Talk by Joel Pedro, Centre for Ice and Climate – Niels Bohr Institute - University of Copenhagen

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Talk by Joel Pedro, Centre for Ice and Climate

The Spatial Extent and Dynamics of the Antarctic Cold Reversal

Abstract
The Antarctic Cold Reversal is a millennial-scale cooling observed in Antarctic ice cores which coincides with the warm conditions of Greenland Interstadial 1. I use high-resolution Southern Hemisphere palaeoclimate records from multiple archives (ice core, marine, speleothem and others) to generate a map of the ACR's spatial extent. The map is compared to surface temperature data from a recent fully-coupled transient simulation spanning the same period (conducted on the Community Climate System Model 3, see He et al., Nature, 2013). Good agreement is observed; the general pattern in both observations and model is of ACR cooling in Antarctica, the South Atlantic and the Southern Ocean poleward of ~40°S, and of a Greenland-like warming in continental regions equator-ward of ~20–30°S.

The cooling in the South Atlantic and Southern Ocean is consistent with a positive anomaly in the modeled northward ocean heat flux in the these regions -- i.e the classic bipolar ocean seesaw. At the same time, observed warming in the southern tropics to sub-tropics is consistent with enhanced southward atmospheric heat transport linked to a strengthening of the Southern Hemisphere winter Hadley cell. I argue that disparate observations of millennial-scale climate variability can be brought together into a more unified framework through consideration of both ocean and atmospheric heat transport; i.e. the presence of opposing ocean and atmospheric seesaws. I also discuss the speed of propagation of the ocean and atmospheric signals.