Elvia Thompson<br />Headquarters, Washington October 1, 2003<br />(Phone: 202/358-1696)<br /><br /><br />Rob Gutro<br />Goddard Space Flight Center, Greenbelt, Md.<br />(Phone: 301/286-4044)<br /><br /><br />Mark Shwartz<br />Stanford University News Service, Calif.<br />(Phone: 650/723-9296)<br /><br /><br />RELEASE: 03-309<br /><br /><br />HUGE ANTARCTIC ICEBERG MAKES A BIG SPLASH ON SEA LIFE <br /><br /><br /> NASA satellites observed the calving, or breaking off, <br />of one of the largest icebergs ever recorded, named "C-19.<br /><br /><br />C-19 separated from the western face of the Ross Ice Shelf <br />in Antarctica in May 2002, splashed into the Ross Sea, and <br />virtually eliminated a valuable food source for marine life. <br />The event was unusual, because it was the second-largest <br />iceberg to calve in the region in 26 months.<br /><br /><br />Over the last year, the path of C-19 inhibited the growth of <br />minute, free-floating aquatic plants called phytoplankton <br />during the iceberg's temporary stopover near Pennell Bank, <br />Antarctica. C-19 is located along the Antarctic coast and <br />has diminished little in size. Since phytoplankton is at the <br />base of the food chain, C-19 affects the food source of <br />higher-level marine plants and animals.<br /><br /><br />Kevin R. Arrigo and Gert L. van Dijken of Stanford <br />University, Stanford, Calif., used chlorophyll data from <br />NASA's Sea-viewing Wide Field-of-view Sensor (SeaWiFS). The <br />instrument, on the OrbView-2 satellite, also known as <br />SeaStar, was used to locate and quantify the effects of C-19 <br />on phytoplankton. The researchers were able to pinpoint <br />iceberg positions by using images from the Moderate <br />Resolution Imaging Spectroradiometer (MODIS), an instrument <br />aboard NASA's Terra and Aqua satellites. The findings from <br />this NASA-funded study appeared in a recent issue of the <br />American Geophysical Union's Geophysical Research Letters.<br /><br /><br />C-19 is about twice the size of Rhode Island. When it broke <br />off the Ross Ice Shelf, the iceberg was 32 km (almost 20 <br />miles) wide and 200 km (124 miles) long. It was not as large <br />as the B-15 iceberg that broke off of the same ice shelf in <br />2001 but among the largest icebergs ever recorded.<br /><br /><br />Since it was so large, C-19 blocked sea ice from moving out <br />of the southwestern Ross Sea region. The blockage resulted <br />in unusually high sea-ice cover during the spring and <br />summer. Consequently, light was blocked. Phytoplankton <br />blooms that occur on the ocean surface were dramatically <br />diminished, and primary production was reduced by over 90 <br />percent, relative to normal years.<br /><br /><br />Primary production is the formation of new plant matter by <br />microscopic plants through photosynthesis. Phytoplankton is <br />at the base of the food chain. If they are not able to <br />accomplish photosynthesis, all organisms above them in the <br />food chain will be affected. "Calving events over the last <br />two decades indicate reduced primary productivity may be a <br />typical consequence of large icebergs that drift through the <br />southwestern Ross Sea during spring and summer," Arrigo <br />said.<br /><br /><br />Arrigo and van Dijken also used imagery from the Defense <br />Meteorological Satellite Program (DMSP) satellite Special <br />Sensor Microwave Imager and Scanning Multichannel Microwave <br />Radiometer, managed by the U.S. Department of Defense. The <br />data was used to monitor the impact of C-19 on the movement <br />of sea ice. The data is archived at the National Snow and <br />Ice Data Center, University of Colorado, Boulder.<br /><br /><br />Arrigo said most of the face of the Ross Ice Shelf has <br />already calved. There is another large crack, but it is very <br />difficult to predict if and when another large iceberg will <br />result. <br /><br /><br />NASA's Earth Science Enterprise is dedicated to <br />understanding the Earth as an integrated system and applying <br />Earth System Science to improve prediction of climate, <br />weather, and natural hazards using the unique vantage point <br />of space.<br /><br /><br />For more information and images, on the Internet, visit:<br />http://www.gsfc.nasa.gov/topstory/2003/1010iceberg.html<br /><br /><br />For information about SeaWiFS on the Internet, visit:<br />http://seawifs.gsfc.nasa.gov/<br /><br /><br />For information about MODIS on the Internet, visit:<br />http://modis.gsfc.nasa.gov/<br /><br /><br />For information about DMSP, visit:<br />http://www.dmsp.ngdc.noaa.gov/