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• 1. [Article] Analysis of particulate organic matter distribution along surface waters of the California Current

  Water samples along the Washington, Oregon and California coastline were collected using high resolution sampling and analyzed to determine particulate organic carbon and nitrogen concentrations. Over ...

  Citation × Citation Citation Abstract Copy Title: Analysis of particulate organic matter distribution along surface waters of the California Current Author: Welch, Kylie Water samples along the Washington, Oregon and California coastline were collected using high resolution sampling and analyzed to determine particulate organic carbon and nitrogen concentrations. Over 28 days during August 2011, nearly 1500 samples were collected aboard the R/V Wecoma (W1108C) using a semi-automated filtration system. Additional subsurface samples were collected from CTD casts. In-situ measurements of temperature, salinity, chlorophyll fluorescence, and beam attenuation were combined with the data from individual samples to provide a near-synoptic, spatial distribution of particulate organic matter along the California Current. Marked contrasts in the concentrations and compositions of particulate organic matter were observed among different water masses along the margin, including those directly affected by Columbia River discharge, recently upwelled near-shore waters, and filaments associated with mesoscales eddies. My results demonstrate the utility of high-resolution sampling techniques can be integrated with remote sensing approaches to better understand physical-biological interactions in the coastal ocean. Title: Analysis of particulate organic matter distribution along surface waters of the California Current Author: Welch, Kylie Water samples along the Washington, Oregon and California coastline were collected using high resolution sampling and analyzed to determine particulate organic carbon and nitrogen concentrations. Over 28 days during August 2011, nearly 1500 samples were collected aboard the R/V Wecoma (W1108C) using a semi-automated filtration system. Additional subsurface samples were collected from CTD casts. In-situ measurements of temperature, salinity, chlorophyll fluorescence, and beam attenuation were combined with the data from individual samples to provide a near-synoptic, spatial distribution of particulate organic matter along the California Current. Marked contrasts in the concentrations and compositions of particulate organic matter were observed among different water masses along the margin, including those directly affected by Columbia River discharge, recently upwelled near-shore waters, and filaments associated with mesoscales eddies. My results demonstrate the utility of high-resolution sampling techniques can be integrated with remote sensing approaches to better understand physical-biological interactions in the coastal ocean. Close

• 2. [Article] Coastal ocean response to alongshore variations in topography and wind forcing

  The effects of alongshore variability in topography (banks and capes) and spatial variability in the wind forcing, including the wind-stress curl, on coastal ocean circulation are studied using a combination ...

