Snow and ice thickness distributions in the south polar Pacific Ocean

Abstract

Two sets of snow and ice thickness data of antarctic sea ice are presented in this study: drilling profiles on individual sea ice floes and spatially more extensive shipboard observations are investigated in order to reveal spatial and temporal characteristics of sea ice. The data were acquired between 1993 and 1995 in the Ross and the Amundsen/Bellinghausen Seas, two different regions of the south polar Pacific Ocean. Sea ice characteristics as well as their spatial distribution and temporal evolution are derived from the data sets. Strong regional trends are observed in ice thickness distributions of the drilling data. A spatial pattern is detected in the snow and ice thickness data as they were sorted according to distance from the ice edge. Flooding on sea ice floes is a widespread phenomenon in Antarctica and relevant for snow ice growth. Flooding is shown to correlate highly with snow loading, while it was much less distinctly correlated to ridging. Isostatic balance was tested on individual sea ice floes. Deviation from isostatic balance was shown to occur locally but was negligible on averaging scales of a few meters. With the help of ice thickness and roughness criteria an unbiased and reproducible ice classification scheme is developed. A combination of different methods from spectral and spatial statistics was used to describe the surface roughness characteristics of the three ice groups in detail. As a practical outcome from the roughness characteristics, air, water and ice surface drag coefficients were derived. With the goal to enhance sampling efficiency, the methodology of data sampling is investigated and optimized strategies are presented. Finally, a statistical ice thickness model managed to explain regional differences in the shape of the ice thickness distribution and therefore the relative significance of ice growth and development processes for a certain region.