HR: 15:00h
AN: A13C-06 INVITED     [Abstracts]
TI: An hypothesis for tropical climate stability and extratropical instability
AU: * Emanuel, K
EM: emanuel@texmex.mit.edu
AF: Massachusetts Institute of Technology, Rm 54 1620 MIT 77 Mass Ave, Cambridge, MA 02139
AB: A curious feature of climate change over the last several hundred millions years is the relative stability of tropical climate. While high latitude temperature fluctuates over a range of 10o C or more, tropical surface temperatures change by only a few degrees. For example, during the early Eocene, polar temperatures are thought to have been about 15 o C warmer than present, while tropical sea surface temperatures are estimated to have been only a few degrees warmer. In this talk, I will present recent research results that suggests that the comparative stability of tropical climate can be explained by a feedback involving the ocean's thermohaline circulation. The strength of this circulation is rate-limited by vertical mixing in the Tropics, and yet the source of this mixing is controversial. In current climate models, the mixing coefficient is largely independent of climate. I will show that much of the mixing is due to global tropical cyclone activity, which itself is a strong function of tropical climate. Increasing tropical temperature leads to greatly increased tropical storm activity, increasing vertical mixing and accelerating the thermohaline circulation. This in turn transports heat poleward, cooling the Tropics but accelerating the warming of high latitudes.
DE: 3344 Paleoclimatology
DE: 4215 Climate and interannual variability (3309)
SC: Atmospheric Sciences [A]
MN: 2004 AGU Fall Meeting