Tag Archives: ice

Researchers finally explain the ‘Zen Stone’ phenomenon, and how it could affect space explorers

Researchers at the French National Research Center (CNRS) and l’Université Claude Bernard Lyon 11 are digging into the secrets of the ‘Zen stone’ phenomenon.

a laboratory reproduction of the Zen stone phenomenon in a lyophilizer (freeze-drier).
Image credits Nicolas Taberlet, Nicolas Plihon, (2021), PNAS.

It’s not a rare sight to see stones seemingly placed on a pedestal of ice on the surface of frozen lakes. Contrary to all appearances, this is a naturally-occurring phenomenon, referred to as “Zen stones” for its similarities with the Japanese style of garden decoration, or “Baikal Zen”, after the famous Siberian lake.

Although we had theories regarding their formation, ranging from ‘magic’ to ‘wind erosion, we never actually knew for sure why this happened. The study, now, reports that it comes down to sublimation — the process of a solid becoming a gas without turning into a liquid in-between.

Naturally zen

“There’s no direct application to our work. Just the satisfaction of having understood something new,” Dr. Nicholas Taberlet, a physicist at the University of Lyon and first author of the study, told ZME Science in an email. “However our results can be useful for space exploration missions. For example, NASA is planning to send a lander to Europa, which is covered in ice. It’s important to realize that the rover will prevent the ice from sublimating underneath it and to plan the mission accordingly.”

Lake Baikal, in Siberia, is particularly associated with this phenomenon. As the world’s largest, deepest, and perhaps cleanest freshwater lake, as well as one in a very frigid expanse of the globe, conditions here are ripe for ice pedestals to form. The first requirement for this phenomenon is for a stone to become lodged in ice. This isn’t a rare occurrence in places such as Baikal, whose surface is frozen solid for a long period each year (around 5 mo/year). That being said, however, it is a very rare phenomenon on a global scale, which is why ice pedestals are so strongly associated with this lake.

According to the findings, the physical processes that govern this phenomenon can act pretty much anywhere — even, as Dr. Taberlet mentioned, in outer space. All it takes is the right environmental conditions. Ice pedestal formation is relatively rare on the global scale because it requires “thick, flat, snow-free layers of ice” which form only under “longstanding cold and dry weather conditions”. There simply aren’t many places on Earth that satisfy those conditions.

The team explains that the formation of an ice pedestal starts with a stone that initially “rests directly on a flat ice surface”. Over time, however, this ice is gradually eroded to create the final, slender shape. The exact mechanism which protects the ice under the stone, thus forming the pedestal, remained unknown. The goal of this paper was to determine what this mechanism is.

Up to now, our best guess as to what was happening was the direct melting of the ice beneath the stone. But it didn’t really fit in with what we were seeing in the field. Liquid water promotes the melting of ice around it. Since liquids pool, a small puddle forming underneath the stones would not be able to create a pedestal-like shape — it would melt all the ice at the same rate, creating a roughly uniform, concave shape. Furthermore, it didn’t really make sense for ice underneath the stones to melt faster than the rest, since the stone itself should be blocking sunlight, essentially acting as an umbrella providing shade around it. An argument could be made that the stone warmed up under sunlight, which would promote melting, but that would also melt the pedestal, not create the wavy patterns seen in the field.

The main breakthrough in the study came when the team realized that “the ice was indeed sublimating (and not melting)” and that this effect was caused directly by the shade cast by the stone.

Sublimation is the process through which a solid turns directly into a gas, without turning into a liquid in between. Naphthalene (mothballs) are a very good example of sublimation at work. Dry ice and car air fresheners also rely on sublimation.

Through a series of lab experiments and mathematical modeling, the team showed that the stones do indeed act as umbrellas, preventing sunlight from reaching the ice beneath them. At the same time, however, due to the movements of the Sun in the sky and light scattering in the atmosphere, they only provide complete and permanent shade to a small area in the middle — this will become the pedestal.

A very interesting finding is that, although the stones do block infrared energy (i.e. heat) in sunlight from reaching the ice, they are also what causes the dips around them to form. As these stones heat up, they emit infrared radiation in turn (this is known as black-body radiation). In the area around the stone, ice is heated up by infrared waves from the sunlight and the stones at the same time — causing it to melt even faster than exposed ice. But the radiation emitted by the stone isn’t particularly powerful, and not enough to melt through the ice of the pedestal by itself.

Tied into the unique combination of environmental conditions at the site (sustained, very low temperature and humidity levels), which promote sublimation of ice instead of melting, these interactions lead to the creation of the wavy patterns and ice pedestal beneath the stones of the Baikal lake.

The team used both stones and disks of a variety of dimensions and materials (to account for a larger range of physical properties), finding that the ice pedestals form largely independently of these properties.

While the conditions necessary for this process to take place are quite rare on Earth, they would be very, very common on planets lacking an atmosphere, or those with atmospheres that are very dry. As Dr. Taberlet noted, understanding how a rover might promote the sublimation of ice beneath it could prevent some embarrassing — and very dire — situations for our future explorers.

The paper “Sublimation-driven morphogenesis of Zen stones on ice surfaces” has been published in the journal PNAS.

Global ice loss rate increased by over 65% in the last two decades

New research reports that the planet is losing ice at an ever-faster rate. This is the first time satellite data has been used to survey global ice loss rates, according to the authors, finding that it has increased by over 50% in the last three decades, and 65% over the last two decades.

Furthermore, the authors explain that our planet has lost around 28 trillion tons of ice between 1994 and 2017, which they say is roughly the same quantity in an ice sheet the size of the UK and 100 meters thick — and the rate of melt is increasing. If left unchecked, this will lead to massive damage as communities and natural habitats on today’s coasts will flood.

No-more-ice Age

“Although every region we studied lost ice, losses from the Antarctic and Greenland ice sheets have accelerated the most. The ice sheets are now following the worst-case climate warming scenarios set out by the Intergovernmental Panel on Climate Change,” says lead author Dr. Thomas Slater, a Research Fellow at Leeds’ Centre for Polar Observation and Modelling.

“Sea-level rise on this scale will have very serious impacts on coastal communities this century.”

Led by members from the University of Leeds, the team reports that there has been a 65 % increase in the rate of melt over the 23 years it investigated, driven mainly by losses in Antarctica and Greenland. In raw numbers, we went from 0.8 trillion tons of ice melting per year in the 1990s to 1.3 trillion tons per year by 2017.

Although we had a better idea than ever before about how individual elements in the Earth’s ice system fared, we were still lacking data on how the planet as a whole was evolving. This study, says Dr. Slater, is the first to examine all of the ice at the same time, using satellite data. It includes 215,000 mountain glaciers, the ice sheets of Greenland and Antarctica, ice shelves around Antarctica, as well as sea ice bobbing along the Arctic and Southern Oceans.

The faster rates of melt are being caused by warmer waters and bodies of air — the atmosphere and oceans have warmed by 0.26°C and 0.12°C per decade since the 1980, respectively. Atmospheric melting was the prime offender (responsible for around 68% of the extra melting), with the remainder (32%) coming down to oceanic melting. The geographic distribution of ice on the planet explains the higher rates of atmospheric melting (not all ice comes in contact with the ocean).

All the elements investigated in the study lost ice, but the largest losses were in Arctic Sea ice (7.6 trillion tons) and Antarctic ice shelves (6.5 trillion tons). Mountain glaciers lost a total of 6.1 trillion tons of ice, the Greenland ice sheet lost 3.8 trillion tons, while the Antarctic ice sheet lost some 2.5 trillion tons of ice.

This contributed around 35 millimeters of global sea level rise. The team explains that every centimeter of sea level rise puts an estimated one million people at risk of being displaced by water.

“Sea ice loss doesn’t contribute directly to sea level rise but it does have an indirect influence. One of the key roles of Arctic sea ice is to reflect solar radiation back into space which helps keep the Arctic cool,” says Dr. Isobel Lawrence, a Research Fellow at Leeds’ Centre for Polar Observation and Modelling.

“As the sea ice shrinks, more solar energy is being absorbed by the oceans and atmosphere, causing the Arctic to warm faster than anywhere else on the planet. Not only is this speeding up sea ice melt, it’s also exacerbating the melting of glaciers and ice sheets which causes sea levels to rise.”

Mountain glaciers contributed around 25% of the sea level rise seen over this period, despite storing only 1% of the world’s ice. Their melting is especially worrying, as mountain glaciers are essential sources of fresh water for communities around the world.

It is estimated that for every centimetre of sea level rise, approximately a million people are in danger of being displaced from low-lying homelands.

The paper “Review article: Earth’s ice imbalance” has been published in the journal The Cryosphere.

Greenland’s ice sheet is poised to melt forever — we have 600 years to stop it

New research suggests that the Greenland Ice Sheet is inching in towards a dangerous threshold: in around 600 years, it will melt enough that the sheet won’t ever recover, no matter what we do, and sea levels remain permanently higher. This scenario assumes that current rates of melt remain constant.

The glaciers and landscape in northeast Greenland, captured in 2014. Here you can see refrozen meltwater ponds from last year’s summer cover with snow that has fallen during the winter months. Image credits Credits: NASA /Michael Studinger.

