An algorithm has been developed for estimating total and multiyear sea ice concentration from passive microwave and surface air temperature measurements. The algorithm was made for use with Nimbus 7 scanning multichannel microwave radiometer (SMMR) data. It is based on radiation physics and may thus easily be modified to suit other passive microwave instruments. A comparison between Nimbus 7 SMMR and aircraft microwave measurements indicates that estimates of total ice concentration are accurate to ±3% and those of multiyear ice concentration to ±10%. These accuracies are not valid during the melt season when the snow on the ice is wet. For the first time such a comparison of independent estimates has been performed to validate the capability of measuring sea ice coverage from space. The ability of the SMMR to follow moving patches of multiyear ice and of rain/wet snow areas has been demonstrated. From the concentration estimates the sharpness of the ice edge can be estimated. The need for accurate concentration estimates for reliable heat budget estimates in the Arctic is also discussed.

During September–October 1979 the Norwegian Remote Sensing Experiment was carried out in the marginal ice zone north of Svalbard. Convergence of the ice cover is correlated with along‐ice edge winds with the ice to the right, while divergence occurs during office winds or calm conditions. A wind‐driven ice edge jet is observed. Wind‐driven upwelling of the pycnocline of up to 7 m was present along the ice edge during a 10‐ to 15‐m/s easterly wind event. The upwelling is due to Ekman divergence at the ice edge, caused by higher wind stress over ice than over open water. The ice edge meanders with a scale of 20–40 km and sheds eddies with a scale of 5 to 15 km into the open water. This scale is of the same order as the Rossby radius of deformation. Eddies with the same scale are also seen in the conductivity, temperature, and depth observations. Conditions during the experiment were such that barotropic instabilities could have generated these eddies.

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Hydrographic (CTD) observations obtained with R/V‘Lance’in July‐August 1982 across the Fram Strait are presented. The extent and the presence of traditional water masses such as Atlantic Water, Polar Water and Greenland Sea Deep Water are discussed. The complicated hydrographical structure in the upper water masses due to eddies and fronts near the ice edge is noted. An intermediate water mass characterized by a salinity minimum is found all across the Strait, and is suggested to originate in the Greenland Sea. The deep water in the south‐west part of the Strait shows strong horizontal salinity and temperature gradients, and the structure of the corresponding station profiles indicates large hydrographical activity. This is in contrast to the east‐north‐east part, where the horizontal gradients are much weaker and the profiles much smoother. Thus most of the deep‐and bottom‐water communication between the Greenland/ Norwegian Seas and the Arctic Ocean seems to take place west of the 0° meridian.

Hydrographic (CTD) observations obtained with R/V 'Lance' in July-August 1982 across the Fram Strait are presented. The extent and the presence of traditional water masses such as Atlantic Water, Polar Water and Greenland Sea Deep Water are discussed. The complicated hydrographical structure in the upper water masses due to eddies and fronts near the ice edge is noted. An intermediate water mass characterized by a salinity minimum is found aU across the Strait, and is suggested to originate in the Greenland Sea. The deep water in the south-west part of the Strait shows strong horizontal salinity and temperature gradients, and the structure of the corresponding station profiles indicates large hydrographical activity. This is in contrast to the east-north-east part, where the horizontal gradients are much weaker and the profiles much smoother. Thus most of the deep-and bottom-water communication between the Greenland/ Norwegian Seas and the Arctic Ocean seems to take place west of the 0" meridian.