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
20 18%
14%
10
3%
0
PACIFIC ATLANTIC INDIAN ARCTIC
LAND
OCEAN OCEAN OCEAN OCEAN

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

21. What is a Feedback?
input output
something The
happens outp
feed u
s ba t
to th c
e in p k
ut
feedback
louder
sound sound
amplifier
feedback

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

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

24. 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

25. 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.

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

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. 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

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
Fall
transition
Length of
summer
Spring
transition
Draw best-fit lines
TO DO NOW Are there trends?

31. 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?