The Arctic Sea Ice Cover

From the Living Earth

• Frozen ocean• 8-15 million km2

• Size of U.S.• Meters thick• Floating, moving ice• Highly variable• Large albedo

Interface, Impediment, Integrator

Why importantExploration Economic

Climate change• Canary in a coal mine• Amplifier of changeMilitary

Climate change!

What are the major sea ice questions?

• How much ice is there?• areal extent• thickness

• How much snow is there?• How does the ice move?• What is its mass balance?• Where does the sunlight go?• What are its properties?• How does it interact with other components?

• Determine the extent of the ice cover• Determine the redistribution of the ice cover due to dynamics and thermodynamcs• Measure the export of ice from the Arctic basin• Determine the snow depth and the ice thickness

• Which Arctic changes reflect basin-wide, decadal, and long-term processes? • How are they coupled?• Have Arctic feedbacks amplified these changes?• What are the future Arctic change scenarios?

• Is Arctic change related to the Arctic Oscillation?• Is Arctic change a component of climate change?• Are feedbacks critical to Arctic change?• Do physical changes greatly impact Arctic ecosystems and society?

• Assess large-scale Arctic environmental change.• Conduct scientific exploration of polar frontiers.• Observe polar regions in depth.• Understand human-environmental dynamics.• Create new connections between science and public.

How are these quantities changing?

What do we need to measure?• Ice extent• Thickness distribution• Snow depth distribution• Ice motion• Temperature• Mass balance • Albedo and transmission• Environmental forcing

(ocean and atmosphere)

Spatial and temporal variability make it difficult

What tools do we have?

• Archived data• Field experiments

• camps• cruises• submarines

• Remote sensing• IPS• aircraft• satellites

• Models• process• discrete element• large-scale ice• GCM

Ice tethered buoys!

What is the ice extent?• Satellites

March September

Ice extent is decreasing

How thick is the ice?

• Rothrock et al. show thinning everywhere!• Average decrease was 40% from 3 m to under 2 m• Tucker et al. show similar results for spring

Changes in summer thicknessComparing 1958-1976 and the 1990’s

• Submarines• Moorings• Surface obs• Satellites?

Sea ice is thinning everywhere

How much snow is there?• Surface obs• Buoys• Satellites?

0 25 50 75 100 1250.00

0.01

0.02

0.03

0.04

0.05

Spring 199821,169 points33.7 cm mean19.3 std. dev.

Freq

uenc

y (%

)Snow depth (cm)

10/10 11/24 1/8 2/22 4/8 5/23 7/70

10

20

30

40

19981997D t

Ave

rage

dep

th (c

m)

Seasonal evolution and large spatial variability

How does the ice move? • Buoys• Satellites

Variations due to changes in forcing

What is the mass and heat budget?• Surface obs• Buoys

10/10 12/10 2/10 4/10 6/10 8/10 10/10-200

-150

-100

-50

0

50

100

First year 0.7 to 1.5 m 1.5 to 2.25m above 2.25 m

Date

Cha

nge

in ic

e th

ickn

ess

(cm

)

Manned camp

Autonomous buoy

0

25

50

75

Tota

l mel

t (cm

)

Snow melt Surface melt Bottom melt

1957 1958 1959 1975 1994 1998 2000 2002

Large variability: spatial and interannual

Where does the sunshine go?• Surface obs• Buoys

Seasonal variability, melt ponds are the key.

What are the ice properties?• Surface obs• Buoys• Satellites

Ice properties impact all parameters

How does it interact?• Surface obs

Much work to do.

Ice tethered systems: ice measurements1. Air temperature2. Ice temperature3. Upper ocean temperature4. Snow depth5. Ice thickness6. Ice mass balance7. Surface conditions8. Solar partitioning9. Ice position

1. Thermistors2. Thermistors3. Thermistors4. Acoustic sensor5. Acoustic sensor6. Acoustic / thermistors7. Web cams – above,below8. Spectroradiometers9. GPS

Ice tethered systems can make major contributions

Sample ice buoy results

0

-10

-20

Almost as good as being there.

Spatial variability

Snow depth, ice thickness, ice conditions

What good is a point measurement?

0.0

0.1

0.2

0.3

0.4

-150 -100 -50 00.0

0.1

0.2

0.3

0.4

Fra

ctio

n

Surface melt

Total melt (cm)

Fra

ctio

n

Bottom melt

Pretty good if… you carefully select location

Smart motes

Snow-ice interface temperature tells all

Installation measurement festival

Explore spatial variability

• Aerial photographs • Snow depth• Pond depth• Ice thickness• Surface types

Characterize area during buoy installation

Remember outreach

Classroom visits, media outreach, web cams and pages

Integration coordination, and synthesis

Ice tethered buoys Satellites

Field studies

Models

3 levels of coordination and integration

• Integrate all buoy elements (ice, ocean, atmosphere, biology, geochemistry).

• Integrate tethered buoys with other components of an Arctic Ocean observing system (satellites, moorings, stations)

• Coordinate with other studies (process studies, field studies, models)

• Collaborate with other efforts• Synthesize results

Integration is the key

Summary

• How much ice is there?• areal extent• thickness – Yes!

• How much snow is there? – Yes!• How does the ice move? – Yes!• What is its mass balance? – Yes!• Where does the sunlight go? – Yes!• What are its properties? – Yes!• How does it interact with other components? – Yes!

Can ice tethered buoys help answer the questions – YES!

SEARCH ice mass balance activities

• Sponsored by NOAA and NSF• Ice mass balance buoys • Deployments defined by

• Maximum coverage• Models and observations

• Eight buoys this year• Expected life 1-3 year • Coordinated with moorings

• Ocean instruments• Ice profiling sonar

• Collaboration with other efforts

Location, location, location

Mass balance observations

Beaufort Sea

05101520253035

Snow

-40

-30

-20

-10

0

Air t

empe

ratu

re (o C

)

-300

-250

-200

-150

-100

-50

0

50

Ice

Water

Ocean heat flux (W

m-

Dep

th (c

m)

2)

n 20 Aug 20 Oct 20 Dec 20 Feb 20Apr 20 Ju-1.9

-1.8

-1.7

-1.6

-1.5

-1.4

Wat

er te

mpe

ratu

re (o C

)

North Pole

20001993 - 1994 1997 - 1998 2002

Autonomous field experiment in a box