ABSTRACT

During the summer of 2009, ice observations were made using Electromagnetic, Video and Laser sensors mounted on an helicopter that was stationed on the CCGS Amundsen while she traversed the Canadian Beaufort Sea pack ice from August 28 to September 12. The Arctic pack ice encountered was made up of thin "rotten" first year ice, 50–75cm thick and thicker second year ice 2–3m thick containing melt ponds. The pack ice did not represent an obstacle to the icebreaker which moved at full speed to well above 75oN latitude (Fig. 1). Upon arriving on September 6 at the "Multi-Year Ice" station within the thicker, consolidated pack ice, long period swells with a period of 13.5sec at the start and reducing in time appeared coming from the NW. They were present for 2 days and broke up the large 2–3km ice floes into smaller floes of less than 100m. The video camera and laser mounted on the helicopter documented the break-up of the floes. Data collected along long West-East flight paths showed that the long period swells, generated by a distant storm, penetrated 350km into the pack ice, breaking up and diverging the pack ice without any ridging. This process will enhance the thermodynamic and dynamic processes of pack ice decay (Toyota et al., 2006 and Squire et al., 2009) that should be included in ice-ocean climate models.

INTRODUCTION

In the Canadian Beaufort Sea, sea ice is present for most of the year and represents a hazard to navigation and offshore oil&gas development. It is now generally accepted that due to climate change, the Arctic polar ice cap is melting (ACIA, 2005 and IPCC, 2007). The Arctic ice extent is decreasing (Serreze et al., 2007) and the remaining ice is thinning (Kwok and Rothrock, 2009).

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