Tag Archives: melt

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.

NASA creates stunning visualization of melting snowflake

For the first time, researchers have created a 3D numerical model of melting snowflakes in the atmosphere. Aside from just painting a pretty, scientifically accurate picture, this could also help scientists develop better weather models and predictions.

This model reproduces key features of melting snowflakes that have been observed in nature: first, meltwater gathers in any concave regions of the snowflake’s surface. These liquid-water regions merge as they grow and eventually form a shell of liquid around an ice core, finally developing into a water drop. Credit: NASA.

If there’s anything this winter has taught us, it’s that weather is still surprising. Weather predictions have come a long way, but the sheer complexity of all the elements involved makes it very difficult to create accurate models — one of those elements which adds complexity is snow.

Snow not only affects weather predictions, but it also affects remote sensing. For instance, a radar “profile” of the atmosphere will typically show a very bright layer at the altitude where falling snow and hail melt — much brighter than atmospheric layers above and below it. We don’t really know why this happens, and we don’t understand many things about how snow starts to melt high up in the atmosphere. This is where NASA’s Jussi Leinonen enters the stage.

Leinonen created a melting model for snowflakes. He started his model by observing snowflakes in nature and noting the different melting stages. First, the outer parts start to melt, creating a bit of liquid water. This meltwater gathers in any concave regions it can find, and then the different droplets merge to form a liquid shell around the ice core. Ultimately, this melted core develops into a water drops, as can be seen above.

Although snowflakes notoriously have different intricate forms, the process seems to carry out similarly, regardless of what the shape might be.

While this isn’t the first model of snow melting, it’s by far the most accurate. This improvement could lead to significant improvements in several fields of research. Taking into consideration the individual dynamics of individual snowflakes can help researchers better understand the cryosphere — the collection of the Earth’s ice sheets, glaciers, sea ice, snow cover, and permafrost.

In 2018, NASA will launch two new satellite missions, conducting an array of field research that will enhance our understanding of the Earth’s cryosphere.

The paper, titled “Snowflake melting simulation using smoothed particle hydrodynamics,” recently appeared in the Journal of Geophysical Research – Atmospheres.

The Greenland ice sheet is losing some 270 billion tons of ice each year, a new study finds

A new study focusing on the Greenland Ice Sheet found that the rate of ice loss has accelerated over the past few years, confirming previous measurements. To put it into perspective, the sheet is now losing some 110 million Olympic-size swimming pools of water every year.

Image credits NASA Goddard Space Flight Center / Flickr.

One direct consequence of all the greenhouse gases we’re emitting into the atmosphere is melting ice. Doesn’t sound so dramatic — ice on my front lawn melts every spring, there’s ice-covered lakes and ice-bergs that sometimes melt and a little water never hurt anybody, right? For those things, yes. It’s a small quantity of ice, and it’s already floating on bodies of water so it won’t affect the volume of the world’s oceans if it melts.

But our planet has one huge deposit of water that doesn’t take part in the liquid’s natural cycle — ice sheets. When these melt, the water finds its way into the ocean and raises the sea level of the world’s oceans. So knowing how melting happens every year is important not only to help us quantify our activity’s effect on climate, but also because it helps us estimate how much sea levels rise.

However, you can’t simply hammer a tap into the ice and measure how much water flows out. What we can do is measure the volume of ice. This requires high-precision measurements of the ice sheets’ sizes over a long period of time to yield reliable results. In a new study, an international team reports the findings of one such high-precision measurement of the Greenland Ice Sheet, and their results confirm previous estimates of its rate of melting.

Malcolm McMillan from the Centre for Polar Observation and Modeling and his colleagues mapped the ice-sheet with incredibly high resolution (5 km distances,) by using data from the CryoSat 2 satellite. It relies on a technique called radar altimetry to measure terrain height, and with it the team was able to track the behavior of Greenland’s ice sheets with more precision than ever before.

