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This study presents a generalised characterisation of the surface circulation over the northern shelf of the Gulf of Cadiz, based on 4 years of high-resolution satellite altimetry data from Sentinel-3A and wind model data. The altimetry-based surface zonal currents, adjusted for bottom-drag and wind effects, are compared with a generic CMEMS product and validated against in-situ ADCP measurements. The proposed altimetry product demonstrates superior performance than the CMEMS product, accurately reflecting surface circulation direction compared to in-situ measurements (r = 0.77, RMSE = 0.10 m/s, bias = 0.01 m/s). The use of the bottom-drag and wind-corrected/uncorrected altimetry product for spatiotemporal analysis of the shelf circulation revealed the distinct contributions of wind-driven and geostrophic components in different basin sectors. The results show that over the western basin, positive (eastward) surface currents were predominantly driven by westerly winds, while only occasionally, westward flows coincided with easterly winds, suggesting a higher control of the geostrophic component over the westward flows. In contrast, over the eastern basin, both eastward and westward flows were found to be primarily driven by favourable winds. Additionally, the analysis of Absolute Dynamic Topography (ADT) values along the whole basin showed the presence of ADT gradients both along-shore and cross-shore over the shelf, contributing to geostrophic flows. Finally, the seasonal analysis showed that eastward circulation tends to dominate during the spring and summer months, related to the upwelling season in the Gulf of Cadiz and associated westerly winds. Westward flows prevail during the winter months, related to easterly winds and the rebalancing of the along-shore sea level gradient during relaxed upwelling conditions. The findings demonstrate a significant improvement in the use of satellite altimetry data to study complex oceanographic dynamics in coastal areas, where both spatial and temporal variability are high. Moreover, the similarity of our results to those obtained from in-situ systems supports the use of altimetry data and publicly available wind models to support oceanographic studies in remote or resource-limited areas. [ABSTRACT FROM AUTHOR]

Over a hundred of experiments were realised between 1998 and 2022 in the Mediterranean Sea using surface Lagrangian drifters, at coastal and offshore level. Raw data were initially unified and pre-processed manually by eliminating spikes and wrong positions or date/time information. The integrity of the received data packages was checked, and incomplete ones were discarded. Deployment information was retrieved from an initial excel database and campaign notes for each drifter and integrated into the PostgreSQL database, realised and maintained by the National Institute of Oceanography and Applied Geophysics (OGS) in Trieste (IT). This database also collects a variety of metadata about the drifter model, project, owner and operator. Subsequently data were processed using standard procedures of editing and quality control developed for the OGS Mediterranean drifter dataset to remove spikes generated by malfunctioning of the sensors and obtain files with common characteristics. Drifter data and plots of each track were also visually checked to remove any point not identified by the automatic procedure and clearly erroneous. Drifters' trajectories were split into two or more segments that have been considered as different deployments, in case of specific drifters' behaviours. Data were interpolated at defined time intervals to temporarily unify tracks. From the original 138 experiments, a dataset of 204 tracks was obtained, available from the public open-access repository in SEANOE (SEA scieNtific Open data Edition) at https://doi.org/10.17882/90537 (Ribotti et al., 2022). [ABSTRACT FROM AUTHOR]

The sea surface velocity measurements obtained during the period of 2014–2016 using two high-frequency radars (HFR), which were installed on the northern coast of Vietnam, were reprocessed by using a variational approach (EOF/2dVar) to provide an extended dataset. The high temporal resolution of measurements and large spatial coverage of the radar data enabled the assessment of the surface circulation in the data-poor region of the southern Gulf of Tonkin (GoT) and the characterization of its temporal variations in a wide range of scales: from tidal frequency to annual cycle. It was found that tidal motions account for a large percentage (approximately 60%) of surface current variability in the GoT. The temporal variability of the kinetic energy of the surface currents is tightly correlated with wind variations in the monsoon-dominated atmospheric circulation system. Stratification, induced by the discharge of the Red River, also affects the tidal currents within the coastal region (~ 40 km wide) by modifying the tidal ellipses polarizations. Close to the shore, the prominent coastal flow experiences large temporal variations in response to wind and buoyancy forcing. The seasonal variability of the zonal wind component was found to play a significant role in coastal flow speed variations through the cross-shore mass exchange. The Red River freshwater discharge controls the seaward extension of the coastal flow and causes asymmetry in the seasonal variability of flow velocity. The data obtained and analysis results could be useful for the improvement of the regional circulation models, for further studies of the physical and biological processes in the GoT, and for marine resource management. [ABSTRACT FROM AUTHOR]

