Improved sea-ice monitoring for the Baltic Sea
Background and objectives
Since many years radar data from satellites are used for mapping of sea ice. Ice coverage and ice concentration are some of the parameters obtained from the imagery. The satellites that are used today only allow acquisition of images at one frequency and with one or two polarisations. With the launch of new satellites it will soon be possible to get fully polarimetric SAR data from three different frequencies. It is anticipated that this will improve the possibilities for accurate characterization of the ice cover. The main objective of this project is to evaluate how multi-polarisation radar data from the Japanese Advanced Land Observing Satellite (ALOS) and the European ENVISAT can improve determination of sea ice concentration, classification of ice types and detection of ice ridges.
Picture: Ice-breaker seen from FLIR-camera during a helicopter fly by.
The project will be focussed on sea ice in the northern part of the Baltic Sea, which is an area with a high level of winter traffic. In order to cover different ice and weather conditions several satellite images will be acquired from both winter and spring. This will give a time series of data that include conditions that currently are considered as difficult. A time series like this will make it possible to test the limits of the developed classification algorithms for the specified data.
To be able to validate the results from the satellite images it is crucial to have good in situ data from the studied sea ice areas. Information about location and structure of the ice edge, new ice, and melt ponds will be collected from helicopter in order to cover a large area. Camera equipment both for the visual and thermal infrared regime will be used. Helicopter observations will be complemented by measurements on the ice.
The results should lead to recommendations on how data from the new radar satellites can be incorporated in the operational services provided SMHI. It is foreseen that this will improve the accuracy of the operational ice charts. More detailed knowledge of the ice conditions would also be useful for data assimilation into the forecast models, eventually producing more accurate ice forecasts which will benefit the icebreaking authorities in the Baltic as well as the large number of merchant vessels transiting the Baltic waters.
Information about changes in ice conditions is highly relevant for climate studies. In order to capture the maximum and minimum ice extent it is important that the time series has a high temporal resolution. SMHI continue to compile these data and the results from this project will hopefully improve the accuracy of future additions to the time series. It is expected that these results will contribute to GMES efforts to detect climate change and monitor its effects.
Leif Eriksson, Chalmers University of Technology, Dept. Radio and Space Science
Karin Borenäs, SMHI, Oceanographic Research and Development
4 juli 2011