There has been yet another terrifying event that has been documented regarding the melting of the sleeping ice giant we know as Antarctica. Large scale surface melting of an Antarctica ice shelf that is 2 miles thick has “rattled scientists” because Antarctica is blistering cold and surface melt has not been a near term contributor to sea level rise. The collapse of the Antarctica ice shelves was expected to be due to warming ocean waters that have been carving into the ice from below weakening the shelf. But large scale melting on the surface was brought about by hot weather last summer. This is one of the first documented cases of widespread surface melting.
The loss of any ice shelf by itself will not raise sea levels, but the shelves buttress the massive inland glaciers from flowing into the sea (see image above).
What he saw during the melting event was an area of roughly 300,000 square miles, including most of the Ross Ice Shelf, that likely contained a mix of snow and water.
"What probably happened is that the surface snowpack was able to contain the meltwater, acting as a buffer and preventing the formation of melt ponds and streams that can be common on some Antarctic ice shelves," Nicolas said, "but we cannot rule out the presence of standing water in many locations."
What makes this event particularly interesting to scientists is that it took place during one of the strongest El Nino events on record.
"This conjunction of events was no coincidence," he said.
During an El Nino, warm waters from the equatorial Pacific Ocean move east. El Ninos also favor weather patterns that steer warm air towards West Antarctica, but strong westerly winds that blow over the ocean to the north of the continent usually keep the warmer air at bay.
BPCRC senior research associate Aaron Wilson, also a coauthor on the study, used climate models to show that melt events in West Antarctica are more likely to occur during El Nino conditions, especially when westerly winds are weak. What makes this January 2016 event unique, he explained, is that the warming occurred despite strong westerly winds.
An area twice the size of California was partially melted when warm winds from an especially strong El Niño blew over western Antarctica for more than two weeks in January 2016. Satellite data showed a mix of melted snow and ice over most of the Ross Ice Shelf, which covers an area the size of France and is the largest floating ice shelf in the world.
More frequent melting would accelerate the general deterioration of the West Antarctic Ice Sheet, which is located to the west of the Ross Ice Shelf, explained David Bromwich of Ohio State team, co-author of a paper on the findings in Nature Communications. “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,” he cautioned.
Researchers have documented that the West Antarctic Ice Sheet is melting from below because of warming ocean waters. But the January 2016 melt event affected the surface of large areas of western Antarctica, which could mean that a major portion of Antarctica’s vast ice sheet — which holds 90 percent of the world’s ice — will experience intensified melting from the air above and the sea below.
Chris Mooney at the Washington Post writes:
The resulting observations, from the satellites, suggest not that the Ross Ice Shelf was covered with lakes or pools, but rather, that liquid water mixed into the snow atop it.
“In some parts it could be slush for example, a mixture of ice and liquid water,” said Bromwich.
The melting occurred during a strong El Niño event, which are known to bring added warmth to West Antarctica. Several other past melt events atop the Ross Ice Shelf have also coincided with El Niños.
In this case, the event brought moist air in from the ocean. The researchers report in their study that there even appears to have been rainfall atop the Ross Ice Shelf, and other parts of West Antarctica, a striking occurrence.
“The story of melt all over the ice shelf rattled through the science community as it happened,” said Robin Bell, an Antarctic researcher at the Lamont-Doherty Earth Institute at Columbia University who was not involved in the study. “Who had heard of rain in Antarctica - it is a desert!”
Sorry to be the bearer of such bad news. Peace to all.