Growth and motion at the Weddell Sea ice edge

The formation of sea ice in the presence of turbulence was studied using data from drifting buoy<br/>deployments and ice sampling in the Weddell Sea during April 2000. The study sought to<br/>improve understanding of pancake ice in terms of dynamics, heat fluxes, ice growth rates and<br/>mechanisms.<br/>Ice motion at high frequencies was examined using GPS buoy positions at a 20-minute<br/>sampling interval. Relative motions of the buoy array were characterised by a marked<br/>oscillation at the highest frequencies, with an RMS value two orders of magnitude higher than<br/>previously seen in the Weddell Sea. This motion ceased overnight as the pancakes consolidated.<br/>Wave forcing, either surface gravity or internal, was postulated as the cause. The oscillation was<br/>found to significantly influence the proportions of pancake and frazil ice, though the nature of<br/>the ice cover meant that ice production rates were unaffected, in contrast to the enhanced growth<br/>this would imply for congelation ice. Momentum transfer parameters were found to be similar<br/>to those found for the Greenland Sea Odden ice tongue.<br/>Pancakes were found to be dominantly thickened by over-topping of the surrounding<br/>frazil ice crystals, termed ‘scavenging’, and gave rise to distinct morphologies, which were<br/>classified. A physical model was developed to describe the evolution of the pancake ice cover to<br/>consolidation. Ice production in the pancake/frazil process was found to proceed at<br/>approximately double the rate of the equivalent congelation ice cover, or 0.58 times the limiting<br/>free-surface frazil production. It was suggested that the discrepancy will seriously impact largescale<br/>modelling attempts to simulate heat and momentum fluxes between the ocean and<br/>atmosphere, as well as salt rejection and subsequent water mass modification, though it is<br/>acknowledged that further field measurements are required to place some currently empirical<br/>parameters into a physical context.

Name dc:type.qualificationname

Ph.D.

Level dc:type.qualificationlevel

doctoral

Grantor dc:publisher.institution

University of Southampton

Year dc:date.issued

2007

Author dc:creator

• Doble, Martin Jonathan