Time series analysis of data for sea surface temperature and upwelling components from the southwest coast of Portugal

Abstract This study relates sea surface temperature (SST) to the upwelling conditions off the southwest coast of Portugal using statistical analyses of publically available data. Optimum Interpolation (OI) of daily SST data were extracted from the United States (US) National Oceanic and Atmospheric Administration (NOAA) and data for wind speed and direction were from the US National Climatic Data Center. Time series were extracted at a daily frequency for a time horizon of 26 years. Upwelling indices were estimated using westerly (Qx) and southerly (Qy) Ekman transport components. In the first part of the study, time series were inspected for trend and seasonality over the whole period. The seasonally adjusted time series revealed an increasing slope for SST (0.15 °C per decade) and decreasing slopes for Qx (− 84.01 m3 s− 1 km− 1 per decade) and Qy (− 25.20 m3 s− 1 km− 1 per decade), over the time horizon. Structural breaks analysis applied to the time series showed that a statistically significant incremental increase in SST was more pronounced during the last decade. Cross-correlation between upwelling indices and SST revealed a time delay of 5 and 2 days between Qx and SST, and between Qy and SST, respectively. A spectral analysis combined with the previous analysis enabled the identification of four oceanographic seasons. Those seasons were later recognised over a restricted time period of 4 years, between 2008 and 2012, when there was an extensive sampling programme for the validation of ocean colour remote sensing imagery. The seasons were defined as: summer, with intense and regular events of upwelling; autumn, indicating relaxation of upwelling conditions; and spring and winter, showing high interannual variability in terms of number and intensity of upwelling events.

[1]  J. Hansen,et al.  GLOBAL SURFACE TEMPERATURE CHANGE , 2010 .

[2]  P. Oliveira,et al.  Surface temperature, chlorophyll and advection patterns during a summer upwelling event off central Portugal. , 2009 .

[3]  H. Wanner,et al.  A review of non-stationarities in climate variability of the last century with focus on the North Atlantic–European sector , 2015 .

[4]  R Core Team,et al.  R: A language and environment for statistical computing. , 2014 .

[5]  R. Weller,et al.  Wind-Driven Ocean Currents and Ekman Transport , 1987, Science.

[6]  E. Serrão,et al.  Shift happens: trailing edge contraction associated with recent warming trends threatens a distinct genetic lineage in the marine macroalga Fucus vesiculosus , 2013, BMC Biology.

[7]  James C. McWilliams,et al.  The Warming of the California Current System: Dynamics and Ecosystem Implications , 2005 .

[8]  Priscila Goela,et al.  Using CHEMTAX to evaluate seasonal and interannual dynamics of the phytoplankton community off the South-west coast of Portugal , 2014 .

[9]  F. Mélin,et al.  Temporal variability in SeaWiFS derived apparent optical properties in European seas , 2010 .

[10]  M. Gómez-Gesteira,et al.  Present warming within the context of cooling–warming cycles observed since 1854 in the Bay of Biscay , 2009 .

[11]  Esther Garcés,et al.  Harmful algal blooms (HABs), dissolved organic matter (DOM), and planktonic microbial community dynamics at a near-shore and a harbour station influenced by upwelling (SW Iberian Peninsula) , 2011 .

[12]  Priscila Goela,et al.  In situ validation of MERIS marine reflectance off the southwest Iberian Peninsula: assessment of vicarious adjustment and corrections for near-land adjacency , 2014 .

[13]  Richard J. Greatbatch,et al.  The North Atlantic Oscillation , 2000 .

[14]  S. V. Cristinat,et al.  Assessment of Water-Leaving Reflectances of Oceanic and Coastal Waters Using MERIS Satellite Products off the Southwest Coast of Portugal , 2009 .

[15]  Rosalia Santoleri,et al.  Combining model and geostationary satellite data to reconstruct hourly SST field over the Mediterranean Sea , 2014 .

[16]  M. Gómez-Gesteira,et al.  Changes in sea surface temperature seasonality in the Bay of Biscay over the last decades (1982–2014) , 2015 .

[17]  Antoine Mangin,et al.  Variability of suspended particulate matter concentration in coastal waters under the Mekong's influence from ocean color (MERIS) remote sensing over the last decade , 2014 .

[18]  D. Wethey,et al.  Three decades of high-resolution coastal sea surface temperatures reveal more than warming , 2012, Nature Communications.

[19]  R. Haynes,et al.  Development, persistence, and variability of upwelling filaments off the Atlantic coast of the Iberian Peninsula , 1993 .

[20]  M. N. Lorenzo,et al.  Trends of the Galician upwelling in the context of climate change , 2014 .

[21]  P. Relvas,et al.  Spring–summer climatological circulation in the upper layer in the region of Cape St. Vincent, Southwest Portugal , 2003 .

