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The Southern Ocean in a Changing Climate
Our Common Future Under Climate Change
Paris
July 7, 2015
Andrew Thompson
Califor...
Antarctic
Circumpolar
Current
Antarctic
Slope Front
The two-dimensional Southern Ocean
• Uniform upwelling of Deep Waters around Antarctica.
• “Monolithic” outflow of Bottom ...
Our three-dimensional Southern Ocean
Orsi & Whitworth (2005)
60°W 30°W 0° 30°E
Our three-dimensional Southern Ocean
Orsi & Whitworth (2005)
60°W 30°W 0° 30°E
Overturning
circulation
The classic interpretation of
the ocean’s overturning
involves two-distinct cells.
Marshall & Spee...
A more recent interpretation
involves cycling through the
Southern Ocean twice.
Overturning
circulation
Marshall & Speer (...
Atlantic
Loop
Southern
Ocean
Pacific
LoopA more recent interpretation
involves cycling through the
Southern Ocean twice.
O...
A zonally-asymmetric Antarctic Circumpolar Current
Current speed
Eddy kinetic energy
Thompson & Richards (2011)
Changes in the
Antarctic Circumpolar Current
Eddy energy and eddy transports are largely
focused in the lee of major topog...
Hogg et al. (2014)
Changes in the
Antarctic Circumpolar Current
Eddy energy and eddy transports are largely
focused in the...
Localization of ventilation
and subduction
Sallée et al. (2010)
Localization of eddy activity
influences tracer transport ...
Three-dimensional changes
in sea ice patterns
Sea ice distributions and sea ice duration
are responding to both changes in...
Pritchard et al. (2012)
Pritchard et al. (2012)
Documenting changes in shelf properties suffers from:
• a lack of observations;
• a limited unders...
Antarctic shelf water Schmidtko, et al. (2014)
ASBW = Antarctic continental Shelf Bottom Water
Antarctic shelf water changes
ASBW = Antarctic continental Shelf Bottom Water
Schmidtko, et al. (2014)
Antarctic CDW changes Schmidtko, et al. (2014)
Eddy transport at the Antarctic margins Stewart and Thompson (2015)
Eddy transport at the Antarctic margins
Surface
CDW
Bottom
Surface
CDW
Bottom
Stewart and Thompson (2015)
Cross-shelftrans...
Southern Ocean glider deployments
Jan. - March, 2012; Weddell Sea
Dec. - April, 2015; Drake Passage
CDW
WSDW
WW
Antarctic
margins
Thompson et al. (2014)
Evidence of eddy transport across the continental shelf break within ...
Evidence of eddy transport across the continental shelf break within Circumpolar Deep Water layers;
good agreement with hi...
Major Southern Ocean research topics are moving towards a three-dimensional interpretation
of dynamics and biogeochemistry...
1) Upper ocean, three-dimensional pathways and their influence on mass transport, heat uptake,
carbon sequestration and pr...
• Three gliders, 10 weeks of continuous
sampling.
• Over 750 profiles of T, S, dissolved O2,
fluorescence, optical backsca...
The Southern Ocean in a Changing Climate, Andrew Thompson
The Southern Ocean in a Changing Climate, Andrew Thompson
The Southern Ocean in a Changing Climate, Andrew Thompson
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The Southern Ocean in a Changing Climate, Andrew Thompson

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Andrew Thompson (California Institute of Technology; Pasadena, CA) at the Our Common Future Under Climate Change conference, July 7-10 in Paris, France.

More at http://www.commonfuture-paris2015.org/

Published in: Science
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The Southern Ocean in a Changing Climate, Andrew Thompson

