Cryosphere and Climate Change

Few countries in the world are as drastically affected by their frozen regions, or cryosphere, as Canada is. Subtle changes in our snow cover, lake, river and sea ice, glaciers and permafrost have a profound effect on everything from floods and droughts to water supplies, tourist operations, and the flow of commerce along our shipping routes. On a global scale, the cryosphere influences the world's surface energy, water cycle, and atmospheric and oceanic circulation.

For more than 20 years, scientists with Environment Canada's Meteorological Service of Canada have used satellite information to monitor and forecast changes in our cryosphere. Now, as the lead in a new Canadian Space Agency (CSA) initiative, it is working closely with the university community, private sector and other government agencies to develop, demonstrate and validate space-based systems for studying the cryosphere and its response to climate change. The new initiative builds on a decade of collaborative research on variability and change in the cryospheric system in Canada, known as CRYSYS-one of three Canadian contributions to the US National Aeronautics and Space Administration (NASA) Earth Observing System (EOS).

Although observations of the cryosphere have been made from ground, ship and aircraft for many decades, they cover small areas at a time-leaving large, often uninhabited areas uninvestigated. Satellites, on the other hand, can look at larger areas and at scales from metres to kilometres. Also, since all elements of the cryosphere are very dynamic, measurements made by satellite on a daily or weekly basis can detect changes that are overlooked by less frequent methods.

Data collected in space can be used for everything from monitoring the movement of pack ice to estimating the amount of water that will come from a seasonal snow melt. One of the greatest challenges facing scientists at present is to find a way to gauge ice thickness from space, something that is essential to understanding how climate change affects the cryosphere. Data from submarine observations indicate a dramatic thinning of sea ice in certain regions of the world-a phenomenon scientists say must be taken into consideration in modelling the future impacts of climate change.

The three-year CSA initiative is designing science and validation projects for sensors and data from Canada's RADARSAT and NASA's EOS Terr satellite, launched in 1999, and its cousin Aqua, set to head into space next summer. These will involve collecting ground and airborne measurements below the satellite's flight path to verify data, and analyzing and interpreting the results. European Space Agency satellites and products, such as the scatterometer, which detects ground freeze and thaw, are also being considered for future study. Frozen ground and permafrost play a role in the carbon cycle and may release greenhouse gases, such as methane and carbon dioxide, when they melt. The initiative is also working to establish a Canadian Cryospheric Information Network to link databases and provide public outreach.

Studies show that the cryosphere is responding quickly to changes in the climate system. In western Canada not only has there has been a decrease in the depth of spring snow-cover of up to one centimetre per year for the past 30 years, but also the snow has disappeared about one day earlier per year-a trend that has serious implications for ground freezing and thawing, as well as water supply. In 1998, when temperatures were uncommonly high, some sea-ice plugs in the Arctic archipelago opened for the first time in decades, creating the most open water since 1962. Many glaciers showed significant melting the same year, including the Athabaska Glacier, where ice-measuring stakes had to be redrilled twice as often. Other high-latitude glaciers showed more melt this year, when temperatures were cooler-an indication of lags in the system. Similar lags are being felt on large northern lakes, such as Great Slave Lake, which experienced a domino effect from a record early ice break-up and late freeze-up in 1998.

The cryosphere is a highly variable, dynamic system with complex linkages to the climate system. Improving the use of space-based systems to monitor the cryosphere will help scientists better understand the role our frozen regions play in the global climate system, and provide more accurate information for studying the impacts of changes to this system on our environment and our economy.

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