Abstract
AbstractDuring the LeadEx main field experiment, held in April 1992 in the Alaskan Beaufort Sea, a number of large ice stalactites were observed growing under young lead ice. Formation of the stalactites was associated with rafting of the thin, highly saline ice. The rafting caused the brine to drain rapidly from the ice at a temperature well below the freezing point of the surrounding water, which in turn caused ice to form in a hollow cylinder around the brine plume. Within a 15 h period after the rafting event, the stalactites, which were located approximately 10 m apart in a line along the upwind edge of a 150 m wide lead, had grown to a length of 2 m. A detailed structural analysis of the upper part of one of these stalactites revealed that the interior channel, down which the brine flowed, was bounded by a zone of frazil ice that developed into a shell of columnar ice. The growth of the columnar ice was directed radially outward and the c axes of these crystals were oriented perpendicular to their growth direction. Development of the stalactites illustrates the impact ice deformation can have on the process of brine rejection in freezing leads and potentially on the thermohaline structure of the upper ocean in the immediate vicinity of the lead.
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