ARCTIC SEA ICE PAST, PRESENT AND FUTURE

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ARCTIC SEA ICEPAST, PRESENT AND FUTURE
Asgeir Sorteberg, Marianne Skolem Andersenand
Nils Gunnar Kvamstø Asgeir.Sorteberg_at_gfi.uib.no
Nils.Kvamsto_at_gfi.uib.no
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SUMMER SEA ICE EXTENT
1979-2008 IPCC TREND 15 OBS TREND 30
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QUESTIONS

• PREDICTIONS WILL THIS CONTINUE?
• UNDERSTANDING OF THE PROCESSES
• ENVIRONMENTAL AND SOCIO-ECONOMIC IMPACT

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ENERGY RESOURCES
25 of remaining oil/gass reserves estimated to
be in the Arctic
Estimated reserves
Rest of the world
N. Afrika Caspian Sea Middle East
Arctic
1 Barents Sea 2 Southern Kara Sea and West
Siberia 3 Northern Kara Sea 4 Laptev Sea 5
East Siberian Sea 6 Chuchi Sea 7 Alaska North
Slope 8 East Greenland
USGS estimates
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TRANSPORT
2008
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CULTURAL
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ECOSYSTEMS
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OBSERVATIONS OF SEA ICE
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ARCTIC SEA - ICE
Arctic sea ice covers an area the size of USA
Its separating the relatively warm ocean from a
cold atmosphere Maximum sea ice extent is in
March minimum in September.
NERSC, 2009
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ARCTIC SEA ICE EXTENT
Various regional time series back to 1900 Good
quality satellite measurements of the total
extent since 1979
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OBSERVED CHANGE IN SUMMER SEA ICE EXTENT
CHANGE IN SEPTEMBER ICE EXTENT RELATIVE TO
1979-2000 MEAN (Stroeve et al 2009)
Slope -11.1 (/- 3.3) per decade
Area of lost sea ice equal to 7 times the area
of Norway
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ARCTIC SEAICE THICKNESS

• Submarine data
• (upward looking sonar)
• 1958/77 and 1993/97
• Thinning of 42
• Rothrock et al. (1999)
• (based on 9 cruises)
• 1976 and 1996,
• Thinning of 43
• Wadhams and Davis (2001)
• (based on 2 cruises)
• 1980 to 2000
• Thinning 37 (1.25m)
• Rothrock et al. (2008)
• (based on 34 cruises)

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ARCTIC SEAICE THICKNESS

• Remote sensing (radar altimetry)
• 1993-2001 wintertime
• No significant thinning
• Large year to year variability
• Laxon et al (2003)
• (ERS data up to 81.58N)
• 2003-2008
• No significant trend, but
• 2008 drop
• Giles et al. (2008)
• (Envisat data, up to 81.58N)

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ARCTIC SEAICE THICKNESS

• Remote sensing (electromagnetic
• induction (EM) from helicopter)
• 2001, 2004, 2007
• 2007 1m below 2001 and 2004
• Haas (2008)
• (close to North Pole)

Haas (2008)
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ARCTIC SEAICE THICKNESS
1950
1975
2000
1900
1990
2010
Reduction
Regional extent (Nordic Seas, Russia)
Reduction
Satellite extent
Summer 30, annual 8
Submarine thickness
Reduction
1 m (40)
Satellite Thickness (to 81N)
No trend
EM Thickness (north Pole region)
Reduction
1m
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OBSERVATIONS OF FORCING TERMS
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OCEANIC ENERGY BUDGET
Li Si
so
L Latent heat S sensible heat

• Forcing terms
• Ice export
• Ocean heat transport and heat content
• Surface flux
• Lets see if there has been changes in someof
  these terms

