Effect of glacial drainage water on the CO2 system and ocean acidification state in an Arctic tidewater-glacier fjord during two contrasting years

Abstract

In order to investigate the effect of glacial water on the CO₂ system in the fjord, we studied the variability of the total alkalinity (A_T), total dissolved inorganic carbon (C_T), dissolved inorganic nutrients, oxygen isotopic ratio (δ¹⁸O), and freshwater fractions from the glacier front to the outer Tempelfjorden on Spitsbergen in winter 2012 (January, March, and April) and 2013 (April) and summer/fall 2013 (September). The two contrasting years clearly showed that the influence of freshwater, mixing, and haline convection affected the chemical and physical characteristics of the fjord. The seasonal variability showed the lowest calcium carbonate saturation state (Ω) and pH values in March 2012 coinciding with the highest freshwater fractions. The highest Ω and pH were found in September 2013, mostly due to CO₂ uptake during primary production. Overall, we found that increased freshwater supply decreased Ω, pH, and A_T. On the other hand, we observed higher A_T relative to salinity in the freshwater end-member in the mild and rainy winter of 2012 (1142 μmol kg⁻¹) compared to A_T in 2013 (526 μmol kg⁻¹). Observations of calcite and dolomite crystals in the glacial ice suggested supply of carbonate-rich glacial drainage water to the fjord. This implies that winters with a large amount of glacial drainage water partly provide a lessening of further ocean acidification, which will also affect the air-sea CO₂ exchange.