Health & Environmental Research Online (HERO)


Print Feedback Export to File
502418 
Journal Article 
Review 
Closing of the Central American Seaway and the ice age: A critical review 
Molnar, P 
2008 
23 
1 
English 
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 similar to 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? 
atlantic deep-water; northern-hemisphere glaciation; eastern equatorial; pacific; ocean thermohaline circulation; permanent el-nino; fe-mn; crusts; ferromanganese crusts; pb isotopes; global climate; south-america