The Weekend Wonk: Jamin Greenbaum on East Antarctica

May 20, 2016

Scientist Jamin Greenbaum was in the news again this week as the Washington Post, among others, carried news of his recent study deepening understanding of melting in remote East Antarctica.

Readers of this blog will know Jamin from Interviews I conducted more than a year ago, so useful to review. One more example of why regular visitors here know the players and the playbook well ahead of the mainstream media. Worth supporting.

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To summarize, West Antarctica is well known to be melting and moving rapidly towards the sea – but less has been said about vast East Antarctica, for the most part because it has not been as accessible and well studied. Now the veil is being penetrated, and the news is unsettling.

Greg Laden’s Blog covers this week’s new research:

Here is the abstract:

Climate variations cause ice sheets to retreat and advance, raising or lowering sea level by metres to decametres. The basic relationship is unambiguous, but the timing, magnitude and sources of sea-level change remain unclear; in particular, the contribution of the East Antarctic Ice Sheet (EAIS) is ill defined, restricting our appreciation of potential future change. Several lines of evidence suggest possible collapse of the Totten Glacier into interior basins during past warm periods, most notably the Pliocene epoch, … causing several metres of sea-level rise. However, the structure and long-term evolution of the ice sheet in this region have been understood insufficiently to constrain past ice-sheet extents.

Here we show that deep ice-sheet erosion—enough to expose basement rocks—has occurred in two regions: the head of the Totten Glacier, within 150 kilometres of today’s grounding line; and deep within the Sabrina Subglacial Basin, 350–550 kilometres from this grounding line. Our results, based on ICECAP aerogeophysical data, demarcate the marginal zones of two distinct quasi-stable EAIS configurations, corresponding to the ‘modern-scale’ ice sheet (with a marginal zone near the present ice-sheet margin) and the retreated ice sheet (with the marginal zone located far inland). The transitional region of 200–250 kilometres in width is less eroded, suggesting shorter-lived exposure to eroding conditions during repeated retreat–advance events, which are probably driven by ocean-forced instabilities. Representative ice-sheet models indicate that the global sea-level increase resulting from retreat in this sector can be up to 0.9 metres in the modern-scale configuration, and exceeds 2 metres in the retreated configuration.

Chris Mooney has written up a detailed description of the research including information gleaned from interviews with the researchers, and you can read that here. In that writeup, Chris notes:

Scientists believe that Totten Glacier has collapsed, and ice has retreated deep into the inland Sabrina and Aurora subglacial basins, numerous times since the original formation of the Antarctic ice sheet over 30 million years ago. In particular, they believe one of these retreats could have happened during the middle Pliocene epoch, some 3 million years ago, when seas are believed to have been 10 or more meters higher (over 30 feet) than they are now.

“This paper presents solid evidence that there has been rapid retreat here in the past, in fact, throughout the history of the ice sheet,” Greenbaum says. “And because of that, we can say it’s likely to happen again in the future, and there will be substantial sea level implications if it happens again.”

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