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. Greenland Alaska Canada Russia

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

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.

7. 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.

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

9. February

10. March

11. April

12. May

13. June

14. July

15. August

16. September

17. October

18. November

19. December

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

21. What is a Feedback? inputoutput something happens feedback sound louder sound amplifier feedback The output feeds back to the input

22. Courtesy Don Perovich, CRREL Ice-Albedo Feedback ocean absorbs more heat more ocean exposed sea ice melts warming 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

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

24. 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/ http://www.realclimate.org/index.php/archives/2006/01/polar-amplification/ courtesy of Cecilia Bitz, University of Washington Arctic Amplification

25. Overland et al. 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.

26. Tipping Points and Hysteresis http://www.ronmartin.net/blog/archives/2779 X = 0X = 1X = 2 Final state Initial state 0 2 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

27. 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?

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

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

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

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