The team from the National Centre for Atmospheric Science and the University of Reading show that climate change is leading to an irreversible rise in the sea level alongside a declining Greenland ice sheet. Worse yet, this sheet is closing in on a point of no return, past which it will never fully regrow — leaving a permanent mark on the global sea level.

Big Ice, Big Loss

The Greenland ice sheet is roughly three times the size of Texas and stores an important quantity of Earth’s frozen water. Under current melting rates, it contributes around 1mm of sea level rise per year (around one-quarter, 25%, of the total increase). It’s estimated that it lost a total of three-and-a-half trillion tonnes of ice since 2003, even with seasonal growth periods factored in.

Needless to say, that’s a lot of water. Rising seas threaten all coastal areas around the world, and can affect potentially millions of people who live in low-lying areas.

If the current target of the Paris Agreement (keeping global warming from going above 2°C compared to pre-industrial temperatures) is not met, we should expect the sea level to rise by several meters and significant ice loss, the authors note. Both would last for tens of thousands of years, and the worse global warming gets, the more dramatic these shifts would be.

The current paper shows that even if temperatures are brought back under control at a later time, the Greenland ice sheet will never fully regrow after it passes its critical threshold. If that point is passed, the sea level would permanently rise by at least 2 meters (with other sources adding to that figure).

Being so large, the sheet has a significant cooling effect on its local climate. In essence, there’s so much ice in Greenland that it’s making Greenland colder and more icy — not a bad trick. But if the sheet declines, local temperatures would increase, which increases melting rates, and snowfall levels would drop dramatically, which would slow down the formation of ice. The team estimates that if the Greenland ice sheet retreats from the northern part of Greenland, that area would remain permanently ice-free. All in all, we have around 600 years before that threshold is passed, the team estimates based on data from the Fifth Assessment Report of the Intergovernmental Panel on Climate Change.

The team simulated the effects of the Greenland ice sheet melting under a range of scenarios, from minimal warming to worst-case conditions. All scenarios led to a decline in size of the sheet and contributed to rising sea levels to one extent or another.

So what’s to be done? Well we need to stop and then reverse climate warming before that threshold is reached.

“Our experiments underline the importance of mitigating global temperature rise. To avoid partially irreversible loss of the ice sheet, climate change must be reversed — not just stabilised — before we reach the critical point where the ice sheet has declined too far,” says Professor Jonathan Gregory, climate scientist from the National Centre for Atmospheric Science and University of Reading, a co-author of the paper.

There were some scenarios the team found where the ice sheet could be stabilized before reaching its point of no return. All of them, however, hinged on steps being taken ahead of time to reverse global warming.

The paper “Large and irreversible future decline of the Greenland ice sheet” has been published in the journal The Cryosphere.

We should expect long-term ice loss even if we stop climate change today, according to a new study

New research at the Monash University reports that historic ice loss in Antarctica has persisted for several centuries after it first started.

Stock image via Pixabay.

Such findings underscore the inertia of processes affecting ice sheets and suggest that today’s polar ice will continue to shrink for quite a long time even if climate change is avoided.

Long-term melt

“Our study implies that ice loss unfolding in Antarctica today is likely to continue unabated for a long time—even if climate change is brought under control,” said lead study authors Dr. Richard Jones and Dr. Ross Whitmore, from the Monash University School of Earth, Atmosphere and Environment.

The study charts the extent of ice in the Mawson Glacier, which is adjacent to a region of the Ross Sea that saw a rapid retreat of sea ice after the Last Glacial Maximum.

According to the team, this area experienced at least 220 meters of abrupt ice thinning between 7,500 and 4,500 years ago, and more gradual thinning up until a thousand years ago. The same abrupt ice loss has occurred (at similar rates) in other glaciers formed on various bed topographies across multiple regions during the mid-Holocene, they explain. The Holocene is the current geological epoch.

Sea-level and ocean temperature data suggest that warmer oceans were the key drivers of this ice loss. Warmer waters most likely hastened glacier retreat (through ground-line melting, which makes glaciers slip more quickly into the oceans) which led to greater sheet instability and faster melting.

“We show that part of the Antarctic Ice Sheet experienced rapid ice loss in the recent geological past,” said Professor Andrew Mackintosh, head of the Monash School of Earth, Atmosphere, and Environment, and co-author of the paper.

“This ice loss occurred at a rate similar to that being observed in rapidly changing parts of Antarctica today, and it was caused by the same processes that are considered to cause current and probable future Antarctic ice mass loss—ocean warming, amplified by internal feedbacks.”

This retreat continued for several centuries after it first started, the authors note, which gives us cause to believe that the ice loss we’re seeing today will behave similarly. Such findings are particularly troubling in the context of climate change, which is driving glacier ice loss through higher atmospheric and ocean mean temperatures.

The results are supported by previous research which also found that glaciers are beyond the point of no return in regards to ice loss.

The paper “Regional-scale abrupt Mid-Holocene ice sheet thinning in the western Ross Sea, Antarctica” has been published in the journal Geology.

Arctic ice shrinks to second lowest level on record

In another sign of the acceleration of global warming, ice in the Arctic Ocean has melted to its second-lowest level on record this year. The Floes glacier shrunk to 3.74 million square kilometers (1.4 million square miles) last week, according to preliminary data from satellite observation.

Credit Flickr Duncan C.

The only other time such a low level was seen was in 2012 when the ice pack was reduced to 3.41 million square kilometers after a late-season cyclonic storm. Arctic sea ice usually reaches its low point in September, but it’s melting more and more each year as the polar north warms due to climate change.

“It’s been a crazy year up north, with sea ice at a near-record low… heat waves in Siberia, and massive forest fires,” said Mark Serreze, director of the National Snow and Ice Data Center (NSIDC), in a statement. “The year 2020 will stand as an exclamation point on the downward trend in Arctic sea ice extent. We are headed towards a seasonally ice-free Arctic Ocean, and this year is another nail in the coffin.”

This year’s drop in sea ice levels was particularly sharp between August 31 and September 5 due to pulses of warm air from a heatwave in Siberia, according to the NSIDC. The rate of ice loss during those six days was greater than during any other year on record, with temperatures in the Siberian Arctic 8ºC to 10ºC (14 to 18 Fahrenheit) above normal.

Studies have shown the warming of the Arctic and the melting of sea ice is influencing weather further south, altering the jet stream that powers the weather system. As ice disappears, it leaves areas of dark water open, which absorb radiation instead of reflecting it back to the atmosphere. This amplifies global warming and explains why the Arctic is warming faster than the rest of the world.

The reduction on sea ice levels in the Arctic is threatening wildlife, from seals and polar bears to algae, said Tom Foreman, a polar wildlife expert, for Al Jazeera.

“The numbers that we’re getting in terms of the extent of sea ice decrease each year put us pretty much on red alert in terms of the level of worry that we have, our concern for the stability of this environment,” he explains.

A study earlier this month discovered that the Arctic sea ice has melted so much in the last few decades that even a record cold year won’t produce the amount of summer sea ice that existed in the mid-20th century. High air temperatures during autumn and winter will drive the region to a district climate by the middle of this century, they found.

At the same time, Hamburg University scientists found in a study last April that by 2050 the North Pole would be ice-free in some Arctic summers. Every ton of carbon dioxide emitted worldwide led to three square meters of ice melt in the highly sensitive Arctic, said the study’s lead earth scientist Dirk Notz.

Countries agreed to limit global temperature rises to “well below” 2ºC (3.6 degrees Fahrenheit) through the Paris Agreement signed in 2015. But greenhouse gas emissions are still going up, with more ambitious climate action needed. The drops in emissions from the pandemic haven’t had a significant effect on climate change, and lockdowns are being lifted around the world.

Greenland is losing ice seven times faster than in the 1990s

Greenland’s rate of ice loss is increasing faster than expected, a new metastudy reports.

The increased influx of water from Greenland’s ice sheet puts us on track for sea-level rise consistent with the Intergovernmental Panel on Climate Change’s (IPCC) high-end climate warming scenario. Projections for this scenario estimate that coastal flooding will displace 400 million people by 2100.

Image credits Jean-Christophe Andre.

The study is a collaboration between 96 polar scientists from 50 international organizations — The Ice Sheet Mass Balance Inter-comparison Exercise (IMBIE) team — and takes the most complete look at Greenland’s long-term ice loss to date. It combined 26 separate surveys to track changes in the ice mass of Greenland between 1992 and 2018. Data from 11 different satellite missions was used to measure the ice sheet’s changing volume, flow, and mass.

Melting quick

“On current trends, Greenland ice melting will cause 100 million people to be flooded each year [by 2100], so 400 million in total due to all sea level rise,” says Professor Andrew Shepherd at the University of Leeds, one of the study’s co-lead authors.

Melt rate in Greenland has risen from 33 billion tons, on average, per year in the 1990s to 254 billion tons per year over the last decade. In total, the island lost roughly 3.8 trillion tons of ice since 1992.

The IPCC mid-warming scenario set out in 2013 estimated 60 centimeters of sea-level rise by 2100, with associated coastal flooding displacing an estimated 360 million people. The rates of melt reported on in this study push those estimates by an additional 5 to 12 cm — consistent with the projection for the high-warming climate scenario.

“As a rule of thumb, for every centimeter rise in global sea level another six million people are exposed to coastal flooding around the planet,” Professor Shepherd explains.

