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Huyer A.. Coastal upwelling in the California current system. Prog Oceanogr 12: 259

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Abstract

Coastal upwelling in the California Current system has been the subject of large scale studies off California and Baja California, and of small scale studies off Oregon. Recent studies of the winds along the entire coast from 25°N to 50°N indicate that there are significant along-shore variations in the strength of coastal upwelling, which are reflected in the observed temperature distribution. Active upwelling appears to be restricted to a narrow coastal band (about 10–25 km wide) along the entire coast, but the region influenced by coastal upwelling may be much wider. Intensive observations of the upwelling zone during summer off Oregon show the presence of a southward coastal jet at the surface, a mean vertical shear, a poleward undercurrent along the bottom, and persistently sloping isopycnals over the continental shelf; most of the upwelling there occurs during relatively short periods (several days long) of upwelling-favorable winds. During the upwelling season off Oregon, the offshore Ekman transport is carried by the surface Ekman layer, and the onshore return flow occurs through a quasi-geostrophic interior. It is not known whether the structure and dynamics observed off Oregon are typical of the upwelling zone along the entire coast, though some of the same features have been observed off Baja California. Current and future research will eventually show whether the Oregon results are also applicable in the region of persistently strong upwelling-favorable winds off northern California, and in the region of complex bathymetry off central and southern California.
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... Due to their narrowly focused prey regime, blue whale health is closely linked with environmental factors that determine prey abundance and concentration (Croll et al., 2005;Calambokidis et al., 2007;Silber et al., 2017). The eastern North Pacific blue whales forage partially in the highly productive California Current System which spans from British Columbia, Canada (~50°N) to Baja California, Mexico (~15-25°N) (Huyer, 1983;Di Lorenzo et al., 2008;McClatchie et al., 2008;Checkley and Barth, 2009;Palacios et al., 2019). Productivity in the California Current System is driven by patterns of variability on various spatial and temporal scales from local and seasonal upwelling to ocean basin level interannual/decadal Pacific Decadal Oscillation. ...
... We looked at both the average annual PDO value for each year and PDO as a binomial factor (positive or negative). On a smaller temporal and spatial scale, seasonal upwelling occurs in the spring/summer and varies in duration (LUSI) at different latitudes along the current, which leads to high levels of primary and secondary production (Huyer, 1983;Fiedler et al., 1998;Croll et al., 2005;Bograd et al., 2009;Checkley and Barth, 2009). The California Current System also experienced a heat wave from 2014-2016 and we considered all months of those years to be under the influence of the heat wave. ...
... PDO reflects sea surface temperature in the Pacific Ocean basin with positive PDO values signifying warmer ocean temperatures (Mantua and Hare, 2002;Brinton and Townsend, 2003;Di Lorenzo and Mantua, 2016). We also looked at LUSI since upwelling occurs on a smaller temporal scale than PDO, seasonally leading to high levels of primary and secondary production (Huyer, 1983;Fiedler et al., 1998;Croll et al., 2005;Checkley and Barth, 2009). The seasonal upwelling coincides with the summer feeding period for blue whales (Croll et al., 2005;Barlow et al., 2020) and therefore its length could drive overall foraging success. ...
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... Then we took all the DO, pH, and temperature values measured over each month from May−October and calculated the monthly variance in oxygen and pH and the average monthly temperature. We focused on the relationship between grazing and these factors, since upwelling is known to bring colder, more variable conditions in spring versus fall (Huyer 1983). Additionally, lowfrequency variability (i.e. ...
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... In addition to wake effects extending to the lee of the predominant wind direction, shorter-term wake effects are seen southeast of the call areas, presumably due to eddying of wind fields. While distinct in Figure 4, these shorter term wakes are not expected to affect coastal upwelling, which requires sustained northwesterly winds to occur on time scales of several days (Huyer, 1983). ...
... Wind speeds generally trend lower as fall transitions to winter, typical of weather patterns along the California coast. The seasonal atmospheric circulation is driven by the location of the North Pacific High and terrestrial surface pressures that in turn are modulated by seasonal heating and cooling (Huyer, 1983). Figure 8 shows a close-up of spring season wind speed changes around each of the call areas, at 10 m height above the sea surface. ...
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In California offshore waters, sustained northwesterly winds have been identified as a key energy resource that could contribute substantially to California’s renewable energy mandate. It is these winds that drive upwelling, which is responsible for much of the primary productivity that sustains one of the richest ecosystems on the planet. The goal of this study is to quantify changes in wind fields at the sea surface as the result of offshore wind turbine deployments by use of an atmospheric model. Modeled wind fields from this study will drive an ocean circulation model. The Weather Research and Forecasting model was implemented on a regional scale along the U.S. west coast, with a higher resolution nest along the California continental shelf. Simulated arrays of offshore wind turbines were placed within call areas for wind farm development offshore of Central and Northern California. At full build-out, it was found that wind speeds at 10 m height are reduced by approximately 5%, with wakes extending approximately 200 km downwind of the nominated lease block areas. The length scale of wind speed reductions was found to be several times the internal Rossby radius of deformation, the spatial scale at which rotationally-influenced ocean circulation processes such as upwelling occur.
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... Coastal upwelling records support the hypothesis that the strength of the westerlies in wNAm was related to Holocene LTG. Spring and summer upwelling along the west coast of North America is driven by persistent northwesterly winds (Huyer, 1983). The coastal northwesterlies stem from the synoptic-scale westerlies and the position of the Pacific High. ...
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... In the coastal ocean, high pCO 2(sw) occurs in the central CCS (∼ 34 to ∼ 42 • N), with values of 400 µatm or greater beginning in April off Pt. Conception (34 • N) and propagating northward to around Cape Arago (43 • N) through October (Fig. 7). This corresponds to the latitudinal band of the CCS with the strongest and most consistent equatorward winds (Huyer, 1983), which induce upwelling of CO 2 -rich subsurface waters by wind-driven Ekman transport very near the coast and wind-stress-curl-driven Ekman pumping farther offshore (Checkley and Barth, 2009). This nearshore band of high summertime pCO 2(sw) has been previously reported by observational and modeling (Fiechter et al., 2014;Turi et al., 2014;Deutsch et al., 2021) studies. ...
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