ICEWATCH-Ice SAR monitoring of the Northern Sea Route

Abstract

The use of Synthetic Aperture Radar (SAR) images from satellites is currently tested in operational sea ice monitoring, and will play a more important role when SAR data become available on a regular basis over all ice-covered areas. SAR images, with a resolution of 100m, can be used to distinguish different ice types and to map leads, polynyas, shear zones, landfast ice, drifting ice and location of the ice edge. The SAR is the only instrument that provides high resolution images of such ice features under different cloud and light conditions. In several demonstration projects the Nansen Centers in Bergen and St. Petersburg have used ERS-1/2 SAR images to monitor sea ice conditions in the Northern Sea Route. The projects have been performed in close cooperation with ice breakers belonging to Murmansk Shipping Company (MSC), one of the most important users of ice information in Russia. From 1995 SAR ice monitoring is established as the first joint project in earth observation between the European Space Agency and the Russian Space Agency. The objective of this project called ICEWATCH is to make SAR data from ERS and ENVISAT available for Russian users of ice data on an operational basis. The Northern Sea Route is the sailing route along the coast north of Russia from the Barents Sea in West to the Bering Strait in east (Figure. 1). The ice conditions restrict sea transportation which requires ice class vessels as well as ice breaker assistance throughout the year. In summer there is traffic in the whole sailing route, whereas in winter it is mainly the western part which is used serving the ports on the Yenisei River. An extensive ice monitoring and forecasting service has been built up in Russia over the last 50 years based on data from satellites, aircraft, vessels, ice stations and coastal stations. Use of spaceborne SAR has not been a part of this service. NERSC first demonsetrated use of ERS-1 SAR data for near real-time ice mapping in the Northern Sea Route in August 1991, only a few weeks after the launch of the ERS-1 satellite. SAR derived sea ice maps were then sent by telefax to the French polar vessel ‘L'Astrolabe” during her voyage through the Northeast Passage from Norway to Japan 1.2 . This demonstration was evaluated as very interesting by the captains and sea ice experts on board the Russian ice breakers which escorted “L'Astrolabe” through the icecovered parts of the route. Since 1993 SAR ice monitoring demonstrations have been carried out on several Russian ice breakers 3,4 . In all these demonstration experiments, a scientist from the Nansen Center in St. Petersburg stayed on board the ice breakers and analyzed the SAR images in cooperation with the captain and ice pilots. In addition to the ice navigation these experiments also had scientific objectives to study sea ice phenomena and their SAR signature along the Northern Sea Route at different times of the year. In January and February 1996, ERS SAR data files were transferred directly to a Russian ice breaker “Vaygach” moving in ice covered areas 5 , by means of Inmarsat connections, a modem and a PC. The time lag from the seatellite overpass to reception of images on board the ice breaker was at a minimum of 5–6 hours, which enabled the captain to select the optimal sailing route (Figure. 2). The expected result of the ICEWATCH project is toi integrate use of satellite ERS SAR data in the Russian Ice Service, and make SAR data readily available for a number of users who need detailed ice information.