This paper reviews basic synthetic aperture radar (SAR) theory of ocean wave imaging mechanisms, using both known work and recent experimental and theoretical results from the Marine Remote Sensing (MARSEN) Experiment. Several viewpoints that have contributed to the field are drawn together in a general analysis of the backscatter statistics of a moving sea surface. A common focus for different scattering models is provided by the mean image impulse response function, which is shown to be identical to the (spatially varying) frequency variance spectrum of the local complex reflectivity coefficient. From the analysis has emerged a more complete view of the SAR imaging phenomenon than has been previously available. A new, generalized imaging model is proposed.

ERS 1 C band synthetic aperture radar (SAR) data were collected during the Norwegian Continental Shelf Experiment (NORCSEX) both in November 1991 during the ERS 1 commissioning phase and at different seasons in 1992 and 1993. Characteristic SAR image expressions are observed in relation to perturbation of the surface current‐short wave interaction across the Norwegian Coastal Current front for winds less than 10–12 m s−1. In situ measurements document the existence of alternating zones of convergence and divergence coexisting with a strong near‐surface current shear of nearly 4f (where f is the Coriolis parameter) across a distance of a few kilometers. Under calm to moderate winds, i.e., 4–7 m s−1, characteristic expressions of upper ocean circulation features also include the manifestation of eddies through the presence of surface film, which damps the Bragg waves. Comparison of a near‐coincident National Oceanic and Atmospheric Administration advanced very high resolution radiometer image and an ERS 1 SAR image supports the interpretation that surface current fronts are imaged by SAR. In combination with a SAR image simulation model, the relative quantitative importance of shear, convergence, and divergence along the front is examined. Although the model formulation is simple and the absolute magnitude of the perturbations is uncertain, the study shows that the SAR images can sometimes be used to interpret frontal dynamics, including growth and decay of meanders.

Synthetic aperture radar (SAR) images of moving ships often exhibit characteristic patterns associated with various wake phenomena. These features can be classified into three general categories which include (1) surface waves generated by the ship, (2) turbulent or vortex wakes, and (3) internal waves. In this paper an overview of the present status of SAR ship wake imaging is presented.

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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