Water exchange and its relationships with external forcings and residence time in Chesapeake Bay

Xiong, Jilian; Shen, Jian; Qin, Qubin; Du, Jiabi

doi:10.1016/j.jmarsys.2020.103497

Cited by 19 publications

(17 citation statements)

References 63 publications

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“…Many studies have addressed the impact of the longitudinal and lateral topographic variations on mixing and estuarine circulation (e.g., Farmer & Smith, 1980; Klymak & Gregg, 2004; Peters, 1999; Valle‐Levinson et al., 2003), but few studies focus on the influence of along‐channel topographic variations on material transport and retention. The long RT of the whole CB and some unique phenomena around the RS region, such as the distinct longitudinal gradient in the vertical mean RT (Du & Shen, 2016), the significance of bottom upstream transport of DO (Scully, 2016a), and the evident spatial variations of the long‐term water exchange (Xiong et al., 2021), suggest that the bathymetric variation plays an important role in water and material transport and retention inside the bay. The importance of the RS, characterized as one of the centers for tidal energy dissipation in CB (Zhong & Li, 2006), can be further analogous to the intensified mixing at a sill near the mouth of a fjord (Scully, 2016a).…”

Section: Discussionmentioning

confidence: 99%

“…Lateral advection can also directly influence the along‐estuary momentum balance (e.g., Geyer et al., 2020; Lacy et al., 2003; Lerczak & Rockwell Geyer, 2004; Li & Li, 2012; Scully et al., 2009; Zhou et al., 2020). On a monthly to annual timescale, studies show that freshwater discharge and wind forcing are two dominant drivers for the seasonal and interannual variations of exchange flow, while exchange flow responds non‐monotonically to the river discharge (Du et al., 2018; Xiong et al., 2021).…”

Section: Introductionmentioning

confidence: 99%

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Exchange Flow and Material Transport Along the Salinity Gradient of a Long Estuary

2021

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Exchange Flow and Material Transport Along the Salinity Gradient of a Long Estuary

2021

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“…The horizontal pattern of the VPA also reverses between the shallow and deep water compared to the VDA in these regions. In particular, the shallow flanks have much higher VPA than the deep channel, which has fast tidal currents (Xiong et al., 2021b) and strong shear. The higher VPA over the shallow flanks corresponds to the low resuspension frequency (regions shown in Moriarty et al., 2020), resulting in the lengthy material retention on the seabed.…”

Section: Resultsmentioning

confidence: 99%

Vertical Transport Timescale of Surface‐Produced Particulate Material in the Chesapeake Bay

Xiong

Shen

2022

JGR Oceans

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Accumulation and remineralization of surface‐produced particulate organic matter (POM) in the water column and seabed link closely to hypoxia and the health of aquatic ecosystems. The POM retention time provides a key timescale to interpret biochemical reaction processes. In this study, we investigated the spatiotemporal variations in the vertical particulate age (VPA) of surface‐produced POM, which is the mean time elapsed since the particulates last contact the surface, by incorporating major physical processes including sinking, resuspension, and deposition in the Chesapeake Bay. It was found that the vertical transport time for the particulates (i.e., VPA) is much longer than the dissolved counterparts as the former consists of new material from the surface and the resuspended aged material that has elongated resting on the seabed after deposition. The VPA is sensitive to settling velocity, especially in low‐frequent resuspension environments, and varies over 2 orders of magnitude with settling velocity from 0 to 10 m/day. Slow‐sinking material can remain in suspension and seldom settle to the seabed, thus mainly contribute to pelagic processes, while the fast‐sinking material connects closely with benthic processes. The seasonality of VPA decreases as the settling velocity increases. No significant difference in VPA was found between wet and dry years, yet the episodic strong flood events entrain old materials from the depositional lateral shoals to increase VPA in the channel. The transport age bridges cross disciplinaries by providing the fourth‐dimensional age information as a common currency to compare the physical transport timescale with the timescales for biochemical reactions.

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“…Amongst these, residence time (RT) and exposure time (ET) are the most useful descriptors to estimate the mixing and renewal of estuarine waters (Zhang et al, 2010;Xiong et al, 2021) and, therefore, to understand estuarine dynamics. RT of a water parcel is an integrative parameter that measures the renewal time for a given water parcel or water body (Defne and Ganju, 2015) and is defined as the time the water will spend in the domain of interest until leaving it for the first time.…”

Section: Introductionmentioning

confidence: 99%

“…Estuarine hydrodynamics, RT, and ET vary in both space and time (Zhang et al, 2010;Azhikodan and Yokoyama, 2016;Bárcena et al, 2016). The combined effects of several meteoceanographic drivers (tides, riverine flows and meteorological data, such as wind) and estuarine geomorphology shape the hydrodynamics, RT and ET on timescales ranging from hours to months (Bárcena et al, 2012;Defne and Ganju, 2015;Xiong et al, 2021). Understanding how long water is retained in an estuary and how quickly water is flushed from the water body is essential to ascertain the health vulnerability of the estuary in areas with significant pollutant loadings (Bárcena et al, 2017a).…”

Section: Introductionmentioning

confidence: 99%

The Influence of the River Discharge on Residence Time, Exposure Time and Integrated Water Fractions for the Tagus Estuary (Portugal)

et al. 2022

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Understanding how long water is retained in an estuary and how quickly it is completely flushed is essential to estimate an estuary’s health in areas with significant pollutant loadings. The present study analyses the effect of five different Tagus River discharge scenarios ranging from low to extreme on residence time (RT), exposure time (ET) and integrated water fractions inside pre-established Tagus estuary areas, to identify its most vulnerable areas to pollution. The 3D version of the MOHID hydrodynamic model coupled to a lagrangian tool was used. The increase of the river discharge generated high current velocities which, in turn, led to an increased rate of tracers leaving the estuary. As a consequence, RT and ET decreased from 59 to 3.5 days under a low and extreme river discharge scenario, respectively. Under a low river discharge, significant differences were observed between RT and ET in the areas located in the main body of the estuary and in the bays. As river discharge increased, RT and ET decreased in all areas of the estuary and those differences faded, with the greatest differences observed in the areas situated along the south margin. In general, results showed that with high river discharges the tracers released in the upper estuary are spread throughout the estuary, but mainly in downstream areas. However, when the river discharge reached exceptionally high values, local eddies were formed, leading to the retention of the tracers in the estuary’s south margin and inner bays. The results in this study allowed to identify the most vulnerable areas within the estuary as a function of the river discharge.

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Water exchange and its relationships with external forcings and residence time in Chesapeake Bay

Cited by 19 publications

References 63 publications

Exchange Flow and Material Transport Along the Salinity Gradient of a Long Estuary

Exchange Flow and Material Transport Along the Salinity Gradient of a Long Estuary

Vertical Transport Timescale of Surface‐Produced Particulate Material in the Chesapeake Bay

The Influence of the River Discharge on Residence Time, Exposure Time and Integrated Water Fractions for the Tagus Estuary (Portugal)

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