Central Equatorial Pacific Cooling During the Last Glacial Maximum

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.

Glacial‐Interglacial Controls on Ocean Circulation and Temperature During the Permo‐Carboniferous

“…Alternatively, Permo-Carboniferous brachiopod Mg/Ca and δ 18 O values have been used to argue for shallow-water temperatures in the glacial tropics that were significantly colder (up to 10°C) than their modern counterparts (Giles, 2012;Powell et al, 2009). These cooler SSTs would suggest much larger oscillations in surface temperatures during the LPIA than during glacial-interglacial cycles of the Late Pleistocene (∼2-3 ± 0.5°C; Ballantyne et al, 2005;Monteagudo et al, 2021). Our simulations indicate that glacial-interglacial changes in upper ocean temperature in the low latitudes were consistently ∼3-6°C, supporting smaller SST variations in tropical oceans during the LPIA.…”

“…Nevertheless, the response of equatorial sea surface temperatures (SSTs) to changes in high-latitude glaciation during the Permo-Carboniferous remains debated, with some records of brachiopod δ 18 O supporting climatically buffered tropical oceans with less seasonality (Powell et al, 2009), while other brachiopod Mg/Ca and δ 18 O values have been used to argue for tropical SSTs that were significantly colder (up to 10 °C) than their modern counterparts (Giles, 2012). These proxy records suggest that tropical SSTs during the LPIA experienced much larger oscillations than during glacial-interglacial cycles of the Late Pleistocene (∼2-3 ± 0.5 °C; Ballantyne et al, 2005;Monteagudo et al, 2021). Reconstructing paleoceanographic events from the fossil record, however, is limited by relatively poor correlation between temperature changes and biotic reorganizations (Boersma & Premoli Silva, 1983), as minor reductions in surface temperature can represent a several-fold increase in trophic resources (Hallock et al, 1991), and by the fragmentary paleogeographic distribution of fossil remains that are often restricted to shallow coastal environments (Peters & Husson, 2017).…”

Expansion of Ocean Anoxia During Glacial Periods Recorded in the Cobalt Flux to Pelagic Sediments

“…During the LGM, asymmetric cooling in the northern hemisphere should induce a southward shift in the ITCZ (Broccoli et al., 2006), consistent with proxy reconstructions (Reimi & Marcantonio, 2016), thereby weakening the NECC. Zonal gradients in surface temperature and thermocline depth, which power the EUC, also appear to have slackened during the LGM (Ford et al., 2018; Monteagudo et al., 2021). We hypothesize that the combined reduction in eastward transport during glacial periods decreased mid‐water O 2 supply and facilitated ODZ expansion.…”

Global genetic diversity and historical demography of the Bull Shark

“…As C . leucas inhabits areas with water temperatures down to 18°C (Brunnschweiler et al., 2010; Lea et al., 2015; Matich & Heithaus, 2012; Smoothey et al., 2016, 2019, 2023), sea surface temperature changes during the LGM did not significantly reduce its distribution in the tropics (Monteagudo et al., 2021). Additionally, long‐range movements (Espinoza et al., 2016; Lea et al., 2015; Lee et al., 2019) may have facilitated colonization of newly emerged areas.…”

“…During this period, sea levels were at least 50 m below present, extending coastlines and so the available habitat for C. leucas (Carlson et al, 2010;Graham et al, 2016;Hammerschlag et al, 2012;Heupel et al, 2015;Niella et al, 2020), potentially supporting larger populations. As C. leucas inhabits areas with water temperatures down to 18°C (Brunnschweiler et al, 2010;Lea et al, 2015;Matich & Heithaus, 2012;Smoothey et al, 2016Smoothey et al, , 2019Smoothey et al, , 2023, sea surface temperature changes during the LGM did not significantly reduce its distribution in the tropics (Monteagudo et al, 2021). Additionally, long-range movements (Espinoza et al, 2016;Lea et al, 2015;Lee et al, 2019) may have facilitated colonization of newly emerged areas.…”