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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 - PowerPoint PPT Presentation
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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)