Variability in a fjord-like coastal estuary I: Quantifying the circulation using a formal multi-tracer inverse approach

Riche, Olivier G. J.; Pawlowicz, Rich

doi:10.1016/j.ecss.2013.11.018

Cited by 9 publications

(8 citation statements)

References 29 publications

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“…In order to estimate O 2int , we require a conversion factor relating depth‐integrated values to ferry measurements:

O_{2 int} = \int_{0}^{50 normalm} O_{2} false(z false) normald z = \int_{0}^{50 normalm} false(normalΔ O_{2} false(z false) + normalΦ false) normald z = γ_{50} normalΔ O_{2} false(2 normalm false) + 50 \cdot normalΦ,

where Φ = O 2 (50 m) represents the background concentration of O 2 which upwells into surface waters as part of the estuarine circulation in this region, and γ 50 is a scale depth to relate the measured anomaly Δ O 2 (2 m) from this background value with a depth integrated value on short time scales. The integration depth of 50 m is chosen because it encompasses the euphotic zone, which, if using the usual heuristic of “1% Photosynthetically Active Radiation level,” is typically between 10 and 30 m deep (Figure b), but is still shallow enough to be unaffected by advective effects in deeper water (Pawlowicz et al, ; Riche & Pawlowicz, ).…”

Section: Resultsmentioning

confidence: 99%

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Diurnal and Seasonal Variability of Near‐Surface Oxygen in the Strait of Georgia

2019

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Dissolved oxygen (O2) concentrations in waters of the ocean surface mixed layer are generally close to thermodynamic equilibrium with atmospheric concentrations. However, near‐surface O2 levels are also affected by other processes, including primary productivity, and thus measurements of near‐surface O2 can in theory be used to estimate productivity. Here we discuss variations in near‐surface O2 concentrations in the Strait of Georgia by examining a variety of data sets, focusing primarily on ferry‐based measurements over a 3‐year period (2015–2017). Both diurnal, seasonal, and interannual variations are quantified, and various fluxes into and out of the surface waters are estimated so that the degree to the measured oxygen variations representing biological activity can be assessed. On average, advective and vertical transport makes only a small negative contribution, while other budget terms show a strong seasonal cycle, lowest in winter, peaking in spring and slowly dropping to winter level during summer and autumn. For most of the year, the air‐sea flux is the largest term, but the storage term is important during the spring blooms. Diurnal variations of 5–10% saturation in measured oxygen levels must therefore largely reflect diurnal cycles in productivity and respiration. We estimate respiration effects from the rate of decay of O2 at night, which yields an average respiration rate of 459 mmol·m−2·day−1. This value is almost an order of magnitude larger than the other budget terms we have discussed, suggesting that a future focus on diurnal variations might provide most insight into biological processes in the Strait.

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“…In order to estimate O 2int , we require a conversion factor relating depth‐integrated values to ferry measurements:

O_{2 int} = \int_{0}^{50 normalm} O_{2} false(z false) normald z = \int_{0}^{50 normalm} false(normalΔ O_{2} false(z false) + normalΦ false) normald z = γ_{50} normalΔ O_{2} false(2 normalm false) + 50 \cdot normalΦ,

Section: Resultsmentioning

confidence: 99%

“…"1% Photosynthetically Active Radiation level," is typically between 10 and 30 m deep (Figure 3b), but is still shallow enough to be unaffected by advective effects in deeper water (Pawlowicz et al, 2007;Riche & Pawlowicz, 2014).…”

Section: Depth Variation Of Omentioning

confidence: 99%

Diurnal and Seasonal Variability of Near‐Surface Oxygen in the Strait of Georgia

2019

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“…Virtually none of the light that enters the SoG passes all the way through the surface estuarine outflow layer. The depth of separation between the outflowing and inflowing layers has been modelled at 50 m (Pawlowicz et al 2007) and 30 m (Riche and Pawlowicz 2014), and the depth of the Fraser River plume at 15 m (Johannessen et al 2006;Masson 2006). The more highly depth-resolved profiles shown here (Figs.…”

