After the calving, or "breaking off," of the B-15 iceberg in March of 2000, researchers used imagery from NASA's SeaWiFS (Sea-viewing Wide Field-of-view Sensor) satellite and data from the Defense Meteorological Satellite Program to see the effect that large icebergs have on the blooms of phytoplankton, tiny floating plants. The B-15 iceberg that broke off the Ross Ice Shelf and drifted into the southwestern Ross Sea was as large as the state of Connecticut, about 3,900 square miles (10,000 square kilometers).

"This is the first time that satellite imagery has been used to document the potential for large icebergs to substantially alter the dynamics of a marine ecosystem," said Kevin Arrigo, a researcher at Stanford University. Arrigo and his colleagues are publishing their results in an upcoming issue of the journal Geophysical Research Letters.

NASA's Thorsten Markus of the Goddard Space Flight Center, a co-author on the paper, said SeaWiFS satellite imagery enabled researchers to see that large icebergs such as the B-15 restricted the normal drift of pack ice. Normally, when the winds shift, ice is carried out into the Ross Sea, creating open ocean space and a breeding ground for phytoplankton.

The icebergs, however, created a blockage that resulted in heavier spring/summer pack-ice cover than previously recorded.

The southwestern Ross Sea is one of the most biologically productive regions in the Southern Ocean surrounding Antarctica. In the springtime, winds normally shift in the area of the Ross Sea and clear away sea ice and allowing phytoplankton to flourish. However, when large icebergs calve, such as B-15, sea ice is not as easily moved by winds, severely reducing the area of open water.

Phytoplankton are a critical part of the entire ecosystem in the Ross Sea, since they sustain marine mammals and birds in the region, including penguins.