EL NINO'S DRAMATIC
IMPACT ON OCEAN BIOLOGY,
CARBON DIOXIDE CAPTURED BY
UNIQUE MONITORING SYSTEM
The 1997-98 El Nino/La Nina had an unprecedented roller-coaster effect
on the oceanic food chain across a vast swath of the Pacific, plunging chlorophyll
levels to the lowest ever recorded in December 1997 and spawning the largest
bloom of microscopic algae ever seen in the region the following summer.
According to new results published in the Dec. 10 issue of the journal
Science, El Nino also dramatically reduced the amount
of carbon dioxide normally released into the atmosphere by the
equatorial Pacific Ocean.
Data from an array of instruments on buoys, ships and in space,
including NASA's Sea-viewing Wide Field-of-View Sensor (SeaWiFS), gave
researchers an unprecedented view into the extreme biological effects
of this El Nino/La Nina event.
"With SeaWiFS in orbit, we were able to see for the first time not
only the vast size and intensity of the ocean's biological rebound from
El Nino, but also the unbelievable speed of that recovery," said
Goddard Space Flight Center (Greenbelt, Md.) oceanographer Dr. Gene
Feldman, a co-author of the study. SeaWiFS provides daily views of the
world's oceans and land masses.
Over the past decade scientists have been able to observe the
development and progression of El Nino warmings, and consequent changes
in upwelling of nutrient-rich ocean waters, thanks to data continuously
collected in the Pacific by the buoys of the National Oceanic and
Atmospheric Administration's Tropical Atmosphere Ocean array.
In 1996 new biological and chemical sensors were added to some of
these buoys by the Monterey Bay Aquarium Research Institute (MBARI),
allowing researchers for the first time to directly and continuously
monitor biological productivity and the concentration of carbon dioxide
in the region. The launch of SeaWiFS in 1997 added yet another
ocean-monitoring tool capable of detecting subtle changes in ocean
color that are directly related to the concentration of chlorophyll, a
prime indicator of biological activity in ocean waters. The largest
reservoir of chlorophyll in the ocean is in the phytoplankton (a
microscopic form of algae), which forms the base of the oceanic food
"This is the first time we've ever had a set of biological
measurements from moored instruments and satellites during an intense
El Nino, and we've never seen such low chlorophyll concentrations,"
said MBARI biological oceanographer Francisco Chavez, lead author of
It was the buoy measurements and SeaWiFS data that revealed
surprisingly low and then high levels of chlorophyll coinciding with El
Nino's strongest phase and the recovery period and transition to La
Nina cooling. When the warm-water layer produced by El Nino extended
to its greatest depths and the upwelling of nutrients necessary for
phytoplankton growth virtually ceased, chlorophyll values plummeted.
The researchers were again surprised in mid-1998 when chlorophyll
levels skyrocketed, revealing the largest phytoplankton bloom, in area,
ever observed in the equatorial Pacific. In their published results,
the researchers suggest that elevated iron concentrations stimulated
this intense bloom, a result of the increased upwelling associated with
El Nino also drastically reduced the amount of carbon dioxide this
ocean region adds to the atmosphere. Unlike most parts of the world's
oceans, the equatorial Pacific is normally a major contributor to
atmospheric carbon dioxide due to the carbon-dioxide-rich deep ocean
waters brought to the surface here and the relatively low levels of
The researchers calculate that the amount of carbon dioxide released to
the atmosphere by the equatorial Pacific during the year of El Nino
conditions was 700 million metric tons of carbon less than the previous
year. This is equivalent to half of the United States' total annual
carbon dioxide emissions from fossil fuel burning.
Credit line for all images:
NASA/Goddard Space Flight Center
The SeaWiFS Project and ORBIMAGE
Scientific Visualization Studio
NOTE: All SeaWiFS images and data presented on this website are for research and educational use only. All commercial use of SeaWiFS data must be coordinated with ORBIMAGE.