© unknownMonthly Values for the PDO Index, January 1900 to September 2008. Positive (red) index values indicate a warm phase PDO; negative (blue) index values indicate a cool phase PDO. While short-term flips in PDO phases do occur, evaluation of 20th century instrumental records has shown that PDO phases generally persist for 20-30 years, as indicated in this figure. To download the data, see Nate Mantua’s PDO page.
Changes in Net Flow of Ocean Heat Correlate with Past Climate Anomalies
Physicists at the University of Rochester have combed through data from satellites and ocean buoys and found evidence that in the last 50 years, the net flow of heat into and out of the oceans has changed direction three times.
These shifts in the balance of heat absorbed from the sun and radiated from the oceans correlate well with past anomalies that have been associated with abrupt shifts in the earth's climate, say the researchers. These anomalies include changes in normal storm intensities, unusual land temperatures, and a large drop in salmon populations along the western United States.
The physicists also say these changes in ocean heat-flow direction should be taken into account when predicting global climate because the oceans represent 90 percent of the total heat in the earth's climate system.
The study, which will appear in an upcoming issue of Physics Letters A, differs from most previous studies in two ways, the researchers say. First, the physicists look at the overall heat content of the Earth's climate system, measuring the net balance of radiation from both the sun and Earth. And second, it analyzes more completely the data sets the researchers believe are of the highest quality, and not those that are less robust.
"These shifts happened relatively abruptly," says David Douglass, professor of physics at the University of Rochester, and co-author of the paper. "One, for example, happened between 1976 and 1977, right when a number of other climate-related phenomenona were happening, such as significant changes in U. S. precipitation."
