Data from the National Oceanic and Atmospheric Administration (NOAA) and Topography Experiment (TOPEX)JPoseidon (TJP) satellites, a surface drifter, and subsurface floats, named RAFOS, at a depth of -1000 m in the Mediterranean... more
Data from the National Oceanic and Atmospheric Administration (NOAA) and Topography Experiment (TOPEX)JPoseidon (TJP) satellites, a surface drifter, and subsurface floats, named RAFOS, at a depth of -1000 m in the Mediterranean Undercurrent were used to investigate Mediterranean Water eddies, or meddies, off the southwest coast of Portugal. Analysis of RAFOS trajectories and simultaneous distributions of NOAA Advanced Very-High Resolution
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Abstract Physical oceanography is increasingly relying on satellite remote sensing to survey the perpetually undersampled ocean, whereas the latest Synthetic Aperture Radars (SARs) are moving forward to provide a more continuous... more
Abstract Physical oceanography is increasingly relying on satellite remote sensing to survey the perpetually undersampled ocean, whereas the latest Synthetic Aperture Radars (SARs) are moving forward to provide a more continuous monitoring of the ocean. In this study we use a collection of SAR images to document the two-dimensional horizontal structure of Internal Solitary Waves (ISWs) propagating between two large submarine canyons off the Western Iberian Peninsula (between May and October 2018), which are observed to intersect approximately along the mid-shelf and originate a naturally-occurring interaction hotspot between different ISW packets. ISW interactions are well documented in theory and in laboratorial and numerical studies, but their observations in the real ocean are limited to airborne observations over the Strait of Georgia. The frequent SAR imagery of interacting ISWs in this region provides additional case studies to the literature, and we investigate if an energy proxy taken from their sea surface signatures can be used as an indicator for high-energy interaction events (e.g. when comparing with a non-interacting background). In particular, a quasi-synergetic event captured both in SAR and in a moored thermistor chain reveals that the often used weakly nonlinear theory for small-amplitude waves may underestimate the amplitudes measured in the waves’ interacting sections. ISWs provide the largest vertical displacements and velocities in the ocean. Understating how their vertical structure changes during wave-wave interactions may have important implications in the broader spectrum of ocean sciences, and SARs are shown in this study to be a first-approach tool to survey this frequent phenomenon in coastal regions.
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Dinophysis acuta, which is responsible for diarrhetic shellfish poisoning, reached particularly high concentrations on the north-west coast of Portugal in 2003. In the Ría de Aveiro (40°41'N), the species reached a maximum... more
Dinophysis acuta, which is responsible for diarrhetic shellfish poisoning, reached particularly high concentrations on the north-west coast of Portugal in 2003. In the Ría de Aveiro (40°41'N), the species reached a maximum concentration of 5.0 × 104 cells l−1 on 8 September, the highest value in a 17-year record of monitoring. The bloom followed a brief period of upwelling-favourable winds, at the end of an extremely hot summer marked by weak upwelling, thereby favouring the development of highly stratified conditions. In mid-September, during a cruise transecting the shelf 30km south of Aveiro, a subsurface maximum of D. acuta was identified by fluorescence, with cell concentrations exceeding 2.4 × 104 cells l−1. The species was restricted to a relatively thin layer of 5m (with maxima between 18m and 20m depth) within the pycnocline extending 30km offshore. Cross-shelf distributions revealed the presence of two smaller forms of D. acuta, the smallest of which was identified as D. dens. Their coincident distribution with that of D. acuta reinforced the supposition that these smaller forms correspond to different life-cycle stages of D. acuta, with D. dens representing a gamete of D. acuta. The high cell concentrations in the thin layer are thought to embody a species' strategy to ensure successful gamete mating during sexual reproduction.
