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Arctic Sea Ice and the Ice-Albedo Feedback

Arctic Sea Ice and the Ice-Albedo Feedback. Harry Stern, Polar Science Center, University of Washington, Seattle. Climate Complexity Workshop 2012 May 9, 2012. Arctic Geography. Russia. Alaska. Canada. Greenland. Surface Area of the Earth. 40. 36%. 29%. 30. 18%. 20. 14%. 10. 3%.

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Arctic Sea Ice and the Ice-Albedo Feedback

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  1. Arctic Sea Ice and the Ice-Albedo Feedback Harry Stern, Polar Science Center, University of Washington, Seattle Climate Complexity Workshop 2012 May 9, 2012

  2. Arctic Geography

  3. Russia Alaska Canada Greenland

  4. Surface Area of the Earth 40 36% 29% 30 18% 20 14% 10 3% 0 PACIFIC OCEAN ATLANTIC OCEAN INDIAN OCEAN ARCTIC OCEAN LAND

  5. SEA ICE forms from freezing saltwater. The surface can be smooth or bumpy. Sea ice can grow to be 10 feet thick or more.

  6. ICEBERGS are chunks of glaciers that break off and float away. They are made of freshwater ice (no salt) from many years of compressed snowfall.

  7. January Monthly average sea ice concentration from satellite data National Snow and Ice Data Center (NSIDC), Boulder, CO

  8. February

  9. March

  10. April

  11. May

  12. June

  13. July

  14. August

  15. September

  16. October

  17. November

  18. December

  19. September Arctic Sea Ice Trends, 1979-2011 Courtesy of NSIDC, Boulder, CO

  20. What is a Feedback? input output something happens feedback louder sound sound amplifier feedback The outputfeeds back to the input

  21. warming sea ice melts ocean absorbs more heat more ocean exposed Ice-Albedo Feedback Positive feedback: more ice melt leads to more ice melt Also works the other way: less ice melt leads to less ice melt Operates every summer, with or without global warming Need not lead to “runaway” situation Courtesy Don Perovich, CRREL

  22. Ice Growth Feedback Positive feedback Output is enhanced Negative feedback Output is retarded Thin ice grows faster than thick ice Ice growth feedback Summer: Warming makes ice thinner Winter: Thin ice grows thicker faster same thickness by late winter thick ice ? thin ice ? positive or negative feedback? ? ? Notz (2009), PNAS, 106, #49, 20590–20595

  23. Arctic Amplification Linear surface warming trend in °C per century from NCAR CCSM3 averaged from 9 ensemble members using the SRES A1B scenario http://www.realclimate.org/index.php/archives/2006/01/polar-amplification/courtesy of Cecilia Bitz, University of Washington

  24. Is Arctic Amplification due to the Ice-Albedo Feedback? • IAF is not the whole story: • AA occurs even with no IAF (in climate models) • AA occurs even on an aqua planet (in models) • Pole-ward heat and moisture transport are factors Area of research… see: Processes and impacts of Arctic Amplification, Serreze and Barry, Global and Planetary Change 2011, 77, 85-96 Steele et al. Overland et al.

  25. Tipping Points and Hysteresis Tipping Point: Where a small change in a parameter leads to a different equilibrium state Hysteresis: The system follows a different path when the forcing is reversed http://www.ronmartin.net/blog/archives/2779 X = 0 X = 1 X = 2 2 Final state 0 Initial state

  26. Climate Change, Sea Ice Loss, and Polar Bears in Greenland Kristin Laidre and Harry Stern, University of Washington, Seattle Kristin April 2012 Track polar bear movements Monitor sea ice at bear locations Bear movements  sea ice relation?

  27. Polar bears use sea ice as a platform for hunting seals Polar bears are found all across Baffin Bay in winter Movement behavior of adult male and female polar bears (Ursus maritimus) during the spring breeding season Laidre et al. (2012) submitted

  28. Sea Ice in Baffin Bay, 1979-2011 1982-1991 1992-2001 2002-2011

  29. Changes in Dates of Spring and Fall as defined by threshold in sea ice area Fall transition Length of summer Spring transition Draw best-fit lines Are there trends? TO DO NOW

  30. Changes in Dates of Spring and Fall as defined by threshold in sea ice area +5 days/dec +12 days/dec −7 days/dec Also: Correlation of residuals = −0.64 Earlier spring tends to be followed by later fall Ice-Albedo feedback??? Other explanations?

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