HR: 0800h
AN: PP21B-1558    [Abstracts]
TI: Ocean gateways and the thermohaline circulation through the Cenozoic
AU: * von der Heydt, A
EM: A.S.vonderHeydt@phys.uu.nl
AF: Institute for Marine and Atmospheric Research, Utrecht University, Princetonplein 5, Utrecht, 3584CC Netherlands
AU: Dijkstra, H A
EM: H.A.Dijkstra@phys.uu.nl
AF: Institute for Marine and Atmospheric Research, Utrecht University, Princetonplein 5, Utrecht, 3584CC Netherlands
AB: Climate model simulations of various time periods through the Cenozoic have indicated that due to tectonic changes different thermohaline circulation patterns have existed. These simulations show, that in the Oligocene, deep water formation was (i) shallower than today and (ii) took place in both the Pacific and Atlantic Oceans. In contrast, today deep water forms mainly in the North Atlantic. These differences may have had consequences for the (local) climate at northern middle and high latitudes, because the ocean transports more heat into the high latitudes where deep water is formed. In the Oligocene, the salinity contrast between Pacific and Atlantic Ocean is reduced as compared to the present day case. As a consequence, surface salinities in the North Pacific are higher than today and favor deep water formation in that area. The different salinity distribution in the world oceans is probably due to the equatorial circum-global seaway that existed in the Oligocene and increased the salt exchange between Atlantic and Pacific Oceans. On the other hand, in the Miocene, where the Tethys Seaway is closed, salt exchange between the two oceans was still possible through the Central American Seaway, but the climate model simulations indicate much lower salinities in the North Pacific and almost no deep water formation. The flow pattern that is associated with each continental gateway configuration seems therefore crucial to explain the distribution of salt between the two oceans. In this presentation we investigate under which conditions a thermohaline circulation with deep water formation in both Atlantic and Pacific northern high latitudes is favored. We use parameter studies within idealized ocean models to explain the different circulation states that have been found in the climate model simulations.
DE: 4928 Global climate models (1626, 3337)
DE: 4962 Thermohaline
SC: Paleoceanography and Paleoclimatology [PP]
MN: Fall Meeting 2005