The report shows that half of the ice losses recorded between 1992 and today have been caused by higher average temperatures, which promoted surface melting. The rest, around 48% of the total ice mass lost, was caused by increased glacier flow into the ocean due to warmer waters. Melting peaked 335 billion tonnes per year in 2011 but has since decreased to 238 billion tonnes per year “as atmospheric circulation favored cooler conditions”.

https://www.youtube.com/watch?v=HlApT0-2LT4

The team notes that this lower rate is still seven times higher than that in the 1990s, and that the dataset didn’t include all of 2019. Higher rates of melt expected in the summer could push Greenland to see record quantities of ice loss.

“Satellite observations of polar ice are essential for monitoring and predicting how climate change could affect ice losses and sea level rise” said Erik Ivins at NASA’s Jet Propulsion Laboratory in California, and co-lead author of the study.

Researchers from the European Space Agency (ESA) and the US National Aeronautics and Space Administration (NASA) also took part in the IMBIE report.

The paper “Mass balance of the Greenland Ice Sheet from 1992 to 2018” has been published in the journal Nature.

NASA maps ice water reserves inches below Martian surface

If humans will ever colonize Mars, they’ll need to find a fairly accessible source of water. A new map of the Martian surface showing where water ice is believed to be located suggests this won’t be that challenging. In some places, the ice is located as little as 2.5 centimeters below the surface, just one shovel away.

The annotated area has near-surface water ice that could be easily accessible by astronauts traveling to Mars. Credit: NASA/JPL.

Space missions are frugal by nature since every pound of cargo can cost tens of thousands of dollars to launch — and that’s for shipments to the International Space Station. A manned trip to Mars would be even tighter with resource utilization. This is why any human-crewed mission to Mars would have to involve some on-site resources, such as harvesting ice for drinking water and making rocket fuel.

Using data from the Mars Reconnaissance Orbiter (MRO) and Mars Odyssey orbiter — two spacecraft that are constantly monitoring the Red Planet‘s surface — NASA has compiled a map of relatively accessible ice which could potentially be reached by astronauts on Mars.

Colored map showing underground water ice on Mars. Cool colors represent ice closer to the surface than zones with warm colors; black represents very little to water. Credit: NASA/JPL.

In order to detect ice from afar, the researchers relied on heat-sensing instruments aboard the spacecraft. Underground ice changes the temperature of the Martian surface, so by measuring surface temperature and cross-referencing with data, such as known ice reservoirs detected by radar or seen after meteor impacts, it is possible to map out water ice deposits.

“You wouldn’t need a backhoe to dig up this ice. You could use a shovel,” said the paper’s lead author, Sylvain Piqueux of NASA’s Jet Propulsion Laboratory in Pasadena, California. “We’re continuing to collect data on buried ice on Mars, zeroing in on the best places for astronauts to land.”

Due to Mars’ thin atmosphere, liquid water can’t last on the surface of the planet (although sometimes briny water can flow temporarily). But there are important water reserves locked as ice in the underground throughout the planet’s mid-latitudes. For instance, a large portion of Arcadia Planitia, located in the northern hemisphere, shows a large quantity of water ice trapped less than 30 centimeters below the surface. As such, this area could be considered prime real estate for landing astronauts.

In the future, NASA will continue to study subsurface water ice, looking to study how buried ice deposits change across different seasons.

“The more we look for near-surface ice, the more we find,” said MRO Deputy Project Scientist Leslie Tamppari of JPL. “Observing Mars with multiple spacecraft over the course of years continues to provide us with new ways of discovering this ice.”

Stop climate change or the Emperor penguins die, a new paper warns

Unless we get a grip on climate heating, the emperor penguin is going the way of the dodo — extinct.

Image credits Christopher Michel / Flickr.

An international study led by researchers at the Woods Hole Oceanographic Institution (WHOI) reports that warming climate conditions might cause emperor penguins (Aptenodytes forsteri) to become extinct by the end of the century.

The Emperor’s new environment

“If global climate keeps warming at the current rate, we expect emperor penguins in Antarctica to experience an 86% decline by the year 2100,” says Stephanie Jenouvrier, a seabird ecologist at WHOI and lead author on the paper.

“At that point, it is very unlikely for them to bounce back.”

Emperor penguins live and die by sea ice, which is where they breed and molt. The animals build their colonies on spans of ice that satisfy very specific conditions: it must be locked to the Antarctic shoreline but close to open seawater (giving the birds access to food). Climate heating is melting sea ice, however, which effectively destroys the birds’ habitat, food access, and ability to reproduce.

For their study, the team combined a global climate model (created by the National Center for Atmospheric Research, NCAR) and a model of the penguin populations themselves. The first gave the team a rough idea of how sea ice will evolve in the future, especially in terms of where and when it will form or melt in the future. The second one worked to predict how colonies might react to the changes in their environment.

“We’ve been developing that penguin model for 10 years,” says Jenouvrier. “It can give a very detailed account of how sea ice affects the life cycle of emperor penguins, their reproduction, and their mortality. When we feed the results of the NCAR climate model into it, we can start to see how different global temperature targets may affect the emperor penguin population as a whole.”

The compound model was then used to examine three different scenarios. The first assumes an increase in global average temperatures of only 1.5 degrees Celsius (the goal set out by the Paris climate accord). The second involves a temperature increase of 2 degrees Celsius. The final scenario assumes no action was taken against climate change, leading to temperature increases of 5 to 6 degrees Celsius.

The first one led to a loss of around 5% of sea ice by 2100, causing a roughly 20% drop in the penguin population. The 2-degree warming scenario led to around 15% ice loss and a 30% drop in penguin numbers. The business as usual scenario was by far the most damaging, leading to almost complete loss of the penguin colonies.

“Under that scenario, the penguins will effectively be marching towards extinction over the next century,” she says.

The paper “The Paris Agreement objectives will likely halt future declines of emperor penguins” has been published in the journal Global Change Biology.

Greenland set to accelerate sea level change in the near future

Greenland’s contribution to sea-level rise is increasing, as climate change makes the region release meltwater into the ocean.

Image via Pixabay.

Greenland’s ice sheet is experiencing an increase in ice slab thickness at its interior regions. These ice sheets are normally porous, allowing meltwater to percolate (drain through) them, but the extra thickness makes them impermeable — so all the meltwater is draining into the ocean.

The process could see the country’s contribution to sea level rise increase by as much as 2.9 inches by 2100.

Thicc ice

“Even under moderate climate projections, ice slabs could double the size of the runoff zone by 2100,” said Mike MacFerrin, a CIRES (Cooperative Institute for Research In Environmental Sciences) and University of Colorado Boulder researcher who led the new study. “Under higher emissions scenarios, the runoff zone nearly triples in size.”

Runoff from ice slabs only amounts to a one-millimeter increase in global sea levels so far, the team explains, but that contribution will expand substantially under climate warming.

In the year 2000, Greenland’s runoff zone — the region of the ice sheet where runoff contributes to sea level rise — was roughly equivalent to the size of New Mexico. Between 2001 and 2013, it expanded by an average of two American football fields per minute, reaching roughly 65,000 sq km.

Even under a moderate emissions scenario, the team adds, it could reach the size of Colorado by 2100. That would raise sea levels by an extra 7-33 mm (one-quarter to one inch) by the same timeframe. Under a high emissions scenario, the situation looks even bleaker: the runoff zone could increase by the size of Texas, according to the new paper, contributing an extra 17-74 mm (half-inch to nearly three inches) of sea-level rise.

The runoff estimates from ice slabs are in addition to other sources of sea-level rise from Greenland, such as calving icebergs.

The team explains that Greenland’s ice sheets are made of layers with different textures. Fresh snow that falls each winter either melts into surface lakes or builds-up and helps compact older snow into glacial ice. Snow that partially melts over summer later re-freezes into thin ice “lenses” between 2 to 5 mm (one or two inches) thick within the compacted snow.

Normally, meltwater can percolate through and around ice lenses, refreezing in place without running off to sea. As mean temperatures over the Arctic increase and melting events become more frequent and extreme, however, these ice lenses solidify into slabs between 1 and 16-meter (3- to 50-foot) thick. These slabs block water from flowing through, which ends up flowing downhill into the ocean.

Climate warming is also increasing the quantity of meltwater in Greenland. In July of 2012, snow and ice melted from 97% of Greenland’s ice sheet surface, which the team says has never before been seen the 33-year-long satellite record. This spring, which was particularly warm and sunny in Greenland, resulted in a record-setting 80 billion tons of Greenland ice melted.

“As the climate continues to warm, these ice slabs will continue to grow and enhance other meltwater feedbacks,” said Mahsa Moussavi, a coauthor on the paper. “It’s a snowball effect: more melting creates more ice slabs, which create more melting, which creates again more ice slabs.”

All in all, this process will fundamentally alter the ice sheet’s equilibrium. The team warns that we need to understand Arctic feedbacks like this one because they show just how much, and how quickly, a warming climate can change Earth’s most vulnerable regions.

“Humans have a choice about which way this goes,” MacFerrin said.

The paper “Rapid expansion of Greenland’s low-permeability ice slabs” has been published in the journal Nature.

