Tropical cooling and the onset of North American glaciation P. Huybers1 and P. Molnar2 1Department of Earth and Planetary Sciences, Harvard University, Cambridge MA, USA 2Department of Geological Sciences and Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder CO, USA
Abstract. We offer a test of the idea that gradual cooling in the eastern
tropical Pacific led to cooling of North America and the initiation
of glaciation ~3 Myr ago. Using modern climate data we estimate
how warming of the eastern tropical Pacific affects North American
temperature and ice-ablation. Assuming that the modern relationship
holds over the past millions of years, a ~4°C warmer
eastern tropical Pacific between 3–5 Ma would increase ablation in
northern North America by approximately two meters per year. By
comparison, a similar estimate of the ablation response to
variations in Earth's obliquity gives less than half the magnitude
of the tropically-induced change. Considering that variations in
Earth's obliquity appear sufficient to initiate glaciations between
~1–3 Ma, we infer that the warmer eastern equatorial Pacific
prior to 3 Ma suffices to preclude glaciation.
Citation: Huybers, P. and Molnar, P.: Tropical cooling and the onset of North American glaciation, Clim. Past, 3, 549-557, doi:10.5194/cp-3-549-2007, 2007.