How Do Scientists Monitor Arctic Sea Ice?

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Scientists test their equipment on a small iceberg during the 2006 IceTrek expedition. Credit: Ted Scambos, NSIDC
Scientists test their equipment on a small iceberg during the 2006 IceTrek expedition. Credit: Ted Scambos, NSIDC

Obtaining reliable measurements of sea ice as it changes was difficult until the satellite era began in the early 1970s. Useful satellite data concerning sea ice began in late 1978 with the launch of NASA’s Scanning Multichannel Microwave Radiometer (SMMR) satellite.

Icebergs can develop into a variety of shapes as they break apart. Credit: Ted Scambos, NSIDC
Icebergs can develop into a variety of shapes as they break apart. Credit: Ted Scambos, NSIDC

Today, scientists from NSIDC primarily use to monitor Arctic sea ice, the Special Sensor Microwave/Imager (SSM/I) instrument on the Defense Meteorological Satellite Program (DMSP) satellite. The satellite passes over the polar region several times each day to gather data; researchers can then form the data into images for analysis and publication.

Sea ice can take on a variety of textures. When waves buffet the freezing ocean surface, characteristic "pancake" sea ice forms. This sea ice was photographed near Antarctica. Credit: Ted Scambos, NSIDC
Sea ice can take on a variety of textures. When waves buffet the freezing ocean surface, characteristic “pancake” sea ice forms. This sea ice was photographed near Antarctica. Credit: Ted Scambos, NSIDC

When scientists compare average sea ice conditions between years, they often use a 30-year reference period of 1981 to 2010. This reference period allows a consistent comparison of changes in extent over individual years.

The Antarctic Ice Sheet covers an area larger than the U.S. and Mexico combined. This photo shows Mt. Erebus rising above the ice-covered continent. Credit: Ted Scambos & Rob Bauer, NSIDC
The Antarctic Ice Sheet covers an area larger than the U.S. and Mexico combined. This photo shows Mt. Erebus rising above the ice-covered continent. Credit: Ted Scambos & Rob Bauer, NSIDC

Scientists monitor both Arctic and Antarctic sea ice, but Arctic sea ice is more significant to understanding global climate because much more Arctic ice remains through the summer months, reflecting sunlight and cooling the planet. Antarctica and the Arctic are reacting differently to climate change partly because of geographical differences.

Strong winds caused sea ice to crack and buckle off the coast of Greenland. Credit: Andy Mahoney, NSIDC
Strong winds caused sea ice to crack and buckle off the coast of Greenland. Credit: Andy Mahoney, NSIDC

Antarctica is a continent surrounded by water, while the Arctic is an ocean surrounded by land. Wind and ocean currents around Antarctica isolate the continent from global weather patterns, keeping it cold. In contrast, the Arctic Ocean is intimately linked with the climate systems around it, making it more sensitive to changes in climate.

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To learn more about studying sea ice, see All About Sea Ice: Studying; to explore the satellite-derived sea ice images, see the Sea Ice Index.

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