Glacial meltwater and primary production are drivers of strong CO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; uptake in fjord and coastal waters adjacent to the Greenland Ice Sheet

Meire, Lorenz; Søgaard, D. H.; Mortensen, John; Meysman, F. J. R.; Soetaert, Karline; Arendt, KE; Juul-Pedersen, Thomas; Blicher, ME; Rysgaard, Søren

doi:10.5194/bg-12-2347-2015

Cited by 98 publications

(180 citation statements)

References 44 publications

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“…8c and d), for example, has nearly constant DIC throughout the year, while TA drops to less than half of the DIC concentration at peak river discharge (Wang et al, 2013). Another exception is cold glacial meltwater (magenta square), which, even at a DIC : TA more than twice as high as our High Carbon scenario, is pCO 2 -undersaturated relative to the atmosphere and continues to take up DIC as it mixes with seawater (Meire et al, 2015). Seasonal biological productivity may also regulate DIC in some temperate rivers, at least near the river mouth, as it does in the Fraser River.…”

Section: Comparison To Other Rivers and Implications For Future Climatementioning

confidence: 75%

“…For example, the relatively high DIC : TA ratio of the present-day glacial DIC and TA endmember (magenta square, Fig. 8c, d) is in equilibrium with the atmosphere at a river temperature of 0 • C (Meire et al, 2015), but if this pure glacier water were to experience a 10 • C increase during its passage to the ocean, then outgassing would decrease river DIC by about 10 % (∼ 9 µmol kg −1 ) if the meltwater remained in atmospheric equilibrium. However, its pH would stay about the same (slight increase) in this scenario.…”

Section: Comparison To Other Rivers and Implications For Future Climatementioning

confidence: 99%

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The sensitivity of estuarine aragonite saturation state and pH to the carbonate chemistry of a freshet-dominated river

2018

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Abstract. Ocean acidification threatens to reduce pH and aragonite saturation state ( A ) in estuaries, potentially damaging their ecosystems. However, the impact of highly variable river total alkalinity (TA) and dissolved inorganic carbon (DIC) on pH and A in these estuaries is unknown. We assess the sensitivity of estuarine surface pH and A to river TA and DIC using a coupled biogeochemical model of the Strait of Georgia on the Canadian Pacific coast and place the results in the context of global rivers. The productive Strait of Georgia estuary has a large, seasonally variable freshwater input from the glacially fed, undammed Fraser River. Analyzing TA observations from this river plume and pH from the river mouth, we find that the Fraser is moderately alkaline (TA 500-1000 µmol kg −1 ) but relatively DICrich. Model results show that estuarine pH and A are sensitive to freshwater DIC and TA, but do not vary in synchrony except at high DIC : TA. The asynchrony occurs because increased freshwater TA is associated with increased DIC, which contributes to an increased estuarine DIC : TA and reduces pH, while the resulting higher carbonate ion concentration causes an increase in estuarine A . When freshwater DIC : TA increases (beyond ∼ 1.1), the shifting chemistry causes a paucity of the carbonate ion that overwhelms the simple dilution/enhancement effect. At this high DIC : TA ratio, estuarine sensitivity to river chemistry increases overall. Furthermore, this increased sensitivity extends to reduced flow regimes that are expected in future. Modulating these negative impacts is the seasonal productivity in the estuary which draws down DIC and reduces the sensitivity of estuarine pH to increasing DIC during the summer season.

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Section: Comparison To Other Rivers and Implications For Future Climatementioning

confidence: 75%

Section: Comparison To Other Rivers and Implications For Future Climatementioning

confidence: 99%

The sensitivity of estuarine aragonite saturation state and pH to the carbonate chemistry of a freshet-dominated river

2018

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“…With increasing surface air temperatures over the Arctic, recent increases in annual mass loss from the Greenland Ice Sheet (van Angelen et al, 2013;Vizcaíno et al, 2014) are expected to continue. Fjords in Greenland are important both as carbon sinks (Rysgaard et al, 2012;Sejr et al, 2014;Meire et al, 2015) and as distinct components of the coastal ecosystem (Tang et al, 2011;Arendt et al, 2013;Dziallas et al, 2013). Seasonal discharge from the Greenland Ice Sheet creates strong lateral and vertical gradients in the physical properties of water along these fjords (Rysgaard et al, 2003;Mortensen et al, 2013).…”

