Recent environmental changes in the Arctic: A review

Numerous recent observations indicate that the Arctic is undergoing a signi ficant change. In the last decade, the hydrography of the Arctic Ocean has shifted, and the atmospheric circulation has undergone a change from the lo wer stratosphere to the surface. Typically the eastern Arctic Ocean, on the European side of the Lomonosov Ridge, is dominated by water of Atlantic or igin. A cold halocline of varying thickness overlies the warmer Atlantic wa ter and isolates it from the sea ice and surface mixed layer. The western A rctic Ocean, on the North American side of the Lomonosov Ridge, is characte rized by an added layer of water from the Pacific immediately below the sur face mixed layer. Data collected during several cruises from 1991 to 1995 i ndicate that in the 1990s the boundary between these eastern and western ha locline: types shifted from a position roughly parallel to the Lomonosov Ri dge to near alignment with the Alpha and Mendeleyev Ridges. The Atlantic Wa ter temperature has also increased, and the cold halocline has become thinn er. The change has resulted in increased surface salinity in the Makarov Ba sin. Recent results suggest that the change also includes decreased sm-face salinity and greater summer ice melt in the Beaufort Sea. Atmospheric pres sure fields and ice drift data show that the whole patterns of atmospheric pressure and ice drift for the early 1990s were shifted counterclockwise 40 degrees -60 degrees from earlier patterns. The shift in atmospheric circul ation seems related to the Arctic Oscillation in the Northern Hemisphere at mospheric pressure pattern. The changes in the ocean circulation, ice drift , air temperatures, and permafrost can be explained as responses to the Arc tic Oscillation, as can changes in air temperatures over the Russian Arctic .