Although the temperature of the ocean's top half continues to rise




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 ocean -- above the 1.24-mile mark -- is still climbing, but not fast enough to account for the stalled air temperatures.


"The deep parts of the ocean are harder to measure," said JPL's William Llovel, lead author of the study, published Sunday, Oct. 5 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 water added by glacier and ice sheet melt.

To arrive at their conclusion, the JPL scientists did a straightforward subtraction calculation, using data for 2005 to 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.



Landerer also is a coauthor of another paper in the same Nature Climate Change journal issue on ocean warming in the Southern Hemisphere from 1970 to 2005. 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.




For more information on ocean surface topography from space, visit:

More information on NASA's GRACE satellites is available at:

For more information on the Argo array, visit:

News Media Contact

Alan Buis
Jet Propulsion Laboratory, Pasadena, California

Steve Cole
NASA Headquarters, Washington

Written by Carol Rasmussen
NASA Earth Science News Team