Tag Archives: atlantic

A new tropical storm, Peter, has formed in the Atlantic. Another, Rose, is likely to follow soon

A new tropical storm has been brewing in the Atlantic. Christened “Peter”, it marks the 16th named storm of this year’s hurricane season.

Forecasted path of tropical storm Peter. Image credits National Hurricane Center.

Tropical storm Peter formed east of the Caribbean on Sunday, centered some 400 miles off the Leeward Islands. According to the National Hurricane Center (NHC), the storm is expected to pass north of the Lesser Antilles and is likely to produce between one and three inches of rainfall around its edge. Puerto Rico, the Virgin Islands, and the Leeward Islands are liable to see “areas of urban and small stream flooding” up through Tuesday, the NHC adds. Top wind speeds are expected to fall below or around 45 mph (72.5 km/h).

Stormy again

Although it has barely been a week since Hurricane Nicholas slid across Texas and Louisiana, and just a little over three since Hurricane Ida battered the same shores, a new storm is brewing in the Atlantic.

Tropical storm Peter is the sixth hurricane to form this year. Along with these, three major hurricanes (meaning they were a category 3 or higher in intensity) have raged in 2021, making it quite the busy year. Naturally, more could be on the way. As far as Peter is concerned, the NHC notes that a strong cold mass of air is moving eastward across the U.S., which is likely to butt heads with the storm. This front of cold air should push Peter back out to the ocean and insulate the Eastern Seaboard, if not completely, then at least to a certain extent.

Despite the formation of this tropical storm, no coastal watches or warnings were in effect as of this Sunday in any of the areas highlighted by the NHC.

Forecasters are also keeping tabs on a tropical depression in the eastern Atlantic. This particular low-pressure system was picked up around 315 miles west-southwest of the Cabo Verde Islands (off the western coast of Africa). While not particularly intense right now, moving northwards at around 14 mph with sustained winds of around 35 mph (22.5 and 56.3 km/h respectively), there is still a high chance that it will morph into a new tropical storm — which will be named “Rose”. The two storms started coalescing pretty much at the same time, but Peter developed more rapidly in intensity.

If we consider Rose as well, this would be the third Atlantic hurricane season in recorded history to have 17 named storms by the 20th of September. The others were the 1966 season, the 2005 one, and 2020. The link between climate change and freak weather or events such as hurricanes has been highlighted in the past, and the high incidence of storms recorded this season certainly seems to follow that hypothesis.

Each hurricane in every year is given a name starting with the corresponding letter of the alphabet — A for the first, B for the second, and so on. Last year, in particular, had so many named storms that meteorologists exhausted the alphabet and had to assign Greek letters, only the second time in history that this has happened. It still holds the record for the highest number of storms in a single year, 30. The runner-up is still the 2005 hurricane season, with 28 recorded storms.

Hurricanes are primarily fed by expanses of open, warm water. As the planet’s climate heats up overall, so do the oceans, meaning we’re likely to see stronger and more frequent events of this kind in the future. They are also likely to become wetter — to carry more precipitation — due to higher overall levels of moisture in the atmosphere, as higher mean temperatures lead to higher levels of surface evaporation. As storms increase in intensity and sea levels rise, they are also liable to generate more storm surges, and thus become more dangerous over time.

A report by the United Nations released in August has also issued a warning to this extent. According to the document, unavoidable shifts in climate will lead to more intense and more frequent heatwaves and droughts over the next 30 years. Hurricanes have already been following this trend for the last 40 years, it adds.

Belize Sargassum.

Satellite imaging used to spot the largest seaweed bloom in the world

Researchers at the USF College of Marine Science report discovering the largest bloom of macroalgae in the world — the Great Atlantic Sargassum Belt (GASB).

Belize Sargassum.

Sargassum on a beach in Belize.
Image via Pixabay.

Based on computer simulations, the team reports that the GASB’s shape has formed in response to ocean currents. This brown macroalgae belt blankets the surface of the tropical Atlantic Ocean from the west coast of Africa to the Gulf of Mexico, and formed last year as 20 million tons of algae floated in surface waters and wreaked havoc on shorelines around the tropical Atlantic, Caribbean Sea, Gulf of Mexico, and the east coast of Florida.

All the algae

The seaweed, the team reports, grows seasonally in response to two nutrient inputs, one natural and one human-derived. The Amazon River’s spring and summer discharge floods the ocean with fresh nutrients; this discharge may have increased in recent years due to deforestation and fertilizer use in the area. In the winter, upwelling off the West African coast delivers nutrients from deep waters to the ocean surface where the Sargassum grows.

