Thinning Arctic Sea Ice

Thinning Arctic Sea Ice

The Arctic

• “Arctic ocean basin”

• Mediterranean ocean

• Lowest measured temperature: -68C

• The most humid place on Earth (=>feels colder than it is)

• 9 to 12 (16) million sq. km

What is sea ice?

• Sea ice iceberg• Boundary layer between “warm” ocean and

cold atmosphere in the polar region• Brine rejection• Can float and accumulate

– First year ice floe– Ridges– Multi-year ice

Sea ice cycleformation

growth

deformation

disintegration

Adapted from Canadian ice service site

50 year trend

100 year trend

Measuring ice decrease

1973 Landsat 1 image 2000 Landsat 7 image

About 1440-meter retreat

Here, satellite picture of Greenland’s retreating ice cover serves as an example of using satellite images to measure ice cover from space

“Thinning of the Arctic Sea-Ice Cover” by D.A. Rothrock, Y. Yu, and G.A. Maykut, GRL 1999

• Comparison of data from 1958-1976 to data from 1990s

• Submarine data• Draft measurements : about 1.3m decrease (40%),

decrease continues at the rate of 0.1 m/year • Problems with comparison

Decrease in draft

Changes in mean draft from 1958-1976 to 1990s

“The arctic ice thickness anomaly of the 1990s: A consistent view from observations

and models” by D.A. Rothrock, J. Zhang, and Y. Yu in JGR 2003

• Model and observations demonstrate “compelling agreement”

• Model-observation disagreement in interannual variability

• Current and future situation vs. current data• Better error characterization needed for more

meaningful comparisons also incorporating the latest data from satellites

Draft: observations vs. model

Comparison of ice models

Consequences of Sea ice melting

• Negative effects on arctic animals

• Weather change in Canada: Gulf of St. Lawrence beaches exposed to winter storm waves

• Increasing coastal erosion

• Shipping and oil drilling safer

http://www.gfdl.gov/~kd/KDwebpages/NHice.html#three

Sea-ice and global warming

Arctic ice and global warming

• Positive feedback with ice melting (ice reflects 80% of the sunrays that reach it)

• Sea-ice melting => global warming OR global warming => sea-ice melting???

• Arctic region: amplification of global warming effect

• Sea-ice melting: not a contributor to the sea level rise (the melting glaciers are)