Tropical Atlantic climate and ecosystem regime shifts during the Paleocene–Eocene Thermal Maximum
The Paleocene–Eocene Thermal Maximum (PETM, 56 Ma) was a phase of rapid global warming associated with massive carbon input into the ocean–atmosphere system from a <sup>13</sup>C-depleted reservoir. Many midlatitude and high-latitude sections have been studied and document changes in...
| Main Authors: | , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2018-01-01
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| Series: | Climate of the Past |
| Online Access: | https://www.clim-past.net/14/39/2018/cp-14-39-2018.pdf |
| Summary: | The Paleocene–Eocene Thermal Maximum (PETM, 56 Ma) was a phase of rapid
global warming associated with massive carbon input into the ocean–atmosphere
system from a <sup>13</sup>C-depleted reservoir. Many midlatitude and high-latitude
sections have been studied and document changes in salinity, hydrology and
sedimentation, deoxygenation, biotic overturning, and migrations, but detailed
records from tropical regions are lacking. Here, we study the PETM at Ocean
Drilling Program (ODP) Site 959 in the equatorial Atlantic using a range of
organic and inorganic proxies and couple these with dinoflagellate cyst
(dinocyst) assemblage analysis. The PETM at Site 959 was previously found to
be marked by a ∼ 3.8 ‰ negative carbon
isotope excursion (CIE) and a ∼ 4 °C surface
ocean warming from the uppermost Paleocene to peak PETM, of which
∼ 1 °C occurs before the onset of the CIE. We
record upper Paleocene dinocyst assemblages that are similar to PETM
assemblages as found in extratropical regions, confirming poleward
migrations of ecosystems during the PETM. The early stages of the PETM are
marked by a typical acme of the tropical genus <i>Apectodinium</i>, which
reaches abundances of up to 95 %. Subsequently, dinocyst abundances
diminish greatly, as do carbonate and pyritized silicate microfossils. The
combined paleoenvironmental information from Site 959 and a close-by shelf
site in Nigeria implies the general absence of eukaryotic surface-dwelling
microplankton during peak PETM warmth in the eastern equatorial Atlantic,
most likely caused by heat stress. We hypothesize, based on a literature
survey, that heat stress might have reduced calcification in more tropical
regions, potentially contributing to reduced deep sea carbonate accumulation
rates, and, by buffering acidification, also to biological carbonate
compensation of the injected carbon during the PETM. Crucially, abundant
organic benthic foraminiferal linings imply sustained export production,
likely driven by prokaryotes. In sharp contrast, the recovery of the CIE
yields rapid (≪ 10 kyr) fluctuations in the abundance of
several dinocyst groups, suggesting extreme ecosystem and environmental
variability. |
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| ISSN: | 1814-9324 1814-9332 |