SST phases in the open-ocean and margins of the tropical Pacific; implication on tropical climate dynamics

Abstract. The tropical Pacific exerts a major effect on the global climate system and might have driven large extra-tropical climate change. We present a 320 kyr high resolution U^K'₃₇-sea surface temperature (SST) record from core MD052928 (11°17.26' S, 148°51.60' E, water depth 2250 m) located off southeastern Papua New Guinea (PNG), in the western tropical Pacific. The age model of the core is based on AMS ¹⁴C dating of planktic foraminifers and correlation of benthic to the LR04 stack. The U^K'₃₇-SST ranges from 26.5 to 29 °C, showing glacial–interglacial and millennial variations. We assess the phase of the MD052928 U^K'₃₇-SST as part of a synthesis of five other SST records from the tropical Pacific at the precession, obliquity, and eccentricity bands. The SST records can be separated into two groups when considering SST phase relative to changes in orbital forcing, ice volume and greenhouse gases (GHGs). SST maxima at open-ocean sites within primary equatorial current systems occur between obliquity maxima and methane (CH₄) maxima but early relative to ice volume minima and CO₂ maxima at the obliquity band. In contrast, SST maxima at continental margin sites change are in phase with ice minima and CO₂ maxima, likely influenced by the slow response of continental ice sheets and GHGs. At the precession band, the early group located on the Warm Pool area indicates a direct influenced by the local insolation, and with the similar phase progress as the obliquity band. These results indicate that the decreased high-low latitudes insolation gradient and increasing low latitude local insolation resulting in tropical Pacific SST rise. Higher SST would supply more moisture resulting in increased CH₄ in the tropical wetlands. This promotes increasing CO₂ and deglaciation leading to increase continental and continental margin surface temperatures.