January 18, 2005

Climate histories

Yesterday we had two guests at the University. One is an expert on climate models from California and has been on many expert panels and editorial boards for several decades. Nice guy, a mathematician and physicist by training, from Yale and Oxford. The other was a Professor from Michigan who is an expert on the role of aerosols in climate-- as it turns out, she was also a mathematician by training.

Whenever we have guests I always try to take them to visit the glaciology group. These people are in charge of the Greenland ice core project, and it is always exciting to hear their latest results and go down into the freezer. The nice thing about the big glaciers like on Greenland and Antarctica is that the snow never melts. When they drill down, they find layer after layer of ice like rings of a tree, perfectly preserving samples of snow and trapped air bubbles. they analyse this in order to reconstruct climate records, date large volcanic eruptions and so on. The fun fact I learned yesterday was that the transition from the Younger Dryas period to the Holocene was very rapid. The entire climate warmed by 6 C (11 F) over a period of just 20 years! The other fun recent result from this group is the discovery that DNA is stored in the ice cores.


At January 19, 2005 6:29 AM , Anonymous Anonymous said...

Bick here - whad kinda DNA do ya got? Lemme know and I recon if its got some signal, I can git whatcha need. Seriously. This is what I do.

At January 19, 2005 12:07 PM , Blogger Matt_J said...

The possibilities for fossil DNA seem to be enormous. The real Danish expert on DNA in ice cores (and permafrost) is a guy named Eske Willerslev. He gave a great talk at a conference I organised in June 2003. Things like dating the arrival of humans to N. America, and DNA from wooly mammoths and saber tooth tigers. He was a PhD student here and apparently he pissed off the biology department in Copenhagen (traditionalists who didn't like fossil DNA) and ended up with a research contract at Oxford for a few years. He published a lot of papers, and then came back to Copenhagen not to submit his PhD thesis but to submit a higher level thesis, like the German habilitation thesis. This was done directly to the faculty of science, not to the biology department. I have never seen so many people in our big auditorium as there were for his defense. His website (including references) is:
Some examples:
Willerslev et al., Diversity of Holocene life-forms in fossil glacier ice, PNAS USA 96, 8017 - 8021, 1999.
Willerslev et al., Isolation of nucleic acids and cultures from fossil ice and permafrost, Trends in ecology and evolution, in press.
Cooper et al., Human origins and ancient human DNA, Science 292, 1655, 2001.
Endicott et al., The genetic origins of the Andaman Islanders, Am J Hum Gen 72, 178, 2003.
Shapiro et al., Evolution and dispersal of the Beringian steppe bison, Nature, submitted.
I'm not sure of the politics of getting samples but if you have a good idea let me know and I'll talk to some people. I know them fairly well and it should be possible to get samples. For example, there is a lake at the bottom of the Greenland glacier. Cold, high pressure, and containing the remains of a boreal forest present at the end of the last warm period. When they hit the bottom of the ice, this water shot up into the borehole and froze, and now they have drilled into it and retrieved samples. They've found perfectly preserved pollen and even a pine needle, tens of thousands of years old.


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