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• 1. [Article] Iron, nutrient, and phytoplankton distributions in Oregon coastal waters

  Copyrighted by American Geophysical Union.

  Citation × Citation Citation Abstract Copy Title: Iron, nutrient, and phytoplankton distributions in Oregon coastal waters Author: Wheeler, Patricia A., Chase, Zanna, Marra, John, van Geen, Alexander, Kosro, P. Michael, 1951- Copyrighted by American Geophysical Union. Title: Iron, nutrient, and phytoplankton distributions in Oregon coastal waters Author: Wheeler, Patricia A., Chase, Zanna, Marra, John, van Geen, Alexander, Kosro, P. Michael, 1951- Copyrighted by American Geophysical Union. Close

• 2. [Article] CTD and velocity surveys of seaward jets off Northern California, July 1981 and 1982

  Two mesoscale surveys were conducted (in July 1981 and July 1982) near Point Arena, California, to determine the structure and circulation associated with tongues of cold surface water extending seaward from ...

  Citation × Citation Citation Abstract Copy Title: CTD and velocity surveys of seaward jets off Northern California, July 1981 and 1982 Author: Huyer, Adriana, 1945-, Kosro, P. Michael, 1951- Two mesoscale surveys were conducted (in July 1981 and July 1982) near Point Arena, California, to determine the structure and circulation associated with tongues of cold surface water extending seaward from the coastal zone. Both surveys were designed at sea on the basis of available satellite IR data, and each was completed in less than a week. Sampling extended 100 km alongshore and 150 km (1981) to 250 km (1982) offshore, and included conductivity, temperature, and depth casts to 500 dbar, and continuous ocean current profiling to 150 m by means of a Doppler acoustic log. Both surveys showed that the tongues of cold water seen in the satellite images were the surface manifestation of hydrographic and current anomalies that extended to a depth of at least 100 m. In each case, strong seaward flow was observed along the northern edge of the cold tongue, which also marked a shallow water mass boundary between low-salinity (< 32.8 ppt) surface waters to the north and high-salinity (> 33.2 ppt) waters to the south. The seaward jets were very strong (up to 80 cm/s) and narrow (30 km), with strong shears (up to 10- 2 S- 1 in the vertical and up to 10^(-4)/s in the horizontal). They were largely geostrophic, had transports exceeding 1.5 sverdrups, and can persist for 2-3 weeks. The seaward jets seemed to be continuous with southward flowing alongshore coastal jets. There is evidence that the seaward jets are recurrent features in the vicinity of Point Arena. Title: CTD and velocity surveys of seaward jets off Northern California, July 1981 and 1982 Author: Huyer, Adriana, 1945-, Kosro, P. Michael, 1951- Two mesoscale surveys were conducted (in July 1981 and July 1982) near Point Arena, California, to determine the structure and circulation associated with tongues of cold surface water extending seaward from the coastal zone. Both surveys were designed at sea on the basis of available satellite IR data, and each was completed in less than a week. Sampling extended 100 km alongshore and 150 km (1981) to 250 km (1982) offshore, and included conductivity, temperature, and depth casts to 500 dbar, and continuous ocean current profiling to 150 m by means of a Doppler acoustic log. Both surveys showed that the tongues of cold water seen in the satellite images were the surface manifestation of hydrographic and current anomalies that extended to a depth of at least 100 m. In each case, strong seaward flow was observed along the northern edge of the cold tongue, which also marked a shallow water mass boundary between low-salinity (< 32.8 ppt) surface waters to the north and high-salinity (> 33.2 ppt) waters to the south. The seaward jets were very strong (up to 80 cm/s) and narrow (30 km), with strong shears (up to 10- 2 S- 1 in the vertical and up to 10^(-4)/s in the horizontal). They were largely geostrophic, had transports exceeding 1.5 sverdrups, and can persist for 2-3 weeks. The seaward jets seemed to be continuous with southward flowing alongshore coastal jets. There is evidence that the seaward jets are recurrent features in the vicinity of Point Arena. Close

• 3. [Article] Horizontal transport and the distribution of nutrients in the coastal transition zone off Northern California: effects on primary production, phytoplankton biomass and species composition

  Conductivity-temperature-depth surveys during 1988 encountered strong baroclinic jets that were evident in acoustic Doppler current profiler and hydrographic data. During June and July 1988 a filament ...

