The Arctic Ocean marine carbon cycle: evaluation of air-sea CO<sub>2</sub> exchanges, ocean acidification impacts and potential feedbacks

Abstract

Abstract. At present, although seasonal sea-ice cover mitigates atmosphere-ocean gas exchange, the Arctic Ocean takes up carbon dioxide (CO 2 ) on the order of −66 to −199 Tg C year −1 (10 12 g C), contributing 5-14% to the global balance of CO 2 sinks and sources. Because of this, the Arctic Ocean has an important influence on the global carbon cycle, with the marine carbon cycle and atmosphere-ocean CO 2 exchanges sensitive to Arctic Ocean and global climate change feedbacks. In the near-term, further sea-ice loss and increases in phytoplankton growth rates are expected to increase the uptake of CO 2 by Arctic Ocean surface waters, although mitigated somewhat by surface warming in the Arctic. Thus, the capacity of the Arctic Ocean to uptake CO 2 is expected to alter in response to environmental changes driven largely by climate. These changes are likely to continue to modify the physics, biogeochemistry, and ecology of the Arctic Ocean in ways that are not yet fully understood. In surface waters, sea-ice melt, river runoff, cooling and uptake of CO 2 through air-sea gas exchange combine to decrease the calcium carbonate (CaCO 3 ) mineral saturation states ( ) of seawater while seasonal phytoplankton primary production (PP) mitigates this effect. Biological amplification of ocean acidification effects in subsurface waters, due to the remineralization of organic matter, is likely to reduce the ability of many species to produce CaCO 3 shells or tests with profound implications for Arctic marine ecosystems

Glacial meltwater and primary production are drivers of strong CO<sub>2</sub> uptake in fjord and coastal waters adjacent to the Greenland Ice Sheet

“…High biological productivity combined with high seasonality in freshwater input and sea ice cover leads to strong dynamics in the carbonate system (Kaltin and Anderson, 2005). Increasing water temperatures, freshwater input and decreasing ice cover will likely have a profound effect on the carbon cycle of the coastal Arctic Ocean and will likely amplify the large seasonal and spa-tial biogeochemical gradients that occur in this area (Bates and Mathis, 2009;Mathis et al, 2011). While 25 % of the global continental shelves (water depth < 200 m) are located in the Arctic, we still have a limited understanding of the carbon dynamics in these high-latitude coastal systems due to the scarcity of studies compared to low-latitude coastal environments (Bates and Mathis, 2009).…”

“…Increasing water temperatures, freshwater input and decreasing ice cover will likely have a profound effect on the carbon cycle of the coastal Arctic Ocean and will likely amplify the large seasonal and spa-tial biogeochemical gradients that occur in this area (Bates and Mathis, 2009;Mathis et al, 2011). While 25 % of the global continental shelves (water depth < 200 m) are located in the Arctic, we still have a limited understanding of the carbon dynamics in these high-latitude coastal systems due to the scarcity of studies compared to low-latitude coastal environments (Bates and Mathis, 2009). As a result, there are many open questions regarding how the carbon cycle in the Arctic will be affected by future environmental changes.…”

“…The Arctic Ocean plays an important role in the global carbon cycle and contributes 5-14 % to the global ocean CO 2 uptake (Bates and Mathis, 2009). High biological productivity combined with high seasonality in freshwater input and sea ice cover leads to strong dynamics in the carbonate system (Kaltin and Anderson, 2005).…”

Towards the Marine Arctic Component of the Pan-Eurasian Experiment

“…In combination with the co-occurring external forcings, both processes are conducive to a variety of alterations in marine hydrobiological processes. Among the latter are the formation of nutrients uptakable by phytoplankton, rates of intracellular metabolism, primary production, and 20 reshufflings in phytoplankton species composition and abundance (Bates and Mathis, 2009). Figure 7 presents an example of a widespread phytoplankton bloom in the Barents Sea.…”

“…However, these activities are irregular in time, very expensive, biased to the summer season, 25 and hence poorly suited for providing regular long-term monitoring data. Moorings have been deployed at key locations in the gateways and rims of the Arctic Ocean ( Figure 6), but they mainly deliver physical parameters from fixed depths in a delayed mode (Beszczynska-Möller et al, 2011). Nevertheless, NABOS measurements allowed documenting of Atlantic Water warm pulses in 2000s (Polyakov et al, 2011), and revealing strong seasonal cycle in the intermediate AW layer deep below the ocean surface, which was not directly measured before Dmitrenko et al, 2009).…”