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• 1. [Article] The Hydraulics of an Evolving Upwelling Jet Flowing around a Cape

  Upwelling jets flow alongshore in approximate geostrophic balance with the onshore pressure gradient induced by coastal upwelling. Observations of such jets have shown that they often move offshore downstream ...

  Citation × Citation Citation Abstract Copy Title: The Hydraulics of an Evolving Upwelling Jet Flowing around a Cape Author: Barth, John A., Dale, Andrew C. Upwelling jets flow alongshore in approximate geostrophic balance with the onshore pressure gradient induced by coastal upwelling. Observations of such jets have shown that they often move offshore downstream of capes, leaving a pool of upwelled water inshore. Comparisons are made between this behavior and the hydraulic transition of a potential-vorticity-conserving coastal current as it passes a topographic anomaly at which it is exactly critical to long coastal-trapped waves. An analytic 1.5-layer model of coastal hydraulics with constant potential vorticity in each layer predicts flow fields (i.e., jet separation) in critical situations that resemble observations. When scales approximate Cape Blanco on the Oregon coast, separation occurs at a jet transport of around 0.76 × 10⁶ m³ s−¹, similar to observed transports. Time-dependent, semigeostrophic calculations suggest that, during an upwelling season, the jet would evolve from a weak flow, which was subcritical everywhere and symmetric about the cape, to an exactly critical state that made a transition from subcritical to supercritical structure at the head of the cape. The predicted flow field at critical transition consists of a narrow upwelling jet upstream of the cape that moves offshore and broadens at the cape. This critical state would be accompanied by a downstream jump back to subcritical conditions. Further upwelling-favorable winds would lead to transient waves that propagated upstream and downstream, modifying the upstream and downstream conditions and restoring criticality. Thus, the head of the cape exerts hydraulic control on the flow and prevents the jet transport from increasing above its critical level. Inherent in the hydraulic approach is the assumption that alongshore scales are large. For realistic alongshore scales, solutions modified by coastline curvature suggest that the convexity of the head of a cape slightly inhibits the transition to a strongly upwelled downstream state by increasing the required critical transport. In the presence of topographic features with finite alongshore scale, the hydraulic approach can be used to construct a flow field, although this flow field has an inherent error arising from the implicit assumptions regarding scales. Estimation of this error for topography representing Cape Blanco suggests that in places the cape is rather abrupt for hydraulic theory to be valid. Title: The Hydraulics of an Evolving Upwelling Jet Flowing around a Cape Author: Barth, John A., Dale, Andrew C. Upwelling jets flow alongshore in approximate geostrophic balance with the onshore pressure gradient induced by coastal upwelling. Observations of such jets have shown that they often move offshore downstream of capes, leaving a pool of upwelled water inshore. Comparisons are made between this behavior and the hydraulic transition of a potential-vorticity-conserving coastal current as it passes a topographic anomaly at which it is exactly critical to long coastal-trapped waves. An analytic 1.5-layer model of coastal hydraulics with constant potential vorticity in each layer predicts flow fields (i.e., jet separation) in critical situations that resemble observations. When scales approximate Cape Blanco on the Oregon coast, separation occurs at a jet transport of around 0.76 × 10⁶ m³ s−¹, similar to observed transports. Time-dependent, semigeostrophic calculations suggest that, during an upwelling season, the jet would evolve from a weak flow, which was subcritical everywhere and symmetric about the cape, to an exactly critical state that made a transition from subcritical to supercritical structure at the head of the cape. The predicted flow field at critical transition consists of a narrow upwelling jet upstream of the cape that moves offshore and broadens at the cape. This critical state would be accompanied by a downstream jump back to subcritical conditions. Further upwelling-favorable winds would lead to transient waves that propagated upstream and downstream, modifying the upstream and downstream conditions and restoring criticality. Thus, the head of the cape exerts hydraulic control on the flow and prevents the jet transport from increasing above its critical level. Inherent in the hydraulic approach is the assumption that alongshore scales are large. For realistic alongshore scales, solutions modified by coastline curvature suggest that the convexity of the head of a cape slightly inhibits the transition to a strongly upwelled downstream state by increasing the required critical transport. In the presence of topographic features with finite alongshore scale, the hydraulic approach can be used to construct a flow field, although this flow field has an inherent error arising from the implicit assumptions regarding scales. Estimation of this error for topography representing Cape Blanco suggests that in places the cape is rather abrupt for hydraulic theory to be valid. Close

• 2. [Article] Wave-Driven Inner-Shelf Motions on the Oregon Coast*

  Recent work by S. Lentz et al. documents offshore transport in the inner shelf due to a wave-driven return flow associated with the Hasselmann wave stress (the Stokes–Coriolis force). This analysis is ...