The different types of planets barreling through space

Planets come in all sha… planets come in various sizes. But, some of the most striking characteristics that set them apart are their physical and chemical particularities, which we use to categorize the myriad of planets we’ve found in space.

Image via JPL-Caltech.

I like planets. I like them so much I live on one. They’re heavy enough for gravity to make them round, their orbits are clear of debris, and they don’t burn like stars do. But, there’s a lot of variation in what they are and the experience they offer.

So, today, I’d thought it would be exciting to look at all the different types of planets — some of which we’ve seen in the great expanse of space, some of which we’re only expecting to find. In no particular order, they are:

Brown Dwarfs

Artist’s impression of a T-type brown dwarf named 2MASSJ22282889-431026. The Hubble and Spitzer space telescopes observed the object to learn more about its turbulent atmosphere.
Image credits NASA / JPL-Caltech.

A star is a delicate system where gravity compresses and heats everything up while the nuclear fusion at their core pushes outwards. With too much pressure, electrons can’t move freely, so the reaction stops. With too much ‘boom’, there’s not enough pressure to keep the reaction going.

Teetering on the edge of starhood, brown dwarfs have outgrown any definition of a ‘planet’. Yet, they’re just not quite a star. Ranging from 13 to 80 times the mass of Jupiter, brown dwarfs are immense embers barreling through space, fusing deuterium and lithium to keep themselves slightly alight. However, they need yet more matter to be able to fight their own gravity, so they can’t ignite.

Brown dwarfs aren’t planets. They don’t form like planets — they form like stars. Instead of material slowly clumping together, brown dwarfs are born from clouds of gas collapsing in on themselves.

Gas Giants

Jupiter as snapped by the Juno probe.
Image credits NASA / JPL-Caltech.

The chonk de la chonk, gas giants are the largest planets to ever dot the universe. They are composed primarily (>90%) of hydrogen and helium (the two simplest elements in the periodic table) with traces of other compounds thrown in for good measure. Hydrogen and helium give these planets an overall brown-yellow-ocher palette, with water and ammonia clouds peppering their highest layers white. Owing to the nature of their bodies, these giants are blanketed by wild storms and furious winds.

We don’t know much about their cores, only that it has to be immensely hot (around 20,000 Kelvin, K) and pressurized in there. The main hypotheses hold that gas giants either have molten rocky cores surrounded by roiling oceans of gas, diamond cores, or ones made of super-pressured (metallic) hydrogen nuggets.

Jupiter as snapped by the Juno probe.
Image credits NASA / JPL-Caltech.

They are sometimes called ‘failed stars’ because hydrogen and helium keep stars running, but gas giants don’t have enough mass to spark nuclear fusion. We have two of them in the solar system, Jupiter and Saturn.

Most exoplanets we’ve found so far are gas giants — just because they’re huge and easier to spot.

Ice Giants

Picture of Neptune taken in August 1989, assembled using filtered images taken by Voyager 2.
Image credits NASA / JPL-Caltech / Kevin M. Gill.

Very similar to gas giants but won’t return your texts. Ice giants are believed to swap out hydrogen and helium (under 10% by weight) in favor of oxygen, carbon, nitrogen, and sulfur, which are heavier. Boiled down, we don’t really know what elements these planets are made of — their (admittedly thin) hydrogen envelopes hide the interior of the planets, so we can’t just go and check. This outer layer is believed to closely resemble the nature of gas giants.

Still, it is believed that, while not entirely made of the ice we know and love here on Earth exactly, there is water and water ice in their make-up. They get their name from the fact that most of their constituent matter was solid as the planets were forming, and because planetary scientists refer to elements with freezing points above about 100 K (such as water, ammonia, or methane) as “ices”.

COROT-7c, an exoplanet located approximately 489 light years away in the constellation Monoceros. Seen here in an artistic simulation as a hot mini-Neptune.
Image credits MarioProtIV / Wikimedia.

Ice giants are, as per their name, quite gigantic, but they tend to be smaller than gas giants. However, owing to their much-denser make-up, they are also more massive overall. There are two ice giants in our solar system, Uranus and Neptune. Water, in the form of a supercritical ocean beneath their clouds, is believed to account for roughly two-thirds of their total mass.

Both ice giants and gas giants have primary atmospheres. The gas they’re made from was accreted (captured) as the planets were forming.

Rocky Planets

Artist’s concept of NASA’s Mars Science Laboratory spacecraft approaching Mars.
Image credits NASA / JPL-Caltech.

Also known as terrestrial or telluric planets (from the Latin word for Earth), they are formed primarily of rock and metal. Their main feature is that they have a solid surface. Mercury, Venus, Earth, and Mars, the first four from the Sun, are the rocky planets of our solar system.

To the best of our knowledge rocky planets are formed around a metallic core, although the hypothesis of coreless planets has been floated around.

Atmospheres, if they have one, are secondary — formed from captured comets or created via volcanic or biological activity. Rocky planets also form primary atmospheres but fail to retain them. Secondary atmospheres are much thinner and more pleasant than those of Saturn or Uranus. That’s not to say a secondary atmosphere can’t influence its planet: Venus’s rampant climate disaster is a great example.

Composite image of Mercury’s north pole.
Image credits NASA.

Mercury, with a metallic core of 60–70% of its planetary mass, is as close as we’ve found to an Iron planet. Both those and the much more bling Carbon planets thus remain hypothetical. Another exciting and cool-named hypothetical class of rocky planets are Chthonians, the rock or metal cores of gas giants stripped bare.

Rocky worlds can harbor liquid water, terrain features, and potentially tectonic activity. Tectonically-active planets can also generate a magnetic field.

Comparison of best-fit size of the exoplanet Kepler-10c (middle) with Earth (Left) and Neptune.
Image via Wikimedia.

Such planets come in many different sizes. Earth is Earth-sized, Mercury is only about one third of it, while Kepler-10c is 2.35 times as large as our planet. Density is also a factor. Without going to a planet and studying its interior structure, it’s impossible to accurately estimate its density. As a rule of thumb, however, uncompressed density estimates for a rocky planet tend to be lower the farther away it orbits its star. It’s likely that planets closer to the star would thus have a higher metal (denser) content, while those further away would have higher silicate (lighter) content. Gliese 876 d is 7 to 9 times the mass of Earth.

The first extrasolar rocky planets were discovered in the early 1990s. Ironically, they were found orbiting a pulsar (PSR B1257+12), one of the most violent environments possible for a planet. Their estimated masses were 0.02, 4.3, and 3.9 times that of Earth’s.

Ocean planets

Ganymede, the largest and most massive moon in the Solar System, and its ninth largest body.
Its also an ocean moon.
Image via Wikimedia.

These planets contain a large amount of water, either on the surface or subsurface. They’re an offshoot of the rocky planet, either covered in liquid water or an ice layer over liquid water. We don’t know very much about them or how many there are out there because we can’t yet spot liquid surface water, so we use atmosphere spectrometry as a proxy.

Earth is the only planet on which we’ve confirmed the existence of liquid water at the surface so far. And although water does cover around 71% of the Earth, it only makes up for 0.05% of its mass, so we’re not an Ocean planet. On these latter ones, waters are expected to run so deep that they would turn to (warm) ice even at high temperatures (due to the pressure).

This type of planet remains one of the likeliest to harbor extraterrestrial life.

Dwarf planets

True color image of Pluto taken by the  New Horizons craft.
Image via Wikimedia.

Fan-favorite Pluto, along with Ceres, Haumea, Makemake, and Eris are the dwarf planets of our solar system. Dwarf planets kind of stride the line between planets and natural satellites. They’re large enough to hold their own stable shape, even to hold moons themselves, but not enough to clear their orbit of other material.

Moons

Titan seen in visible light (center) and infrared (exterior).
Image credits NASA / JPL-Caltech / University of Nantes / University of Arizona.

Not technically planets because they orbit another planet, moons are nevertheless telluric bodies that vary in size from ‘large asteroid’ to ‘larger than Mercury’. Titan, Saturn’s largest moon, has its own atmosphere.

There are six planets in the Solar System that sum up to 185 known natural satellites, while Pluto, Haumea, Makemake, and Eris also harbor their own moons.

Rogue planets

These are the planets your parents warned you about.

Rogue planets deserve a mention on this list despite the fact that they don’t orbit a star. They are, for all intents and purposes, planets that orbit the galactic core after being ejected from the planetary system in which they formed. It is also possible that, somehow, they formed free of any stellar host. PSO J318.5−22 is one such planet.

Glacier.

Antarctic instability could raise sea levels by half a meter in 150 years

We’re seriously underestimating Antarctica’s ability to push global sea level rise, a new study reports.

Glacier.

Image credits Luis Valiente.

Ice masses in the southern continent are becoming extremely unstable due to climate change, the authors explain, but this isn’t readily apparent. The team behind the study, with members from the Georgia Institute of Technology, NASA Jet Propulsion Laboratory, and the University of Washington, says that this hidden instability will likely accelerate water flow into the ocean and raise sea levels much faster than previously estimated.

