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Meridional contrasts in productivity changes driven by the opening of Drake Passage

Meridional contrasts in productivity changes driven by the opening of Drake Passage
Meridional contrasts in productivity changes driven by the opening of Drake Passage
Changes in atmospheric pCO2 are widely suggested to have played a major role in both the long‐term deterioration of Cenozoic climate and many superimposed rapid climate perturbations such as the pivotal Eocene‐Oligocene transition. Changes in marine productivity affecting the biological oceanic carbon pump represent one possible cause of past CO2 variability. Here we explore the relationship between ocean gateway change and marine biogeochemistry. Specifically, we use a fully coupled atmosphere‐ocean‐biogeochemical model (IPSL‐CM5A) to examine global ocean paleoproductivity changes in response to the opening of Drake Passage. In our simulations, we find that Drake Passage opening yields a spatially uniform decrease in primary productivity in the low‐latitude oceans while the high‐latitude response is more spatially heterogeneous. Mechanistically, the low‐latitude productivity decrease is a consequence of a fundamental reorganization of ocean circulation when Drake Passage opens driven by the isolation of the Southern Ocean from low‐latitude water masses. Nutrient depletion in the low latitudes is driven by a marked decrease in the intensity of deep convection in the Southern Ocean, which drives the accumulation of nutrients at depth and their depletion in the intermediate and upper ocean, especially away from sites of subduction. In the high latitudes, the onset of the Antarctic Circumpolar Current in the model exerts a strong control both on nutrient availability and on regions of deep‐water formation. The qualitative agreement between geographically diverse long‐term paleoproductivity records and the simulated variations suggests that Drake Passage opening may contribute to the long‐term paleoproductivity signal.
2572-4525
Ladant, Jean-Baptiste
05b87c2c-a0de-4526-874c-debebcf80e7f
Donnadieu, Yannick
54586dcb-64b1-4c57-b780-2cb3ac04a7a5
Bopp, Laurent
771de655-3caf-42ba-8231-40f17d4addc4
Lear, Caroline H.
c0caf74d-ed6c-4b04-b5c8-de8fc794943c
Wilson, Paul A.
f940a9f0-fa5a-4a64-9061-f0794bfbf7c6
Ladant, Jean-Baptiste
05b87c2c-a0de-4526-874c-debebcf80e7f
Donnadieu, Yannick
54586dcb-64b1-4c57-b780-2cb3ac04a7a5
Bopp, Laurent
771de655-3caf-42ba-8231-40f17d4addc4
Lear, Caroline H.
c0caf74d-ed6c-4b04-b5c8-de8fc794943c
Wilson, Paul A.
f940a9f0-fa5a-4a64-9061-f0794bfbf7c6

Ladant, Jean-Baptiste, Donnadieu, Yannick, Bopp, Laurent, Lear, Caroline H. and Wilson, Paul A. (2018) Meridional contrasts in productivity changes driven by the opening of Drake Passage. Paleoceanography and Paleoclimatology. (doi:10.1002/2017PA003211).

Record type: Article

Abstract

Changes in atmospheric pCO2 are widely suggested to have played a major role in both the long‐term deterioration of Cenozoic climate and many superimposed rapid climate perturbations such as the pivotal Eocene‐Oligocene transition. Changes in marine productivity affecting the biological oceanic carbon pump represent one possible cause of past CO2 variability. Here we explore the relationship between ocean gateway change and marine biogeochemistry. Specifically, we use a fully coupled atmosphere‐ocean‐biogeochemical model (IPSL‐CM5A) to examine global ocean paleoproductivity changes in response to the opening of Drake Passage. In our simulations, we find that Drake Passage opening yields a spatially uniform decrease in primary productivity in the low‐latitude oceans while the high‐latitude response is more spatially heterogeneous. Mechanistically, the low‐latitude productivity decrease is a consequence of a fundamental reorganization of ocean circulation when Drake Passage opens driven by the isolation of the Southern Ocean from low‐latitude water masses. Nutrient depletion in the low latitudes is driven by a marked decrease in the intensity of deep convection in the Southern Ocean, which drives the accumulation of nutrients at depth and their depletion in the intermediate and upper ocean, especially away from sites of subduction. In the high latitudes, the onset of the Antarctic Circumpolar Current in the model exerts a strong control both on nutrient availability and on regions of deep‐water formation. The qualitative agreement between geographically diverse long‐term paleoproductivity records and the simulated variations suggests that Drake Passage opening may contribute to the long‐term paleoproductivity signal.

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Accepted/In Press date: 28 February 2018
e-pub ahead of print date: 25 March 2018

Identifiers

Local EPrints ID: 419023
URI: http://eprints.soton.ac.uk/id/eprint/419023
ISSN: 2572-4525
PURE UUID: 6b553077-5467-4f84-82ba-0d3e95bb683b

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Date deposited: 28 Mar 2018 16:30
Last modified: 14 Nov 2020 05:01

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Contributors

Author: Jean-Baptiste Ladant
Author: Yannick Donnadieu
Author: Laurent Bopp
Author: Caroline H. Lear
Author: Paul A. Wilson

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