  Citation × Citation Citation Abstract Copy Title: Wave-Driven Inner-Shelf Motions on the Oregon Coast* Author: Kirincich, Anthony R., Barth, John A., Lentz, Steven J. Recent work by S. Lentz et al. documents offshore transport in the inner shelf due to a wave-driven return flow associated with the Hasselmann wave stress (the Stokes–Coriolis force). This analysis is extended using observations from the central Oregon coast to identify the wave-driven return flow present and quantify the potential bias of wind-driven across-shelf exchange by unresolved wave-driven circulation. Using acoustic Doppler current profiler (ADCP) measurements at six stations, each in water depths of 13–15 m, observed depth-averaged, across-shelf velocities were generally correlated with theoretical estimates of the proposed return flow. During times of minimal wind forcing, across-shelf velocity profiles were vertically sheared, with stronger velocities near the top of the measured portion of the water column, and increased in magnitude with increasing significant wave height, consistent with circulation due to the Hasselmann wave stress. Yet velocity magnitudes and vertical shears were stronger than that predicted by linear wave theory, and more similar to the stratified ‘‘summer’’ velocity profiles described by S. Lentz et al. Additionally, substantial temporal and spatial variability of the wave-driven return flow was found, potentially due to changing wind and wave conditions as well as local bathymetric variability. Despite the wave-driven circulation found, subtracting estimates of the return flow from the observed across-shelf velocity had no significant effect on estimates of the across-shelf exchange due to along-shelf wind forcing at these water depths along the Oregon coast during summer. Title: Wave-Driven Inner-Shelf Motions on the Oregon Coast* Author: Kirincich, Anthony R., Barth, John A., Lentz, Steven J. Recent work by S. Lentz et al. documents offshore transport in the inner shelf due to a wave-driven return flow associated with the Hasselmann wave stress (the Stokes–Coriolis force). This analysis is extended using observations from the central Oregon coast to identify the wave-driven return flow present and quantify the potential bias of wind-driven across-shelf exchange by unresolved wave-driven circulation. Using acoustic Doppler current profiler (ADCP) measurements at six stations, each in water depths of 13–15 m, observed depth-averaged, across-shelf velocities were generally correlated with theoretical estimates of the proposed return flow. During times of minimal wind forcing, across-shelf velocity profiles were vertically sheared, with stronger velocities near the top of the measured portion of the water column, and increased in magnitude with increasing significant wave height, consistent with circulation due to the Hasselmann wave stress. Yet velocity magnitudes and vertical shears were stronger than that predicted by linear wave theory, and more similar to the stratified ‘‘summer’’ velocity profiles described by S. Lentz et al. Additionally, substantial temporal and spatial variability of the wave-driven return flow was found, potentially due to changing wind and wave conditions as well as local bathymetric variability. Despite the wave-driven circulation found, subtracting estimates of the return flow from the observed across-shelf velocity had no significant effect on estimates of the across-shelf exchange due to along-shelf wind forcing at these water depths along the Oregon coast during summer. Close

• 3. [Article] The Relative Importance of Wind Strength and Along-Shelf Bathymetric Variations on the Separation of a Coastal Upwelling Jet

  A high-resolution numerical model with idealized topography is used to investigate the degree to which a coastal upwelling jet separates from the shelf as it flows around a submarine bank depending on ...

