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Science Forum Index » Environment Forum » CALIFORNIA:Studies show global warminG to drive big changes
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| Economic Democracy |
 Posted: Thu Dec 18, 2003 6:05 pm |
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Public release date: 17-Dec-2003
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Contact: Tim Stephens
stephens@ucsc.edu
831-459-2495
University of California - Santa Cruz
Studies show global warming is likely to drive big changes in
California's coastal waters
Effects seen in intensity and timing of wind-driven upwelling
SANTA CRUZ, CA--Global warming could have profound effects on the
wind-driven upwelling of deep ocean water along the California coast,
according to recent studies by researchers at the University of
California, Santa Cruz. The studies showed changes in both the
intensity and the seasonal timing of the upwelling, which brings cold,
nutrient-rich water into coastal ecosystems.
This seasonal upwelling supports California's diverse marine life and
productive fisheries, but how changes in the upwelling will affect
these and other aspects of coastal ecosystems remains uncertain. The
researchers, led by professor of Earth sciences Lisa Sloan, used
computer simulations of the regional climate to show that wind-driven
upwelling along the California coast will likely intensify over the
next 50 years as a result of increased concentrations of carbon
dioxide in the atmosphere. In addition, the models showed the
upwelling season extending later into the fall.
The first set of experiments was published in the August 14 issue of
Geophysical Research Letters (GRL), and a second paper with additional
findings will be published online this week by the Proceedings of the
National Academy of Sciences (PNAS).
Previous studies by other researchers found that the intensity of
upwelling along the California coast has been increasing over the past
30 years, leading some to speculate that the trend is a result of
global warming, said Mark Snyder, lead author of the GRL paper. Snyder
earned his Ph.D. this month working with Sloan.
"Some people think we may already be seeing the effects of climate
change on the upwelling regime, so we thought we would use our climate
models to see how increases in greenhouse gases would affect the winds
that drive the upwelling," he said.
These winds are the result of differences in atmospheric pressure over
the land and the ocean that develop because the land surface heats up
faster than the ocean surface. Similarly, global warming could be
expected to raise temperatures more over land than over the ocean,
making the differences in atmospheric pressure even greater and
creating stronger winds. Sloan's group set out to test this hypothesis
using powerful computers to run complex models of the climate system.
The researchers used a high-resolution regional climate model,
centered over California and driven by inputs from a global climate
model with coarser resolution, to look at the effects of rising
concentrations of carbon dioxide in the atmosphere. Concentrations of
carbon dioxide, a greenhouse gas that traps heat in the atmosphere,
are increasing due to emissions from the burning of fossil fuels.
The first set of experiments, published in the GRL paper, showed that
with increasing carbon dioxide in the atmosphere, the intensity of
upwelling is decreased in the early season (April to May) and is
dramatically increased during the peak season (typically July to
August). The results also showed the duration of the upwelling season
extends further into the fall.
"The increase we saw in the upwelling intensity in the peak season
supports some of the observational work showing a trend toward
increased upwelling intensity in the present day," Snyder said.
The new results just published by PNAS reinforce these findings. In
these experiments, the researchers included the effects on the climate
system of changes in vegetation that are likely to occur with
increased atmospheric carbon dioxide. The results showed the same
general effects on upwelling as in the previous studies, only more
pronounced, said postdoctoral researcher Noah Diffenbaugh, lead author
of the PNAS paper.
"The interactions between vegetation and climate that are set in
motion by increasing carbon dioxide concentrations enhance the effects
on the upwelling regime," Diffenbaugh said.
The projected changes in vegetation result from warmer and dryer
conditions created by global warming and lead to changes in the
overall energy balance of the land surface, he said.
Diffenbaugh cautioned, however, that despite the complexity of the
climate models, they still represent a simplified view of an
extraordinarily complicated system of feedbacks and interactions.
Nevertheless, as human activities continue to pour more carbon dioxide
into the atmosphere, these studies show just how wide-ranging its
effects may be.
"The regional climate model is certainly the best tool we have at the
moment, and it shows us that elevated carbon dioxide is important not
only for its direct effects on the climate, but also because it
induces other changes that feed back into the climate system, and the
magnitudes of those feedbacks appear to be substantial," Diffenbaugh
said.
Researchers at UCSC and elsewhere are currently working to understand
how changes in upwelling conditions will affect fisheries and the
dynamics of coastal ecosystems. The new climate studies highlight the
importance of those efforts, Snyder said.
http://www.eurekalert.org/pub_releases/2003-12/uoc--ssg121703.php
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