NOAA Reports Recent Cooling Of Upper Ocean

Sep 21: The average temperature of the water near the top of the Earth's oceans has cooled significantly since 2003. The new research suggests that global warming trends are not always steady in their effects on ocean temperatures. Although the average temperature of the upper oceans has cooled significantly since 2003, the researchers say the decline is a fraction of the total ocean warming seen over the previous 48 years. Josh Willis, a co-author of the study at NASA's Jet Propulsion Laboratory, Pasadena, CA said, "This research suggests global warming isn't always steady but happens with occasional 'speed bumps.'" This cooling is probably natural climate variability. The oceans today are still warmer than they were during the 1980s, and most scientists expect the oceans will eventually continue to warm in response to human-induced climate change."

Researchers found that the average temperature of the upper ocean rose by 0.16 degrees Fahrenheit from 1993 to 2003, and then fell 0.055 degrees Fahrenheit from 2003 to 2005. The recent decrease is a dip equal to about one-fifth of the heat gained by the ocean between 1955 and 2003. John Lyman, at the NOAA Pacific Marine Environmental Laboratory in Seattle, WA, and said the recent cooling is not unprecedented. "While global ocean temperatures have generally increased over the past 50 years, there have also been substantial decadal decreases. Other studies have shown that a similar rapid cooling took place from 1980 to 1983. But overall, the long-term trend is warming."

Willis indicated the findings have significant implications for global sea-level rise saying, "Average sea level goes up partly due to warming and thermal expansion of the oceans and partly due to runoff from melting glaciers and ice sheets. The recent cooling episode suggests that sea level should have actually decreased in the past two years. Despite this, sea level has continued to rise. This may mean that sea level rise has recently shifted from being mostly caused by warming to being dominated by melting. This idea is consistent with recent estimates of ice-mass loss in Antarctica and accelerating ice-mass loss on Greenland."

Access a lengthy release from NOAA and links to additional information (click here). Access a 15-page technical paper on the study (click here). [*Climate]