[22]  A. Newton,et al.  Using bio-optical parameters as a tool for detecting changes in the phytoplankton community (SW Portugal) , 2015 .

[23]  Bruno Sansó,et al.  Spatio‐temporal variability of ocean temperature in the Portugal Current System , 2006 .

[24]  Chris Chatfield,et al.  The Analysis of Time Series: An Introduction , 1981 .

[25]  S. Delurgio.  Forecasting Principles and Applications , 1998 .

[26]  Alexandre M. Ramos,et al.  The use of circulation weather types to predict upwelling activity along the western Iberian Peninsula coast , 2013 .

[27]  M. I. Barão,et al.  Can Pseudo-nitzschia blooms be modeled by coastal upwelling in Lisbon Bay? , 2010 .

[28]  A Bakun,et al.  Global Climate Change and Intensification of Coastal Ocean Upwelling , 1990, Science.

[29]  M. Gómez-Gesteira,et al.  Spatiotemporal evolution of upwelling regime along the western coast of the Iberian Peninsula , 2008 .

[30]  Raj Kumar,et al.  Long-term variability in Arctic sea surface temperatures , 2013 .

[31]  P. Miranda,et al.  Variability of Iberian upwelling implied by ERA-40 and ERA-Interim reanalyses , 2013 .

[32]  A. Bakun,et al.  Coastal Upwelling Indices, West Coast of North America, 1946-71 , 2018 .

[33]  P. Minnett,et al.  Evidence linking satellite-derived sea-surface temperature signals to changes in the Atlantic meridional overturning circulation , 2015 .

[34]  Warren S. Wooster,et al.  SEASONAL UPWELLING CYCLE ALONG THE EASTERN BOUNDARY OF THE NORTH ATLANTIC. , 1976 .

[35]  F. Muller‐Karger,et al.  Interannual Variability in Sea Surface Temperature and Fco2 Changes in the Cariaco Basin , 2013 .

[36]  Peter M. Atkinson,et al.  Looking back and looking forwards: Historical and future trends in sea surface temperature (SST) in the Indo-Pacific region from 1982 to 2100 , 2016, Int. J. Appl. Earth Obs. Geoinformation.

[37]  S. Lluch-Cota,et al.  Coastal upwelling in the eastern Gulf of California , 2000 .

[38]  D. Pauly,et al.  Primary production required to sustain global fisheries , 1995, Nature.

[39]  M. Schulz,et al.  Trends in coastal upwelling intensity during the late 20th century , 2010 .

[40]  Eric D. Barton,et al.  Mesoscale patterns in the Cape São Vicente (Iberian Peninsula) upwelling region , 2002 .

[41]  Priscila Goela,et al.  Specific absorption coefficient of phytoplankton off the Southwest coast of the Iberian Peninsula: A contribution to algorithm development for ocean colour remote sensing , 2013 .

[42]  Vincent Vantrepotte,et al.  Inter-annual variations in the SeaWiFS global chlorophyll a concentration (1997–2007) , 2011 .

[43]  Annick Bricaud,et al.  Satellite-derived phytoplankton pigment structures in the Portuguese upwelling area , 1992 .

[44]  R. T. Lemos,et al.  The upwelling regime off the West Portuguese Coast, 1941–2000 , 2004 .

[45]  Davide D'Alimonte,et al.  Multi-sensor satellite time series of optical properties and chlorophyll- a concentration in the Adriatic Sea , 2011 .

[46]  Achim Zeileis,et al.  Strucchange: An R package for testing for structural change in linear regression models , 2002 .

[47]  F. Sousa,et al.  Identification of upwelling areas on sea surface temperature images using fuzzy clustering , 2008 .

[48]  Y. Kaska,et al.  Nest temperatures in a loggerhead nesting beach in Turkey is more determined by sea surface than air temperature. , 2015, Journal of thermal biology.

[49]  F. G. Figueiras,et al.  Renewal time and the impact of harmful algal blooms on the extensive mussel raft culture of the Iberian coastal upwelling system (SW Europe) , 2008 .

[50]  Priscila Goela,et al.  Using remote sensing as a support to the implementation of the European Marine Strategy Framework Directive in SW Portugal , 2015 .

[51]  Thomas M. Smith,et al.  Daily High-Resolution-Blended Analyses for Sea Surface Temperature , 2007 .

[52]  John Icely,et al.  Microplankton composition, production and upwelling dynamics in Sagres (SW Portugal) during summer of 2001 , 2005 .

[53]  H. L. Miller,et al.  Climate Change 2007: The Physical Science Basis , 2007 .

[54]  G. T. Wilson,et al.  Models for Dependent Time Series , 2015 .

[55]  G. Bigg,et al.  Spatial and temporal seasonal trends in coastal upwelling off Northwest Africa, 1981-2012 , 2014 .

[56]  Guerreiro,et al.  Climatological space and time-variation of the portuguese coastal upwelling , 1982 .