Thawing the Antarctic

Five Antarctic glaciers have doubled their rate of ice loss over the last six years, according to the study, with at least one (the Thwaites Glacier) being in danger of collapse. While we can’t accurately estimate exactly how glacier runoff will evolve over the coming 50 to 800 years yet (this is dependant bot on our choices and on unknown factors such as topography), the team have done their best to cover all possible outcomes. For this, they’ve run 500 ice flow simulations for Thwaites’ evolution. While there was a wide range of variation between the scenarios, they all ended in the eventual collapse of Thwaites.

Glacier collapse has a lot to do with the geometry of the bedrock underpinning the ice. Glaciers whose leading edge ‘hangs’ in the ocean instead of being supported by bedrock are called tidewater glaciers. The point at which they glaciers start to float is the grounding line. Glacier instability/collapse first starts here.

Glacier shelf interaction.

Image credits Ted Scambos, Michon Scott / National Snow and Ice Data Center.

Warmer temperatures also heat up the ocean water, which starts eating away at the bottom of the glacier (which raises sea levels). This process also accelerates the rate at which glaciers fragment and float out into the sea. This is perhaps the most worrying process from a sea-level perspective: these bits of ice eventually melt in the wider ocean, but the process also speeds up the rate at which glaciers slide into the waters (as they’re no longer buoyed up by the ocean), leading to more and more melting.

“Once ice is past the grounding line and just over water, it’s contributing to sea level because buoyancy is holding it up more than it was,” says Alex Robel, an assistant professor in Georgia Tech’s School of Earth and Atmospheric Sciences and the study’s lead author. “Ice flows out into the floating ice shelf and melts or breaks off as icebergs.”

The simulations show that even if we do stop climate warming in the future, instability in Thwaites will keep feeding water into the global ocean at extremely fast rates compared to the baseline value. These results are based on present-day ice melt rates, meaning that higher rates of global warming will lead to faster and stronger melt rates than identified in this paper.

Worst of all, if Thwaites does collapse, it will trigger a feedback loop leading to more and more melt as it slides into the ocean at faster rates.

“If you trigger this instability, you don’t need to continue to force the ice sheet by cranking up temperatures. It will keep going by itself, and that’s the worry,” said Robel.  “Climate variations will still be important after that tipping point because they will determine how fast the ice will move.”

“After reaching the tipping point, Thwaites Glacier could lose all of its ice in a period of 150 years. That would make for a sea level rise of about half a meter (1.64 feet),” adds NASA JPL scientist Helene Seroussi, a co-author of the paper. “The process becomes self-perpetuating”.

Currently, sea levels are 20 cm (almost 8 inches) above pre-industrial levels. Sea ice doesn’t raise sea levels as it melts — all that ice is already in the water so it already contributes a volume to the global ocean — but land-borne glaciers do. Antarctica holds the most land-supported ice, so it can have a very sizeable contribution to sea levels.

“There’s almost eight times as much ice in the Antarctic ice sheet as there is in the Greenland ice sheet and 50 times as much as in all the mountain glaciers in the world,” Robel explains.

It’s not yet clear whether Thwaites has reached the tipping point or not, but its outer edge is sinking into the ocean faster than previously recorded. The findings are particularly worrying as the success of current efforts to proof cities and installations against sea level rise are wholly dependent on having accurate predictions. However, the current study shows that our current forecasts aren’t very reliable.

“You want to engineer critical infrastructure to be resistant against the upper bound of potential sea level scenarios a hundred years from now,” Robel said. “It can mean building your water treatment plants and nuclear reactors for the absolute worst-case scenario, which could be two or three feet of sea level rise from Thwaites Glacier alone, so it’s a huge difference.”

Another surprising finding made by the team is that when climate conditions fluctuate strongly, Antarctic ice evens out the effects. Ice flow in such conditions will increase gradually, not wildly, but the instability produced the opposite effect in the simulations.

“The system didn’t damp out the fluctuations, it actually amplified them. It increased the chances of rapid ice loss,” Robel said.

“[Almost total ice loss in Thwaites] could happen in the next 200 to 600 years. It depends on the bedrock topography under the ice, and we don’t know it in great detail yet,” Seroussi said.

The paper “Marine ice sheet instability amplifies and skews uncertainty in projections of future sea-level rise” has been published in the journal Proceedings of the National Academy of Sciences.

Iceland.

Our emissions could melt all the ice in Greenland by the year 3000 — and raise sea levels by 24 ft

Greenland may actually be green by the end of the millennium if greenhouse emissions continue unabated.

Iceland.

Image credits Marcel Prueske.

New research shows that, if greenhouse gas emissions continue on their current trajectory, Greenland could lose 4.5% of its ice by the end of the century, and all of it by the year 3000. That 4.5% loss of ice is equivalent to roughly 13 inches of sea level rise, the team explains.

Actually Green land

“How Greenland will look in the future — in a couple of hundred years or in 1,000 years — whether there will be Greenland, or at least a Greenland similar to today, it’s up to us,” said first author Andy Aschwanden, a research associate professor at the University of Alaska Fairbanks Geophysical Institute.

Greenland houses a lot of ice — around 660,000 square miles of solid ice sheet, which contains around 8% of all the planet’s fresh water. Between 1991 and 2015, melting here has added about 0.02 inches per year to the sea level. Needless to say, we need to know how all that ice is faring and whether there’s any cause for concern. Turns out that there is.

The team used recent topography (landscape) data of Greenland’s terrain today to model how its ice sheets will evolve in the future. This data was recorded by a NASA airborne science campaign (Operation IceBridge) during which aircraft fitted with a full suite of scientific instruments scanned Greenland’s ice sheets recording its surface, the individual layers within, and the shape of the bedrock. On average, Greenland’s ice sheet is 1.6 miles thick, but there was a lot of variation.

A wide range of scenarios concerning ice loss and changes in sea level are possible based on how greenhouse gas concentrations and atmospheric conditions evolve. The team ran 500 simulations for each emission scenario using the Parallel Ice Sheet Model, developed at the Geophysical Institute, to create a picture of how Greenland’s ice would respond to different climate conditions. The model included parameters on ocean and atmospheric conditions as well as ice geometry, flow, and thickness.

Under a business as usual scenario, we could see around 24 feet to global sea level rise by the year 3000 due to melting in Greenland alone — which would put much of San Francisco, Los Angeles, New Orleans and other cities under water. However, if we do manage to slash greenhouse gas emissions significantly, the prospects improve. Reduced emission scenarios showed between 8% to 25% melting of Greenland’s ice, which would lead to approximately 6.5 feet of sea level rise

Projections for both the end of the century and 2200 tell a similar story. A wide range of outcomes are possible, including saving the ice sheet, but it all depends on emission levels, the team explains.

The team explains that modeling ice sheet behavior is tricky because ice loss is primarily driven by the retreat of outlet glaciers. These are the glaciers at the margin of the ice sheets, and they ‘drain’ ice from deeper in the sheets through through-like structures in the bedrock. This study was the first to include these outlet glaciers in its modeling and found that their discharge could contribute as much as 45% of the total mass of ice loss in Greenland by 2200. Outlet glaciers come into contact with water, the team explains, which makes ice melt much faster than air. The more ice that comes into contact with water, the faster the rate of melting — which creates a feedback loop that dramatically affects the ice sheet’s stability.

Previous research lacked data as comprehensive as that recorded by IceBridge, so it couldn’t simulate the ice sheets’ evolution in such detail.

“Ice is in very remote locations,” says Mark Fahnestock, a researcher at the University of Alaska Fairbanks Geophysical Institute and paper co-author. “You can go there and make localized measurements. But the view from space and the view from airborne campaigns, like IceBridge, has just fundamentally transformed our ability to make a model to mimic those changes.”

“What we know from the last two decades of just watching Greenland is not because we were geniuses and figured it out, but because we just saw it happen,” he adds. As for what we will see in the future, “it depends on what we are going to do next.”

The paper “Contribution of the Greenland Ice Sheet to sea level over the next millennium” has been published in the journal Science Advances.

Iceberg.

Arctic ecosystems “highly responsive” to climate change — and very hard to fix once broken

Climate change is impacting the Arctic far quicker than we’ve assumed, an international team of researchers reports. Other research looking into how Arctic life fared after the meteorite impact that wiped out the dinosaurs gives us a glimpse into how ecosystems in the area might evolve under climate change.

Iceberg.

Image credits Rolf Johansson.

Ecosystems in the Arctic undergo rapid, dramatic, and long-lasting changes in response to climate shifts — even those of average magnitude, according to a new study published in Environmental Research Letters. The study, conducted by an international research team led by members from the University of Maine, finds a “surprisingly tight coupling” between climate shifts and environmental responses in the Arctic. The paper thus overturns previous assumptions that environmental responses are delayed or dampened by internal ecosystem dynamics, allowing only significant climate shifts to have an effect on local ecosystems.

The heat is on

“Our analyses reveal rapid environmental responses to nonlinear climate shifts, underscoring the highly responsive nature of Arctic ecosystems to abrupt transitions,” the study’s abstract reads.

After 1994, mean air temperatures over West Greenland (as recorded in June) were 2.2°C higher than baseline, the team reports, and have increased by an additional 1.1°C since 2006. Mean winter precipitation also doubled in quantity (from 20mm to 40mm) over the area after 1994.