  Citation × Citation Citation Abstract Copy Title: Horizontal transport and the distribution of nutrients in the coastal transition zone off Northern California: effects on primary production, phytoplankton biomass and species composition Author: Stanton, Timothy P., Kosro, P. Michael, 1951-, Ramp, Steven R., Rojas de Mendiola, Blanca, Huyer, Adriana, 1945-, Chavez, Francisco P., Barber, Richard T. Conductivity-temperature-depth surveys during 1988 encountered strong baroclinic jets that were evident in acoustic Doppler current profiler and hydrographic data. During June and July 1988 a filament with high surface nitrate, high chlorophyll, abundant populations of neritic centric diatoms, and higher rates of primary production was evident perpendicular to the coast between Point Arena and Point Reyes. However, the high-nutrient and phytoplankton regions were not in the baroclinic jets but were south and inshore of them. Surface water transported offshore by the strong baroclinic jets was found to have relatively low nutrient content, suggesting that the jets themselves do not carry significant levels of coastally upwelled, high-nutrient water to the ocean interior. The low nutrient and salinity content of the jet suggests that the water originated several hundred kilometers upstream. Although the jets themselves do not appear to transport significant levels of nutrients directly from the coastal regime to the oceanic regime, dynamic processes associated with a meandering jet are likely responsible for high surface nutrients found several hundred kilometers offshore. Processes such as upwelling along the southern edge of the seaward jet result in significant enrichment of the coastal transition zone and in large blooms of neritic diatoms. During 1988 the high-nutrient, high-phytoplankton filament was present when the survey sequence began but then decayed after a month. The surface and subsurface nitrate fields were coherent with the dynamic topography field throughout the survey sequence; however, the surface and integrated chlorophyll fields were coherent only through the first two surveys. A decrease in phytoplankton biomass began during the third survey coincident with physical changes which occurred in that time frame: (1) an intensification of the undercurrent and (2) changes in the surface circulation from predominantly offshore to predominantly alongshore. Understanding the processes responsible for the uncoupling between biology and physics is paramount for realistic biological models of this region. Title: Horizontal transport and the distribution of nutrients in the coastal transition zone off Northern California: effects on primary production, phytoplankton biomass and species composition Author: Stanton, Timothy P., Kosro, P. Michael, 1951-, Ramp, Steven R., Rojas de Mendiola, Blanca, Huyer, Adriana, 1945-, Chavez, Francisco P., Barber, Richard T. Conductivity-temperature-depth surveys during 1988 encountered strong baroclinic jets that were evident in acoustic Doppler current profiler and hydrographic data. During June and July 1988 a filament with high surface nitrate, high chlorophyll, abundant populations of neritic centric diatoms, and higher rates of primary production was evident perpendicular to the coast between Point Arena and Point Reyes. However, the high-nutrient and phytoplankton regions were not in the baroclinic jets but were south and inshore of them. Surface water transported offshore by the strong baroclinic jets was found to have relatively low nutrient content, suggesting that the jets themselves do not carry significant levels of coastally upwelled, high-nutrient water to the ocean interior. The low nutrient and salinity content of the jet suggests that the water originated several hundred kilometers upstream. Although the jets themselves do not appear to transport significant levels of nutrients directly from the coastal regime to the oceanic regime, dynamic processes associated with a meandering jet are likely responsible for high surface nutrients found several hundred kilometers offshore. Processes such as upwelling along the southern edge of the seaward jet result in significant enrichment of the coastal transition zone and in large blooms of neritic diatoms. During 1988 the high-nutrient, high-phytoplankton filament was present when the survey sequence began but then decayed after a month. The surface and subsurface nitrate fields were coherent with the dynamic topography field throughout the survey sequence; however, the surface and integrated chlorophyll fields were coherent only through the first two surveys. A decrease in phytoplankton biomass began during the third survey coincident with physical changes which occurred in that time frame: (1) an intensification of the undercurrent and (2) changes in the surface circulation from predominantly offshore to predominantly alongshore. Understanding the processes responsible for the uncoupling between biology and physics is paramount for realistic biological models of this region. Close

• 4. [Article] Evaluation of a coastal ocean circulation model for the Columbia River plume in summer 2004

  copyrighted by American Geophysical Union

  Citation × Citation Citation Abstract Copy Title: Evaluation of a coastal ocean circulation model for the Columbia River plume in summer 2004 Author: Banas, Neil S., Hickey, Barbara M., MacCready, Parker, Liu, Yonggang, Dever, Edward P., Kosro, P. Michael, 1951- copyrighted by American Geophysical Union Title: Evaluation of a coastal ocean circulation model for the Columbia River plume in summer 2004 Author: Banas, Neil S., Hickey, Barbara M., MacCready, Parker, Liu, Yonggang, Dever, Edward P., Kosro, P. Michael, 1951- copyrighted by American Geophysical Union Close

• 5. [Article] Offshore wind forcing in the Gulf of Tehuantepec, Mexico: the asymmetric circulation

  Since the early surveys carried out by the Eastern Tropical Pacific (EASTROPIC) and Scripps Tuna Oceanographic Research (STOR) projects in the tropical Pacific off Mexico, the northerly winds which blow ...

  Citation × Citation Citation Abstract Copy Title: Offshore wind forcing in the Gulf of Tehuantepec, Mexico: the asymmetric circulation Author: Velez, H.S., Kosro, P. Michael, 1951-, Brown, J., Smith, Robert L. (Robert Lloyd), 1935-, Barton, E.D., Trasvina, A. Since the early surveys carried out by the Eastern Tropical Pacific (EASTROPIC) and Scripps Tuna Oceanographic Research (STOR) projects in the tropical Pacific off Mexico, the northerly winds which blow over the Gulf of Tehuantepec were described as an Important factor controlling the dynamics of this coastal ocean. In January-February 1989 an international team carried out the experiment Tehuano, designed to study the response of the gulf to these wind pulses. The complete evolution of the coastal ocean after an event of moderate intensity was observed. The forcing is characterized by a mostly symmetric, fanshaped, offshore wind jet, which in turn produces a remarkably asymmetric upper ocean response. While analytical results based on Ekman theory forced by a symmetric offshore wind predict the formation of a symmetric dipolar circulation, the observed flow consists mainly of a large (200 km in diameter) anticyclonic warm-core eddy in the western gulf, with only a weak cyclonic counterpart in the eastern gulf. Intense surface cooling under the wind jet is caused by entrainment of subsurface water into the upper layer. The thermocline in the west deepens with the development of the eddy, which is formed initially by the advection of warm surface waters from west of the gulf. East of the axis of the wind, the mixed layer deepens due to wind-induced entrainment, while, at the same time, shoaling and compression of the deeper isotherms by curl-induced upwelling (Ekman pumping) strengthen the thermocline. Title: Offshore wind forcing in the Gulf of Tehuantepec, Mexico: the asymmetric circulation Author: Velez, H.S., Kosro, P. Michael, 1951-, Brown, J., Smith, Robert L. (Robert Lloyd), 1935-, Barton, E.D., Trasvina, A. Since the early surveys carried out by the Eastern Tropical Pacific (EASTROPIC) and Scripps Tuna Oceanographic Research (STOR) projects in the tropical Pacific off Mexico, the northerly winds which blow over the Gulf of Tehuantepec were described as an Important factor controlling the dynamics of this coastal ocean. In January-February 1989 an international team carried out the experiment Tehuano, designed to study the response of the gulf to these wind pulses. The complete evolution of the coastal ocean after an event of moderate intensity was observed. The forcing is characterized by a mostly symmetric, fanshaped, offshore wind jet, which in turn produces a remarkably asymmetric upper ocean response. While analytical results based on Ekman theory forced by a symmetric offshore wind predict the formation of a symmetric dipolar circulation, the observed flow consists mainly of a large (200 km in diameter) anticyclonic warm-core eddy in the western gulf, with only a weak cyclonic counterpart in the eastern gulf. Intense surface cooling under the wind jet is caused by entrainment of subsurface water into the upper layer. The thermocline in the west deepens with the development of the eddy, which is formed initially by the advection of warm surface waters from west of the gulf. East of the axis of the wind, the mixed layer deepens due to wind-induced entrainment, while, at the same time, shoaling and compression of the deeper isotherms by curl-induced upwelling (Ekman pumping) strengthen the thermocline. Close

