Trends in the draft and extent of seasonal pack ice, Canadian Beaufort Sea

Continuous observations by sub-sea sonar form a 12-year draft record for seasonal pack ice in the Beaufort Sea. There has been a small trend (0.07 m/decade) to thinner ice, but this has low statistical significance; net change is comparable to the uncertainty of measurement. Although ice concentration at the monitoring site has increased by 0.14 since 1991, there is little evidence for trend in ice-covered area over the continental shelf in the longer (36-year) ice-chart record. However, local air temperature has increased by 1.6 +/- 0.6 degrees C during the last three decades. Clearly longer time series are needed to detect and understand change. Changing snow cover, ice circulation and ice deformation may obscure the direct effects of warming climate on seasonal pack ice.