Larsen C Ice Shelf Melt In Focus; Even In Winter, Weight Of Meltwater, Warm Winds Do The Job
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Utrecht University writes:
Glacier researcher Peter Kuipers Munneke from Utrecht University’s (UU) climate institute IMAU was the leader of the study in which UU cooperated with several institutes from the UK and the US. Kuipers Munneke was surprised by the findings. “The meltwater lakes occur on the Larsen C ice sheet, a large floating glacier in the north of Antarctica, where a large iceberg broke off just last July. We hadn’t expected it to melt so much there in the winter, because it’s so dark there, and the sun provides absolutely no heat. Four years ago, we installed a weather station there to study why so much snow melts in the area. Unexpectedly, it’s due to the melting in the winter, which appears to be caused by the warm wind.”
Around once per week, an extremely warm, dry wind blows down from the mountains to the west of the ice sheet. This foehn wind can raise the temperature by 15 to 20 degrees in just a few hours. Kuipers Munneke: “All of the winter heat comes from the foehn wind, there is no other heat source this period of year. During a strong foehn, so much snow can melt that it forms huge lakes on the surface of the ice. We had known about these lakes during the summertime, but apparently 20 to 25 percent of the meltwater from the past few years actually occurs in the winter instead.”
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Thanks to the new radar images, the researchers can also see that the meltwater re-freezes over the course of the winter. Kuipers Munneke: “Both of the times, the lakes developed in May, the start of the Antarctic winter. Later in the season, the water re-froze, creating slabs of ice over those locations. Consequently, the meltwater doesn’t flow into the sea, so it doesn’t contribute to rising sea levels either.”
However, the discovery may have consequences in the future. “Over the past few decades, large floating glaciers have broken off from the Antarctic mainland. That was in some cases caused by the fact that large meltwater lakes had made some of the ice sheets unstable. We may be observing a process that might create meltwater lakes over a much larger area in the future. We expect that there will be many more winter melt days as time passes. Not only because global temperatures are rising, but also because a warmer world means a stronger westerly wind in the southern hemisphere. And that increases the foehn winds that cause winter melting in Antarctica.”
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https://www.dailykos.com/stories/2019/5/31/1850769/-Antarctica-s-fourth-largest-ice-shelf-susceptible-to-hydrofracture-and-collapse-from-winter-winds?utm_campaign=trending