Antarctica is dealing with a climatic tipping level by 2060 with a catastrophic soften until carbon emissions are lowered shortly – Watts Up With That?
The big wildcard for sea level rise is Antarctica. Photo credit Charles Rotter 1993
Julie Brigham-Grette, University of Massachusetts Amherst and Andrea Dutton, University of Wisconsin-Madison
While US Secretary of State Antony Blinken is raising awareness of climate change in the Arctic at meetings with other national officials in Iceland this week, an even greater threat looms on the other side of the planet.
New research shows that it is Antarctica that can force a settlement between today’s decisions by countries about greenhouse gas emissions and the future survival of their coasts and coastal cities from New York to Shanghai.
This reckoning can come much sooner than people realize.
The Arctic is losing ice as global temperatures rise. This has a direct impact on life and creates feedback loops that encourage warming. But the big wild card for sea level rise is Antarctica. There is enough land ice in it to raise global sea levels by more than 60 meters – roughly ten times the amount in the Greenland ice sheet – and we are already seeing signs of problems.
Scientists have long known that the Antarctic ice sheet has physical tipping points beyond which ice loss can spiral out of control. The new study, published in the journal Nature, finds that the Antarctic ice sheet could reach a critical turning point in a few decades, when today’s elementary school children raise their families.
The results mean that a general argument for not reducing greenhouse gas emissions now – that future technological advancement can save us later – is likely to fail.
A satellite image shows the long river lines as a glacier to the right carries ice into the Ross Ice Shelf in Antarctica. The red spots mark the bedrock. USGS
The new study shows that by around 2060, the Antarctic ice sheet crossed a critical threshold, pledging the world to sea level rise irreversible on human timescale if emissions persist at their current pace. If carbon dioxide is pulled out of the air at this point, ice loss will not stop, and by 2100 sea levels could rise more than ten times faster than today.
The turning point
In Antarctica there are several protective ice shelves that fan out into the ocean in front of the continent’s constantly flowing glaciers and slow the flow of glaciers on land to sea. But these shelves can thin and dissolve when warmer water gets under them.
When ice shelves break open, towering ice cliffs can be exposed that may not be able to stand on their own.
There are currently two possible instabilities. Portions of Antarctica’s ice sheet are grounded below sea level on bedrock that slopes inward toward the center of the continent, allowing warm seawater to eat its way around their lower edges, destabilizing them, and causing them to quickly retreat downhill. Above the water, surface melt and rain can open fractures in the ice.
If the ice cliffs get too high to support themselves, they can collapse catastrophically and accelerate the flow of ice to the ocean.
Using computer models based on the physics of the ice sheet, the study found that above 2 ° C, Antarctica will see a sharp increase in ice loss triggered by the rapid ice loss from the massive Thwaites Glacier. This glacier drains an area the size of Florida or Great Britain and is the focus of intense study by scientists from the USA and Great Britain.
To put this into context, the planet is on track to exceed 2 ° C warming under current country policies.
Other projections do not take into account the instability of the ice cliffs and generally come up with lower estimates for the rate of sea level rise. While much of the reporting after the new paper was released has focused on differences between these two approaches, both come to the same basic conclusions: the magnitude of sea level rise can be drastically reduced by meeting the goals of the Paris Agreement and physical instabilities in Antarctica Ice cover can lead to a rapid acceleration in sea level rise.
The disaster won’t stop in 2100
The new study, led by Robert DeConto, David Pollard, and Richard Alley, is one of the few looking beyond this century. One of us is a co-author.
It shows that sea level rise would explode if the high emissions from today continued unabated until 2100 and exceeded 6 cm per year by 2150. By 2300, sea levels would be ten times higher than expected if countries met the goals of the Paris Agreement. A warmer and softer ice sheet and a warming ocean that holds its heat for centuries prevent the protective ice shelves of the Antarctic from re-freezing and lead to a completely different world.
The vast majority of ways to meet the Paris Agreement assume that emissions will exceed their targets of keeping warming below 1.5 ° C or 2 ° C and then count on future technological advances to remove enough carbon dioxide from the Agreement to remove air later to lower the temperature again. The rest requires a 50% reduction in emissions worldwide by 2030.
While the majority of countries – including the US, UK and the European Union – have set this as a target, current global policies would only result in a 1% reduction by 2030.
It’s about reducing emissions quickly
Some other researchers suggest that the ice cliffs in Antarctica may not collapse as quickly as they did in Greenland. But what if, given their size and current rates of warming – far faster than the historical record – they collapse faster?
As countries prepare to step up their Paris Agreement pledges ahead of a United Nations meeting in November, Antarctica has three key messages that we as polar and ocean scientists want to highlight.
First, every fraction of a degree is important.
Second, letting global warming exceed 2C is not a realistic option for coastal communities or the global economy. The comforting prospect of technological fixes that will allow a later return to normal is an illusion that will leave the coasts beneath feet of water with devastating economic repercussions.
Third, today’s policies must be viewed in the long term, as they can have irreversible effects on Antarctica ice and the world. In the past few decades, the focus of rapid climate change has mainly been on the Arctic and its rich population of threatened indigenous cultures and ecosystems.
As scientists learn more about Antarctica, it becomes clear that this continent – without constant human presence – will determine the state of the planet on which today’s children and their children will live.
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Julie Brigham-Grette, Professor of Earth Sciences, University of Massachusetts Amherst and Andrea Dutton, Professor of Earth Sciences, University of Wisconsin-Madison
This article is republished by The Conversation under a Creative Commons license. Read the original article.
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