ARCTIC SEA ICE PAST, PRESENT AND FUTURE Asgeir Sorteberg, Marianne Skolem Andersen and Nils Gunnar Kvamstø

SUMMER SEA ICE EXTENT IPCC TREND: 15% OBS TREND: 30%

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

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 Estimated reserves N. Afrika Caspian Sea Middle East Rest of the world Arctic USGS estimates 25% of remaining oil/gass reserves estimated to be in the Arctic ENERGY RESOURCES

TRANSPORT 2008

CULTURAL

ECOSYSTEMS

OBSERVATIONS OF 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. ARCTIC SEA - ICE NERSC, 2009

Various regional time series back to 1900 Good quality satellite measurements of the total extent since 1979 ARCTIC SEA ICE EXTENT

OBSERVED CHANGE IN SUMMER SEA ICE EXTENT CHANGE IN SEPTEMBER ICE EXTENT RELATIVE TO MEAN (Stroeve et al 2009) Slope = (+/- 3.3)% per decade Area of lost sea ice equal to 7 times the area of Norway

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) ARCTIC SEAICE THICKNESS

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

Remote sensing (electromagnetic induction (EM) from helicopter) 2001, 2004, m below 2001 and 2004 Haas (2008) (close to North Pole) ARCTIC SEAICE THICKNESS Haas (2008)

ARCTIC SEAICE THICKNESS Submarine thickness Reduction Regional extent ( Nordic Seas, Russia ) Reduction Satellite extent Reduction Satellite Thickness ( to 81N ) No trend 2010 EM Thickness ( north Pole region ) Summer 30%, annual 8% 1 m (40%) 1m

OBSERVATIONS OF FORCING TERMS

soso L i +S i OCEANIC ENERGY BUDGET L – Latent heat; S – sensible heat Forcing terms: Ice export Ocean heat transport and heat content Surface flux Let’s see if there has been changes in some of these terms

RADIATION TERMS

Last 200 years: Last 50 years: Reconstructions of the solar irradiance

INSTRUMENTAL MEASUREMENTS EXIST SINCE 1979 (composite of several instruments) THE SOLAR MAGNETIC ACTIVITY CYCLE

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/m 2 ]

RADIATIVE FORCING FROM ATMOSPHERIC GREENHOUSE GASSES

IPCC., 2007 GREENHOUSE GASES: 2.63 W/m 2 TROPOSPHERIC OZONE: 0.35 W/m 2 SOLAR RADIATION: 0.12 W/m 2 STRATOSPHERIC OZONE: W/m 2 PARTICLES EFFECT ON CLOUDS: W/m 2 VEGETATION CHANGES: W/m 2 PARTICLES FROM POLLUTION: W/m 2 SUM: 1.65 W/m 2 RADIATIVE FORCING LAST 250 YEARS IPCC, 2007

Smedsrud and Sorteberg, 2008 HOW DOES ATMOSPHERIC ENERGY TRANSPORT AFFECT SEA-ICE? Model study ( Andersen and Sorteberg, 2009 ) indicates that the increased atm. energy flux reduced the sea ice thickness with 20% from HEAT TRANSPORT ACROSS 60ºN

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)

Input: Monthly values Time step: 1 day (Björk and Söderkvist, 2002) FORCING / PRESCRIPTIONS Lateral atmospheric and oceanic energy transport Solar rad at TOA All precip as snow Wind Ice export River run off

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)

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 Larger (non-linear) senstivity for positive summer perturbations 13 member ensemble repeated annual cycle in D. dD one month at the time Andersen and Sorteberg (2009)

Simulated annual sea ice thickness development Atmospheric energy transportIce export Andersen and Sorteberg (2009)

INCREASED NET OCEANIC ENERGY TRANSPORT INTO THE ARCTIC? 40TW 130TW 80TW 5TW 40TW Skagseth, 2008

89N, 166E 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 ) INCREASED NET OCEANIC ENERGY TRANSPORT INTO THE ARCTIC? Model study ( Smedsrud and Sorteberg, 2008 ) indicates that an increase in oceanic heatflow of 40TW (5W/m 2 ) over 10 years reduces the ice thickness with 10-15%

INCREASED NET EXPORT OF ICE OUT OF ARCTIC?

INCREASED NET EXPORT OF ICE OUT OF ARCTIC? Smedsrud and Sorteberg, 2008 Kwok, 2008

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

RADIATIVE AND DYNAMICAL FORCINGS Atmospheric heat transport Possibly high No trend Anthropogenic forcing Increased Solar Reduction Oceanic heat transport Possibly high 2010 Ice Export Increased ? ? No trend

CHANGE IN RADIATIVE FORCINGS SOLAR POSITIVE FORCING LAST 200 YEARS, NO TREND LAST W/m 2 ANTROPOGENIC POSITIVE FORCING LAST 200 YEARS, STRONG TREND LAST W/m 2 LAST 200, 1 W/m 2 LAST 50 DYNAMICALLY INDUCED CHANGES ATMOSPHERIC HEAT TRANSPORT POSSIBLE POSITIVE TREND LAST 50 YEARS (NEGATIVE LAST 20) 4-6 W/m 2 LAST 50, -2.5 W/m 2 LAST 25 (NB. values not directly comparable to radiative forcing estimates!) OCEANIC HEAT TRANSPORT NO GOOD ESTIMATES OVER LAST 50 YEARS,SOME HIGH VALUES LAST YEARS ICE EXPORT NO GOOD ESTIMATES OVER LAST 50 YEARS,SOME HIGH VALUES LAST YEARS

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(?)

CHANGE IN RADIATIVE FORCING CHANGE IN ALBEDO CHANGE IN TEMPERATURE CHANGE IN MELTING THE ALBEDO FEEDBACK

IPCC TREND: 15% OBS TREND: 30% IS THIS THE TIPPING POINT? Is the ice-albedo effect triggering an accelerated climate change with global implications?

Surface Atmosphere Space L TOA CO 2 +ΔCO 2 1.A change in GHG results in an imbalance/forcing Q 2.The temperature responds ∆T s to restore balance FRAMEWORK

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

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 INDICATIONS 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 SUMMARY

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

That’s all folks!…