Autumn melting could be a warning sign
Lauren Dauphin/NASA Earth Observatory
Turquoise pools of snowmelt on the Antarctic Peninsula, including on the Larsen C ice shelf, have recently been forming months after the continent’s peak summer melt. Bursts of warm, dry wind cascading over mountains that run along the peninsula are largely to blame, researchers report April 11 in Geophysical Research Letters. In this March 2016 satellite image, meltwater on part of Larsen C can be seen at the foothills of these mountains, just one case of this type of wind-induced melting.
Eastward-flowing winds sweeping across the Antarctic Peninsula sometimes pick up enough speed to surmount its mountain peaks. As the air rises and chills, its moisture condenses and, in the process, reheats the air. So when the now-dry air comes coursing down the leeway mountainside, it can be a balmy 20° Celsius.
Researchers “have told me they’ve been in a T-shirt” while standing in these winds, says cryospheric scientist Tri Datta of NASA Goddard Space Flight Center in Greenbelt, Md.
Datta and her team compared satellite data collected from 1982 to 2017 with simulations of the peninsula’s ice sheet and atmospheric conditions during the same period. The team found that, since 2015, these winds called foehns have caused a lot of melting on the peninsula, including on Larsen C, as late as May, well into Antarctica’s autumn. Foehns likely cause 60 percent of the total snowmelt on the northeastern part of the peninsula at that time of year, Datta says.
That’s a problem because meltwater can trickle into crevasses on Larsen C. The water’s own weight wedges the cracks open and may help cause the ice shelf to break off. Late melting can also prevent new snow from replenishing the ice shelf. In 2017, a giant iceberg broke from Larsen C, raising questions about the shelf’s stability and how it may contribute to rising seas (SN: 8/5/17, p. 6).
It’s still unclear what’s driving these foehns and if they’re linked to climate change. And Datta emphasizes that three years is too short to constitute a trend. But without Larsen C, which buttresses multiple glaciers, glacial ice flow to the ocean could accelerate and contribute to rising global sea levels.
R. Datta et al. The effect of Foehn-induced surface melt on firn evolution over the northeast Antarctic peninsula. Geophysical Research Letters. Published online April 11, 2019. doi:10.1029/2018GL080845.
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