The Seasonal Cycle of Sea Ice Thickness on the North East Greenland Shelf

Abstract

Abstract The seasonal cycle of sea ice thickness on the North East Greenland shelf as derived from 22 years of direct observations with upward looking sonars is quantified. The seasonal cycle of the mean and modal thickness is presented, both as absolute numbers and as anomalies from the annual mean. The average seasonal amplitude for the whole observational period (19902011) is 0.5 m for the modal thickness, and 1.12 m for the mean ice thickness. The mean cycle was also calculated for two distinct periods with respect to the age and thickness of the ice in the region; 1990-2000 and 2001-2011. Between these two periods, the average seasonal amplitude in modal thickness was reduced by 0.2 m. For the mean ice thickness, the corresponding reduction was 0.3 m. In addition the seasonal cycles were shifted down. The results presented here are directly applicable for industry planning activities on the North East Greenland shelf, and are particularly useful for oil companies holding licenses in the Kanumas area. The seasonal and interannual variability of sea ice thickness is large in this region. Any plan for field development or operations in the region must take this variability into account. This includes ice thickness observation campaigns (e.g. by airborne electromagnetic devices) set up to provide details about the design basis prior to field development, where it is imperative that the observations are interpreted on a background of variability. Along with previously published results on long term variability, the present results on the seasonal cycle provide such a background.