Evolution of mean ocean temperature in Marine Isotope Stage 4
<p>Deglaciations are characterized by relatively fast and near-synchronous changes in ice sheet volume, ocean temperature, and atmospheric greenhouse gas concentrations, but glacial inception occurs more gradually. Understanding the evolution of ice sheet, ocean, and atmosphere conditions from...
| Main Authors: | , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2021-10-01
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| Series: | Climate of the Past |
| Online Access: | https://cp.copernicus.org/articles/17/2273/2021/cp-17-2273-2021.pdf |
| Summary: | <p>Deglaciations are characterized by relatively fast and
near-synchronous changes in ice sheet volume, ocean temperature, and
atmospheric greenhouse gas concentrations, but glacial inception occurs more
gradually. Understanding the evolution of ice sheet, ocean, and atmosphere
conditions from interglacial to glacial maximum provides insight into the
interplay of these components of the climate system. Using noble gas
measurements in ancient ice samples, we reconstruct mean ocean temperature
(MOT) from 74 to 59.7 ka, covering the Marine Isotope Stage (MIS) 5a–4
boundary, MIS 4, and part of the MIS 4–3 transition. Comparing this MOT
reconstruction to previously published MOT reconstructions from the last and
penultimate deglaciation, we find that the majority of the last
interglacial–glacial ocean cooling must have occurred within MIS 5. MOT
reached equally cold conditions in MIS 4 as in MIS 2 (<span class="inline-formula">−2.7</span> <span class="inline-formula">±</span> 0.3 <span class="inline-formula"><sup>∘</sup></span>C relative to the Holocene, <span class="inline-formula">−0.1</span> <span class="inline-formula">±</span> 0.3 <span class="inline-formula"><sup>∘</sup></span>C
relative to MIS 2). Using a carbon cycle model to quantify the CO<span class="inline-formula"><sub>2</sub></span> solubility pump, we show that ocean cooling can explain most of the
CO<span class="inline-formula"><sub>2</sub></span> drawdown (32 <span class="inline-formula">±</span> 4 of 40 ppm) across MIS 5. Comparing MOT to
contemporaneous records of benthic <span class="inline-formula"><i>δ</i><sup>18</sup></span>O, we find that ocean cooling
can also explain the majority of the <span class="inline-formula"><i>δ</i><sup>18</sup></span>O increase across MIS 5 (0.7 ‰
of 1.3 ‰). The timing of ocean warming and cooling in
the record and the comparison to coeval Antarctic isotope data suggest an
intimate link between ocean heat content, Southern Hemisphere high-latitude climate,
and ocean circulation on orbital and millennial timescales.</p> |
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| ISSN: | 1814-9324 1814-9332 |