Prolonged deep-ocean carbonate chemistry recovery after the Paleocene-Eocene Thermal Maximum
(2023) In Earth and Planetary Science Letters 620.- Abstract
The Paleocene-Eocene Thermal Maximum (PETM) is a hyperthermal event at ∼56 Ma ago, caused by rapid and massive carbon releases into the ocean-atmosphere system. Currently, the PETM ocean acidification is mainly quantified in the surface ocean. By contrast, PETM carbonate chemistry changes of the deep ocean, a larger carbon reservoir, are largely qualitatively constrained by sedimentary calcium carbonate contents (%CaCO3). Here, we revisit a previously proposed method for quantifying Early Cenozoic deep-water carbonate chemistry, using boron to calcium ratios (B/Ca) in extinct benthic foraminifera Nuttallides truempyi (Brown et al., 2011). We show that calibrating core-top B/Ca in the extant relative of N. truempyi against... (More)
The Paleocene-Eocene Thermal Maximum (PETM) is a hyperthermal event at ∼56 Ma ago, caused by rapid and massive carbon releases into the ocean-atmosphere system. Currently, the PETM ocean acidification is mainly quantified in the surface ocean. By contrast, PETM carbonate chemistry changes of the deep ocean, a larger carbon reservoir, are largely qualitatively constrained by sedimentary calcium carbonate contents (%CaCO3). Here, we revisit a previously proposed method for quantifying Early Cenozoic deep-water carbonate chemistry, using boron to calcium ratios (B/Ca) in extinct benthic foraminifera Nuttallides truempyi (Brown et al., 2011). We show that calibrating core-top B/Ca in the extant relative of N. truempyi against deep-water calcite saturation degree (Ω, Ω = [CO32−] /[CO32−]saturated), rather than calcite saturation state (Δ[CO32−], Δ[CO32−] = [CO32−] - [CO32−]saturated) as originally proposed better reflects Early Cenozoic carbonate chemistry changes. Furthermore, we provide multiple deep-water Ω reconstructions paired with benthic foraminiferal carbon isotopes during the PETM. At two sites, deep-water Ω recovered synchronously with carbon isotopes but lagged the sedimentary %CaCO3 rebound, indicating a slower post-PETM deep-water Ω recovery than previously thought. This may imply that during the PETM recovery phase, carbon could have been injected into the ocean-atmosphere system, despite net carbon loss, over a prolonged period after the initial release. If so, during this period, carbon removal from the ocean via calcite burial on the seafloor in response to enhanced silicate weathering may be weakened, suggesting that more carbon was sequestered via other processes such as those related to organic carbon burial.
(Less)
- author
- Dai, Yuhao LU ; Yu, Jimin and Ji, Xuan
- organization
- publishing date
- 2023-10-15
- type
- Contribution to journal
- publication status
- published
- subject
- keywords
- B/Ca proxy, carbon cycle, paleoceanography, PETM
- in
- Earth and Planetary Science Letters
- volume
- 620
- article number
- 118353
- publisher
- Elsevier
- external identifiers
-
- scopus:85169050974
- ISSN
- 0012-821X
- DOI
- 10.1016/j.epsl.2023.118353
- language
- English
- LU publication?
- yes
- id
- 8e46b4c8-bcbf-40e3-aab6-5fbb92c31d2b
- date added to LUP
- 2023-10-24 14:12:36
- date last changed
- 2023-10-24 14:12:36
@article{8e46b4c8-bcbf-40e3-aab6-5fbb92c31d2b,
abstract = {{<p>The Paleocene-Eocene Thermal Maximum (PETM) is a hyperthermal event at ∼56 Ma ago, caused by rapid and massive carbon releases into the ocean-atmosphere system. Currently, the PETM ocean acidification is mainly quantified in the surface ocean. By contrast, PETM carbonate chemistry changes of the deep ocean, a larger carbon reservoir, are largely qualitatively constrained by sedimentary calcium carbonate contents (%CaCO<sub>3</sub>). Here, we revisit a previously proposed method for quantifying Early Cenozoic deep-water carbonate chemistry, using boron to calcium ratios (B/Ca) in extinct benthic foraminifera Nuttallides truempyi (Brown et al., 2011). We show that calibrating core-top B/Ca in the extant relative of N. truempyi against deep-water calcite saturation degree (Ω, Ω = [CO<sub>3</sub><sup>2−</sup>] /[CO<sub>3</sub><sup>2−</sup>]<sub>saturated</sub>), rather than calcite saturation state (Δ[CO<sub>3</sub><sup>2−</sup>], Δ[CO<sub>3</sub><sup>2−</sup>] = [CO<sub>3</sub><sup>2−</sup>] - [CO<sub>3</sub><sup>2−</sup>]<sub>saturated</sub>) as originally proposed better reflects Early Cenozoic carbonate chemistry changes. Furthermore, we provide multiple deep-water Ω reconstructions paired with benthic foraminiferal carbon isotopes during the PETM. At two sites, deep-water Ω recovered synchronously with carbon isotopes but lagged the sedimentary %CaCO<sub>3</sub> rebound, indicating a slower post-PETM deep-water Ω recovery than previously thought. This may imply that during the PETM recovery phase, carbon could have been injected into the ocean-atmosphere system, despite net carbon loss, over a prolonged period after the initial release. If so, during this period, carbon removal from the ocean via calcite burial on the seafloor in response to enhanced silicate weathering may be weakened, suggesting that more carbon was sequestered via other processes such as those related to organic carbon burial.</p>}},
author = {{Dai, Yuhao and Yu, Jimin and Ji, Xuan}},
issn = {{0012-821X}},
keywords = {{B/Ca proxy; carbon cycle; paleoceanography; PETM}},
language = {{eng}},
month = {{10}},
publisher = {{Elsevier}},
series = {{Earth and Planetary Science Letters}},
title = {{Prolonged deep-ocean carbonate chemistry recovery after the Paleocene-Eocene Thermal Maximum}},
url = {{http://dx.doi.org/10.1016/j.epsl.2023.118353}},
doi = {{10.1016/j.epsl.2023.118353}},
volume = {{620}},
year = {{2023}},
}