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Quantitative and qualitative analyses of planktonic foraminiferal assemblages from 134 core-top sediment samples collected along the western Iberian margin were used to assess the latitudinal and longitudinal changes in surface water... more
Quantitative and qualitative analyses of planktonic foraminiferal assemblages from 134 core-top sediment samples collected along the western Iberian margin were used to assess the latitudinal and longitudinal changes in surface water conditions and to calibrate a Sea Surface Temperature (SST) transfer function for this seasonal coastal upwelling region. Q-mode factor analysis performed on relative abundances yielded three factors that explain 96% of the total variance: factor 1 (50%) is exclusively defined by Globigerina bulloides, the most abundant and widespread species, and reflects the modern seasonal (May to September) coastal upwelling areas; factor 2 (32%) is dominated by Neogloboquadrina pachyderma (dextral) and Globorotalia inflata and seems to be associated with the Portugal Current, the descending branch of the North Atlantic Drift; factor 3 (14%) is defined by the tropical-sub-tropical species Globigerinoides ruber (white), Globigerinoides trilobus trilobus, and G. inflata and mirrors the influence of the winter-time eastern branch of the Azores Current. In conjunction with satellite-derived SST for summer and winter seasons integrated over an 18 year period the regional foraminiferal data set is used to calibrate a SST transfer function using Imbrie & Kipp, MAT and SIMMAX(ndw) techniques. Similar predicted errors (RMSEP), correlation coefficients, and residuals' deviation from SST estimated for both techniques were observed for both seasons. All techniques appear to underestimate SST off the southern Iberia margin, an area mainly occupied by warm waters where upwelling occurs only occasionally, and overestimate SST on the northern part of the west coast of the Iberia margin, where cold waters are present nearly all year round. The comparison of these regional calibrations with former Atlantic and North Atlantic calibrations for two cores, one of which is influenced by upwelling, reveals that the regional one attests more robust paleo-SSTs than for the other approaches.
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Research Interests: Oceanography, MODIS, Internal Wave, SAR, Marine Systems, and 3 moreBay of Biscay, Internal waves, and Bay
High-resolution acoustic and ichtyoplankton sampling with a 'continuous under-way fish egg sampler (CUFES)' was performed in two regions of approximately 100 square nautical miles off southern Iberian Peninsula, with the... more
High-resolution acoustic and ichtyoplankton sampling with a 'continuous under-way fish egg sampler (CUFES)' was performed in two regions of approximately 100 square nautical miles off southern Iberian Peninsula, with the aim of studying the small scale distribution of ...
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ABSTRACT Velocity measurements from 4 bottom-mounted ADCP deployments (summers of 2006, 2007, 2008 and 2011) at a 12-m depth site off Sines, Portugal, complemented with time series of winds, waves and tides, are used to study the... more
ABSTRACT Velocity measurements from 4 bottom-mounted ADCP deployments (summers of 2006, 2007, 2008 and 2011) at a 12-m depth site off Sines, Portugal, complemented with time series of winds, waves and tides, are used to study the inner-shelf cross-shore flow dependence on wave, tidal and wind forcings. During these four summers, the dominating winds are from the north (upwelling-favorable), with strong diurnal sea breeze cycle throughout these periods. This quasi-steady wind circulation is sometimes interrupted by short event-like reversals. The observed records were split in different subsets according to tidal amplitude, wave height, cross- and along-shore wind magnitudes, and the vertical structure of the cross-shore flow was studied for each of these subsets. Despite different forcing conditions, the cross-shore velocity profiles usually show a vertical parabolic structure with maximum onshore flow at mid-depth, resembling the upwelling return flow for mid-shelf conditions, but atypical for the inner-shelf and in disagreement with other inner-shelf studies from other sites. We compare the observations with simplified 2D inner-shelf models and with results from other studies.
