Hydrological Cycle

The transport of water in the Arctic is significantly different from that in other parts of the globe. While much of the water is frozen most of the time, ambient temperatures in the Arctic are close to the melting point of snow and ice. Therefore, freeze-thaw cycles of sea ice, snow, permafrost, and glacial ice constitute important elements of the northern hydro-logical cycle. Melting and freezing also influence runoff and the riverine input (including the input of various trace materials) into the ocean. The extended shelf areas along the Arctic coasts comprise about 25% of the world's continental shelf regions and are strongly affected by the freshwater influx. The freshwater discharge also controls the formation of near-coastal sea ice and thus the regional albedo and the global radiation balance. Increased freshwater input to the oceans from melting ice would lower surface densities and could slow down thermohaline circulation. The strong seasonality of terrestrial water transport has a bearing on biospheric processes through the varying delivery of important nutrients (AMAP, 1998).

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