Continental microseismic intensity delineates oceanic upwelling timing along the west coast of North America

Thomson, Richard E.; Martin, Henno; Davis, Earl E.; Hourston, Roy A. S.

doi:10.1002/2014gl061241

Cited by 22 publications

(19 citation statements)

References 36 publications

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“…Regime 3 encompasses the waters to the south and west of Vancouver Island (zones BC1, BC2, and BC7) and the Washington coast (US1). In this regime, the spring bloom typically starts in March, which is within the range of the mean onset time for the Spring Transition in the region [ Thomson et al ., ]. All four zones in regime 3 are characterized by high surface chlorophyll concentrations from April until the beginning of November.…”

Section: Discussionmentioning

confidence: 99%

“…Because the prevailing winds are most upwelling favorable from June through September, results indicate that surface phytoplankton on the northwest coast of Vancouver Island are more dependent on wind‐induced upwelling than at other coastal regions of British Columbia. The high phytoplankton concentrations on the southwest coast of Vancouver Island in April through June are likely associated with onset of upwelling favorable winds following the Spring Transition in April [ Thomson et al ., ], the seasonally high discharges from the Fraser and/or Columbia Rivers at this time, and the seaward flux of brackish low salinity surface water through Juan de Fuca Strait near the time of monthly neap tides [cf., Griffin and LeBlond , ; Masson and Cummins , ; Hickey and Banas , ]. The seaward transport of brackish water leads to a high nutrient flux to the outer coast and enhanced productivity on the continental shelf [ Dewey and Crawford , ; Foreman et al ., ; MacFayden and Hickey , ].…”

Section: Discussionmentioning

confidence: 99%

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Satellite chlorophyll off the British Columbia Coast, 1997-2010

Jackson

Thomson

Brown

et al. 2015

J. Geophys. Res. Oceans

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We examine the spatial and temporal variability of satellite-sensed sea surface chlorophyll off the west coast of North America from 1997 to 2010, with focus on coastal British Columbia. The variability in surface chlorophyll is complex. Whereas the spring bloom generates the highest phytoplankton concentration for coastal Alaska, the north and east coasts of Haida Gwaii, Queen Charlotte Sound, the Strait of Georgia, and coastal Oregon and California, it is the fall bloom that normally generates the highest concentration for the west coast of Vancouver Island, Juan de Fuca Strait, and the west coast of Washington. The highest satellite-sensed chlorophyll concentrations occur in the Strait of Georgia, where mean values are at least 2 times higher than elsewhere in the northeast Pacific. Moreover, the annual average surface chlorophyll concentration increased significantly in the Strait of Georgia during this period, with highest concentration observed during the near neutral ENSO conditions of the spring of 2007. The next highest concentrations occur off southwest Vancouver Island but have no statistically significant trend. The lowest average peak chlorophyll concentration is observed off Southern California. The timing of the highest chlorophyll concentration is latest off the coast of Washington and earliest off the coast of Southern California. Small increasing concentration trends are observed off the Washington and California coasts.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Satellite chlorophyll off the British Columbia Coast, 1997-2010

Jackson

Thomson

Brown

et al. 2015

J. Geophys. Res. Oceans

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“…Based on our 7 years of observation at site A1, the undercurrent is absent sometime between early March and late May, which brackets the period of the spring transition (early April ± 1 month) reported by Thomson et al . [] for the west coast of British Columbia and Washington. The undercurrent is reestablished following the spring transition and typically strengthens through summer to early fall.…”

Section: Discussionmentioning

confidence: 99%

“…Consistent with previous studies, the canonical annual flow in the upper layer at A1 is dominated by the equatorward flowing shelf‐break current in summer and the poleward flowing Davidson Current in winter [ Thomson et al ., ; Hickey et al ., ]. The shelf‐break current forms around the time of the spring transition in mid‐April (±1 month) [ Thomson et al ., ], when prevailing winds off the British Columbia‐Washington coast switch from southerly (downwelling favorable) to northerly (upwelling favorable). Formation of the Davidson Current follows the return to southerly winds after the fall transition in mid‐October (±1 month).…”

Section: Wind and Current Variabilitymentioning

confidence: 99%

Remote alongshore winds drive variability of the California Undercurrent off the British Columbia‐Washington coast