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RADIATION TERMS
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Reconstructions of the solar irradiance
Last 200 years Last 50 years
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THE SOLAR MAGNETIC ACTIVITY CYCLE
INSTRUMENTAL MEASUREMENTS EXIST SINCE
1979 (composite of several instruments)
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RADIATIVE FORCING
Radiative forcing is defined as the change in net
irradiance at the tropopause. Net irradiance is
the difference between the incoming radiation
energy and the outgoing radiation energy in a
given climate state AFTER allowing for
stratospheric temperatures to readjust to
radiative equilibrium, but with surface and
tropospheric temperatures and state held fixed at
the unperturbed values. W/m2
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RADIATIVE FORCING FROMATMOSPHERIC GREENHOUSE
GASSES
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RADIATIVE FORCING LAST 250 YEARS
GREENHOUSE GASES
2.63 W/m2
TROPOSPHERIC OZONE
0.35 W/m2
SOLAR RADIATION
0.12 W/m2
STRATOSPHERIC OZONE
-0.05 W/m2
VEGETATION CHANGES
-0.20 W/m2
PARTICLES FROM POLLUTION -0.50
W/m2
PARTICLES EFFECT ON CLOUDS -0.70
W/m2
SUM
1.65 W/m2
IPCC, 2007
IPCC., 2007
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HOW DOES ATMOSPHERIC ENERGY TRANSPORT AFFECT
SEA-ICE?
HEAT TRANSPORT ACROSS 60ºN
Smedsrud and Sorteberg, 2008
Model study (Andersen and Sorteberg, 2009)
indicates that the increased atm. energy flux
reduced the sea ice thickness with 20 from
1970-1990
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1DICE

• 1D model of the Arctic AOI (Barents s. not incl)
• Atmosphere is a grey body in LW and transparent
  in SW
• Optical thickness as vertical coordinate
• 41 classes of sea ice characterized by Hice,
  Hsnow, Tice, area
• Ocean 350 m column with mixing at the top

(Björk and Söderkvist, 2002)
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FORCING / PRESCRIPTIONS

• Lateral atmospheric and oceanic energy transport
• Solar rad at TOA
• All precip as snow
• Wind
• Ice export
• River run off

• Input Monthly values
• Time step 1 day

(Björk and Söderkvist, 2002)
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Sensitivity increase
A more realistic vertical distribution of the
atmospheric energy transport results in a higher
sea ice sensitivity to transport anomalies!
Accuracy of atmospheric energy transport is
important!
Andersen and Sorteberg (2009)
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13 member ensemble repeated annual cycle in D.
dD one month at the time

• Larger (non-linear) senstivity for positive
  summer perturbations

• Air temperature is close to melting point in
  summer ? extra energy may melt ice
• Larger fraction of open waters and thin sea ice
  gives a sea ice cover that is more sensitive to
  anomalies in atmospheric energy transport
• ? ice-albedo feed-back
• Ice-albedo feedback gets stronger and faster with
  a depth dependent sea-ice albedo

