On August 1, 2013, the Moderate Resolution Imaging Spectroradiometer (MODIS) flying aboard NASA’s Terra satellite captured a brilliant true-color image of a seasonal phenomenon – a summer phytoplankton bloom in the Barents Sea. The brilliant colors are caused by the reflection of light from different species of phytoplankton – microscopic plant-like organisms that contain chlorophyll and other pigments, and which form the basis of the marine food chain.
Each spring lengthening sunlight and warming temperatures causes the sea ice covering the Barents Sea to slowly retreat. The mixing of icy cold melt water with sea water, as well as the prevailing currents which churn the deeper waters, stir the environment and change the available nutrient levels. When the hours of sunlight, water temperature and nutrient levels reach optimum peak, the quiescent year-round phytoplankton population begins to reproduce explosively. By late summer, the blooms often span hundreds and even thousands of kilometers across the North Atlantic and Arctic Oceans.
The different colors seen from space are caused by different species, as well as the depth at which the organisms ride beneath the surface. The milky tones seen in the turquoise color in this image suggests the presence of coccolithophores – a type of phytoplankton that contains calcium carbonate. Different species also tend to have peak growth at different times. The Barents Sea usually hosts two major blooms each year, with diatoms peaking in May and June. Later in the year, as certain nutrients become depleted and the waters grow warmer and become more layered (stratified), colonies of coccolithophores surge to the fore, and expand across the expanse of the Barents Sea.
While phytoplankton blooms in this region are common, a clear summer-time view is not. The Barents Sea is cloud-covered about 80 percent of the time in summer. In this image, clouds cover most of the Scandinavian Peninsula as well as the western and northern Barents Sea. But where they part, the stunning colors of the huge bloom can be clearly seen. In the northwest section of the image, winds blowing towards the northeast over Bear Island have induced a ship-wave-shape wave in the cloud bank.