Global Ocean Cooling of 2.3°C During the Last Glacial Maximum

Abstract Quantitative constraints on past mean ocean temperature (MOT) critically inform our historical understanding of Earth's energy balance. A recently developed MOT proxy based on paleoatmospheric Xe, Kr, and N2 ratios in ice core air bubbles is a promising tool rooted in the temperature d...

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Bibliographic Details
Published in:Geophysical Research Letters
Main Authors: A. M. Seltzer, P. W. Davidson, S. A. Shackleton, D. P. Nicholson, S. Khatiwala
Format: Article in Journal/Newspaper
Language:English
Published: Wiley 2024
Subjects:
gas exchange
ocean heat
Last Glacial Maximum
ice cores
noble gases
paleoclimate
Geophysics. Cosmic physics
QC801-809
ice core
Sea ice
Online Access:https://doi.org/10.1029/2024GL108866
https://doaj.org/article/42d0da9b4caa402382a0a93fe10742fd
Description
Summary:Abstract Quantitative constraints on past mean ocean temperature (MOT) critically inform our historical understanding of Earth's energy balance. A recently developed MOT proxy based on paleoatmospheric Xe, Kr, and N2 ratios in ice core air bubbles is a promising tool rooted in the temperature dependences of gas solubilities. However, these inert gases are systematically undersaturated in the modern ocean interior, and it remains unclear how air‐sea disequilibrium may have changed in the past. Here, we carry out 30 tracer‐enabled model simulations under varying circulation, sea ice cover, and wind stress regimes to evaluate air‐sea disequilibrium in the Last Glacial Maximum (LGM) ocean. We find that undersaturation of all three gases was likely reduced, primarily due to strengthened high‐latitude winds, biasing reconstructed MOT by −0.38 ± 0.37°C (1σ). Accounting for air‐sea disequilibrium, paleoatmospheric inert gases indicate that LGM MOT was 2.27 ± 0.46°C (1σ) colder than the pre‐industrial era.

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