The Arctic's increased vulnerability to climate change is not limited to higher temperatures and melting permafrost.

New research from the University of Alaska Fairbanks suggests Arctic oceans are particularly susceptible to acidification, with potentially dire consequences to Alaska's rich crab and salmon fisheries.

"Everything is acting in unison on the environment - it's not just the ice loss or the warming or the acidification," said UAF chemical oceanographer Jeremy Mathis. "The Arctic is taking a multilateral hit."

Mathis' newest data from the Gulf of Alaska shows acidity levels far higher than expected are already having an impact. In several sites the increasing acidity has changed ocean chemistry so significantly that organisms are unable to pull crucial minerals out of the water to build shells, he said.

Ocean acidification, often called the sister problem to climate change, refers to the rising acidity of the world's seas as seawater absorbs carbon dioxide from the atmosphere.

By some accounts the oceans have absorbed 30 percent of the carbon dioxide humans have pumped into the atmosphere since the dawn of the industrial age, buffering the atmosphere from the harm posed by that greenhouse gas.

But that storage comes with a price. The ocean's pH has dropped nearly 30 percent* over the past 250 years to levels not seen in the last 800,000 years; if emissions continue unchecked, the oceans could be more acidic than anything experienced in the past 12 million years. Scientists increasingly consider this change in ocean chemistry to be as consequential and potentially catastrophic for the globe as any temperature rise associated with climate disruption.

"When people talk about ocean acidification, it's a whole suite of changes in the chemical system," said Joanie Kleypas, an oceanographer with the National Center for Atmospheric Research in Boulder, Colo. "There's all sorts of stuff going on, and it's hard to piece it all together."

But one of the most noticeable impacts is hampered shell formation: As ocean pH drops (and acidity rises), organisms such as corals, oysters, clams and crabs have trouble pulling minerals necessary for their shells out of the seawater.

It's too soon to say whether an acidifying Arctic means curtains for Alaska's lucrative king crab fishery, Mathis said.

The impact is already being felt by a tiny creature at the base of the food web supporting the state's legendary salmon runs - the pteropod, or swimming sea snail. Accounting for up to half the diet of pink salmon, pteropods have trouble building shells - and hence surviving - at the Gulf of Alaska's current acidity, Mathis has found.

Mathis, talking with commercial salmon fishermen in Alaska's Kenai Peninsula, said many have reported that fish this year weighed 20 percent less than those from past runs. The change could be significant for all Americans: Alaska in 2007 accounted 62 percent of the United States' commercial seafood catch, according to the Marine Conservation Alliance.

"The increasing acidification of Alaska waters could have a destructive effect on all of our commercial fisheries," Mathis said. "This is a problem that we have to think about in terms of the next decade instead of the next century."

But others are more cautious about stating that Arctic ecosystems are any more at risk by acidification than tropical ones.

Cold water holds more gas than warmer water - the reason why a refrigerated can of cola fizzes less aggressively when opened than a warm one. While this means frigid waters off Alaska's coasts can absorb more carbon dioxide from burning fossil fuels, it also means the waters were naturally more acidic and that species in those waters are adapted to lower pH levels.

"It won't necessarily have a more severe impact," said Oceana marine scientist Ellycia Harrould-Kolieb. "It's having an earlier impact."

"As more and more carbon dioxide is absorbed by the oceans, it's going to spread from the poles to the tropics."

There's also question whether Arctic organisms are more vulnerable than their tropical counterparts, Kleypas said.

Northern critters might be able to adapt more successfully to changing ocean chemistry than tropical coral reefs, which Kleypas compared to "spoiled brats" that have existed for eons in comfortably stable, higher pH waters.

Indeed, the situation in the Arctic could be akin to adding a few degrees to the summertime highs in Phoenix, she said: the typical resident, well-adapted to the heat, wouldn't have to do much to adjust.

But force that same increase upon someone living in Hawaii, where temperatures stay comfortably constant, and the change is unbearable.

"If they're already used to (stress), they've figured out a way to deal with it," she said.

"Not that people are wrong," she added. But "we're assuming things we shouldn't assume yet."

Still, both Kleypas and Harrould-Kolieb cautioned that acidification's consequences are profound and need to be taken seriously, whether in the tropics or at the poles.

Mathis, who agreed that the full range of acidification's effects remains uncertain, said it's clear at this point that the changing oceans pose a threat to Alaska's commercial fisheries and subsistence communities today.

"Ecosystems in Alaska are going to take a hit from ocean acidification," said Mathis.

"Right now, we don't know how they are going to respond."

This article originally appeared at The Daily Climate, the climate change news source published by Environmental Health Sciences, a nonprofit media company.

* *Note (8/28/09): Scientists estimate that seawater's average pH is 8.1 today versus 8.2 in preindustrial times. Given the logarithmic pH scale, that represents a 30 percent increase in acidity.