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An analysis of NOAA/AVHRR II sea surface temperatures (SST) and NIMBUS-7/CZCS phytoplankton pigment concentrations was conducted in order to characterize their mean distributions and their space-time variability in the eastern North... more
An analysis of NOAA/AVHRR II sea surface temperatures (SST) and NIMBUS-7/CZCS phytoplankton pigment concentrations was conducted in order to characterize their mean distributions and their space-time variability in the eastern North Atlantic, particularly in the vicinity of the western Iberian Peninsula. A 9-year long (1982--1990) SST set relative to a large part of the North Atlantic was extensively processed and analyzed to obtain the highest space-time resolution possible using only measured values. A good compromise led to a 9-year sequence of weekly averages of SST at 90 km x 90 km resolution. The first applications of these data were the preparation of yearly, seasonal and monthly mean surface temperature distributions with unprecedented resolution, as well as the construction of sequences of weekly SST charts for the whole 9-year period. The latter were used to construct a color video-loop which clearly shows the seasonal and interannual evolution of SST in a large region of the North Atlantic, in particular the meridional migration of the isotherms, the variability of large-scale thermal features associated with the Gulf Stream, the Labrador Current, the Azores Current, and the coastal upwelling along the North Atlantic eastern boundary.
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Research Interests: Oceanography and Bloom
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Resting cysts of planktonic dinoflagellates, once produced, sink to the seabed where they can remain viable for a long time. These cysts have important ecological roles, such as acting as the inoculum for the development of planktonic... more
Resting cysts of planktonic dinoflagellates, once produced, sink to the seabed where they can remain viable for a long time. These cysts have important ecological roles, such as acting as the inoculum for the development of planktonic populations. Moreover, dinoflagellate cyst records from depth sediment cores are broadly used as a proxy to infer past environmental conditions. In this study, the main objective was to obtain information on the relationships between the spatial distribution of modern dinoflagellate cysts and present-day hydrography in the NW Iberian shelf. Cyst assemblages were analyzed in 51 surface sediment samples with varying grain sizes, collected at different water depths, following nine transects perpendicular to the coast, between Aveiro and Figueira da Foz (Atlantic Iberian margin). Multivariate statistical analyses revealed marked land-sea and latitudinal gradients in the distribution of cysts, and helped investigate how environmental factors [water depth, g...
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An analysis of NOAA/AVHRR II sea surface temperatures (SST) and NIMBUS-7/CZCS phytoplankton pigment concentrations was conducted in order to characterize their mean distributions and their space-time variability in the eastern North... more
An analysis of NOAA/AVHRR II sea surface temperatures (SST) and NIMBUS-7/CZCS phytoplankton pigment concentrations was conducted in order to characterize their mean distributions and their space-time variability in the eastern North Atlantic, particularly in the vicinity of the western Iberian Peninsula. A 9-year long (1982--1990) SST set relative to a large part of the North Atlantic was extensively processed and analyzed to obtain the highest space-time resolution possible using only measured values. A good compromise led to a 9-year sequence of weekly averages of SST at 90 km x 90 km resolution. The first applications of these data were the preparation of yearly, seasonal and monthly mean surface temperature distributions with unprecedented resolution, as well as the construction of sequences of weekly SST charts for the whole 9-year period. The latter were used to construct a color video-loop which clearly shows the seasonal and interannual evolution of SST in a large region of ...
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In a period when the Iberian sardine stock abundance is at its historical minimum, knowledge of the sardine juvenile’s distribution is crucial for the development of fishery management strategies. Generalized additive models were used to... more
In a period when the Iberian sardine stock abundance is at its historical minimum, knowledge of the sardine juvenile’s distribution is crucial for the development of fishery management strategies. Generalized additive models were used to relate juvenile sardine presence with geographical variables and spawning grounds (egg abundance) and to model juvenile abundance with the concurrent environmental conditions. Three core areas of juvenile distribution were identified: the Northern Portuguese shelf (centred off Aveiro), the coastal region in the vicinity of the Tagus estuary, and the eastern Gulf of Cadiz. Spatial differences in the relationship between juvenile presence and egg abundances suggest that essential juvenile habitat might partially differ from the prevailing spawning grounds. Models also depicted significant relationships between juvenile abundance, temperature and geographical variables in combination with salinity in the west and with zooplankton in the south. Results ...
