Growth and motion at the Weddell Sea ice edge

• Main Author: Doble, Martin Jonathan
• Format: Thesis
• Language: English
• Published: 2007
• Subjects: Weddell Sea; Greenland; Weddell; Pancake; Greenland Sea; Sea ice
• Online Access: https://eprints.soton.ac.uk/63134/; https://eprints.soton.ac.uk/63134/1/Doble_2007_PhD.pdf

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