Sea surface temperature anomalies in the oceans at the LGM estimated from the alkenone-U<inf>37</inf>^K′ index: Comparison with GCMs

U37K′ sea surface temperature (SST) estimates for the Last Glacial Maximum (LGM) are discussed and compared to coupled general circulation model (GCM) results. We conclude that U37K′ estimates and most numerical models agree in the magnitude of the large scale SST cooling features of the glacial ocean. There was a larger cooling in the northern than in the Southern Hemisphere. The eastern boundary currents and equatorial regions were also colder. There is a consensus between models and alkenone data for a tropical cooling of about -2°C, which is in disagreement with both a smaller cooling as suggested by the CLIMAP project reconstruction, or a more pronounced cooling as suggested from coral proxy records. The comprehensive HadCM3 simulation examined reproduces a puzzling feature of the U37K′-SST reconstruction, i.e., the warming of the glacial north Atlantic, which needs further investigation using numerical modelling and proxy data reconstruction. Copyright 2004 by the American Geophysical Union.