Momentum balances on the inner continental shelf at Martha's Vineyard Coastal Observatory

Fewings, Melanie R.; Lentz, Steven J.

doi:10.1029/2009jc005578

Cited by 34 publications

(71 citation statements)

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“…The Coriolis force and the radiation stress played secondary roles in the momentum balance. In particular, the radiation stresses were 1 order of magnitude smaller than the dominant acceleration, pressure gradient and frictional terms, consistent with other studies that ignored wave forcing outside the surf zone (Lentz et al, 1999;Fewings and Lentz, 2010). In a region 150 km north of our study area, in water depths of 28 m off the Tet River, Michaud et al (2012) confirmed numerically that the wave effects on the inner-shelf circulation are relatively small even during a storm event.…”

Section: Momentum Evolution In the Inner Shelfsupporting

confidence: 75%

“…The PGFR includes a contribution by a direct response to the local wind forcing (for instance during 13 March), which is not immediately obvious in PGFO. During the wind peaks, the positive pressure-gradient force partially counterbalanced the wind stress in a manner consistent with other observational studies (Lee et al, 1984;Lentz, 1994;Fewings and Lentz, 2010). Despite its potentially large uncertainty, we use PGFR in the analysis of the momentum balance evolution because it is consistent with the estimates for the other momentum terms.…”

Section: Momentum Balance In the Inner Shelfmentioning

confidence: 65%

“…The circulation over the inner shelf is often investigated through the analysis of the momentum balance in different regions, although most studies have usually focused on those conditions averaged over periods longer than 1 week (Lee et al, 1984;Lentz and Winant, 1986;Lentz et al, 1999, Maza et al, 2006Fewings and Lentz, 2010;Grifoll et al, 2012Grifoll et al, , 2013. In contrast, the analysis of the momentum terms at daily and shorter timescales under rapidly changing forcing conditions remains less explored.…”

Section: Introductionmentioning

confidence: 99%

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Temporal evolution of the momentum balance terms and frictional adjustment observed over the inner shelf during a storm

et al. 2016

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Abstract. We investigate the rapidly changing equilibrium between the momentum sources and sinks during the passage of a single two-peak storm over the Catalan inner shelf (NW Mediterranean Sea). Velocity measurements at 24 m water depth are taken as representative of the inner shelf, and the cross-shelf variability is explored with measurements at 50 m water depth. During both wind pulses, the flow accelerated at 24 m until shortly after the wind maxima, when the bottom stress was able to compensate for the wind stress. Concurrently, the sea level also responded, with the pressuregradient force opposing the wind stress. Before, during and after the second wind pulse, there were velocity fluctuations with both super-and sub-inertial periods likely associated with transient coastal waves. Throughout the storm, the Coriolis force and wave radiation stresses were relatively unimportant in the along-shelf momentum balance. The frictional adjustment timescale was around 10 h, consistent with the efolding time obtained from bottom drag parameterizations. The momentum evolution at 50 m showed a larger influence of the Coriolis force at the expense of a decreased frictional relevance, typical in the transition from the inner to the midshelf.

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Section: Momentum Evolution In the Inner Shelfsupporting

confidence: 75%

Section: Momentum Balance In the Inner Shelfmentioning

confidence: 65%

Section: Introductionmentioning

confidence: 99%

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Temporal evolution of the momentum balance terms and frictional adjustment observed over the inner shelf during a storm

et al. 2016

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“…Studies over different inner-shelves (Lentz et al, 1999;Liu and Weisberg, 2005;Fewings and Lentz, 2010) seem to agree that the circulation is mainly forced by along-shelf pressure gradient (generated by local wind forcing) and wind stress, though other processes can also be important depending on water depth and wave regime.…”

Section: Discussionmentioning

confidence: 97%

Diurnal variability of inner-shelf circulation in the lee of a cape under upwelling conditions