  Citation × Citation Citation Abstract Copy Title: The Relative Importance of Wind Strength and Along-Shelf Bathymetric Variations on the Separation of a Coastal Upwelling Jet Author: Castelao, Renato M., Barth, John A. A high-resolution numerical model with idealized topography is used to investigate the degree to which a coastal upwelling jet separates from the shelf as it flows around a submarine bank depending on the wind strength and the horizontal scale of the bank. Experiments were run using several wind forcing magnitudes and submarine banks with different geometries, so as to explore a wide range of the flow strength as measured by the Rossby number (Ro) and the ratio of the squares of the internal Rossby radius of deformation and curvature of the topography as denoted by the Burger number (Bu). The intensity of the jet separation is strongly dependent on both parameters, with maximum separation with increasing Ro and Bu close to 1, when large amounts of upwelled water are exported toward deeper waters. For small Bu, separation is minimal and independent of Ro. For high Ro, the degree of separation decreases at large Bu since the bank acts only as a small perturbation to the flow. Term balances in the along-shelf momentum equation reveal that the primary balance over the bank is between the nonlinear and the ageostrophic terms. In an asymmetric bank, the radius of curvature in the upstream half of the bank dominates in terms of determining the offshore deflection of a water particle at the surface. The asymmetry increases the cross-isobath transport but not the offshore deflection of the jet. Title: The Relative Importance of Wind Strength and Along-Shelf Bathymetric Variations on the Separation of a Coastal Upwelling Jet Author: Castelao, Renato M., Barth, John A. A high-resolution numerical model with idealized topography is used to investigate the degree to which a coastal upwelling jet separates from the shelf as it flows around a submarine bank depending on the wind strength and the horizontal scale of the bank. Experiments were run using several wind forcing magnitudes and submarine banks with different geometries, so as to explore a wide range of the flow strength as measured by the Rossby number (Ro) and the ratio of the squares of the internal Rossby radius of deformation and curvature of the topography as denoted by the Burger number (Bu). The intensity of the jet separation is strongly dependent on both parameters, with maximum separation with increasing Ro and Bu close to 1, when large amounts of upwelled water are exported toward deeper waters. For small Bu, separation is minimal and independent of Ro. For high Ro, the degree of separation decreases at large Bu since the bank acts only as a small perturbation to the flow. Term balances in the along-shelf momentum equation reveal that the primary balance over the bank is between the nonlinear and the ageostrophic terms. In an asymmetric bank, the radius of curvature in the upstream half of the bank dominates in terms of determining the offshore deflection of a water particle at the surface. The asymmetry increases the cross-isobath transport but not the offshore deflection of the jet. Close

• 4. [Article] Alongshelf Variability of Inner-Shelf Circulation along the Central Oregon Coast during Summer

  The spatial and temporal variability of inner-shelf circulation along the central Oregon coast during the 2004 upwelling season is described using a 70-km-long array of moorings along the 15-m isobath. ...

  Citation × Citation Citation Abstract Copy Title: Alongshelf Variability of Inner-Shelf Circulation along the Central Oregon Coast during Summer Author: Kirincich, Anthony R., Barth, John A. The spatial and temporal variability of inner-shelf circulation along the central Oregon coast during the 2004 upwelling season is described using a 70-km-long array of moorings along the 15-m isobath. Circulation at three stations located onshore of a submarine bank differed from that of a station north of the bank, despite the relatively uniform wind forcing and inner-shelf bathymetry present. During upwelling-favorable winds, strong southward alongshelf flow occurred north of the bank, no alongshelf flow occurred onshore of the northern part of the bank, and increasing southward flow occurred onshore of the southern part of the bank. During downwelling-favorable winds, strong northward flow occurred in the inner shelf onshore of the bank while weak flow occurred north of the bank. These alongshelf differences in inner-shelf circulation were due to the effects of the bank, which isolated the inner shelf onshore of the bank from the regional upwelling circulation that was evident at the northernmost station. As a result, circulation onshore of the bank was driven primarily by local wind forcing, while flow north of the bank was only partially driven by local winds.A secondary mode of variability, attributed to the movement of the regional upwelling jet due to remote forcings, contributed the bulk of the variability observed north of the bank. With the time-dependent wind forcing present, acceleration was an important term in the depth-averaged alongshelf momentum equation at all stations. During upwelling, bottom stress and acceleration opposed the wind stress north of the bank, while bottom stress was weaker onshore of the bank where the across-shelf momentum flux and the alongshelf pressure gradient balanced the residual of the acceleration and stresses. During downwelling, waters onshore of the bank surged northward at magnitudes much larger than that found north of the bank. These spatial variations developed as the season progressed and the regional upwelling circulation intensified, explaining known variations in growth and recruitment of nearshore invertebrate species. Title: Alongshelf Variability of Inner-Shelf Circulation along the Central Oregon Coast during Summer Author: Kirincich, Anthony R., Barth, John A. The spatial and temporal variability of inner-shelf circulation along the central Oregon coast during the 2004 upwelling season is described using a 70-km-long array of moorings along the 15-m isobath. Circulation at three stations located onshore of a submarine bank differed from that of a station north of the bank, despite the relatively uniform wind forcing and inner-shelf bathymetry present. During upwelling-favorable winds, strong southward alongshelf flow occurred north of the bank, no alongshelf flow occurred onshore of the northern part of the bank, and increasing southward flow occurred onshore of the southern part of the bank. During downwelling-favorable winds, strong northward flow occurred in the inner shelf onshore of the bank while weak flow occurred north of the bank. These alongshelf differences in inner-shelf circulation were due to the effects of the bank, which isolated the inner shelf onshore of the bank from the regional upwelling circulation that was evident at the northernmost station. As a result, circulation onshore of the bank was driven primarily by local wind forcing, while flow north of the bank was only partially driven by local winds.A secondary mode of variability, attributed to the movement of the regional upwelling jet due to remote forcings, contributed the bulk of the variability observed north of the bank. With the time-dependent wind forcing present, acceleration was an important term in the depth-averaged alongshelf momentum equation at all stations. During upwelling, bottom stress and acceleration opposed the wind stress north of the bank, while bottom stress was weaker onshore of the bank where the across-shelf momentum flux and the alongshelf pressure gradient balanced the residual of the acceleration and stresses. During downwelling, waters onshore of the bank surged northward at magnitudes much larger than that found north of the bank. These spatial variations developed as the season progressed and the regional upwelling circulation intensified, explaining known variations in growth and recruitment of nearshore invertebrate species. Close

