Surface and subsurface single foraminifera analyses from the Western Pacific Warm Pool over the Plio-Pleistocene

The Western Equatorial Pacific (WEP) warm pool, with surface temperatures >28 °C and a relatively deep thermocline, is an important source of latent and sensible heat for the global climate system. Because the tropics are not sensitive to ice-albedo feedbacks, Understanding the WEP's response to radiative forcing can be used to is key to constraining a minimum estimate of Earth system sensitivity because the tropics are not sensitive to ice-albedo feedbacks. Climate modeling of pCO2-radiative warming projections shows little change in WEP variability; To investigate the warm pool's long-term response to radiative forcing, here we use temperature distributions of individual surface and subsurface dwelling foraminifera to evaluate past variability and possible radiative and dynamic climate forcing over the Plio-Pleistocene. We investigate WEP warm pool variability within paired glacial-interglacial (G-IG) intervals for four time slices: the Holocene-Last Glacial Maximum, ~2 Ma, ~3 Ma, and ~ 4 Ma. were analyzed from glacial-interglacial (G-IG) pairs from four time slices over the last four million years. The individual foramininfera distribution within each sample represent decadal to seasonal variability. We predict no change in temperature distribution between populations of foraminifera if temperatures primarily respond to pCO2-radiative forcing. Our results show the that these SST surface and subsurface temperature distributions of single foraminifera from G-IG pairs are similar for all G-IG pairs, indicating . We predict no change in temperature distributionsub-century variability, between populations of foraminifera if temperatures primarilyeven as respond to pCO2-radiative forcing and other boundary conditions changed on G-IG timescales. Plio-Pleistocene SST distributions compared to the Holocene, did not change indicating WEP SSTs respond to pCO2-radiative forcing and associated feedbacks. In contrast, Plio-Pleistocene subsurface temperature distributions suggest subsurface temperatures respond to changes in thermocline temperature and depth. When these four time slices are compared to the Holocene, In comparison to the Holocene, SST distributions are similar while subsurface distributions are not. This suggests surface temperatures over the last four million years SSTs also respond to pCO2-radiative forcing and associated feedbacks while subsurface temperatures respond to dynamic forcing, such as changes in thermocline structure or depth.and subsurface temperatures within G-IG pairs respond to pCO2-radiative forcing and associated feedbacks. In contrast, subsurface temperatures over the last four million years respond to dynamic forcing, such as changes in thermocline structure or depth. We estimate tropical temperature sensitivity at ~3 Mafor the mid-Pliocene (~3 Ma) using our individual foraminifera SST dataset and a previously published high-resolution boron isotope based pCO2 reconstruction. Additionally, we adjust our SST dataset for possible changes in the Mg/Ca of seawater for the Pliocene. We find tropical temperature sensitivity was equal to, or less than that of the Late Pleistocene.