Remotely sensed imagery is the acquisition of images by satellite and is interpreted through the application of algorithms. These mathematical equations are used to convert light measurements observed by satellites to other types of parameters, such as chlorophyll concentration.
This is where the field of ocean optics comes in: in interacting with water, light undergoes absorption, scattering or transmission. In absorption, certain wavelengths of light are absorbed by particles; in scattering, a certain amount of light is reflected by the particles. The sum of the two equals the light transmitted toward the sea floor. Ocean optics involves the study of these properties of water.
Pierre Larouche and his team are using ocean optics and satellite imagery to convert physical data—absorption and scattering of light—to biological data—chlorophyll concentration. Chlorophyll concentration is the focus because it provides information on phytoplankton. By studying chlorophyll concentration, researchers can determine quantities of and changes in phytoplankton in the Arctic Ocean.
A phytoplankton bloom in the Barents Sea. Photo Credit: Jeff Schmaltz
Research undertaken by Pierre Larouche and his colleagues has led to the definition of new algorithms, specifically developed for interpreting satellite images of the Arctic. These adapted algorithms can therefore be used to re-examine all the imagery archived since 1997. In this way, scientists will obtain reliable and representative historical data covering more than ten years. They will then be able to reassess the forecast models developed using the old algorithms and modify the results accordingly.
Climate change and the melting ice pack are opening a new ocean for phytoplankton. The effects of these changes on the upper links of the food chain are still unknown because the feeding habits of species that consume phytoplankton are not fully documented. However, it is known that any change in quantity, type, or location of phytoplankton will necessarily affect the behaviour and survival of other animals, right up to large marine mammals and polar bears.
source: Canadian Department of Fisheries and Oceans