Wind-induced upwelling along the west coast of North America, 1899–1988

1995 ◽  
Vol 52 (2) ◽  
pp. 325-334 ◽  
Author(s):  
William W. Hsieh ◽  
Daniel M. Ware ◽  
Richard E. Thomson
Keyword(s):  
British Columbia ◽  
Baja California ◽  
Coastal Upwelling ◽  
Function Analysis ◽  
Geostrophic Wind ◽  
Second Mode ◽  
Coastal Sea ◽  
Coastal Downwelling ◽  
Alongshore Wind Stress ◽  
Alongshore Wind

Alongshore geostrophic wind stresses (AWS) were used as an "index" of wind-induced coastal upwelling/downwelling for eight coastal stations from Baja California to Alaska for 1899–1988. For winters since around 1940, downwelling has intensified along Alaska and northern British Columbia, while upwelling has increased along Baja California. El Niño events induced strong winter coastal downwelling poleward of 40°N. During summer, upwelling has increased since around 1940 along southern British Columbia to Baja California, while from 1899 to 1940, upwelling declined along southern California to Baja California. Empirical orthogonal function analysis of the AWS showed that the first mode consisted of the AWS at the eight stations all varying in-phase, while the second mode had the northern four stations out-of-phase with the southern four stations. Off southern British Columbia, correlations between coastal sea level and AWS and between sea surface temperature and AWS were both strong during winter but insignificant during summer. In contrast, correlation between salinity and alongshore wind stress was insignificant during fall and winter, but strong during spring and moderate during summer. Summer AWS was positively correlated with both the fatness of sardine and the condition factor of herring off British Columbia.

scholarly journals Seasonal variability of the Ekman transport and pumping in the upwelling system off central-northern Chile (∼  30° S) based on a high-resolution atmospheric regional model (WRF)

Ocean Science ◽  
2016 ◽  
Vol 12 (5) ◽  
pp. 1049-1065 ◽  
Author(s):  
Luis Bravo ◽  
Marcel Ramos ◽  
Orlando Astudillo ◽  
Boris Dewitte ◽  
Katerina Goubanova
Keyword(s):  
High Resolution ◽  
Wind Stress ◽  
Seasonal Variability ◽  
Coastal Upwelling ◽  
Ekman Transport ◽  
Northern Chile ◽  
Ekman Pumping ◽  
Relative Contribution ◽  
Alongshore Wind Stress ◽  
Alongshore Wind

Abstract. Two physical mechanisms can contribute to coastal upwelling in eastern boundary current systems: offshore Ekman transport due to the predominant alongshore wind stress and Ekman pumping due to the cyclonic wind stress curl, mainly caused by the abrupt decrease in wind stress (drop-off) in a cross-shore band of 100 km. This wind drop-off is thought to be an ubiquitous feature in coastal upwelling systems and to regulate the relative contribution of both mechanisms. It has been poorly studied along the central-northern Chile region because of the lack in wind measurements along the shoreline and of the relatively low resolution of the available atmospheric reanalysis. Here, the seasonal variability in Ekman transport, Ekman pumping and their relative contribution to total upwelling along the central-northern Chile region (∼  30° S) is evaluated from a high-resolution atmospheric model simulation. As a first step, the simulation is validated from satellite observations, which indicates a realistic representation of the spatial and temporal variability of the wind along the coast by the model. The model outputs are then used to document the fine-scale structures in the wind stress and wind curl in relation to the topographic features along the coast (headlands and embayments). Both wind stress and wind curl had a clear seasonal variability with annual and semiannual components. Alongshore wind stress maximum peak occurred in spring, second increase was in fall and minimum in winter. When a threshold of −3  ×  10−5 s−1 for the across-shore gradient of alongshore wind was considered to define the region from which the winds decrease toward the coast, the wind drop-off length scale varied between 8 and 45 km. The relative contribution of the coastal divergence and Ekman pumping to the vertical transport along the coast, considering the estimated wind drop-off length, indicated meridional alternation between both mechanisms, modulated by orography and the intricate coastline. Roughly, coastal divergence predominated in areas with low orography and headlands. Ekman pumping was higher in regions with high orography and the presence of embayments along the coast. In the study region, the vertical transport induced by coastal divergence and Ekman pumping represented 60 and 40 % of the total upwelling transport, respectively. The potential role of Ekman pumping on the spatial structure of sea surface temperature is also discussed.

