HR: 0800h
AN: PP11A-0212    [Abstracts]
TI: Precessional and Sea Level Induced Hydrological Changes in the Mediterranean Sea During the Messinian Salinity Crisis
AU: * Murphy, L N
EM: lmurphy@atmos.umd.edu
AF: University of Maryland, 3417 Computer and Space Sciences Building, College Park, MD 20910, United States
AU: Kirk-Davidoff, D
EM: dankd@atmos.umd.edu
AF: University of Maryland, 3417 Computer and Space Sciences Building, College Park, MD 20910, United States
AU: Mahowald, N
EM: nmm63@cornell.edu
AF: Cornell University, 2140 Snee Hall, Ithaca, NY 14850, United States
AU: Otto-Bliesner, B
EM: ottobli@ucar.edu
AF: National Center for Atmospheric Research, CCR, CGD/NCAR, PO Box 300, Boulder, CO 80307, United States
AB: The Messinian Salinity Crisis (MSC) occurred nearly 6 million years ago when tectonic uplift closed the straits connecting the Mediterranean Sea (MS) with the Atlantic Ocean. High rates of evaporation and diminishing water input led to a 1500-2500 m drop in MS level and the deposition of a thick layer of evaporites (Hsu et al, 1973). Cyclic patterns in evaporite deposition during the MSC have been correlated with variations in precession. It is important to model both sea level induced climatic changes and precessional changes to see how they feedback on the hydrological cycle and therefore the desiccation process during this remarkable event. In this study, experiments were conducted using the National Center for Atmospheric Research (NCAR) Community Atmosphere Model (CAM 3.1) configured with a Slab Ocean Model (SOM). We attempted to break down the series of events that occurred during the MSC to isolate the effect of each separate component on the atmosphere. In all experiments the horizontal ocean heat transport is turned off to represent the isolation of the MS from the Atlantic Ocean. The first experiment simulated the beginning of the MSC when a substantial sea level lowering occurred and extremely dry conditions led to deposition of the "Lower Evaporite" layer. In this experiment the level of the MS is reduced by 1500 m and water is removed from the basin. Lowering the sea level of the MS results in anomalous cooling of more than 2 K in the North Pacific. This agrees with proxy data that indicates extensive glaciation just after the initiation of the MSC. Another experiment simulated the end of the MSC during the Lago-Mare event when water is believed to have existed at the bottom of the desiccated sea. In our Lago-Mare experiment, the sea level is reduced up to 1500 m but water remains in the basin. Our Lago-Mare simulation results in anomalous wintertime warming of more than 10 K over the MS. Anomalous heating drives local changes in the wind field that leads to convergence at the northern margin of the basin. This yields a topographically induced precipitation anomaly of more than 1500 mm yr-1 over the Alps when water remains at the bottom of the basin. This result supports geological evidence of wetter conditions in the peripheral mountains that are believed to have led to more humid conditions during the Lago-Mare event. New results simulating the influence of the precessional cycle on the climate of the desiccated basin in both scenarios will be presented. Precessional variations, which influence the hydrological cycle, may play a key role in the desiccation process.
DE: 0429 Climate dynamics (1620)
DE: 0466 Modeling
DE: 0473 Paleoclimatology and paleoceanography (3344, 4900)
DE: 1223 Ocean/Earth/atmosphere/hydrosphere/cryosphere interactions (0762, 1218, 3319, 4550)
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting