The upwelling regime off the West Portuguese Coast, 1941–2000

Lemos, Ricardo T.; Pires, Henrique Oliveira

doi:10.1002/joc.1009

Cited by 131 publications

(119 citation statements)

References 14 publications

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“…just after the Little Ice Age. Recent research suggests that the Portuguese coastal upwelling regime has weakened since the 1940s (Lemos and Pires 2004).…”

Section: Resultsmentioning

confidence: 99%

Coastal Upwelling and Radiocarbon—Evidence for Temporal Fluctuations in Ocean Reservoir Effect off Portugal During the Holocene

Soares¹,

Dias²

2006

Radiocarbon

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ABSTRACT. This paper focuses on the use of the radiocarbon content of marine shells collected along the Portuguese coast as a proxy for the intensity of coastal upwelling off of Portugal. Differences in the 14 C ages of closely associated marine mollusk shells and terrestrial material (charcoal or bones) from several Portuguese archaeological contexts seem to be significant throughout the Holocene. ∆R values range from 940 ± 50 to -160 ± 40 14 C yr. Five of these values are significantly higher than the modern value (250 ± 25 14 C yr), while the remaining values are lower. The modern value was calculated by measuring the 14 C content of live-collected, pre-bomb marine mollusk shells. This value is in accordance with an active upwelling of strong intensity that currently occurs off of Portugal. Some primary observations based on data presented here can be made: i) during the Holocene important changes have occurred in the ocean reservoir effect off the Portuguese coast; ii) these fluctuations may be correlated with regional oceanographic changes, namely with changes in the strength of coastal upwelling; and iii) these changes suggest some sort of variability of the climatic factors forcing coastal upwelling off of Portugal.

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“…just after the Little Ice Age. Recent research suggests that the Portuguese coastal upwelling regime has weakened since the 1940s (Lemos and Pires 2004).…”

Section: Resultsmentioning

confidence: 99%

Coastal Upwelling and Radiocarbon—Evidence for Temporal Fluctuations in Ocean Reservoir Effect off Portugal During the Holocene

Soares¹,

Dias²

2006

Radiocarbon

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“…However, Lemos and Pires (2004) find a decrease in coastal upwelling intensity off the coast of Portugal in the later part of the 20th century. Furthermore, Dunbar (1983) suggests a decrease of upwelling between 1850 and the present.…”

Section: Introductionmentioning

confidence: 84%

Trends in coastal upwelling intensity during the late 20th century

et al. 2010

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Abstract. This study presents linear trends of coastal upwelling intensity in the later part of the 20th century employing various indices of upwelling, derived from meridional wind stress and sea surface temperature. The analysis was conducted in the four major coastal upwelling regions in the world, which are off North-West Africa, Lüderitz, California and Peru. The trends in meridional wind stress showed a steady increase of intensity from 1960-2001, which was also reflected in the SST index calculated for the same time period. The steady cooling observed in the instrumental records of SST off California substantiated this observation further. It was also noted that the trends in meridional wind stress obtained from different datasets differ substantially from each other. Correlation analysis showed that basin-scale oscillations like the Atlantic Multidecadal Oscillation (AMO) and the Pacific Decadal Oscillation (PDO) could not be directly linked to the observed increase of upwelling intensity off NW Africa and California respectively. The relationship of the North Atlantic Oscillation (NAO) with coastal upwelling off NW Africa turned out to be ambiguous due to a negative correlation between the NAO index and the meridional wind stress and a lack of correlation with the SST index. Our results give additional support to the hypothesis that the coastal upwelling intensity increases globally because of raising greenhouse gas concentrations in the atmosphere and an associated increase of the land-sea pressure gradient and meridional wind stress.

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“…The available hard substrate is a mixture of granite greywacke and schist. The tidal regime is semidiurnal, with the largest spring tides of 3.5-4.0 m. Moreover, the studied area is subjected to a seasonal upwelling during spring and summer months that provides nutrient supply for primary producers (Lemos and Pires 2004).…”

Section: Study Areamentioning

confidence: 99%

Spatial variability in intertidal macroalgal assemblages on the North Portuguese coast: consistence between species and functional group approaches

et al. 2012

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Natural assemblages are variable in space and time; therefore, quantification of their variability is imperative to identify relevant scales for investigating natural or anthropogenic processes shaping these assemblages. We studied the variability of intertidal macroalgal assemblages on the North Portuguese coast, considering three spatial scales (from metres to 10 s of kilometres) following a hierarchical design. We tested the hypotheses that (1) spatial pattern will be invariant at all the studied scales and (2) spatial variability of macroalgal assemblages obtained by using species will be consistent with that obtained using functional groups. This was done considering as univariate variables: total biomass and number of taxa as well as biomass of the most important species and functional groups and as multivariate variables the structure of macroalgal assemblages, both considering species and functional groups. Most of the univariate results confirmed the first hypothesis except for the total number of taxa and foliose macroalgae that showed significant variability at the scale of site and area, respectively. In contrast, when multivariate patterns were examined, the first hypothesis was rejected except at the scale of 10 s of kilometres. Both uni-and multivariate results indicated that variation was larger at the smallest scale, and thus, smallscale processes seem to have more effect on spatial variability patterns. Macroalgal assemblages, both considering species and functional groups as surrogate, showed consistent spatial patterns, and therefore, the second hypothesis was confirmed. Consequently, functional groups may be considered a reliable biological surrogate to study changes on macroalgal assemblages at least along the investigated Portuguese coastline.

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The upwelling regime off the West Portuguese Coast, 1941–2000

Cited by 131 publications

References 14 publications

Coastal Upwelling and Radiocarbon—Evidence for Temporal Fluctuations in Ocean Reservoir Effect off Portugal During the Holocene

Coastal Upwelling and Radiocarbon—Evidence for Temporal Fluctuations in Ocean Reservoir Effect off Portugal During the Holocene

Trends in coastal upwelling intensity during the late 20th century

Spatial variability in intertidal macroalgal assemblages on the North Portuguese coast: consistence between species and functional group approaches

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