The Red Sea holds one of the lowest concentrations of floating plastic worldwide and no evident congregation zones were identified so far, despite peculiar oceanographic features that candidate the basin as an accumulation area for floating debris. However, the Red Sea exhibits a complex pattern of surface currents, which changes according to the monsoon season, possibly affecting the abundance of plastic throughout the year. To explore the effect of seasonality on plastic concentration in surface waters, we conducted a fortnightly time series sampling, using a neuston net, for 21 months at a pelagic station in the central Red Sea, where the major seasonal overturn of the Red Sea surface circulation occurs. The estimated average abundance (±SE) was 58,563 ± 19,272 items Km−2 (73.5 ± 40.75 g Km−2), highly variable according to season, lower during the summer monsoon. Indeed, the winter monsoon pushes oceanic surface waters inside the Red Sea, transporting alongside floating plastic items, whilst surface currents exit the basin during the summer monsoon, depleting central Red Sea waters from floating plastic. Composition of plastic items also changes through time. Particularly, the higher proportion of films and foams during summer months suggests that the main source of plastic at the sampling station from June to September is a short-range transport, while during winter months, the higher contribution of small fragments indicates that, from October to May, plastic is also transported to the central Red Sea through surface currents for long distances, possibly coming all the way from the Indian Ocean. Unlabelled Image • We conducted a seasonal sampling in an area of surface currents convergence. • We identified the central Red Sea as a hotspot of floating plastic. • Plastic concentrations vary seasonally according to the monsoons, lower in summer. • Plastic composition varies seasonally, with films more frequent in summer. • Most likely, plastic inputs are short-ranged in summer, long-ranged in winter. [ABSTRACT FROM AUTHOR]

As the base of almost all marine food webs, phytoplankton play a dominant role in determining the productivity of marine ecosystems. Recent studies have highlighted the dynamic variability of phytoplankton abundance in nearshore ecosystems over synoptic time scales. Therefore, a greater understanding of the physical mechanisms that contribute to this variability is required to assess impacts of current as well as future weather patterns on these ecosystems. In this study, chlorophyll fluorescence data from a nearshore location in southern Monterey Bay was used to identify the timing and duration of increases in phytoplankton concentrations. Regional physical parameters, including wind stress, wave height and water temperature were analyzed to determine what, if any, physical processes are associated with observed blooms. A significant negative correlation between water temperature and chlorophyll (high chlorophyll associated with cold water) was found for the two summer seasons studied (2012, 2013). The timing of high chlorophyll events coincided with relaxations of upwelling favorable wind conditions. Analysis of surface current data suggests that the incoming cold water masses are the result of poleward currents from the south of Monterey Bay. A conceptual model is proposed in which phytoplankton are advected into southern Monterey Bay during wind relaxation events preceded by upwelling events of great enough duration to establish well defined circulation patterns. The reversal of circulation patterns transports cold, phytoplankton-rich water into the bay from south of the Monterey Peninsula. This study demonstrates that wind relaxation events can be an important driver of localized high phytoplankton biomass events on the inner shelf by advecting recently upwelled water into coastal embayments that are relatively sheltered from strong upwelling favorable winds. • Phytoplankton abundance correlates strongest with inner shelf water temperature. • Phytoplankton blooms are associated with upwelling relaxation events. • Exposed coast and sheltered conditions vary dramatically across short distances. [ABSTRACT FROM AUTHOR]

Abstract The Taiwan Strait is the only channel connecting the South China Sea (SCS) and the East China Sea (ECS), and plays a key role in the material exchanges between SCS and ECS. The region however is poorly sampled during the northeast (NE) monsoon when severe weather hinders shipboard measurements. In this study, the surface circulations in the Taiwan Strait and the adjacent East China Sea are derived from the Geostationary Ocean Color Imager (GOCI) with a high spatiotemporal resolution. The satellite observations are limited by cloud over. Nevertheless, they provide the only surface flow observations useful in hypothesis testing. It is demonstrated that the transient surface currents can be classified into three regimes: a southwestward flow for strong winds, a northeastward flow for weak winds, and a cross-strait flow for moderate winds. The satellite observations are also valuable in validating model currents. Two high-resolution global ocean reanalysis products, the Hybrid Coordinate Ocean Model (HYCOM) and the Copernicus Marine Environment Monitoring Service (CMEMS), are examined. The reanalysis products are generally consistent with the satellite observations. The CMEMS moreover shows a superior performance. This study illustrates the unique capability of the geostationary ocean color satellite in providing spatially extensive surface flow observations in broad shelf regions where current meter data are sparse or non-existent. Highlights • Mapping surface circulation in the Taiwan Strait during NE monsoon from GOCI • Classifying into three flow regimes depending on the strength of northeasterly wind • Validating global 1/12° HYCOM and CMEMS model surface currents in the Taiwan Strait [ABSTRACT FROM AUTHOR]

