October 1, 2003
Huge Antarctic Iceberg Makes a Big Splash on Sea Life
NASA satellites observed the calving, or breaking off, of one of the
largest icebergs ever recorded, named "C-19."
C-19 separated from the western face of the Ross Ice Shelf in Antarctica
in May 2002, splashed into the Ross Sea, and virtually eliminated a valuable
food source for marine life. The event was unusual, because it was the
second-largest iceberg to calve in the region in 26 months.
Over the last year, the path of C-19 inhibited the growth of minute,
free-floating aquatic plants called phytoplankton during the iceberg's
temporary stopover near Pennell Bank, Antarctica. C-19 is located along
the Antarctic coast and has diminished little in size. Since phytoplankton
is at the base of the food chain, C-19 affects the food source of higher-level
marine plants and animals.
Kevin R. Arrigo and Gert L. van Dijken of Stanford University, Stanford,
Calif., used chlorophyll data from NASA's Sea-viewing Wide Field-of-view
Sensor (SeaWiFS). The instrument, on the OrbView-2 satellite, also known
as SeaStar, was used to locate and quantify the effects of C-19 on phytoplankton.
The researchers were able to pinpoint iceberg positions by using images
from the Moderate Resolution Imaging Spectroradiometer (MODIS), an instrument
aboard NASA's Terra and Aqua satellites. The findings from this NASA-funded
study appeared in a recent issue of the American Geophysical Union's
Geophysical Research Letters.
C-19 is about twice the size of Rhode Island. When it broke off the
Ross Ice Shelf, the iceberg was 32 km (almost 20 miles) wide and 200
km (124 miles) long. It was not as large as the B-15 iceberg that broke
off of the same ice shelf in 2001 but among the largest icebergs ever
recorded.
Since it was so large, C-19 blocked sea ice from moving out of the southwestern
Ross Sea region. The blockage resulted in unusually high sea-ice cover
during the spring and summer. Consequently, light was blocked. Phytoplankton
blooms that occur on the ocean surface were dramatically diminished,
and primary production was reduced by over 90 percent, relative to normal
years.
Primary production is the formation of new plant matter by microscopic
plants through photosynthesis. Phytoplankton is at the base of the food
chain. If they are not able to accomplish photosynthesis, all organisms
above them in the food chain will be affected. "Calving events over the
last two decades indicate reduced primary productivity may be a typical
consequence of large icebergs that drift through the southwestern Ross
Sea during spring and summer," Arrigo said.
Arrigo and van Dijken also used imagery from the Defense Meteorological
Satellite Program (DMSP) satellite Special Sensor Microwave Imager and
Scanning Multichannel Microwave Radiometer, managed by the U.S. Department
of Defense. The data was used to monitor the impact of C-19 on the movement
of sea ice. The data is archived at the National Snow and Ice Data Center,
University of Colorado, Boulder.
Arrigo said most of the face of the Ross Ice Shelf has already calved.
There is another large crack, but it is very difficult to predict if
and when another large iceberg will result.
NASA's Earth Science Enterprise is dedicated to understanding the Earth
as an integrated system and applying Earth System Science to improve
prediction of climate, weather, and natural hazards using the unique
vantage point of space.
For information about SeaWiFS on the Internet, visit:
http://seawifs.gsfc.nasa.gov/
For information about MODIS on the Internet, visit:
http://modis.gsfc.nasa.gov/
For information about DMSP, visit:
http://www.dmsp.ngdc.noaa.gov/
###
Contacts:
Elvia Thompson
Headquarters, Washington
(Phone: 202/358-1696)
Rob Gutro
Goddard Space Flight Center, Greenbelt, Md.
(Phone: 301/286-4044)
Mark Shwartz
Stanford University News Service, Calif.
(Phone: 650/723-9296) |
|
![Iceberg C-19 in the Ross Sea, Antarctica](https://webarchive.library.unt.edu/eot2008/20081013142928im_/http://earthobservatory.nasa.gov/Newsroom/NasaNews/ReleaseImages/20031001/c19_tn.jpg)
Iceberg C-19 in the Ross Sea, Antarctica
The C-1 iceberg broke off the Ross shelf in May 2002. This is an image
from NASA's Moderate Resolution Imaging Spectroradiometer (MODIS) on
the Terra satellite. CREDIT: NASA MODIS Rapid Response Team
High-Resolution
Image
![Movement of the C-19 Iceberg](https://webarchive.library.unt.edu/eot2008/20081013142928im_/http://earthobservatory.nasa.gov/Newsroom/NasaNews/ReleaseImages/20031001/map_tn.jpg)
Movement of the C-19 Iceberg
This is a map of the southwestern Ross Sea showing the drift path taken
by iceberg C-19 beginning May 11, 2002 and moving up in the diagram.
Also shown is the B-15A iceberg. CREDIT: Stanford University
![Animation of the Movement of the C-19 Iceberg](https://webarchive.library.unt.edu/eot2008/20081013142928im_/http://earthobservatory.nasa.gov/Newsroom/NasaNews/ReleaseImages/20031001/movie_tn.jpg)
Animation of the Movement of the C-19 Iceberg
The animation shows the B-15 (left) and C-19 (center) icebergs in the
Ross Sea and the movement of C-19 between September 22, 2002, and February
3, 2003. C-19 drifts from the center of the scene out to the far right
edge. CREDIT: NASA/GSFC Scientific Visualization Studio.
![](https://webarchive.library.unt.edu/eot2008/20081013142928im_/http://earthobservatory.nasa.gov/Newsroom/NasaNews/ReleaseImages/20031001/iceberg_tn.jpg)
Sea Ice Affects Sea Life
These images from the years 2000, 2001 & 2002 shows the greatest amount
of plankton in the Ross Sea occurred in 2000, as identified by yellow
and red colors indicating chlorophyll in the floating plants. In 2002,
more sea ice (dark gray) prevented plankton growth. Black areas are open
water regions obscured by clouds. Major icebergs are in white and are
labeled. CREDIT: Stanford University
![25 Years of Polynyas (Open Water Areas)](https://webarchive.library.unt.edu/eot2008/20081013142928im_/http://earthobservatory.nasa.gov/Newsroom/NasaNews/ReleaseImages/20031001/graph_tn.jpg)
25 Years of Polynyas (Open Water Areas)
This chart depicts a 25 year record of area covered by polynya in the
Ross Sea. In 2002, the area of polynyas, areas of open water surrounded
by ice, is much lower than previous years, likely because of the extraordinarily
high sea ice concentrations likely due to the calving of iceberg C-19.
Polynyas form in areas where the wind blows the ice away or where warm
water moves up from lower depths and melts the ice cover. CREDIT: Stanford
University |