Thomson

Krassovski²

2015

JGR Oceans

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The California Undercurrent transports warm, salty, nutrient‐rich, oxygen‐depleted water along the continental slope from the equatorial Pacific to the Aleutian Islands. We use multiyear acoustic Doppler current profiler records collected simultaneously at two mooring sites off Vancouver Island to detail the regional structure of the undercurrent and to show that much of its variability is attributable to the passage of remotely forced, coastal‐trapped waves. We also document two subsurface currents missed by earlier current measurements. The undercurrent becomes evident in spring, intensifies through summer and fall, and merges with the wind‐driven poleward surface flow in winter. During intensification at the southern mooring site (A1), the undercurrent shoals from 250 ± 50 m in early summer to 150 ± 50 m depth in late fall. At the northern site (BP2), 225 km to the northwest of A1, the current is weaker and maintains a year‐round depth of 150 ± 50 m. Temporal variability in the undercurrent velocity attains highest coherence with winds along the southern Oregon‐northern California coast, with peak coherence occurring for “synoptic” (10–40 day period) alongshore winds off Cape Blanco in southern Oregon. The undercurrent lag of 3 ± 2 days relative to the Cape Blanco winds at synoptic periods is consistent with low mode, poleward propagating, coastally trapped waves. For periods >40 days, the wind‐current coherence remains high for winds off the Oregon‐California coast but lags are often negative, indicating possible forcing by alongshore baroclinic pressure gradients. At interannual time scales, the undercurrent variations have links to climate‐scale processes in the equatorial Pacific.

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“…Maximum SST (∼ 18 • C) are observed in the summer, covering much of the Strait of Georgia. The impact of coastal upwellings on the SST spatial structure can be observed along Vancouver Island during the summer and fall seasons due to a shift of dominant winds (Cummins and Masson 2014;Thomson et al 2014). Relatively low SST can also be observed in Queen Charlotte Strait and Juan de Fuca Strait.…”

Section: Northeastern Pacificmentioning

confidence: 99%

Canadian Coastal Seas and Great Lakes Sea Surface Temperature Climatology and Recent Trends

Larouche

Galbraith

2016

Canadian Journal of Remote Sensing

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28 years of satellite data were used to calculate sea surface temperature (SST) climatologies covering Canada's 3 surrounding oceans and the Great Lakes. Results show the imprint of major circulation features on the spatial distribution of the SST. Together with the Gulf Stream, the Labrador Current generates a strong spatial variability of SST on the east coast. Most of the Canadian Arctic, with the exception of Hudson Bay and the coastal Beaufort Sea region, is characterized by very small seasonal SST amplitude. Lake Erie is the water body having the largest seasonal SST amplitude, but for the oceanic regions, it is the southern Gulf of St. Lawrence and the adjacent Scotian Shelf. A trend analysis showed that many regions are undergoing rapid warming of the sea surface. However, warming is not spatially uniform. The strongest warming was detected in Baffin Bay and appears to result from the decreasing ice cover. Lake Superior is also showing a strong warming trend. These results have important implications for fisheries management because SST affects many species. Regions with small yearly amplitudes and warming trends might act as future cool water oases for some species. Résumé. 28 années de données satellitaires ontété utilisées afin de calculer des climatologies des températures de surface de la mer «sea surface temperature» (SST) pour les 3 océans entourant le Canada ainsi que pour les Grands Lacs. Les résultats montrent l'empreinte des principaux courants océaniques sur la distribution spatiale des SST. Avec le Gulf Stream, le courant duLabrador génère une forte variabilité spatiale des SST sur la côte est. La plupart de l'arctique canadien, avec l'exception de la Baie d'Hudson et la zone côtière de la mer de Beaufort, est caractérisé par une très faible amplitude annuelle des SST. Le lacÉrié est la masse d'eau montrant la plus grande amplitude saisonnière, mais pour les régions océaniques, ce sont le sud du Golfe du Saint-Laurent et le plateau Néo-Écossais adjacent. Une analyse de tendances a montré que plusieurs régions sont soumisesà un accroissement rapide des températures de surface. Toutefois, le réchauffement n'est pas spatialement uniforme. Le plus fort réchauffement aété détecté dans la baie de Baffin et semble reliéà la décroissance de la couverture de glace. Le lac Supérieur montre aussi une forte tendance au réchauffement. Ces résultats ont d'importantes implications pour la gestion des pêches puisque la SST affecte plusieurs espèces. Les régions ayant une faible amplitude annuelle et un faible taux de réchauffement pourraient agir dans le futur comme des oasis froides pour certaines espèces.

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Continental microseismic intensity delineates oceanic upwelling timing along the west coast of North America

Cited by 22 publications

References 36 publications

Satellite chlorophyll off the British Columbia Coast, 1997-2010

Satellite chlorophyll off the British Columbia Coast, 1997-2010

Remote alongshore winds drive variability of the California Undercurrent off the British Columbia‐Washington coast

Canadian Coastal Seas and Great Lakes Sea Surface Temperature Climatology and Recent Trends

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