Seaice research International Polar Year and looking to the future

Research on sea ice is a strong focus in the programme of the International Polar Year (2007-2008), with many nations combining resources and expertise to collaborate on large-scale studies aimed at furthering understanding of sea ice, oceans and the atmosphere. These research campaigns involve integration of in situ observations and use of modern technology (automatic sensors, autonomous drifters and floats, and satellites), along with improved climate modelling.

Further development of satellite sensor technology is underway, and this should soon result in higher accuracy and better spatial and temporal resolution of measurements33,34. The new ice-specialist satellite CryoSat-2 (Figure 5.12), to be launched in 2009, and new developments beyond that, will hopefully lead to a much better capacity to observe and understand the status of Arctic and Antarctic sea ice and the processes and factors controlling it.

Figure 5.12: CryoSat-2, artist's impression. CryoSat-2, to be launched in 2009, will improve monitoring of ice thickness. Its altimeter measures distances to sea ice and open water and the difference between the two is used to derive ice thickness Illustration: ESA - AOES Medialab

Sea-ice research

Photo: Sebastian Ge

shelf seas, the East Siberian Sea and the Laptev Sea. There, sea ice forms during the Arctic autumn and winter, grows thicker and joins the transpolar drift towards and over the North Pole. Finally, after some two to seven years, the ice floe enters Fram Strait. This transport of ice influences, among other things, the processes governing ocean circulation and the flow of nutrients in Arctic marine ecosystems.

Many factors influence the formation, evolution and degradation of sea ice. Monitoring and research is underway to improve understanding of these factors, how they are linked, and the influence of climate change (see boxes on sea ice research).

Large parts of the Arctic are characterized by complex, multi-year ice35. During Arctic summers, ponds form as snow melts on the ice surface. In autumn the melt

Figure 5.13: Several metre-high pressure ridge on a multi-yearsea ice floe in Western Fram Strait.

Photo: Sebastian Cerland, Norwegian ___ Polar Institute

Figure 5.13: Several metre-high pressure ridge on a multi-yearsea ice floe in Western Fram Strait.

Photo: Sebastian Cerland, Norwegian ___ Polar Institute ponds freeze over, snow falls on the surface and new ice forms at the underside of the ice floe. Individual floes freeze together to form larger floes. Rafting and ridging occurs (Figure 5.13) and leads (narrow channels of open water) are formed. Ridges, which can be several metres high, and ice keels, which can extend more than 20 m below sea level, affect wind drag and water drag. Dust and sediments are incorporated into snow and ice through atmospheric and oceanic processes, and ice algae and other organisms colonize the brine channels and the under-sides of ice floes.

In the Southern Hemisphere sea-ice conditions are very different. The Southern Ocean surrounds the Antarctic continent, in contrast to the Arctic Ocean, which is surrounded by land. Since the highest latitude areas in the south are land covered, Antarctic sea ice is on average further away from the South Pole than is Arctic sea ice from

the North Pole. During the Antarctic summers, most sea ice breaks up, drifts northward and eventually melts. Consequently, most Antarctic sea ice is first-year ice.

Snow plays an important role in the formation and nature of sea ice in both polar regions, and changes in patterns of precipitation, both as snow and as rain, will have impacts on sea ice. Young ice without a snow cover thickens faster than young ice with an insulating snow cover. Snow properties such as grain shapes and sizes influence the snow's albedo, and the extent and properties of snow are the dominating factors controlling how much energy in the form of solar radiation reaches the ice. Snow can also contribute to the ice mass through transformation into ice. Superimposed ice forms when mild weather melts snow at the surface, or when rain falls. Water percolates downwards through the snow cover and reaches the snow-ice transition zone where it is cold enough that the snow-water mixture freezes. Snow can also be added to ice when seawater seeps into the snow-ice transition through cracks in the ice or from the side of an ice floe, resulting in "snow ice".

Changes in wind strength and wind patterns would also affect many characteristics of sea ice. More wind or more extreme wind events would lead to more ice rafting and ridging and increased ice thickness in some areas. Changes in winds would especially affect coastal areas. Land-fast ice formation and evolution is highly dependent on winds. Ice conditions in bays, fjords and sounds especially will be substantially different in a climate with different wind patterns than at present.

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