Seventeen dipole eddies, including five large, well-formed ones, three second-generation eddies, and two double eddies, were observed in the Alaska Coastal Current near Kayak Island in one single scene of the Landsat thematic mapper (TM) on April 22, 1985. The digital Landsat TM satellite data were computer analyzed to extract details in the near coastal circulation in the northern Gulf of Alaska. Enhancement techniques were applied to the visible and thermal IR bands. The features are evident only in the visible bands because of the ability of these bands to detect the distribution of sediments in the near surface. These eddies did not have a significant thermal signature. The sources of these sediments are the glacial streams found throughout the Gulf of Alaska coast. Eddies of this configuration and frequency have never been observed here previously. However, the oceanographic and meteorological conditions are typical for this time of year. These eddies should be important to the cross-shelf mixing processes in the Alaska Coastal Current and are an indicator that the flow here can be unstable at certain times of the year. 13,041 13,042 AHLN•S ET AL.' MULTIPLE DIPOLE EDDIES IN ALASKA COASTAL CURRENT

Multi‐temporal satellite images, field observations and field measurements were used to investigate the mechanisms by which sea ice melts offshore from the Mackenzie River Delta. Satellite data recorded between April and August 1986 were corrected to a map projection and calibrated such that albedo and temperature values could be compared. Three stages in the melting of sea ice were identified: flooding (overflows), insolation and melting by warm river water. The albedo values of overflows were as much as 1/7 that of ice values while the albedo of ice decreased by 1/3 over the summer. Approximately two weeks after the overflows develop, sea surface temperatures rise as the river‐discharge peaks and becomes the dominant source of energy. By this process, ice removal in the delta regime is initiated two months earlier than adjacent coasts with minimal runoff. However, the net result is only a two‐week acceleration of ice removal in the delta region.

Ice distribution and motion in the Bering Sea from March to June 1974 were observed by imagery from the NOAA 2 and 3 VHRR (very high resolution radiometer) satellites. The southerly ice edge was nearly constant in position from March to mid‐May, when ice disintegration had progressed to a point where the edge was undefined. Ice movement was southerly in response to northerly winds until late April, after which variable ice motion reflected variable winds. The southerly motion created regions of ice divergence south of islands and along east‐west trending southern coasts. In some areas such as the Bering Strait, water motion exerted sufficient stress on the ice to balance the wind.stress, resulting in stationary ice or northerly ice motion. The Bering Sea ice cover is conceptualized as northern source and southern sink regions connected by an intermediate zone of southerly ice motion. A mean observed southerly ice motion of 18 cm s−1 requires heat losses for ice formation of the order of 10 g‐cal m−2 s−1 or an order of magnitude greater if most ice is assumed to form in divergent areas covered by thin ice or that have open water. These values are in agreement with previous estimates of sea‐air heat flux in the Arctic.

Selected infrared images obtained by the NOAA satellites have increased our understanding of the formation and extent of the Alaskan Coastal Current, a movement of relatively warm water from the vicinity of Bering Strait northward along the Alaskan coast past Point Barrow and eventually into the Arctic Ocean where it disperses. Oceanographic measurements made from an icebreaker during the same period give spot checks on the depth of the warm layer, as well as the outline of a downward trend of the current when it is blocked by the ice. A study of satellite and oceanographic observations over a seven-year period, 1974-1980, reveals many interesting features of the flow and shows the annual variability. The northward flow and the shape of the ice edge are interrelated in that the flow is partially blocked by the ice and the ice is melted by the oncoming warm water. The solar-heated waters in Kotzebue Sound, Norton Sound, and along the coast to the south are seen as a major source of the heat in the coastal current.

ABSTRACT. Two la rge glacier tongues, which exte nd substa ntiall y across th e coas tline of King G eo rge V La nd in Eas t Antarctica, ha\'e been studi ed by remote sensing (synth etic aperture radar, JERS-I ). Th e to ngu e of Mertz G lacier is in a state of a d va nce, wh ile th e Ninn is Glacier tongue is retrea ting. Some m o re speci fi c points are:Th e distin ctive surface stru ct ure a nd th e form of the glacier tongues indi ca tes th a t they are Ooa ting.Whil e th e tongue o f Ninn is G lacier has lost a bo u t two-thi rds of its a rea since 191 3, the M ertz G lacie r tongue has a d va nced subs ta n t ia ll y and has a bo u t doubl ed its areal ex tent ove r the sa me time p eriod.Th e an nu a l move m ent of th e tong ue of ~Vl e rl Z G lacier was d ete rmin ed as a bo ut 1.2 km. This is close to th e valu e of th e advance o f th e tip of th e to ng ue since 1963 , which was d e termined as 0.9 km year-I.