The findings come from over 40 years’ worth of weather data and paleoecological reconstructions. The team explains that these “abrupt climate shifts” were accompanied by “nearly synchronous” environmental responses in the area, including increased ice sheet discharge and dust, and advanced plant phenology (i.e. earlier onset of the life cycles of plants in the area). Lakes in the area experienced earlier ice-outs and greater diversity of algae.

In light of these findings, the team cautions that Arctic ecosystems are much more responsive to abrupt transitions — even moderate magnitude ones — than assumed. The strength of climate forcing (i.e. warming) in the area has also been underestimated, they add. Understanding how these ecosystems respond to abrupt climate change is key to predicting their evolution in the future and managing potentially damaging shifts says Jasmine Saros, the paper’s lead author.

“We present evidence that climate shifts of even moderate magnitude can rapidly force strong, pervasive environmental changes across a high-latitude system,” she says.

“Prior research on ecological response to abrupt climate change suggested delayed or dampened ecosystem responses. In the Arctic, however, we found that nonlinear environmental responses occurred with or shortly after documented climate shifts in 1994 and 2006.”

How does this pan out?

Penguins.

Penguins don’t live in the Arctic but they’re cute, so here’s a picture of some.
Image credits Siggy Nowak.

Another unrelated study published in the journal Palaeontology looked at how life on the other end of the planet — Antarctica — recovered after the impact of Chicxulub, the dinosaur-killing meteorite. This impact triggered a massive, planet-wide extinction event known as the Cretaceous-Paleogene (K-Pg) mass extinction some 66 million years ago.

Although the effects of this impact (e.g. transient cooling, global darkness, and expansion of anoxic waters) were “probably short-lived, […] biogeochemical cycling and ecosystem function remained disturbed for an extended period”. It took local marine ecosystems roughly one million years to return to pre-extinction levels, they explain.

The K-Pg event was caused by the impact of a 10 km asteroid on the Yucatán Peninsula, Mexico, and took place while our planet was already in the throes of environmental instability caused by a major volcanic episode. In the end, Chicxulub’s visit would wipe out around 60% of the marine species around Antarctica, and 75% of species around the world. This turned out to be quite a fortunate development for us humans, as the impact fundamentally changed the evolutionary history of life on Earth. Most of the animal groups you know today, including us mammals, were only able to rise as a direct consequence of this impact.

“This study gives us further evidence of how rapid environmental change can affect the evolution of life,” says Dr. Rowan Whittle, a palaeontologist at British Antarctic Survey and the study’s lead author.

“Our results show a clear link in the timing of animal recovery and the recovery of Earth systems.”

For over 320,000 years after the extinction, the team reports, the Antarctic sea floor was dominated by burrowing clams and snails. It took roughly one million years for the number of species to recover to pre-extinction levels.

“Our discovery shows the effects of the K-Pg extinction were truly global, and that even Antarctic ecosystems, where animals were adapted to environmental changes at high latitudes like seasonal changes in light and food supply, were affected for hundreds of thousands of years after the extinction event.”

Now, needless to say, the K-Pg extinction event was way more abrupt and dramatic than the shifts we’re causing in the Earth’s climate today. And this study focuses on its effects in Antarctica, not the Arctic. However, it does serve as an adequate case-study to see how long such ecosystems need to recover from major environmental shocks.

And climate change (plus human activity) is a major environmental shock. It’s much slower than an asteroid impact, sure, but it’s still happening unbelievably fast from a geological and evolutionary point of view. The first study we’ve discussed here shows that Arctic ecosystems do feel the heat, and feel it fast. Life here is very specialized to thrive in its frigid niche and if we let these ecosystems collapse, the same ancient dynamics that Whittle’s team found in the Antarctic will likely apply — our Arctic will only recover as the Earth’s systems recover.

The paper “Arctic climate shifts drive rapid ecosystem responses across the West Greenland landscape” has been published in the journal Environmental Research Letters.

The paper “Nature and timing of biotic recovery in Antarctic benthic marine ecosystems following the Cretaceous–Palaeogene mass extinction” has been published in the journal Palaeontology.

Mars.

Some Martian clouds are made of ground-up meteors

Mars has clouds too — but some are formed by falling meteorites, not rain.

Mars.

Rendering of Mars produced using MOLA altimetry data.
Image credits Kevin Gill / Flickr.

Researchers from the University of Colorado at Boulder have obtained new insight into the clouds that dot the Red Planet. While these clouds have long been documented in Mars’ middle atmosphere (which begins about 18 miles or 30 kilometers above the surface), little was known about how they form in the thin, dry ‘air’ there.

New research shows that these wispy bodies are actually accumulations of “meteoric smoke”, the icy dust thrown up when meteorites or space debris break up in the planet’s atmosphere.

Dust rain

“We’re used to thinking of Earth, Mars and other bodies as these really self-contained planets that determine their own climates,” said Victoria Hartwick, a graduate student in the Department of Atmospheric and Ocean Sciences (ATOC) and lead author of the new study.

“But climate isn’t independent of the surrounding solar system.”

The most peculiar fact about Mars’ clouds is that they exist. The Big Bang notwithstanding, you can’t make something out of nothing, and clouds subscribe to this rule as well. Down here on Earth, low-lying clouds form on the backs of tiny particles — things like grains of sea salt or dust that get blown high into the air. These act as anchors of sorts for water vapor to condense on, growing into larger and larger drops, forming the large puffs of white or gray you can see from the ground.

To the best of our knowledge, however, that same mechanism doesn’t exist on Mars. There’s no sea salt to be blown up, and even if there was, the atmosphere is less dense so it’s less able to hold particles aloft. So Hartwick’s team turned their attention to meteors.

Around two to three tons of space debris rain down on Mars, on average, every single day, the authors explain. As this material, ranging from meteorites to space dust, comes into contact with the planet’s atmosphere, it starts to burn and break apart. In essence, a torrent of space dust ‘rains’ down on Mars.

So far, the theory seemed plausible — now the team needed to test it. To find out if this dust could generate Mars’ mysterious clouds, the team employed massive computer simulations that attempt to mimic the flows and turbulence of the planet’s atmosphere. After introducing meteors into the simulations, clouds started to appear.

“Our model couldn’t form clouds at these altitudes before,” Hartwick said. “But now, they’re all there, and they seem to be in all the right places.”

The findings are supported by previous research showing that a similar mechanism may help seed clouds near Earth’s poles (where the magnetic shield is weakest), the team explains. However, we shouldn’t expect to see enormous, roiling thunderstorms of cosmic dust above Mars: the clouds Hartwick’s team studied are very thin, “cotton candy-like clouds” explains Space.

“But just because they’re thin and you can’t really see them doesn’t mean they can’t have an effect on the dynamics of the climate,” Hartwick said.

Depending on the area, these clouds could cause temperature swings of up to 18 degrees Fahrenheit (10 degrees Celsius), the team’s model shows. The findings flesh out our understanding of Martian clouds and could help us better understand how ancient Mars regulated its climate, and how it was able to hold liquid water on its surface.

The paper “High-altitude water ice cloud formation on Mars controlled by interplanetary dust particles” has been published in the journal Nature Geoscience.

Research uncovered new, surprising melting patterns beneath the Ice Ross Shelf

Insight gained from a data collection survey of Antarctic Ice shows that local ocean currents play a heavy hand in how ice shelves evolve over time.

Ross Ice Shelf.

The Ross Ice Shelf.
Image credits lin padgham / Flickr.

Ice shelves are massive bodies of floating ice that form where glaciers meet the ocean. Such structures are humbling to behold, but they also play a central part in the evolution of the glaciers that spawn them. In Antarctica’s case, they slow down the flow of ice going from the continent into the ocean — and thus, slow down their rates of melting. One such ice shelf, the Ross Ice Shelf, dams around 20% of Antarctica’s ground ice from slipping under the waves.

The stakes are geological in proportion. All of the ice that the Ross Ice Shelf has been corralling is equivalent to an estimated 38 feet of global sea level rise, should it ever melt. And Antarctic ice has been experiencing an accelerated rate of melting. As such, it’s paramount that we properly understand shelf dynamics in the area and the factors that can hasten or slow the melting of the Ross Ice Shelf.

Local influence

Data gathered by a three-year, multi-institutional research effort — the ROSETTA-Ice project — comes to flesh-out our understanding of the area. The team reports they have assembled an unprecedented view of the structure and evolution of the Ross Ice Shelf over time. They also report uncovering a yet-unknown geologic structure that restricts the movement of local ocean currents, with significant effects on the ice shelf’s stability.

“We could see that the geological boundary was making the seafloor on the East Antarctic side much deeper than the West, and that affects the way the ocean water circulates under the ice shelf,” explains Kirsty Tinto, a researcher at Columbia University’s Lamont-Doherty Earth Observatory who led all three field expeditions and is the lead author of the study.

The team’s first hurdle to overcome was how to gather useful data on the whole of the Ross Ice Shelf, a region that’s roughly the same size as Spain. Further complicating the matter, ice in the shelf is frequently over a thousand feet thick, making it impossible to study the seabed here using traditional approaches (ship-based surveys).

Their solution was IcePod, a first-of-its-kind system designed to collect high-resolution data across the polar regions. Developed at Columbia University’s Lamont-Doherty Earth Observatory, IcePod incorporates several distinct measuring instruments meant to analyze ice shelf height, thickness, and internal structure, as well as the magnetic and gravity properties of the rock beneath. Mounted on a cargo plane, IcePod allowed the team to cover the whole study area over three missions.

