- Количество слайдов: 38
Who Left the Freezer Door Open? Dr. Robert Bindschadler Hydrospheric and Biospheric Sciences Laboratory NASA Goddard Space Flight Center Robert. A. [email protected] gov
Changes in polar regions are occurring at an accelerating rate. NASA is discovering, documenting and monitoring these changes.
Remote sensing has revolutionized polar research Remote sensing is a natural solution to the remoteness, harshness and dangers of polar regions. Near-polar orbiting satellites provide denser observations of the polar regions than of mid- or lowlatitude regions.
Who has seen… • The polar regions? • beyond the Arctic or Antarctic Circles? • “midnight Sun” or aurora? • Documentary films? • “March of the Penguins” • Shackleton films or “Scott vs. Amundsen” • Cousteau documentaries • Hollywood Films? • “The Day After Tomorrow” (ugh!) • “Happy Feet” • Exhibits? • Shackleton • A Friend Acting Strangely
My Story The Cast Dollars and Sense A Double Whammy A Triple Whammy Polar Miscellany The Future
The Cryospheric Cast
Ice sheets and glaciers Primary impact: sea level Antarctica is the highest, brightest, coldest, driest, windiest continent on Earth 10% of Earth’s land area is ice-covered Ice sheets contain ~75% of all fresh water and can raise sea level 65 meters
Ice sheets and glaciers Sea ice Primary impact: heat balance (both local and global) Covers an area twice the size of the US
Ice sheets and glaciers Sea ice Snow covers up to 40% of Northern Hemisphere land in winter Seasonal snow, lake and river ice Primary impact: water resource
Permafrost Primary impact: infrastructure engineering Sea ice 20% Seasonal snow, of surface land mass islake and river ice permanently frozen
Dollars and Sense • The daily loss of land in Louisiana? – 43 acres per day (33 football fields)
Dollars and Sense • The daily loss of land in Louisiana? – 43 acres per day (33 football fields) • Cost of 1 meter rise in sea level to U. S. alone? – Approximately $400, 000, 000
Dollars and Sense • The daily loss of land in Louisiana? – 43 acres per day (33 football fields) • Cost of 1 meter rise in sea level to US alone? – Approximately $400, 000, 000 • Economic impact of an ice-free Arctic Ocean? – Priceless!! Polar regions matter!
A Double Whammy: Positive Feedbacks of Sea Ice Sea ice as a reflector bright ice—highly reflective dark ocean—highly absorptive 5 X Sea ice as an insulator Both processes amplify thermallydriven change “positive feedbacks” colder atmosphere less heat more heat warmer ocean
Decline of Perennial Arctic Pack Ice AREA 1980 1970 2002 2004 2003 Source: J. Comiso 2002, 2003 and 2005 set new records for minimal summer ice extent during the satellite era (i. e. , past 30 years) Summer minimum decreasing at 9. 2% per decade 37% of 2*CO 2 global warming caused by ice-albedo feedback
Sea Ice is Thinning Everywhere Changes in summer thickness Comparing 1958 -1976 and the 1990’s Source: D. Rothrock
Winners and Losers of Ice-Free Arctic Ocean Ice-free Arctic Ocean in summer may occur as early as 2050
Ice Sheets and Sea Level Change • Sea level rise has not been steady • Periods of fast rise – Up to 50 times present rate – Can’t be due to melting alone • Relatively steady over past 6000 yrs (2 mm/yr. ) • Rate of rise as important as magnitude
Where is the water coming from? ? Ice Sheets Ocean Thermal Expansion Glaciers and Ice Caps Present rate = 2 mm/year =3 mm/year
Sea Level Prediction • IPCC report predicts accelerating sea level rise • Probably underestimates future rates This Century? Last century
Sea Level Impact • 1/3 of the world’s population lives in the “coastal zone” • $400 billion – US only – 1 meter only
Fingerprint of Collapse What would be the signs of a collapsing ice sheet? • Thinning increasing towards coast (satellite altimetry) • Flow acceleration (In. SAR) Pine Island Gl. Thwaites Gl. Smith/Kohler Gl. • Retreat of grounding line (Landsat) • Calving of large icebergs (MODIS) All glaciers in this area exhibit these signs. All observations made by satellite sensors.
Satellite Data showing more Ice Sheet Acceleration/Thinning Change is concentrated at outlet glaciers exiting deep subglacial valleys
The Triple Whammy (part 1) Warmer ocean water melts the bases of thick outlet glaciers causing faster ice flow Cold, fresh water Warm, salty water Rapid melting More rapid ice discharge thins ice sheet and raises sea level
The Triple Whammy (part 2) Heat produces meltwater Some of this water flows along the glacier bed and accelerates ice flow Source: R. Braithwaite Greenland ice loss by melting is increasing
The Triple Whammy (part 3) Disintegrating ice shelves 2000 km 2 of Larsen Ice Shelf disintegrated in 2 days. Source: T. Scambos Glaciers feeding lost ice shelves accelerate => “ice-shelf buttressing”
Worldwide Glacier Retreat • Glaciers in all regions now retreating • Satellite data increase the quality and quantity of retreat records Retreat is accelerating Source: M. Dyurgerov
Decreasing Snow Cover 10% decrease in NH winter snow extent since 1966—primarily in springtime Source: D. Hall Global snow amount remains unknown (+50%)
Permafrost is Melting "I went to school on the mainland, and when I came back, my house was gone. ” (from Nome Nugget Newspaper)
The Day After Tomorrow Hollywood’s view of the future Sudden ice age!!? ?
The (Correct) Day After Tomorrow More heat = less ice
The (Correct) Day After Tomorrow More heat = less ice VOSTOK ICE CORE Source: R. Alley
Warnings from the Ice © MSK Partners
International Polar Year An international program of coordinated research to explore the polar regions, deepen understanding of polar interactions including their role in global climate, expand our ability to detect changes, and extend this knowledge to the public and decision makers.
Take Home Messages • Polar regions are warming faster than the rest of the planet – Multiple positive feedbacks will maintain this disproportionate response • This warming is causing major loss of ice, raising sea level and melting permafrost • Recovery is difficult and slow • Global consequences will continue and probably accelerate • NASA will continue to monitor these changes and predict their consequences
Thank you! Questions?