One thing is clear: the future of a frozen ocean in a warming world is increasingly uncertain. Dr Will Hobbs, Physical Oceanographer and sea ice researcher for the Australian Antarctic Program Partnership (AAPP) at the University of Tasmania
It's the ocean's stupid. Antarctic sea ice around the frozen continent has dropped to a scary low for the third year in a row per the US National Snow and Ice Data Center.
The sea ice was again below 2 million square kilometers, which The Guardian noted had never been breached until 2022 since satellite records began.
From the Australian Antarctic Program Partnership (AAPP): Good things don't come in threes for Antarctic sea ice.
Lead author Dr Will Hobbs, of the Australian Antarctic Program Partnership (AAPP) at the University of Tasmania, said a ‘regime shift’ is an abrupt change in the behaviour of a system.
“The extreme lows in Antarctic sea ice have led researchers to suggest that a regime shift is under way in the Southern Ocean, and we found multiple lines of evidence that support such a shift to a new sea-ice state.”
“We explored whether a significant change in sea-ice variability has led to more extreme sea-ice events over the last decade or so, and whether that’s because of a changed response to the atmosphere or the ocean,” Dr Hobbs said.
“We found that the variability of Antarctic sea ice, and how long the anomalies last, has increased significantly since 2006.”
“Perhaps the most striking change for scientists is that while the atmosphere has always been the main driver of Antarctic sea-ice variability, the recent extreme fluctuations over the last decade can’t be explained by the atmosphere alone.”
“AAPP research shows that the changes we’re seeing – how much the sea ice can shift from its average state, and how long those shifts can stick around – are controlled by ocean processes. This is more evidence that ocean changes are probably the secret to what’s happened in recent years,” he said.
The warming ocean damages the sea ice and the world's climate.
New research flags an alarming shift in the ocean's coldest, deepest water. Learn what the impact is on the ocean's ecosystem from Discovery Magazine.
To model circulation strength at unthinkable depths, England’s team relied on direct observations of temperature, as well as vital measurements taken by the larger oceanographic community. These included oxygen levels recorded across ocean strata, and even measurements taken from transducers strapped to elephant seals — a technique used to get as close to the ice shelf as possible.
“They made a model that created Antarctic Bottom Water in a realistic way, and nobody else had understood that,” says Spencer Jones, a physical oceanographer at Texas A&M University who was not involved in the study.
Using data at an incredibly fine scale, the landmark research is consistent with circulation slowdowns projected in recent Intergovernmental Panel on Climate Change reports, and exposed how the melting ice shelf, specifically, is driving this change.
England says getting his team’s experiment right also took a bit of luck. Avoiding its predictions, however, will require deliberate action. “We’re probably halfway into the slowdown we projected,” he says. “It’s a tough ship to turn around, but with dramatic emissions reductions, we can save it from a full collapse.”
Such a breakdown hasn’t happened for more than 100,000 years, since at least the last interglacial period. And it would be devastating. Changes we already endure — collapsing marine ecosystems, strengthening cyclones, smothering heat waves, bleaching coral reefs, and calamitous sea level rise — would only intensify. In July, a team from Denmark revealed how similar warming in northern seas is on pace to stall the AABW’s Atlantic sister current by midcentury.
Let's begin with the sea ice. Each winter, the ocean water around Antarctica freezes. Because Antarctica is in the Southern Hemisphere, this happens during North American summer months – deep winter in Antarctica is in July, August, and September.
Disappearing sea ice is a problem for lots of reasons. While it doesn't directly add any extra water to the ocean, missing sea ice does contribute to global sea level rise in other ways. The sea ice around Antarctica shields glaciers on land, and massive ice shelves that extend out into the water, from storms and above-freezing ocean water. Without that protection, that ice can melt more quickly, and that leads to more sea level rise.
And it's difficult for sea ice to recover after a bad year like this one. The water that doesn't freeze — the exposed ocean water — absorbs more heat than ice does, and that makes it more difficult for ice to re-form the next year.
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And when the authors used a computer to simulate what would happen if humans immediately slashed greenhouse gas emissions, they found it would have basically no effect on the rate of melting in West Antarctica for the rest of the century.
"It appears that we may have lost control of the West Antarctic ice shelf melting over the 21st century," says Kaitlin Naughten of the British Antarctic Survey and one of the authors of the study. "Our actions today likely will make a difference further down the line, in the 22nd century and beyond, but that's a time scale that probably none of us here will be around to see."
The 2023 large-scale drivers of the lowest recorded sea ice extent in satellite records. 2024 was the second-lowest sea ice extent on record.
The year 2023 marked a turning point for the Antarctic region as the Southern Hemisphere experienced a significant reduction in its sea ice extent, with a record-breaking sea ice minimum in July 2023 of approximately 2.4 million square kilometers below the long-term average. This study highlights the drivers behind this exceptional event by combining observational, satellite, and reanalysis data, with a special focus on the large-scale atmospheric circulation. Throughout the year, the Antarctic Sea ice extent broke record after record, ranking as the lowest sea ice on record from January to October, except for March and April. The exceptionally low sea ice extent from May to August was mainly driven by the prevalence of a zonal wave number 3 pattern, characterized by alternating surface high- and low-pressure systems, which favored the advection of heat and moisture, especially over the Ross Sea (RS), Weddell Sea (WS), and Indian Ocean (IO). The anomalous large-scale circulation was accompanied by record-high sea surface and subsurface temperatures over the regions with reduced sea ice extent. In addition to the air and ocean temperature, record-breaking heat, moisture, and sensible heat fluxes have been observed, especially over the WS, RS, and IO, which further amplified the reduction in the sea ice extent over these areas. Notably, over the Weddell Sea, we observed air temperature anomalies reaching up to 8°C and sea surface temperature anomalies of up to 3°C from May to July. Similar temperature anomalies were recorded over the Ross Sea, particularly in July and August. A change point analysis indicates that a regime shift in the Antarctic Sea ice, as well as in the average mean air temperature and (sub)surface ocean temperature over the Weddell Sea, started around 2015. The low sea ice extent in Antarctica in 2023 was a stark reminder of the ongoing changes in the polar regions. Thus, understanding the underlying mechanisms of these extreme events provides crucial insights into the changing dynamics of Antarctic Sea ice and its broader climatic significance.
Thwaite's tongue is crumbling but has not collapsed or had a major calving in years. It was a melange, icebergs, and sea ice cemented together that provided resistance that collapsed. parts of the western and eastern ice shelves occurring over the past few days. This video of the ice stream tongue is from 2017-2019.
The British Antarctic Survey has wrapped up its 2024 field season. They say they have collected an abundance of information on Thwaites. We’ll have to wait for their well-done public announcements.
Sorry to be so prolific on Antarctica, but fast-moving dangerous fuckery is happening, and I would like to keep on top of it. We can't count on the ice situation improving anytime soon.