Filaments on the Western Iberian Margin: A modeling study

Abstract

Coastal upwelling filaments off the Western Iberian Margin, detected in AVHRR satellite imagery and in a realistic ROMS simulation of sea surface temperature, were studied in the upwelling seasons (May-October) of [2001][2002][2003][2004][2005][2006][2007][2008][2009][2010]. Sea surface temperature data were retrieved from AVHRR satellite imagery and from a realistic ROMS numerical simulation. The development and variability of the observed filaments were characterized and analyzed during each upwelling season of the 10 year period. Filaments were generally found anchored to the main bathymetric and coastal features but off the more regular northern coast of the Western Iberian Margin their locations were more variable. The results from the modeling analysis reproduced well the general features of filament development. Moreover results of model and observation showed very similar characteristics as those found in the earlier study of Haynes et al. (1993). The model output was used to relate filament patterns, eddy activity, and wind forcing. There was a clear relation between upwelling-favorable wind strength and number and length of filaments, although the relation was weaker in the north of the region. Model filaments were clearly related to eddies only during periods of weak winds. The filament detection method was also applied to a climatologically forced ROMS simulation, which reproduced only gross features of the observed and interannually forced model filament development. This suggests that direct wind forcing and its spatial structure are highly important.

Independent estimates of marine population connectivity are more concordant when accounting for uncertainties in larval origins

“…In the second (3 × 4) and third (4 × 4) scenarios we kept the Cascais and the Arrábida bay regions, but made a distinction between the Estremadura North and South sections, separated by Cape Carvoeiro. This major cape induces strong and recurrent filament activities in response to upwelling events, which affect local oceanography and decouple to some degree both sections of the coast 86 , 94 . In the second scenario we expect a common natal signature for the whole Estremadura coast, but distinct settlement zones (Estremadura North and South) due to a two-cell circulation caused by the topographic influence of the cape.…”

Environmental Factors Affecting Spatial Dinoflagellate Cyst Distribution in Surface Sediments Off Aveiro-Figueira da Foz (Atlantic Iberian Margin)

“…The interpretation of the heterotroph dominance as an upwelling signal is preferred to other nutrient enrichment processes, such as nutrient loads from river input, since this would also promote increased stratification which would favor autotrophic dinoflagellates relative to other non-flagellated groups such as diatoms. The latitudinal gradient on heterotrophic dominance (higher abundance in northern sites) can at least partially be explained by a recurrent upwelling front observed on the shelf north of the study site, offshore the Douro estuary (e.g., Haynes et al, 1993;Cordeiro et al, 2015), and the coincidence with a zone of higher upwelling probability (Figure 1C; Relvas et al, 2007), i.e., the greater abundances of heterotrophic cysts in northern samples responding to increased productivity (Figure 9B).…”

Observed cold filaments associated with mesoscale eddies in the South China Sea

“…The methodology used for SST or Chl a concentration filament identification is similar to the procedure described by Haynes et al [1993] and Cordeiro et al [2015], which mainly consists of two procedures: first, the pixels with an SST (Chl a) meridional gradient higher than 0.038C/km (0.001 mg m 23 /km) are marked on each SST (Chl a) image, in order to highlight frontal regions. It should be noted that the threshold of 0.038C/ km (0.001 mg m 23 /km) was reached empirically.…”