Lamas

Peliz

Dias

et al. 2017

Continental Shelf Research

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to study the diurnal variability of the cross-shelf circulation. This period was chosen because it had a steady upwellingfavourable wind condition modulated by a diurnal cycle much similar to sea breeze.The daily variability of the observed cross-shelf circulation consisted of three distinct periods: a morning period with a 3-layer vertical structure with onshore velocities at mid-depth, a mid-day period where the flow is reversed and has a 2-layer structure with onshore velocities at the surface and offshore flow below, and, lastly, in the evening, a 2-layer period with intensified offshore velocities at the surface and onshore flow at the bottom. The observed cross-shelf circulation showed a peculiar vertical shape and diurnal variability different from several other systems described in literature. We hypothesize that the flow reversal of the cross-shelf circulation results as a response to the rapid change of the wind magnitude and direction at mid-day with the presence of the cape north of the mooring site influencing this response.A numerical modelling experiment exclusively forced by winds simulated successfully most of the circulation at the ADCP site, especially the mid-day reversal and the evening's upwelling-type structure. This supports the hypothesis that the cross-shelf circulation at diurnal timescales is mostly wind-driven. By analysing the 3D circulation in the vicinity of Cape Sines we came to the conclusion that the diurnal variability of the wind and the flow interaction with topography are responsible for the circulation variability at the ADCP site, though only a small region in the south of the cape showed a similar diurnal variability.The fact that the wind diurnally undergoes relaxation and intensification strongly affects the circulation, promoting superficial onshore flows in the leeside of Cape Sines. Despite the small-scale nature of the observed cross-shelf circulation, onshore flows as the ones described in this study can be particularly helpful to understand the transport and settlement of larvae in this region and in other regions with similar topography and wind characteristics.

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“…The inner shelf is defined as the region offshore of the surf zone where surface and bottom boundary layers overlap (Lentz 1995). The dynamics in this region are dominated by the forcing of alongshore wind stress and alongshore pressure gradients, balanced by bottom stress response (Pettigrew 1980, Lentz and Winant 1986, Lentz 1994, Liu and Weisberg 2005, Gutierrez et al 2006, Fewings and Lentz 2010, Lentz and Fewings 2012. Coastal and bathymetric variations modify inner shelf circulation and the momentum balance (Dragos and Aubrey 1990, Yankovsky and Garvine 1998, van de Meene and van Rijn 2000a, Kirincich and Barth 2009, Kumar et al 2013).…”

Section: Chapter 1: Introductionmentioning

confidence: 99%

Alongshore Momentum Balance Over Shoreface-Connected Ridges, Fire Island, Ny

Ofsthun¹

2016

Geological Society of America Abstracts With Programs

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Bathymetric variations, such as shoreface-connected ridges (SFCRs), modify inner shelf circulation, altering the significance of and relationships between alongshore momentum balance terms. The inner shelf of Fire Island, NY provides a study site representative of SFCRs around the world. During the winter of 2014, hydrodynamic observations (~12 m depth) from 6 ADCPs, 3 SeaGauge pressure sensors, 2 tide gauges, and 2 meteorological buoys were collected over a region of the inner shelf spanning a full wavelength of one such SFCR. Analysis of the data, under westward wind forcing, revealed a predominantly alongshore circulation with localized offshore (onshore) current veering over the SFCR crests (troughs). This circulation pattern, and its implied sediment dynamics, has long been recognized as the primary maintenance mechanism for SFCRs.Momentum balance analysis revealed local acceleration, advective acceleration, and bottom stress to be balanced by wind stress and large-scale (>100 km) pressure gradient force (correlation r=0.75). Current veering of alongshore flows is hypothesized to result from a frictional torque-induced rotation stemming from bottom stress variations across SFCRs.

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Momentum balances on the inner continental shelf at Martha's Vineyard Coastal Observatory

Cited by 34 publications

References 50 publications

Temporal evolution of the momentum balance terms and frictional adjustment observed over the inner shelf during a storm

Temporal evolution of the momentum balance terms and frictional adjustment observed over the inner shelf during a storm

Diurnal variability of inner-shelf circulation in the lee of a cape under upwelling conditions

Alongshore Momentum Balance Over Shoreface-Connected Ridges, Fire Island, Ny

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