Sea ice drift analysis in the Barents Seas

The objective of this study was to observe sea ice drift in the Barents Sea from satellite data and in situ data from drifting ice buoys, and furthermore to use these data to validate ice drift estimates from model simulations. The background for this is the need to obtain better data on sea ice drift and iceberg drift, as well as to validate an iceberg drift model under development at NERSC. The Barents Sea had a record minimum ice extent in the spring of 2006, allowing us to study ice drift only in the northeastern part, between Novaya Zemlya, Franz Josef Land and Svalbard. Also the air temperature in this period was record high, with anomalies of 4 – 6 degrees above average. Wideswath SAR images from ENVISAT were collected from early March to late April, covering the sea ice areas roughly every three days with some interruptions. Also ASAR Global Mode data with 1 km resolution were used to estimate ice drift. The SAR ice drift vectors were compared with large scale ice drift provided by Ifremer, based on scatterometer and passive microwave data for 17 time intervals, each of three day duration. The Ifremer ice drift products are uniformly distributed in time and space, while the SAR data provides more scattered distribution of the vectors. This is due to fact that the SAR wideswath data did not cover the whole study area regularly every three days. The SAR ice drift and Ifremer ice drift showed very good agreement, and the SAR data with higher resolution could therefore be used to validate the Ifremer products. Three drifting ice buoys from CMR were deployed on ice floes and produced in situ ice drift continuously until the buoys drifted into open water southeast of Svalbard. During a three day period from 15 to 18 March, simultaneous ice drift data were obtained from both SAR and the drifting buoys. The two ice drift data sets were consistent, showing that the SAR retrieval was very close to the buoy data for the three mean drift: the displacement from SAR was 63.0 km and from the buoys 64.4 km. The direction of the drift was 190° from SAR and 196° from the buoys. The TOPAZ model simulations of ice drift were compared with the observed ice drift from SAR and Ifremer for the 17 time intervals. There was generally good agreement between the observed and modeled ice drift. The present study has used a three day interval for the ice drift, but it is necessary to compare ice daily averaged ice drift, because we know that ice drift can change rapidly in this region due to changing wind forcing. It is important to assess how well satellite data can be used for monitoring daily ice drift. Data on sea ice drift will be an important component of the validation of the Barents Sea model that includes an iceberg drift model. It is recommended to continue observation of sea ice properties as part of the iceberg modelling work in the Barents Sea. The goal for this work is to come up with a monitoring and forecasting system for sea ice and icebergs, using numerical models in combination with satellite data and drifting ice buoys.NERSC Technical Report no. 27