RESEARCH HIGHLIGHT

View from Above: Satellite Monitoring of the Arctic Ice Cap

September 1, 2004

Arctic sea ice is one of the fundamental components of the Earth's climate system. In the study of climate change, it is important to understand the life cycle of sea ice and its relationship with the Earth's atmosphere. There is a complicated mechanism of interaction between arctic sea ice and Earth's atmosphere: ice is affected by air pressure and climate variations and, in turn, affects the amount of heat, moisture, and solar radiation that is reflected back into the atmosphere. This reflection is defined by an important ice parameter that is known as ice albedo. The life cycle of sea ice is characterized by thermodynamic (melting, freezing, absorbing, and releasing heat) processes and dynamic processes (motion, deformation, rafting, ridging , etc).

Satellite monitoring has added another dimension to the study of arctic sea ice. Monitoring is one of the most effective sources of data for arctic ecological research because of its ability to monitor environmental activity that other conventional methods may not detect.

Over the last decade, satellite monitoring has revealed changes and trends in the sea ice and is being used to compare and correlate results with other sources. Long-term arctic satellite measurements began in the early 1970's with the polar-orbiting weather Landsat and Nimbus satellites. These satellites used optical passive systems to measure the radiation from the Earth's surface and the atmosphere. Today, multispectral optical systems, such as the Advanced Very High Resolution Radiometer (AVHRR), are also used for arctic research. However, darkness or cloud cover in the Arctic can obstruct the satellite's ability to gather data. Active (radar) and passive (radiometer) microwave satellite sensors have provided another monitoring option and they are not dependent on sunlight or restricted by clouds, fog, or precipitation.

Visiting IARC scientist Gennady Belchansky ,from the Institute of Ecology, Russian Academy Sciences, is doing perennial studies of the seasonal distribution of perennial sea ice using active and passive microwave satellite sensors in the United States, Japan, and Russia. He works with the Ecology study group at the Russian Academy of Sciences and research wildlife biologist David Douglas of the USGS Alaska Science Center in Juneau, Alaska. They are gathering data to project the annual dates of melting and freezing (Figure), ice surface temperatures, atmospheric air patterns, and sea ice motion, distribution, and long-term trends. These studies will provide information about seasonal changes in ice concentration, thickness and mass, and sea-ice albedo, and can be used to model the interaction between the dynamic forces of air circulation, sea ice motion, and ice melting.

Their research can also work in conjunction with the Arctic Ocean Model Intercomparison Project (AOMIP) at IARC, which is examining models that simulate the seasonal activity of the Arctic Ocean.

Variations in sea ice cover are part of the natural process of change on earth. It is difficult to determine the extent these variations are due to natural forces or human influence; this is an important question to pursue. During the last three decades, arctic sea ice has been decreasing and this decrease affects the climate as well as the ecological environment.

Satellite monitoring can also provide important information for ecological researchers of the Arctic and sub-Arctic regions. Ecologists are working on questions that need data about regional, continental, and global changes so they can develop an understanding of both short and long-term consequences. These new methods of obtaining data based on advance satellite technologies can monitor arctic marine mammals (polar bear, walrus and other) and their sea-ice habitats and show their relationship to climate change.

These maps show passive microwave satellite data of the onset dates of snow melting and freezing and melt season duration of the arctic sea ice for 25 years from 1979-2003.