Low-latitude climate control on sea-surface temperatures recorded in the southern Okinawa Trough during the last 13.3 kyr

Abstract

Paleotemperature records were reconstructed for the past 13.3kyr using the alkenone unsaturation index (UK′37) and the tetraether index of 86 carbon atoms (TEX86) proxies measured in sediment core OKI-151, which was collected in the southern Okinawa Trough. The UK′37- and TEX86-derived temperatures for the top sample are close to the modern mean annual sea-surface temperature (SST). Changes in SSTs in the southern Okinawa Trough were primarily controlled by the western tropical Pacific Ocean, low-latitude winter insolation, and sea-level rise. Unlike previous studies, we found that the high-latitude North Atlantic played no significant role in the SST variations in this area. Moreover, SSTs in the southern Okinawa Trough decoupled from the East Asian summer monsoon system in the last 13.3kyr. The UK′37- and TEX86-based SSTs dropped significantly at 7.6–6.9kyr BP (centered on 7.3kyr BP). These findings suggest that the cold event at 7.3kyr BP was widely recorded in the Okinawa Trough. However, the TEX86-based SSTs dropped approximately 14°C during this period for an unknown reason.