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|Title:||Physical properties of summer sea ice in the Fram Strait, June-July, 1984|
|Authors:||United States. Office of Naval Research.|
Gow, Anthony Jack.
Tucker, W. B.
Weeks, W. F.
|Publisher:||Cold Regions Research and Engineering Laboratory (U.S.)|
Engineer Research and Development Center (U.S.)
|Series/Report no.:||CRREL report ; 87-16.|
Abstract: The physical properties of sea ice in the Fram Strait region of the Greenland Sea were examined during June and July 1984 in conjunction with the MIZEX field program. Most of the ice sampled within Fram Strait during this period was multi-year; it is estimated to represent at least 84% by volume of the total ice discharged from Fram Strait during June and July. Thicknesses and other properties indicated that none of the multi-year ice was older than 4 to 5 years. Snow coves on the multi-year ice averaged 29 cm deep while that on first-year averaged only 8 cm. Much of this difference appears to be the result of enhanced sublimation of the snow on the thinner first-year ice. The salinity profiles of first-year ice clearly show the effects of ongoing brine drainage in that profiles from cores drilled later in the experiment were substantially less saline than earlier cores. Bulk salinities of multi-year ice are generally much lower than those of first-year ice. This difference furnished a very reliable means of distinguishing between the two ice types. Thin section examinations of crystal structure indicate that about 75% of the ice consisted of congelation ice with typically columnar type crystal structure. The remaining 25% consisted of granular ice with only a few occurrences of snow ice. The granular ice consisted primarily of frazil, found in small amounts at the top of floes, but mainly observed in multi-year ridges where it occurred as the major component of ice in interblock voids. The horizontally oriented crystal c-axes showed varying degrees of alignment, ranging from negligible to strong, in which the alignment direction changed with depth, implying a change in floe orientation with respect to the ocean current at the ice/water interface during ice growth. Evidence of crystal retexturing was observed in the upper meter of nearly every multi-year core. This retexturing, involving grain boundary smoothing and nearly complete obliteration of the original ice platelet/brine layer substructure, is attributed to summer warming; ice exhibiting such substructure can immediately be identified as multi-year ice.
|Appears in Collections:||CRREL Report|