Subsurface baroclinic eddies in the Arctic Ocean have a diameter of 10–20 km and are confined in depth between 50 and 300m. During the Arctic Ice Dynamics Joint Experiment (AIDJEX) in the central Beaufort Sea between March 1975 and May 1976, extensive information on eddy characteristics, statistics, and behavior was collected from four manned drifting ice camps. During this 14‐month period, 146 eddies were encountered, of which 19 were found to be repeated crossings, making a total of 127 separate eddies observed during this period. On the basis of the 1975–1976 AIDJEX data set, it is concluded that eddies are (1) prevalent in the Amerasia Basin of the Arctic Ocean and, in particular, the Beaufort Sea where they may occupy up to a quarter of the available surface area, (2) located in the depth range of 50–300 m (although a few deeper eddies are also present), (3) the second largest producers (32%) of kinetic energy found within the upper 200 m of the Beaufort Sea, and (4) predominantly anticyclonic in rotational tendency. These eddies apparently originate north of Point Barrow, Alaska, as a result of instability in the eastward flowing Alaskan Coastal Current and transfer seasonally varying water properties from the Chukchi Sea and Alaskan Shelf into the Arctic Ocean. They appear to translate in response to barotropic forcing over short time scales and, over longer time periods, move with the mean geostrophic field. The season of formation for an eddy may be identified by the anomalous thermal properties still residing in its core.
Atlantic Water (AW) supplies the largest source of heat, mass, and salt to the Arctic Ocean via Fram Strait (Greenland‐Spitsbergen Passage), yet it represents only a fraction of the Atlantic Water that resides in the Greenland, Iceland, Norwegian, and Barents Seas. This is a result of both the branching of the central core of AW along its northward flow and the modification of its T‐S signature through air‐sea‐ice interactions and internal mixing. This paper addresses the quantitative analysis of the three dominant Atlantic Water cores within Fram Strait and north of 76°N using an 11‐year (1977 to 1987) hydrographic database. Spatial variations of heat, volume, and salt along its flow path of some 600 km showed that the major core of Atlantic Water that directly enters the Arctic Ocean (Svalbard branch) did not extend past 20°E. Of the 9719 km3 of Atlantic Water existing within the region, one third resided within the Svalbard branch; the remainder, 22% and 45%, were held within the Return Atlantic Current and the Yermak branches, respectively. Restricting the analysis to a southern limit of 79°N effectively removed the Return Atlantic Current and showed a nearly equal split between the two remaining branches. Work completed by Bourke et al. (1988) indicated that the Yermak branch is largely recirculated to the south; if true, this analysis supports Rudels' (1987) model estimate of a 50% recirculation of AW within this region.
During the summer Marginal Ice Zone Experiment in Fram Strait in 1983 and 1984, fourteen mesoscale eddies, in both deep and shallow water, were studied between 78 ø and 81øN. Sampling combined satellite and aircraft remote sensing observations, conductivity-temperature-depth observations, drift of surface and subsurface floats and current meter measurements. Typical scales of these eddies were 20-40 km. Rotation was mainly cyclonic with a maximum speed, in several cases subsurface of up to 40 cm s-• Observations further suggest that the eddy lifetime was at least 20 to 30 days. Five generation sources are suggested for these eddies. Several of the eddies were topographically trapped, while others, primarily formed by combined baroclinic and barotropic instability, moved as much as 10-15 km d -• with the mean current. The vorticity balance in the nontrapped eddies is dominated by the stretching of isopycnals accompanied by a change in the radial shear. In the most completely observed eddy south of 79øN the available potential energy exceeded the kinetic energy by a factor of 2. Quantitative estimates suggest that the abundance of these eddies enhances the ice edge melt up to 1-2 km d-• !. INTRODUCTION The marginal ice zone (MIZ) is the transition region from open ocean to pack ice. Here strong mesoscale air-ice-ocean interactive processes occur which control the advance and retreat of the ice margin. To gain better understanding of these processes, the 1984 Marginal Ice Zone Experiment (MIZEX '84) was carried out in Fram Strait between Greenland and Svalbard from May 18 to July 30, !984, following a preliminary summer experiment in 1983 I-MIZEX Group, 1986]. One of the central objectives of MIZEX is to understand the physics of mesoscale eddies and their importance in the various exchange processes of mass, heat, and momentum which affect the position of the ice edge. Major investigations of mid-ocean eddies started in 1973 with the Mid-Ocean Dynamics Experiment (MODE) 1 program [Robinson, 1983]. Although it is now well established that eddies are present in all the world oceans with important implications for physical, biological, chemical, and geological oceanography and acoustics [Robinson, 1983; Maqaard et al., 1983], eddy features have not been extensively investigated in the MIZ. To qualitatively demonstrate the effect of eddies in the MIZ, a unique aerial photograph obtained on June 30, 1984 is shown in Plate 1, where the ice traces the cyclonic orbital motion of an eddy at the ice edge. (Plate 1 is shown here in black and white. The color version can be found in the separate color section in this issue.) Such motion advects large amounts of ice, Polar Water (PW), and Atlantic Water (AW) into closer contact, causing enhanced floe breakup and ice melting. While Plate 1 shows one ice edge eddy in detail, the National Oceanic and Atmospheric Administration (NOAA) satellite image from July 1, 1984 (Plate 2) establishes that eddies and meanders are the dominant features along the ice edge under moderate wind con...
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