Dazzling blue lakes are forming in Antarctica — and they’ve got scientists worried
By Chris Mooney
HANDOUT PHOTO: Satellite image shows a group of lakes atop Langhovde Glacier, East Antarctica. (Satellite image courtesy of DigitalGlobe, Inc.)
More specifically, the satellite-based study found that atop the coastal Langhovde Glacier in East Antarctica’s Dronning Maud Land, large numbers of “supraglacial” or meltwater lakes have been forming — nearly 8,000 of them in summer between the year 2000 and 2013. Moreover, in some cases, just as in Greenland, these lakes appear to have then been draining down into the floating parts of the glacier, potentially weakening it and making it more likely to fracture and break apart.
When it comes to East Antarctica, however, “that’s the part of the continent where people have for quite a long time assumed that it’s relatively stable, there’s not a huge amount of change, it’s very, very cold, and so, it’s only very recently that the first supraglacial lakes, on top of the ice, were identified,” said Stewart Jamieson, a glaciologist at Durham University in the U.K. and one of the study’s authors.
The research raises concern, for the following reason: Mounting evidence suggests one reason that Greenland has been melting so fast lately is precisely these kinds of lakes. In the summer as air temperatures warm, lakes form on top of the ice sheet, and on its finger-like glaciers that extend outwards into deep ocean fjords.
In the new study, Langley and her colleagues find large numbers of lakes forming atop Langhovde Glacier, both inland from, and outward from, the so-called “grounding line,” which is where the marine glacier touches the seafloor far below the ice surface. Past the grounding line, the glacier’s ice begins to float and forms an ice shelf, extending out across the surface of the ocean.
The occurrence of these lakes was strongly related to surface air temperatures — they formed when temperatures rose above zero Celsius, or, above freezing, and formed most frequently in the summer of 2012-2013, which saw 37 days with temperatures above the freezing point.
“What we find is that the appearance of these lakes, unsurprisingly, is correlated directly with the air temperature in the region, and so the maximum number of lakes, and the total area of the lakes, as well as the depth of the lakes, all of these things peak when the air temperatures peak,” said Jamieson.
This raises the concern that these events could possibly be weakening the ice shelf by widening or exploiting fractures within it. But Jamieson said the study could not prove that, in part because it is much harder to observe the consequences of lake draining events in Antarctica than it is in Greenland.
When glaciers lose large parts of their ice shelves, they become less stable and flow faster towards the ocean, contributing to an increased rate of global sea level rise.
“The size of the lakes … are probably not big enough to do much at present, but if climate warming continues in the future, we can only expect the size and number of these lakes to increase. So that’s what we’re looking at,” Jamieson said.
He added that the mid-sized Langhovde Glacier is not special when it comes to East Antarctic meltwater lakes — other parts of coastal Antarctica see them too. The reason the study focused on Langhovde is simply that there was a lot of satellite and temperature data available.
In Greenland, when meltwater from the ice sheet’s surface flows out from beneath glaciers and enters the sea, it often takes with it sediment from the glacier bedrock, washing it out as well. This leads to the appearance of what are called “meltwater plumes” in the ocean near glaciers, areas of water with significantly different coloration due to high levels of sediment concentration.
So far, such plumes have not been observed around East Antarctica, Jamieson said.
Still, the lakes, and especially the apparent drainage events, raise a distinct worry about the future of Antarctica, which contains vastly more ice than Greenland and which, thus far, has not been losing nearly as much. “The parallels between these mechanisms, and those observed on Greenland/the Antarctic Peninsula, suggest that lakes may similarly affect rates and patterns of ice melt, ice flow and ice shelf disintegration in East Antarctica,” the study concludes.
Richard Alley, a glaciologist at Penn State who was not involved in the study, noted in an email comment that seeing some Antarctic surface melt is not too surprising. “Across many sensors and studies, there is summertime melting on the surface of Antarctica around the edges, and sometimes in some places extending farther inland than you might think,” he said.
For now, scientists plan to use the instruments available — mainly, at the moment, satellites — to further study the Antarctic lakes.
“It’s not hitting the glacier really hard at the moment, this process, but of course, as things warm up, we’d expect it to start doing more damage, like we see in Greenland,” said Jamieson.
Here is some hopeful researc on methane – hopeful, that is, if you see things isolation, rather than take a system approach
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