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Climate Hustle

Antarctic Octopus Living Testament To Global Warming

Posted on 9 April 2013 by Daniel Bailey

Tell me, O Octopus, I begs
Is those things arms, or is they legs?
I marvel at thee, Octopus;
If I were thou, I'd call me Us.
-Ogden Nash

The octopus, formerly known as both a delicacy food item and for being thrown onto the ice at hockey games, now has a new recognition: a living testament to the effects of global warming.

Genetic information from an Antarctic octopus species adds to a growing body of evidence of at least a partial collapse of the West Antarctic Ice Sheet (WAIS) during a previous interglacial period (like during the Eemian interglacial some 125,000 years ago).

Click to enlarge

Turquet’s octopus.  Image courtesy of the University of Liverpool

Members of Turquet’s octopuses (pictured) tend to live in one place and only move to escape predators. This led to the understanding that specimens from areas on either side of Antarctica would be genetically different. What scientists found after examining specimens from each side of the WAIS was that both populations were genetically nearly identical.

Dr Phill Watts, from the University’s Institute of Integrative Biology, explains: "We expected to find a marked difference between Turquet’s octopuses living in different regions of the ocean, particularly between areas that are currently separated by approximately 10,000 km of sea. These creatures don’t like to travel and so breeding between the populations in the Ross and Weddell Seas [now separated by those 10,000 km of ocean] would have been highly unusual."

Antarctica

To check, scientists examined data on octopuses from other parts of Antarctica, not separated by this particular ice sheet. What they found was that the depth of the ocean and its currents limited the movement of the octopus in certain areas, as would have been expected for those living on either side of the West Antarctic Ice sheet. This added further evidence that at some point in recent history the WAIS might have collapsed.

Dr Louise Allcock, from the National University of Ireland, Galway, added: "A previous study has shown evidence that the Ross and Weddell Seas could have been connected. We wanted to investigate whether there was any genetic information that could tell us what the past environment could have been like, and this octopus species, with its large populations around the region and limited movements, was an ideal species to use."

"The fact that we found more similarities than we did differences supports the theory that the WAIS could have collapsed in the past. It also provides further evidence that scientists should continue to raise awareness about the impact of climate change on Antarctica today."

So what is the supporting evidence from other studies?

Yin et al 2011 show that warming ocean currents can undercut polar ice sheets. The results from Hellmer et al 2012 include that these warming currents could increase ice mass losses from 80 gigatons per year to over 1,600 gigatons per year, just in the area of the Filchner-Ronne Ice Shelf alone. Further, a newly discovered basin underlying the WAIS at the head of the Filchner-Ronne Ice Shelf (Ross et al 2012), serves to highlight the inherent weakness represented by this weak underbelly of the WAIS.

The evidence on the Amundsen Sea side of the WAIS tells a similar tale. Marcott et al 2011 examined evidence from previous episodes of ice sheet deglaciation and found that warming oceanic currents can penetrate ice sheets and shelves, helping to trigger rapid deglaciation events. Jacobs et al 2012 show that warming ocean currents are already undercutting the ice sheets and shelves in the area, allowing water as warm as 4°C to reach the grounding lines of the ice. Additionally, the ice shelves in the area are losing their grips on their anchor points and are tearing themselves apart in the process (MacGregor et al 2012).

Looking at further evidence from previous interglacials, work by Grant et al 2012 found a rapid coupling between ice volume and polar temperatures over the past 150,000 years, including that the timing of ice volume fluctuations agrees well with that of variations in Antarctic climate and that the amplitudes of ice volume fluctuations closely match Antarctic climate changes.

Researching an earlier interglacial (MIS 11 from about 400,000 years ago), Raymo and Mitrovica 2012 found that the West Antarctic Ice Sheet collapsed during that protracted warm period. Evidence from the NEEM Community Members study (2013) shows that during the Eemian interglacial, the Greenland Ice sheet could not have contributed much more than 1 meter of the 6-8 meters of sea level rise known to have occurred at that time.

That leaves the WAIS as the likeliest source for the remaining 4-6 meters of sea level rise known to have occurred during the Eemian interglacial. It is this collapse of the WAIS that paved the way for an opportunistic octopus species to thrive, via adaptation to a changing climate. Like the changing climate that we face today.

Credit an obscure species of octopus for the inspiration for this post.

