February 28, 2007
GCRIO Program Overview
Our extensive collection of documents.
Archives of the
Global Climate Change Digest
A Guide to Information on Greenhouse Gases and Ozone Depletion
Published July 1988 through June 1999
FROM VOLUME 12, NUMBER 5, MAY 1999
Oceanic Minerals: Their Origin, Nature of Their Environment, and
Significance, M. Kastner, Proc. Natl. Acad. Sci. USA, 96,
3380-3387 (March 1999).
Dense cold water plunges beneath the surface in the North Atlantic,
spreads along the bottoms of the worlds oceans, and is replaced by
the northward transport of warm water. The circulation patterns of the
oceans have changed over geologic time, and indicators of global
environmental changes are stored in deposits of marine minerals, such as
nodules and crusts that scavenge and incorporate trace elements. The work
here demonstrates that variations in these depositions allow measurement
of changes, such as those in ocean circulation and in climate, even though
these nodules grow at only 1 to 10 mm per million years.
Global Warming and Marine Carbon Cycle Feedbacks on Future
Atmospheric CO2, F. Joos et al., Science, 284
(5413), 464-467 (1999).
A simple model that represents the oceans, the atmosphere, and the
marine and terrestrial biospheres was run with a large variety of CO2
atmospheric concentrations. It indicated that, at high CO2 concentrations,
the North Atlantic circulation collapses; the resulting decrease in mixing
reduces CO2 uptake in that region significantly. At lesser increases in
CO2 concentration, sea-surface warming occurs, which also decreases CO2
uptake. But, it also modifies the marine biological cycle slightly,
allowing that cycle to compensate for the decreased mixing brought on by
the slowing of the oceans circulation.
Influence of El Niño on the Equatorial Pacific
Contribution to Atmospheric CO2 Accumulation, R. A. Feely et al.,
Nature 398, 597-601 (1999).
The equatorial oceans are the dominant oceanic source of carbon dioxide
to the atmosphere, annually releasing 0.7 to 1.5 Pg of carbon as CO2. The
equatorial Pacific has high seawater carbon dioxide and nutrient
concentrations provided by the upwelling of CO2-rich water to the surface.
As a result, the region is a major site for release of carbon dioxide from
the ocean interior to the atmosphere. Direct measurements in the
equatorial Pacific from 1992 to 1996 indicate that during strong El Niño
events, the release rate of CO2 from the ocean to the atmosphere was
reduced to 30 to 80% of that of non-El Niño periods. This decline
in the upwelling is caused by a relaxation of the normal easterly winds,
and the resulting decrease in carbon dioxide released from the sea into
the air is large enough to be seen as an atmospheric CO2 anomaly. The
total reduction of the sea-to-air carbon dioxide exchange during the
1991-94 El Niño is estimated to be 0.8 to 1.2 PgC, which is
equivalent to 16 to 36% of the decline of the growth rate of CO2 in the
atmosphere observed over the same period. Because more carbon dioxide is
retained by the oceans during strong El Niño events, changes in the
frequency of El Niño events may have a profound impact on the
sea-to-air exchange of carbon dioxide.
Variability of Inorganic and Organic Phosphorus Turnover Rates
in the Coastal Ocean, C. R. Benitez-Nelson and K. O. Buesseler, Nature,
398, 502-505 (1999).
The activities of two cosmogenic phosphorus nuclides were measured in
situ in a coastal marine environment to assess phosphorus turnover rates.
Dissolved inorganic, dissolved organic, and total phosphorus were measured
for a full seasonal cycle. The study showed that turnover rates are rapid
and vary seasonally, implying that low phosphorus concentrations can
support high rates of primary production. Picoplankton were found to
preferentially use dissolved organic phosphorus compounds to obtain carbon
and nitrogen. These results indicate that the roles of phosphorus in
supporting primary production have been underestimated.
Increased El Niño Frequency in a Climate Model Forced by
Future Greenhouse Warming, A. Timmermann et al., Nature,
398, 694-697 (1999).
A model was developed that had sufficiently high resolution in the
tropics to represent the equatorial upwelling and low-frequency waves.
When an enhanced-CO2 atmosphere is simulated, the model results indicate
(1) more frequent El Niño events and (2) stronger cold events in
the tropical Pacific Ocean.
Continental-Shelf Sediment as a Primary Source of Iron for
Coastal Phytoplankton, K. S. Johnson, F. P. Chavez, and G. E.
Friederich, Nature, 398, 697-700 (1999).
Phytoplankton primary productivity is frequently limited by iron
availability in the equatorial Pacific Ocean. Measurements of soluble iron
across the California Current System revealed high iron concentrations
during periods of strong upwelling and low concentrations during El Niños.
The low-iron periods in the study corresponded to periods of high efflux
from rivers and low offshore salinity. These results indicate that the
primary source of iron in the upper ocean is resuspension of benthic-layer
particles that are carried to the surface by upwelling.
Guide to Publishers
Index of Abbreviations