Global ocean heat content in the Last Interglacial

Abstract

The Last Interglacial (129-116 ka) represents one of the warmest climate intervals of the last 800,000 years and the most recent time when sea level was meters higher than today. However, the timing and magnitude of peak warmth varies between reconstructions, and the relative importance of individual sources contributing to elevated sea level (mass gain versus seawater expansion) during the Last Interglacial remains uncertain. Here we present the first mean ocean temperature record for this interval from noble gas measurements in ice cores and constrain the thermal expansion component of sea level. Mean ocean temperature reaches its maximum value of 1.1±0.3°C warmer-than-modern at the end of the penultimate deglaciation at 129 ka, resulting in 0.7±0.3m of elevated sea level, relative to present. However, this maximum in ocean heat content is a transient feature; mean ocean temperature decreases in the first several thousand years of the interglacial and achieves a stable, comparable-tomodern value by ~127 ka. The synchroneity of the peak in mean ocean temperature with proxy records of abrupt transitions in oceanic and atmospheric circulation suggests that the mean ocean temperature maximum is related to the accumulation of heat in the ocean interior during the preceding period of reduced overturning circulation.

Orbital- and millennial-scale variability of the Antarctic Circumpolar Current over the past 140,000 years

“…These strong variations of the ACC likely played an important role in shaping AMOC strength and stability over the past 140 ka. Since a vigorous ACC prevailed during the last warmer-than-present interglacial 35 , we speculate that under future warmer climates the ACC would remain similar to or stronger than today. Such a persistent cold water route return flow into the Atlantic could stabilize the AMOC in the long-term future, despite the AMOC showing emerging signs of weakening over the past decades 62 .…”

“…2A, C, E). The last interglacial (MIS 5e, ~129-116 ka) was warmer than today 35 with the average SSFS ������ value is ~49 µm, while the Holocene average (~0-10 ka) occurred slightly smaller SSFS ������ with ~47 µm ( Fig. 2E).…”

Snapshots of mean ocean temperature over the last 700,000 yr using noble gases in the EPICA Dome C ice core

“…Here we extend previous efforts in reconstructing MOT using noble gases in ice cores (Bereiter et al, 2018b;Baggenstos et al, 2019;Shackleton et al, 2020), which were limited to the last and penultimate glacial terminations, by reconstructing the glacial/interglacial MOT range for snapshots of all glacial and interglacial intervals over the last 700,000 years using the EPICA Dome C (EDC) ice core. To obtain quantitative MOT values, large corrections of the raw data for physical transport processes in the firn have to be applied, which affect the precision and accuracy of the MOT data.…”

“…Holocene elemental ratios larger than zero have also been recently observed by Shackleton et al (2020) using Taylor Glacier ice, reflecting our insufficient quantitative understanding of fractionation processes in the firn, requiring more dedicated firn gas sampling and firn gas transport modeling studies that realistically resolve seasonal variations in the gas transport, pressure variability and kinetic fractionation. However, glacial/interglacial differences in our corrected elemental ratios are not sensitive to this overall offset.…”

Review of ESSD-2019-249

“…Line 296-305 -Please specify here that the authors mean thermal expansion of the top 700 m of the ocean (which I think is what they mean, though it needs to be clarified more explicitly in the text). The authors should compare their result to other estimates of the thermosteric component of LIG sea level in addition to the McKay result (Hoffman et al, 2017;Shackleton et al, 2020).…”