Reference Sources

Antarctic Octopus Study Shows West Antarctic Ice Sheet May Have Collapsed 125,000 Years Ago – Strugnell et al 2012

Warming Ocean Layers Will Undermine Polar Ice Sheets, Climate Models Show – Yin et al 2011

New Weak Point Discovered in the Antarctic Ice Sheet – Hellmer et al 2012

Potential Instability in West Antarctic Ice Sheet from Newly Discovered Basin Size of New Jersey – Ross et al 2012

Ancient Glacial Melting Shows That Small Amount of Subsurface Warming Can Trigger Rapid Collapse of Ice Shelves - Marcott et al 2011

Ocean Currents Speed Melting of Antarctic Ice: A Major Glacier Is Undermined from Below - Jacobs et al 2012

West Antarctic Ice Shelves Tearing Apart at the Seams - MacGregor et al 2012


Rapid coupling between ice volume and polar temperature over the past 150,000years - Grant et al 2012

Collapse of polar ice sheets during the stage 11 interglacial - Raymo and Mitrovica 2012

Eemian interglacial reconstructed from a Greenland folded ice core - NEEM Community Members (2013)

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Comments

Comments 1 to 11:

  1. The link to http://www.nature.com/ngeo/journal/v5/n6/full/ngeo1468.html links to facebook instead.

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  2. Actually all of the links in the reference-list are Facebook-prefixed.

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    Moderator Response:

    [DB] You are correct.  Bitly was used to keep the links short for the article, originally written for the FB site The Earth Story.  I have updated the References Sources section into the standard SkS linked format.

  3. Compare Bedmap2.


    Bedmap 2


    http://spaceref.com/earth/antarctica/bedmap2-a-detailed-view-of-antarcticas-landmass.html


    If enough ice melts, the two separate populations become one.

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    Moderator Response:

    [DB] Hotlinked URL; embedded linked graphic.

  4. Rob Painting was kind enough to point out this NSIDC bedrock graphic of Antarctica:

    Antarctica

    From the Atlas of the Cryosphere, Antarctica page.

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  5. Huh. I knew a lot of Antarctica was below sea level because of the ice pressing down on it, but I'm surprised to see large contiguous swathes like that. This would suggest to me that if the mass of ice on top melts enough that it would no longer weigh enough to push the bottom ice down to the land surface large portions of the ice sheet could just 'pop' free from buoyancy and float away. Not going to happen any time soon, but significant portions of the Antarctic ice may wind up being lost through export rather than in situ melting.

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  6. interesting study, but is their life cycle well understood? i guess so for the study's been published.

    the two large gorges crossing the transantarctic mountains could still have had an ice shelf over them of course, for the extensive snowfalls on the (pen)insula mountains and south in transarctic montains. and the ross sheet might have been attached to the bottom for the rebound. but ok, +4 - +6 meters of global sea level rise from melt is still plenty. pig, thwaites and ronne to go if not greenland, and other way around. filchner will stay for a long time (origins partly on eais).  

    off topic (lame joke), there has been some rumours of ocean's fourteen movie, but i think oceans 13m ASL was bad enough.

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  7. This must be evidence that past interglacials could have been warmer or of longer in duration or both then the one we are experiencing today.  The causes of these past interglacials must have all been of natural origin. 

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  8. Yes, the last interglacial, the Eemian (about 120-130,000 years ago), was thought to be slightly warmer than present. This was due to changes in Earth's orbit and rotational tilt (obliquity) which allowed more sunlight to reach Earth's surface - especially the Northern Hemisphere. See this SkS series of posts on the last interglacial.

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  9. I wonder if the scientists have taken into account the "floating ice" consideration.  For instance, if there is a basin with a bottom is 100m below sea level filled with ice, all the ice up to sea level and approximately 10 meters above sea level will have no effect on sea level if it melts.  Only the ice above 10m above sea level will cause a rise in sea level if it melts.

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  10. # 9 william

    One has to account for the change in MSL between the Eemian and the Holocene. Eemian GAT was ~1C above the late Holocene but mean sea level was ~5m higher.

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  11. When I was reading Twenty Thousand Leagues Under the Sea as a child, I thought "Interesting but completely our of reality nonsense" because Jules Verne did not know that Antarctica was a continent rather than ice shlf like arctic. BTW, Verne could have been ignorant, because even back then (mid-end of XIX century) the adventurers could have known about antarctic mountains.
    Anyway, that has now changed: Nautilus could have swam under the antarctic ice just like octopuses did, if the action have taken place in Eemian...

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