  Citation × Citation Citation Abstract Copy Title: Coastal ocean response to alongshore variations in topography and wind forcing Author: Castelao, Renato Menezes The effects of alongshore variability in topography (banks and capes) and spatial variability in the wind forcing, including the wind-stress curl, on coastal ocean circulation are studied using a combination of observations and model simulations. Satellite sea surface temperature observations are used to describe the seasonal evolution of temperature fronts in the California Current System. The evolution is consistent with the seasonal cycle of wind forcing, but also reveals the profound influence of major capes in creating convoluted and offshore-diverted fronts. Although the greatest offshore excursion of fronts is found south of Cape Blanco, observations suggest that late in the upwelling season, the upwelling front (and jet) leaves the shelf to the north of the Cape, around Heceta Bank. This is supported by in situ observations obtained during the Coastal Ocean Advances in Shelf Transport (COAST) project, which depicted jet separation at Heceta Bank's downstream asymmetry with an average off-shelf transport around 0.7 Sv. Simulations exploring a large range in parameter space show that jet separation is expected to occur when the flow is strong (high Rossby number) and when the Burger number (the ratio of the squares of the internal Rossby radius of deformation and curvature of the topography) is close to one. Observations reveal that conditions at Heceta Bank during spring and summer are often nearly ideal for separation. The importance of the wind-stress curl to coastal circulation is also investigated. A region of upwelling-favorable wind-stress curl close to the coast downstream of a cape is shown to create a strong offshore intensification of the alongshore velocities, which helps jet separation via continuity and by creating potential vorticity contours that track far offshore of the cape. Stronger upwelling-favorable curl leads to earlier separation, while increasing the offshore extend of the region of strong curl leads to more separation. Finally, satellite scatterometer observations are used to show that the wind-stress curl is strongly enhanced around Cabo Frio, Brazil, during summer. At that time, curl-driven upwelling is as strong as coastal upwelling, which helps explain the observation that the coldest water along the coast is found near Cabo Frio. Title: Coastal ocean response to alongshore variations in topography and wind forcing Author: Castelao, Renato Menezes The effects of alongshore variability in topography (banks and capes) and spatial variability in the wind forcing, including the wind-stress curl, on coastal ocean circulation are studied using a combination of observations and model simulations. Satellite sea surface temperature observations are used to describe the seasonal evolution of temperature fronts in the California Current System. The evolution is consistent with the seasonal cycle of wind forcing, but also reveals the profound influence of major capes in creating convoluted and offshore-diverted fronts. Although the greatest offshore excursion of fronts is found south of Cape Blanco, observations suggest that late in the upwelling season, the upwelling front (and jet) leaves the shelf to the north of the Cape, around Heceta Bank. This is supported by in situ observations obtained during the Coastal Ocean Advances in Shelf Transport (COAST) project, which depicted jet separation at Heceta Bank's downstream asymmetry with an average off-shelf transport around 0.7 Sv. Simulations exploring a large range in parameter space show that jet separation is expected to occur when the flow is strong (high Rossby number) and when the Burger number (the ratio of the squares of the internal Rossby radius of deformation and curvature of the topography) is close to one. Observations reveal that conditions at Heceta Bank during spring and summer are often nearly ideal for separation. The importance of the wind-stress curl to coastal circulation is also investigated. A region of upwelling-favorable wind-stress curl close to the coast downstream of a cape is shown to create a strong offshore intensification of the alongshore velocities, which helps jet separation via continuity and by creating potential vorticity contours that track far offshore of the cape. Stronger upwelling-favorable curl leads to earlier separation, while increasing the offshore extend of the region of strong curl leads to more separation. Finally, satellite scatterometer observations are used to show that the wind-stress curl is strongly enhanced around Cabo Frio, Brazil, during summer. At that time, curl-driven upwelling is as strong as coastal upwelling, which helps explain the observation that the coldest water along the coast is found near Cabo Frio. Close

• 3. [Article] Variability in mesoscale circulation and its effects on zooplankton distribution in the Northern California Current

  In eastern boundary current upwelling ecosystems, mesoscale circulation features such as eddies and upwelling filaments play a prominent role in the transfer of water and the associated plankton from the ...