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The Iberian Peninsula, at North Atlantic mid-latitude and the western extreme of the European continent, is a relevant area for climate reconstructions. This work provides multi-proxy records measured in 7 inner-shelf sediment sequences... more
The Iberian Peninsula, at North Atlantic mid-latitude and the western extreme of the European continent, is a relevant area for climate reconstructions. This work provides multi-proxy records measured in 7 inner-shelf sediment sequences from 5 sites located between South Portugal (Algarve) and Northwest Spain (Galiza) (36 to 42º N) and targets a regional reconstruction of climate variability during the last 2000 yr.<br><br> Alkenone derived Sea Surface Temperature (SST) reconstructions were compared to on-land precipitation given by higher plant n-alkanes and pollen data, to assess the relationship between hydroclimate (drought and/or precipitation) and oceanic SST.<br><br> The SST records reveal a long-term scale cooling (±1 ºC/2000 yr) that ends at the beginning of the 20th century at all sites. This cooling is a follow up of the cooling process started after the Holocene optimum and driven by a decrease in summer insolation in t...
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During summer (June, July, and August), northerly winds driven by the Azores anticyclone are prevalent over western Iberia. The Quick Scatterometer Satellite 2000 to 2009 summertime estimates reveal a broad high wind speed (≥7 ms−1) area... more
During summer (June, July, and August), northerly winds driven by the Azores anticyclone are prevalent over western Iberia. The Quick Scatterometer Satellite 2000 to 2009 summertime estimates reveal a broad high wind speed (≥7 ms−1) area extending about 300 km from shore and along the entire Iberian west coast. Nested in this large high‐speed region, preferred maximum regions anchored in the Iberian major capes, Finisterre, Roca, and S. Vicente, are found. Composite analyses of wind maxima were performed to diagnose the typical summertime synoptic‐scale pressure distribution associated with these smaller size high‐speed regions. The flow low‐level structure was further studied with a mesoscale numerical prediction model for three northerly events characterized by typical summertime synoptic conditions. A low‐level coastal jet, setting the background conditions to the marine atmospheric boundary layer (MABL) response to topography, was found in the three cases. The causes for wind ma...
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The Iberian Peninsula, at North Atlantic mid-latitude and the western extreme of the European continent, is a key point for climate reconstructions. This work provides multi-proxy records measured in 8 inner-shelf sediment cores from 5... more
The Iberian Peninsula, at North Atlantic mid-latitude and the western extreme of the European continent, is a key point for climate reconstructions. This work provides multi-proxy records measured in 8 inner-shelf sediment cores from 5 sites located between South Portugal (Algarve) and Northwest Spain (Galiza) (36 to 41º N) and target a regional reconstruction of climate variability during the Historic period (last 2 ky).<br><br> The SST records reveal a long-term scale cooling (±1 ºC/2 ky) that ends at the beginning of the 20th century at all latitudes. This cooling is a follow up of the cooling process that started in the early Holocene driven by a decrease in summer insolation in the Northern Hemisphere.<br><br> Within this long term SST variability multi-decadal/centennial scale variability is detected along Iberia. The different latitudinal SST reconstructions jointly with a determined regional SST stack were compared to on-la...
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Oceanogragraphic conditions at the Portuguese margin are characterized by seasonal coastal upwelling (May to September) and the influence of the Mediterranean Outflow Water (MOW) between 600 and 1500m water depth along the southern and... more
Oceanogragraphic conditions at the Portuguese margin are characterized by seasonal coastal upwelling (May to September) and the influence of the Mediterranean Outflow Water (MOW) between 600 and 1500m water depth along the southern and (south)western margin. Variability of these two oceanographic parameters during the last 1500 yr is reconstructed through a multi-proxy study from 10 multi- box-cores recovered from two profiles (7 at 37º 50´N, 267-2331m water depth and 3 at 8º 15´W, 667-1978m water depth). The distribution of upwelling planktonic foraminifera related species (mainly G. bulloides) on surface samples reflects upwelling conditions such as revealed by a ten year integration of Sea Surface Temperature (SST) satellite and pigment concentration along the Portuguese margin. A regional transfer function based on these data and SIMMAX 28 will be used to estimate Paleo-SST along the cores on both profiles. The productivity signal will be accessed through carbon content, stable ...