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Open AccessArticle

A 60-Year Time Series Analyses of the Upwelling along the Portuguese Coast

1
Campus de Gambelas, Centro de Ciências do Mar (CCMAR), Universidade do Algarve, 8005-139 Faro, Portugal
2
MARETEC, Instituto Superior Técnico, Universidade de Lisboa, Av Rovisco Pais, 1049-001 Lisboa, Portugal
*
Author to whom correspondence should be addressed.
Water 2019, 11(6), 1285; https://doi.org/10.3390/w11061285
Received: 24 March 2019 / Revised: 25 May 2019 / Accepted: 12 June 2019 / Published: 20 June 2019
(This article belongs to the Special Issue Satellite Remote Sensing and Analyses of Climate Variability)
Coastal upwelling has a significant local impact on marine coastal environment and on marine biology, namely fisheries. This study aims to evaluate climate and environmental changes in upwelling trends between 1950 and 2010. Annual, seasonal and monthly upwelling trends were studied in three different oceanographic areas of the Portuguese coast (northwestern—NW, southwestern—SW, and south—S). Two sea surface temperature datasets, remote sensing (RS: 1985–2009) and International Comprehensive Ocean—Atmosphere Data Set (ICOADS: 1950–2010), were used to estimate an upwelling index (UPWI) based on the difference between offshore and coastal sea surface temperature. Time series analyses reveal similar yearly and monthly trends between datasets A decrease of the UPWI was observed, extending longer than 20 years in the NW (1956–1979) and SW (1956–1994), and 30 years in the S (1956–1994). Analyses of sudden shifts reveal long term weakening and intensification periods of up to 30 years. This means that in the past 60 years a normal climate UPWI occurred along the Portuguese coast. An intensification of UPWI was recorded in recent decades regardless of the areas (RS: 1985–2009). Such an intensification rate (linear increase in UPWI) is only significant in S in recent decades (increase rate: ICOADS = 0.02 °C decade-1; RS = 0.11 °C decade-1) while in NW and SW the increase rate is meaningless. In NW more stable UPWI conditions were recorded, however average UPWI values increased in autumn and winter in NW in recently decades (RS: 1985–2009). An intensification rate of UPWI was recorded during summer (July, August and September) in SW and S in latter decades (RS: 1985–2009). The average UPWI values increased in recent decades in autumn in S. Marked phenological changes were observed in S in summer (before downwelling conditions prevail whilst recently when UPWI regimes prevail) with UPWI seasonal regime in S in recent decades becoming similar to those found in SW and NW. Results of this work can contribute to a better understanding of how upwelling dynamics affect/are correlated with biological data. View Full-Text
Keywords: Iberian Portuguese coast; climate normal; sudden shifts; upwelling trends; seasonal changes Iberian Portuguese coast; climate normal; sudden shifts; upwelling trends; seasonal changes
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Leitão, F.; Baptista, V.; Vieira, V.; Laginha Silva, P.; Relvas, P.; Alexandra Teodósio, M. A 60-Year Time Series Analyses of the Upwelling along the Portuguese Coast. Water 2019, 11, 1285.

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