“The evidence for nutrient enrichment is preliminary and based on limited field data and other environmental data, and we need more research to confirm this hypothesis,” said Dr. Chuanmin Hu of the USF College of Marine Science, who led the study and has studied Sargassum using satellites since 2006.

“On the other hand, based on the last 20 years of data, I can say that the belt is very likely to be a new normal,” said Hu.

Hu’s team used data from NASA’s Moderate Resolution Imaging Spectroradiometer (MODIS) between 2000-2018. They also analyzed fertilizer consumption patterns in Brazil, Amazon deforestation rates, Amazon River discharge, and two years of nitrogen and phosphorus measurements taken from the central western parts of the Atlantic Ocean (among other ocean properties) to see whether they linked with the blooms.

Bloom evolution.

Image credits Mengqiu Wang, Chuanmin Hu / USF College of Marine Science

Based on the data, they report a possible shift in the pattern of these blooms since 2011. Before this point, most of the pelagic Sargassum in the ocean was clumped up around the Gulf of Mexico and the Sargasso Sea (on the western edge of the central Atlantic Ocean). After 2011, Sargassum populations made big appearances in places the algae hadn’t been encountered before, such as the central Atlantic, growing in massive blobs that suffocated local life along the shoreline and entangled shipping. Some countries, such as Barbados, declared a national emergency because of the toll this once-healthy seaweed took on tourism.

“The ocean’s chemistry must have changed in order for the blooms to get so out of hand,” Hu said.

Sargassum reproduces vegetatively (i.e. from a parent plant or fragments), and the team believes there are several ‘initiation zones’ from which it propagates into the wider Atlantic. They also explain that the plant grows faster when environmental conditions are favorable. The results, while preliminary, do show a strong correlation between the recent boom in Sargassum and increases in deforestation and fertilizer use since 2010.

Key factors for bloom formation, the team found, are:

  • A large seed population in the winter left over from a previous bloom.
  • Nutrient input from West Africa upwelling in winter.
  • Nutrient input in the spring or summer from the Amazon River.
  • In addition, Sargassum only grows well when salinity is normal and surface temperatures are normal or cooler.

The bloom in 2011 was caused by rich Amazon discharge from previous years compounding with upwelling in the eastern Atlantic and river discharge on the western Atlantic. Major blooms occurred yearly after this, with the exception of 2013, as all the ingredients on the list were present. No bloom occurred in 2013 because the seed populations measured during winter of 2012 were unusually low, said first author Dr. Mengqiu Wang. The first large bloom didn’t occur in 2010 because heavy rains in 2009 reduced the overall salinity in the Amazon discharge area and because surface temperatures were higher than usual.

“This is all ultimately related to climate change because it affects precipitation and ocean circulation and even human activities, but what we’ve shown is that these blooms do not occur because of increased water temperature,” Hu said.

“They are probably here to stay.”

The team reports that what we’ll likely see in the future is a recurring pattern of Sargassum blooming in late January to early April, which will develop into a Great Atlantic Sargassum Belt up through to July. After this, the bloom will increasingly dissipate until winter.

“We hope this provides a framework for improved understanding and response to this emerging phenomenon,” Hu said. “We need a lot more follow-on work.”

The team, however, cautions that predicting future blooms and their evolution is tricky because they depend on a large palette of factors that are hard to predict.

The paper “The great Atlantic Sargassum belt” has been published in Science.

Barents Sea.

Barents Sea just crossed a climate tipping point — and we watched it happen

We may have just witnessed a climate tipping point in the Barents Sea, research suggests.

Barents Sea.

The Barents Sea.
Image credits NASA / Earth Observatory.

Climate change is a lumbersome beast. Threats associated with climate change — such as rising seas, an increase in extreme weather events, environmental degradation, or loss of biodiversity — involve huge and hugely complex systems, which have a lot of inertia. However, such processes are not completely devoid of sudden shifts, and we refer to these events as climate tipping points.

We’re pretty poor at spotting an incoming tipping point — but we’re quite capable of identifying them in retrospect; hindsight 20/20 and all that. While we’ve found evidence of such tipping points affecting Earth’s climate in the past, we couldn’t accurately reconstruct how fast these events took place. Now, a team of Norwegian researchers says they’ve watched such a tipping point while it was happening. According to a paper they recently published, this tipping point involves the Barents Sea. The loss of Arctic sea ice in the region has fundamentally changed the Sea, from a buffer between the Atlantic and Arctic ocean into a de facto extension of the Atlantic.

A sea change

The Barents Sea lies north of Norway and Russia, flanked by the Atlantic to its west and the Arctic Ocean to its North. It’s also one of the most intensely-monitored areas in the world. The paper draws on over five decades of temperature, ice cover, salinity, and other indicators recorded in the area. This wealth of data allowed the team to reliably fix a baseline from which to spot longterm changes. It also means that we’ve just happened to spot a major change as it was taking place.

