Friday, 16 June 2017

The Rains of Antarctica have arrived

Raining in the Antarctic

The Rains of Antarctica are Coming — Warm Summer Storms Melted Texas-Sized Section of Ross Ice Shelf Surface During 2016

In West Antarctica, we have a tug-of-war going on between the influence of El Niños and the westerly winds, and it looks like the El Niños are winning. It’s a pattern that is emerging. And because we expect stronger, more frequent El Niños in the future with a warming climate, we can expect more major surface melt events in West Antarctica (emphasis added).” 
— David Bromwhich, co-author of a recent study identifying massive summer surface melt in West Antarctica during 2016.

15 June, 2017
If you’re concerned about human-caused global warming, then you should also be concerned about ice. In particular — how warming might melt a miles-high pile of the frozen stuff covering the massive continent of Antarctica.
During recent years, scientists have become more and more worried as they’ve observed warming oceans eating away at the undersides of floating ice sheets. This particular process threatens numerous cities and coastal regions with swiftening sea level rise as ice margins melt and glaciers the size of mountain ranges clamor for release into the world’s oceans.
Major Antarctic Surface Melt Event During 2016

But another potential process in a still warmer world threatens to compound the impact of the heating waters that are already melting so many of the world’s glaciers from the bottom up — large scale surface melt.
(A major warming event during January of 2016 turned a Texas-sized section of Antarctica’s surface into slush. This occurred as a storm running in from the Southern Ocean delivered warm air and rainfall to sections of West Antarctica. Scientists are concerned that more major surface melt is on the way for Antarctica as the Earth’s climate heats up and that repeated warming and rainfall events in this typically-frozen region may further quicken rates of sea level rise. Image source: Earth Nullschool.)

During January of 2016, as a very strong El Nino was combining with human-caused global warming to spike atmospheric temperatures to 1.2 C above 1880s levels, something pretty strange and concerning happened. Over the course of about 15 days, a 300,000 square mile section of the Ross Ice Shelf surface and nearby lands over West Antarctica experienced melting. This mass slushing across Antarctica’s surface occurred as a warm storm swept in from the Southern Ocean (see image above) to deliver an unheard of rainfall event to the region.
West Antarctica is typically too cold for such weather. It is also often too dry. The region is well know by climate researchers as a frozen desert. But as human-forced climate change has warmed the nearby ocean, warm, moist winds blowing in from these heating waters have become more frequent.

Westerlies Interrupted by Warming Ocean

Antarctica is typically protected by strong westerly winds that keep both heat and moisture out. But a warming ocean environment, according to Ohio State researchers, is enabling El Nino to interrupt these westerlies and hurl increasing volumes of heat and moisture over the glaciers of Antarctica. In 2016, these winds bore with them an odd rainstorm that set off a massive surface melt event.

(Surface melt over a large section of West Antarctica lasted for as much as 15 days as heat and moisture from the surrounding ocean beat back a protective barrier of westerly winds and invaded the frozen continent. According to scientists, these events are likely to become more frequent and long-lasting as the climate warms. Image source: Ohio State University.)

When combined with already-active melt from ocean warming, surface melt could further serve to destabilize ice sheets and swiften sea level rise. This was exactly the concern that David Bromwich, an Antarctic researcher at Ohio State and co-author of the paper that identified this strange event highlighted in this statement (please see related Washington Post article here):
It provides us with a possible glimpse of the future. You probably have read these analyses of West Antarctica, many people think it’s slowly disintegrating right now, and it’s mostly thought to be from the warm water eating away at the bottom of critical ice shelves. Well, that’s today. In the future, we could see action at the surface of these ice shelves as well from surface melting. So that makes them potentially much more unstable (emphasis added).”

It’s worth noting that this particular storm, though unusual and noteworthy, did not produce too much in the way of surface melt ponding. Instead, the storm turned a large section of the Antarctic surface to a slurpee-like slush. But this event did deliver a considerable amount of heat to the Ross Ice Shelf region. And repeated instances could serve to seriously soften this massive ice formation.

Eventually, as warming worsens, significant surface melt and flooding could help to shatter large buttressing ice shelves like Ross or even generate risks of surface glacial outburst flooding in instances where permanent surface melt lakes form behind an ice dam. But the primary concern at this time is that these warm rain events provide a compounding melt influence that adds to risks for more rapid sea level rise this Century.

Hat tip to TodaysGuestIs

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