Talk by Emilie Capron

A new temperature data synthesis as an improved benchmark to model the Last Interglacial climate

The Last Interglacial (LIG, 129-116 thousand of years BP, ka) offers an opportunity to assess the effect of warmer-than-present-day polar climate on climate-sensitive parts of the Earth system. However, mainly because aligning records from different archives and from different parts of the world is not trivial, a spatio-temporal picture of LIG temperature changes is difficult to obtain.

I will present the first LIG compilation of high-latitude temperature changes associated with a coherent temporal framework built between 47 ice core and marine sediment records and the associated four data-based time slices with temperature anomalies (compared to present-day conditions) for 115, 120, 125 and 130 ka. They provide improved benchmarks to perform climate model-data comparison exercises.

In particular, I will discuss a comparison of the 130 ka data-based time slice with the surface temperatures simulated by two General Circulation Models (GCM; CCSM3 and HadCM3) as part of the PMIP3 2012 General Meeting. This exercise highlights that the two GCMs predict warmer-than-present-day conditions earlier than documented in the North Atlantic, while neither model is able to produce the reconstructed early Southern Ocean and Antarctic warming. It strongly suggests that important processes were missing in the set-up of those model experiments.

I will finally show that by including realistic freshwater forcing in HadCM3 to account for the early melting of the Northern Hemisphere ice sheets, we are now able to simulate the asynchronous pattern observed between the two hemispheres in the 130 ka data-based time slice. Our new 130 ka simulations also suggest that the Antarctic surface temperatures are better reproduced when accounting, in addition to a realistic freshwater forcing, for the disintegration of the West Antarctic Ice sheet.