Karman Vortex, Canary Islands

This false-colour Envisat image highlights a unique cloud formation, created by ‘Von Karman vortices’, south of the Canary Island archipelago, some 95 km from the northwest coast of Africa (right) in the Atlantic Ocean.

Von Karman vortices, named after aeronautical engineer Theodore von Karman, form as air flows around an object in its path, causing it to separate and create eddies in its wake. The clockwise and counterclockwise spirals in this image were created as wind blowing from the north over the Atlantic was disturbed by the archipelago.

Seven larger islands and a few smaller ones make up the Canaries; the larger islands are (left to right): El Hierro, La Palma, La Gomera, Tenerife, Gran Canaria, Fuerteventura and Lanzarote.

Tenerife is the largest of the Canaries, while Gran Canaria is the most populated. UNESCO declared La Palma a Biosphere Reserve in 1983.

This image was acquired by Envisat’s Medium Resolution Imaging Spectrometer on 6 June 2010 at a resolution of 300 m.

Arctic Bloom, Barents Sea

This Envisat image captures a plankton bloom larger than the country of Greece stretching across the Barents Sea off the tip of northern Europe.

The colourful blossoming bloom in the Barents Sea, a rather deep shelf sea with an average depth around 230 m, is approximately 136 000 sq km. In comparison, Greece has a land area of 131 940 sq km. The land visible across the bottom of the image belongs to Norway (left) and Russia’s Murmansk Oblast.

Plankton, the most abundant type of life found in the ocean, are microscopic marine plants that drift on or near the surface of the sea. Microscopic plankton have been called 'the grass of the sea' because they are the basic food on which all other marine life depends. Since plankton contain photosynthetic chlorophyll pigments, these simple organisms also play a similar role to terrestrial ‘green’ plants in the photosynthetic process. Plankton are able to convert inorganic compounds such as water, nitrogen and carbon into complex organic materials.

With their ability to 'digest' these compounds, they are credited with removing as much carbon dioxide from the atmosphere as their earthbound 'cousins'. As a result, the oceans have a profound influence on climate. Since plankton are a major influence on the amount of carbon in the atmosphere and are sensitive to environmental changes, it is important to monitor and model them into calculations of future climate change.

Although some types of plankton are individually microscopic, the chlorophyll they use for photosynthesis collectively tints the colour of the surrounding ocean waters, providing a means of detecting these tiny organisms from space with dedicated 'ocean colour' sensors, such as Envisat's Medium Resolution Imaging Spectrometer (MERIS) instrument, onboard satellites.

MERIS’s primary objective is to provide quantitative ocean-colour measurements, but the sensor has enough flexibility to serve applications in atmospheric and land-surface science as well.

MERIS acquired this image on 19 August 2009 by while working in Full Resolution mode to provide a spatial resolution of 300 m.