Press Release

NASA Study Links El Nino and Southern Ocean Changes

By SpaceRef Editor
March 5, 2002
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NASA researchers have found strong relationships between
El Niño episodes and changes in climate and sea ice cover
around Antarctica.

Identifying these relationships is important because it
provides new insights into the changing characteristics of the
Antarctic region and their role in Earth’s climate system.

The findings, published in the March 1 issue of the
American Meteorological Society’s Journal of Climate, show
that although the total ice coverage of the southern ocean has
not changed significantly over the last 20 years, the El Niño
and its related Southern Oscillation appear to affect regional
ice distributions. The oscillation is a recurring warming and
cooling of the surface ocean in the central and eastern
Pacific. El Niño refers to the warm phase of the oscillation.

“Understanding the connection between the Southern
Oscillation and southern ocean climate and the sea ice cover
will substantially improve our understanding of global
climate,” said Dr. Ron Kwok, a senior research scientist at
NASA’s Jet Propulsion Laboratory, Pasadena, Calif. “Our study
concludes that the southern ocean’s climate and ice cover is
somehow connected to climate in the tropical latitudes. While
we don’t know yet the cause-and-effect relationship between
the two, we do know the changes in sea ice cover cannot be
explained by local climate variations alone and are instead
linked to larger scale climate phenomena.”

The study was conducted by scientists at JPL and NASA’s
Goddard Space Flight Center, Greenbelt, Md. It is based on
data from 1982 to 1999. The NASA scientists also noted changes
in sea ice cover in regions not normally associated with El
Niño, such as the Weddell Sea east of the Antarctic peninsula.

The strongest links were observed in the Amundsen,
Bellingshausen and Weddell seas of the west Antarctic, where
the connections are localized and well defined. Within these
sectors, higher sea level pressure, warmer air temperature and
warmer sea surface temperature are generally associated with
the El Niño phase.

A number of observations in the scientific literature can
be explained by this El Niño Southern Oscillation connection.
Examples include a record decrease in sea ice coverage in the
Bellingshausen Sea from mid-1982 through early 1999; the
reduced sea ice concentration in the Ross Sea; and the
shortening of the ice season in the eastern Ross, Amundsen and
far western Weddell seas. Four El Niño episodes over the 17
year period occurred at the same time as ice cover retreats in
the Bellingshausen and Amundsen seas, showing unique
associations between the Southern Oscillation and this region
of the Antarctic.

“The study shows that the impact of El Niño is global and
that processes as remote as those in the polar regions are
affected,” said co-author Dr. J. Comiso, senior research
scientist from Goddard. “The effect can be profound since
these El Niño episodes affect the Weddell and Ross seas.
These areas are regarded as key sources of cold and dense
bottom water that influences global ocean circulation. Also,
the ice cover in the Bellingshausen Sea is the habitat for a
wide variety of marine life and is crucial to their survival.”

Data for the study were acquired from several sources,
including satellite data from the National Oceanic and
Atmospheric Administration, Washington, D.C.; climate data
from the joint data set of the National Centers for
Environmental Prediction, also in Washington, and the National
Center for Atmospheric Research, Boulder, Colo.; sea ice data
from the National Snow and Ice Data Center in Boulder; and sea
ice motion data from JPL’s Remote Sensing Group.

The complete paper, “Southern Ocean Climate and Sea Ice
Anomalies Associated with the Southern Oscillation,” is
available to journalists from Alan Buis at (818) 354-0474.

The American Meteorological Society is the nation’s
leading professional society for scientists in the atmospheric
and related sciences. The study was funded by the Cryospheric
Sciences Program within NASA’s Earth Science Enterprise, a
long-term research effort dedicated to understanding how
human-induced and natural changes affect our global
environment.

JPL is a division of the California Institute of
Technology in Pasadena.

SpaceRef staff editor.