Beautiful and Ominous: Lakes Developing in East Antarctica
August 22, 2016
Something strange is happening to one of the coldest places on Earth. Dazzling blue lakes are blooming like summer wildflowers atop the East Antarctic ice sheet’s Langhovde Glacier. And that’s got scientists worried—because they’ve seen these lakes before.
“Supraglacial lakes”—meltwater ponds that form as warm summer air heats the surface of an ice sheet—have been spreading across Greenland for years. They’re both a sign of global warming and a cause of ice sheet collapse: as meltwater from the lakes drains into the underlying ice, it can lubricate the ice sheet’s foundation, causing it to weaken. This feedback is thought to be one of the reasons Greenland is now melting at an accelerating rate. (Earth’s northernmost ice sheet shed roughly a trillion tons between 2011 and 2014.)
Now, the lakes have jumped to the other end of the world, peppering an ice sheet that’s enjoyed relative stability compared with its overheated neighbor to the north. A new study in Geophysical Research Letters drew on satellite and meteorological data to construct the first long-term record of meltwater ponds along the coast of East Antarctica. According to the authors’ analysis, nearly 8,000 dazzling blue lakes appeared on the Langhovde Glacier in the summertime between 2000 and 2013.
Here, Dark Snow Project chief scientist Jason Box discusses the role this kind of lake plays on the Greenland sheet.
As in Greenland, many of these ephemeral lakes appear to be draining their contents into the underlying ice. It’s the first time this behavior has been observed in East Antarctica, a place that study co-author Stewart Jamieson, describes as “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.”
The presence of the lakes is, unsurprisingly, tied directly to temperature, with the greatest number of lakes forming in the unusually warm summer of 2012-2013.
It’s a bit early to say whether East Antarctica’s fresh summer look is going to mean trouble in the long-term. “We do not think that the lakes on Langhovde Glacier are at present affecting the glacier, but it will be important to monitor these in the future to see how they evolve with surface air temperature changes,” lead study author Emily Langley told Gizmodo in an email.
Indeed, the prospect of more lakes and larger lakes is worrisome, because Antarctica contains much more ice than Greenland, enough to raise global sea levels hundreds of feet if it all decided to melt. Recent studies suggest that parts of this icy fortress—particularly the West Antarctic ice sheet—could be far more sensitive to a few degrees of warming than we had hoped.
Supraglacial lakes are known to influence ice melt and ice flow on the Greenland ice sheet and potentially cause ice shelf disintegration on the Antarctic Peninsula. In East Antarctica, however, our understanding of their behaviour and impact is more limited. Using >150 optical satellite images and meteorological records from 2000-2013, we provide the first multi-year analysis of lake evolution on Langhovde Glacier, Dronning Maud Land (69°11’S, 39°32’E). We observe 7,990 lakes and 855 surface channels up to 18.1 km inland (~ 670 m a.s.l.) from the grounding line, and document three pathways of lake demise: (i) refreezing, (ii) drainage to the en-/sub-glacial environment (on the floating ice), and (iii) overflow into surface channels (on both the floating and grounded ice). 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.
This paper mentions lakes inland of the grounding line, meaning land-based ice – but the role of lakes like these was perhaps mostly famously illustrated in the collapse of the Larsen B ice shelf, on West Antarctica, in 2002.
In the pic above, and video below, you can see a number of these meltwater lakes on the ice shelf just before it collapsed, and it is believed that this was part of a process of weakening and undermining the ice sheet, leading it to fall apart suddenly.
No one is predicting any collapse in East Antarctica, but it is further evidence that conditions in that enormous and poorly studied area are changing rapidly. I spoke to one young experts on East Antarctica not long ago – including Jamin Greenbaum of the University of Texas, who has done some of the most significant work in the area. The video is worth look if you have not seen, and is a good review, even if you have.