The study of Weddell Sea ice using passive microwave and buoy data

The growth of the Weddell Sea ice cover in 1980 is examined, using Nimbus-7 satellite Scanning Multi-channel Microwave Radiometer (SMMR) data in combination with data (positional, air temperature and atmospheric pressure) from 4 Nimbus-tracked drifting buoys. Ice concentrations are retrieved from the SMMR data by applying a cluster analysis algorithm developed by J. Comiso of NASA. Analyses of computed differential kinematic parameters (DKP)s of the buoy array offer insight into the complex mesoscale behaviour of the underlying Weddell Gyre. High frequency divergence, convergence and deformation events isolated in the DKP results, and driven largely by the regular passage of cyclones, are related to changes in ice concentration observed in the SMMR data. The profound role of the Antarctic Peninsula in influencing both atmospheric and oceanic circulation (and thus ice formation, drift and eventual decay) in the region is evaluated. Possible relationships between buoy drift in the inner pack and ice edge advance are examined, yielding information on the relative importance of ice growth in open water within the pack and that at the ice edge. After an introductory chapter, Chapter 2 describes the physical setting of the Weddell Sea. Comparisons are drawn both with other sectors of the Southern Ocean and the Arctic, emphasizing the uniqueness of the region not only in terms of its climate and oceanography but also its sea ice cover. Chapter 3 traces the evolution of passive microwave remote sensing from space as a tool for monitoring Antarctic sea ice extent and concentration; the relative merits and disadvantages of these techniques are evaluated. Chapter 4 concentrates on the use of SMMR data. Detailed comparisons are made of algorithms available for the extraction of ice concentrations from the raw brightness temperature data. The choice of algorithm used is justified. Chapter 5 is largely concerned with the analysis of the buoy data, and the kinematic behaviour of the array as a unit. These results are combined with the SMMR data in Chapter 6 to identify distinct dynamic zones and meridional advective sectors, and to compare the behaviour of the inner pack with that of the unconstrained ice edge. The evolution of a high concentration core within the unique perennial sea ice zone hugging the east coast of the Peninsula, which persists throughout the period of study is unusual enough to merit a separate sub-section. Conclusions are drawn in chapter 7.