ARCTIC SEA ICE

PAST, PRESENT AND FUTURE

Asgeir Sorteberg, Marianne Skolem Andersenand Nils Gunnar Kvamstø

Asgeir.Sorteberg@gfi.uib.no; Nils.Kvamsto@gfi.uib.no

SUMMER SEA ICE EXTENT

1979-2008IPCC TREND: 15% OBS TREND: 30%

QUESTIONS

• PREDICTIONS – WILL THIS CONTINUE?

• UNDERSTANDING OF THE PROCESSES

• ENVIRONMENTAL AND SOCIO-ECONOMIC IMPACT

1: Barents Sea2: Southern Kara Sea and West Siberia3: Northern Kara Sea4: Laptev Sea5: East Siberian Sea6: Chuchi Sea7: Alaska North Slope8: East Greenland

Estimated reserves

N. AfrikaCaspian SeaMiddle East

Rest ofthe world

Arctic

8

3

2

1 4

5

67

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 areathe 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 1900Good 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 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

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)

• 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)

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)

ARCTIC SEAICE THICKNESS

Haas (2008)

ARCTIC SEAICE THICKNESS

1950 1975 2000

Submarinethickness

Reduction

Reduction

Regional extent(Nordic Seas, Russia)

Reduction

1900 1990

Satellite extent

Reduction

SatelliteThickness (to 81N) No trend

2010

EMThickness (north Pole region)

Summer 30%, annual 8%

1 m (40%)

1m

OBSERVATIONS OF FORCING TERMS

sfcioioiE

EHsfcsfc

FFFSSLtt

O

QQRF

so

Li +Si

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 someof these terms

RADIATION TERMS

2

2

/m W2.0

W/m2 to25.0

d

d

S

SLast 200 years:Last 50 years:

Reconstructions of the solar irradiance

INSTRUMENTAL MEASUREMENTS EXIST SINCE 1979(composite of several instruments)

THE SOLAR MAGNETIC ACTIVITY CYCLE

2 W/m0 solarQ

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]

2 W/m2.0 to05.014

stratosd

solar absS

Q

RADIATIVE FORCING FROMATMOSPHERIC GREENHOUSE GASSES

IPCC., 2007

GREENHOUSE GASES: 2.63 W/m2

TROPOSPHERIC OZONE: 0.35 W/m2

SOLAR RADIATION: 0.12 W/m2

STRATOSPHERIC OZONE: -0.05 W/m2

PARTICLES EFFECT ON CLOUDS: -0.70 W/m2

VEGETATION CHANGES: -0.20 W/m2

PARTICLES FROM POLLUTION: -0.50 W/m2

SUM: 1.65 W/m2

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 1970-1990

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 transport Ice export

Andersen and Sorteberg (2009)

INCREASED NET OCEANIC ENERGY TRANSPORT INTO THE ARCTIC?

40TW130TW

80TW

5TW

40TW

Skagseth, 2008

89N, 166E

Possibly more oceanic heat transportlast 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/m2) 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 trendin 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 10years will reduce ice thicknesswith 15-20%, but have large impacton year-to-year variability

RADIATIVE ANDDYNAMICAL FORCINGS

1950 1975 2000

Atmospheric heat transport

Possibly high

No trend

Anthropogenicforcing

Increased

1900 1990

Solar

Reduction

Oceanic heattransport Possibly

high

2010

Ice Export

Increased

Increased

?

? No trend

No trend

CHANGE IN RADIATIVE FORCINGS

SOLARPOSITIVE FORCING LAST 200 YEARS, NO TREND LAST 50

0.05-0.2 W/m2

ANTROPOGENICPOSITIVE FORCING LAST 200 YEARS, STRONG TREND LAST 50

1.5 W/m2 LAST 200, 1 W/m2 LAST 50

DYNAMICALLY INDUCED CHANGES

ATMOSPHERIC HEAT TRANSPORTPOSSIBLE 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 TRANSPORTNO GOOD ESTIMATES OVER LAST 50 YEARS,SOME HIGH VALUES

LAST YEARS

ICE EXPORTNO 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 feedbackLapse rate feedback

Cloud feedbackSurface albedo feedbackGeochemical feedbacksDynamical feedbacks

?

2007(?)

CHANGE IN RADIATIVE FORCING

CHANGE IN ALBEDO

CHANGE INTEMPERATURE

CHANGE INMELTING

THE ALBEDO FEEDBACK

1979-2008IPCC 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 T

OA

CO2+ΔCO2

pS 14

0

ii

SS

QTTQ

1. A change in GHG results in an imbalance/forcing Q2. The temperature responds ∆Ts to restore balance

4AT

FRAMEWORK

Climate Feedbacks

-3.2

Planck

1.80

WaterVapor

0.68

Clouds

0.26

Albedo(snow, ice)

-0.84

Change in atmospherictemperature

profile

Values from Soden and Held., 2006

albedocloudwaterLapsePlanckeqs

QT

,

40% from snow35% Arctic sea ice25% from Antarctic ice

C8.2, eqsT

C65.2, eqsT

C4.2, eqsT

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 TONON 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!…