Brink Kenneth H.

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Kenneth H.
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Article

Topographic rectification in a stratified ocean

2011-07-01 , Brink, Kenneth H.

Mean flow generation by oscillating currents is considered in an idealized stratified ocean with a corrugated shelf-slope topography. Numerical model results for near-bottom mean along-isobath flow show a general parameter dependence similar to that found with no stratification (Brink, 2010). Stratification, however, makes the interior rectified flow depth-dependent, and usually bottom-intensified. Scalings for both the mean flow and its vertical dependence are developed and evaluated. Two crude comparisons against observed mean oceanic flows suggest that the present results may parameterize the mean flow magnitude correctly.

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Article

Some considerations about coastal ocean observing systems

2017-05-01 , Brink, Kenneth H. , Kirincich, Anthony R.

Coastal ocean observing capabilities are evolving rapidly, both in terms of sensors and in terms of the volume of information available. We discuss the aspects of the coastal ocean that make it a unique environment, both in terms of physical processes and measurement techniques. Although many global-level systems are relevant to the coastal ocean, we concentrate on treating systems that are unique to the continental shelf environment. Further, we briefly discuss examples of measurement systems that would be useful for developing and driving ocean prediction systems.

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Preprint

Water column structure and statistics of denmark strait overflow water cyclones

2013-10-30 , von Appen, Wilken-Jon , Pickart, Robert S. , Brink, Kenneth H. , Haine, Thomas W. N.

Data from seven moorings deployed across the East Greenland shelfbreak and slope 280 km downstream of Denmark Strait are used to investigate the characteristics and dynamics of Denmark Strait Overflow Water (DSOW) cyclones. On average, a cyclone passes the mooring array every other day near the 900 m isobath, dominating the variability of the boundary current system. There is considerable variation in both the frequency and location of the cyclones on the slope, but no apparent seasonality. Using the year-long data set from September 2007 to October 2008, we construct a composite DSOW cyclone that reveals the average scales of the features. The composite cyclone consists of a lens of dense overflow water on the bottom, up to 300 m thick, with cyclonic flow above the lens. The azimuthal flow is intensified in the middle and upper part of the water column and has the shape of a Gaussian eddy with a peak depth-mean speed of 0.22 m/s at a radius of 7.8 km. The lens is advected by the mean flow of 0.27 m/s and self propagates at 0.45 m/s, consistent with the topographic Rossby wave speed and the Nof speed. The total translation velocity along the East Greenland slope is 0.72 m/s. The self-propagation speed exceeds the cyclonic swirl speed, indicating that the azimuthal flow cannot kinematically trap fluid in the water column above the lens. This implies that the dense water anomaly and the cyclonic swirl velocity are dynamically linked, in line with previous theory. Satellite sea surface temperature (SST) data are investigated to study the surface expression of the cyclones. Disturbances to the SST field are found to propagate less quickly than the in-situ DSOW cyclones, raising the possibility that the propagation of the SST signatures is not directly associated with the cyclones.

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Article

A new era for The Sea

2017-05-01 , Brink, Kenneth H. , McCarthy, James J.

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Article

Rectified flow in a stratified coastal ocean

2018-01 , Brink, Kenneth H.

An idealized numerical model is used to explore the generation of mean flows by oscillating wind forcing in a stratified coastal ocean with no alongshore variability, i.e., where neither barotropic nor baroclinic instability is a factor. On the inner shelf, where surface-to-bottom mixing occurs, a mean cross-shelf flow develops, as examined by Castelao et al. (2010), and the present results suggest that this flow can remain two-dimensional if there is a nonzero cross-shelf density gradient. Offshore of the inner shelf, where the water column is stratified, a mean alongshore flow develops in the direction opposite to coastal-trapped wave propagation. This flow is associated with cross-shelf density gradients that are set up by the asymmetry between onshore and offshore flow in the bottom boundary layer. Both forms of rectified flow (cross-shelf and alongshore) are sensitive to the presence of surface heating, and the rectifications can be readily masked by the effect of a steady alongshore wind stress.