scholarly journals A Simple Analytical Model of Periodic Coastal Upwelling

2011 ◽  
Vol 41 (6) ◽  
pp. 1271-1276 ◽  
Author(s):  
Mirko Orlić ◽  
Zoran Pasarić
Keyword(s):  
Gravity Waves ◽  
Coastal Upwelling ◽  
Wind Forcing ◽  
Simple Analytical Model ◽  
Temperature Oscillations ◽  
Coastal Sea ◽  
Near Shore ◽  
Wind Driven Currents ◽  
Inertial Currents ◽  
Alongshore Wind

Abstract An existing reduced-gravity model that reproduces the response of the coastal sea to alongshore wind forcing at subinertial frequencies is extended by allowing for cross-shore wind forcing and by considering superinertial frequencies. The obtained explicit solution shows that the wind-driven currents are predominantly controlled by friction and the Coriolis force at subinertial frequencies and by friction and local acceleration at superinertial frequencies. The effect of the coast is manifested by coastal-trapped variability at subinertial frequencies and baroclinic inertia–gravity waves propagating away from the coast at superinertial frequencies. The pycnocline oscillates at the coast not only at subinertial but also at superinertial frequencies, with the alongshore wind contributing more to the former and the cross-shore wind influencing more the latter. The oscillations are most pronounced when the periodic wind forcing is resonantly coupled to the local inertial oscillations (but only if the wind is not rotating counter to the inertial currents) and at near-zero frequencies (but not when the wind is purely cross-shore). These theoretical findings are related to recent observations of diurnal temperature oscillations in the near-shore water column.

scholarly journals Seasonal Variability of SST Fronts in the Inner Sea of Chiloé and Its Adjacent Coastal Ocean, Northern Patagonia

2021 ◽  
Vol 13 (2) ◽  
pp. 181
Author(s):  
Gonzalo S. Saldías ◽  
Wilber Hernández ◽  
Carlos Lara ◽  
Richard Muñoz ◽  
Cristian Rojas ◽  
...  
Keyword(s):  
Coastal Upwelling ◽  
Environmental Variability ◽  
Function Analysis ◽  
Coastal Ocean ◽  
Dominant Mode ◽  
Early Summer ◽  
High Biological Activity ◽  
Northern Patagonia ◽  
Sst Gradient ◽  
Sst Fronts

Surface oceanic fronts are regions characterized by high biological activity. Here, Sea Surface Temperature (SST) fronts are analyzed for the period 2003–2019 using the Multi-scale Ultra-high Resolution (MUR) SST product in northern Patagonia, a coastal region with high environmental variability through river discharges and coastal upwelling events. SST gradient magnitudes were maximum off Chiloé Island in summer and fall, coherent with the highest frontal probability in the coastal oceanic area, which would correspond to the formation of a coastal upwelling front in the meridional direction. Increased gradient magnitudes in the Inner Sea of Chiloé (ISC) were found primarily in spring and summer. The frontal probability analysis revealed the highest occurrences were confined to the northern area (north of Desertores Islands) and around the southern border of Boca del Guafo. An Empirical Orthogonal Function analysis was performed to clarify the dominant modes of variability in SST gradient magnitudes. The meridional coastal fronts explained the dominant mode (78% of the variance) off Chiloé Island, which dominates in summer, whereas the SST fronts inside the ISC (second mode; 15.8%) were found to dominate in spring and early summer (October–January). Future efforts are suggested focusing on high frontal probability areas to study the vertical structure and variability of the coastal fronts in the ISC and its adjacent coastal ocean.

scholarly journals Alongshore Wind Forcing of Coastal Sea Level as a Function of Frequency

