Climatic and Tidal Forcing of Hydrography and Chlorophyll Concentrations in the Columbia River Estuary

Roegner, G. Curtis; Seaton, Charles; Baptista, Antoniò M.

doi:10.1007/s12237-010-9340-z

Cited by 33 publications

(64 citation statements)

References 53 publications

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“…The Fraser River, the primary freshwater source, drains approximately 238 000 km 2 with seasonally variable discharge (∼ 800 to 12 000 m 3 s −1 at Hope, ECCC data, http://wateroffice.ec.gc.ca) due to summer snow/ice melt and lack of dams throughout most of the watershed. This large freshwater flux is partially contained by narrow passages and tidal mixing over sills (Pawlowicz et al, 2007), and thus imparts a significant freshwater influence on the strait, especially compared with regions where large rivers meet the ocean directly, such as the nearby Columbia River plume region (Roegner et al, 2011). These same coastal and topographic features create long residence times, causing carbon to accumulate and making the strait DIC-rich relative to the open ocean ) despite a strong, seasonal DIC upwelling signal over the outer shelf (Bianucci et al, 2011).…”

Section: Study Areamentioning

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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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: Study Areamentioning

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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“…The Fraser River, the primary freshwater source, drains approximately 238,000 km 2 with seasonally-variable discharge (∼800 to 12,000 m at Hope, ECCC data, http://wateroffice.ec.gc.ca) due to summer snow/ice melt and lack of dams throughout most of the watershed. This large freshwater flux is partially contained by narrow passages and tidal mixing over sills (Pawlowicz et al, 2007), and thus imparts a significant freshwater influence on the Strait especially compared with regions where large rivers meet the ocean directly such as the nearby Columbia River plume region 10 (Roegner et al, 2011). These same coastal and topographic features create long residence times, causing carbon to accumulate and making the Strait DIC-rich relative to the open ocean (Ianson et al, 2016) despite a strong, seasonal DIC upwelling signal over the outer shelf (Bianucci et al, 2011).…”

Section: Study Areamentioning

confidence: 99%

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

Moore-Maley¹,

Ianson²,

Allen³

2017

Preprint

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Abstract.Ocean acidification threatens to reduce pH and aragonite saturation state (Ω A ) in estuaries, potentially damaging their ecosystems. However, the impact of highly variable river total alkalinity (TA) and dissolved inorganic carbon (DIC) on pHand Ω A in these estuaries is unknown. We assess the sensitivity of estuarine surface pH and Ω A to river chemistry using a 1-dimensional, biogeochemical-coupled model of the Strait of Georgia on the Canadian Pacific coast and generalize the results 5 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 and pH observations from this river and its estuary, we find that the Fraser is moderately alkaline (TA 500-1350 µmol kg −1 ) but relatively DIC-rich, especially during winter (low flow). Model results show that estuarine pH and Ω A , while sensitive to freshwater DIC and TA, do not vary in synchrony. Instead, rivers with high DIC and TA produce lower estuarine pH due to an increased estuarine DIC:TA ratio, but higher estuarine Ω A because of 10 DIC contributions to the carbonate ion. This estuarine pH sensitivity decreases with increasing mean river TA, but the zone of maximum pH sensitivity also moves to higher salinity which could impact a larger areal extent of the estuary. Many temperate rivers, such as the Fraser, are expected to experience weaker freshets and stronger winter flows under climate change, reducing the extent of the river plume and the impact of river chemistry in much of the estuary. However, increasing carbon in rivers will move the highest sensitivity zone to higher salinities that cover larger areas under present-day flow regimes.

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“…Also, the horizontal distribution of P is remarkably different under different stratification conditions. A specific example is the Columbia River estuary, where in spring season P during spring tides (weak salinity stratification) significantly decreases along the estuary towards the mouth, whereas during neap tides (strong salinity stratification) high densities extend seawards in the upper layer (Roegner et al 2011).…”

Section: Introductionmentioning

confidence: 99%

“…Cloern (1996) pointed out that in estuarine and coastal systems, a strong tidal stirring effectively mixes phytoplankton downward into the aphotic zone where net growth rate is negative, whereas a vertical stratification can isolate phytoplankton in the euphotic zone such that it allows P to increase. Roegner et al (2011) related the isolation of phytoplankton in the upper low-salinity water during neap tides to the extension of the fluvial conditions to the estuary mouth during strong stratification. Lara-Lara et al (1990) suggested that estuarine salinity variation also directly influences the P pattern, since it has been observed that a large number of freshwater phytoplankton lyse in low salinity (3-5 psu) regions.…”

Section: Introductionmentioning

confidence: 99%

“…Here, also two parameters are introduced that quantify the vertical and along-estuary gradients of P . In "Results" section, results are first shown for weakly and strongly stratified conditions and they are compared to field data of Roegner et al (2011) to demonstrate that the model is capable of capturing main characteristics of the observed P patterns. Next, results of sensitivity experiments that relate to the last three research aims are presented.…”

Section: Introductionmentioning

confidence: 99%

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Quantifying the Effect of Salinity Stratification on Phytoplankton Density Patterns in Estuaries

Liu

Swart

2017

Estuaries and Coasts

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To quantify the effect of salinity stratification on phytoplankton density (denoted as P ) patterns, experiments were conducted with an idealised model that couples physical and biological processes. Results show that the idealised model is capable of capturing the main features of observed P patterns in the Columbia River estuary during the spring season: during weak stratification, P is almost vertically uniform with values decreasing towards the estuary mouth, whereas during strong stratification, high values of P extend further seawards but are confined to the upper layer. Sensitivity studies reveal that the strong vertical gradients of P can only occur if the intensity of turbulence (measured by depth-averaged values of vertical eddy viscosity and eddy diffusivity) is weak. The advection of P by subtidal currents is important in obtaining a smaller along-estuary gradient of P during weak stratification and in obtaining a smaller horizontal gradient and a larger vertical gradient of P during strong stratification. Accounting for stratification controlled vertical distribution of vertical eddy viscosity and eddy diffusivity is necessary for obtaining realistic P patterns if stratification is strong, but not if stratification is weak. A higher osmotic stress, which leads to faster loss of phytoplankton in salt water, results in a larger along-estuary gradient of P if stratification is weak and in a larger vertical gradient of P if stratification is strong.

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Climatic and Tidal Forcing of Hydrography and Chlorophyll Concentrations in the Columbia River Estuary

Cited by 33 publications

References 53 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

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

Quantifying the Effect of Salinity Stratification on Phytoplankton Density Patterns in Estuaries

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