• 6. [Article] Mesoscale surveys over the shelf and slope in the upwelling region near Point Arena, California

  Repeated mesoscale surveys of a 40-km-wide, 100-km-long, coastal region near Point Arena, California, were conducted during the upwelling season (April-August) in 1981 and 1982. Each survey included conventional ...

  Citation × Citation Citation Abstract Copy Title: Mesoscale surveys over the shelf and slope in the upwelling region near Point Arena, California Author: Huyer, Adriana, 1945-, Kosro, P. Michael, 1951- Repeated mesoscale surveys of a 40-km-wide, 100-km-long, coastal region near Point Arena, California, were conducted during the upwelling season (April-August) in 1981 and 1982. Each survey included conventional conductivity-temperature-depth casts at standard locations over the continental shelf and slope between 38°N and 39°10'N, and continuous operation of a Doppler acoustic log to obtain velocity profiles in the 20- to 150-m depth range. "Synoptic" surveys covered the entire grid in 2-3 days. Winds were strongly favorable for upwelling during the three 1981 surveys and were weak or variable during the three 1982 surveys. Surface temperature and salinity fields reflect the influence of both the seasonal winds and day-to-day variations in the wind. Persistently low surface salinities offshore reflect the general southward advection of subarctic waters, and sporadic low salinities over the inner shelf reflect northward advection of local runoff through an intermittent narrow countercurrent along the coast. Circulation patterns during all but one of the surveys were very complex and included meandering equatorward flow, cyclonic and anticyclonic eddies, and inshore countercurrents. The simple two-dimensional, equatorward, baroclinic coastal jet usually associated with coastal upwelling was observed during only one of our surveys. Overall average fields are relatively simple. They show broad equatorward surface flow, a very weak inshore countercurrent, and a definite poleward undercurrent at the shelf break. Average temperature, salinity, and density fields are generally congruent with the average flow pattern. Average isotherms and isohalines are not strictly parallel to the coastline: south of the coastline bend at Point Arena, they diverge gradually from the coast. Comparison of average sections calculated from 10 matched pairs of Central and Arena lines (separated by 50 km) shows there are systematic differences between them. Warmer, fresher waters lie nearer shore (and in shallower water) off Point Arena than on the Central line; this suggests that the surface waters flowing past Point Arena have sufficient southward momentum to cross isobaths. Comparison of average velocity sections on these two lines shows some differences in structure; since the variability is large, these may not be significant. Comparison of the measured and geostrophic average shears suggests there is a significant ageostrophic component in the upper layers above 40 m; it may be the signature of an average wind-driven Ekman spira Title: Mesoscale surveys over the shelf and slope in the upwelling region near Point Arena, California Author: Huyer, Adriana, 1945-, Kosro, P. Michael, 1951- Repeated mesoscale surveys of a 40-km-wide, 100-km-long, coastal region near Point Arena, California, were conducted during the upwelling season (April-August) in 1981 and 1982. Each survey included conventional conductivity-temperature-depth casts at standard locations over the continental shelf and slope between 38°N and 39°10'N, and continuous operation of a Doppler acoustic log to obtain velocity profiles in the 20- to 150-m depth range. "Synoptic" surveys covered the entire grid in 2-3 days. Winds were strongly favorable for upwelling during the three 1981 surveys and were weak or variable during the three 1982 surveys. Surface temperature and salinity fields reflect the influence of both the seasonal winds and day-to-day variations in the wind. Persistently low surface salinities offshore reflect the general southward advection of subarctic waters, and sporadic low salinities over the inner shelf reflect northward advection of local runoff through an intermittent narrow countercurrent along the coast. Circulation patterns during all but one of the surveys were very complex and included meandering equatorward flow, cyclonic and anticyclonic eddies, and inshore countercurrents. The simple two-dimensional, equatorward, baroclinic coastal jet usually associated with coastal upwelling was observed during only one of our surveys. Overall average fields are relatively simple. They show broad equatorward surface flow, a very weak inshore countercurrent, and a definite poleward undercurrent at the shelf break. Average temperature, salinity, and density fields are generally congruent with the average flow pattern. Average isotherms and isohalines are not strictly parallel to the coastline: south of the coastline bend at Point Arena, they diverge gradually from the coast. Comparison of average sections calculated from 10 matched pairs of Central and Arena lines (separated by 50 km) shows there are systematic differences between them. Warmer, fresher waters lie nearer shore (and in shallower water) off Point Arena than on the Central line; this suggests that the surface waters flowing past Point Arena have sufficient southward momentum to cross isobaths. Comparison of average velocity sections on these two lines shows some differences in structure; since the variability is large, these may not be significant. Comparison of the measured and geostrophic average shears suggests there is a significant ageostrophic component in the upper layers above 40 m; it may be the signature of an average wind-driven Ekman spira Close

• 7. [Article] Surface patterns in temperature, flow, phytoplankton biomass, and species composition in the coastal transition zone of northern California

  Satellite thermal imagery and in situ biological and physical data are presented that describe the spatial variability of phytoplankton biomass and species composition in relation to the physical structure ...

