American Geophysical Union Become an AGU Member
Subscribe to AGU Journals		 AGU Home AGU Publications

Read Full Article (file size: 398919 bytes)    Cited by

PALEOCEANOGRAPHY, VOL. 23, PA2201, doi:10.1029/2007PA001574, 2008

Closing of the Central American Seaway and the Ice Age: A critical review

Peter Molnar

Department of Geological Sciences, Cooperative Institute for Research in Environmental Sciences, University of Colorado at Boulder, Boulder, Colorado, USA


Abstract

What role did the closing of the Central American Seaway play in enabling continental ice sheets to wax and wane over North America and Fennoscandia? A summary of relevant evidence presented here permits a causal relationship between them but can be interpreted to show none. The common denominator of such evidence is the approximate simultaneity of that closing with global cooling and the first major ice advance. At the resolution of paleoclimate, however, geologic evidence from Central America places only weak constraints on when interchange between Pacific and Caribbean water ceased. The strongest evidence for when North and South America became connected by a continuous land bridge, the “Great American Exchange” of vertebrates, assigns climate change the causal role, for an arid Central American climate, typical of glacial times, seems necessary for animals that inhabited savannas to pass through Panama. Paleoceanographic and geochemical studies of environments and water masses in the eastern Pacific, western Caribbean, and Atlantic in general call for continual change since ∼6 Ma or earlier, if evidence concurrent with global change near 3.5–3 Ma seems more widespread than for other times. Hypothesized connections between a closed seaway and glaciation commonly call for profoundly different North Atlantic Ocean circulation, but simulations using general circulation models provide a spectrum of differences in circulation for open and closed seaways. Might much (not all) of the evidence implicating the closing of the seaway in global climate change in fact be a consequence of that change and blind to Central America's tectonic development?

Received 21 November 2007; accepted 1 February 2008; published 11 April 2008.

Keywords: Central American Seaway; ice ages; Paleoclimate.

Index Terms: 4900 Paleoceanography (0473, 3344); 4914 Paleoceanography: Continental climate records; 4928 Paleoceanography: Global climate models (1626, 3337); 8110 Tectonophysics: Continental tectonics: general (0905); 8177 Tectonophysics: Tectonics and climatic interactions.

Read Full Article (file size: 398919 bytes)    Cited by

Citation: Molnar, P. (2008), Closing of the Central American Seaway and the Ice Age: A critical review, Paleoceanography, 23, PA2201, doi:10.1029/2007PA001574.