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Wednesday, April 10, 2013

Antarctic Octopus genetics reveals past West Antarctic Ice sheet collapse

It seems the genetics of the Antarctic Octopus is showing us how fragile the West Antarctic Ice sheet (WAIS) may be with global warming. It raising questions about the ice sheet susceptibility to collapse.

The Antarctic octopus - Turquet's octopus - is a little creature that doesn't like moving house. It is a stay-at-home tending to live in one place and only moving short distances to escape predators. Yet when marine scientists looked at the genetic diversity of specimens of the octopus from the Ross Sea and compared them with specimens 10,000kms by sea away in the Weddell Sea they found there was little genetic difference.

To explain how these different populations can be so alike scientists believe there has been at least partial collapse of the West Antarctic Ice Sheet, with the last time perhaps being the previous interglacial period - the Eemian some 125,000 years ago. A partial collapse may have opened up a channel between the Weddell and Ross Seas.

The West Antarctic Ice Sheet is inherently unstable covering a channel and basin up to 2km below sea level. Once ice shelves and their grounding lines to the seabed start receding, the process of ice sheet collapse can happen relatively quickly (geologically speaking).

It is possible that during the Eemian interglacial that Greenland contributed about 1 meter to sea level rise, with 5-7 meters contributed by Antarctic Ice Sheets. We know that warm ocean currents are the primary force melting ice shelves which could rapidly boost mass loss from ice sheets from 80 gigatons per year to over 1,600 gigatons per year.

And the funny thing is the start of this process may be happenning now producing an Antarctic sea ice paradox. While deep warm currents are undercutting and progressively melting the ice sheets, the cold melt water forms a surface layer on the sea which helps the formation and preservation of sea ice, so we see more sea ice around Antarctica, at least for the moment.

You can read more in this Science Daily article from May 2012 on Antarctic Octopus Study Shows West Antarctic Ice Sheet May Have Collapsed 200,000 Years Ago, or more detailed links to related scientific work on the Antarctic Octopus and global warming at the Skeptical Science article just published today - Antarctic Octopus Living Testament To Global Warming

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