  Citation × Citation Citation Abstract Copy Title: Surface patterns in temperature, flow, phytoplankton biomass, and species composition in the coastal transition zone of northern California Author: Abbott, Mark R., Hood, Raleigh R., Huyer, Adriana, 1945-, Kosro, P. Michael, 1951- Satellite thermal imagery and in situ biological and physical data are presented that describe the spatial variability of phytoplankton biomass and species composition in relation to the physical structure at the sea surface during persistent upwelling off northern California. Surface patterns in temperature, geostrophic velocity, chlorophyll, and particle size structure show that the coastal zone was dominated by two water masses separated by a well-defined physical boundary. This boundary is apparent in satellite thermal imagery as a cold front and in dynamic height as a meandering jet in the California Current. On the landward side of the front (jet) we observed cold, coastal water that was relatively enriched in phytoplankton biomass, due to the presence of large diatoms. On the seaward side of the front (jet) we observed relatively warm water where the phytoplankton biomass was low and the diatoms were largely absent. Broad tongues and narrow filaments of cold, chlorophyll-rich water that extended over 100 km offshore were present in our study area. These features were bounded by the meandering coastal jet. The coldest, most chlorophyll-rich water in these tongues and filaments was located between the onshore and offshore flows in relatively slow moving water, but entrainment of coastal water into the jet was apparent. Title: Surface patterns in temperature, flow, phytoplankton biomass, and species composition in the coastal transition zone of northern California Author: Abbott, Mark R., Hood, Raleigh R., Huyer, Adriana, 1945-, Kosro, P. Michael, 1951- Satellite thermal imagery and in situ biological and physical data are presented that describe the spatial variability of phytoplankton biomass and species composition in relation to the physical structure at the sea surface during persistent upwelling off northern California. Surface patterns in temperature, geostrophic velocity, chlorophyll, and particle size structure show that the coastal zone was dominated by two water masses separated by a well-defined physical boundary. This boundary is apparent in satellite thermal imagery as a cold front and in dynamic height as a meandering jet in the California Current. On the landward side of the front (jet) we observed cold, coastal water that was relatively enriched in phytoplankton biomass, due to the presence of large diatoms. On the seaward side of the front (jet) we observed relatively warm water where the phytoplankton biomass was low and the diatoms were largely absent. Broad tongues and narrow filaments of cold, chlorophyll-rich water that extended over 100 km offshore were present in our study area. These features were bounded by the meandering coastal jet. The coldest, most chlorophyll-rich water in these tongues and filaments was located between the onshore and offshore flows in relatively slow moving water, but entrainment of coastal water into the jet was apparent. Close

• 8. [Article] Physical versus biological spring transition: 2005

  In 2005, the onset of spring conditions in the physics of the coastal ocean (lowered sea level, spin-up of vertically-sheared equatorward coastal jet) came about 50 days later than average off Newport ...

  Citation × Citation Citation Abstract Copy Title: Physical versus biological spring transition: 2005 Author: Shearman, R. Kipp, Hickey, Barbara M., Pierce, Stephen D., Peterson, William T., Kosro, P. Michael, 1951- In 2005, the onset of spring conditions in the physics of the coastal ocean (lowered sea level, spin-up of vertically-sheared equatorward coastal jet) came about 50 days later than average off Newport Oregon, on May 24. There was a further delay of 50 days before the subsurface upwelled water penetrated into the anomalously stratified surface layer, becoming most available for biological activity. The warm anomaly in sea surface temperature which provided the surface cap was observed at mid-shelf locations from Washington to central California, but it ended sooner south of Oregon. Biological impacts of these delays to several trophic levels have been reported. Title: Physical versus biological spring transition: 2005 Author: Shearman, R. Kipp, Hickey, Barbara M., Pierce, Stephen D., Peterson, William T., Kosro, P. Michael, 1951- In 2005, the onset of spring conditions in the physics of the coastal ocean (lowered sea level, spin-up of vertically-sheared equatorward coastal jet) came about 50 days later than average off Newport Oregon, on May 24. There was a further delay of 50 days before the subsurface upwelled water penetrated into the anomalously stratified surface layer, becoming most available for biological activity. The warm anomaly in sea surface temperature which provided the surface cap was observed at mid-shelf locations from Washington to central California, but it ended sooner south of Oregon. Biological impacts of these delays to several trophic levels have been reported. Close

• 9. [Article] Water mass subduction and the transport of phytoplankton in a coastal upwelling system

  Observations during the Coastal Transition Zone (CTZ) experiment in summer 1988 reveal the presence of deep phytoplankton layers in a coastal upwelling system. The layers occur throughout the CTZ study ...

