Gateway-driven weakening of ocean gyres leads to Southern Ocean cooling

Declining atmospheric CO2 concentrations are considered the primary driver for the Cenozoic Greenhouse-Icehouse transition, ~34 million years ago. A role for tectonically opening Southern Ocean gateways, initiating the onset of a thermally isolating Antarctic Circumpolar Current, has been disputed as ocean models have not reproduced expected heat transport to the Antarctic coast. Here we use high-resolution ocean simulations with detailed paleobathymetry to demonstrate that tectonics did play a fundamental role in reorganising Southern Ocean circulation patterns and heat transport, consistent with available proxy data. When at least one gateway (Tasmanian or Drake) is shallow (300 m), gyres transport warm waters towards Antarctica. When the second gateway subsides below 300 m, these gyres weaken and cause a dramatic cooling (average of 2–4°C, up to 5°C) of Antarctic surface waters whilst the ACC remains weak. Our results demonstrate that tectonic changes are crucial for Southern Ocean climate change and should be carefully considered in constraining long-term climate sensitivity to CO2.

Simple

Identification info

Date (Creation)
2020-04-21
Date (Publication)
2019-02-01
Citation identifier
doi:10.25959/5eb21fc078c99

Title
Information and documentation - Digital object identifier system
Date (Publication)
2019-02-01
Citation identifier
ISO 26324:2012

Citation identifier
https://doi.org/10.25959/5eb21fc078c99

Principal investigator

Institute for Marine and Antarctic Studies (IMAS), University of Tasmania (UTAS) - Sauermilch, Isabel
IMAS - Hobart
Private Bag 129
Hobart
Tasmania
7001
Australia
ORCID ID >

Principal investigator

Institute for Marine and Antarctic Studies (IMAS), University of Tasmania (UTAS) - Whittaker, Joanne
IMAS - Hobart
Private Bag 129
Hobart
Tasmania
7001
Australia
ORCID ID >

Collaborator

Institute for Marine and Antarctic Studies (IMAS), University of Tasmania (UTAS) - Klocker, Andreas
IMAS - Hobart
Private Bag 129
Hobart
Tasmania
7001
Australia
ORCID ID >

Credit
This research was undertaken with support from Australian Research Council Special Research Initiative for Antarctic Gateway Partnership (Project ID SR140300001), Discovery Project 180102280, and computational resources from the Australian National Computational Infrastructure. We thank Dave Hutchinson for providing the forcing input data for our model. DRM is supported by the ORCHESTRA project (NE/N018095/1). KH's research has been funded by the Deutsche Forschungsgemeinschaft (DFG) under the project GO724/15-1 and institutional resources from the Research Program PACES-II, Workpackage 3.2, of the Alfred Wegener Institute (AWI). The European Research Council under the European Community’s Seventh Framework Program provided funding by ERC Starting Grant #802835 to PKB. DRM, KH and JHL received a “Visiting Scholarship” by the University of Tasmania.
Status
Completed

Point of contact

Institute for Marine and Antarctic Studies (IMAS), University of Tasmania (UTAS) - Sauermilch, Isabel
IMAS - Hobart
Private Bag 129
Hobart
Tasmania
7001
Australia
ORCID ID >

Topic category
  • Oceans

Extent

N
S
E
W


Temporal extent

Time period
2020-04-21 2030-04-21
Maintenance and update frequency
Not planned
Keywords (Theme)
  • Southern Ocean, ACC, Cenozoic Greenhouse-Icehouse Transition, Sea Surface Temperatures, Ocean Gyres, Antarctic cooling, Eocene-Oligocene transition, Tectonic gateways
NASA/GCMD Keywords, Version 8.5
Australian and New Zealand Standard Research Classification (ANZSRC): Fields of Research

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Unclassified

Resource constraints

Use limitation
The data described in this record are the intellectual property of the University of Tasmania through the Institute for Marine and Antarctic Studies.

