Marine CO2 system variability in a high arctic tidewater-glacier fjord system, Tempelfjorden, Svalbard

Abstract

The marine CO2 system in Tempelfjorden (Svalbard) was investigated between August 2015 and December 2017 using total alkalinity, pH, temperature, salinity, oxygen isotopic ratio, and nutrient data.Primary production resulted in the largest changes that were observed in the partial pressure of CO2 (pCO2, 140 µatm) and the saturation state of aragonite (ΩAr, 0.9). Over the period of peak freshwater discharge (June to August), the freshwater addition and air-sea CO2 uptake (on average 15.5 mmol m -2 day -1 in 2017) governed the surface pCO2. About one fourth of the uptake was driven by the freshening.The sensitivity of ΩAr to the freshwater addition was investigated using robust regressions. If the effect of air-sea CO2 exchange was removed from ΩAr, a freshwater fraction larger than 50% (lower range of uncertainty) was needed to provide aragonite undersaturated waters. This study shows that ΩAr and freshwater fraction relationships that are derived from regression techniques and the interpretation thereof are sensitive to the effect of air-sea CO2 exchange. Since the freshening in itself only drives a fraction of the air-sea CO2 uptake, studies that do not account for this exchange will overestimate the impact of freshwater on ΩAr. Finally, in the summer an excess in the salinity normalized dissolved inorganic carbon, corrected for aerobic primary production/respiration, of on average 86 µmol kg -1 was found in the deepest water of the fjord. This excess is suggested to be a result of enhanced CO2 uptake and brine release during the period of sea ice growth. Dates CTD Stations Bottom depths (m) Max sampling depths (m) TA/pH δ 18 O Nutrients

Review article: How does glacier discharge affect marine biogeochemistry and primary production in the Arctic?

“…Seasonal changes in the availability of bioessential resources, the structure of the water column and the feeding patterns of zooplankton thereby interact to produce distinct bloom periods of high primary production shouldered by periods of low primary production. In glacier fjords, strong lateral and vertical gradients in some, or all, of these factors create a far more dynamic situation for primary producers than in the open ocean (Etherington and Hooge, 2007;Arendt et al, 2010;Murray et al, 2015).…”

“…5). For the purposes of defining the spatial extent of individual glacier fjords, we consider broad bay areas such as the lower and central parts of Glacier Bay (Etherington and Hooge, 2007;Reisdorph and Mathis, 2015), Scoresby Sund (Scoresby Sound in English; Seifert et al, 2019) and Disko Bay (Jensen et al, 1999;Nielsen, 1999) to be beyond the scale of the associated glacier fjords on the basis of the oceanographic interpretation presented in the respective studies. Defining the potential spatial influence of marineterminating glaciers is more challenging.…”

Review Article: How does glacier discharge affect marine biogeochemistry and primary production in the Arctic?

“…By decreasing the alkalinity of glacially-modified waters, glacier discharge reduces the aragonite and calcite (ΩAr and ΩCa, respectively) saturation states thereby amplifying the effect of ocean acidification (Fransson et al, 2015(Fransson et al, , 2016Ericson et al, 2019). High primary production can mitigate this impact as photosynthetic CO 2 uptake reduces dissolved inorganic carbon and pCO 2 (e.g.…”

“…In relatively productive fjords, the negative effect of alkalinity dilution may therefore be counter-balanced. However, in systems where discharge-driven stratification is responsible for low productivity, the increased input of discharge may create a positive feedback on ocean acidification state in the coastal zone resulting in a lower saturation state of calcium carbonate (Chierici and Fransson, 2009;Ericson et al, 2019). Low-calcium carbonate saturation states (Ω<1; i.e.…”

“…conditions have negative effects on aragonite-shell forming calcifiers such as the pteropod Limacina helicina (Comeau et al, 2009(Comeau et al, , 2010Lischka et al, 2011;Lischka and Riebesell, 2012;Bednaršek et al, 2014). Under future climate scenarios, in addition to the effect of increased glacier drainage in glacier fjords, synergistic effects with a combination of increased ocean CO 2 uptake and warming will further amplify changes to the ocean acidification state (Fransson et al, 2016;Ericson et al, 2019), resulting in increasingly https://doi.org/10.5194/tc-2019-136 Preprint. Discussion started: 18 June 2019 c Author(s) 2019.…”