Central Equatorial Pacific Cooling During the Last Glacial Maximum. Issue 3 (5th February 2021)

• Record Type: Journal Article
• Authors: Monteagudo, Minda Moriah; Lynch‐Stieglitz, Jean; Marchitto, Thomas M.; Schmidt, Matthew W.
• Is Part Of: Geophysical research letters. Volume 48:Issue 3(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-02-05
• Subjects: foraminifera -- Last Glacial Maximum -- Mg/Ca -- Paleoceanography -- Paleoclimate -- Tropical Pacific; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1029/2020GL088592
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: Establishing tropical sea surface temperature (SST) during the Last Glacial Maximum (LGM) is important for constraining equilibrium climate sensitivity to radiative forcing. Until now, there has been little data from the central equatorial Pacific in global compilations, with foraminiferal assemblage‐based estimates suggesting the region was within 1°C of modern temperatures during the LGM. This is in stark contrast to multi‐proxy evidence from the eastern and western Pacific and model simulations which support larger cooling. Here we present the first estimates of glacial SST in the central equatorial Pacific from Mg/Ca in Globigerinoides ruber . Our results show that the central Pacific cooled by about 2.0°C during the LGM, in contrast with previous global compilations but in agreement with models. Our data support a larger magnitude of tropical LGM cooling, and thus a larger equilibrium climate sensitivity, than previous studies which relied on foraminiferal assemblages in the central tropical Pacific. Plain Language Summary: Reconstructing how tropical Pacific climate changed during periods of variable atmospheric CO2 levels may improve our understanding of how this region will respond to anthropogenic forcing. The Last Glacial Maximum, (LGM, 19–23, 000 years before present), is the most recent time in earth history when atmospheric CO2 was significantly different than pre‐Industrial values. Proxy‐based reconstructions of LGM sea surface temperatures (SSTs) are often used as a point of comparison with output from climate models. These models indicate ∼2°C cooling in the central equatorial Pacific during the LGM, in contrast with earlier microfossil‐based estimates which suggest very little LGM cooling. Here, we use the chemistry of unicellular protists called foraminifera to estimate SSTs during the LGM in the central equatorial Pacific. Our data show that the central equatorial Pacific cooled by about 2°C during the LGM, in agreement with models and supporting the notion that this region may be more sensitive to CO2 change than previously suggested. Key Points: We present the first Mg/Ca data from the glacial Central Equatorial Pacific, which confirms cooling in agreement with model output A compilation of tropical Mg/Ca records indicates larger glacial cooling than previous proxy compilations Together these data suggest that Equilibrium Climate Sensitivity estimates based on earlier global proxy compilations may be underestimated