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Article

Evaporative dense water formation and cross-shelf exchange over the northwest Australian inner shelf

2010-06-29 , Shearman, R. Kipp , Brink, Kenneth H.

High-resolution surveys of oceanographic and atmospheric conditions made during the winter over the inner shelf off northwest Australia are used to examine the coastal ocean response to large outgoing heat and freshwater fluxes. Relatively cool, low-humidity air blows off the Australian continent out over the tropical continental shelf, resulting in a large mean latent heat flux (−177 W m−2) that overwhelms insolation and, along with the outgoing long-wave radiation, results in substantial net cooling (−105 W m−2) and evaporative freshwater flux (0.6 cm d−1). The inner shelf is characterized by increasingly cool, salty, and dense waters onshore, with a strong front near the 25 m isobath. The front is evident in satellite sea surface temperature (SST) imagery along the majority of the northwest Australian shelf, exhibiting a complex filamentary and eddy structure. Cross-shelf buoyancy fluxes estimated from the mean, two-dimensional heat and salt budgets are comparable to parameterizations of cross-shelf eddy driven fluxes; however, the same fluxes can be achieved by cross-shelf transports in the bottom boundary layer of about 0.5 m2 s−1 (and an overlying return flow).

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Article

Bottom boundary layer flow and salt injection from the continental shelf to slope

2006-07-14 , Brink, Kenneth H. , Shearman, R. Kipp

Austral winter oceanographic measurements from the northwest Australian continental shelf reveal salty water forming evaporatively inshore, moving across the wide shelf near the bottom and into the adjacent open ocean when the shelf edge alongshore flow is equatorward. The salt tongue is absent during more normal conditions, when the poleward Leeuwin Current is present. We hypothesize that the flow reversal enables shelf-wide bottom boundary layer (Ekman) transport and thus creates the shelf-edge convergence that accounts for the observed salt tongue. This flow is absent under sustained normal conditions because of buoyancy arrest in the bottom boundary layer.

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Technical Report

Moored current meter and wind recorded measurements near Point Conception, California : the 1983 OPUS observations

1985-01 , Brink, Kenneth H. , Chausse, Dolores , Davis, Russ E.

The OPUS (Organization of Persistent Upwelling Structures) program deployed two current meter (VMCM) moorings near Point Conception, California, during April-July 1983. Current and temperature data from these moorings are summarized here. In addition, data from two nearby NDBC (National Data Buoy Center) meteorological buoys are presented.

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Article

Topographic rectification in a forced, dissipative, barotropic ocean

2010-05-01 , Brink, Kenneth H.

Barotropic current rectification by topographic irregularities is treated for a case with bottom friction and fluctuating forcing. Geometries both with underlying shelf-slope topography and with no mean topographic slope are considered. In common with many previous studies of this sort, the resulting time-mean flow roughly follows isobaths in the direction that long topographic Rossby waves travel, but the mean flow often deviates locally from this rule. Further, as might be expected, there is an area-averaged correlation of pressure and bottom slope in the sense that would propel the mean flow. If the topographic irregularities have a length scale shorter than roughly a particle fluctuation excursion, then the typical along-isobath mean flow is proportional to the bottom slope, the irregularity length scale, the amplitude of the cross-isobath velocity fluctuations, and the inverse of the water depth. If the spatial scale of the irregularities is greater than roughly a particle excursion, then the resulting mean flow does not depend on irregularity length scale, but does depend on the Coriolis parameter, the bottom slope, cross-isobath velocity squared, the inverse depth and the inverse frequency squared. For large amplitude fluctuations, eddy momentum transport leads to a further inverse proportionality of mean flow to the strength of bottom friction. The overall mean flow parameterization holds only in a statistical sense (as opposed to point-by-point) because of the spatial complexity of typical flows. In a forced, dissipative system, the mean flow generation is often just tidal rectification (e.g., Loder, 1980) if the particle excursion is short relative to topographic scales. However, as the irregularity scale decreases, mean flow becomes weaker.

