Surprising data suggests that deep ocean water is immune to global warming

The world’s oceans serve as the Earth’s primary heat uptake reservoir, but new research found that the temperatures of the deep ocean waters have remained constant over the past decade, nullifying the hypothesis that their warming may account for some sea level rise.

by John Tyburski

Copyright © Daily Digest News, KPR Media, LLC. All rights reserved.

First published at Daily Digest News on October 6, 2014

New research reported this week shows that the Earth’s cold waters of its deep ocean abysses are still cold after a decade of global warming. The report on trends in satellite and direct measurements of ocean water temperatures taken since January 2005 was published on Monday in the journal Nature Climate Change.

Researchers at the National Aeronautics and Space Administration’s (NASA) Jet Propulsion Laboratory (JPL) analyzed satellite data and direct ocean water temperature measurements from 2005 through 2013 and found that the that the water deeper than 1.24 miles below the surface had not warmed any measurable amount.

While so-called greenhouse gases have risen, the global surface air temperatures over the past 13 or so years have not. Upper level ocean water temperatures have risen but not rapidly enough to account for the stable air temperatures. Scientists hypothesized that the unaccounted-for heat was being absorbed by the deep ocean waters. Furthermore, many experts speculated that the missing heat, upon being found in the deep oceans, would confirm their hypothesis that expansion of these waters from their warming would account for the observed rise in global sea levels.

The new findings contradict these speculations, but they do not, the authors say, “throw suspicion” on global climate change.

“The sea level is still rising,” said study coauthor Josh Willis of JPL. “We’re just trying to understand the nitty-gritty details.”

Since deep ocean water temperatures are not accessible by direct measurement methods, the scientists used depth calculations based on data from NASA’s Jason-1, Jason-2, and Gravity Recovery and Climate Experiment (GRACE) satellites to estimate how much of the global sea level rise could be explained by warming of deep water, upper ocean water, and meltwater.

“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,” said JPL’s William Llovel, lead author of the study.