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Effects of GeoEngineering on the Southern Ocean

Effects of GeoEngineering on the Southern Ocean. Judy Twedt ~ Kelly McCusker ~ Cecilia Bitz June 5, 2012. Reuters. A Tale of Two Geoengineering Strategies. increase the earth’s reflectance with stratospheric sulfate aerosols. remove greenhouse gasses. i ncreased winds;

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Effects of GeoEngineering on the Southern Ocean

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  1. Effects of GeoEngineeringon theSouthern Ocean Judy Twedt ~ Kelly McCusker ~ Cecilia Bitz June 5, 2012 Reuters

  2. A Tale of Two Geoengineering Strategies increase the earth’s reflectance with stratospheric sulfate aerosols remove greenhouse gasses increased winds; more upwelling decreased winds; less upwelling decrease global mean surface temperature Southern Ocean barely cools Southern Ocean Cools feasible now hypothetically feasible

  3. Increasing Albedo with • Sulfate Aerosols • (Kelly’s work) • Run RCP 8.5 emissions scenarios on CCSM4, with *full ocean dynamics* • In 2035, increase Earth’s albedo by prescribing stratospheric concentrations of sulfate aerosols on top of RCP 8.5 greenhouse gasses • Compare with 20th Century Climatology (1970-1999) http://www.noaa.gov/features/protecting_0808/images/volcanoashcloud.jpg

  4. Annual Mean Global Temperature RCP 8.5 288 K 1960 2060 McCusker, 2012

  5. Annual Mean Global Temperature RCP 8.5 Sulfate Engineering 288 K 1960 2060 McCusker, 2012

  6. Annual Mean Global Temp (k) RCP 8.5 Sulfate Engineering Shut-Off 288 K 1960 2060 McCusker, 2012

  7. Annual Mean Global Temperature RCP 8.5 Sulfate Engineering Shut-Off 288 K 1850 Reference 1960 2060 McCusker, 2012

  8. Annual Mean Global Temperature return to 1988 GHG concentrations 288 K 1960 2060

  9. Annual Mean Global Temperature return to 1988 GHG concentrations 288 K 1960 2060

  10. Surface Temperature Differences (k)Annual Avg of Sulfate Engineering (2045-2054) – 20th C (1970-1999) Sulfates Cool the Arctic more than the Antarctic

  11. Vertical Temperature Profile Annual Avg of Sulfate Engineering (2045-2054) – 20th C (1970-1999) pause Temperature Difference • Sulfates absorb sw radiation in the stratosphere and are confounded with greenhouse gases. • Result: a polewardshift in surface westerlies

  12. Near Surface Winds Sulfate Engineering (2045-2054) – 20th C (1970-1999) 1970-1999 control increased westerlies The change in the sulfate run is a strengthening of existing Antarctic winds

  13. Motivating Questions • Why didn’t the Southern Ocean cool? • Are winds the culprit? Does the combination of greenhouse gasses & sulfates increase the winds and induce warm water upwelling in the Southern Ocean?

  14. Modeling Wish Fulfillment (Greenhouse Gas Removal) • I ran a branch from the RCP 8.5 scenario • In 2035, dropped the GHG emissions to 1988 concentrations; ran 50 years Prescribed Greenhouse Gas Concentrations CO2 CH4 N2O CFC-11 CFC-12 350 ppm CO2 concentrations of 350 ppm have been proposed as target concentration by Hansen et. al., 2008

  15. (just a reminder) 2045 – 2054 climatology Return to 1988 concentrations sulfate geoengineering

  16. Surface Temperature DifferenceAnnual Avg (2045 – 2054) of GHG Removal – Sulfate Engineering Although the global mean surface temp is warmer, the Southern Ocean surface is already cooler!

  17. Wind Stress DifferenceAnnual Avg (2045 – 2054) of GHG Removal – Sulfate Engineering surface westerlies over Antarctica are weaker with greenhouse gas removal

  18. Zonal AvgEkman Pumping Antarctica Downwelling *positive* Upwelling *negative* ‘zero-line’ of the greenhouse gas removal run is NORTH of the sulfate run 90 S 44 S

  19. Comparison of CCSM4 Cooling Scenarios Stratospheric Sulfates Greenhouse Gas Removal Reduction in global mean surface temp Decreased Ekman pumping Ekman transport shifts northward Cooling over the Southern Ocean • Rapid reduction in global mean surface temp • Increased westerlies over the Southern Ocean – more upwelling, more heating from below • Not a viable means of protecting the Antarctic ice sheet

  20. Next Steps • Dig deeper into the ocean data and look at the subsurface ocean response • Probe the response rate: how does the Southern Ocean respond so quickly? • Remove MORE greenhouse gasses: simulate a return to pre-industrial forcing • ? ? ? ?

  21. I’d like to thank Kelly McCusker and Cecilia Bitz for their help and terrific feedback. That said, any errors are my own.

  22. xkcd.com/154

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