Extensive snowmelt in West Antarctica caused due to strong El Nino


Scientists have found evidence of widespread snowmelt in West Antarctica and this they say occurred due to especially strong El Nino blew over the continent.

An international team of scientists reveal in their study published in Nature Communications how an area of West Antarctica more than twice the size of California partially melted in 2016 as a result of unusually warm summer. One of the primary reasons behind the widespread melt is thought to be the warm spell that persisted for more than two weeks in January 2016.

Scientists have found evidence in satellite data that hint at a mix of melted snow and ice over most of the Ross Ice Shelf – a thick platform of floating ice that channels about a third of the ice flowing from the West Antarctic Ice Sheet into the ocean. This is the first time ever, scientists have been able to document how warm air could also cause widespread melting from above.

As it happens, researchers had installed the necessary instruments to investigate these processes in West Antarctica only a few weeks earlier, as part of a study to better understand how clouds affect the amount of energy that reaches the snow surface and influence its temperature.

Julien Nicolas, lead author of the paper, got a January 2016 alert from the AWARE expedition that the weather at their campsite atop of the West Antarctic Ice Sheet had turned unseasonably warm. Upon checking to see in the satellite data what was happening to the rest of West Antarctica, he saw 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.”

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.

“Without the strong westerlies, it’s likely there would have been much more melting,” Wilson said.


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