Monitoring Open Water and Sea Ice in the Bering Strait by Radar

Observations made at the Bering Strait show the utility of employing radar systems providing both moving-target-identification (MTI) and short-time-constant video signals for monitoring sea-surface areas containing open water and sea ice. MTI video signals tend to emphasize returns from areas of open water and loose pack ice. Short-time-constant or differentiated video signals tend to emphasize returns from boundaries between water and ice and record echoes from stationary as well as moving targets. Large polynyas (areas of open water) south of projecting points and islands in the Bering Strait area in May are vividly displayed by the combination of MTI and short-time-constant signals. The use of the two types of signals constitutes a simple form of processing in the Doppler frequency domain. The results indicate that the use of MTI systems, or more sophisticated pulse-Doppler systems, could be advantageous for monitoring restricted areas of water in which ice may occur and present a limitation or hazard to navigation by boats and ships.