by Tina van De Flierdt
It is just a bit more than two years since I made my last post here, and since we had the sampling party to take the material from our fantastic expedition back home.
Today, the first major scientific results of our endeavour were published in the journal Nature.
The team led by Jorg Pross, which included myself and my graduate student Claire Huck, found amazing evidence from spores and pollen in the very old cores we recovered. These cores reached back to the early Eocene, a time which is often described as part of the ‘Greenhouse world’. Atmospheric carbon dioxide concentrations were a lot higher back then, probably similar to what we would get when burning all our fossil fuels. We always knew that it must have been warm around Antarctica back then, but our work for the first time shows direct evidence for near tropical warmth at the Antarctic continental margin.
Joerg and his colleagues found pollen grains from palm trees and relatives of the modern baobab and macadamia. Such plants have very defined temperature ranges they are happy with, which dictate that even winter temperatures have to have been above 10°C. In contrast today, the winters in this area of Antarctica can easily reach temperatures of -10 to -20°C. Mean annuanl temperatures were probably around 17°C – quite a pleasent environment to live it and different to the ice-dominated world we witnessed two years ago!
The scientific significance of this study is far reaching. We think that during the so-called Greenhouse world atmospheric CO2 concentrations were at least double as high as they are today, and that the temperature gradient between the poles and the equator was much less pronounced than today. However, if we try to simulate the response of the climate system in models, it is very hard to achieve such a low ‘meridional temperature gradient’. Our new data deliver some key benchmark values that now have to be reconciled by models. Being successful at reconstructing Greenhouse climates may be very relevant for looking into our own future.
Before I finish I should of course give a big cheer to Claire Huck who contributed to this study by analysing some of the mud from the Eocene and figuring out where it was coming from based on its geochemical provenance. Watch this space, for more exciting data and results to come from her and from Carys Cook, who works on reconstructing the paleoclimate at the Antarctic margin in the Pliocene, just a few milion years back in time.
Also check the coverage by the BBC, which was among the first to pick up on the story.