An area larger than the state of Texas in West Antarctica melted to an unusual degree last year, with pools of the meltwater remaining on the surface for as long as 15 days. That’s trouble, since meltwater can accelerate the thawing already occurring from warming ocean temperatures. West Antarctica alone could contribute 10 feet of sea level rise, according to a 2009 paper published in Science.
This area in the Ross Ice Shelf, the world’s largest chunk of floating ice, likely melted at its surface because of a particularly strong 2015–2016 El Niño event, which brought warm and moist sea air to the area, according to the study published today in Nature Communications. El Niños have caused melting atop the Ross Ice Shelf before, but this time it lasted unusually long, according to the paper. It appears it also rained on the ice shelf and other parts of West Antarctica. That could made it easier for the snow surface to melt.
Antarctica is the coldest place on the planet — and though rain sometimes happens on the coasts, where it’s warmer, rainfall is a pretty striking event. “The story of melt all over the ice shelf rattled through the science community as it happened,” Robin Bell, an Antarctic researcher at the Lamont-Doherty Earth Institute at Columbia University, who was not involved in the study, told The Washington Post. “Who had heard of rain in Antarctica — it is a desert!”
The presence of meltwater worries scientists because it might make it more likely that the ice shelf will fracture. That could eventually lead to chunks of ice breaking off — bad news for us pitiable humans, since this ice shelf keeps other ground-based ice from flowing into the sea. Without this natural barrier, sea levels could rise several feet, spelling doom for many coastal areas.
There’s already evidence that warmer ocean water is melting West Antarctic ice shelves from beneath. But this paper shows that melting is causing pressure from the top, too. It also foreshadows a pretty bleak future for the ice continent — and for other continents, too. The number of extreme El Niño events is projected to increase in the future, the study says. If the melting event described in today’s paper is a taste of what’s to come, we can expect more frequent, extended melting of the West Antarctica ice sheet. That will almost certainly mean higher seas.