Seen from space, Antarctica looks so much simpler than the other continents\u2014a great sheet of ice set in contrast to the dark waters of the encircling Southern Ocean. Get closer, though, and you\u2019ll find not a simple cap of frozen water, but an extraordinarily complex interplay between the ocean, sea ice, and ice sheets and shelves.<\/p>\n
That relationship is in serious peril. A new paper<\/a> in the journal Nature catalogs how several \u201cabrupt changes,\u201d like the precipitous loss of sea ice over the last decade, are unfolding in Antarctica and its surrounding waters, reinforcing one another and threatening to send the continent past the point of no return\u2014and flood coastal cities everywhere as the sea rises several feet.<\/p>\n \u2018Global consequences\u2019 <\/p>\n \u201cWe\u2019re seeing a whole range of abrupt and surprising changes developing across Antarctica, but these aren\u2019t happening in isolation,\u201d said climate scientist Nerilie Abram, lead author of the paper. (She conducted the research while at Australian National University but is now chief scientist at the Australian Antarctic Division.) \u201cWhen we change one part of the system, that has knock-on effects that worsen the changes in other parts of the system. And we\u2019re talking about changes that also have global consequences.\u201d<\/p>\n Scientists define abrupt change as a bit of the environment changing much faster than expected. In Antarctica these can occur on a range of time scales, from days or weeks for an ice shelf collapse to centuries and beyond for the ice sheets. Unfortunately, these abrupt changes can self-perpetuate and become unstoppable as humans continue to warm the planet. \u201cIt\u2019s the choices that we\u2019re making right now, and this decade and the next, for greenhouse gas emissions that will set in place those commitments to long-term change,\u201d Abram said.<\/p>\n Warning signs <\/p>\n A major driver of Antarctica\u2019s cascading crises is the loss of floating sea ice, which forms during winter. In 2014, it hit a peak extent (at least since satellite observations began in 1978) around Antarctica of 20.11 million square kilometers, or 7.76 million square miles. But since then, the coverage of sea ice has fallen not just precipitously but almost unbelievably, contracting by 75 miles closer to the coast. During winters, when sea ice reaches its maximum coverage, it has declined 4.4 times faster around Antarctica than it has in the Arctic in the last decade.<\/p>\n Put another way: The loss of winter sea ice in Antarctica over just the past decade is similar to what the Arctic has lost over the last 46 years. \u201cPeople always thought the Antarctic was not changing compared to the Arctic, and I think now we\u2019re seeing signs that that\u2019s no longer the case,\u201d said climatologist Ryan Fogt, who studies Antarctica at Ohio University but wasn\u2019t involved in the new paper. \u201cWe\u2019re seeing just as rapid\u2014and in many cases, more rapid\u2014change in the Antarctic than the Arctic lately.\u201d<\/p>\n While scientists need to collect more data to determine if this is the beginning of a fundamental shift in Antarctica, the signals so far are ominous. \u201cWe\u2019re starting to see the pieces of the picture begin to emerge that we very well might be in this new state of dramatic loss of Antarctic sea ice,\u201d said Zachary M. Labe, a climate scientist who studies the region at the research group Climate Central, which wasn\u2019t involved in the new paper.<\/p>\n This extraordinary decline is kicking off a climatic feedback loop. The Arctic is warming around four times faster than the rest of the planet in large part because its reflectivity is changing. Sea ice is white and bright, so it bounces the sun\u2019s energy back into space to cool the region. But when it disappears, it exposes darker ocean waters, which absorb that energy. So less reflectivity begets more warming, and more warming melts more sea ice, which begets more warming, and on and on. \u201cWe now expect that that same process is going to become a factor in the Southern Hemisphere, because we\u2019ve lost this equivalent amount of sea ice,\u201d Abram said.<\/p>\n Bigger and irreversible consequences <\/p>\n Around Antarctica, however, the consequences could be even bigger and more complex than in the Arctic and might even be irreversible. Models predict that if the global climate were to stabilize, so too would Arctic sea ice. \u201cWe don\u2019t see that same behavior in Antarctica,\u201d Abram said. \u201cWhen you stabilize the climate and let these climate model simulations run for hundreds of years, Antarctic sea ice still continues to decline because the Southern Ocean is continuing to take up extra heat from the atmosphere.\u201d<\/p>\n This could spell major trouble for the continent\u2019s enormous cap of ice. That consists of two main parts: the ice sheets, which rest on land, and the ice shelves, which extend from the sheets and float on the sea. The problem isn\u2019t so much about the sun beating down on the sheets, but increasingly warm water lapping at the bottom of the shelves. And the more the surrounding sea ice disappears, the more those waters are warming. Additionally, sea ice acts as a sort of shield, absorbing wave energy that would normally pound these edges of the ice shelves, breaking them apart.