Abstract Northern Hemisphere winter circulation is affected by both solar and terrestrial forcings. El-Niño events and volcanic eruptions have been shown to produce a negative and a positive North Atlantic Oscillation (NAO) signature, respectively. Recent studies show a positive NAO signature related to both geomagnetic activity (proxy for solar wind driven particle precipitation) and sunspot activity (proxy for solar irradiance). Here the relative role of these four different drivers on the Northern Hemisphere wintertime circulation is studied using a statistical analysis of observational and reanalysis data during 1868–2014. The phase of the Quasi-Biennial Oscillation (QBO) is used to study driver signals in different stratospheric conditions. Moreover, the effects are separated for early/mid- and late winter. Our findings suggest a stratospheric mediation of the ENSO signal to the Atlantic side, which is delayed and modulated by the QBO unlike the signal in the Pacific side. The positive NAO by volcanic activity is preferentially obtained in the westerly QBO. We also find a substantial QBO modulation for geomagnetic activity and late winter sunspot activity, which favours a stratospheric pathway and the top-down mechanisms. However, signal in the North Pacific produced by early/mid-winter sunspot activity remain rather similar in different QBO phases and supports a direct forcing from the troposphere by the bottom-up sunspot mechanism. Highlights • Effects of ENSO, volcanic activity, geomagnetic activity and sunspots to winter circulation is studied during 1868-2014. • The phase of the QBO is used to study driver signals in different stratospheric conditions during 1900-2014. • ENSO and sunspots responses in the Pacific remain the same in different QBO phases supporting direct tropospheric forcing. • All driver responses in the Atlantic change notably in different QBO phases supporting substantial stratospheric influence. [ABSTRACT FROM AUTHOR]

The Indo-Pacific warm pool (IPWP) is an area hosting key tropical climate processes such as the El Niño Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD). The tropical climate processes, via various feedback mechanisms, control the surface ocean climate in the Indian Ocean and its surrounding continents on annual to inter-annual timescales. However, little has been known about how the tropical processes are effective forcing climate mechanism over longer timescales. Here we presented a reconstruction of the spatiotemporal pattern of sea surface temperature (SST) with inferred hydroclimate changes since the early Holocene (∼11ka), using proxies of planktonic foraminifer shell Mg/Ca, organic biomarker (TEX 86 ), foraminifer oxygen isotopes, and a terrigenous BIT index measured from a 220 cm long Core BS24 (2.724041°N, 97.010943°E, 1015 m water depth) which was taken offshore of northwest Sumatra in the eastern Indian Ocean. With an age model of 13 AMS 14 C dating by the uses of planktonic foraminiferal shells from the core, the TEX 86 H temperatures of BS24 show as summer-weighted, and reflect integrated thermal effects from the surface to thermocline water, while the Mg/Ca temperature of BS24 better reflects mean annual SST. Our results, along with a regional synthesis of published SST records from the IPWP, suggest that the IPWP has migrated eastwardly since the mid-Holocene (∼5ka). In phase with this eastward migration, the IPWP SSTs have decreased, but the upwelling in the eastern Indian Ocean appears to have been a persistent feature since the mid-Holocene. Our Empirical Orthogonal Function (EOF) analysis on the compiled IPWP SST records indicates two dominant modes of spatio-temporal variability of surface hydrographes in the IPWP that are attributed to a combined effect of orbital and solar forcing, with expressions analogous to the Indian ocean basin-wide mode (IOBM) and the Indian Ocean dipole model (IOD). [ABSTRACT FROM AUTHOR]