Resource constraints

Linkage
http://i.creativecommons.org/l/by/4.0/88x31.png

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Creative Commons Attribution 4.0 International License


>

Website
http://creativecommons.org/licenses/by/4.0/

License Text

Other constraints
Cite data as: Sauermilch, I., Klocker, A & Whittaker, J. (2020). Gateway-driven weakening of ocean gyres leads to Southern Ocean cooling. Institute for Marine and Antarctic Studies (IMAS), University of Tasmania (UTAS). doi:10.25959/5eb21fc078c99
Language
English
Character encoding
UTF8

Distribution Information

OnLine resource
DATA ACCESS - ocean gyre model [index of files for download]

OnLine resource
Alternative data access via IMAS THREDDS server

Resource lineage

Statement
The ocean model used is the MIT general circulation model (MITgcm, version MITgcmUV checkpoint62x) in an ocean-only configuration with no sea ice. The model domain is circumpolar and extends between 84°S and 25°S (and 0°, see model run in SI) in latitude. The horizontal grid spacing is 0.25°, equivalent to a zonal grid spacing of ~27.8 km and a meridional grid spacing of ~3 km to ~25 km at the southern and northern boundary, respectively. The model configuration uses 50 vertical levels, ranging from 10 m at the sea surface to 368 m at the bottom. Our model uses a linear drag coefficient of 0.0011, a nonlinear equation of state, a seventh-order advection scheme for temperature and salinity and the K-profile parameterization. No parameterization is used for the advection and diffusion due to mesoscale eddies. Partial cells are used in the vertical for a more accurate representation of bathymetry. Restoring boundary conditions for the surface forcing are taken from a coupled atmosphere-ocean model (GFDL CM2.1) simulating Late Eocene conditions with atmospheric CO2 concentrations of 800 ppm. The surface forcing for sea surface temperature, sea surface salinity, and zonal and meridional wind stresses are temporally and zonally averaged values from the coupled model (Figure S1). The surface forcing is zonal averaged, in order to be able to modify the bathymetry configurations and continent-ocean distributions, without causing artificial disturbances of the ocean circulations. A sponge layer of ~300 km is used at the northern boundary of the model to relax to a temporal and zonal mean of salinity and temperature output from the coupled model with a restoring time scale of 10 days.
Hierarchy level
Dataset

Metadata

Metadata identifier
44e47376-8627-4daa-a49a-7c2d31294537

Language
English
Character encoding
UTF8

Publisher

Institute for Marine and Antarctic Studies (IMAS), University of Tasmania (UTAS) - IMAS Data Manager

Type of resource

Resource scope
Dataset
Metadata linkage
https://metadata.imas.utas.edu.au/geonetwork/srv/eng/catalog.search#/metadata/44e47376-8627-4daa-a49a-7c2d31294537

Point of truth URL of this metadata record

Date info (Creation)
2021-06-04T09:57:18
Date info (Revision)
2021-06-04T09:57:18

Metadata standard

Title
ISO 19115-3:2018
 
 

Overviews

Spatial extent

N
S
E
W


Keywords

Southern Ocean, ACC, Cenozoic Greenhouse-Icehouse Transition, Sea Surface Temperatures, Ocean Gyres, Antarctic cooling, Eocene-Oligocene transition, Tectonic gateways
Australian and New Zealand Standard Research Classification (ANZSRC): Fields of Research
Physical Oceanography
NASA/GCMD Keywords, Version 8.5
EARTH SCIENCE | CLIMATE INDICATORS | PALEOCLIMATE INDICATORS EARTH SCIENCE | CLIMATE INDICATORS | PALEOCLIMATE INDICATORS | PALEOCLIMATE RECONSTRUCTIONS EARTH SCIENCE | CLIMATE INDICATORS | PALEOCLIMATE INDICATORS | PALEOCLIMATE RECONSTRUCTIONS | SEA SURFACE TEMPERATURE RECONSTRUCTION EARTH SCIENCE | CLIMATE INDICATORS | PALEOCLIMATE INDICATORS | PALEOCLIMATE RECONSTRUCTIONS | SEDIMENTS EARTH SCIENCE | CLIMATE INDICATORS | PALEOCLIMATE INDICATORS | PALEOCLIMATE RECONSTRUCTIONS | STREAMFLOW RECONSTRUCTION EARTH SCIENCE | CLIMATE INDICATORS | PALEOCLIMATE INDICATORS | PLATE TECTONICS EARTH SCIENCE | OCEANS | MARINE GEOPHYSICS EARTH SCIENCE | PALEOCLIMATE | OCEAN/LAKE RECORDS | ISOTOPES EARTH SCIENCE | PALEOCLIMATE | OCEAN/LAKE RECORDS | MICROFOSSILS

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