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• 1. [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

• 2. [Article] SEASOAR and CTD observations during EBC cruises W9306A and W9308B, June to September 1993

  Citation × Citation Citation Abstract Copy Title: SEASOAR and CTD observations during EBC cruises W9306A and W9308B, June to September 1993 Author: Shearman, R. Kipp, Smith, Robert L. (Robert Lloyd), 1935-, Fleischbein, Jane, Oregon State University. College of Oceanic and Atmospheric Sciences, O'Malley, Robert T., Huyer, Adriana, 1945-, Kosro, P. Michael, 1951-, Barth, John A. Title: SEASOAR and CTD observations during EBC cruises W9306A and W9308B, June to September 1993 Author: Shearman, R. Kipp, Smith, Robert L. (Robert Lloyd), 1935-, Fleischbein, Jane, Oregon State University. College of Oceanic and Atmospheric Sciences, O'Malley, Robert T., Huyer, Adriana, 1945-, Kosro, P. Michael, 1951-, Barth, John A. Close

• 3. [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

• 4. [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

• 5. [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

• 6. [Article] Two coastal upwelling domains in the northern California Current system

  A pair of hydrographic sections, one north and one south of Cape Blanco at 42.9N, was sampled in five summers (1998–2000 and 2002–2003). The NH line at 44.6N lies about 130 km south of the Columbia River, ...

  Citation × Citation Citation Abstract Copy Title: Two coastal upwelling domains in the northern California Current system Author: Wheeler, Patricia A., Smith, Robert L. (Robert Lloyd), 1935-, Perlin, Natalie, Keister, Julie Eileen, Huyer, Adriana, 1945-, Kosro, P. Michael, 1951-, Fleischbein, Jane A pair of hydrographic sections, one north and one south of Cape Blanco at 42.9N, was sampled in five summers (1998–2000 and 2002–2003). The NH line at 44.6N lies about 130 km south of the Columbia River, and spans a relatively wide shelf off Newport, Oregon. The CR line at 41.9N off Crescent City, California, lies 300 km farther south and spans a narrower shelf. Summer winds are predominantly southward in both locations but the southward winds are stronger on the CR line. Sampling included CTD/rosette casts (to measure temperature, salinity, dissolved oxygen, nutrients, chlorophyll), zooplankton net tows and continuous operation of an Acoustic Doppler Current Profiler. We summarize and compare July-August observations from the two locations. We find significant summer-season differences in the coastal upwelling domains north and south of Cape Blanco. Compared to the domain off Newport, the domain off Crescent City has a more saline, cooler, denser and thicker surface mixed layer, a wider coastal zone inshore of the upwelling front and jet, higher nutrient concentrations in the photic zone and higher phytoplankton biomass. The southward coastal jet lies near the coast (about 20–30 km offshore, over the shelf) on the NH line, but far from shore (about 120 km) on the CR line; a weak secondary jet lies near the shelf-break (35 km from shore) off Crescent City. Phytoplankton tend to be light-limited on the CR line and nutrient-limited on the NH line. Copepod biomass is high (15 mg C m-3) inshore of the mid-shelf on both NH and CR lines, and is also high in the core of the coastal jet off Crescent City. The CR line shows evidence of deep chlorophyll pockets that have been subducted from the surface layer. We attribute these significant differences to stronger mean southward wind stress over the southern domain, to strong small-scale wind stress curl in the lee of Cape Blanco, and to the reduced influence of the Columbia River discharge in this region. Title: Two coastal upwelling domains in the northern California Current system Author: Wheeler, Patricia A., Smith, Robert L. (Robert Lloyd), 1935-, Perlin, Natalie, Keister, Julie Eileen, Huyer, Adriana, 1945-, Kosro, P. Michael, 1951-, Fleischbein, Jane A pair of hydrographic sections, one north and one south of Cape Blanco at 42.9N, was sampled in five summers (1998–2000 and 2002–2003). The NH line at 44.6N lies about 130 km south of the Columbia River, and spans a relatively wide shelf off Newport, Oregon. The CR line at 41.9N off Crescent City, California, lies 300 km farther south and spans a narrower shelf. Summer winds are predominantly southward in both locations but the southward winds are stronger on the CR line. Sampling included CTD/rosette casts (to measure temperature, salinity, dissolved oxygen, nutrients, chlorophyll), zooplankton net tows and continuous operation of an Acoustic Doppler Current Profiler. We summarize and compare July-August observations from the two locations. We find significant summer-season differences in the coastal upwelling domains north and south of Cape Blanco. Compared to the domain off Newport, the domain off Crescent City has a more saline, cooler, denser and thicker surface mixed layer, a wider coastal zone inshore of the upwelling front and jet, higher nutrient concentrations in the photic zone and higher phytoplankton biomass. The southward coastal jet lies near the coast (about 20–30 km offshore, over the shelf) on the NH line, but far from shore (about 120 km) on the CR line; a weak secondary jet lies near the shelf-break (35 km from shore) off Crescent City. Phytoplankton tend to be light-limited on the CR line and nutrient-limited on the NH line. Copepod biomass is high (15 mg C m-3) inshore of the mid-shelf on both NH and CR lines, and is also high in the core of the coastal jet off Crescent City. The CR line shows evidence of deep chlorophyll pockets that have been subducted from the surface layer. We attribute these significant differences to stronger mean southward wind stress over the southern domain, to strong small-scale wind stress curl in the lee of Cape Blanco, and to the reduced influence of the Columbia River discharge in this region. Close

• 7. [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

• 8. [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

• 9. [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