# Presentation: 467545

## Arctic Sea Ice Cover: What We Have Learned 

- Arctic Sea Ice Cover: What We Have Learned
- from Satellite Passive-Microwave Observations
- 			Claire L. Parkinson
- NASA Goddard Space Flight Center
- Presentation at the Polar Gateways Arctic Circle Sunrise 2008 Conference in Barrow, Alaska, January 25, 2008

## Global Surface Temperatures over the Last 150 Years 

- (Courtesy Jim Hansen)

## Animation of 2003 Arctic Sea Ice Coverage, from satellite data

- (Daily images)

- White: Highly compact ice.
- Shades of light blue: Ice of lesser compactness.

## Selected Impacts of Sea Ice

- Insulation

- Hindrance to ships

- Many impacts on polar life

- Reflection of solar radiation

## A Key Positive Feedback Involving Sea Ice

- Warming

- Sea ice retreat

- Reduced surface albedo

- Increased absorption of solar radiation

## Sea Ice from Satellite Visible Imageryand Its Limitations

- Landsat image of sea ice in the Weddell Sea, November 17, 1973.

- Landsat image of sea ice and clouds in the Arctic, September 5, 1972.

## Satellite Detection of Sea Ice Using Microwave Radiation: Ice/Water Emissivity Contrast

## Sample Satellite Passive-Microwave Brightness Temper-ature Images for March 1, 1999, from data from the Special Sensor Microwave Imager (SSMI)

## Arctic Sea Ice Concentrations, March 1, 1999 Derived from Satellite Passive-Microwave Data

- The values mapped are sea ice concentrations (percent areal coverages of ice).

## Key Satellite Passive-Microwave Instruments

- NASA Nimbus 5 Electrically Scanning Microwave Radiometer (EMSR), launched December 1972.
- NASA Nimbus 7 Scanning Multichannel Microwave Radiometer (SMMR), launched October 1978.
- DMSP Special Sensor Microwave Imager (SSMI), first launched June 1987.
- Japan Aerospace Exploration Agency (JAXA) Advanced Microwave Scanning Radiometer for the Earth Observing System (AMSR-E) on NASA’s Aqua spacecraft, launched May 2002.

-        (Arctic sea ice, March 1, 2003, from Aqua AMSR-E data; image from T. Markus)

## Winter and Summer Arctic Sea Ice Coverages Derived from Satellite Passive-Microwave Data

- The values mapped are sea ice concentrations (percent areal coverages of ice).

## Monthly Arctic Sea Ice ExtentsNovember 1978 – December 2006

- (from Parkinson and Cavalieri, 2008)

## Monthly Arctic Sea Ice Extent DeviationsNovember 1978 – December 2005

- (extended from Parkinson, Cavalieri, Gloersen, Zwally, and Comiso, 1999)

## Arctic September Sea Ice Concentra-tions, 1979-2003, illustrating interannual variability

- (from SMMR and SSMI data)

## Length of the Northern Hemisphere Sea Ice Season, 2004

- (updated from Parkinson 2000a)

## Trends in the Length of the Sea Ice Season1979 - 1986

- (recolored from Parkinson 1992)

## September 14, 2007 Arctic Sea Ice Distribution vs. Minima in 2005 and Averaged over 1979-2006

- (from Comiso, Parkinson, Gersten, and Stock, 2008)

## (from Comiso, Parkinson, Gersten, and Stock, 2008)

## (from Comiso, Parkinson, Gersten, and Stock, 2008)

## Satellite-Derived Reduction in Arctic Sea Ice Coverage since November 1978

- Decreases in the areal coverage of the ice
- Marked decreases in all seasons
- Marked decreases in most regions (with none of the regions having overall increases)
- Decreases in the length of the sea ice season

## Sample Consequence: Polar Bear Impact in Western Hudson Bay

- Earlier ice breakup, forcing earlier polar bear retreat to land.
- Average weight of adult female polar bears in Western Hudson Bay: 295 kg in 1980, 230 kg in 2004.
- Western Hudson Bay polar bear population: about 1,200 in 1989, about 950 in 2004.

- (Robert Taylor)

- Sea ice coverage on April 29, 2006 (left) and November 14, 2005 (right), from Aqua’s AMSR-E satellite data

- Date when ice concentration in western Hudson Bay first reaches ≤ 50%, from Stirling and Parkinson (2006).

## Thinning of the Arctic Sea Ice Coveras determined by Rothrock, Yu, and Maykut from submarine data

- (from Rothrock et al. 1999)

- Mean ice draft:
-    1958-1976 –  3.1 m
-    1993-1997 –  _1.8 m_
-         Thinning:  1.3 m,
-         or 40% (later
-         adjusted down).

- Small dots are the original data points; triangles and squares have been seasonally adjusted to September 15.

## Laser Altimetry from the Ice, Cloud, and Land Elevation Satellite (ICESat)

- (schematic from the ICESat Science Team)

## Broader Context

- Impacts of the Ice Decreases
- Helpful to shipping and to some marine life
- Harmful to polar bears, some seal species, walruses, Arctic foxes, and other wildlife dependent on the ice
- Enhances warming, through feedbacks
- Other Arctic Changes
- Rising temperatures
- Declining snow cover
- Thawing permafrost
- Diminishing lake and river ice
- Melting glaciers
- Melting Greenland Ice Sheet
- Antarctic Sea Ice Changes
- Major decreases in the 1970s
- Increases overall since 1978
- Good regional ice/temperature correspondence

-  July 24, 1909

-  August 13, 2004

-  (photos courtesy Jim Tucker)

- Retreat of Alaska’s Holgate Glacier

## Southern Ocean Sea Ice Decreases in the 1970s 

- 12-month running mean of sea ice area (bottom curve) and of ocean area with ice concentrations exceeding 1 octa (top curve) and 4 octas (middle curve). (Figure from Kukla and Gavin 1981.)

- Area (106 km2)

- 1973     1974     1975     1976     1977     1978     1979

## 30-Year Record of Southern Ocean Sea Ice Extents, 1973-2002

- (from Cavalieri, Parkinson, and Vinnikov 2003)

## Summary

- Arctic sea ice over the past 3 decades: clear overall decreases in every month, although with considerable interannual and regional variability.
- Multiple impacts of the ice decreases: climate feedbacks, impacts on wildlife and human activities.
- Contrast with Antarctic sea ice, which has increased overall since 1978.
- Likely future: continued ice decreases in the Arctic, eventual ice decreases in the Antarctic.
- Uncertainties: scientists do                                          not fully understand the                                             observed changes, making                                           future surprises likely.

- Seas of Okhotsk and Japan