NOAA/WDS Paleoclimatology - Indo-Pacific Warm Pool Last Glacial Maximum Hydroclimate Proxy Synthesis

STUDY NOTES: Synthesis of hydroclimatic proxy records for the Indo-Pacific Warm Pool at the Last Glacial Maximum, indicating wet or dry hydroclimatic conditions from both marine and terrestrial proxies. The files "terr_raw" and "marine_raw" contain the locations and hydroclimate state at the LGM from a collection of proxy records. Their "val" field indicates whether the proxy captured dry(val=-1)/unchanged(val=0)/wetter(val=1) or fresh(val=-1)/unchanged(val=0)/salty(val=1) climate at the LGM. The "n_obs" field is the number of proxy techniques used to estimate LGM hydroclimate from each location. A value "is_robust=1" indicates when different proxy techniques agree in their estimates of LGM hydroclimate at each location. The "is_robust" field also takes the value of 1 when only one proxy technique is used. A value "chrono_flag=1" indicates whether the proxy record contains one or more radiocarbon U/Th or well-constrained OSL dates near to or during the LGM. A value "chrono_flag=0" indicates that the LGM was dated via wiggle-matching the local benthic d18O to a global stack or another method. The files "terr_gridded" and "marine_gridded" are the final "gridded" data as seen in the main text of DiNezio and Tierney (2013), in which proxies were averaged within a search radius of 150 km. The "is_robust" field of "terr_gridded" and "marine_gridded" indicates whether the observations merged into each "gridded" point agree (is_robust=1) or not (is_robust=0). See DiNezio and Tierney (2013) for more details.
ABSTRACT SUPPLIED BY ORIGINATOR: The Indo-Pacific warm pool - the main source of heat and moisture to the global atmosphere - plays a prominent role in tropical and global climate variability. During the Last Glacial Maximum, temperatures within the warm pool were cooler than today and precipitation patterns were altered, but the mechanism responsible for these shifts remains unclear. Here we use a synthesis of proxy reconstructions of warm pool hydrology and a multi-model ensemble of climate simulations to assess the drivers of these changes. The proxy data suggest drier conditions throughout the centre of the warm pool and wetter conditions in the western Indian and Pacific oceans. Only one model out of twelve simulates a pattern of hydroclimate change similar to our reconstructions, as measured by the Cohen's K statistic. Exposure of the Sunda Shelf by lower glacial sea level plays a key role in the hydrologic pattern simulated by this model, which results from changes in the Walker circulation driven by weakened convection over the warm pool. We therefore conclude that on glacial-interglacial timescales, the growth and decay of ice sheets exert a first-order influence on tropical climate through the associated changes in global sea level.