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Article

Rossby waves with continuous stratification and bottom friction

2018-09-17 , Brink, Kenneth H. , Pedlosky, Joseph

Published observations of subinertial ocean current variability show that the vertical structure is often well described by a vertical mode that has a node of horizontal velocity at the bottom rather than the traditional node of vertical velocity. The theory of forced and free linear Rossby waves in a continuously stratified ocean with a sloping bottom and bottom friction is treated here to see if frictional effects can plausibly contribute to this phenomenon. For parameter values representative of the mesoscale, bottom dissipation by itself appears to be too weak to be an explanation, although caution is required because the present approach uses a linear model to address a nonlinear phenomenon. One novel outcome is the emergence of a short-wave, bottom-trapped, strongly damped mode that is present even with a flat bottom.

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Technical Report

FASINEX moored current meter array data report including WHOI meteorologically instrumented surface moorings (F2-845, F4-846, F6-847. F8-848. F10-849) and WHOI long term subsurface moorings (F1-829, F12-830)

1988-12 , Pennington, Nancy J. , Weller, Robert A. , Brink, Kenneth H.

The Frontal Air-Sea Interaction Experiment (FASINEX) examined air-sea interaction in the vicinity of sea surface temperature fronts in the Subtropical Convergence Zone (STCZ). Mooring measurements were made from five surface, four Profiling Current Meter (PCM) and two longer duration subsurface moorings. The surface and PCM moorings, which made up the FASINEX central array were set in January 1986 and remained on station for six months. The two outlying subsurface moorings, set 90 miles south and 30 miles north of the central array were deployed in October 1984 and were recovered with the central array moorings in June 1986. The surface moorings collected oceanographic and meteorological data, using a 3-meter instrumented discus buoy and eight to ten Vector Measuring Current Meters (VMCMs) and Vector Averaging Current Meters (VACMs). The surface buoy carried a Vector Measuring Wind recorder (VAWR) and a Meteorological Recorder (MR) which measured wind speed and direction, sea surface temperature (SST), air temperature, insolation, barometric pressure and relative humidity. The MR also transmitted meteorological and engineering data via ARGOS. The VMCMs and VACMs, placed from 10 to 4000 m, measured oceanic velocities and temperatures. The subsurface moorings measured oceanic velocities and temperature from 160 to 4060 m, carrying a total of seven VACMs and a WOTAN (Wind Observations Through Ambient Noise). This report presents meteorological and oceanographic data from the seven W.H.O.I. moorings, with major emphasis on the surface mooring data. Details of the moored array and a statement of data return and quality are also included.

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Technical Report

Coastal Ocean Processes : a science prospectus

1992-04 , Brink, Kenneth H. , Bane, John M. , Church, Thomas M. , Fairall, Christopher W. , Geernaert, G. L. , Hammond, D. E. , Henrichs, S. M. , Martens, C. S. , Nittrouer, Charles A. , Rogers, D. P. , Roman, Michael R. , Roughgarden, J. D. , Smith, R. L. , Wright, L. Donelson , Yoder, James A.

CoOP (Coastal Ocean Processes) is an organization meant to study major interdisciplinary scientific problems in the coastal ocean. Its goal is "to obtain a new level of quantitative understanding of the processes that dominate the transformations, transport and fates of biologically, chemically and geologically important matter on the continental margin". Central to obtaining this understanding will be advances in observing and modeling the cross-shelf component of transport. More specific objectives are to understand 1) cross-margin exchanges, 2) air sea exchanges, 3) benthic-pelagic exchanges, 4) terrestrial inputs and 5) biological and chemical transformations within the water column. CoOP research will be carried out primarly through a series of process-oriented field studies, each involving about two years of measurements. Each of these field studies is to be initiated and defined through a community workshop. In addition to the process studies, CoOP will also involve modeling, long time series, exploratory studies, remote sensing, technological innovation, data archiving and communications. A CoOP pilot study has been approved for funding by the National Science Foundation, and funding will begin in 1992. The CoOP science effort is thus already underway.

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Article

Buoyancy arrest and bottom Ekman transport. Part II : oscillating flow

2010-04 , Brink, Kenneth H. , Lentz, Steven J.