During each flight, the magnetometer that’s part of IcePod showed a pretty stable signal up until halfway across the shelf — when it started displaying very large variations that the authors liken to heartbeat recordings on a cardiogram. After the team mapped these readings, they pointed to a previously unmapped segment of the geologic boundary that separates East and West Antarctica.

Shown here as a blue line.
Image credits K. J. Tinto et al., (2019), Nat.Geosc.

Gravity recordings from IcePod were then used to model the shape of the seafloor beneath the shelf, revealing the uneven structure Tinto’s earlier quote refers to. Based on this model, they simulated ocean current circulation beneath the shelf and its effect on melting rates.

The team reports that very little warm water reaches the Ross Ice Shelf — in stark contrast to the Amundsen Sea to the east, where warm water moves over the continental shelf and speeds up melting. In the Ross Shelf, heat from the deep ocean instead dissipates into the winter air in a region of open water called the Ross Shelf Polynya.  This cooled-down water then flows under the ice shelf. It still melts some ice — the deeper portions of the east Antarctic glaciers, for example — but it doesn’t reach the west Antarctic ice due to the new-found boundary.

Plot twist: the same polynya also creates a region of intense melting along the shelf’s leading edge during summer — as revealed by radar imaging of the shelf’s internal structure.

“We found that the ice loss from the Ross Ice Shelf and flow of the adjoining grounded ice are sensitive to changes in processes along the ice front, such as increased summer warming if sea ice or clouds decrease,” said Laurie Padman, a co-author and senior scientist at Earth and Space Research.

“We found out that it’s these local processes we need to understand to make sound predictions,” Tinto adds.

All in all, the results show how important local conditions are in predicting ice and climate evolutions over time, and why misunderstandings can throw a wrench into models based only on large-scale factors.

The paper “Ross Ice Shelf response to climate driven by the tectonic imprint on seafloor bathymetry” has been published in the journal Nature Geoscience.

PIA21863 Pluto.

Pluto’s ocean might be held in place by a thin layer of gas

This might also mean that there are many more oceans in the universe than previously thought.

PIA21863 Pluto.

Digital rendering, with exaggerated relief and color of Pluto. Based on close-up images taken by NASA’s New Horizons spacecraft in 2015. Credits NASA/Johns Hopkins University Applied Physics Laboratory.

It’s almost shocking to think how much we know about Pluto. The tiny ex-ex-planet was studied in unprecedented detail by the New Horizons missions that brushed right by it. The images sent by the shuttled showed Pluto’s topography in great detail, revealing some unexpected details. For instance, scientists were surprised by a white-colored ellipsoidal basin named Sputnik Planitia, located near the equator and roughly the size of Texas. The basin appears to be very thin, which would suggest the presence of a subsurface ocean beneath it. However, if this was true, researchers would have expected it to be long-frozen by now, which does not seem to be the case.

Now, researchers believe that they have an idea what happened.

Shunichi Kamata and colleagues from several Japanese universities propose that an “insulating layer” of gas hydrates exists beneath the icy surface of Sputnik Planitia. Gas hydrates are a crystalline solid formed from water and gas. They look and behave very much like ice, but contain high amounts of methane gas. They also have very low thermal conductivity, which means that they can essentially act as an insulator.

Since actually going to Pluto and drilling it on-site is not really an option, researchers tested their hypothesis with computer simulations. They generated a model of Pluto and its subsurface ice starting 4.6 billion years ago, when the solar system began to form.

The simulations confirmed that without an insulator, the subsurface ice would have long frozen over.

It also showed that the thermal and structural evolution of Pluto’s interior and the time required for a subsurface ocean to freeze and for the icy shell covering it to become uniformly thick. They simulated two scenarios: one where an insulating layer of gas hydrates existed between the ocean and the icy shell, and one where it did not.

The study has been published in Nature Geoscience. DOI: 10.1038/s41561-019-0369-8

Iceberg.

Nearly one quarter of West Antarctica ice is unstable, melting, study reports

Over the last 25 years, Antarctica’s ice sheet has thinned by up to 122 meters in certain areas. The most heavily-hit area is West Antarctica, where ocean melting is speeding up the process. However, affected glaciers are becoming unstable throughout the frozen continent, a new paper reports, meaning they lose more ice through melting and calving than they gain from snowfall.

Iceberg.

Image via Pixabay.

The authors of the study, a team from the UK Centre for Polar Observation and Modelling (CPOM) led by Professor Andy Shepherd from the University of Leeds, used 25 years’ worth of altimetry data recorded by European Space Agency satellites and a regional climate model to determine the state of Antarctic ice.

Antarctic, shaken, no ice, please

“In parts of Antarctica the ice sheet has thinned by extraordinary amounts, and so we set out to show how much was due to changes in climate and how much was due to weather,” Professor Shepherd explains.

“While the majority of the ice sheet has remained stable, 24% of West Antarctica is now in a state of dynamical imbalance,” the paper reads.

The patterns of glacier thinning have not been static, the team reports. Since 1992, glaciers across more than 24% of West Antarctica has begun to thin, as did those associated with the continent’s largest ice streams — the Pine Island and Thwaites Glaciers. These two glaciers are now melting a full five times faster than they were at the beginning of the survey, the team notes. All in all, fluctuations in snowfall do cause small changes in glacier volume for a few years at a time, but the significant changes observed by the team have persisted for decades and are indicative of the effects of climate-change-induced glacier instability, the team explains.

The data used in the study included over 800 million measurements of the Antarctic ice sheet height recorded by the ERS-1, ERS-2, Envisat, and CryoSat-2 satellite altimeter missions between 1992 and 2017 and simulations of snowfall over the same period produced by the RACMO regional climate model. This wealth of data allowed the team to tease apart changes in ice sheet height caused by weather — such as variations in snowfall — from longer-term changes caused by climate — such as warmer ocean water that melts ice away. To separate the two effects, the researchers compared the surface height readings obtained in the field to changes in snowfall they simulated using the RACMO model. In effect, any discrepancies between the two datasets are the product of glacier imbalance (i.e. of climate change).

“Knowing how much snow has fallen has really helped us to detect the underlying change in glacier ice within the satellite record,” says Professor Shepherd. “We can see clearly now that a wave of thinning has spread rapidly across some of Antarctica’s most vulnerable glaciers, and their losses are driving up sea levels around the planet.”

“Altogether, ice losses from East and West Antarctica have contributed 4.6 mm to global sea level rise since 1992.”

The study is a good example of how satellite data can be used to study large climate trends ongoing on our planet. This is especially true in hostile environments such as the arctic and antarctic, where ground-level missions are not only difficult but potentially deadly, as well.

The paper “Trends in Antarctic Ice Sheet Elevation and Mass” has been published in the journal Geophysical Research Letters.

Glacier ice.

Ice ages may be caused by tectonic activity in the tropics, new study proposes

New research says that the Earth’s past ice ages may have been caused by tectonic pile-ups in the tropics.

Glacier ice.

A crevasse in a glacier.
Image via Pixabay.

Our planet has braved three major ice ages in the past 540 million years, seeing global temperatures plummet and ice sheets stretching far beyond the poles. Needless to say, these were quite dramatic events for the planet, so researchers are keen to understand what set them off. A new study reports that plate tectonics might be the culprit.

Cold hard plates

“We think that arc-continent collisions at low latitudes are the trigger for global cooling,” says Oliver Jagoutz, an associate professor in MIT’s Department of Earth, Atmospheric, and Planetary Sciences and a co-author of the new study.

“This could occur over 1-5 million square kilometers, which sounds like a lot. But in reality, it’s a very thin strip of Earth, sitting in the right location, that can change the global climate.”

“Arc-continent collisions” is a term that describes the slow, grinding head-butting that takes place when a piece of oceanic crust hits a continent (i.e. continental crust). Generally speaking, oceanic crust (OC) will slip beneath the continental crust (CC) during such collisions, as the former is denser than the latter. Arc-continent collisions are a mainstay of orogen (mountain range) formation, as they cause the edges of CC plates ‘wrinkle up’. But in geology, as is often the case in life, things don’t always go according to plan.

The study reports that the last three major ice ages were preceded by arc-continent collisions in the tropics which exposed tens of thousands of kilometers of oceanic, rather than continental, crust to the atmosphere. The heat and humidity of the tropics then likely triggered a chemical reaction between calcium and magnesium minerals in these rocks and carbon dioxide in the air. This would have scrubbed huge quantities of atmospheric CO2 to form carbonate rocks (such as limestone).

Over time, this led to a global cooling of the climate, setting off the ice ages, they add.

The team tracked the movements of two suture zones (the areas where plates collide) in today’s Himalayan mountains. Both sutures were formed during the same tectonic migrations, they report: one collision 80 million years ago, when the supercontinent Gondwana moved north creating part of Eurasia, and another 50 million years ago. Both collisions occurred near the equator and proceeded global atmospheric cooling events by several million years.

In geological terms, ‘several million years’ is basically the blink of an eye. So, curious to see whether one event caused the other, the team analyzed the rate at which oceanic rocks known as ophiolites can react to CO2 in the tropics. They conclude that, given the location and magnitude of the events that created them, both of the sutures they investigated could have absorbed enough CO2 to cool the atmosphere enough to trigger the subsequent ice ages.

