The latitudinal temperature gradient and its climate-dependence as inferred from foraminiferal δ18O over the past 95 million years
The latitudinal temperature gradient and its climate-dependence as inferred from foraminiferal δ18O over the past 95 million years
The latitudinal temperature gradient is a fundamental state parameter of the climate system tied to the dynamics of heat transport and radiative transfer. Thus, it is a primary target for temperature proxy reconstructions and global climate models. However, reconstructing the latitudinal temperature gradient in past climates remains challenging due to the scarcity of appropriate proxy records and large proxy-model disagreements. Here, we develop methods leveraging an extensive compilation of planktonic foraminifera δ
18O to reconstruct a continuous record of the latitudinal sea-surface temperature (SST) gradient over the last 95 million years (My). We find that latitudinal SST gradients ranged from 26.5 to 15.3
°C over a mean global SST range of 15.3 to 32.5
°C, with the highest gradients during the coldest intervals of time. From this relationship, we calculate a polar amplification factor (PAF; the ratio of change in >60
° S SST to change in global mean SST) of 1.44 6 0.15. Our results are closer to model predictions than previous proxy-based estimates, primarily because δ
18O-based high-latitude SST estimates more closely track benthic temperatures, yielding higher gradients. The consistent covariance of δ
18O values in low- and high-latitude planktonic foraminifera and in benthic foraminifera, across numerous climate states, suggests a fundamental constraint on multiple aspects of the climate system, linking deep-sea temperatures, the latitudinal SST gradient, and global mean SSTs across large changes in atmospheric CO
2, continental configuration, oceanic gateways, and the extent of continental ice sheets. This implies an important underlying, internally driven predictability of the climate system in vastly different background states.
climate modeling, foraminifera, latitudinal temperature gradients, meridional temperature gradients, sea-surface temperatures
e2111332119
Gaskell, Daniel
b0ce5014-3b53-4716-8262-8a1a88fe4aaf
Huber, Matthew
cac8c146-e2e3-4758-9fe9-46aa85e35ad2
O'Brien, Charlotte
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Inglis, Gordon
1651196d-916c-43cb-b5a0-9b3ecaf5d664
Acosta, Paul
d8501857-4b1d-4df6-a0ee-fd541378eca7
Poulsen, Christopher J.
ded76898-ecb2-415a-9bf1-13b443d3b3e9
Hull, Pincelli M.
ec74bbf9-239b-439f-a158-cfd68b575b92
15 March 2022
Gaskell, Daniel
b0ce5014-3b53-4716-8262-8a1a88fe4aaf
Huber, Matthew
cac8c146-e2e3-4758-9fe9-46aa85e35ad2
O'Brien, Charlotte
b8abe9b0-725c-41d5-8298-3f6b754e04d8
Inglis, Gordon
1651196d-916c-43cb-b5a0-9b3ecaf5d664
Acosta, Paul
d8501857-4b1d-4df6-a0ee-fd541378eca7
Poulsen, Christopher J.
ded76898-ecb2-415a-9bf1-13b443d3b3e9
Hull, Pincelli M.
ec74bbf9-239b-439f-a158-cfd68b575b92
Gaskell, Daniel, Huber, Matthew, O'Brien, Charlotte, Inglis, Gordon, Acosta, Paul, Poulsen, Christopher J. and Hull, Pincelli M.
(2022)
The latitudinal temperature gradient and its climate-dependence as inferred from foraminiferal δ18O over the past 95 million years.
Proceedings of the National Academy of Sciences, 119 (11), , [e2111332119].
(doi:10.1073/pnas.2111332119).
