World's Oceans Warming Up
By Cat Lazaroff
WASHINGTON, DC (ENS) - The oceans of the world have warmed substantially during the past 40 years, the National Oceanic and Atmospheric Administration announced Thursday. NOAA researchers suggest that much of the heat from global warming may have been stored in the oceans, reducing atmospheric temperature increases but leading to potentially huge climate changes in the near future.
Ocean warming could signal more impending global warming (Photo courtesy Ocean-Atmosphere Carbon Exchange Study)
Researchers from NOAA's Ocean Climate Laboratory in Silver Spring, Maryland examined three major ocean basins - the Atlantic, Indian and Pacific.
They found the greatest warming has occurred in the upper 300 meters (975 feet) of the ocean waters. This level has warmed an average of 0.56 degrees Fahrenheit.
The water in the upper 3,000 meters (9,750 feet) of the world's oceans has warmed on average by 0.11 degrees Fahrenheit.
These findings represent the first time scientists have quantified temperature changes in all of the world's oceans from the surface to a depth of 3,000 meters.
"Since the 1970s, temperatures at the earth's surface have warmed, Arctic sea ice has decreased in thickness, and now we know that the average temperature of the world's oceans has increased during this same time period," said NOAA Administrator D. James Baker.
Sea ice has been shrinking over the past 40 years, perhaps due in part to warmer ocean waters (Three photos courtesy National Aeronautic and Space Administration)
The ocean and atmosphere interact in complex ways to produce Earth's climate. Owing to its large mass, the ocean acts as the memory of the earth's climate system and can store heat for decades or longer.
As a result, it might become possible some day for scientists to use ocean temperature measurements to forecast the earth's climate decades in advance, the researchers said.
"It is possible that ocean heat content may be an early indicator of the warming of surface, air and sea surface temperatures more than a decade in advance," said Sydney Levitus, who heads NOAA's Ocean Climate Laboratory.
"For example, we found that the increase in subsurface ocean temperatures preceded the observed warming of surface air and sea surface temperatures, which began in the 1970s," Levitus said.
"Our results support climate modeling predictions that show increasing atmospheric greenhouse gases will have a relatively large warming influence on the earth's atmosphere," Levitus warned.
"One criticism of the models is that they predict more warming of the atmosphere than has been actually observed. Climate modelers have suggested that this missing warming' was probably to be found in the world ocean. The results of our study lend credence to this scenario," he explained.
The scientists determined their findings by using data - 5.1 million temperature profiles - from sources around the world, to quantify the variability of the heat content (mean temperature) of the world,s oceans from the surface through 3000 meter depth for the period 1948 to 1996.
The researchers looked at temperature changes in the Atlantic, Indian and Pacific oceans.
"In each ocean basin substantial temperature changes are occurring at much deeper depths than we previously thought. This is just one more piece of the puzzle to understanding the variability of the earth's climate system," said Baker.
The Pacific and Atlantic Oceans have been warming since the 1950s, while the Indian Ocean has warmed since the 1960s. The similar warming patterns of the Pacific and Indian Oceans suggest that the same phenomena is causing the changes to occur in both oceans.
The world ocean warming is likely due to a combination of natural variability, such as the Pacific Decadal Oscillation, and human induced effects, the researchers say. The scientists, led by Levitus, report their findings in today,s issue of the journal "Science," in an article titled "Warming of the World Ocean."
The NOAA report was made possible in part by an international ocean data management project headed by Levitus that has added more than two million historical temperature profiles to electronic archives during the past seven years.
A massive iceberg that peeled off the Ross Ice Shelf in Antarctica this week could be a symptom of warming oceans (Photo courtesy NOAA/Space Science and Engineering Center, University of Wisconsin-Madison)
"International cooperation in building the global ocean databases required for understanding the role of the ocean as part of the earth's climate system has been excellent," said Levitus.
Contributions of subsurface ocean temperature data have come from all countries that make oceanographic measurements including the United States, Russia, the United Kingdom, Germany, France, Canada, Australia, and Japan.
Nearly all of the data were gathered by research ships, naval ships, buoys, and merchant ships. Some merchant ships deploy instruments that measure the temperature of the upper ocean as participants in voluntary programs.
Understanding the role of the ocean in climate change and making 10 year climate forecasts will soon be greatly enhanced by observations planned as part of an emerging international Global Ocean Observing System.
Meanwhile, a recently completed study of climate over the past 100 years suggests that interactions between the atmosphere, ocean and sea ice systems may have played a prominent role in the global warming of the early 20th century, NOAA scientists say.
Climate is a result of interactions between many factors, like this "cloud wake" off Guadalupe island, located in the Pacific Ocean off the coast of Baja California
Using climate models run on high performance supercomputers, scientists at NOAA's Geophysical Fluid Dynamics Laboratory in Princeton, New Jersey, conducted six experiments to explore possible causes for the warming in the first half of the century. Their findings were also published in today,s issue of "Science."
They linked warming in the early part of the century with a combination of ingredients, including increasing concentrations of greenhouse gas and sulfate aerosols.
The supercomputers turned up strong evidence that warming in the latter part of the 20th century was due in large part to human generated greenhouse gases.
"The fact that all experiments capture the warming from 1970 on is indicative of a robust response of the climate model to increasing concentrations of greenhouse gases," said Thomas Knutson, a research meteorologist.
© Environment News Service (ENS) 2000. All Rights Reserved.


This Site Served by TheHostPros