Modeling the Miocene climatic optimum: Ocean circulation

摘要: [1] Ocean circulation is investigated using the Community Climate System Model 3 (CCSM3) forced with early to middle Miocene (∼20–14 Ma) topography, bathymetry, vegetation and modern CO2. Significant bottom water formation modeled in Weddell Sea along intermediate North Component Water Atlantic. This attributed primarily stronger- weaker-than-modern convective preconditioning Labrador Seas, respectively. Global meridional overturning gyre weaker due midlatitude westerlies southern hemisphere, caused by lowering of surface temperature gradient, addition regional influences on convection. Subsurface temperatures are significantly higher far Atlantic, Greenland-Norwegian Seas Arctic basin compared present. Ocean heat transport symmetrical about equator resembles that simulated for late Cretaceous Cenozoic climates, suggesting northern hemisphere dominated ocean active today developed after Miocene. Simulated deep warming more than an order magnitude lower indicated proxies. discrepancy not reconciled CO2 persistence sea-ice at sites formation. suggests either CCSM3 insufficiently sensitive boundary conditions, greater greenhouse forcing existed currently reconstructed, or proxy records exaggerated. Given diversity global their near-unanimous estimate a warmer Earth, first two options likely.