High-frequency multiyear time-series highlights seasonal and annual pH variability along a freshwater gradient in Alaska’s Beaufort Sea

The Arctic Ocean is currently undergoing unprecedented change. While carbonate system parameters have been collected across the Arctic Ocean for decades, nearshore, high-frequency, multiyear time-series that include both seasonal sea ice evolution and decline remain elusive due to the extreme logistical constraints that accompany working in remote polar regions. Furthermore, baseline data of environmental factors are critical for understanding annual and long-term climate variability affecting these regions. Here, we present two years of high-frequency, continuous pH, salinity and temperature data from two sites within Stefansson Sound that vary in distance from the Sagavanirktok River along Alaska’s Beaufort Sea, from August 2016 – August 2018. Coastal ocean pH, salinity, and temperature generally followed seasonally distinct transitions that were related to four main events: the summer open water, fall freeze-up, the winter ice covered season, and the spring freshet. Of all forcing factors, the greatest influence on pH was determined largely by proximity to the Sagavanirktok River, as freshwater from this riverine system is well buffered, drastically increasing pH during height of the spring run-off. Although seasonal trends were present, the timing of these transitions varied annually, and the relative impact of these transition states were non-linear as pH amplitude during these seasons varied from one year to the next. These data underscore the importance of collecting multiyear carbonate system time-series in dynamic nearshore environments, where the identification of intra-and intersite seasonal and annual differences would be otherwise undetectable.