High-frequency pH time series reveals pronounced seasonality in Arctic coastal waters

The accelerated rate of climate change in the Arctic Ocean occurs in conjunction with a system known for its extreme seasonal variability. Here, we present 2 years of continuous pH, salinity, and temperature data from the north Arctic coast of Alaska from instruments deployed in a kelp bed at 4.5-6 m depths in Stefansson Sound. At the innermost site, which receives freshwater runoff from the nearby Sagavanirktok River, short-term pH variability in late spring and summer produced pH values up to 8.67. The pH values of the deeper offshore site were less affected by freshwater input, although biological (heterotrophy) and physiochemical (ice formation) processes dominated during the winter months, driving pH down to 7.47 during the 8-month period of ice cover. These long-term physicochemical measurements reveal the natural but critical influence of changing river inputs on the pH of Arctic nearshore waters which support highly productive communities and subsistence fisheries.