- Associated Press - Saturday, November 22, 2014

ANCHORAGE, Alaska (AP) - The world’s most acidic ocean waters are found during the cold winter months in the Bering Sea, according to a new study.

Researchers at Columbia University released a series of maps tracking changes in global marine activity, The Alaska Dispatch News reported (https://goo.gl/OkLfSa).

The new maps, based on 40 years’ worth of measurements, show how acidity in marine waters around the globe changes with the seasons.

The Bering Sea has shallow waters, a broad continental shelf and ocean currents that deposit nutrients from around the world. Those conditions make for wonderful fisheries, geochemist Taro Takahashi said.

But the sea also receives large amounts of runoff from rivers, which dump carbon-rich sediments and fresh water. And it’s partially enclosed by land, so acidic waters are more likely to become trapped. Together, the conditions make the Bering Sea ideal for acidity, especially in the winter months when low temperatures allow water to hold maximum carbon dioxide, Takahashi said.

The Bering Sea has registered pH readings of about 7.7, according to data collected by Takahashi and scientists from the National Oceanic and Atmospheric Administration (NOAA) and other institutions. The maps show that spots in the Gulf of Alaska register similarly acidic readings. Those levels compare to a global average of 8.1 on the logarithmic pH scale, which runs from the most acidic measurement of zero to the most alkaline measurement of 14.

Summer blooms of plankton absorb large amounts of carbon dioxide from the water, dramatically raising pH levels temporarily every year. Then swelling up of carbon-rich water from the ocean depths in winter help lower pH levels in that season, scientists say.

The Antarctic waters also are vulnerable to acidification, but they are less acidic than the Bering Sea, which gets runoff waters and is almost enclosed where Alaska and Russia nearly touch.

Tropical and temperate oceans have pH levels that range from 8.15 to 8.05, scientists said.

The good news for the Bering Sea is that acidification appears to be increasing less quickly there than in the rest of the world’s ocean waters.

“The Bering Sea is very acidic and the most acidic water in the global ocean, but it’s not changing fast,” Takahashi said.

But acidification is happening faster than predicted in Arctic waters north of the Bering Sea, scientists said.

The ocean changes put fishing-dependent regions in Alaska at particular risk, according to a recent NOAA study.

___

Information from: Alaska Dispatch News, https://www.adn.com


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