Section: Introductionmentioning

confidence: 99%

Seasonal Changes in Fe along a Glaciated Greenlandic Fjord

et al. 2016

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Greenland's ice sheet is the second largest on Earth, and is under threat from a warming Arctic climate. An increase in freshwater discharge from Greenland has the potential to strongly influence the composition of adjacent water masses with the largest impact on marine ecosystems likely to be found within the glaciated fjords. Here we demonstrate that physical and chemical estuarine processes within a large Greenlandic fjord are critical factors in determining the fate of meltwater derived nutrients and particles, especially for non-conservative elements such as Fe. Concentrations of Fe and macronutrients in surface waters along Godthåbsfjord, a southwest Greenlandic fjord with freshwater input from six glaciers, changed markedly between the onset and peak of the meltwater season due to the development of a thin (<10 m), outflowing, low-salinity surface layer. Dissolved (<0.2 µm) Fe concentrations in meltwater entering Godthåbsfjord (200 nM), in freshly melted glacial ice (mean 38 nM) and in surface waters close to a land terminating glacial system (80 nM) all indicated high Fe inputs into the fjord in summer. Total dissolvable (unfiltered at pH <2.0) Fe was similarly high with concentrations always in excess of 100 nM throughout the fjord and reaching up to 5.0 µM close to glacial outflows in summer. Yet, despite the large seasonal freshwater influx into the fjord, Fe concentrations near the fjord mouth in the out-flowing surface layer were similar in summer to those measured before the meltwater season. Furthermore, turbidity profiles indicated that sub-glacial particulate Fe inputs may not actually mix into the outflowing surface layer of this fjord. Emphasis has previously been placed on the possibility of increased Fe export from Greenland as meltwater fluxes increase. Here we suggest that in-fjord processes may be effective at removing Fe from surface waters before it can be exported to coastal seas.

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“…While the remineralization of highly labile DOC between station occupations could have added DIC back into mixed layer and decreased the signal of seasonal drawdown, any significant contribution of DIC from remineralization in the mixed layer seems unlikely given the slow remineralization rates and the short time periods (∼ 30 days) between station occupations. Additionally, while glacial freshwater input has been shown to have some impact on NCP estimates in Greenland fjords, Meire et al (2015) found biological processes to be the main driver of carbon dynamics. In a study similar to ours in Glacier Bay, Alaska, Meire and his team estimated air-sea CO 2 fluxes and NCP in the Godthåbsfjord system in western Greenland, as well as the impact of freshwater on these estimates.…”

Section: Caveatsmentioning

confidence: 97%

“…In a study similar to ours in Glacier Bay, Alaska, Meire and his team estimated air-sea CO 2 fluxes and NCP in the Godthåbsfjord system in western Greenland, as well as the impact of freshwater on these estimates. They identified biological processes as the most important driver of carbon dynamics, accounting for 65 to 70 % of the total CO 2 uptake by the fjord system (Meire et al, 2015).…”

Section: Caveatsmentioning

confidence: 99%

Assessing net community production in a glaciated Alaskan fjord

Reisdorph

Mathis

2015

Biogeosciences

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Abstract. The impact of deglaciation in Glacier Bay has been observed to seasonally influence the biogeochemistry of this marine system. The influence from surrounding glaciers, particularly tidewater glaciers, has the potential to affect the efficiency and structure of the marine food web within Glacier Bay. To assess the magnitude and the spatial and temporal variability in net community production in a glaciated fjord, we measured dissolved inorganic carbon, inorganic macronutrients, dissolved oxygen, and particulate organic carbon between July 2011 and July 2012 in Glacier Bay, Alaska. High net community production rates were observed across the bay (~ 54 to ~ 81 mmol C m−2 d−1) between the summer and fall of 2011. However, between the fall and winter, as well as between the winter and spring of 2012, air–sea fluxes of carbon dioxide and organic matter respiration made net community production rates negative across most of the bay as inorganic carbon and macronutrient concentrations returned to pre-bloom levels. The highest organic carbon production occurred within the west arm between the summer and fall of 2011 with ~ 4.5 × 105 kg C d−1. Bay-wide, there was carbon production of ~ 9.2 × 105 g C d−1 between the summer and fall. Respiration and air–sea gas exchange were the dominant drivers of carbon chemistry between the fall and winter of 2012. The substantial spatial and temporal variability in our net community production estimates may reflect glacial influences within the bay, as meltwater is depleted in macronutrients relative to marine waters entering from the Gulf of Alaska in the middle and lower parts of the bay. Further glacial retreat will likely lead to additional modifications in the carbon biogeochemistry of Glacier Bay, with unknown consequences for the local marine food web, which includes many species of marine mammals.

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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

Cited by 98 publications

References 44 publications

The sensitivity of estuarine aragonite saturation state and pH to the carbonate chemistry of a freshet-dominated river

The sensitivity of estuarine aragonite saturation state and pH to the carbonate chemistry of a freshet-dominated river

Seasonal Changes in Fe along a Glaciated Greenlandic Fjord

Assessing net community production in a glaciated Alaskan fjord

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