Oceans Stored More Heat than They Released Since 1993
Ocean Stored Significant Warming Over
Last 16 Years
NOAA.gov,
May 19, 2010
The upper layer of the world’s ocean has warmed
since 1993, indicating a strong climate change signal, according to a
new study. The energy stored is enough to power nearly 500 100-watt
light bulbs per each of the roughly 6.7 billion people on the planet
continuously over the 16-year study period
“We are seeing the global ocean store more heat
than it gives off,” said John Lyman, an oceanographer at NOAA’s Joint
Institute for Marine and Atmospheric Research, who led an international
team of scientists that analyzed nine different estimates of heat
content in the upper ocean from 1993 to 2008.
The team combined the estimates to assess the
size and certainty of growing heat storage in the ocean. Their findings
will be published in the May 20 edition of the journal Nature. The
scientists are from NOAA, NASA, the Met Office Hadley Centre in the
United Kingdom, the University of Hamburg in Germany and the
Meteorological Research Institute in Japan.
“The ocean is the biggest reservoir for heat in
the climate system,” said Josh Willis, an oceanographer at NASA’s Jet
Propulsion Laboratory and one of the scientists who contributed to the
study. “So as the planet warms, we’re finding that 80 to 90 percent of
the increased heat ends up in the ocean.”
A warming ocean is a direct cause of global sea level rise, since
seawater expands and takes up more space as it heats up. The scientists
say that this expansion accounts for about one-third to one-half of
global sea level rise.
Combining multiple estimates of heat in the
upper ocean – from the surface to about 2,000 feet down – the team found
a strong multi-year warming trend throughout the world’s ocean.
According to measurements by an array of autonomous free-floating ocean
floats called Argo as well as by earlier devices called expendable
bathythermographs or XBTs that were dropped from ships to obtain
temperature data, ocean heat content has increased over the last 16
years.
The team notes that there are still some
uncertainties and some biases.
“The XBT data give us vital information about
past changes in the ocean, but they are not as accurate as the more
recent Argo data,” said Gregory Johnson, an oceanographer at NOAA’s
Pacific Marine Environmental Laboratory. “However, our analysis of these
data gives us confidence that on average, the ocean has warmed over the
past decade and a half, signaling a climate imbalance.”
Data from the array of Argo floats – deployed by NOAA and other U.S.
and international partners – greatly reduce the uncertainties in
estimates of ocean heat content over the past several years, the team
said. There are now more than 3,200 Argo floats distributed throughout
the world’s ocean sending back information via satellite on temperature,
salinity, currents and other ocean properties.
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