Researchers from the British Antarctic Survey and the University of Southampton found direct observational evidence that changes in the winds and sea ice formation change are warming and shrinking the bottom water production in the Weddell Sea of Antarctica. This sea is one of Earth’s most extensive, dense, frigid bottom water producers.
The Weddell Sea was very late in forming sea ice for weeks, ice-free in the bitter cold of winter. Antarctic sea ice is the lowest in recorded history despite record-breaking cold atmospheric temperatures. The Weddel Sea is not an outlier. The Ross Sea is experiencing the same phenomenon.
From CNN:
Deep ocean water in the Antarctic is heating up and shrinking, with potentially far-reaching consequences for climate change and deep ocean ecosystems, according to a report.
“Antarctic bottom water” is the coldest, saltiest water on the planet. These waters play a crucial role in the ocean’s ability to act as a buffer against climate change by absorbing excess heat and human-caused carbon pollution. They also circulate nutrients across the ocean.
But in the Weddell Sea, located east of the Antarctic Peninsula, this vital water mass is in decline, due to long-term changes in winds and sea ice, according to the study published Monday by the British Antarctic Survey.
They found that the volume of the cold bottom waters has shrunk by more than 20% over the past three decades. They also found that ocean waters deeper than 2,000 meters (6,600 feet) have warmed four times faster than the rest of the global ocean.
“We used to think that changes in the deep ocean could only occur over centuries. But these key observations from the Weddell Sea show that changes in the dark abyss can take place over just a few decades,” Alessandro Silvano from the University of Southampton in the UK, a co-author of the study, said in a statement.
From the University of South Hampton presser:
The new study discovered that the shrinking bottom waters are a result of a slowing sea ice formation.
Normally, strong winds push newly formed ice away from the shelf, creating open areas for more ice to form. But weakening winds near the Filchner-Ronne ice shelf in the Southern Weddell Sea have reduced the size of these gaps in the sea ice cover, resulting in a slowdown in the formation of new ice.
As new ice forms, it leaves behind salt, contributing to the creation of the cold and salty Antarctic Bottom Water. The shortage of these salty shelf waters has triggered the shrinking of bottom waters.
The researchers uncovered an interplay between large-scale atmospheric patterns, connecting responses in the tropical Pacific to the Southern Ocean. Changes in these patterns have caused shifts in the winds across the Southern Ocean, resulting in reduced northerly winds across the Weddell Sea, and in turn a reduction in sea ice formation.
The changes are a consequence of natural variability in the system, although potentially stronger changes are predicted in the future.
This is untrue.
The changes are a consequence of natural variability in the system, although potentially stronger changes are predicted in the future.
See Fish out of Waters comment below.
There is natural variability involved, but there has been a huge build up in ocean heat between New Zealand and Antarctica. There has also been heat build up off of the east coasts of south America and south Africa. This heat build up in these areas is controlled by subsea topography and fundamentally, the locations of the continents. This heat build up locks in a 3 wave pattern in the atmosphere and that 3 wave pattern drives the intensification of storms and winds around Antarctica. So, the observational science in this study is great, but the “it’s just natural variability” part comes from their lack of understanding of the interconnections between the ocean and the atmosphere, something that I have been beating myself over the head with for about 50 years. Jim Hansen, trained as a radiation physicist, gets these problems and predicted this slowdown around Antarctica. He’s a real interdisciplinary scientist who has pulled the pieces together and made bold and correct predictions. These scientists have done great work, but they have not understood the connections between the ocean and the atmospheric circulation patterns.
Now, remember that the reduction in sea ice hampers the ability of solar energy to be bounced back to space. The solar heat is instead absorbed within the Southern Ocean water column.
An area the size of Argentina is missing its sea ice. Over the last four decades, the southern ocean has absorbed 90% of heat and a third of CO2 emissions. The stored heat is starting to give it back, and is one reason why the heatwaves on land and the oceans are shattering temperature records.
The bottom waters also provide oxygen to the depths of the southern ocean. It is not yet known what that means for deepwater marine systems. Additionally, the ocean heat has primed Antarctica for rapid melting as spring and summer arrive in Antarctica. Satellite imagery of the continent should be available for scrutiny in September and October; we will see what damage has occurred to the ice shelves from the open ocean during this past winter.
Yale 360 writes on the collapse of the Antarctic currents. It is not good news.
It is being hailed as a sea change in scientific understanding of the global ocean circulation system and how it will respond as the world heats up. A doomsday scenario involving the collapse of the circulation — previously portrayed in both peer-reviewed research and the climate disaster movie The Day After Tomorrow — came a lot closer in the last month. But rather than playing out in the far North Atlantic, as previously assumed, it now seems much more likely at the opposite end of the planet.
A new analysis by Australian and American researchers, using new and more detailed modeling of the oceans, predicts that the long-feared turn-off of the circulation will likely occur in the Southern Ocean, as billions of tons of ice melt on the land mass of Antarctica. And rather than being more than a century away, as models predict for the North Atlantic, it could happen within the next three decades.
snip
And after 2050, their model predicts that things will get even worse. Deep-water formation “looks headed towards collapse this century,” the coordinator of the study, Matthew England of the University of New South Wales, told Yale Environment 360. “And once collapsed, it would most likely stay collapsed until Antarctic melting stopped. At current projections that could be centuries away.”
