New evidence that it was once possible to sail across Antarctica
Tuesday, August 31, 2010 at 18:55 Why are two groups of tiny sea creatures called bryozoans nearly identical, despite being separated by 1,500 miles of ice? They must have traveled across the continent long ago - on a massive Antarctic seaway.
The bryozoan is a simple marine organism that attaches itself to the sea bed and filters nutrients out of the surrounding water. There are many different bryozoan sub-species, but a new survey of Antarctic organisms turned up some striking similarities between two distant populations. Both live on continental ice shelves, massively thick ice platforms that are created when continental glaciers reach the sea. One population is on the Ross Ice Shelf, and the other is on the Weddell Ice Shelf. As you can see onthis map, there's a whole lot of Antarctica between those two populations. So how did such similar species get to such distant locations?
David Barnes, a scientist with the British Antarctic Survey, explains why the animals couldn't have simply worked their way around the Antarctic coastline, and why they must have traveled through the continent:
"When we found groups of strikingly similar bryozoans hundreds of miles apart we knew we were onto something very interesting. Perhaps these species had survived the last ice age whereas in all other regions of Antarctica they were wiped out. We know that after the last ice age groups of bryozoans dispersed freely between many of the regions we studied. But because the larvae of these animals sink and this stage of their life is short – and the adult form anchors itself to the seabed – it's very unlikely that they would have dispersed the long distances carried by ocean currents. For the bryozoans on both the Weddell and Ross sea continental shelves to be more similar to one another than to any of those found in the waters in between is striking indeed. Our conclusion is that the colonization of both these regions is a signal that both seas were connected by a trans-Antarctic seaway in the recent past."
This seaway could have opened up as recently as 125,000 years ago, during an interglacial warm period in which the sea levels were about fifteen feet higher than they are now. We don't know the exact processes that caused this seaway to open up, but they created an opening through what's now over a mile of solid ice. The ancient seaway also calls into question how stable Antarctica's ice is today.
The West Antarctic Ice Sheet, which is the region through which this trans-Antarctic seaway must have traveled, is thought to be unstable and in danger of collapsing, partially as a result of climate change. If the ice sheet does collapse, it could increase global sea levels by 10 to 15 feet, which could displace billions of people from their homes. The bryozoan discovery could, however, help us better understand how a melting Antarctica fits into current climate change. Barnes explains:
"The West Antarctic Ice Sheet can be considered the Achilles heel of Antarctica and because any collapse will have implications for future sea level rise it's important that scientists get a better understanding of big deglaciation events. This biological evidence is one of the novel ways that we look for clues that help us reconstruct Antarctica's ice sheet history. Our new research provides compelling evidence that a seaway stretching across West Antarctica could have opened up only if the ice sheet had collapsed in the past."
Reader Comments (9)
There were also forests on Antarctica at one point when the earth was totally not warmer than it is today with industrial influences.
I know, those bryozoans gave off too much CO2 and caused global warming and as a result the ice melted!!!!
Hmmm, this inland seaway sounds a bit implausible. But it reminds me of the illegibly ancient maps of Antarctica (which show river systems) as described in Graham Hancock's 1985 book, Fingerprints of the Gods. It's a long time since I read that book, and Hancock must be completely wrong about Antarctica being the the centre of an ancient civilisation until some catastrophic pole shift the end of the last ice age - how could it be when ice core data goes back 500,000 years? But there's a lot we don't know about the ancient world and a lot we don't understand about this one so no harm in having an open mind until we have more pieces of the jigsaw.
sorry - illegibly should be allegedly (I can blame the Firefox spellchecker for that) and messed up the close italics tag. Should have previewed it but not used to that having that option on WUWT.
Having just re-read the post title, was there any old evidence that it was possible to sail across Antarctica?
"If the ice sheet does collapse, it could increase global sea levels by 10 to 15 feet, which could displace billions of people from their homes."
Hmmm.... An ice sheet by definition is already floating on water. I'm not sure what 'collapsing' means, but I assume it ultimately means 'melt'. Melting ice that was already floating on water is supposed to raise sea levels world wide by 10 to 15 feet? Anyone see a problem with this analysis?
125kyrs ago was the last interglacial back. The Eemian or MIS-5 (a through e). Orbitally, the Eemian is not as good an analogue as MIS's 11 and 19, or the 4th and 8th interglacials back, respectively. During those two interglacials the earth was also at an eccentricity minimum, as the Holocene (the present interglacial, or MIS-1) is now. The Eemian occured midway between an eccentricity minimum and maximum. Still a very careful perusal of the literature will net you estimates of the sea level highstand during the eemian of between 0 and 52 meters above present, with what appears to be fair agreement on 6 meters as the most likely. The 6 meter excusrsion is reported to have occurred during two rapid thermal pulses at the end of the roughly similaly long Eemian, which lasted something like 10-12k years. The Holocene is presently ~11,500 years old, or precisely half of the present precessional cycle of 23kyrs. Five of the last 6 interglacials have each lasted about half of a precessional cycle. Rapid, extreme thermal excusrisons (both cold and warm) seem to be common at the end interglacials, and the strong one at the end Eemian seems to have resulted in that 6 or so meter rise and is well recorded in the Bahamas. There is a lot of speculation for and against this resulting from the melting of the WAIS.
What is important to consider here is that even on things which have happened, the science is not that particularly well-settled. Which makes consensus on things which haven't happened yet perhaps a bridge too far. For a fair and balanced look at the unsettled nature of the consensus of things since the Mid Pleistocene Transition, you may want to download the free European Geosciences Union puplished paper by Tzedakis (2010) entitled "The MIS-11 - MIS-1 analogy, southern European vegetation, atmospheric methane and 'the early Anthropogenic hypothesis'". In the paper, Chronis Tzedakis presents a cogent and thorough vetting of Ruddiman's early anthropogenic GHG hypothesis (reviewed by Ruddiman himself) against the rich backdrop of data accumulated on MIS-19, MIS-11 and MIS-1, the three interglacials which have occurred during eccentricity minima since we have been in the 100kyr ice age/interglacial cycles (post Mid Pleistocene Transition).
The concluding remark is worth pondering:
"On balance, what emerges is that projections on the natural
duration of the current interglacial depend on the choice
of analogue, while corroboration or refutation of the “early
anthropogenic hypothesis” on the basis of comparisons with
earlier interglacials remains irritatingly inconclusive."
I also meant to mention that the sea level highstand during MIS-11 seems to have been something like 11 meters above present. So, during eccentricity minima, such as we are at now, it is possible for the natural climate noise to be significantly higher than the 2007 IPCC AR4 worst case prediction of 0.59 meters. Measuring a 0.59 meter AGW signal within a natural noise envelope of from 6-11 meters will be a significant accomplishment with respect to the well established literature regarding signal to noise ratio.
Jacques Voorhees writes (incorrectly......)
>>Hmmm.... An ice sheet by definition is already floating on water. I'm not sure what 'collapsing' means, but I assume it ultimately means 'melt'. Melting ice that was already floating on water is supposed to raise sea levels world wide by 10 to 15 feet? Anyone see a problem with this analysis?<<
An ice sheet is a mass of glacier ice that covers surrounding terrain and is greater than 50,000 km² (20,000 mile²), thus also known as continental glacier. It is not "floating" on water as he suggests.
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