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AGU Journal European Highlights - 21 June 2002

June 21, 2002

American Geophysical Union
AGU Journal European Highlights - 21 June 2002

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The following highlights are from Geophysical Research Letters
(GRL) and the Journal of Geophysical Research-Atmospheres
(JGR-D). The research papers related to these Highlights will be
printed in the next paper issues of the respective journals following
their electronic publication.

Please note: We will be able to send copies of the highlighted
papers only from Monday, 24 June.

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2. Ecosystem evolution within an ocean vortex

Oceanic temperature and circulation instability near the Equator
can form a vortex that affects the cycle of marine life by mixing
the distribution of nutrients and carbon dioxide distributed within
equatorial ecosystems. The "equatorial vortices" are similar to
three-dimensional water cyclones that blend cooler, nutrient-rich
streams and warmer, nutrient-poor waters, drawing plankton,
nutrients and small pelagic fish down into its circulation. Menkes
et al. ["A whirling ecosystem in the Equatorial Atlantic"] perform
the first biological and physical measurements of these processes
in the equatorial oceans in a study that they believe can be used to
set a framework to understand how equatorial vortices affect the
marine ecosystem. Using satellite data to identify the large, cusp-
like waves that form the vortices, their observations demonstrate
how a complex ecosystem evolves within a large ocean vortex
associated with tropical instability waves in the equatorial Atlantic
Ocean. The study is an example of how biological variability is
driven by the physical actions of the ocean.

Authors:
Christophe E. Menkes, Yves Dandonneau, Sebastien Masson,
Benjamin Biessy, Emile Marchal, Gerard Eldin, Jacques Grelet,
Yves Montel, Alain Morliere, Anne Lebourges, Institut de
Recherche pour le Developpement (IRD) , Laboratoire
d`Oceanographie Dynamique et de Climatologie (LODYC)/
Universite Pierre et Marie Curie (UPMC), Paris, France;
Sean C. Kennan, Nova University Ocean Center, Dania Beach,
Florida;
Pierre Flament, University of Hawaii, Honolulu;
Cyril Moulin, LSCE, Gif sur Yvette, France;
Gisele Champalbert, LOB, Marseille, France;
Alain Herbland, CREMA, Nieul ser Mer, France.

Source: Geophysical Research Letters (GRL) paper
10.1029/2001GL014576, 2002

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5. Greenhouse gases and ocean warming

Does the anthropogenic increase in atmospheric greenhouse gases
affect the temperature and heat stored in the oceans? The oceans
that cover nearly three-fourths of Earth`s surface have the greatest
capacity to store heat of any component in Earth`s climate system.
Two years ago, oceanographer Sydney Levitus found that over the
last five decades, the upper 3000 meters [10,000 feet]warmed by
about 20 x 10^22 Joules. Now, Bernhard Reichert and colleagues
["Global ocean warming tied to anthropogenic forcing"] compare
the observed changes in ocean heat content with the predictions of
their European Center/Hamburg global climate model that couples
the oceans and atmosphere. They find that to get a good agreement
with Levitus` observations they have to include increasing
manmade greenhouse gas concentrations. They also include the
direct and indirect effect of sulfate aerosols and manmade changes
in tropospheric ozone. This finding agrees with two other recent
simulations that only achieved good agreement with the
observations when the effects of anthropogenic greenhouse gases
were included.

Authors:
Bernhard K Reichert, Reiner Schnur, and Lennart Bengtsson, Max
Planck Institute for Meteorology, Hamburg, Germany.
(Reichert is now at Lamont Doherty Earth Observatory, Columbia
University, Palisades, New York.)

Source: Geophysical Research Letters (GRL) paper
10.1029/2001GL013954, 2002

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10. Line-shaped contrails add less energy than previously
predicted

Contrails-the man-made clouds from high-flying aircraft-which
reflect sunlight and retain surface energy similarly to natural cirrus
clouds, add less energy to the atmosphere than previously
predicted. Ice clouds, like pollutants, affect the Earth`s energy
balance and influence global temperature changes. Meyer et al.
["Regional radiative forcing by line-shaped contrails derived from
satellite data"] analyzed two years of European contrail data
collected by satellite observations, finding that contrails add .03
Watts per square meter over Western Europe. The researchers used
more thorough data to infer much smaller heat contributions than
previous estimates, concluding that the effects from contrails are
similar to those from airborne exhaust gases like carbon dioxide,
nitrous oxides, and soot. The authors` calculation is significant,
because travel distance and the number of passengers is expected
to increase by a factor of six by the year 2050, according to an
international forecast. They note that their detection scheme
observes only recently formed contrails before the line shape
dissolves.

Authors:
R. Meyer, H. Mannstein, R. Meerkotter, U. Schumann, and
P. Wendling, German Center for Air and Space Travel,
Oberpfaffenhofen, Germany.

Source: Journal of Geophysical Research-Atmospheres (JGR-D)
paper 10.1029/2001JD000246, 2002
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American Geophysical Union (AGU)