<\/p>\n So sea ice supports the ice shelves, which support the ice sheets on land. \u201cWhen we melt ice shelves, they have a buttressing effect on the ice sheets behind them, so we get an enhanced flow of ice sheets into the ocean,\u201d said Matthew England, an oceanographer at the University of New South Wales and coauthor of the paper. One of these, the West Antarctic Ice Sheet, could collapse if global temperatures reach 2 degrees Celsius above pre-industrial levels, raising sea levels by more than three meters, or about 10 feet. And it could still partially collapse before that.<\/p>\n As ice shelves melt, they\u2019re also borking a critical ocean system known as the Antarctic Overturning Circulation. When sea ice forms, it rejects salt, creating salty, extra cold seawater that\u2019s denser and therefore sinks to the seafloor, creating circulation. But as ice shelves melt, they dilute the cold salty water, slowing the circulation and bringing more warm water in contact with ice shelves and sea ice. \u201cThis amplifying feedback that we\u2019re talking about now is across systems,\u201d England said. \u201cIt\u2019s from the ocean back to the ice, and then back into the ocean again, that can trigger a runaway change where we do see the overturning potentially collapse altogether.\u201d<\/p>\n When this circulation brings deeper waters back to the surface, it transports critical nutrients for phytoplankton\u2014tiny photosynthetic organisms that absorb carbon and expel oxygen. Not only are these organisms responsible for sequestering half of the carbon from photosynthesis worldwide<\/a>, but they also make up the base of the food web, feeding small animals known as zooplankton, which in turn feed bigger organisms like fishes and crustaceans. Sea ice is also a critical habitat for phytoplankton, so they stand to lose both their home and their nutrients.<\/p>\n A chronic sickness for the far south <\/p>\n Emperor penguins, too, establish their breeding colonies on stable sea ice, where their chicks grow up and develop the waterproof feathers they need to glide through the ocean. \u201cThat ice is being lost before the emperor penguins have been able to fledge, and when that happens, you have a complete breeding failure for the colony in that season,\u201d Abram said. \u201cWe\u2019re seeing those catastrophic breeding failure events happening right around the Antarctic continent.\u201d<\/p>\n The relentless warming of Antarctica and its surrounding waters is a long-term trend\u2014a sort of chronic sickness for the far south. But it\u2019s being accentuated by acute attacks, like a freak heat wave in East Antarctica in March 2022 that spiked temperatures 40 degrees C (72 degrees F) above normal, obliterating records and shocking scientists<\/a>. \u201cBecause of just the intensity of that extreme event,\u201d Fogt said, \u201cit can take places that are slightly vulnerable and push them over a tipping point where they\u2019re no longer going to be able to recover, at least not for a long, long time.\u201d<\/p>\n The bit of good news, though, is that year by year, researchers are getting ever more data about how Antarctica is responding to human-caused climate change, allowing them to more accurately model what might happen in the decades ahead. And scientists know full well how to treat the continent\u2019s chronic disease: Immediately and massively cut greenhouse gas emissions \u2014 or face the consequences. \u201cEvery fraction of a degree of warming that we can save stacks the odds of avoiding these catastrophic changes,\u201d England said. \u201cSea-level rises of multiple meters mean global political instability that will dwarf what we\u2019re seeing right now.\u201d<\/p>\n This article originally appeared in Grist<\/a> at https:\/\/grist.org\/climate\/antarctica-is-in-extreme-peril\/<\/a>. Grist is a nonprofit, independent media organization dedicated to telling stories of climate solutions and a just future. Learn more at Grist.org<\/a>.<\/p>\n","protected":false},"excerpt":{"rendered":"Seen from space, Antarctica looks so much simpler than the other continents\u2014a great sheet of ice set in…\n","protected":false},"author":2,"featured_media":119339,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[32],"tags":[9348,2351,6733,6876,79],"class_list":{"0":"post-119338","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","7":"category-science","8":"tag-antarctica","9":"tag-ecology","10":"tag-global-warming","11":"tag-melting-ice","12":"tag-science"},"_links":{"self":[{"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/posts\/119338","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/comments?post=119338"}],"version-history":[{"count":0,"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/posts\/119338\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/media\/119339"}],"wp:attachment":[{"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/media?parent=119338"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/categories?post=119338"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/tags?post=119338"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}