Southern Ocean control on atmospheric CO<sub>2</sub> changes across late Pliocene Marine Isotope Stage M2
<p>During the Pliocene, atmospheric <span class="inline-formula">CO<sub>2</sub></span> concentrations (<i>p</i><span class="inline-formula">CO<sub>2</sub></span>) were probably sometimes similar to today's, an...
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| Main Authors: | , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2025-01-01
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| Series: | Climate of the Past |
| Online Access: | https://cp.copernicus.org/articles/21/79/2025/cp-21-79-2025.pdf |
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| Summary: | <p>During the Pliocene, atmospheric <span class="inline-formula">CO<sub>2</sub></span> concentrations (<i>p</i><span class="inline-formula">CO<sub>2</sub></span>) were probably sometimes similar to today's, and global average temperature was <span class="inline-formula">∼3 °C</span> higher than preindustrial. However, the relationships and phasing between variability in climate and <i>p</i><span class="inline-formula">CO<sub>2</sub></span> on orbital timescales are not well understood. Specifically, questions remain about the nature of a lag of <i>p</i><span class="inline-formula">CO<sub>2</sub></span> relative to benthic foraminiferal <span class="inline-formula"><i>δ</i><sup>18</sup>O</span> in late Pliocene Marine Isotope Stage (MIS) M2 (3300 ka), which was longer than during the Pleistocene. Here, we present a multiproxy paleoceanographic reconstruction of the late Pliocene subtropical–subantarctic zone. New dinoflagellate cyst assemblage data are combined with previously published sea surface temperature reconstructions to reveal past surface conditions, including latitudinal migrations of the subtropical front (STF) over the late Pliocene at Ocean Drilling Program (ODP) Site 1168, offshore of western Tasmania. We observe strong oceanographic variability at the STF over glacial–interglacial timescales, especially the interval (3320–3260 ka) across MIS M2. By providing tight and independent age constraints from benthic foraminiferal <span class="inline-formula"><i>δ</i><sup>18</sup>O</span>, we find that, much more than benthic <span class="inline-formula"><i>δ</i><sup>18</sup>O</span> or local SST, latitudinal migrations of the STF are tightly coupled to global <i>p</i><span class="inline-formula">CO<sub>2</sub></span> variations across the M2. Specifically, a northerly position of the STF during the MIS M2 deglaciation coincides with generally low <i>p</i><span class="inline-formula">CO<sub>2</sub></span>. We postulate that the Southern Ocean <span class="inline-formula">CO<sub>2</sub></span> outgassing varied strongly with migrations of the STF and that this in part accounted for the variability in <i>p</i><span class="inline-formula">CO<sub>2</sub></span> across MIS M2.</p> |
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| ISSN: | 1814-9324 1814-9332 |