In theory, if an ice sheet gains in altitude, it means that it’s also gaining in volume, so there’s more ice. A drop in altitude would correspond to a thinning of the ice caused by melting. But the processes that create the sheets are a little more complex — the Greenland sheets are thousands of meters thick, but the top layers are made up of snow and firn which gradually compress into solid ice. Accounting for the constitution of the sheet thus becomes very important in determining how much water gets trapped or released into the ocean.

After accounting for changes in density, surface roughness, and water content the authors found how much ice Greenland is losing, and how this melt varies by location and time. For example, 2012 saw a huge amount of ice loss compared to other years. The western side of the ice sheet is also melting much faster than the eastern side. The team found that a small part of the ice sheet (less than 1% of the sheet) is responsible for more than 10% of the mass loss.

Rate of mass change between January 2011 and December 2014 from CryoSat-2 radar altimetry. The color wheel indicates ice mass lost each year, with the radius scaled according to the magnitude of the total losses. The boundaries between the four sectors are shown in gray. Image provided by authors.

Rate of mass change between January 2011 and December 2014 from CryoSat-2 radar altimetry. The color wheel indicates ice mass lost each year, with the radius scaled according to the magnitude of the total losses. The boundaries between the four sectors are shown in gray.
Image credits Malcolm MacMillan et. al, 2016.

They estimate that between 2011 and 2014, some 270 gigatons of ice have melted away from Greenland — that’s enough water to fill 110 million Olympic swimming pools each year. This matches other independent measurements almost perfectly, helping to confirm the numbers.

“Using high resolution satellite data from ESA’s CryoSat-2 mission, we have produced a detailed and comprehensive picture of how Greenland has changed in recent years. In particular, we have been able to map the changing ice sheet in fine detail, and pinpoint where, and when, the greatest ice losses have occurred,” McMillan said in an interview for The Guardian.

The measurements allow scientists to calculate how much ice has been lost every year and determine the relationship between mean temperatures and melt — by looking at melt during the record summertime temperatures of 2012, for example. The variations in ice quantity show to what extent Greenland contributes to the sea level rise we’ve seen in recent years. And, thanks to their high resolution, researchers can also highlight which glaciers are experiencing the most melt.

The duration of this study was a relatively short 4 years. Hopefully, the team will continue their measurements in the following years, so we can get a better understanding of how sea levels will evolve in the future.

The full paper, titled “A high-resolution record of Greenland mass balance” has been published online in the journal Geophysical Research Letters.

Huge portion of Greenland starts to melt, surprises scientists

A massive portion of the Greenland ice sheet has started to melt, taking researchers by surprise. The vast region is experiencing a freakishly early spring thaw, with 12% of Greenland’s ice melting on Monday, according to the Danish Meteorological Institute.

“We had to check that our models were still working properly,”6 Peter Langen, climate scientist at DMI, told blog Polar Portal.

Left: Maps showing areas where melting took place on Monday (April 11th) and Tuesday (April 12th). Right: Average percentage of the total area of the Greenland ice sheet that melts over the course of a year, from 1990-2013 (gray) compared with 2016 (blue). Image: DMI

This is extremely worrying. Not only is a big part of Greenland melting, but it’s melting much sooner than it normally is. Thawing season normally starts in late May or June. The three earliest ever recorded meltings started in May 5, 2010, May 8, 1990, and May 8, 2006. This is almost a month earlier. Basically, these are hot days for July, let alone April.

“Even weather stations quite high up on the ice sheet observed very high temperatures on Monday”, said Robert Fausto, a scientist at GEUS who maintains PROMICE.dk melt data. “At KAN_U for example, a site at 1840 m above sea level, we observed a maximum temperature of 3.1°C. This would be a warm day in July, never mind April”. Other PROMICE stations in the network at lower levels had daily average temperatures between 5 and 10 °C. 

The good news is that because this happened so early in the year, there’s a good chance that the melting water will freeze again, but the bad news is that by doing so, it will suck heat energy from the depths, which means that the entire system will be left more vulnerable in the face of future thawings. All in all, it seems like Greenland is set for another hot year.