Study Finds Earth's Ocean Abyss Has Not Warmed
 
Oct. 6, 2014: The cold waters of Earth's deep ocean have not warmed
measurably since 2005, according to a new NASA study, leaving unsolved the
mystery of why global warming appears to have slowed in recent years.
 
Scientists at NASA's Jet Propulsion Laboratory (JPL) in Pasadena,
California, analyzed satellite and direct ocean temperature data from 2005
to 2013 and found the ocean abyss below 1.24 miles (1,995 meters) has not
warmed measurably. Study coauthor Josh Willis of JPL said these findings do
not throw suspicion on climate change itself.
 
"The sea level is still rising," Willis noted. "We're just
trying to understand the nitty-gritty details."
 
http://www.nasa.gov/sites/default/files/anemone-full.jpg
 
Deep sea creatures, like these anemones at a hydrothermal vent, are not yet
feeling the heat from global climate change. Although the top half of the
ocean continues to warm, the bottom half has not increased measurably in
temperature in the last decade. Image credit: NERC
 
In the 21st century, greenhouse gases have continued to accumulate in the
atmosphere, just as they did in the 20th century, but global average
surface air temperatures have stopped rising in tandem with the gases. The
temperature of the top half of the world's oceans -- above the 1.24-mile
mark -- is still climbing, but not fast enough to account for the stalled
air temperatures.
 
Many processes on land, air and sea have been invoked to explain what is
happening to the "missing" heat. One of the most prominent ideas
is that the bottom half of the ocean is taking up the slack, but supporting
evidence is slim. This latest study is the first to test the idea using
satellite observations, as well as direct temperature measurements of the
upper ocean. Scientists have been taking the temperature of the top half of
the ocean directly since 2005, using a network of 3,000 floating
temperature probes called the Argo array.
 
"The deep parts of the ocean are harder to measure," said JPL's
William Llovel, lead author of the study published Sunday in the journal
Nature Climate Change. "The combination of satellite and direct
temperature data gives us a glimpse of how much sea level rise is due to
deep warming. The answer is -- not much."
 
The study took advantage of the fact that water expands as it gets warmer.
The sea level is rising because of this expansion and the water added by
glacier and ice sheet melt.
 
http://www.nasa.gov/multimedia/imagegallery/image_feature_2515.html
 
While the upper part of the world's oceans continue to absorb heat from
global warming, ocean depths have not warmed measurably in the last decade.
This image shows heat radiating from the Pacific Ocean as imaged by the
NASA's Clouds and the Earth's Radiant Energy System instrument on the Terra
satellite. (Blue regions indicate thick cloud cover.) Image credit: NASA To
arrive at their conclusion, the JPL scientists did a straightforward
subtraction calculation, using data for 2005-2013 from the Argo buoys,
NASA's Jason-1 and Jason-2 satellites, and the agency's Gravity Recovery
and Climate Experiment (GRACE) satellites. From the total amount of sea
level rise, they subtracted the amount of rise from the expansion in the
upper ocean, and the amount of rise that came from added meltwater. The
remainder represented the amount of sea level rise caused by warming in the
deep ocean.
 
The remainder was essentially zero. Deep ocean warming contributed
virtually nothing to sea level rise during this period.
 
Coauthor Felix Landerer of JPL noted that during the same period warming in
the top half of the ocean continued unabated, an unequivocal sign that our
planet is heating up. Some recent studies reporting deep-ocean warming
were, in fact, referring to the warming in the upper half of the ocean but
below the topmost layer, which ends about 0.4 mile (700 meters) down.
 
Landerer also is a coauthor of another paper in the same journal issue on
1970-2005 ocean warming in the Southern Hemisphere. Before Argo floats were
deployed, temperature measurements in the Southern Ocean were spotty, at
best. Using satellite measurements and climate simulations of sea level
changes around the world, the new study found the global ocean absorbed far
more heat in those 35 years than previously thought -- a whopping 24 to 58
percent more than early estimates.
 
Both papers result from the work of the newly formed NASA Sea Level Change
Team, an interdisciplinary group tasked with using NASA satellite data to
improve the accuracy and scale of current and future estimates of sea level
change. The Southern Hemisphere paper was led by three scientists at
Lawrence Livermore National Laboratory in Livermore, California.
 
Credits:
Production editor: Dr. Tony Phillips | Credit: Science{at}NASA
 
More information:
 
NASA monitors Earth's vital signs from land, air and space with a fleet of
satellites and ambitious airborne and ground-based observation campaigns.
NASA develops new ways to observe and study Earth's interconnected natural
systems with long-term data records and computer analysis tools to better
see how our planet is changing. The agency shares this unique knowledge
with the global community and works with institutions in the United States
and around the world that contribute to understanding and protecting our
home planet.
 
For more information about NASA's Earth science activities in 2014, visit:
http://www.nasa.gov/earthrightnow
 
For more information on ocean surface topography from space, visit:
http://sealevel.jpl.nasa.gov
 
More information on NASA's GRACE satellites is available at:
http://grace.jpl.nasa.gov
 
For more information on the Argo array, visit: http://www.argo.ucsd.edu/index.html
 
 
Regards,
 
Roger

--- D'Bridge 3.99