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The Rapidly-Acidifying Arctic Ocean Won't Return to Normal for Thousands of Years

While the picture isn't yet complete, it's not looking good.
Photo: Tim Lucas/Flickr

So much of the focus on climate change-induced ocean acidification has been on its effects in tropical regions, and sometimes on the effects on shellfish (more acidic waters are hell on shell formation). But a new study looks at the effects of acidification on the Arctic, and while the picture isn't yet complete, it's not looking good.

What we do know, as summed up by the Arctic Monitoring and Assessment Programme (AMAP): The Arctic Ocean is acidifying rapidly, with pH decreasing about 0.02 per decade over the past half century. This is inline with previous research showing that the world's oceans are acidifying more rapidly than at any other time in the past 300 million years. Human activity is the primary culprit, with all the greenhouse gas emissions absorbed by the oceans since the Industrial Revolution meaning the average acidity of the water at the ocean surface has risen by 30 percent.

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Interestingly, Arctic waters are particularly vulnerable to acidification, due to a few factors. First, large quantities of fresh water, from rivers and ice melt, mix into the Arctic Ocean, meaning the water is less capable of handling the acidifying effect of CO2. Also, CO2 has a higher solubility in cold Arctic waters than in tropical ones, meaning Arctic waters can hold more acidifying carbon. Finally, the decreasing amount of summer sea ice each year means there's more open water to absorb CO2.

The report also points out that the food chain in Arctic marine ecosystems is often shorter and simpler than elsewhere, which means disruption of a few key species at the bottom of the food chain can have an even greater impact. Animal species such as sea butterflies, sea urchins, and sea stars are all likely to be affected; research carried out in the Antarctic shows that animals such as these have difficulty maintaining their shells in more acidic water.

Though birds and mammals probably won't be directly affected by more acidic water, they are certainly indirectly affected "if their food sources decline, expand, relocate, or otherwise change in response to ocean acidification," as the AMAP report notes.

The one form of life cited as potentially benefiting from more acidic waters? Some seagrasses. But balanced against the negative impacts on animals at the bottom of the food chain, a seagrass bloom may not be beneficial.

While the AMAP report is clear in saying that ocean acidification will likely have a negative impact on Arctic fisheries—affecting the base of the food chain can have cascade effects that ripple to the top—it's not yet clear how it will all play out. The refrain of the report is that we need more research in the Arctic. It's a common ending to any scientific paper, but here it's stated with urgency. We can't say for certain how things may hang together or fall apart, but with how much is at stake, leaving it to chance is not an intelligent course of action.

One thing is certain, though. The changes brought about by ever-increasing carbon emissions—remember that we're going to officially pass 400 ppm of CO2 in the atmosphere pretty soon—are very long lasting. As the chairman of the AMAP report, Richard Bellerby, told the BBC, "Even if we stop emissions now, acidification will last tens of thousands of years."