Millennial meridional dynamics of the Indo-Pacific Warm Pool during the last termination

Abstract

Abstract.To develop an in-depth understanding of the natural dynamics of the Indo-Pacific Warm Pool (IPWP) during the last deglaciation, stacked north-(N-) and south-IPWP (S-IPWP) thermal and hydrological records over the past 23-10.5 ka were built using planktonic foraminiferal geochemistry data from a new core, MD05-2925 (9.3 • S, 151.5 • E, water depth 1661 m) in the Solomon Sea and eleven previous sites. Ice-volume-corrected seawater δ 18 O (δ 18 O SW−IVC ) stacks show that S-IPWP δ 18 O SW−IVC values are indistinguishable from their northern counterparts through glacial time. The N-IPWP SST (sea surface temperature) stacked record features an increasing trend of 0.5 • C ka −1 since 18 ka. Its S-IPWP counterpart shows an earlier onset of temperature increase at 19 ka and a strong teleconnection to high-latitude climate in the Southern Hemisphere. Meridional SST gradients between the N-and S-IPWP were 1-1.5 • C during the Bølling/Allerød period and 1 • C during both Heinrich event 1 and the Younger Dryas, due to a warmer S-IPWP. A warm S-IPWP during the cold events could weaken the southern hemispheric branch of the Hadley cell and reduce precipitation in the Asian monsoon region.

Nonlinear climatic sensitivity to greenhouse gases over past 4 glacial/interglacial cycles

“…S7). This correlation implies a persistent teleconnection between the two regions (Figs S7–S9) 12 . Therefore, the southern WPWP and EEP regions are linked to Southern Ocean climate and/or affected directly by the RF GHG 3, 15, 16 .…”

“…S5) shows that the Solomon Sea SST record is characterized by strong obliquity pacing and a good correlation with Antarctic temperature changes during the past four G/IG cycles. The Southern Hemisphere (SH) middle- to high-latitude climate apparently exerts a significant influence on the Solomon Sea, possibly by oceanic tunnel connections 11, 12 (Figs S5–S9). …”

“…The higher SST and increased latent heating may also have acted as a positive feedback mechanism, contributing to the collapse of high-latitude ice sheets 25 . Rapid warming in the equatorial Pacific possibly further weakened Hadley circulation 12 and strengthened the SH westerlies. The enhanced Southern Ocean upwelling was then able to release more CO 2 into the atmosphere 23 .…”

“…All benthic foraminiferal tests were >250 μm in size, and 2–5 tests were used to measure δ 18 O values. Our group has reported the first 282-kyr age model 12, 29 and adopt the interspecies δ 18 O offset constants from previous studies 29 . All oxygen isotope age control points are summarized in Table S1.…”

“…The age model for MD05-2925 was established using radiocarbon dates 12 and composite benthic foraminiferal oxygen isotopic stratigraphy (Figs S2, S3). The Mg/Ca ratios of planktonic foraminifera, Globigerinoides ruber , were determined using a sector field inductively coupled plasma mass spectrometer (SF-ICP-MS) 13 and were used to establish a 360-kyr SST sequence with 200- to 900-year resolution.

Figure 1A sea surface temperature map with site locations, schematic circulation, and distribution of water masses.

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