High-Resolution Records of Surface and Thermocline Conditions during Glacial Terminations I through IV from the Sulu Sea in the Far Western Pacific

Accurate high-resolution records of transitions from glacial to interglacial conditions, termed terminations, are crucial to our understanding of how global and regional climate respond to Milankovitch driven insolation forcing and how that climate variability drives ice sheet melting and growth. The Younger Dryas (12.9-11.6 ka), a brief return to glacial-like conditions during Termination I, was the most notable event during the most recent termination, but the cause of the event is still under debate and it is unclear if a Younger Dryas-like event is a feature of all terminations. With its high sedimentation rate (>15 cm/ka) and excellent carbonate preservation, the Sulu Sea, located in the far western Pacific, is ideal for generating records of past terminations and was one of the first locations where abrupt changes in climate and/or surface ocean conditions during the Younger Dryas chronozone was identified in the tropical Pacific. Younger Dryas-like events during Terminations II (~136-128 ka), III (~250-240 ka), and IV (~344-334 ka) are apparent in previously published 18O records generated using the surface-dwelling foraminifera Globigerinoides ruber from Sulu Sea core MD97-2141. These data suggest Younger Dryas-like events were not unique to Termination I and may have been a regular occurrence during glacial terminations. To identify temperature and 18Ow contributions to these events, we present newly generated Mg/Ca based temperature and 18Ow records from the same core and foraminifera species. Recent 18O, Mg/Ca based temperature, and 18Ow records from Sulu Sea core MD97-2141 generated using the thermocline dwelling foraminifera Globorotalia tumida show Sulu Sea thermocline salinity increased during the Younger Dryas in response to a northward shift of the North Equatorial Current bifurcation latitude located east of the Philippines. We generate similar 18O, Mg/Ca based temperature, and 18Ow records from G. tumida spanning Terminations II, III, and IV to investigate whether the Younger Dryas-like events observed in the Sulu Sea surface during those intervals also affected the Sulu Sea thermocline. Preliminary G. tumida 18O data show clear evidence of a Younger Dryas-like event in the Sulu Sea thermocline during Termination III, but not during Terminations II or IV.