Melt pond formation and temporal evolution at the drifting station Tara during summer 2007

Abstract

Melt pond coverage of sea ice in the High Arctic was observed for a period of 28 days: from 24 June to 21 July 2007. Pond fractions were computed from digital photographs automatically obtained with a camera and computer unit mounted in the mast of the drifting polar schooner Tara. The area visible in the series of images corresponds to approximately 6400 m2 on the ice. By applying iterative image classification methods, the images were partitioned into melt ponds and other surface types, such as ice or snow. The percentage of melt ponds could be calculated for 22 out of 28 days. Six days were omitted from the analysis because of weather conditions causing poor visibility. Melt pond coverage was seen to rise rapidly shortly after the melt ponds started forming: between 24 and 30 June 2007 the pond fraction increased from 3 to 14%. After the first rapid growth period, the pond fraction increased more gradually, reaching 15% at the end of the data collection period (21 July 2007). Estimated with additional data, the maximum melt pond coverage was reached in mid- August, and totalled 32–42%. Melt onset date and the initial rapid melt pond growth agree well with previous research, but the areal pond coverage appears surprisingly high for the latitude (88°N). Direct comparison with previously observed melt pond coverage is rendered difficult by scarce observations of pond coverage sufficiently high up in the Arctic.