Seasonal Cycles of Air-Sea CO2 Exchange in an Arctic Coastal System

In recent years, substantial progress has been made towards understanding the Arctic marine environment's role as a source or sink for atmospheric CO₂. Through ship-based field programs, the international community has found that the majority of Arctic seas absorb CO₂ from the atmosphere, typically at rates higher than average for the rest of the global ocean. However, most of those field measurements have been confined to the open water season. Some measurements are available near the end of ice break-up, or towards the beginning of freeze-up, but systematic observations of the complete annual cycle are rare. This observation gap limits our ability to understand the biogeochemical processes that drive spatial and temporal variability in CO₂ exchange, and makes it difficult to predict how the Arctic's status as a marine sink for CO₂ might be affected by climate change.

To address this gap, our research team has established an observation program near Cambridge Bay, Nunavut. We have deployed underwater instruments to measure dissolved CO₂ (pCO₂) and pH in an effort to identify and quantify the biogeochemical processes that drive the marine carbonate system throughout the annual cycle. Those measurements are complemented by a novel micrometeorological installation that allows us to make direct measurements of CO₂ exchange. In the summer, an underway measurement system installed on a coastal research vessel allows us to observe spatial variability in the open water months. Most importantly, we have established a community-based field-sampling program that allows us to collect samples and maintain instruments in even the most extreme seasons.

In this presentation, I will present highlights of these efforts. The dynamic biogeochemical processes that occur thorough the year - even in the dark of polar night - will be described. I will also show that CO₂ exchange in the "shoulder seasons" (early spring, late fall) is more important than previously realized. These findings will highlight the importance of year-round observations in understanding air-sea CO₂ exchange in the Arctic.