New estimates for salinity changes in the Western Pacific Warm Pool during the Last Glacial Maximum: oxygen-isotope evidence

Oxygen-isotope analyses of planktonic foraminifera from 57 western Pacific deep-sea cores are compared for the Holocene and the Last Glacial Maximum (LGM). Carbonate dissolution, sedimentation rates/bioturbation, sample density, and vital effects are assessed before the sea-surface salinity signal of these records is reconstructed. Average glacial-interglacial Delta delta(18)O values in the western Pacific are found to be close to those in the Atlantic Ocean (1.76 parts per thousand in the Pacific compared to 1.80 parts per thousand in the Atlantic), questioning previous suggestions of a larger salinity difference between the Atlantic and the Pacific oceans during the LGM. During the LGM, sea-surface salinity was higher in the western Pacific than today (by > similar to 1 parts per thousand), implying that evaporation minus precipitation was higher all over the region. The minimum change in sea-surface salinity occurred around the equator at the core of the Western Pacific Warm Pool. Holocene high-amplitude, high-frequency fluctuations in planktonic delta(18)O records north and south of the present limits of the Western Pacific Warm Pool are indicative of sea-surface temperature and/or sea-surface salinity variations related to its expansion and contraction at the scale of thousands of years. Such high-amplitude, high-frequency fluctuations at the edge of the WPWP are best documented in the delta(18)O signal of ODP Hole 828A offshore Vanuatu, so far the best high-resolution record for the western Pacific.