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Supporting transport routing  Navigation through sea ice
Ice watchers Many countries that are reliant on shipping through ice-affected areas operate national ice monitoring and icebreaker services, including Russia, China and the nations of Scandinavia. The International Ice Patrol run by the International Maritime Organisation monitors icebergs affecting busy North Atlantic sea-lanes.
The take-up of such services is increasing. Fishing fleets, oil and gas companies and mineral prospectors are increasingly active around Arctic regions, their moves north driven by dwindling returns from traditionally exploited zones and made feasible by technological advances.
Ships' information requirements Ship operators require precise up-to-date information on the location of ice edges and open water and the ice type and concentration along their vessel's route. In the case of oil shipments, tanker insurance is only valid for particular sets of ice conditions and operators need to ensure their classification ranking is consistent with the conditions they face.
Traditionally, ice-monitoring services are based on data from aircraft, ships and land stations, providing standardised information products used by ship operators to modify routes and choose the optimal routes for icebreakers clearing a way to port. But the area coverage available from such sources is always limited, and often impeded further by bad weather.
Earth Observation has begun to fill this performance gap, enabling continuous wide-area ice surveillance. While clouds and winter darkness obscure optical images in the regions of interest, radar instruments of the type flown on ERS and Envisat go on acquiring data regardless of light levels or weather. Because they measure surface roughness rather than reflected light radar images can differentiate ice floes and ice bergs against open water, and even detect different ice types – such as the hazardous multi-year ice that even icebreakers try to avoid. Daily updates
Ice-monitoring bodies such as the Canadian Ice Service and International Ice Patrol are using Envisat Advanced Synthetic Aperture Radar (ASAR) imagery in conjunction with a radar instrument on the Canadian Space Agency's Radarsat for systematic coverage of their regions of responsibility, making updates possible every 12 to 24 hours.
The Finnish Ice Service has employed space-derived radar data for more than a decade – obtained first from ERS, then Envisat and Radarsat – and it has become sufficiently important that it has almost completely supplanted reconnaissance flights. Ice classification maps generated from radar imagery are now being supplied to users at sea. Last update: 12 July 2004
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