Slope water, Gulf Stream, and seasonal influences on southern Mid‐Atlantic Bight circulation during the fall‐winter transition

Rasmussen, Linda L.; Gawarkiewicz, Glen; Owens, W. Brechner; Lozier, M. Susan

doi:10.1029/2004jc002311

Cited by 28 publications

(21 citation statements)

References 26 publications

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“…This is not surprising since adding a substantial barotropic component to the velocity field might well alter the convergence/divergence patterns in the bottom boundary layer that are inherent to the theory. Rasmussen et al (2005) showed that Chapman's (2000) frontal trapping theory accurately predicted the grounding depth of the shelfbreak front using the full transport, but their observations came from the MAB where the baroclinic flow dominates and the theory does well even with the full transport (Fig. 12b).…”

Section: B Frontal Grounding Positionmentioning

confidence: 99%

The Western North Atlantic Shelfbreak Current System in Summer

Fratantoni

Pickart

2007

Journal of Physical Oceanography

132

142

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Twelve years of historical hydrographic data, spanning the period 1990-2001, are analyzed to examine the along-stream evolution of the western North Atlantic Ocean shelfbreak front and current, following its path between the west coast of Greenland and the Middle Atlantic Bight. Over 700 synoptic sections are used to construct a mean three-dimensional description of the summer shelfbreak front and to quantify the along-stream evolution in properties, including frontal strength and grounding position. Results show that there are actually two fronts in the northern part of the domain-a shallow front located near the shelf break and a deeper front centered in the core of Irminger Water over the upper slope. The properties of the deeper Irminger front erode gradually to the south, and the front disappears entirely near the Grand Banks of Newfoundland. The shallow shelfbreak front is identifiable throughout the domain, and its properties exhibit large variations from north to south, with the largest changes occurring near the Tail of the Grand Banks. Despite these structural changes, and large variations in topography, the foot of the shelfbreak front remains within 20 km of the shelf break. The hydrographic sections are also used to examine the evolution of the baroclinic velocity field and its associated volume transport. The baroclinic velocity structure consists of a single velocity core that is stronger and penetrates deeper where the Irminger front is present.

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Section: B Frontal Grounding Positionmentioning

confidence: 99%

The Western North Atlantic Shelfbreak Current System in Summer

Fratantoni

Pickart

2007

Journal of Physical Oceanography

132

142

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“…average of 75 m [Rasmussen et al, 2005]. Although the front meanders up to 50 km horizontally on short time scales, it is usually found within a narrow band (10-20 km), extending hundreds of km, following the shelf break [Loder et al, 1998b;Fratantoni and Pickart, 2007].…”

Section: General Circulation Of the Mid-atlantic Bightmentioning

confidence: 99%

Nutrient exchange and ventilation of benthic gases across the continental shelf break

2011

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[1] On western margins of ocean basins, such as the eastern continental shelf of the United States, rates of biological productivity are higher than in the open ocean, in spite of the mean downwelling circulation. We use a nonhydrostatic, three-dimensional, process study ocean model with idealized shelf-slope geometry, wind forcing, and tracers to explore the interplay between the circulation and the biogeochemistry of the shelf and slope; the pathways that can transport nutrients from the deep ocean and from the sediments to the surface ocean euphotic zone. Cross-shelf exchange between the open and coastal ocean is regulated by a shelf break front that separates light waters on the shelf from denser waters on the slope. The wind direction and strength influence both the position and slope of the isopycnals at the front, which become more vertical in response to northerly winds and flatten in response to southerly winds. When the wind direction oscillates between northerly and southerly, it pumps nutrient and gas-rich bottom boundary layer water up to the sea surface. Nutrients tend to accumulate in the benthic boundary layer during southerly winds and are pumped to the surface during periods of northerly winds. Stratification of the water column in summertime reduces the shelf break pump by dampening the effect of the winds on the movement of the front. When extrapolated over the northeast coast of the United States, the nutrients supplied by the shelf break pump from the open ocean to the coastal ocean are three times the estimated nitrogen delivered to the shelf from estuaries.

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“…The water does not exit the MAB at the shelf break but rather runs along the shelf and exits to the south near Cape Hatteras (Brian 2009). Studies by Rasmussen et al (2005) showed that the cross shelf transport at the shelf-slope edge (shelf break) is small and supports the notion of large along-shelf transport in the MAB. Between 75 and 90 % of the along-shelf sub-inertial current energy can be attributed to wind-forced motions and freely propagating waves (Noble et al 1983).…”

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confidence: 63%

Assessing the fidelity of surface currents from a coastal ocean model and HF radar using drifting buoys in the Middle Atlantic Bight

2012

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The rapid expansion of urbanization along the world's coastal areas requires a more comprehensive and accurate understanding of the coastal ocean. Over the past several decades, numerical ocean circulation models have tried to provide such insight, based on our developing understanding of physical ocean processes. The systematic establishment of coastal ocean observation systems adopting cutting-edge technology, such as high frequency (HF) radar, satellite sensing, and gliders, has put such ocean model predictions to the test, by providing comprehensive observational datasets for the validation of numerical model forecasts. The New York Harbor Observing and Prediction System (NYHOPS) is a comprehensive system for understanding coastal ocean processes on the continental shelf waters of New York and New Jersey. To increase confidence in the system's ocean circulation predictions in that area, a detailed validation exercise was carried out using HF radar and Lagrangian drifter-derived surface currents from three drifters obtained between March and October 2010. During that period, the root mean square (RMS) differences of both the eastwest and north-south currents between NYHOPS and HF radar were approximately 15 cm s −1 . Harmonic analysis of NYHOPS and HF radar surface currents shows similar tidal ellipse parameters for the dominant M 2 tide, with a mean difference of 2.4 cm s −1 in the semi-major axis and 1.4 cm s −1 in the semi-minor axis and 3°in orientation and 10°in phase. Surface currents derived independently from drifters along their trajectories showed that NYHOPS and HF radar yielded similarly accurate results. RMS errors when compared to currents derived along the trajectory of the three drifters were approximately 10 cm s −1 . Overall, the analysis suggests that NYHOPS and HF radar had similar skill in estimating the currents over the continental shelf waters of the Middle Atlantic Bight during this time period. An ensemble-based set of particle tracking simulations using one drifter which was tracked for 11 days showed that the ensemble mean separation generally increases with time in a linear fashion. The separation distance is not dominated by high frequency or short spatial scale wavelengths suggesting that both the NYHOPS and HF radar currents are representing tidal and inertial time scales correctly and resolving some of the smaller scale eddies. The growing ensemble mean separation distance is dominated by errors in the mean flow causing the drifters to slowly diverge from their observed positions. The separation distance for both HF radar and NYHOPS stays below 30 km after 5 days, and the two technologies have similar tracking skill at the 95 % level. For comparison, the ensemble mean distance of a drifter from its initial release location (persistence assumption) is estimated to be greater than 70 km in 5 days.

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Slope water, Gulf Stream, and seasonal influences on southern Mid‐Atlantic Bight circulation during the fall‐winter transition

Cited by 28 publications

References 26 publications

The Western North Atlantic Shelfbreak Current System in Summer

The Western North Atlantic Shelfbreak Current System in Summer

Nutrient exchange and ventilation of benthic gases across the continental shelf break

Assessing the fidelity of surface currents from a coastal ocean model and HF radar using drifting buoys in the Middle Atlantic Bight

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