Intense winter cooling of the surface water in the northern Okinawa Trough during the last glacial period

We generated a 42,000-year record of TEX86 (TEX86L and TEX86H) from core MD98-2195 to better understand changes in the hydrology of the East China Sea (ECS) in the last glacial period. The TEX86-derived temperature showed an intense cooling in the last glacial period, whereas U37K-derived spring sea surface temperature (SST) and foraminiferal Mg/Ca-derived summer SST showed a much smaller-scale cooling. The difference between the TEX86- and Mg/Ca-derived temperatures was around 14 °C from 19 to 16 ka and abruptly decreased to around 5 °C from 16 to 13 ka. This suggests a strong winter cooling of the surface water during the last glacial period. TEX86-, U37K′-, and Mg/Ca-derived temperatures were lowest at 18–17 ka, implying that the formation of cold water was maximized during that period. These results show that the cold water mass developed in the northern Okinawa Trough during the last glacial and the Kuroshio branch did not fully enter the northern margin of the Okinawa Trough.

► TEX86 record showed an intense cooling of the northern Okinawa Trough in the last glacial period.
► Compared to UK37’ and Mg/Ca, TEX86 was sensitive to surface water cooling by winter monsoon.
► The formation of cold water in the northern Okinawa Trough was maximized at 18 to 17 ka.