[Waspie_Dwarf]

Spring Bloom in the South Atlantic Ocean

Satellite: Terra
Date Acquired: 11/15/2009
Resolutions:

1km (139.1 KB)
500m (446.9 KB)
250m (1.1 MB)

Bands Used: 1,4,3
Credit:

Jeff Schmaltz
MODIS Land Rapid Response Team, NASA GSFC

The South Atlantic Ocean off the coast of Argentina was streaked with beautiful green and blue color on November 15, 2009. This image was captured by the MODIS on the Terra satellite on the same day. The color is due to a phytoplankton bloom.

Phytoplankton are plant-like organisms that live in the surface waters of the ocean. They grow best in cool waters, where the temperature difference between the surface and the ocean’s depths is small enough to allow nutrient-rich deep water to mix with surface waters. A few different factors may be contributing to the bloom seen in this image. First, a cold current sweeps north from Antarctica along the coast of Argentina. Second, winds often drive upwelling along the continental shelf. Both the current and upwelling chill the South Atlantic in this region, making it possible for nutrient-rich deep water to reach the surface.

With access to nutrients and increasing springtime sunlight, phytoplankton thrive, developing into large blooms. There are probably many different kinds of phytoplankton growing in the waters off Argentina, accounting for the wide variations in color. Phytoplankton are the base of the marine food chain. Regular blooms such as this one make coastal Argentina a rich fishing ground.

Source: MODIS - Image of the Day

[Waspie_Dwarf]

Savage Islands, Atlantic Ocean

download large image (607 KB, JPEG) acquired October 22, 2009


download large image (385 KB, JPEG) acquired October 22, 2009

Image Location


The Savage Islands, or Ilhas Selvagens in Portuguese, are a small archipelago in the eastern North Atlantic Ocean between the archipelago of Madeira to the north and the Canary Islands to the south. Like these other island groups, the Savage Islands are thought to have been produced by volcanism related to a mantle plume or “hot spot.”

Typically, volcanoes are fueled by magma being generated where tectonic plates are colliding or being pulled apart. The active volcanoes remain at the plate boundaries, even as the plates shift. Mantle plumes, in contrast, are relatively fixed regions of upwelling magma that can feed volcanoes on an overlying tectonic plate. When a tectonic plate passes over the mantle plume, active volcanoes form, but they become dormant as they are carried away from the hot spot on the moving tectonic plate. Over geologic time, this creates a line of older, extinct volcanoes, seamounts, and islands extending from the active volcanoes that are currently over the plume.

These two astronaut photographs illustrate the northern (top) and southern (bottom) Savage Islands. The two views were taken 13 seconds apart from the International Space Station; the geographic center points of the images are separated by about 15 kilometers. Selvagem Grande, with an approximate area of 4 square kilometers, is the largest of the islands. The smaller and more irregularly-shaped Ilhéus do Norte, Ilhéu de Fora, and Selvagem Pequena are visible at the center of the lower image. Spain and Portugal both claim sovereignty over the Savage Islands.

All of the islands of the archipelago are ringed by bright white breaking waves along the fringing beaches. Coral reefs that surround the Savage Islands make it very difficult to land boats there, and there is no permanent settlement on the islands. The islands serve as nesting sites for several species of seabird including petrels and shearwaters, and they are included on the tentative list of additional UNESCO World Heritage Sites.

Astronaut photographs ISS021-E-11832 and ISS021-E-11833 were acquired on October 22, 2009, with a Nikon D2Xs digital camera fitted with an 800 mm lens, and are provided by the ISS Crew Earth Observations experiment and Image Science & Analysis Laboratory, Johnson Space Center. The images were taken by the Expedition 21 crew. The image in this article has been cropped and enhanced to improve contrast. Lens artifacts have been removed. The International Space Station Program supports the laboratory to help astronauts take pictures of Earth that will be of the greatest value to scientists and the public, and to make those images freely available on the Internet. Additional images taken by astronauts and cosmonauts can be viewed at the NASA/JSC Gateway to Astronaut Photography of Earth. Caption by William L. Stefanov, NASA-JSC.

Instrument: ISS - Digital Camera

Source: NASA - Earth Observatory - Image of the Day