Ice from the Arctic Ocean spreads over the Barents during winter. It helps thermally insulate the waters and blocks incoming sunlight — which helps keep Arctic waters colder during summer months. As this ice melts, it creates a layer of fresh water that doesn’t mix with the column of salt water under it (salty water is denser), floating on the surface like oil on water instead. In contrast, water flowing in from the Atlantic is both warmer and saltier than that of the Barents Sea.

Because of this, the sea (which lies between the two oceans) boasts a layer of intermediate water. Arctic water and ice keep surface waters chilly and fresh. Water from the Atlantic, being dense, flows to the bottom; it’s not warm enough to rise towards the surface. The Barents’ waters lie between these two ‘intruders’, forming the intermediate layer, with its own salinity levels and average temperatures.

This layered structure was “remarkably stable” from 1970 all the way through 2011, the team notes. However, signs of change could be seen even as these layers persisted — atmospheric temperatures over the Arctic have seen a steady rise, warming faster than any other region on Earth. This contributed to a dramatic decline in ice cover throughout the Arctic Ocean, reaching then-record lows in 2007 and 2008.

Because there wasn’t any ice to flow south, the Barents remained relatively ice-free during the Arctic summer. Average sea-ice drift into the Barents in 2010-2015 was 40% lower than the 1979-2009 mean, the team writes. Right now, it’s completely ice-free, despite the fact that the melt season historically lasts through to September. The team also checked precipitation levels on islands bordering the Barents Sea, such as Svalbard and Franz Josef Land, to confirm that the loss of fresh water came down to loss of ice, not a change in weather patterns.

Barents sea.

Ocean heat content in the northern Barents Sea, observed during 1970–2016.
Image credits Lind et al., 2018, Nature.

The sea’s surface layer rapidly declined in the absence of ice to insulate it. The top 100m of water has heated up dramatically over the past few years, according to the team. Mean temperatures between 2010 and 2016 were nearly four standard deviations higher than the 1970-1999 mean. In 2016, they were 6.3 standard deviations higher.

Sandwiched between two warmer bodies of water, the intermediate layer has also been heating up. The team reports that starting with the late 2000s, the entire water column has both warmed and gotten saltier. The intermediate has now all but vanished from the Barents Sea, the team notes, which is now dominated by water flowing in from the Atlantic. Even worse, warmer waters with higher salt content make it extremely difficult for sea ice to re-establish itself during winter.

“Increased Atlantic Water inflow has recently enlarged the area where sea ice cannot form, causing reductions in the sea-ice extent,” the team writes.

“The entire region could soon have a warm and well-mixed water-column structure and be part of the Atlantic domain.”

While it may not sound like a big deal to us, from an ecosystems point of view, these changes are immense. The authors describe the Barents as “divided into two regions with distinct climate regimes—the north having a cold and harsh Arctic climate and ice-associated ecosystem, while the south has a favorable Atlantic climate with a rich ecosystem and lucrative fisheries”. Now, however, it’s becoming one big Atlantic climate ecosystem.

The findings help provide some context as to the sheer scale of changes such tipping points can usher in — and how fast they can do so. The team says we’re likely to see a lot of regional tipping points such as this one, not a single, planet-spanning super tipping point. The future, however, will be built on the sum of these events and the way they interact — making it extremely hard to predict just what that future will look like.

The paper “Arctic warming hotspot in the northern Barents Sea linked to declining sea-ice import” has been published in the journal Nature.

Tsunamis in the Atlantic – unlikely, but possible

There’s been a lot of fuss around tsunamis lately, especially seen as Japan, perhaps the most prepared country in the world, was devastated by them. A tsunami in the Atlantic however, is a rare sight, due to the fact that that there are no subduction areas, the most common cause of tsunami-causing earthquakes.

Map of reported tsunamis; credit NOAA

However, even though the tsunami threat in the Atlantic region is quite low, it should definitely be taken into consideration, especially as millions of people live in low elevation areas around the Atlantic basin. The most famous example of a tsunami in the Atlantic took place more than 200 years ago, in 1755, in Lisbon, caused by what is believed to have been a 8.6 magnitude earthquake, generating waves as high as 12 meters and killing approximately 100.000 people; however, an event of this magnitude today would definitely do much more damage as the area is much more populated.

The latest major tsunami causing event took place in 1918, when a 7.3 earthquake struck Puerto Rico and generated tsunamis of 6-7 meters. However, the bad thing is that due to the fact that there is a low risk for those areas, there is little to no preparation made, so unfortunately, a big tsunami in the Atlantic basin would have absolutely devastating effects.