Scientists find yet another negative impact of glacial melt: ocean acidification

Posted by on Jul 28, 2014

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One of the College Fjord glaciers as it flows into Alaska’s Prince William Sound. Ocean acidification from the meltwater is yet other negative impact of rising temperatures. (Wikimedia Commons)

Researchers have recently uncovered previously unknown negative environmental impact of accelerated glacial melt. If reductions in freshwater availability, landslides, outburst floods and sea level rise were not bad enough, ocean acidification can be added to the list.

Ocean acidification is a well-known process, though it has not previously been linked to glaciers. Scientists have recognixed that the chemistry of the world’s oceans has been changing as they absorb carbon dioxide from the atmosphere. About one-third of the carbon dioxide that humans release each year dissolves in the oceans, making them more acid, much as dissolving carbon dioxide in tapwater makes seltzer, its characteristic tartness due to its acidity. This acidification reduces the concentration of carbonate ions that are essential to the formation of the mineral shells of marine organisms, whether large molluscs, corals, or microscopic plants such as plankton. If the saturation level of these ions in seawater falls too low, the shells begin to dissolve.

Jeremy Mathis and Wiley Evans, experts in chemical oceanography at the University of Alaska Fairbanks Ocean Acidification Research Center, recently published a paper that examines the chemistry of fresh-water plumes from glaciers that directly discharge into Prince William Sound in Alaska. The glacial meltwater accumulates in the sound during the summer, when melting is most pronounced. That freshwater eventually ends up in the Gulf of Alaska, when the tides pick up at the end of the summer. “We are seeing that the glacial plume inside and moving out into the Gulf of Alaska is far more extensive than we thought it was going to be,” said Mathis, “one of our conclusions is that the glaciers are having quite an extensive impact on the water chemistry of Prince William Sound.” They found reduced concentrations of carbonate ions more than 10 miles offshore, as well as other chemical changes that can harm shells.

Tidewater glaciation is found both above and below the water's surface. (via the National Park Service, http://www.nps.gov/glba/naturescience/glaciers.htm)

Tidewater glaciation is found both above and below the water’s surface. (via the National Park Service, http://www.nps.gov/glba/naturescience/glaciers.htm)

Building on this research, they are leading a project that will send three remotely controlled vessels into Prince William Sound to collect more data on the water chemistry. In this round of study, the additional data will help identify the processes that are occurring due to glacial run-off, and help pinpoint which species are most vulnerable in the Sound. They are also exploring the interactions between the glacier meltwater and the waters of the open seas; these may combine to exacerbate the ocean acidification.

As Jeremy Mathis, a lead oceanographer in the study explains, “if the saturation state becomes too low, the waters can become corrosive to shell building organisms.” This has dire implications not only for the organisms themselves, but for the foodwebs within marine ecosystems—and for the humans who depend on healthy ecosystems for fishing.

The project, funded partly by the National Oceanic and Atmospheric Administration, is exploring glacially-fed Alaskan waters this summer. It includes two yellow surfboard-like Carbon wave gliders that move across the surface of the water. The Slocum Glider is a yellow torpedo-like sensor that dives underwater to depths of 600 feet capturing profiles of the ocean. The researchers consider this technology a “revolution,” making study the oceans far less expensive and data more available and extensive. In addition, the team will work with tour companies and launch with instruments from those ships. This strategy not only is cost-effective, but also gives the researchers the opportunity to share with the public the environmental issues they are studying.

There is a lot at stake in the Prince William Sound and outlying Gulf of Alaska. While their work is valuable in understanding how glacier loss will affect aquatic ecosystems around the world, the loss of marine organisms is a big threat for their region. Ultimately, the project aims to understand the dynamics of the sound and Gulf of Alaska, not only for the sake of science, but also so that the fishing community, armed with fuller information, can begin exploring ways to adapt to their changing environment.

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