The effects of a sloping bottom and stratification on a turbulent bottom boundary layer are investigated for cases where the interior flow oscillates monochromatically with frequency ω. At higher frequencies, or small slope Burger numbers s = αN/f (where α is the bottom slope, N is the interior buoyancy frequency, and f is the Coriolis parameter), the bottom boundary layer is well mixed and the bottom stress is nearly what it would be over a flat bottom. For lower frequencies, or larger slope Burger number, the bottom boundary layer consists of a thick, weakly stratified outer layer and a thinner, more strongly stratified inner layer. Approximate expressions are derived for the different boundary layer thicknesses as functions of s and σ = ω/f. Further, buoyancy arrest causes the amplitude of the fluctuating bottom stress to decrease with decreasing σ (the s dependence, although important, is more complicated). For typical oceanic parameters, arrest is unimportant for fluctuation periods shorter than a few days. Substantial positive (toward the right when looking toward deeper water in the Northern Hemisphere) time-mean flows develop within the well-mixed boundary layer, and negative mean flows exist in the weakly stratified outer boundary layer for lower frequencies and larger s. If the interior flow is realistically broad band in frequency, the numerical model predicts stress reduction over all frequencies because of the nonlinearity associated with a quadratic bottom stress. It appears that the present one-dimensional model is reliable only for time scales less than the advective time scale that governs interior stratification.

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Article

Pathways and mechanisms of offshore water intrusions on the Espírito Santo Basin shelf (18°S–22°S, Brazil)

2016-07-30 , Palóczy, Andre , Brink, Kenneth H. , da Silveira, Ilson C. A. , Arruda, Wilton Z. , Martins, Renato P.

The pathways and physical mechanisms associated with intrusions of cold, nutrient-rich South Atlantic Central Water (SACW) on the continental shelf of the Espírito Santo Basin (ESB), off southeast Brazil (18°S–22°S), are investigated. To this end, a set of process-oriented, Primitive-Equation (PE) numerical models are used, together with an independent and more complete PE model, available observations and simple theoretical ideas. SACW enters the model ESB shelf mostly through two preferential pathways along the Tubarão Bight (TB, 19.5°S–22°S). These pathways are found to be locations where an equatorward along-isobath pressure gradient force (PGFy*) of inline image m s−2) develops in response to steady wind forcing. This equatorward PGFy* is essentially in geostrophic balance, inducing onshore flow across the shelf edge, and most of the shelf proper. The Brazil Current (BC) imparts an additional periodic (in the along-shelf direction) PGFy* on the shelf. The intrinsic pycnocline uplifting effect of the BC in making colder water available at the shelf edge is quantified. The BC also induces local intrusions by inertially overshooting the shelf edge, consistent with estimated Rossby numbers of inline image0.3–0.5. In addition, the planetary β-effect is related to a background equatorward PGFy*. A modified Arrested Topographic Wave model is shown to be a plausible rationalization for the shelf-wide spreading of the pressure field imparted by the BC at the shelf edge. The deep-ocean processes examined here are found to enhance the onshore transport of SACW, while wind forcing is found to dominate it at leading order.

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Technical Report

Programs for computing properties of coastal-trapped waves and wind-driven motions over the continental shelf and slope

1985-04 , Brink, Kenneth H. , Chapman, David C.

Documentation and listings are presented for a sequence of computer programs to be used for problems in continental shelf dynamics. Three of the programs are to be used for computing properties of free and forced coastal-trapped waves. A final program may be used to compute wind-driven fluctuations over the continental shelf and slope.

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Article

What determines the spatial pattern in summer upwelling trends on the U.S. West Coast?

2012-08-09 , Seo, Hyodae , Brink, Kenneth H. , Dorman, Clive E. , Koracin, Darko , Edwards, Christopher A.

Analysis of sea surface temperature (SST) from coastal buoys suggests that the summertime over-shelf water temperature off the U.S. West Coast has been declining during the past 30 years at an average rate of −0.19°C decade−1. This cooling trend manifests itself more strongly off south-central California than off Oregon and northern California. The variability and trend in the upwelling north of off San Francisco are positively correlated with those of the equatorward wind, indicating a role of offshore Ekman transport in the north. In contrast, Ekman pumping associated with wind stress curls better explains the stronger and statistically more significant cooling trend in the south. While the coast-wide variability and trend in SST are strongly correlated with those of large-scale modes of climate variability, they in general fail to explain the southward intensification of the trend in SST and wind stress curl. This result suggests that the local wind stress curl, often topographically forced, may have played a role in the upwelling trend pattern.

