What Makes East Antarctica Warmer and Colder Than Present in the Last Million Years?

Abstract:

The climate of East Antarctica over the last 800 ka can be deduced in some detail from deep ice cores – most notably the EPICA Dome C core and the Dome Fuji core. These cores provide us with evidence of a relatively uniform climate across the ice sheet (though with some differences), and of the sequence of interglacials and glacials running up to the present. Changes in the observed signal in ice cores can be the result of a number of influences: changes in ice sheet altitude due to isostatic effects and ice sheet thickness changes, changes in the way water isotopes record temperature, and changes in underlying climate. I will discuss each of these, although changes in climate are probably the main influence at these sites.

Of the influences on East Antarctic climate, orbital and greenhouse gas forcing are well-defined (the greenhouse gases from the ice cores themselves). Using these, together with estimates of the state of northern hemisphere ice the climate of East Antarctica over the last 800 ka is rather well simulated, except for some striking differences between interglacials, and between data and simulation, for the recent interglacials. This suggests that there is an additional and significant local forcing, implying an important role for peak warmth due to changes in the bipolar seesaw, and a possible influence of changing ice cover in West Antarctica, which is very poorly known.

Finally the abstract title cheekily claims a million years, but an ice core extending a million years remains in the future. I will however hold out the prospect of 1.5 Ma ice within the next decade.