ISSN:0148-0227    

DOI:10.1029/JC092iC07p06715

年代:1987

数据来源: WILEY

摘要:

A marginal ice zone (MIZ) occurs where polar and temperate climate systems interact to form a transition between open ocean and pack ice regimes. This transition is characterized by large horizontal gradients in the properties of the ice, ocean, and atmosphere. As a geophysical boundary, the MIZ is unique in the complexity of the vertical and horizontal air‐sea‐ice interactions which take place there. Over a seasonal cycle, the ice edge can migrate hundreds of kilometers north and south to produce large variations in maximum and minimum ext

ISSN:0148-0227    

DOI:10.1029/JC092iC07p06716

年代:1987

数据来源: WILEY

摘要:

The pattern of large‐scale circulation in Fram Strait during summer 1984 is inferred from hydrographic data and water mass analysis and direct current observations by use of surface and subsurface floats. The West Spitsbergen Current carrying warm and salty Atlantic water splits into several branches, two flowing northward into the Arctic Ocean and two turning westward, causing a recirculation across the main axis of Fram Strait. The individual flow paths are topographically controlled, suggesting a strong barotropic component of the circulatio

ISSN:0148-0227    

DOI:10.1029/JC092iC07p06719

年代:1987

数据来源: WILEY

摘要:

The water masses and circulation over the northern Greenland continental shelf are described based on two cruises to the region during the summers of 1979 and 1984. The cold Polar Water over the shelf was found to increase notably in salinity toward the shelf break and the East Greenland Polar Front. A colder, more saline, and relatively isolated fraction of the Polar Water was identified just above the Atlantic Intermediate Water of the front. A middepth layer, stable in time, indicates little vertical heat exchange. Warm Atlantic Intermediate Water was found to intrude close to the coast via a newly defined system of troughs in the shelf. The Polar Water was found to circulate over the shelf in a clockwise gyre. Baroclinic transports, northward near the coast with 0.58‐Sv mean flow and southward elsewhere with 1.47‐Sv mean flow, yielded a net southward transport in the East Greenland Current of 0.89

ISSN:0148-0227    

DOI:10.1029/JC092iC07p06729

年代:1987

数据来源: WILEY

摘要:

Four weeks of concurrent temperature and current observations from three moorings across the East Greenland Polar Front, at approximately 78°40′N, showed pronounced differences between the current regimes on either side of the front. East of the front, vertical shear was minimal, mean flow was not statistically significant, and fluctuations showed evidence of wind influence. West of the front, vertical shear and southward mean flow were significant; however, observed fluctuations were not strongly influenced by local winds. The mean current and density structure of the front was similar to that of a two‐layer boundary current model with constant potential vorticity. Current fluctuations west of the front were in part related to mesoscale features generated farther north and subsequently advected downstream by the East Greenland Current or to eddylike features apparently generated through potential vorticity conservation. Local instabilities of the front most likely account for the remainder of the mesoscale variability seen in the rec

ISSN:0148-0227    

DOI:10.1029/JC092iC07p06741

年代:1987

数据来源: WILEY

摘要:

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° and 81°N. 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−1. 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−1with 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 79°N 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

ISSN:0148-0227    

DOI:10.1029/JC092iC07p06754

年代:1987

数据来源: WILEY

摘要:

A warm, 60‐km‐diameter cyclonic eddy was observed in late summer 1984 in the vicinity of the Molloy Deep at the eastern edge of the East Greenland Current. Depression of isotherms to at least 900 m indicates a deep‐reaching baroclinicity. Maximum baroclinic speeds of 0.1 to 0.17 m/s are estimated, as is a swirl transport of

ISSN:0148-0227    

DOI:10.1029/JC092iC07p06773

年代:1987

数据来源: WILEY

摘要:

The biomass and primary productivity of phytoplankton assemblages from the marginal ice zone of the Fram Strait were investigated during June‐July 1984 as part of the 1984 Marginal Ice Zone Experiment. The entire region was characterized by strong vertical stratification and reduced nutrient concentrations near the surface. Chlorophyllalevels were elevated at the ice edge and decreased both under the ice and away from the ice edge. Chlorophyll concentrations were greatest at the top of the pycnocline and averaged 2.9 μg L−1at 20 m. Primary productivity was also greatest at the ice edge, with daily integrated productivity averaging 426 mg C m−2d−1. Small flagellates numerically dominated the assemblages. Growth rates, when corrected for detrital material, were close to their potential maximum for the temperatures encountered. Large differences between the water temperatures, nitrate concentrations, and chlorophyllalevels during similar periods in 1983 and 1984 were noted. These differences, in addition to the spatial and temporal variations in biological processes induced by mesoscale eddies, suggest that the interannual variability in marginal ice zones may have significant consequences to the region's food web

ISSN:0148-0227    

DOI:10.1029/JC092iC07p06777

年代:1987

数据来源: WILEY

摘要:

The physical properties of sea ice in the Fram Strait region of the Greenland Sea were examined during June and July 1984 in conjunction with the Marginal Ice Zone Experiment field program. Most of the ice sampled within Fram Strait during this period was multiyear. Thicknesses and other properties indicated that none of the multiyear ice was older than 4 to 5 years. Snow cover on the multiyear ice averaged 29 cm, while that on first‐year ice averaged only 8 cm deep. This difference may be related to enhanced sublimation of the snow on the thinner first‐year ice. The salinity profiles of first‐year ice clearly show the effects of ongoing brine drainage in that profiles from cores drilled later in the experiment are substantially less saline than earlier cores. Thin section examinations of crystal structure indicate that about 75% of the ice consisted of congelation ice with typically columnar type crystal structure. The remaining 25% consisted of granular ice with only a few occurrences of snow ice. The granular ice consisted primarily of frazil, found in small amounts at the top of floes but mainly observed in multiyear ridges. The horizontally oriented crystalcaxes showed various degrees of alignment, ranging from no alignment to strong alignments in which the alignment direction changed with depth, implying a change in floe orientation with respect to the ocean current at the ice‐water interface during ice growth. Evidence of crystal retexturing was observed in the upper meter of nearly every multiyear core. This retexturing, consisting of grain boundary smoothing and nearly complete obliteration of the ice platelet‐brine layer substructure, is attributed to summe

ISSN:0148-0227    

DOI:10.1029/JC092iC07p06787

年代:1987

数据来源: WILEY

摘要:

During the summer 1984 Marginal Ice Zone Experiment in the Fram Strait and Greenland Sea (MIZEX '84), passive and active microwave sensors on five aircraft and the Nimbus 7 scanning multichannel microwave radiometer (SMMR) acquired synoptic sequential observations which when combined give a comprehensive sequential description of the mesoscale and large‐scale ice morphology variations during the period June 9 through July 16, 1984. The high‐resolution ice concentration distributions in these images agree well with the low‐resolution SMMR distributions. For diffuse ice edges the 30% SMMR ice concentration isopleth corresponds to the ice edge, while for compact conditions the ice edge falls within the 40 to 50% SMMR isopleths. Throughout the experiment, ice edge meanders and eddies repeatedly formed, moved, and disappeared, but the ice edge remained within a 100‐km‐wide zone. The ice pack behind this alternately diffuse and compact edge underwent rapid and pronounced variations in ice concentration over a 200‐km‐wide zone. The aircraft microwave images show the complex structures and ephemeral nature of the mesoscale sea ice morphology. The difference in oceanographic forcing between the eastern and western sectors of the experiment area generated pronounced ice morphology differences. On the Yermak Plateau, from 3°E to 10°E, the weak ocean circulation allowed the wind to be the dominant force in determining the ice morphology. To the southwest of this region, over the Molloy Deep and the Greenland continental shelf break, from 3°E to 8°W, the ice morphology was dominated by the energetic East Greenland Current with its associated ed

ISSN:0148-0227    

DOI:10.1029/JC092iC07p06805

年代:1987

数据来源: WILEY