  Citation × Citation Citation Abstract Copy Title: Variability in mesoscale circulation and its effects on zooplankton distribution in the Northern California Current Author: Keister, Julie Eileen In eastern boundary current upwelling ecosystems, mesoscale circulation features such as eddies and upwelling filaments play a prominent role in the transfer of water and the associated plankton from the productive nearshore to the oligotrophic deep sea. The relationship between mesoscale circulation, zooplankton distributions, and the across-shelf transport of coastal taxa and biomass in the California Current System was studied using data collected as part of the U.S. Global Ocean Ecosystems Dynamics (GLOBEC) Northeast Pacific Program. Sea surface height from >13 years of satellite altimeter data was used to characterize the spatial and temporal variability in mesoscale circulation in the northern California Current (35°N-49°N) and explore mechanisms of variability. High spatial and temporal variation in mesoscale energy occurred. Energy was not strongly linked to upwelling winds, but did correspond to climate indices, indicating that basin-scale processes play a role in controlling the circulation. CTD casts, zooplankton net tows, and Acoustic Doppler Current Profiler (ADCP) velocities collected during a research cruise conducted in summer 2000 off Oregon and northern California were used to describe the effects of mesoscale circulation on distributions of zooplankton. During the cruise, a filament of the coastal upwelling jet extended seaward of Cape Blanco (42.8°N) resulting in the displacement of coastal zooplankton to >100 km off the continental shelf. Velocities and standing stocks of zooplankton were used to estimate seaward transport of 0.5 Sv in the upper 100 m of the filament, in which zooplankton biomass averaged ~20 mg carbon/m³. That offshore transport equated to >900 metric tons of carbon each day, and 4-5x10⁴ tons over the 6-8 week lifetime of the circulation feature. Although the flux represented a small portion (<2%) of the shelf zooplankton biomass, the transport resulted in an offshore "hot-spot" in which biomass was 3-4X higher than in the surrounding ocean. Distributions of early life history stages of euphausiids indicated that retention of coastal populations may be strongly affected by the offshore advection. Finally, satellite sea surface temperature (SST) and sampling conducted during five summers were used to explore variability in the relationship between mesoscale circulation features and distributions of zooplankton. Circulation patterns differed among cruises and were reflected in zooplankton distributions. Circulation features resulted in the occurrence of cold surface water and coastal taxa offshore, but species abundances and presence/absence of taxa at specific locations were not predictable from satellite SSTs. These results are relevant to studies of ecosystem dynamics and the global carbon cycle because mesoscale circulation plays an important role in the seaward transport of carbon, retention and loss of taxa from the continental shelf, and creation of offshore structure which may be exploited by upper trophic level organisms. Title: Variability in mesoscale circulation and its effects on zooplankton distribution in the Northern California Current Author: Keister, Julie Eileen In eastern boundary current upwelling ecosystems, mesoscale circulation features such as eddies and upwelling filaments play a prominent role in the transfer of water and the associated plankton from the productive nearshore to the oligotrophic deep sea. The relationship between mesoscale circulation, zooplankton distributions, and the across-shelf transport of coastal taxa and biomass in the California Current System was studied using data collected as part of the U.S. Global Ocean Ecosystems Dynamics (GLOBEC) Northeast Pacific Program. Sea surface height from >13 years of satellite altimeter data was used to characterize the spatial and temporal variability in mesoscale circulation in the northern California Current (35°N-49°N) and explore mechanisms of variability. High spatial and temporal variation in mesoscale energy occurred. Energy was not strongly linked to upwelling winds, but did correspond to climate indices, indicating that basin-scale processes play a role in controlling the circulation. CTD casts, zooplankton net tows, and Acoustic Doppler Current Profiler (ADCP) velocities collected during a research cruise conducted in summer 2000 off Oregon and northern California were used to describe the effects of mesoscale circulation on distributions of zooplankton. During the cruise, a filament of the coastal upwelling jet extended seaward of Cape Blanco (42.8°N) resulting in the displacement of coastal zooplankton to >100 km off the continental shelf. Velocities and standing stocks of zooplankton were used to estimate seaward transport of 0.5 Sv in the upper 100 m of the filament, in which zooplankton biomass averaged ~20 mg carbon/m³. That offshore transport equated to >900 metric tons of carbon each day, and 4-5x10⁴ tons over the 6-8 week lifetime of the circulation feature. Although the flux represented a small portion (<2%) of the shelf zooplankton biomass, the transport resulted in an offshore "hot-spot" in which biomass was 3-4X higher than in the surrounding ocean. Distributions of early life history stages of euphausiids indicated that retention of coastal populations may be strongly affected by the offshore advection. Finally, satellite sea surface temperature (SST) and sampling conducted during five summers were used to explore variability in the relationship between mesoscale circulation features and distributions of zooplankton. Circulation patterns differed among cruises and were reflected in zooplankton distributions. Circulation features resulted in the occurrence of cold surface water and coastal taxa offshore, but species abundances and presence/absence of taxa at specific locations were not predictable from satellite SSTs. These results are relevant to studies of ecosystem dynamics and the global carbon cycle because mesoscale circulation plays an important role in the seaward transport of carbon, retention and loss of taxa from the continental shelf, and creation of offshore structure which may be exploited by upper trophic level organisms. Close