Preferred Crystal Orientations in the Fast Ice Along the Margins of the Arctic Ocean

Field observations of the growth fabrics of the fast and near-fast ice along the coasts of the Beaufort and Chukchi Seas show that, at depths of more than 60 cm below the upper ice surface, the sea ice crystals show striking alignments within the horizontal plane. At one site this alignment was well...

Full description

Bibliographic Details
Main Authors: Weeks,W F, Gow,A J
Other Authors: COLD REGIONS RESEARCH AND ENGINEERING LAB HANOVER N H
Format: Text
Language:English
Published: 1978
Subjects:
Snow
Ice and Permafrost
Crystallography
*CRYSTALS
*SEA ICE
*ARCTIC OCEAN
POLAR REGIONS
MAGNETIC FIELDS
EXPERIMENTAL DATA
OCEAN CURRENTS
ORIENTATION(DIRECTION)
OCEANOGRAPHIC DATA
FREEZING
COLD WEATHER TESTS
Arctic
Arctic Ocean
Kara Sea
Chukchi
Ice
Ice Sheet
permafrost
Sea ice
Online Access:http://www.dtic.mil/docs/citations/ADA059024
http://oai.dtic.mil/oai/oai?&verb=getRecord&metadataPrefix=html&identifier=ADA059024
Description
Summary:Field observations of the growth fabrics of the fast and near-fast ice along the coasts of the Beaufort and Chukchi Seas show that, at depths of more than 60 cm below the upper ice surface, the sea ice crystals show striking alignments within the horizontal plane. At one site this alignment was well developed at a depth of 15 cm and in all cases the degree of preferred orientation increased with depth, with the strongest orientations occurring at the bottom of the ice sheet. In general the c-axes of the crystals were aligned roughly E-W parallel to the coast. In the vicinity of islands the alignment roughly paralleled the outlines of the islands and in narrow passes between islands the alignment paralleled the channel. Our observations, as well as similar observations made in the Kara Sea by Cherepanov, can be explained if it is assumed that the c-axes of the crystals are aligned parallel to the 'long-term' current direction at the sea ice/sea water interface. The alignments are believed to be the result of geometric selection among the growing crystals, with the most favored orientation being that in which the current flows normal to the (0001) plates of ice that make up the dendritic ice/water interface characteristics of sea ice. It is hypothesized that current flow in this direction reduces the thickness of the solute boundary layer as well as the salinity in the liquid at the interface. This lowered salinity allows crystals in the favored orientation to extend farther into the melt than neighboring crystals with less favored orientations. In addition the current tends to induce a continuous flux of supercooled seawater against the sides of the crystals that extend ahead of the interface.

Similar Items