Airborne Remote Sensing
Multispectral airborne remote sensing – supplemented by observations from trained observers – remains the most effective method for identifying and mapping the presence of oil on water. Modern pollution surveillance aircraft operated by nations such as Canada and Sweden employ a mix of sensors such as side-looking airborne radar and forward- looking infrared radar, together with conventional digital cameras. Visible sensors are constrained by darkness, fog and cloud cover.
The advent of synthetic aperture radar (SAR) satellites in the 1990s represented a quantum leap in the ability to monitor Arctic sea ice under all weather conditions and through periods of winter darkness. SAR has proven effective in mapping large oil slicks on the open ocean and could be effective in ice-infested waters.
Combination Airborne and Surface Systems
Ground penetrating radar (GPR). A series of tank tests and field experiments demonstrated that surface-based GPR can clearly detect and map the presence of oil films as thin as 1 to 3 cm – both underneath ice and trapped as layers within ice. Numerical modelling has indicated that the same system operating at a low altitude from a helicopter should also be able to detect thin oil layers under cold ice in midwinter, as well as oil on ice that is buried under snow.
Handheld IR. Low-cost, handheld IR systems can detect oil under certain conditions. In daylight, IR sensors can distinguish between oil, ice-free water and snow, and clean ice floes. Performance is less reliable at night and in fog. All results will be summarised and aggregated.
Depending on the ice conditions (floe-size, thickness, stability), it may be possible to deploy a variety of remote-sensing systems to work directly from the ice surface or from the deck or bridge of a nearby vessel. Surface-based sensors may include handheld IR, dogs, X-band marine radar, and integrated systems combining IR and low-light-level camera technologies such as the Aptomar SECuras system.
Dogs. The training and field assessment of dogs for detecting oil in snow and on ice was a highly successful part of a previous JIP remote sensing programme. Tests conducted in April 2008 at SINTEF’s research station near Svea on Svalbard followed positive early trials in Trondheim, Norway, in 2007 and confirmed that dogs can be used to detect oil spills covered with snow and/or ice in harsh Arctic winter environments. The dogs maintained their full concentration and operative sensitivity for several days even after being transported in cages, strapped on scooter sledges, and exposed to bumpy rides and fumes.
X-band marine radar (short and medium pulse). These radar systems have proven their ability to detect slicks at sea during tests sponsored by the Norwegian Clean Seas Associating Operating Company (NOFO); there is no technical reason why similar results would not be possible, at least in very open drift ice (10-30 percent ice coverage) where water predominates. The upper limit of ice concentrations where marine radar would cease to be effective is not yet known.
Upward Looking Sonar: Upward-looking sonar (ULS) has been and continues to be the primary source of data for monitoring ice thickness. These instruments operate autonomously during one year or longer deployments, returning data on time and spatial scales which are essential to the understanding of mechanical and thermodynamic aspects of sea ice processes.