From: baalke@zagami.jpl.nasa.gov   
      
   David E. Steitz   
   Headquarters, Washington   
   (Phone: 202/358-1730)               September 16, 2003   
      
   Krishna Ramanujan	   
   Goddard Space Flight Center (GSFC), Greenbelt, Md   
   (Phone: 301/286-3026)   
      
   Kent LaBorde   
   NOAA, Washington   
   (Phone: 202/482-5757)   
      
   RELEASE: 03-285   
      
   OCEAN PLANT LIFE SLOWS DOWN AND ABSORBS LESS CARBON   
      
        Plant life in the world's oceans has become less   
   productive since the early 1980s, absorbing less carbon,   
   which may in turn impact the Earth's carbon cycle, according   
   to a study that combines NASA satellite data with NOAA   
   surface observations of marine plants.   
      
   Microscopic ocean plants called phytoplankton account for   
   about half the transfer of carbon dioxide (CO2) from the   
   environment into plant cells by photosynthesis. Land plants   
   pull in the other half. In the atmosphere, CO2 is a heat-   
   trapping greenhouse gas.   
      
   Watson Gregg, a NASA GSFC researcher and lead author of the   
   study, finds that the oceans' net primary productivity (NPP)   
   has declined more than 6 percent globally over the last two   
   decades, possibly as a result of climatic changes. NPP is the   
   rate at which plant cells take in CO2 during photosynthesis   
   from sunlight, using the carbon for growth. The NASA funded   
   study appears in a recent issue of Geophysical Research   
   Letters.   
      
   "This research shows ocean primary productivity is declining,   
   and it may be a result of climate changes such as increased   
   temperatures and decreased iron deposition into parts of the   
   oceans. This has major implications for the global carbon   
   cycle," Gregg said. Iron from trans-continental dust clouds   
   is an important nutrient for phytoplankton, and when lacking   
   can keep populations from growing.   
      
   Gregg and colleagues used two datasets from NASA satellites:   
   one from the Coastal Zone Color Scanner aboard NASA's Nimbus-   
   7 satellite (1979-1986); and another from Sea-viewing Wide   
   Field-of-view Sensor data on the OrbView-2 satellite (1997-   
   2002).   
      
   The satellites monitor the green pigment in plants, or   
   chlorophyll, which leads to estimates of phytoplankton   
   amounts. The older data was reanalyzed to conform to modern   
   standards, which helped make the two data records consistent   
   with each other. The sets were blended with surface data from   
   NOAA research vessels and buoys to reduce errors in the   
   satellite records and to create an improved estimate of NPP.   
      
   The authors found nearly 70 percent of the NPP global decline   
   per decade occurred in the high latitudes (above 30 degrees).   
   In the North Pacific and North Atlantic basins, phytoplankton   
   bloom rapidly in high concentrations in spring, leading to   
   shorter, more intense lifecycles. In these areas, plankton   
   quickly dies and can sink to the ocean floor, creating a   
   potential pathway of carbon from the atmosphere into the deep   
   ocean.   
      
   In the high latitudes, rates of plankton growth declined by 7   
   percent in the North Atlantic basin, 9 percent in the North   
   Pacific basin, and 10 percent in the Antarctic basin when   
   comparing the 1980s dataset with the late 1990s observations.   
      
   The decline in global ocean NPP corresponds with an increase   
   in global sea surface temperatures of 0.36 degrees Fahrenheit   
   (F) (0.2 degrees Celsius (C)) over the last 20 years. Warmer   
   water creates more distinct ocean layers and limits mixing of   
   deeper nutrient-rich cooler water with warmer surface water.   
   The lack of rising nutrients keeps phytoplankton growth in   
   check at the surface.   
      
   The North Atlantic and North Pacific experienced major   
   increases in sea surface temperatures: 0.7 degrees C (1.26 F)   
   and 0.4 degrees C (0.72 F) respectively. In the Antarctic,   
   there was less warming, but lower NPP was associated with   
   increased surface winds. These winds caused plankton to mix   
   downward, cutting exposure to sunlight.   
      
   Also, the amount of iron deposited from desert dust clouds   
   into the global oceans decreased by 25 percent over two   
   decades. These dust clouds blow across the oceans. Reductions   
   in NPP in the South Pacific were associated with a 35 percent   
   decline in atmospheric iron deposition.   
      
   "These results illustrate the complexities of climate change,   
   since there may be one or more processes, such as changes in   
   temperature and the intensity of winds, influencing how much   
   carbon dioxide is taken up by photosynthesis in the oceans,"   
   said co-author Margarita Conkright, a scientist at NOAA's   
   National Oceanographic Data Center, Silver Spring, Md.   
      
   Other recent NASA findings have shown land cover on Earth has   
   actually been greening. For information and images on the   
   Internet, visit:   
      
   http://www.nasa.gov/home/hqnews/2003/jun/HQ_03182_green_garde   
   n.html   
   &   
   http://www.gsfc.nasa.gov/topstory/2003/0815oceancarbon.html   
      
   -end-   
      
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