Reconstructing sea surface temperature, sea surface salinity and partial pressure of carbon dioxide in atmosphere in the Okinawa Trough during the Holocene and their paleoclimatic implications

Abstract

The sediment core DGKS9603 collected from the Okinawa Trough was used as research target. By use of unsaturated indexU37k of long-chain alkenone, δ13C of POC and of planktonic foraminifera (G. sacculifer), the evolutions of sea surface temperature and partial pressure of carbon dioxide in the atmosphere during the Holocene were reconstructed in the Okinawa Trough. And in combination of δ18O of planktonic foraminifera, the relative difference of sea surface salinity during the Holocene was also reconstructed. Consequently, three cooling events (E1-E3) were identified, each of which occurred at 1.7-1.6, 5.1-4.8 and 8.1-7.4 kaBP (cal), respectively. Of the three events, E2 and E3 are globally comparable, their occurrence mechanism would be that the main stream of the Kuroshio Current shifted eastward due to the enhanced circulation of the northeastern Pacific Ocean, which was driven in turn by amplified intensity of sunshine and subsequent enhancement of subtropical high pressure; E1 corresponds to the Small Ice-Age Event occurring between 1550 and 1850AD in China. In the Oki-nawa Trough, E1 might be also related to the eastward shift of main stream of the Kuroshio current driven by powerful Asia winter monsoon.