  1. 1. The Southern Ocean in a Changing Climate Our Common Future Under Climate Change Paris July 7, 2015 Andrew Thompson California Institute of Technology; Pasadena, CA
  2. 2. Antarctic Circumpolar Current Antarctic Slope Front
  3. 3. The two-dimensional Southern Ocean • Uniform upwelling of Deep Waters around Antarctica. • “Monolithic” outflow of Bottom Waters to the north. Depth Latitude
  4. 4. Our three-dimensional Southern Ocean Orsi & Whitworth (2005) 60°W 30°W 0° 30°E
  5. 5. Our three-dimensional Southern Ocean Orsi & Whitworth (2005) 60°W 30°W 0° 30°E
  6. 6. Overturning circulation The classic interpretation of the ocean’s overturning involves two-distinct cells. Marshall & Speer (2012)
  7. 7. A more recent interpretation involves cycling through the Southern Ocean twice. Overturning circulation Marshall & Speer (2012) The classic interpretation of the ocean’s overturning involves two-distinct cells. Talley (2013)
  8. 8. Atlantic Loop Southern Ocean Pacific LoopA more recent interpretation involves cycling through the Southern Ocean twice. Overturning circulation Deepwater formation Bottom water formation Marshall & Speer (2012) The classic interpretation of the ocean’s overturning involves two-distinct cells. Talley (2013); Ferrari et al. (2014)
  9. 9. A zonally-asymmetric Antarctic Circumpolar Current Current speed Eddy kinetic energy Thompson & Richards (2011)
  10. 10. Changes in the Antarctic Circumpolar Current Eddy energy and eddy transports are largely focused in the lee of major topographic features. Remotely-sensed surface observations suggest an intensification of eddy activity over the past 20 years. Hogg et al. (2014)
  11. 11. Hogg et al. (2014) Changes in the Antarctic Circumpolar Current Eddy energy and eddy transports are largely focused in the lee of major topographic features. The zonal transport of the ACC has remained steady or weakened slightly over this period. Reason: A localized eddy saturation? Remotely-sensed surface observations suggest an intensification of eddy activity over the past 20 years.
  12. 12. Localization of ventilation and subduction Sallée et al. (2010) Localization of eddy activity influences tracer transport and ventilation in the Southern Ocean. An understanding of three- dimensional tracer transport- pathways is critically needed.
  13. 13. Three-dimensional changes in sea ice patterns Sea ice distributions and sea ice duration are responding to both changes in atmospheric and oceanic circulations. Stammerjohn et al. (2008)
  14. 14. Pritchard et al. (2012)
  15. 15. Pritchard et al. (2012) Documenting changes in shelf properties suffers from: • a lack of observations; • a limited understanding of dynamics.
  16. 16. Antarctic shelf water Schmidtko, et al. (2014) ASBW = Antarctic continental Shelf Bottom Water
  17. 17. Antarctic shelf water changes ASBW = Antarctic continental Shelf Bottom Water Schmidtko, et al. (2014)
  18. 18. Antarctic CDW changes Schmidtko, et al. (2014)
  19. 19. Eddy transport at the Antarctic margins Stewart and Thompson (2015)
  20. 20. Eddy transport at the Antarctic margins Surface CDW Bottom Surface CDW Bottom Stewart and Thompson (2015) Cross-shelftransport(Sv)Cross-shelftransport(Sv)
  21. 21. Southern Ocean glider deployments Jan. - March, 2012; Weddell Sea Dec. - April, 2015; Drake Passage
  22. 22. CDW WSDW WW Antarctic margins Thompson et al. (2014) Evidence of eddy transport across the continental shelf break within Circumpolar Deep Water layers; good agreement with high resolution models. Depth(m)
  23. 23. Evidence of eddy transport across the continental shelf break within Circumpolar Deep Water layers; good agreement with high resolution models. Antarctic margins Thompson et al. (2014) Observed
  24. 24. Major Southern Ocean research topics are moving towards a three-dimensional interpretation of dynamics and biogeochemistry of the ACC and the Antarctic margins. Conclusions (Southern Ocean Dynamics and Biogeochemistry, Caltech, February 2015; EOS, in press)
  25. 25. 1) Upper ocean, three-dimensional pathways and their influence on mass transport, heat uptake, carbon sequestration and preformed nutrients. Zonal variations in mass and tracer fluxes extend throughout the water column and localize cross- ACC transport. How this three-dimensional exchange will adjust in a changing climate is unknown. 2) Buoyancy forcing and gas exchange in the marginal sea ice zone. Observations needed to resolve surface processes that occur in the region that spans the winter sea ice extent to coastal polynyas remain sparse. Specifically, measurements are needed to determine the strength of buoyancy forcing and the efficiency of gas equilibration in a lead-filled, divergent sea ice field. 3) Continental shelf/slope controls on mass and tracer fluxes. High resolution process modeling and better parameterizations of eddy processes over the continental shelf and slope are needed to understand localization of transport due to topographic features and the injection of nutrients (iron) into the water column. Major Southern Ocean research topics are moving towards a three-dimensional interpretation of dynamics and biogeochemistry of the ACC and the Antarctic margins. Conclusions (Southern Ocean Dynamics and Biogeochemistry, Caltech, February 2015; EOS, in press)
  26. 26. • Three gliders, 10 weeks of continuous sampling. • Over 750 profiles of T, S, dissolved O2, fluorescence, optical backscatter. • Roughly 5 dives (~20 km) per day. Drake Passage Powell Basin Orkney Plateau Joinville Ridge Mid. Jan. Mid. March

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