Hydrological variability in the western tropical Pacific over the past 700 kyr and its linkage to Northern Hemisphere climatic change.

El Niño/Southern Oscillation (ENSO) events and latitudinal shifts of the Intertropical Convergence Zone (ITCZ) cause large scale hydrologic changes in the western tropical Pacific (WTP). However, there is still a debate on the role of ENSO and ITCZ shifts on the hydroclimate in the WTP and their linkage to Northern Hemisphere climate change on glacial-interglacial timescales. For that reason, we present ice volume-corrected seawater δ 18 O (δ 18 O sw-ice , a proxy for salinity) and sea surface temperature (SST) records from IMAGES Core MD06-3047B recovered from the northern WTP to investigate the hydroclimate in the WTP during the last 700 kyr. Planktic foraminifera Globigerinoides ruber based Mg/Ca-SST and δ 18 O sw-ice records reveal distinct glacial-interglacial variations. The δ 18 O sw-ice record shows that our study site is characterized by fresher conditions and thus higher precipitation during glacials than during interglacials. Our results are in good agreement with numerical model simulations, which also suggest a glacial freshening in the northern WTP. A glacial freshening of the WTP is most likely related to a substantial weakening of the Atlantic Meridional Overturning Circulation (AMOC) and/or exposure of the Maritime Continent due to sea level changes which resulted in an enhanced Pacific Walker circulation and/or southward shift of the ITCZ. In addition, SST records from the WTP and the eastern tropical Pacific (ETP) suggest an enhanced tropical Pacific zonal SST gradient and thus La Niña-like conditions, which may have contributed to fresher conditions in the WTP during glacial periods. Besides, our rainfall record is in antiphase to the Chinese speleothem δ 18 O records, supporting the idea of an opposing trend in precipitation changes between the WTP and East Asia on orbital timescales. [ABSTRACT FROM AUTHOR]