CHANGES IN TEMPERATURE AND TRACER DISTRIBUTIONS WITHIN THE ARCTIC-OCEAN - RESULTS FROM THE 1994 ARCTIC-OCEAN SECTION

Major changes in temperature and tracer properties within the Arctic O cean are evident in a comparison of data obtained during the 1994 Arct ic Ocean Section to earlier measurements. (1) Anomalously warm and wel l-ventilated waters are now found in the Nansen, Amundsen and Makarov basins, with the largest temperature differences, as much as 1 degrees C, in the core of the Atlantic layer (200-400 m). This thermohaline t ransition appears to follow from two distinct mechanisms: narrow (orde r 100 km), topographically-steered cyclonic flows that rapidly carry n ew water around the perimeters of the basins; and multiple intrusions, 40-60 m thick, which extend laterally into the basin interiors. (2) A ltered nutrient distributions that within the halocline distinguish wa ter masses of Pacific and Atlantic origins likewise point to a basin-w ide redistribution of properties. (3) Distributions of CFCs associated with inflows from adjacent shelf regions and from the Atlantic demons trate recent ventilation to depths exceeding 1800 m. (4) Concentration s of the pesticide HCH in the surface and halocline layers are supersa turated with respect to present atmospheric concentrations and show th at the ice-capped Arctic Ocean is now a source to the global atmospher e of this contaminant. (5) The radionuclide I-129 is now widespread th roughout the Arctic Ocean. Although the current level of I-129 level p oses no significant radiological threat, its rapid arrival and wide di stribution illustrate the speed and extent to which waterborne contami nants are dispersed within the Arctic Ocean on pathways along which ot her contaminants can travel from western European or Russian sources. (C) 1998 Elsevier Science Ltd. All rights reserved.