INTRODUCTION 
The North Water is a recurring polynya in the nogthern Baffin Bay, 
with an approximately equal area to Switzerland (40,000 km ). In 1972, an inter- 
national team of scientists under the leadership of the late Fritz Müller star- 
ted the North Water Project aimed at an investigation of climatological and 
glaciological influences of the North Water on it's surroundings. During the in- 
tensive phase of the project (1972-74), three stations -Coburg Island at the 
entrance of Jones Sound to the Baffin Bay, Carey Islands in the northern Baffin 
Bay and Cape Herschel on Ellesmere Island in the northern Smith Sound- were man- 
ned for glaciological, climatological and atmospheric measurements (Müller et al, 
1973). 
The sea ice distribution and movement were monitored for the years 
1972 to 1981 (excluding 1977 to 1979 ) during daylight hours with the aid of 
Landsat II and III satellite images (Ito,1982,in press). Since 1974, low-level 
remote sensing flights were included within the field activities of the project 
(Miller et a1,1975). Their task was to establish the amount, spatial distribu- 
tion and temporal variation of open water, melting and refreezing zones, of frac- 
tures and of different sea ice types as a contribution to our knowledge of the 
origin and of the existing mechanisms of such polynyas. 
This work did not include measurements of the ice distribution in the 
dark season.Until now, no high resolution satellite images are available for that 
time period. Therefore, for the Winters 1978/79 and 1980/81 low-level remote 
sensing flights were carried out in order to describe the ice conditions with 
the aid of infrared thermometry. 
In this paper the corrections for brightness temperature readings of 
snow, water and ice surfaces, the identification of sea ice types based on sur- 
face temperatures and the ice distribution in the North Water for the Winter 
1980/81 will be presented. 
INSTRUMENTATION AND MEASUREMENTS 
The thermal radiation emitted by the sea surface was measured with a 
Precision Radiation Thermometer (PRT-5) in the spectral wavelength band of 9.5 
to 11.5um from a flight altitude of 300 m. The field-of-view of the instrument 
beeing 20 deg. surface radiation was received from circular areas 100 m in dia- 
meter. The measurements were recorded on a ROAR-80 data logger. At the same 
time the ground along the flight path was filmed on Ektachrome Videonews High 
Speed Tungsten 7250 film with a speed setting of 1600 ASA (nominal speed:400ASA) 
to obtain pictorial information for locational referencing and visual evaluation. 
A Spectrolamp SX-16 searchlight with an average beam power of 25,000 lumen serv- 
ed as a source of illumination. In addition,a Hasselblad 500 EL camera was used 
occasionally to take high resolution sea ice pictures. The instruments were oper- 
ated vertically through a hatch in the bottom of a Twin Otter aircraft, which 
was flown at an average airspeed of 220 km/h. For later atmospheric correction 
of the thermal measurements, the air temperature was measured with a PT-100 
resistance thermometer. The flight path (Fig.l) had a total length of 2300 km 
of which 2000 km were over the North Water. From December 1980 until March 1981, 
six low-level remote sensing flights were carried out. The flight dates (Tab.2) 
were chosen such that different meteorological circulation patterns over the 
North Water and it's surroundings were represented. 
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