|
Deepseawaters
Home Deepseawaters
ArticlesOcean temperatures and sea level increases 50 percent higher than previously estimated
Ocean temperatures and sea level increases 50 percent higher than previously estimated
Atmosphere
LIVERMORE, Calif. – New research suggests
that ocean temperature and associated sea level increases
between 1961 and 2003 were 50 percent larger than estimated
in the 2007 Intergovernmental Panel on Climate Change report.
The results are reported in the June 19 edition
of the journal Nature. An international team of researchers,
including Lawrence Livermore National Laboratory climate scientist
Peter Gleckler, compared climate models with improved observations
that show sea levels rose by 1.5 millimeters
per year in the period from 1961-2003. That equates to an
approximately 2½-inch increase in ocean levels in a 42-year
span.
The ocean warming and thermal expansion
rates are more than 50 percent larger than previous estimates
for the upper 300 meters of oceans.
The research corrected for small but systematic
biases recently discovered in the global ocean observing
system, and uses statistical techniques that “infill”
information in data-sparse regions. The results increase scientists’
confidence in ocean observations and further demonstrate that
climate models simulate ocean temperature
variability more realistically than previously thought.
a. The components are
thermal expansion in the upper 700 m (red), thermal expansion
in the deep ocean (orange), the ice sheets of Antarctica and
Greenland (cyan), glaciers and ice caps (dark blue) and terrestrial
storage (green). b. The estimated sea levels are indicated
by the black line (this study), the yellow dotted line and
the red dotted line (from satellite altimeter observations).
The sum of the contributions is shown by the blue line. Estimates
of one standard deviation error for the sea level are indicated
by the grey shading. For the sum of components, rigorous estimates
of one standard deviation error for upper-ocean thermal expansion
are included; these are shown by the thin blue lines. All
time series were smoothed with a three-year running average
and are relative to 1961.
“This is important for the climate
modeling community because it demonstrates that the climate
models used for assessing sea-level rise
and ocean warming tie in closely with the
observed results,” Gleckler said.
Climate model data were analyzed from 13
different modeling groups. All model data were obtained from
the WCRP CMIP3 multi-model dataset archived at the LLNL’s
Program for Climate Model Diagnosis and Intercomparison
(PCMDI).
Although observations and models confirm
that recent warming is greatest in the upper ocean, there
are widespread observations of warming deeper than 700 meters.
Results were compared with recent estimates of other contributions
to sea-level rise including glaciers, ice caps, Greenland
and Antarctic ice sheets, and thermal expansion changes in
the deep ocean. When these independent lines of evidence are
examined collectively, the story is more consistent than found
in earlier studies.
The oceans store more than 90 percent of
the heat in the Earth’s climate system and act as a
temporary buffer against the effects of climate change. The
ocean warming and thermal expansion rates
are 50 percent larger than previous estimates for the upper
700 meters of oceans, and greater than that for the upper
300 meters.
“This is just the tip of the iceberg, so to speak,”
Gleckler said. “Our ability to quantify structural uncertainties
in observationally based estimates is critically important.
This study represents important progress.”
The team involved researchers from the Centre for Australian
Weather and Climate Research (CSIRO), the Antarctic Climate
and Ecosystems Cooperative Research Centre and LLNL.
Founded in 1952, Lawrence Livermore National Laboratory is
a national security laboratory, with a mission to ensure national
security and apply science and technology to the important
issues of our time. Lawrence Livermore National Laboratory
is managed by Lawrence Livermore National Security, LLC for
the U.S. Department of Energy's National Nuclear Security
Administration.
 Email
To Friend
| 
