Sidescan sonar imagery of the winter marginal ice zone obtained from an AUV

The first Arctic under-ice sidescan sonar imagery from an autonomous underwater vehicle (AUV) has been obtained in the winter marginal ice zone of the East Greenland Current at 73degrees00'N, 11degrees47'W, using a Maridan Martin 150 vehicle operated from R/V Lance. First-year, multiyear, brash, and frazil ice can be discriminated, with the underside of multiyear ice appearing smooth as compared to the rough underside detected by submarine-borne sidescan in the Arctic Basin, implying downstream bottom melt. The ice draft profile was obtained from the vertical part of the sidescan beam, and the probability density function of ice thickness was derived and found to agree well with upward sonar results from this region obtained in 1987 from a British submarine.