Andersen and Sorteberg (2009)
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Simulated annual sea ice thickness development
Atmospheric energy transport
Ice export
Andersen and Sorteberg (2009)
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INCREASED NET OCEANIC ENERGY TRANSPORT INTO THE
ARCTIC?
80TW
40TW
130TW
5TW
40TW
Skagseth, 2008
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INCREASED NET OCEANIC ENERGY TRANSPORT INTO THE
ARCTIC?
Possibly more oceanic heat transport last few
years Warm water into Arctic does not
necessarily means more melting. Depends on
turbulent mixing Observations indicates that
turbulent mixing is low outside shelf areas
(Sirevåg, 2008)
89N, 166E
Model study (Smedsrud and Sorteberg, 2008)
indicates that an increase in oceanic heatflow
of 40TW (5W/m2) over 10 years reduces the ice
thickness with 10-15
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INCREASED NET EXPORT OF ICE OUT OF ARCTIC?
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INCREASED NET EXPORT OF ICE OUT OF ARCTIC?
Smedsrud and Sorteberg, 2008
Kwok, 2008
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Satellite data shows no clear trend in sea ice
export, but maybe large export in 2007/08
Model study (Smedsrud and Sorteberg, 2008)
indicates that an increase in ice export of
35 (same as 2007/08 level) over 10 years will
reduce ice thickness with 15-20, but have large
impact on year-to-year variability
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RADIATIVE ANDDYNAMICAL FORCINGS
1950
1975
2000
1900
1990
2010
Increased
Anthropogenic forcing
No trend
Solar
Increased
Atmospheric heat transport
Reduction
Increased
Oceanic heat transport
?
Possibly high
No trend
Ice Export
?
Possibly high
No trend
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CHANGE IN RADIATIVE FORCINGS SOLAR POSITIVE
FORCING LAST 200 YEARS, NO TREND LAST 50 0.05-0.2
W/m2 ANTROPOGENIC POSITIVE FORCING LAST 200
YEARS, STRONG TREND LAST 50 1.5 W/m2 LAST 200, 1
W/m2 LAST 50 DYNAMICALLY INDUCED
CHANGES ATMOSPHERIC HEAT TRANSPORT POSSIBLE
POSITIVE TREND LAST 50 YEARS (NEGATIVE LAST 20)
4-6 W/m2 LAST 50, -2.5 W/m2 LAST 25 (NB. values
not directly comparable to radiative forcing
estimates!) OCEANIC HEAT TRANSPORT NO GOOD
ESTIMATES OVER LAST 50 YEARS,SOME HIGH
VALUESLAST YEARS ICE EXPORT NO GOOD ESTIMATES
OVER LAST 50 YEARS,SOME HIGH VALUESLAST YEARS
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RATE OF THE SEA ICE LOSS
THE ENERGY FORCINGS PRECONDITION AND INITIATE THE
CHANGES BUT MAGNITUDE AND TIME SCALE OF THE
FOLLOWING CHANGES ARE MOSTLY RELATED TO THE
FEEDBACKS
MAIN SHORT-TERM FEEDBACKS
Water vapor feedback Lapse rate feedback Cloud
feedback Surface albedo feedback Geochemical
feedbacks Dynamical feedbacks
?
2007(?)
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THE ALBEDO FEEDBACK
CHANGE IN RADIATIVE FORCING
CHANGE IN TEMPERATURE
CHANGE IN ALBEDO
CHANGE IN MELTING
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IS THIS THE TIPPING POINT?
Is the ice-albedo effect triggering an
accelerated climate change with global
implications?
1979-2008 IPCC TREND 15 OBS TREND 30
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FRAMEWORK

1. A change in GHG results in an imbalance/forcing Q
2. The temperature responds ?Ts to restore balance

LTOA
?CO2
CO2
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Climate Feedbacks
-3.2 Planck
0.26 Albedo (snow, ice)
-0.84 Change in atmospheric temperature profile
1.80 Water Vapor
0.68 Clouds
40 from snow 35 Arctic sea ice 25 from
Antarctic ice
With albedo feedback
Without albedo feedback
Without arctic ice albedo feedback
Values from Soden and Held., 2006
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SUMMARY

• PRESENT SITUATION
• SUMMER ICE EXTENT REDUCED TWICE AS FAST AS
• PROJECTED BY IPCC LAST 30 YEARS
• ICE THICKNESS LOSS IN PROBABLY LARGE, BUT
• UNCERTAIN
• LONG TERM ICE LOSS PROBABLY DUE TO INCREASED
• LONGWAVE RADIATIVE FORCING AND INCREASED
  AND DIFFERENTLY DISTRIBUTED ATMOSPHERIC ENERGY
  TRANSPORT
• NON LINEARITIES IN ALBEDO FEEDBACK MAY BE
• IMPORTANT FOR EXTREME CHANGES IN EXTENT
• LAST FEW YEARS
• INCREASED ICE EXPORT MAY BE IMPORTANT
• TOO EARLY TO CONCLUDE THAT IPCC ESTIMATES ARE
• TOTALLY OFF, NEXT 5-10 YEARS WILL GIVE GOOD

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SUMMARY
FUTURE LONG-TERM CONTINUED LOSS DUE TO
LONGWAVE RADIATIVE FORCING NEXT DECADE OPTION
I PARTIAL RECOVERY IF ICE EXPORT AND
OCEANIC/ATM HEAT TRANSPORT STAYS NORMAL OPTION
II CONTINUED STRONG REDUCTION DUE TO NON LINEAR
ALBEDO FEEDBACK OR IF ICE EXPORT AND OCEANIC/ATM
HEAT TRANSPORT STAYS STRONGER THAN NORMAL
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SUMMARY

• GLOBAL IMPLICATIONS
• ARCTIC SEA ICE IS IMPORTANT FOR ARCTIC ECOSYSTEM
  AND CULTURE , PROBABLY NOT VERY IMPORTANT FOR THE
  GLOBE

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Thats all folks!