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

Abstract

Abstract. The Greenland Ice Sheet releases large amounts of freshwater, which strongly influences the physical and chemical properties of the adjacent fjord systems and continental shelves. Glacial meltwater input is predicted to increase strongly in the future, but the impact of meltwater on the carbonate dynamics of these productive coastal systems remains largely unquantified. Here we present seasonal observations of the carbonate system in the surface waters of a west Greenland tidewater outlet glacier fjord. Our data reveal a permanent undersaturation of CO2 in the surface layer of the entire fjord and adjacent shelf. The average annual CO2 uptake for the fjord is estimated to 65 g C m−2 yr−1 indicating that the fjord system is a strong sink for CO2. Primary production and the high input of glacial meltwater strongly affect the carbonate system in the Godthåbsfjord system. The largest CO2 uptake occurs near to the ice sheet. High glacial meltwater input during the summer months correlates strongly with high levels of CO2 undersaturation, which can be explained by the non-linear effect of salinity on surface water pCO2 resulting from the mixing of glacial meltwater and ambient fjord water. Our findings hence imply that glacial meltwater may form a major driver for CO2 undersaturation in fjord and coastal waters adjacent to an Ice Sheet.

Long photoperiods sustain high pH in Arctic kelp forests

“…For a given photoperiod, the rate of CO 2 depletion also increased with increasing CO 2 supply (Fig. 3B), from 200 ppm, characteristic of contemporary Arctic conditions during spring and summer ( 25 , 27 , 28 ) and exceeding the minimum levels observed in situ within the Arctic kelp canopy (Fig. 1), to 400 and 1000 ppm, reflecting a CO 2 -enriched situation possibly met in the future.…”

“…40 m ( 37 ) interspaced with communities of benthic microalgae and with scarce occurrence of eelgrass meadows at 1 to 3 m depth ( 38 ) and rich intertidal communities ( 21 ). More details on Kobbefjord are available ( 26 , 28 ), including data acquired in parallel to those reported here in neighboring kelp sites ( 21 ). Fortuna Bay is a shallow (ca.…”

“…CO 2 levels in coastal Arctic ecosystems are particularly low [<200 parts per million (ppm)] during the light period, largely driven by intense drawdown by the spring phytoplankton bloom ( 25 – 28 ), and macrophyte photosynthesis would further reduce the levels. Hence, future increases in CO 2 may lead to a positive feedback, promoting Arctic photosynthesis and further enhancing the capacity of macrophytes to up-regulate pH.…”

Coastal marine uptake of CO2 around Greenland

“…Recent studies (Sejr et al, 2011;Rysgaard et al, 2012and Meire et al, 2014 have shown that the fjords and shelf areas of Greenland have an exceptional high potential for CO2 uptake. Measurements of pCO2 were carried out in July-August from 2006-2009 in the High Arctic fjord, Young Sound by Sejr et al, (2011).…”

“…Another possible pump mechanism driving uptake of CO2 in the costal sea around Greenland is the inflow of melt water from land and the Greenland ice sheet. Because of the nonconservative behaviour of CO2 in water, the mixing of meltwater and sea water will result in strongly under saturated surface water with respect to CO2 (Meire et al, 2014).…”