Signy Sea Ice Camera
Sea ice plays a major role in generating the cold saline water that occupies the lowest layers of the ocean and intrudes far into the Northern Hemisphere. Ice cover also determines the character of the local ocean circulation and also interacts with weather patterns.
Because many biological systems in the Antarctic involve sea ice, an understanding of long-term changes in ice cover is also important for an understanding of marine living resources. Scientists at the British Antarctic Survey have completed an initial assessment of the data from Signy Island. They have also combined their own records with those from another station in the same island group, which has made similar observations more-or-less continuously between 1903 and 1976. The combined data set provides a unique record of year-to-year variation in ice cover, and is one of very few such detailed series and is unique for the Antarctic.
The project is a continuation of an important environmental data series that has recorded the duration of the sea ice. These measurements have been carried out at Signy Island since the BAS research station was established in 1947, but ended in 1995/96 when the base was transferred to summer-only operations.
The main problem was to decide on the best means of providing an automated substitute for human observation. It was decided to install an automated camera system on the island to record sea ice throughout the Antarctic Winter. This is the most cost-effective means of continuing a series of environmental data that are unique in the region and may prove to be of importance for the entire planet. The camera system needs to function unattended throughout an Antarctic winter. This is approximately six to eight months.
On Signy Island winter temperatures may drop to -35°C therefore a camera system to withstand the rigorous environment of Antarctica was needed.
The original system deployed in 1995 used:-
- A ROBOT-RECORDER 24CE
- A 12V Automatic Aperture Control Unit
- A Schneider Xenar 38 mm F/2.8 lens and gear drive
- A 12v DC Release Solenoid.
- 30m Robot attachable bulk film magazine (capacity to take 800 frames 24 mm X 24 mm at temperatures down to -20 °C).
The film taken by this black and white film camera system proved expensive to develop. An improved colour digital camera system was designed by BAS engineers and installed in 2002.
The power source for the system consists of solar panels, a wind generator and batteries acting as a reservoir. Internal environmental control enables the camera to operate down to –35ºC and to continue operating for a three-month period without solar or wind energy.
Time stamped colour images of 1600x1280 pixels on a 2.24 megapixel camera are taken and compressed to JPEG images for storage onto a low temperature memory card. Current capacities of available memory cards allow two high-resolution images to be taken per day for up to two years. Automatic exposure allows pictures to be taken down to very low light levels.
Annually, the inner camera box is replaced and the older unit is returned to the design engineer for servicing and data retrieval. By reprogramming the look up table on the memory card during servicing, the camera can take pictures at any hour. Photograph quantity and timing is specified for each month of the year. One camera has been sited at Signy base to study sea ice formations and coverage.
The second system has been installed much further south at Mars Oasis to record snow depth.