The secrets of hidden lakes of water in #Antarctic hint at dire consequences


Sunsurface lake underneath the Roi Baudouin Ice Shelf in east Antarctica

Chris Mooney has been writing within the Washington Post about a lake of water that exists underneath an ice shelf in East Antarctica …

“Many people refer to East Antarctica as being too cold for significant melt,” says Jan Lenaerts, a glaciologist with the Utrecht University in the Netherlands. “I mean there’s marginal melt in summer, but there’s not a lot.”

That’s the common wisdom, at least, but it is challenged in a new study in Nature Climate Change, by Lenaerts and his colleagues from universities in the Netherlands, Belgium, and Germany. They do so based on research they conducted atop the very large Roi Baudouin ice shelf in East Antarctica, which floats atop the ocean, and where they found a very Greenland-like situation in early 2016.

The background context is that they were investigating a 2 Km crater that was thought to have been the result of a meteorite impact that possibly happened in either 2004 or 2007 or even earlier. What they discovered was that it was instead a lake bed. After drilling into the ice, they were rather astonished to discover lakes. Not just one, but as many as 55 of these lakes. They were discovered under the surface of the ice shelf.

Key Point: The ice shelf is not solid ice.

In other words, because the ice shelf is structurally like this, its integral strength is compromised and it has the potential for collapse.

Ice shelf collapse is real. We have seen that actually happen with both the Larson A ice shelf in 1998 and Larson B in 2002 in the west Antarctic, and Larson C appears to be going the same way. An Ice Shelf is like a barrier that holds back vast amounts of glacial ice, and so when it collapses, it opens up the way for that ice to flow out into the ocean and raise sea level.

The Paper Itself

The paper entitled “Meltwater produced by wind–albedo interaction stored in an East Antarctic ice shelf“. was published online on 12th Dec in Nature. (Apologies, there is a paywall at that link).

Lakes … not just one, but lots of lakes …

shallow ice drilling and radar (Supplementary Fig. 1) revealed multiple englacial lakes several metres under the surface (Fig. 1f and Supplementary Movie 2), with lake top depth increasing towards the coast (Fig. 1c). These features are suggestive of meltwater production above the grounding line. The meltwater flows downhill onto the ice shelf, where it collects in surface depressions (Fig. 1b) and forms lakes that get buried by new snow, progressively submerging as they are advected towards the calving front. The finding of englacial meltwater storage suggests that meltwater production is more abundant than assumed by the detection of supraglacial water from aeroplanes or satellites15–17. Combined analysis of visible (Moderate Resolution Imaging Spectroradiometer (MODIS)), radar satellite imagery and ice-shelf topography (Methods) confirmed the presence of at least 55 supraglacial and englacial lakes in the grounding zone of the RBIS during summer (Fig. 1a).

Side note: The acronym within the above extract from the paper, RBIS, stands for “Roi Baudouin Ice Shelf”.

This is not just a paper that records observational data, they also have an explanation. They explain that the Micro Climate on the ice shelf appears to causes these lakes …

To explain these meltwater features, we use local meteorological and firn observations retrieved in austral summers 2014–2015 and 2015–2016

…the downslope winds disrupt the surface-based temperature inversion, efficiently increasing temperatures and decreasing relative humidity. Summer near-surface temperatures are significantly higher …

… This regional warming doubles the surface meltwater production when compared with the region farther downstream,…

…Both the melting of snow and the exposure of blue ice enhance the absorption of short-wave radiation and hence melt rates…

…As a result, surface melt almost quadruples in both summer seasons (Supplementary Fig. 3). This illustrates that surface melt in the RBIS grounding zone is strongly controlled by short-wave radiation availability and the melt–albedo feedback.

So basically,

  • the micro-climate on the ice shelf causes the ice to melt.
  • That then gets covered in snow and iced over … but it remains liquid
  • As the ice slowly flows towards the oceans, lakes like this are deeper down … but still remain liquid
  • There are lots of these lakes, “at least” 55

In other words, the ice shelf is not all solid ice and that tells us a great deal about the structural integrity and potential for collapse.

Exactly where is this?

The paper itself has a handy map to illustrate it. there on the top right it shows you the precise location.

The Lake Under The Ice – A Video

Below is a short video of a hole being cut into the ice and then a camera being lowered into it. The picture at the top comes from this.

Further Insights

This Ice Shelf is neither special nor unique …

“We see similar things going on on neighboring ice shelves, and also for instance on the Amery ice shelf, which is also a notorious, very large ice shelf on East Antarctica, We see this link between strong winds and blue ice formation, enhanced absorption of solar radiation, and the melt that is enhanced by this process.”

– Jan Lenaerts, a glaciologist with the Utrecht University in the Netherlands, and lead author of the Nature paper

So the important observation about all of this from Mr Lenaerts is this …

“If this region can get warmer in the future, the meltwater production will enhance a lot, and we can only expect these features, these processes to be more present than they are now, With potential implications for hydrofacturing to happen and for ice shelf stability.”

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