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ICE COVER PREVENTION BY MEANS OF AIR BUBBLES, NARSARSSUAK, GREENLAND

The climate in the coastal regions of southwestern Greenland is such that ice covers are not formed locally in the sea or in the outer parts of the deep fiords. Only in the inner parts of the narrow fiords and in highly sheltered coves in the fiords does a continuous ice cover form during the winter. This fact has often in general terms been attributed to the effect of the sheltering from wave action, the idea being that the presence of waves would tend to prevent the formation of ice sheets. However, there is a possibility that the tendency for formation of ice covers may be governed partly or primarily by other factors than the degree of sheltering from wave action. The upper ends of the fiords are always the site of the mouth of a river, and the same applies to many of the small bays that are attractive from the point of view of wave protection. It was found that the salinity generally increased with the depth below the surface as well as with the distance from the inner end of the bay, the range of variations being normally from 29 to 33 parts per thousand. The vertical salinity variation was normally sufficient to prevent vertical exchange of water due to the cooling off of the surface layer. The climate conditions were not very far from normal, but the ice cover was broken up about 6 times in northeasterly gales, and the maximum thickness of the ice was rather low, about 15 cm. The results of the field observations relating to ice formation in the bay did suggest that some reduction in ice formation could be obtained by creating a vertical mixing of the water in the bay. Therefore in the winter of 1966/67 a pilot experiment of this kind was performed. Two 1" plastic tubes with 0.6 mm holes spaced 2 metres apart were placed on the bottom at the inner end of the bay, and air was supplied to the tubes from a standard compressor with a capacity of 4.5 cu. m. per minute. During periods with comparatively light general ice cover holes in the cover with a diameter of 1-1.5m were formed over each hole in the tubes. When the temperature dropped to about minus 10 degrees C the open holes were reduced to about 0.5 m diameter or were in some cases completely closed. However, it was always clear that the ice was significantly thinner above the tubes than elsewhere. It is considered that the experiment, which was designed to keep the bay open but only to investigate the possibilities of the air bubble method, did suggest that a very significant improvement in ice conditions under circumstances such as those obtaining at Narsarssuak may be achieved by means of a properly designed air bubble arrangement. When combined with frequent traffic of vessels in the harbour it appears very probable that an air bubble arrangement could provide entirely acceptable navigation conditions throughout the winter period.

  • Supplemental Notes:
    • Abstract of paper delivered at the First International Conference on "Port and Ocean Engineering under Arctic Conditions" held at Trondheim, Norway, August 23-30, 1971
  • Corporate Authors:

    POAC Conference

    ,    
  • Authors:
    • Hulgaard, E
    • Sorensen, T
  • Publication Date: 1971-8-23

Subject/Index Terms

Filing Info

  • Accession Number: 00025672
  • Record Type: Publication
  • Source Agency: Arctic Institute of North America
  • Files: TRIS
  • Created Date: Mar 28 1972 12:00AM