Section: Scalar Irradiance and The Average Cosinementioning

confidence: 85%

Underwater optical environment in the coastal waters of British Columbia, Canada

Loos

Costa

Johannessen

2017

FACETS

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We describe the underwater light field of the Strait of Georgia in spring and summer, using apparent optical properties (reflectance, attenuation coefficient of downwelling irradiance, the average cosine of downwelling irradiance, and the attenuation of scalar irradiance). Both the attenuation and reflectance of photosynthetically available radiation (PAR; 400-700 nm) are highest in the turbid waters of the Fraser River plume, due to scattering by mainly inorganic particles and absorption by coloured dissolved organic matter, phytoplankton, and other organic particles. Light is most diffuse in the surface waters of the plume and least diffuse at depth and away from the plume. Throughout the Strait, blue and red wavelengths are attenuated most rapidly resulting in a green peak of reflectance, the portion of the electromagnetic spectrum that penetrates the most deeply. PAR is attenuated to 1% of its surface intensity within 6-22 m in the spring and 4-23 m in the summer. For red and blue light, the depth of 1% penetration is never deeper than 9 m. All of the visible radiation, with the exception of some green light, is absorbed within the outflowing layer (15-30 m) that is exported from the Strait with the estuarine circulation. The rapid extinction of light helps to explain the very shallow distribution of phytoplankton.

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“…The Salish Sea estuarine circulation is driven by significant freshwater input, dominated by that of the Fraser River (Griffin and LeBlond 1990;Li et al 1999;Riche and Pawlowicz 2014). The IW is formed in the Haro Strait area by tidal mixing between outflowing surface water, with a large seasonal temperature cycle, and inflowing deeper Pacific water.…”

Section: A Regional Overviewmentioning

confidence: 99%

“…However, these views of the circulation are often qualitative since speeds are not well known, and in certain cases a geostrophically controlled circulation could be directed along isopleths rather than across them. Quantitative tracer-based approaches include the ''box-model''-based Knudsen relations for estuarine flow (Hansen and Rattray 1965;MacCready et al 2018) or more complex variations thereof, applied locally by Pawlowicz (2001), Pawlowicz (2014), andMacCready et al (2021); or optimal water mass analyses (Tomczak 1981)-this latter approach was previously used along the thalweg of the Salish Sea as a whole by Masson (2006).…”

Section: Introductionmentioning

confidence: 99%

A study of intermediate water circulation in the Strait of Georgia using tracer-based, Eulerian, and Lagrangian methods

Stevens

Pawlowicz

Allen

2021

Journal of Physical Oceanography

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The intermediate circulation of the Strait of Georgia, British Columbia, Canada, plays a key role in dispersing contaminants throughout the Salish Sea, yet little is known about its dynamics. Here, we use hydrographic observations and hindcast fields from a regional 3D model to approach the intermediate circulation from three perspectives. Firstly, we derive and model a “seasonality” tracer from temperature observations to age the water, estimate mixing, and infer circulation. Secondly, we analyze modeled velocity fields to create mean current maps and examine the advective and diffusive components of the mean flow field. Lastly, we calculate Lagrangian trajectories to derive Transit Time Distributions and Lagrangian statistics. In combination, these analyses provide an overview of the mean intermediate circulation that can be summarized as follows: subducting water in Haro Strait ventilates the intermediate water primarily via an up-strait boundary current that flows along the eastern shores of the southernmost basin in 1–2 months. This inflowing water is either incorporated into the interior of the basin, recirculated southwards, or transported into the northernmost basin, mixing steadily with adjacent water masses during its transit. A second, shallower ventilating jet emanates southwards from Discovery Passage, locally modifying the Haro Strait inflow signal. Outside of these well-defined advective features, diffusive transport dominates in the majority of the region. The intermediate renewal signal fully ventilates the region in 100–140 days, which serves as a benchmark for contaminant dispersal timescale estimates.

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Variability in a fjord-like coastal estuary I: Quantifying the circulation using a formal multi-tracer inverse approach

Cited by 9 publications

References 29 publications

Diurnal and Seasonal Variability of Near‐Surface Oxygen in the Strait of Georgia

Diurnal and Seasonal Variability of Near‐Surface Oxygen in the Strait of Georgia

Underwater optical environment in the coastal waters of British Columbia, Canada

A study of intermediate water circulation in the Strait of Georgia using tracer-based, Eulerian, and Lagrangian methods

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