Remote forcing at the last glacial maximum in the tropical Pacific Ocean

We present results of a Last Glacial Maximum (LGM) wind stress sensitivity experiment using a high-resolution ocean general circulation model of the t ropical 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 Intercompar ison 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 ha-If. This ocean model experiment hind casts chang es that are in close agreement with paleoceanographic data from the entire region, even without the explicit modeling of the air-sea interactions. Dat a and model both predict that the annual average thermocline tilt across th e basin was enhanced. Data and model are consistent with a stronger equator ial undercurrent which shoaled to the west of where it does today, and stro nger advection of water from the Peru Current into the east equatorial Paci fic 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 re sulting from LGM boundary conditions, while SST changes were related to ind ependent, possibly radiative, forcing. Overall, our results imply that much of the dynamic response of the tropical Pacific during the LGM can be expl ained by wind field changes resulting from global LGM boundary conditions.