New research: accelerated melting in West Antarctica inevitable no matter how much emissions are cut

There’s been plenty of bad news from Antarctica in the past few years. Recent coverage here includes: 

In a new study published Monday in Nature Climate Change, the title just about says it all—Unavoidable future increase in West Antarctic ice-sheet melting over the twenty-first century. The researchers assessment is that the melting is locked in and chances are “dire” that this will produce colossal sea-level rise. If all the West Atlantic ice sheet completely melted, scientists calculate it would raise global sea levels by 5.3 meters (17.4 feet).

The study indicates that, even if the world were to meet its 1.5° Celsius (2.7° Fahrenheit) goal for global warming, the melting rate of the floating ice shelves of the Amundsen Sea will be three times what it was in the 20th Century. But there is still huge uncertainty about how fast sea level will rise as a consequence of those floating shelves breaking away from the ice sheet, thus allowing the land-based glaciers to flow into the sea faster.

Lead author Kaitlin Naughten at the British Antarctic Survey told The Guardian: “Our study is not great news—we may have lost control of west Antarctic ice shelf melting over the 21st century. It is one impact of climate change that we are probably just going to have to adapt to, and very likely this means some coastal communities will either have to build [defenses] or be abandoned.” 

Tiago Segabinazzi Dotto, at the UK National Oceanography Center, said: “It is likely that we [have] passed a tipping point to avoid the instability of the west Antarctic ice sheet. However, the pace of this collapse is still uncertain—it can happen in decades for some specific ice shelves or centuries. The conclusions of the work are based on a single model and need to be treated carefully.” But he said the study’s findings meshes with some findings of previous studies. “[This] gives confidence that this study needs to be taken in consideration for policymakers.”

From the study:

Previous modelling6 found that the Amundsen Sea probably warmed in response to atmospheric changes over the twentieth century, providing a viable explanation for WAIS [West Atlantic ice shelf] mass loss. Observations cannot be used to detect such a long-term ocean warming trend in this region, as data collection only began in 19947, and the warming trend exhibits strong decadal variability8. Regardless of the existence or magnitude of historical trends, if the Amundsen Sea experiences further warming over the twenty-first century, the outlook for the WAIS will only become more grave.

It has been hypothesized that Amundsen Sea warming will respond to future climate change and may be amenable to mitigation by reducing greenhouse gas emissions6,9,10. However, this hypothesis has not been adequately tested. Existing future projections of ice-shelf basal melting are generally not reliable in the Amundsen Sea, a region which is frequently biased cold or poorly resolved in the underlying ocean models11,12. Reference 13 produced the first future projections using a regional model of the Amundsen Sea, which simulated an increase in basal melting. However, this study only considered a single forcing scenario, the worst-case scenario of extreme fossil fuel use, and did not account for internal climate variability.

Temperature is averaged over the depth range 200–700 m. Trends are calculated at each point using annually averaged fields from 2006–2100. White regions indicate no significant trend. The Amundsen Sea region visualized here (latitude–longitude projection) is outlined in red in the inset map of Antarctica (polar stereographic projection). The black dashed line shows the 1,750 m depth contour of the continental shelf break and the blue dashed line outlines the continental shelf region used for analysis. Labels denote ice shelves (G, Getz; D, Dotson; Cr, Crosson; T, Thwaites; P, Pine Island; Co, Cosgrove; A, Abbot).

Definitely not good news, but not really surprising in light of other recent news about what so far is still the frozen continent. Naughten said, “The question of doom and gloom is something I’ve spent a lot of time thinking about with this study, because how do you tell such a bad news story?  Conventional wisdom is supposed to give people hope, and I don’t see a lot of hope in this story,” she added, “but it’s what the science tells me and it’s what I have to communicate to the world.” Nonetheless, she added, “we shouldn’t give up [on climate action] because even if this particular impact is unavoidable, it is only one impact of climate change. Our actions likely will make a difference [to Antarctic ice melting] in the 22nd century and beyond, but that’s a timescale that probably none of us today will be around to see.” 

At the University of Colorado Boulder, glacialogist Ted Scambos, who was not involved with the study, called the findings “sobering.” He told CNN, “The thing that’s depressing is the committed nature of sea level rise, particularly for the next century. People who are alive today are going to see a significant increase in the rate of sea level rise in all the coastal cities around the world.”

And he gave a scientific voice to the many people around the world demanding that we stop extracting and burning the fossil fuels that are at the root of the West Antarctic’s melting. Not only do we have to stop adding to that atmospheric carbon burden, he said, but “remove some that has already built up,” something he concedes will be “a real challenge.” That is true both technically, and unfortunately, politically. 

Previous ArticleNext Article