  Citation × Citation Citation Abstract Copy Title: Water mass subduction and the transport of phytoplankton in a coastal upwelling system Author: Washburn, Libe, Hayward, Thomas, Kadko, David C., Ramp, Steve, Cowles, Timothy, Kosro, P. Michael, 1951-, Stanton, Timothy P., Jones, Burton H. Observations during the Coastal Transition Zone (CTZ) experiment in summer 1988 reveal the presence of deep phytoplankton layers in a coastal upwelling system. The layers occur throughout the CTZ study area, including a strong baroclinic jet which was present over the period of the experiment. On the basis of a variety of bio-optical, hydrographic, and geochemical indicators, it is concluded that the water masses associated with the layers result from subduction processes. Criteria are developed for identification of subducted water masses based on the beam attenuation coefficient, chlorophyll fluorescence, and distribution of light in the water column. Temperature-salinity characteristics are consistent with two source regions for the subducted layers, one nearshore and a second farther offshore. Most of the layers correspond to the inshore source which is apparently distributed alongshore. Subducted water masses are found in all six grid surveys of the CTZ experiment and probably result from a variety of physical processes. One of these is flow along sloping isopycnal surfaces due to advection and mixing processes. Advection time scales for flow out the axis of the jet range from a few days to a few weeks, depending on the depth of a particular surface, and the bio-optical indicators for subduction processes persist over these time scales Title: Water mass subduction and the transport of phytoplankton in a coastal upwelling system Author: Washburn, Libe, Hayward, Thomas, Kadko, David C., Ramp, Steve, Cowles, Timothy, Kosro, P. Michael, 1951-, Stanton, Timothy P., Jones, Burton H. Observations during the Coastal Transition Zone (CTZ) experiment in summer 1988 reveal the presence of deep phytoplankton layers in a coastal upwelling system. The layers occur throughout the CTZ study area, including a strong baroclinic jet which was present over the period of the experiment. On the basis of a variety of bio-optical, hydrographic, and geochemical indicators, it is concluded that the water masses associated with the layers result from subduction processes. Criteria are developed for identification of subducted water masses based on the beam attenuation coefficient, chlorophyll fluorescence, and distribution of light in the water column. Temperature-salinity characteristics are consistent with two source regions for the subducted layers, one nearshore and a second farther offshore. Most of the layers correspond to the inshore source which is apparently distributed alongshore. Subducted water masses are found in all six grid surveys of the CTZ experiment and probably result from a variety of physical processes. One of these is flow along sloping isopycnal surfaces due to advection and mixing processes. Advection time scales for flow out the axis of the jet range from a few days to a few weeks, depending on the depth of a particular surface, and the bio-optical indicators for subduction processes persist over these time scales Close

• 10. [Article] Structure of the coastal current field off Northern California during the coastal ocean dynamics experiment

  For 74 days during the spring and summer upwelling seasons of 1981 and 1982, in conjunction with the Coastal Ocean Dynamics Experiment, profiles of upper ocean currents were collected in the waters over ...

  Citation × Citation Citation Abstract Copy Title: Structure of the coastal current field off Northern California during the coastal ocean dynamics experiment Author: Kosro, P. Michael, 1951- For 74 days during the spring and summer upwelling seasons of 1981 and 1982, in conjunction with the Coastal Ocean Dynamics Experiment, profiles of upper ocean currents were collected in the waters over the shelf and slope off northern California using a shipboard Doppler acoustic log. These measurements provide detailed information on the spatial structure of the current field. Synoptic maps of near-surface currents often deviate substantially from classical two-dimensional wind-driven upwelling and indicate a close association between the complex temperature structures observed in satellite imagery and the presence of vigorous current structures including squirts (regions of intense seaward flow), eddies, and countercurrents. Well-defined examples of a squirt and of a countercurrent during a cessation of wind forcing (wind relaxation event) are examined in detail. Despite this complexity, the nearshore synoptic current field was found to be anisotropic, varying more rapidly cross shore than alongshore. The structure of the current averages and simple fluctuation statistics were largely as deduced in other upwelling areas from moored measurements. A surface-intensified equatorward jet was found in the average alongshore currents, with vertical shear exceeding -2 x 10^(-3) s^(-1) over much of the shelf. The core of the jet moved offshore south of Point Arena and was better resolved in along-isobath averages. At depths below 80 m the average alongshore flow reversed, giving way to a poleward undercurrent, strongest near the shelf break. The detailed structure of the inferred cross-shore circulation was found to be sensitive to the coordinate system selected. Using nominal (along-coast) coordinates, the average cross-shore current was found to be directed offshore within a surface layer which deepened with distance from the coast out to the shelf break, showed strong vertical shear only near the surface, and was divergent in the upper water column and convergent in the lower water column over the shelf. Current fluctuations about the local mean were strongly polarized along isobaths near the coast and became largely isotropic far from shore except offshore from Point Arena, where squirts were recurrently observed. Title: Structure of the coastal current field off Northern California during the coastal ocean dynamics experiment Author: Kosro, P. Michael, 1951- For 74 days during the spring and summer upwelling seasons of 1981 and 1982, in conjunction with the Coastal Ocean Dynamics Experiment, profiles of upper ocean currents were collected in the waters over the shelf and slope off northern California using a shipboard Doppler acoustic log. These measurements provide detailed information on the spatial structure of the current field. Synoptic maps of near-surface currents often deviate substantially from classical two-dimensional wind-driven upwelling and indicate a close association between the complex temperature structures observed in satellite imagery and the presence of vigorous current structures including squirts (regions of intense seaward flow), eddies, and countercurrents. Well-defined examples of a squirt and of a countercurrent during a cessation of wind forcing (wind relaxation event) are examined in detail. Despite this complexity, the nearshore synoptic current field was found to be anisotropic, varying more rapidly cross shore than alongshore. The structure of the current averages and simple fluctuation statistics were largely as deduced in other upwelling areas from moored measurements. A surface-intensified equatorward jet was found in the average alongshore currents, with vertical shear exceeding -2 x 10^(-3) s^(-1) over much of the shelf. The core of the jet moved offshore south of Point Arena and was better resolved in along-isobath averages. At depths below 80 m the average alongshore flow reversed, giving way to a poleward undercurrent, strongest near the shelf break. The detailed structure of the inferred cross-shore circulation was found to be sensitive to the coordinate system selected. Using nominal (along-coast) coordinates, the average cross-shore current was found to be directed offshore within a surface layer which deepened with distance from the coast out to the shelf break, showed strong vertical shear only near the surface, and was divergent in the upper water column and convergent in the lower water column over the shelf. Current fluctuations about the local mean were strongly polarized along isobaths near the coast and became largely isotropic far from shore except offshore from Point Arena, where squirts were recurrently observed. Close

• 11. [Article] The structure of the transition zone between coastal waters and the open ocean off northern California, winter and spring 1987

  Physical and biological fields in the coastal transition zone off northern California were measured during February, March, May and June 1987 in an extended alongshore region between 60 km and 150 km offshore. ...