Abstract
The latitudinal temperature gradient is a fundamental state parameter of the climate system tied to the dynamics of heat transport and radiative transfer. Thus, it is a primary target for temperature proxy reconstructions and global climate models. However, reconstructing the latitudinal temperature gradient in past climates remains challenging due to the scarcity of appropriate proxy records and large proxy-model disagreements. Here, we develop methods leveraging an extensive compilation of planktonic foraminifera δ
18O to reconstruct a continuous record of the latitudinal sea-surface temperature (SST) gradient over the last 95 million years (My). We find that latitudinal SST gradients ranged from 26.5 to 15.3
°C over a mean global SST range of 15.3 to 32.5
°C, with the highest gradients during the coldest intervals of time. From this relationship, we calculate a polar amplification factor (PAF; the ratio of change in >60
° S SST to change in global mean SST) of 1.44 6 0.15. Our results are closer to model predictions than previous proxy-based estimates, primarily because δ
18O-based high-latitude SST estimates more closely track benthic temperatures, yielding higher gradients. The consistent covariance of δ
18O values in low- and high-latitude planktonic foraminifera and in benthic foraminifera, across numerous climate states, suggests a fundamental constraint on multiple aspects of the climate system, linking deep-sea temperatures, the latitudinal SST gradient, and global mean SSTs across large changes in atmospheric CO
2, continental configuration, oceanic gateways, and the extent of continental ice sheets. This implies an important underlying, internally driven predictability of the climate system in vastly different background states.
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More information
Accepted/In Press date: 25 January 2022
Published date: 15 March 2022
Additional Information:
Funding Information:
M.H. acknowledges support by NSF P2C2 Award 1602905. C.L.O. acknowledges the support of a Yale Institute for Biospheric Studies Donnelley Postdoctoral Environmental Fellowship and NSF P2C2 Award 1602557. G.N.I. acknowledges support by Royal Society Dorothy Hodgkin Fellowship DHF\R1\191178. R.P.A. and C.J.P. acknowledge support through Heising Simon Foundation Award 2016-05 and NSF Award 1550134. P.M.H. acknowledges support through a Sloan Ocean Fellowship and NSF P2C2 Award 1602557. We acknowledge the World Climate Research Programme, the Earth System Grid Federation (ESGF), and the participating climate-modeling groups of Coupled Model Intercomparison Project 6 (CMIP6) for producing, archiving, and promoting many of the model outputs used for this paper, as well as the multiple funding agencies that support CMIP6 and ESGF. This research used data provided by the International Ocean Discovery Program. We also thank two anonymous reviewers for comments that greatly improved this manuscript.
Funding Information:
ACKNOWLEDGMENTS. M.H. acknowledges support by NSF P2C2 Award 1602905. C.L.O. acknowledges the support of a Yale Institute for Biospheric Studies Donnelley Postdoctoral Environmental Fellowship and NSF P2C2 Award 1602557. G.N.I. acknowledges support by Royal Society Dorothy Hodgkin Fellowship DHF\R1\191178. R.P.A. and C.J.P. acknowledge support through Heis-ing Simon Foundation Award 2016-05 and NSF Award 1550134. P.M.H. acknowledges support through a Sloan Ocean Fellowship and NSF P2C2 Award 1602557. We acknowledge the World Climate Research Programme, the Earth System Grid Federation (ESGF), and the participating climate-modeling groups of Coupled Model Intercomparison Project 6 (CMIP6) for producing, archiving, and promoting many of the model outputs used for this paper, as well as the multiple funding agencies that support CMIP6 and ESGF. This research used data provided by the International Ocean Discovery Program. We also thank two anonymous reviewers for comments that greatly improved this manuscript.
Publisher Copyright:
Copyright © 2022 the Author(s)
Keywords:
climate modeling, foraminifera, latitudinal temperature gradients, meridional temperature gradients, sea-surface temperatures
Identifiers
Local EPrints ID: 455183
URI: http://eprints.soton.ac.uk/id/eprint/455183
ISSN: 0027-8424
PURE UUID: d6b0b3fc-2fb7-42f2-b8a8-eb418c0a72bf
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Date deposited: 14 Mar 2022 17:44
Last modified: 17 Mar 2024 07:09
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Contributors
Author:
Daniel Gaskell
Author:
Matthew Huber
Author:
Charlotte O'Brien
Author:
Paul Acosta
Author:
Christopher J. Poulsen
Author:
Pincelli M. Hull
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