2006 ◽  
Vol 36 (11) ◽  
pp. 2173-2184 ◽  
Author(s):  
Holly F. Ryan ◽  
Marlene A. Noble
Keyword(s):  
United States ◽  
Frequency Response ◽  
Sea Level ◽  
Response Function ◽  
Wind Field ◽  
Frequency Response Function ◽  
The United States ◽  
The West ◽  
Coastal Sea ◽  
Alongshore Wind

Abstract The amplitude of the frequency response function between coastal alongshore wind stress and adjusted sea level anomalies along the west coast of the United States increases linearly as a function of the logarithm (log10) of the period for time scales up to at least 60, and possibly 100, days. The amplitude of the frequency response function increases even more rapidly at longer periods out to at least 5 yr. At the shortest periods, the amplitude of the frequency response function is small because sea level is forced only by the local component of the wind field. The regional wind field, which controls the wind-forced response in sea level for periods between 20 and 100 days, not only has much broader spatial scales than the local wind, but also propagates along the coast in the same direction as continental shelf waves. Hence, it has a stronger coupling to and an increased frequency response for sea level. At periods of a year or more, observed coastal sea level fluctuations are not only forced by the regional winds, but also by joint correlations among the larger-scale climatic patterns associated with El Niño. Therefore, the amplitude of the frequency response function is large, despite the fact that the energy in the coastal wind field is relatively small. These data show that the coastal sea level response to wind stress forcing along the west coast of the United States changes in a consistent and predictable pattern over a very broad range of frequencies with time scales from a few days to several years.

scholarly journals COASTAL SEA SURFACE TEMPERATURE RECORDS ALONG THE BAJA CALIFORNIA PENINSULA

2012 ◽  
Vol 27 (2) ◽  
pp. 65
Author(s):  
M. T. Sicard -González ◽  
M. A. Tripp -Valdéz ◽  
L. Ocampo ◽  
A. N. Maeda -Martínez ◽  
S. E. Lluch -Cota
Keyword(s):  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Baja California ◽  
Sea Surface ◽  
Baja California Peninsula ◽  
Coastal Sea ◽  
Temperature Records

Registros costeros de temperatura superficial del mar en la Península de Baja California El análisis de series ambientales de temperatura de alta resolución temporal en las zonas costeras permitirá caracterizar mejor las formas y escalas de variación. Las bases de datos disponibles actualmente carecen de suficiente resolución para detectar variaciones ambientales a escalas de horas y días. En este trabajo damos a conocer una colección de registros de alta frecuencia de diversos sitios a lo largo de las costas de la Península de Baja California. Hasta el momento se tienen 47 sitios; sin embargo, esta red de monitoreo pretende expandirse con el objetivo de generar bases de datos de acceso público y gratuito, proporcionando una valiosa herramienta no solo para la investigación, sino también para aplicaciones como la producción acuícola.

A Transfer Function Analysis of a Geomagnetic Depth Sounding-Profile across Central British Columbia

1973 ◽  
Vol 10 (7) ◽  
pp. 1089-1098 ◽  
Author(s):  
H. Dragert
Keyword(s):  
British Columbia ◽  
Transfer Functions ◽  
Function Analysis ◽  
Three Dimensional ◽  
Vertical Component ◽  
Rocky Mountain ◽  
Three Dimensional Model ◽  
Transfer Function Analysis ◽  
Single Station ◽  
Depth Sounding

Time variations of the geomagnetic field observed across British Columbia at a mean latitude of 54 °N are analyzed using 'single-station' and 'paired-station' optimum transfer functions. The frequency and spatial dependence of both coastal and inland geomagnetic anomalies are estimated with the following results. (1) The normal coast effect is strongly perturbed by lateral conductivity inhomogeneities both north and south of the profile. (2) A simple, single NW–SE striking conductivity contrast between the Cordillera and plains cannot account for the total geomagnetic anomaly in the area of the Rocky Mountain Trench; a three-dimensional model is required, incorporating (i) a lateral inhomogeneity striking east–west and located to the south of the profile, (ii) the effect of induction by the vertical component of source or secondary fields.

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