Another interesting find is that the same processes likely led to the end of these ice ages. The fresh oceanic crust progressively lost its ability to scrub CO2 from the air (as the calcium and magnesium minerals transformed into carbonate rocks), allowing the atmosphere to stabilize.

“We showed that this process can start and end glaciation,” Jagoutz says. “Then we wondered, how often does that work? If our hypothesis is correct, we should find that for every time there’s a cooling event, there are a lot of sutures in the tropics.”

The team then expanded their analysis to older ice ages to see whether they were also associated with tropical arc-continent collisions. After compiling the location of major suture zones on Earth from pre-existing literature, they reconstruct their movement and that of the plates which generated them over time using computer simulations.

All in all, the team found three periods over the last 540 million years in which major suture zones (those about 10,000 kilometers in length) were formed in the tropics. Their formation coincided with three major ice ages, they add: one the Late Ordovician (455 to 440 million years ago), one in the Permo-Carboniferous (335 to 280 million years ago), and one in the Cenozoic (35 million years ago to present day). This wasn’t a happy coincidence, either. The team explains that no ice ages or glaciation events occurred during periods when major suture zones formed outside of the tropics.

“We found that every time there was a peak in the suture zone in the tropics, there was a glaciation event,” Jagoutz says. “So every time you get, say, 10,000 kilometers of sutures in the tropics, you get an ice age.”

Jagoutz notes that there is a major suture zone active today in Indonesia. It includes some of the largest bodies of ophiolite rocks in the world today, and Jagoutz says it may prove to be an important resource for absorbing carbon dioxide. The team says that the findings lend some weight to current proposals to grind up these ophiolites in massive quantities and spread them along the equatorial belt in an effort to counteract our CO2 emissions. However, they also point to how such efforts may, in fact, produce additional carbon emissions — and also suggest that such measures may simply take too long to produce results within our lifetimes.

“It’s a challenge to make this process work on human timescales,” Jagoutz says. “The Earth does this in a slow, geological process that has nothing to do with what we do to the Earth today. And it will neither harm us, nor save us.”

The paper “Arc-continent collisions in the tropics set Earth’s climate state” has been published in the journal Science.

Sunset.

Massive solar storms are naturally-recurring events, study finds — and we’re unprepared for them

Solar storms can be even more powerful than what our measurements so far have indicated — and we’re still very unprepared.

Sunset.

Image via Pixabay.

Although our planet’s magnetic field keeps us blissfully unaware of it, the Earth is constantly being pelted with cosmic particles. Sometimes, however — during events known as solar storms, caused by explosions on the sun’s surface — this stream of particles turns into a deluge and breaks through that magnetic field.

Research over the last 70 years or so has revealed that these events can threaten the integrity of our technological infrastructure. Electrical grids, various communication infrastructure, satellites, and air traffic can all be floored by such storms. We’ve seen extensive power cuts take place in Quebec, Canada (1989) and Malmö, Sweden (2003) following such events, for example.

Now, new research shows that we’ve underestimated the hazards posed by solar storms — the authors report that we’ve underestimated just how powerful they can become.

‘Tis but a drizzle!

“If that solar storm had occurred today, it could have had severe effects on our high-tech society,” says Raimund Muscheler, professor of geology at Lund University and co-author of the study. “That’s why we must increase society’s protection again solar storms.”

Up to now, researchers have used direct instrumental observations to study solar storms. But the new study reports that these observations likely underestimated how violent the events can become. The paper, led by researchers at Lund University, analyzed ice cores recovered from Greenland to study past solar storms. These cores formed over the last 100,000 years or so, and have captured evidence of storms over that time.

According to the team, the cores recorded a very powerful solar storm occurring in 600 BCE. Also drawing on data recovered from the growth rings of ancient trees, the team pinpointed two further (and powerful) solar storms that took place in 775 and 994 CE.

The result thus showcases that, although rare, massive solar storms are a naturally recurring part of solar activity.

This finding should motivate us to review the possibility that a similar event will take place sooner or later — and we should prepare. Both the Quebec and Malmö incidents show how deeply massive solar storms can impact our technology, and how vulnerable our society is to them today.

“Our research suggests that the risks are currently underestimated. We need to be better prepared,” Muscheler concludes.

The paper “Multiradionuclide evidence for an extreme solar proton event around 2,610 B.P. (∼660 BC)” has been published in the journal Proceedings of the National Academy of Sciences.

Saturn rings.

Saturn’s rings are raining down — in about 100 million years, they’ll be gone

New research from NASA found that Saturn, the ring planet, is losing its rings.

Saturn and rings.

Image NASA / Cassini Imaging Team via Wikimedia.

Observations made decades ago by Voyager 1 and Voyager 2 show that Saturn is devouring its own rings, NASA reports. The particles making up these striking structures are falling onto the planet as a rain of dust and ice, propelled by Saturn’s gravity and magnetic field.

One ring to bind them

“We estimate that this ‘ring rain’ drains an amount of water products that could fill an Olympic-sized swimming pool from Saturn’s rings in half an hour,” said James O’Donoghue of NASA’s Goddard Space Flight Center in Greenbelt, Maryland, the study’s lead author.

“[…] The rings have less than 100 million years to live. This is relatively short, compared to Saturn’s age of over 4 billion years.”

The research actually began with scientists trying to figure out if Saturn formed with its rings or acquired them later. The second scenario seems to be the more likely, the team reports. In fact, they estimate that the rings are no older than 100 million years. The team based this age on how much it would take for the C-ring to form from a (hypothetical) original B-ring-like structure. Here’s a chart for your convenience:

Saturn rings.

Saturn rings and with their major subdivisions.
Image credits NASA / JPL / Space Science Institute via Wikimedia.

There are quite a number of theories in regards to how Saturn got its rings (the most prevalent of which we’ve talked about here). If they’re younger than the planet itself, the rings could be the product of collisions between Saturn and small, icy moons. Such a mechanism would be supported by the rings’ present makeup — chunks of water ice ranging from several yards across to microscopic sizes.

Still, the finding that Saturn acquired its rings later in life is, perhaps, overshadowed by the realization that it’s eventually going to lose them. O’Donoghue says, we’re “lucky to be around” while Saturn still has rings. They’re probably around the middle of their lifetime, he adds. The other side of the coin is that we’ve perhaps missed out on seeing similarly lush ring systems around Jupiter, Uranus, and Neptune. While these gas giants do have ring systems today, they’re thin, wispy things.

Black belt giant

The first hints that Saturn’s rings were raining down on the planet came from Voyager readings on (seemingly) unrelated phenomena: variations in Saturn’s ionosphere (electrically-charged upper atmosphere), density variations in its rings, and the planet’s three dark bands These bands encircle the planet at high altitudes (stratosphere) at northern mid-latitudes, and were first spotted by the Voyager 2 mission in 1981.

Later, a NASA Goddard researcher named Jack Connerney linked (paper here) these bands to the planet’s massive magnetic field. Connerney’s hypothesis was that the bands form as electrically-charged ice particles from Saturn’s rings flowed down magnetic field lines. Tiny particles can get electrically charged by ultraviolet light from the Sun or by plasma clouds emanating from micrometeoroids impacting the rings.

Essentially, water pouring into the planet’s upper atmosphere was what formed these bands. The water would literally wash away haze in Saturn’s stratosphere, making them less reflective of light — so the bands appear darker.

So what actually causes the rings to rain down? Well, they’re generally kept in orbit by an interplay between the planet’s gravitational field (which pulls them down) and the centrifugal force generated by the rings’ rotation (which pushes them outwards, or ‘up’).

Things become more complicated when Saturn’s magnetic field gets involved, however. Those electrically-charged particles we talked about earlier also start feeling the pull of the planet’s magnetic field, which curves towards Saturn at its rings. In some parts of the rings, this magnetic pull is enough to dramatically shift the balance of forces on particles — it neutralizes, to an extent, the centrifugal force. Gravity takes hold, pulling the particles down on the planet.

These infalling bits of water chemically react in Saturn’s ionosphere, generating H3+ ions. O’Donoghue picked up on these ions using the Keck telescope in Mauna Kea, Hawaii, as H3+ ions glow in infrared light. The team saw glowing infrared bands in Saturn’s northern and southern hemispheres where magnetic field lines enter the planet. By analyzing the infrared light output, the team calculated the quantity of infalling ring matter (i.e. of how fast they are degrading).

The highest influx of infalling ice, the paper adds, is found in an area in southern Saturn. Some of the matter spewed by Enceladus’ ice geysers also finds its way down to the gas giant, which Connerney says isn’t “a complete surprise.”

So far, the results are pretty solid. However, the team says observing Saturn as it goes around the sun (on a 29.4-year orbit) would conclusively prove or disprove the findings. On its trek, Saturn’s rings will be exposed to various degrees of ultraviolet light — which charges ice particles in the rings. If researchers find that different levels of exposure to sunlight change the quantity of ‘rain’ on Saturn, the study’s conclusions would be confirmed.

The paper “Observations of the chemical and thermal response of ‘ring rain’ on Saturn’s ionosphere” has been published in the journal Icarus.