Rising acidity in oceans and accelerating wind patterns may lead to unexpected changes.
Melanie Stetson Freeman/Staff/File
Global warming of the sea is affecting the atmosphere and ocean in subtle ways, adding a new dimension to the concept of global change.
As carbon dioxide accumulates in the air, more of it dissolves into the sea. This gradually increases sea-water acidity. Biologists have been concerned about what this could do to corals and other animals that have adapted to live in fairly constant marine conditions. Now scientists also have to take account of changes to seawater chemistry.
Keith Hester and colleagues, who are exploring ocean acidity at the Monterey Bay Aquarium Research Institute (MBARI) in Moss Landing, Calif., explained this new perspective earlier this month in Geophysical Research Letters.
"The waters of the upper ocean are now undergoing an extraordinary transition in their fundamental chemical state at a rate not seen on Earth for millions of years, and the effects are being felt not only in biological impacts but also on basic geophysical properties, including acoustics," they note.
Seawater chemistry affects how water absorbs sound. It's a poorly understood process in which a variety of chemical interactions determines how molecules absorb sound at specific frequencies. Increasing seawater acidity favors transmission of low- to mid-frequency sound. Marine mammals rely on sound in this range to communicate and to find food and mates.
According to the MBARI announcement, its research team estimates "that sound already may travel 10 percent farther in the oceans than it did a few hundred years ago." The team projects that by midcentury, sound may travel as much as 70 percent farther than it does today.