Global Warming Impacting Our Oceans

Ocean Chemists Find Carbon Dioxide Emissions Make Oceans Noisier

June 1, 2009

Ocean chemists discovered that the high levels of carbon dioxide being released into the atmosphere is being absorbed into the ocean and reacting with water molecules, making the ocean more acidic. The more acidic ocean water becomes, the farther underwater sounds will travel. This is because as sound moves through the water, it vibrates groups of atoms causing the water to absorb sounds at certain frequencies. The overall effect is that the more acidic water cannot absorb as many low- and mid-frequency sounds. This effect would allow sea life to communicate with one another from greater distances and hear approaching vessels from farther away.

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WHAT IS GLOBAL WARMING DOING TO THE OCEANS? It's raising the oceans' temperatures ever so slowly, but also, it's making it easier for them to absorb Carbon Dioxide (CO2). Large amounts of CO2 are absorbed by the ocean, up to a million tons an hour worldwide. This changes the chemistry of the ocean, making it slightly more acidic. This can harm the environment as far as many marine animals and plants are concerned, causing devastation in ecosystems like coral reefs. However, because more acidic seawater absorbs less low- and mid-frequency sound (the frequencies at which many animals communicate), water becomes better able to transmit certain frequencies, meaning that equally loud noises can be heard farther away in water with lower pH levels.

ABOUT GLOBAL WARMING: Global warming refers to an average increase in the earth's temperature, which has risen about 1 degree Fahrenheit over the past 100 years, and to changes in climate. A warmer earth may lead to changes in rainfall patterns, and a rise in sea level, for example, as the polar glaciers melt. Some of this rise is due to the greenhouse effect: certain gases in the atmosphere trap energy from the sun so that heat can't escape back into space. Without the greenhouse effect, the earth would be too cold for humans to survive, but if it becomes too strong, the earth could become much warmer, causing problems for humans, plants and animals.

The American Geophysical Union and the Acoustical Society of America contributed to the information contained in the TV portion of this report. This report has also been produced thanks to a generous grant from the Camille and Henry Dreyfus Foundation, Inc.

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To Go Inside This Science:
Lisa Borok
Communications Associate
Monterey Bay Aquarium Research Institute (MBARI)
Moss Landing, CA 95039-9644
831.775.1807
lisab@mbari.org

Peter Weiss
American Geophysical Union
Washington, DC 20009-1277
pweiss@agu.org
1-800-966-2481

Acoustical Society of America
Melville, NY 11747-4502
516-576-2360
asa@aip.org