  Citation × Citation Citation Abstract Copy Title: The structure of the transition zone between coastal waters and the open ocean off northern California, winter and spring 1987 Author: Chavez, F. P., Barber, R. T., Strub, P. Ted, Smith, Robert L. (Robert Lloyd), 1935-, Abbott, Mark R., Cowles, Timothy J., Jessen, P., Ramp, S. R., Huyer, Adriana, 1945-, Kosro, P. Michael, 1951-, Small, Lawrence F. Physical and biological fields in the coastal transition zone off northern California were measured during February, March, May and June 1987 in an extended alongshore region between 60 km and 150 km offshore. The spring transition, as seen in coastal sea level and winds, occurred in mid-March. Surface variability during the two spring cruises was stronger and of larger scale than that seen during the two winter cruises. An equatorward-tending current, flowing along the boundary between low steric sea level inshore and high steric sea level offshore, dominated both the directly-measured (acoustic Doppler current profiler) and geostrophic current fields during spring. Current jets of comparable strength directed both offshore and onshore were seen off Cape Mendocino and Point Arena; these evolved significantly in the 3 weeks between cruises. Inshore of the current, properties associated with upwelled water were found near the surface, including low temperature and high salinity, nutrients and chlorophyll; offshore of the current, waters were warmer, less saline, lower in nutrients and more oligotrophic. Geostrophic and directly measured volume transports in the current were about 2–3 Sv. Isopycnals inshore of the spring upwelling front were displaced vertically by O(40–80 m) from their depths during the winter survey; these displacements extended deep into the water column and were largely independent of depth between 100 and 400 m. Surface mixed layers tended to be deep in winter and shallower inshore of the upwelling front in spring. A connection between the equatorward-tending frontal jet off northern California and the more well-studied California Current further south is suggested by the similarity of their transports and of their dynamic height values. Title: The structure of the transition zone between coastal waters and the open ocean off northern California, winter and spring 1987 Author: Chavez, F. P., Barber, R. T., Strub, P. Ted, Smith, Robert L. (Robert Lloyd), 1935-, Abbott, Mark R., Cowles, Timothy J., Jessen, P., Ramp, S. R., Huyer, Adriana, 1945-, Kosro, P. Michael, 1951-, Small, Lawrence F. Physical and biological fields in the coastal transition zone off northern California were measured during February, March, May and June 1987 in an extended alongshore region between 60 km and 150 km offshore. The spring transition, as seen in coastal sea level and winds, occurred in mid-March. Surface variability during the two spring cruises was stronger and of larger scale than that seen during the two winter cruises. An equatorward-tending current, flowing along the boundary between low steric sea level inshore and high steric sea level offshore, dominated both the directly-measured (acoustic Doppler current profiler) and geostrophic current fields during spring. Current jets of comparable strength directed both offshore and onshore were seen off Cape Mendocino and Point Arena; these evolved significantly in the 3 weeks between cruises. Inshore of the current, properties associated with upwelled water were found near the surface, including low temperature and high salinity, nutrients and chlorophyll; offshore of the current, waters were warmer, less saline, lower in nutrients and more oligotrophic. Geostrophic and directly measured volume transports in the current were about 2–3 Sv. Isopycnals inshore of the spring upwelling front were displaced vertically by O(40–80 m) from their depths during the winter survey; these displacements extended deep into the water column and were largely independent of depth between 100 and 400 m. Surface mixed layers tended to be deep in winter and shallower inshore of the upwelling front in spring. A connection between the equatorward-tending frontal jet off northern California and the more well-studied California Current further south is suggested by the similarity of their transports and of their dynamic height values. Close

• 12. [Article] Upper ocean thermohaline fields near 2°S, 156°E, during the Tropical Ocean-Global Atmosphere - Coupled Ocean-Atmosphere Response Experiment, November 1992 to February 1993

  Zonal and meridional Seasoar sections centered at 1°50’S, 156°06’E were repeated >30 times in three 20-day periods between November 13, 1992, and February 15, 1993. Both sections were 130 km long, and ...

