A(68)nniversary

 

A year ago, the megaberg, A68, broke away from Larsen C (ok, so it was more than a year ago, but I’ve been away… allow me). I spoke to the BBC’s Jon Amos about it, and they made this snappy little video about it. Check it out:

So what’s happening to it now? A68 has started to drift off into the Weddell Sea, losing mass as chunks fall away, becoming ‘bergy bits’ and contributing to the melange of sea ice between the shelf and the berg. But it hasn’t gotten that far in a year:

Before it broke off, lots of people feared it would destabilise the shelf and lead to catastrophic ice shelf collapse. The situation was likened to that of neighbouring Larsen B before it collapsed in 2002: a significant calving event (i.e. a massive iceberg), followed quite soon by ice shelf collapse.

However, it seems that Larsen C may not have been destabilised in the same way its ex-neighbour was. It’s much larger, and wedged in between two ‘pinning points’ that keep it in the same place.

Besides, in any case, its collapse may not actually be that bad. In a new paper published this month (July), Clemens Schanwell and colleagues show results that suggest Larsen C’s complete collapse would have a minimal effect on global sea level (contributing no more than 4.2 mm by 2300). They argue that the buttressing effect of Larsen C – its ability to hold back glaciers that flow off the high mountains of the Antarctic Peninsula – is minimal, and that its total loss would not accelerate these glaciers enough to cause a significant amount of sea level rise.

They contrast this with another peninsula ice shelf, the George VI, which could be a much more significant contributor to global sea level (up to 22 mm by 2300) because of the glaciers it holds back, and because of the way the rock underneath the ice shelf slopes backwards, which could cause runaway ice loss by a mechanism called marine ice sheet instability.

The authors suggest this is just a small insight into what could happen across the rest of Antarctica – particularly West Antarctica – as climate changes.

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