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Biospheric primary production during an ENSO transition.
M J Behrenfeld1, J T Randerson, C R McClain
1National Aeronautic and Space Administration, Goddard Space Flight Center, Greenbelt, MD 20771, USA. mjb@neptune.gsfc.nasa.gov
Science (New York, N.Y.)
|April 3, 2001
Summary
Global ocean and land plant productivity (NPP) were compared during an El Niño to La Niña shift. Ocean NPP increased, especially in tropics, while land NPP showed no clear global ENSO response.
Area of Science:
- Earth Science
- Oceanography
- Ecology
Background:
- The Sea-viewing Wide Field-of-view Sensor (SeaWiFS) provides crucial global data on oceanic phytoplankton and land plant light absorption.
- Understanding the Net Primary Production (NPP) of both marine and terrestrial ecosystems is vital for climate modeling and ecological studies.
Purpose of the Study:
- To compare the simultaneous Net Primary Production (NPP) responses of ocean and land ecosystems to a major El Niño to La Niña transition.
- To analyze the impact of the El Niño-Southern Oscillation (ENSO) on global and regional biospheric productivity.
Main Methods:
- Utilized SeaWiFS global monthly measurements of phytoplankton chlorophyll biomass and land plant light harvesting.
- Analyzed biospheric NPP variations between September 1997 and August 2000, encompassing an ENSO event.
Main Results:
- Biospheric NPP fluctuated by 6 petagrams of carbon per year, ranging from 111 to 117 Pg C yr⁻¹.
- Ocean NPP exhibited significant increases, particularly in tropical regions affected by ENSO-driven changes in upwelling and nutrient availability.
- Global land NPP did not show a consistent ENSO response, though substantial regional variations were observed.
Conclusions:
- The study highlights differential responses of ocean and land NPP to ENSO events.
- Tropical oceans are more sensitive to ENSO impacts on productivity than the global land biosphere.
- SeaWiFS data are invaluable for tracking large-scale environmental changes and their effects on primary production.
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