  Citation × Citation Citation Abstract Copy Title: Upper ocean thermohaline fields near 2°S, 156°E, during the Tropical Ocean-Global Atmosphere - Coupled Ocean-Atmosphere Response Experiment, November 1992 to February 1993 Author: Hacker, Peter, Lukas, Roger, Huyer, Adriana, 1945-, Kosro, P. Michael, 1951- Zonal and meridional Seasoar sections centered at 1°50’S, 156°06’E were repeated >30 times in three 20-day periods between November 13, 1992, and February 15, 1993. Both sections were 130 km long, and sampling depth was 0–280 m, with a vertical resolution of ~2 dbar (2 x 104 Pa) and a horizontal resolution of ~3 km. The observed fields are complex and variable and are summarized graphically in several forms. Characteristics of the near-surface layer varied with the local winds which were variable and weak (<6 m s-1) during the first 20-day period, strong and westerly (>10 m s-1) during much of the second, and moderate and westerly (4-10 m s-1) during most of the third. Near-surface temperatures were warmest (up to 30°C) during the first period and coldest (often <29°C) during the second. Thermal stratification in the near-surface layer was strong under weak winds and weak under strong and moderate winds. Except during and after heavy rainfall, salinity stratification in the near-surface layer was generally weak. Surface salinity generally decreased toward the north. The depth of the surface isopycnal layer was often but not always limited by salinity stratification; the surface isohaline layer was shallower than the top of the thermocline throughout. Strong lateral temperature and salinity gradients occurred on a few occasions. Increased wind stress was associated with lateral homogenization as well as vertical mixing. Structure and water properties of the thermocline also varied between cruises and within each cruise. The upper thermocline was shallowest in late January after prolonged easterly winds. Isotherms in the upper and midthermocline (20°–25°C) sloped generally upward to the north, while those in the lower thermocline (12°–14°C) sloped down to envelop the core of the Equatorial Undercurrent, which shoaled (from 225 to 160 m) and warmed (from 15° to 20°C) between the first and last survey periods. Mesoscale and fine-scale water mass features were usually recognizable in sections less than a few days apart and migrated eastward at about 0.3 m s-1. There is a remarkably high degree of nonstationarity in these thermohaline fields from the Warm Pool of the western Pacific Ocean. Title: Upper ocean thermohaline fields near 2°S, 156°E, during the Tropical Ocean-Global Atmosphere - Coupled Ocean-Atmosphere Response Experiment, November 1992 to February 1993 Author: Hacker, Peter, Lukas, Roger, Huyer, Adriana, 1945-, Kosro, P. Michael, 1951- Zonal and meridional Seasoar sections centered at 1°50’S, 156°06’E were repeated >30 times in three 20-day periods between November 13, 1992, and February 15, 1993. Both sections were 130 km long, and sampling depth was 0–280 m, with a vertical resolution of ~2 dbar (2 x 104 Pa) and a horizontal resolution of ~3 km. The observed fields are complex and variable and are summarized graphically in several forms. Characteristics of the near-surface layer varied with the local winds which were variable and weak (<6 m s-1) during the first 20-day period, strong and westerly (>10 m s-1) during much of the second, and moderate and westerly (4-10 m s-1) during most of the third. Near-surface temperatures were warmest (up to 30°C) during the first period and coldest (often <29°C) during the second. Thermal stratification in the near-surface layer was strong under weak winds and weak under strong and moderate winds. Except during and after heavy rainfall, salinity stratification in the near-surface layer was generally weak. Surface salinity generally decreased toward the north. The depth of the surface isopycnal layer was often but not always limited by salinity stratification; the surface isohaline layer was shallower than the top of the thermocline throughout. Strong lateral temperature and salinity gradients occurred on a few occasions. Increased wind stress was associated with lateral homogenization as well as vertical mixing. Structure and water properties of the thermocline also varied between cruises and within each cruise. The upper thermocline was shallowest in late January after prolonged easterly winds. Isotherms in the upper and midthermocline (20°–25°C) sloped generally upward to the north, while those in the lower thermocline (12°–14°C) sloped down to envelop the core of the Equatorial Undercurrent, which shoaled (from 225 to 160 m) and warmed (from 15° to 20°C) between the first and last survey periods. Mesoscale and fine-scale water mass features were usually recognizable in sections less than a few days apart and migrated eastward at about 0.3 m s-1. There is a remarkably high degree of nonstationarity in these thermohaline fields from the Warm Pool of the western Pacific Ocean. Close

• 13. [Article] Secondary circulation associated with a shelfbreak front

  copyrighted by American Geophysical Union

  Citation × Citation Citation Abstract Copy Title: Secondary circulation associated with a shelfbreak front Author: Kosro, P. Michael, 1951-, Bogucki, Darek, Barth, John A., Pierce, Stephen D. copyrighted by American Geophysical Union Title: Secondary circulation associated with a shelfbreak front Author: Kosro, P. Michael, 1951-, Bogucki, Darek, Barth, John A., Pierce, Stephen D. copyrighted by American Geophysical Union Close

• 14. [Article] On the spatial structure of coastal circulation off Newport, Oregon, during spring and summer 2001 in a region of varying shelf width

  A time series of hourly surface current maps in the shelf waters off Newport, Oregon, was made during April–September 2001 using five SeaSonde HF current mappers, during Coastal Advances in Shelf Transport ...

  Citation × Citation Citation Abstract Copy Title: On the spatial structure of coastal circulation off Newport, Oregon, during spring and summer 2001 in a region of varying shelf width Author: Kosro, P. Michael, 1951- A time series of hourly surface current maps in the shelf waters off Newport, Oregon, was made during April–September 2001 using five SeaSonde HF current mappers, during Coastal Advances in Shelf Transport (COAST). The surface currents responded rapidly to the changing winds, in repeated patterns that were strongly affected by bottom topography. An equatorward current jet repeatedly formed in response to upwelling winds, its strength, but not its trajectory, covarying with the meridional wind stress. Near Cape Foulweather (44.8°N), where the shelf begins to widen, the jet rotates, weakens, and trends offshore to the south first along, then across, the isobaths. Below Cape Foulweather, inshore of the jet, a lee region of generally weak currents was commonly observed. The equatorward jet core was most commonly observed near the 80-m isobath between 45.0°N and 44.4°N, but transited offshore between spring and summer over Heceta Bank. At Newport (44.6°N), it was rarely observed less than 8 km from the coast. A second, inshore, equatorward jet, previously unknown, was observed repeatedly south of Waldport (44.4°N). Sustained downwelling wind episodes produced poleward currents, though less responsively north of Cape Foulweather. Strongest poleward flow was generally trapped near the coast. Surface currents were correlated with the northward wind, except regionally far from shore over Heceta Bank, responding within half a day. Response to the wind varies spatially, being intensified in the narrow shelf (northern) region. The equatorward jet persists through periods of zero wind forcing. Coastal sea level covaries with the meridional wind and the primary mode of ocean current response. Title: On the spatial structure of coastal circulation off Newport, Oregon, during spring and summer 2001 in a region of varying shelf width Author: Kosro, P. Michael, 1951- A time series of hourly surface current maps in the shelf waters off Newport, Oregon, was made during April–September 2001 using five SeaSonde HF current mappers, during Coastal Advances in Shelf Transport (COAST). The surface currents responded rapidly to the changing winds, in repeated patterns that were strongly affected by bottom topography. An equatorward current jet repeatedly formed in response to upwelling winds, its strength, but not its trajectory, covarying with the meridional wind stress. Near Cape Foulweather (44.8°N), where the shelf begins to widen, the jet rotates, weakens, and trends offshore to the south first along, then across, the isobaths. Below Cape Foulweather, inshore of the jet, a lee region of generally weak currents was commonly observed. The equatorward jet core was most commonly observed near the 80-m isobath between 45.0°N and 44.4°N, but transited offshore between spring and summer over Heceta Bank. At Newport (44.6°N), it was rarely observed less than 8 km from the coast. A second, inshore, equatorward jet, previously unknown, was observed repeatedly south of Waldport (44.4°N). Sustained downwelling wind episodes produced poleward currents, though less responsively north of Cape Foulweather. Strongest poleward flow was generally trapped near the coast. Surface currents were correlated with the northward wind, except regionally far from shore over Heceta Bank, responding within half a day. Response to the wind varies spatially, being intensified in the narrow shelf (northern) region. The equatorward jet persists through periods of zero wind forcing. Coastal sea level covaries with the meridional wind and the primary mode of ocean current response. Close