• 5. [Article] Time-dependent, wind-driven flow over a shadow midshelf submarine bank

  copyrighted by American Geophysical Union

  Citation × Citation Citation Abstract Copy Title: Time-dependent, wind-driven flow over a shadow midshelf submarine bank Author: Castelao, R. M., Pierce, S. D., Barth, John A. copyrighted by American Geophysical Union Title: Time-dependent, wind-driven flow over a shadow midshelf submarine bank Author: Castelao, R. M., Pierce, S. D., Barth, John A. copyrighted by American Geophysical Union Close

• 6. [Article] The front on the northern flank of Georges Bank in spring : 1. tidal and subtidal variability

  copyrighted by American Geophysical Union

  Citation × Citation Citation Abstract Copy Title: The front on the northern flank of Georges Bank in spring : 1. tidal and subtidal variability Author: Hebert, Dave, Dale, Andrew C., Barth, John A., Ullman, David S. copyrighted by American Geophysical Union Title: The front on the northern flank of Georges Bank in spring : 1. tidal and subtidal variability Author: Hebert, Dave, Dale, Andrew C., Barth, John A., Ullman, David S. copyrighted by American Geophysical Union Close

• 7. [Article] Chlorophyll enchancement and mixing associated with meanders of the shelf break front in the Mid-Atlantic Bight

  copyrighted by American Geophysical Union

  Citation × Citation Citation Abstract Copy Title: Chlorophyll enchancement and mixing associated with meanders of the shelf break front in the Mid-Atlantic Bight Author: Yoder, J. A., Cornillon, P. C., Barth, John A., Ryan, J. P. copyrighted by American Geophysical Union Title: Chlorophyll enchancement and mixing associated with meanders of the shelf break front in the Mid-Atlantic Bight Author: Yoder, J. A., Cornillon, P. C., Barth, John A., Ryan, J. P. copyrighted by American Geophysical Union Close

• 8. [Article] Short-wavelength instabilities on coastal jets and fronts

  copyrighted by American Geophysical Union

  Citation × Citation Citation Abstract Copy Title: Short-wavelength instabilities on coastal jets and fronts Author: Barth, John A. copyrighted by American Geophysical Union Title: Short-wavelength instabilities on coastal jets and fronts Author: Barth, John A. copyrighted by American Geophysical Union Close

• 9. [Article] Coastal ocean response to summer upwelling favorable winds in a region of alongshore bottom topography variations off Oregon

  copyrighted by American Geophysical Union

  Citation × Citation Citation Abstract Copy Title: Coastal ocean response to summer upwelling favorable winds in a region of alongshore bottom topography variations off Oregon Author: Castelao, Renato M., Barth, John A. copyrighted by American Geophysical Union Title: Coastal ocean response to summer upwelling favorable winds in a region of alongshore bottom topography variations off Oregon Author: Castelao, Renato M., Barth, John A. copyrighted by American Geophysical Union Close

• 10. [Article] The nature of the cold filaments in the California current system

  Data from the Coastal Transition Zone (CTZ) experiment are used to describe the velocity fields and water properties associate with cold filaments in the California Current. Combined with previous field ...