“The physics at play is pretty simple,” says England. “None of the steps is particularly surprising or complex. But until our study, we did not have the circulation model … to make confident predictions.” The slowdown itself, he says, “didn’t surprise me. But the pace of change — to see a 40 percent slowdown in under three decades — was definitely a surprise.”
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The Sea Shepherd exposed the industrial operators that took the food out of the mouths of over one thousand fin whales. Spread the trawler’s shame.
Krill is a generic term to describe 86 species of ocean crustaceans. Commercial interests exploit three species of Krill. They are the Antarctic Krill, Pacific Krill, and Northern Krill. According to scientists, all of them are keystone species. Krill are social and aggregate in areas as large as a few yards to over 115 square miles, which can be seen from orbit. If we don’t count bacteria, Krill is the largest multi-cellular biomass on Earth. They are the food for fish, birds, seals, penguins, and baleen whales. These Antarctic animals’ feces fertilize the world’s oceans. The Southern Ocean is not impacted by dust from the Sahara and runoff as in the other world oceans. Only by krill poop and the poop from the species that feed on them can the ocean conveyor belt of marine nutrition operate. Everything in the web of life is connected.
The below was originally posted in The Conversation, a creative commons site, authors Emma Cavan, Postdoctoral Research Associate in Ecosystem Modelling, Imperial College London, Anna Belcher Ecological Biogeochemist, British Antarctic Survey, and Lavenia Ratnarajah Postdoctoral research associate, University of Liverpool.
Krill are best known as whale food. But few people realise that these small, shrimp-like creatures are also important to the health of the ocean and the atmosphere. In fact, Antarctic krill can fertilise the oceans, ultimately supporting marine life from tiny plankton through to massive whales and, through their faeces, they can increase the store of carbon in the deep ocean.
In a review we recently published in Nature Communications, we highlighted this less well-known role of Antarctic krill.
Krill are able to fertilise the oceans and help store carbon because they release essential nutrients, including ammonium and iron, into the surrounding water, either excreted as a waste product or in solid faecal pellets. These nutrients can then be used by tiny ocean plants at the base of most marine food webs (phytoplankton) to photosynthesise and grow. This is much the same process as humans adding nutrients to a field through a fertiliser.
The Southern Ocean surrounds Antarctica and is a long way from landmasses from which nutrients are washed into the ocean. As a result, nutrient concentrations can be low, particularly of iron which is essential for phytoplankton to grow. Concentrations tend to be highest near the Antarctic continent itself, its sea-ice and a few remote islands.
Krill waste also influences the carbon cycle. Krill poo is in the form of relatively large, carbon-rich pellets which can sink quickly to the deep ocean where they may remain for many years. This means krill poo can lock carbon away from the atmosphere for long periods of time.
But what happens when humans disrupt these natural cycles, for example through fishing or causing climate change?
Humans also commercially fish for Antarctic krill – in fact, krill is the most fished animal in the Southern Ocean. Their oily bodies are either used in pharmaceuticals as an alternative source of omega-3, fed to livestock and aquaculture fish, used in pet food or a small amount are even prepared for humans to eat.
The global climate is one hugely complex interconnected system. While the Antarctic and Southern Ocean are far removed from our daily lives, they play an oversized role in this system and the future climate that concerns humanity now. “Global warming” is really “ocean warming”. The atmospheric temperature change, the 1.5C Paris target we are now perilously near to exceeding, really is only a few percent of our total excess trapped heat. Almost all the rest is in the ocean and it is around Antarctica that it is predominantly taken up. How this uptake may change in the future as winds, temperatures and ice shift is a critical scientific, and human, question.
This unique exchange between the atmosphere and Southern Ocean is controlled by the combination of extreme cold and freezing at the Antarctic margins and the constant blowing of the roaring 40s, furious 50s and screaming 60s. They act to pump deep old water to the surface and push newly modified water, fresh with observable human fingerprints of heat, meltwater, carbon and oxygen, into the ocean abyss where it may be trapped for centuries or longer. These old deep waters also bring nutrients to the surface; nutrients that are then exported to replenish and sustain the warmer oceans that we fish. However, recent studies from multiple research centres show this overturning has weakened over the past decades and components of it may even collapse in the coming century.
The Roaring 40s, Furious 50s and Screaming 60s are winds that batter the Southern Ocean, on the fringes of Antarctica. Their names are nods to the latitudes at which they occur in the Southern Hemisphere, and are terrifying in the intensity they evoke. And with just cause: long feared for the devastation they could wreak, their very existence shaped the shipping routes used by the boats that sailed these waters.
There is news from the British Antarctic Survey that four out of five studied Emperor Penguin colonies in the Bellinghausen Sea lost the 2022 generation of chicks to melting sea ice. The mass mortality event was believed to have included over 10,000 chicks. The chicks could not survive the melting as they were too young to have grown waterproof feathers.
The news is too distressing for me, and I did not read it. I am confident I’m not alone in that choice. The Bellinghausen Sea had abnormally open waters this winter and is a neighbor to the vulnerable Amundsen Bay Sea that includes Thwaites and Pine Island glaciers. The fossil fuel industry killed the 2022 generation, wouldn’t you agree?
In a new study published today in Communications Earth & Environment, researchers from British Antarctic Survey discussed the high probability that no chicks had survived from four of the five known emperor penguin colonies in the central and eastern Bellingshausen Sea. The scientists examined satellite images that showed the loss of sea ice at breeding sites, well before chicks would have developed waterproof feathers.
But here is the absolute beauty of an Emperor Penguin colony formed by icebergs and an aurora. It is worth the watch.
