Intensified mid-Holocene Asian monsoon recorded in corals from Kikai Island, subtropical northwestern Pacific

Coupled records of Sr/Ca and oxygen isotope ratios (delta(18)O) of coral skeletons have been used to produce quantitative estimates of paleo-sea surface temperature (SST) and delta(18)O of surface seawater that can in some cases be converted to sea surface salinity (SSS). Two fossil corals from Kikai Island in the subtropical northwestern Pacific, a location affected by East Asian summer and winter monsoons, were analyzed to investigate differences between mid-Holocene and present-day SST and SSS. At 6180 cal yr BP, SSTs were roughly the same as today, both in summer and winter; delta(18)O(seawater) and SSS values were higher both in summer (+0.5 parts per thousand, +1.1 psu) and in winter (+0.2 parts per thousand, +0.6 psu) than modem values. At 7010 cal yr BP, SSTs were slightly cooler both in summer and winter (-0.8 and -0.6 degrees C), whereas delta(18)O(seawater) and SSS had higher values in summer (+0.3 parts per thousand, +0.6 psu) and in winter (+0.8 parts per thousand, +1.9 psu) than present-day values. These results are consistent with other marine records for the mid-Holocene of the low and midlatitudes in the northwestern Pacific. Such regional conditions indicate that the East Asian summer and winter monsoons were more intense in the mid-Holocene, which was likely a function of the mid-Holocene insolation regime. (c) 2007 University of Washington. All rights reserved.