Investigating two averaging methods for sea ice thickness and volume in the Southern Ocean from 1995-1998

Measurements of sea ice thickness are necessary to understand complex polar climate systems. However, the records of sea ice thickness in the Southern Ocean have insufficient spatial coverage and irregular time intervals. One way to address the lack of data is to use operational ice charts which are based on multiple remotely sensed data sources. We use ice type as a proxy for sea ice thickness from ice charts to calculate the thickness distribution in the Southern Ocean on a regional scale. We explore how averaging a sea ice thickness distribution at different model grid scales impacts the end results of the sea ice thickness seasonal cycles. This paper reports the results of two calculations of sea ice thickness and volume based on measures of central tendency for the thickness distribution. The area-weighted average thickness is calculated from the ice type at the ice chart polygon scale, and the integrated thickness is calculated from the thickness distribution of an entire region. For regions in the Southern Ocean, integrated thickness from ice chart stage of development was always greater than average weighted thickness. At the Southern Ocean basin scale, the volume calculated with integrated thickness is up to 60% larger than volume calculated from average thickness at the ice chart polygon scale. This paper makes recommendations for calculating the thickness distribution and volume of sea ice over large scale regions.