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Article

Buoyancy arrest and shelf–ocean exchange

2012-04 , Brink, Kenneth H.

When steady flow in a stratified ocean passes between the continental slope and open ocean, its ability to cross isobaths is potentially limited by buoyancy arrest. If the bottom Ekman transport vanishes and there are no interior stresses, then steady linear flow on an f plane must be geostrophic and follow isobaths exactly. The influence of arrest on cross-shelf transport is investigated here to establish 1) whether there are substantial penetration asymmetries between cases with upwelling and downwelling in the bottom boundary layer; 2) over what spatial scales, hence in what parameter regime, buoyancy arrest is important; and 3) the effects of depth-dependent interior flow. The problem is approached using scalings and idealized numerical models. The results show that there is little or no asymmetry introduced by bottom boundary layer behavior. Further, if the stratification is weak or moderate, as measured by a slope Burger number s = αN/f (where α is the bottom slope, N is buoyancy frequency, and f is the Coriolis parameter), buoyancy arrest does not exert a strong constraint on cross-isobath exchange.

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Article

Near-resonances of superinertial and tidal fluctuations at islands

2021-08-12 , Brink, Kenneth H.

A linear numerical model of an island or a tall seamount is used to explore superinertial leaky resonances forced by ambient vertically and horizontally uniform current fluctuations. The model assumes a circularly symmetric topography (including a shallow reef) and allows realistic stratification and bottom friction. As long as there is substantial stratification, a number of leaky resonances are found, and when the island’s flanks are narrow relative to the internal Rossby radius, some of the near-resonant modes resemble leaky internal Kelvin waves. Other “resonances” resemble higher radial mode long gravity waves as explored by Chambers. The near-resonances amplify the cross-reef velocities that help fuel biological activity. Results for cases with the central island replaced by a lagoon do not differ greatly from the island case which has land at the center. As an aside, insight is provided on the question of offshore boundary conditions for superinertial nearly trapped waves along a straight coast.

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Article

Offshore transport of shelf water by deep-ocean eddies

2016-12-08 , Cherian, Deepak A. , Brink, Kenneth H.

At continental margins, energetic deep-ocean eddies can transport shelf water offshore in filaments that wrap around the eddy. One example is that of Gulf Stream warm-core rings interacting with the Mid-Atlantic Bight shelf. The rate at which shelf water is exported in these filaments is a major unknown in regional budgets of volume, heat, and salt. This unknown transport is constrained using a series of idealized primitive equation numerical experiments wherein a surface-intensified anticyclonic eddy interacts with idealized shelf–slope topography. There is no shelfbreak front in these experiments, and shelf water is tracked using a passive tracer. When anticyclones interact with shelf–slope topography, they suffer apparent intrusions of shelf–slope water, resulting in a subsurface maximum in offshore transport. The simulations help construct an approximate model for the filament of exported water that originates inshore of any given isobath. This model is then used to derive an expression for the total volume of shelf–slope water transported by the eddy across that isobath. The transport scales with water depth, radius, and azimuthal velocity scale of the eddy. The resulting expression can be used with satellite-derived eddy properties to estimate approximate real-world transports ignoring the presence of a shelfbreak front. The expression assumes that the eddy’s edge is at the shelf break, a condition not always satisfied by real eddies.

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Technical Report

Programs for computing properties of coastal-trapped waves and wind-driven motions over the continental shelf and slope

1987-06 , Brink, Kenneth H. , Chapman, David C.

Documentation and listings are presented for a sequence of computer programs to be used for problems in continental shelf dynamics. Three of the programs are to be used for computing properties of free and forced coastal-trapped waves. A final program may be used to compute wind-driven fluctuations over the continental shelf and slope. This second edition includes several minor revisions and corrections in the computer code and the documentation.

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