Tropical cooling and the onset of North American glaciation
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.
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.