Variations of mesoscale and large‐scale sea ice morphology in the 1984 Marginal Ice Zone Experiment as observed by microwave remote sensing

Abstract

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 3øE to 10øE, 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 3øE to 8øW, the ice morphology was dominated by the energetic East Greenland Current with its associated eddies and meanders. aircraft obtained detailed microwave observations of the MIZEX mesoscale areas (,--100 km x 100 km) in which comprehensive dielectric, meteorological, and ocean observations took place [Cavalieri et al., 1986; Shuchman et al., 1987]. The design of the MIZEX mesoscale microwave aircraft programs was based on instrumental and logistical techniques used in earlier MIZ remote sensing studies: the joint U.S./USSR x U.Bering Sea Experiment (BESEX) in winter-spring 1974 [Kondratyev et al., 1975; Gloersen et al., 1982], in the southern Beaufort Sea in winter 1975 [Campbell et al., 1976] and winter-spring 1978 [Campbell et al., 1980], and in the east Greenland Sea during the Norwegian Remote Sensing Experiment (NORSEX) in winter 1979 [NORSEX Group, 1983]. However, the MIZEX '84 remote sensing program differed from these preceding experiments in one fundamental and important aspect: the aircraft and satellite data were used in a near-real time mode to direct investigators in ships and aircraft to rapidly evolving ice-ocean phenomena, especially eddies. The most comprehensive MIZ aircraft program performed to date took place during MIZEX '84 in the Fram Strait-east Greenland Sea area during the period June 9 through July 16, 1984. Five microwave remote sensing aircraft performed sequential mesoscale mapping with a variety of passive and active microwave sensors. The NASA CV-990 ...

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