• 15. [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

• 16. [Article] Currents and water masses of the coastal transition zone off Northern California, June to August 1988

  In summer 1988, we made repeated mesoscale surveys of a grid extending 200 km offshore between 37°N and 39°N in the coastal transition zone off northern California, obtaining continuous acoustic Doppler ...

  Citation × Citation Citation Abstract Copy Title: Currents and water masses of the coastal transition zone off Northern California, June to August 1988 Author: Ramp, Steven R., Washburn, Libe, Cowles, Timothy J., Fleischbein, Jane, Stanton, Tim, Huyer, Adriana, 1945-, Kosro, P. Michael, 1951-, Smith, Robert L. (Robert Lloyd), 1935-, Pierce, Stephen D., Chavez, Francisco P. In summer 1988, we made repeated mesoscale surveys of a grid extending 200 km offshore between 37°N and 39°N in the coastal transition zone off northern California, obtaining continuous acoustic Doppler current profiler data and conductivity-temperature-depth data at standard stations 25 km apart on alongshore sections 40 km apart. All surveys showed a baroclinic equatorward jet, with core velocities of >50 cm/s at the surface decreasing to about 10 cm/s at 200m , a width of 50-75 km, and a baroclinic transporotf about4 Sv. The core of the jet lay between the 8.6 and9 .4 m²/s² contours of geopotential anomaly (relative to 500 dbar). Three current meter moorings, deployed at 25-km separation across the jet at the beginning of the survey sequence, provided time-series of the velocity; throughout the 37-day deployment, at least one mooring was within the core defined by the 8.6 and9 .4 m²/s² contours. The jet flowed southwestward across the grid from late June until mid-July 1988, when the jet axis moved offshore in the north and onshore in the southern portion of the grid. Temperature-salinity analysis shows that jet waters can be distinguished from both the freshly upwelled coastal waters and the offshore waters. Isopycnal maps indicate alongshore advection of relatively fresh, cool water from farther north, as well as small-scale patchiness not resolved by our survey grid. The baroclinic jet observed here may be continuous with the core of the California Current off central California. The later surveys clearly showed a poleward-flowing undercurrent adjacent to the continental slope, with core velocities up to 20 cm/s at depths of 150-250 m. Its baroclinic transport (relative to 500 dbar) increased from <0.5 Sv to >1.0 Sv between late June and early August 1988. Within the survey grid, there was a definite onshore gradient in the characteristics of North Pacific Intermediate Water. The subsurface waters adjacent to the continental margin were warmer and more saline than those offshore, indicating net northward advection by the California Undercurrent over the inshore 100 km and equatorward advection farther from shore. Title: Currents and water masses of the coastal transition zone off Northern California, June to August 1988 Author: Ramp, Steven R., Washburn, Libe, Cowles, Timothy J., Fleischbein, Jane, Stanton, Tim, Huyer, Adriana, 1945-, Kosro, P. Michael, 1951-, Smith, Robert L. (Robert Lloyd), 1935-, Pierce, Stephen D., Chavez, Francisco P. In summer 1988, we made repeated mesoscale surveys of a grid extending 200 km offshore between 37°N and 39°N in the coastal transition zone off northern California, obtaining continuous acoustic Doppler current profiler data and conductivity-temperature-depth data at standard stations 25 km apart on alongshore sections 40 km apart. All surveys showed a baroclinic equatorward jet, with core velocities of >50 cm/s at the surface decreasing to about 10 cm/s at 200m , a width of 50-75 km, and a baroclinic transporotf about4 Sv. The core of the jet lay between the 8.6 and9 .4 m²/s² contours of geopotential anomaly (relative to 500 dbar). Three current meter moorings, deployed at 25-km separation across the jet at the beginning of the survey sequence, provided time-series of the velocity; throughout the 37-day deployment, at least one mooring was within the core defined by the 8.6 and9 .4 m²/s² contours. The jet flowed southwestward across the grid from late June until mid-July 1988, when the jet axis moved offshore in the north and onshore in the southern portion of the grid. Temperature-salinity analysis shows that jet waters can be distinguished from both the freshly upwelled coastal waters and the offshore waters. Isopycnal maps indicate alongshore advection of relatively fresh, cool water from farther north, as well as small-scale patchiness not resolved by our survey grid. The baroclinic jet observed here may be continuous with the core of the California Current off central California. The later surveys clearly showed a poleward-flowing undercurrent adjacent to the continental slope, with core velocities up to 20 cm/s at depths of 150-250 m. Its baroclinic transport (relative to 500 dbar) increased from <0.5 Sv to >1.0 Sv between late June and early August 1988. Within the survey grid, there was a definite onshore gradient in the characteristics of North Pacific Intermediate Water. The subsurface waters adjacent to the continental margin were warmer and more saline than those offshore, indicating net northward advection by the California Undercurrent over the inshore 100 km and equatorward advection farther from shore. Close