  Citation × Citation Citation Abstract Copy Title: The nature of the cold filaments in the California current system Author: Mackas, D. L., Swenson, M., Chavez, F., James, C., Batteen, M., Strub, P. Ted, Kadko, D., Abbott, Mark R., Hayward, T., Dewey, R., Ramp, S., Brink, K. H., Niiler, Pearn P., Huyer, Adriana, 1945-, Kosro, P. Michael, 1951-, Haidvogel, D., Barber, R., Haney, R., Walstad, L., Hood, R. R., Barth, John A., Washburn, L. A. Data from the Coastal Transition Zone (CTZ) experiment are used to describe the velocity fields and water properties associate with cold filaments in the California Current. Combined with previous field surveys and satellite imagery, these show seasonal variability with maximum dynamic height ranges and velocities in summer and minimum values in late winter and early spring. North of Point Arenda (between 39ºN and 42ºN) in spring–summer the flow field on the outer edge of the cold water has the character of a meandering jet, carrying fresh, nutrient-poor water from farther north on its offshore side and cold, salty, nutrient-rich water on its inshore side. At Point Arena in midsummer, the jet often flows offshore and continues south without meandering back onshore as strongly as it does farther north. The flow field south of Point Arena in summer takes on more of the character of a field of mesoscale eddies, although the meandering jet from the north continues to be identifiable. The conceptual model for the May–July period between 36ºN and 42ºN is thus of a surface jet that meanders through and interacts with a field of eddies; the eddies are more dominant south of 39ºN, where the jet broadens and where multiple jets and filaments are often present. At the surface, the jet often separates biological communities and may appear as a barrier to cross-jet transport, especially north of Point Arena early in the season (March–May) However, phytoplankton pigment and nutrients are carried on the inshore flank of the jet, and pigment maxima are sometimes found in the core of the jet. The biological effect of the jet is to define a convoluted, 100 to 400-km-wide region next to the coast, within which much of the richer water is contained, and also to carry some of that richer water offshore in meanders along the outer edge of that region. Title: The nature of the cold filaments in the California current system Author: Mackas, D. L., Swenson, M., Chavez, F., James, C., Batteen, M., Strub, P. Ted, Kadko, D., Abbott, Mark R., Hayward, T., Dewey, R., Ramp, S., Brink, K. H., Niiler, Pearn P., Huyer, Adriana, 1945-, Kosro, P. Michael, 1951-, Haidvogel, D., Barber, R., Haney, R., Walstad, L., Hood, R. R., Barth, John A., Washburn, L. A. Data from the Coastal Transition Zone (CTZ) experiment are used to describe the velocity fields and water properties associate with cold filaments in the California Current. Combined with previous field surveys and satellite imagery, these show seasonal variability with maximum dynamic height ranges and velocities in summer and minimum values in late winter and early spring. North of Point Arenda (between 39ºN and 42ºN) in spring–summer the flow field on the outer edge of the cold water has the character of a meandering jet, carrying fresh, nutrient-poor water from farther north on its offshore side and cold, salty, nutrient-rich water on its inshore side. At Point Arena in midsummer, the jet often flows offshore and continues south without meandering back onshore as strongly as it does farther north. The flow field south of Point Arena in summer takes on more of the character of a field of mesoscale eddies, although the meandering jet from the north continues to be identifiable. The conceptual model for the May–July period between 36ºN and 42ºN is thus of a surface jet that meanders through and interacts with a field of eddies; the eddies are more dominant south of 39ºN, where the jet broadens and where multiple jets and filaments are often present. At the surface, the jet often separates biological communities and may appear as a barrier to cross-jet transport, especially north of Point Arena early in the season (March–May) However, phytoplankton pigment and nutrients are carried on the inshore flank of the jet, and pigment maxima are sometimes found in the core of the jet. The biological effect of the jet is to define a convoluted, 100 to 400-km-wide region next to the coast, within which much of the richer water is contained, and also to carry some of that richer water offshore in meanders along the outer edge of that region. Close