| Abstract: We present results of a Last Glacial
Maximum (LGM) wind stress sensitivity experiment using a high-resolution
ocean general circulation model of the tropical Pacific Ocean. LGM
wind stress, used to drive the ocean model, was generated using an
atmospheric general circulation model simulation forced by LGM boundary
conditions as part of the Paleoclimate Modeling Intercomparison Project
(PMIP) [Broccoli, 2000]. LGM wind stress anomalies were
large in the western half of the basin, yet there was a significant
hydrographic response in the eastern half. This ocean model
experiment hind casts changes that are in close agreement with
paleoceanographic data from the entire region, even without the explicit
modeling of the air-sea interactions. Data and model both predict
that the annual average thermocline tilt across the basin was
enhanced. Data and model are consistent with a stronger equatorial
undercurrent which shoaled to the west of where it does today, and
stronger advection of water from the Peru Current into the east
equatorial Pacific and across the equator. Paleoproductivity and
sea surface temperature (SST) data are interpreted in light of the
modeling results, indicating that paleoproductivity changes were related
to wind-forced dynamical changes resulting from LGM boundary conditions,
while SST changes were related to independent, possibly radiative,
forcing. Overall, our results imply that much of the dynamic
response of the tropical Pacific during the LGM can be explained by wind
field changes resulting from global LGM boundary conditions. |