The surface connection in the Mediterranean Sea is studied by looking at the statistical properties of 1632 near-surface Lagrangian trajectories. Based on the key role of the surface dynamics and geographical distribution of the data, this work focused on four study area: Strait of Sicily, Gulf of Lion, Alborán Sea and Cretan Passage. The strategy used in this work aims at limiting the problem of data coverage by choosing many regions of arrival (defined as target boxes), around each study area, choice based on drifter trajectories, current patterns and regions of interest, and using the bootstrap resampling method to compute Lagrangian statistics. The pseudo–Eulerian analysis obtained from all trajectories passing through each study area shows the main dynamical structures present in the Mediterranean Sea (e.g. Wester Alborán Gyre, Algerian Current, Northern Current, Lion Gyre, Atlantic Ionian Stream, Pelops Gyre, Western Cretan Gyre, etc.). The data coverage decreases progressively moving away from each study area, following the main surface current flows. Connection percentages computed between each source area and relative target boxes show highest values along the main current patterns. In particular, 70%–50% from Sicily Strait to Sardinia Channel with transit time of about 5–20 days; 40%–30% from Gulf of Lion to Ligurian-North Tyrrhenian Sea with transit time of about 13–37 days; 70% from Alborán Sea to Algerian coast with transit time of about 17 days; 30% from Cretan Passage to Levantine Basin with transit time of about 20 days. • Surface connection between more sub–basins of the Mediterranean Sea and surrounding areas. • Study of statistical properties of near-surface lagrangian trajectories. • Residence and transit time statistics were calculated from drifter data. • Bootstrap method was used to reduce the problem of finite number of drifter trajectories. [ABSTRACT FROM AUTHOR]

Microplastic pellets (MPPs) are ubiquitous contaminants, recognised as a serious threat to the biota in coastal, estuarine and marine environment. The distribution, abundance, weathering and chemical characteristics of MPPs on the beaches of Goa, and their transport to the coast during the southwest (SW) monsoon are discussed in this paper. MPP samples collected from six sandy beaches were categorised based on colour and polymer types using Stereoscope microscope and FTIR-ATR spectroscopy, respectively. White colour MPPs were the most abundant, and Polyethylene (PE) and Polypropylene (PP) were the dominant polymer types of MPPs deposited on all the beaches. Carbonyl index values showed that MPPs collected in June 2015 (representing SW monsoon) were ‘new’, whereas the MPPs collected in January 2015 were ‘aged’, showing that MPPs are arriving at Goa coast only during SW monsoon due to conducive hydrodynamic conditions. Characteristics of MPPs suggest that they could be originated primarily from ocean-based sources. The winds and surface currents during SW monsoon are the driving forces for the transportation and deposition of MPPs on the Goa beaches. The results of this study will be useful to the National ‘Clean India’ program for effective plastic debris removal management. [ABSTRACT FROM AUTHOR]

A dataset of XBT (eXpendable BathyThermograph) temperature profiles collected by ships of opportunity along the Genova-Palermo route, since September 1999, is analyzed, together with altimetric observations and model results, with the purpose of identifying and characterizing robust circulation features along the track and investigating their variability. An anticyclone is found in the Ligurian Sea, just north of the Corsica Channel, not present in previous descriptions of the Mediterranean Sea circulation. It appears to be a recurrent feature, better defined and stronger in summer and in the beginning of autumn. In the northern part of the Tyrrhenian Sea, the well-known Bonifacio dipole shows a similar seasonality, in agreement with previous observations. However, the Bonifacio anticyclone also displays a strong interannual variability, not previously recorded, with significant variations in position and shape. In fact, the data suggest the existence of two distinct summer circulation regimes related to the position and shape of the Ligurian anticyclone. When the latter is wider, filling the entire region north of the Corsica Channel, the circulation in the northern Tyrrhenian Sea is isolated from that in the Ligurian Sea, in agreement with the common picture. However, the altimeter maps show that there are several cases in the last two decades in which the Ligurian anticyclone is small and displaced to the west, allowing an inflow through the Corsica Channel into the Tyrrhenian Sea. The two regimes appear to result from a delicate balance between the forcings acting in the two sub-basins and the topographic constraints. [ABSTRACT FROM AUTHOR]

The processes and instabilities occurring at the ocean surface in the northern Gulf of Mexico between 96.3°W–86.9°W and 25.4°N–30.7°N are investigated with a regional model at submesoscale-permitting horizontal grid resolution (i.e., HR with dx = 1.6 km) over a three-year period, from January 2010 to December 2012. A mesoscale-resolving, lower resolution run (LR, with dx = 5 km) is also considered for comparison. The HR run is obtained through two-way nesting within the LR run. In HR quantities such local Rossby number, horizontal divergence, vertical velocity, and strain rate are amplified in winter, when the mixed layer is deepest, as found in other basins. In the model configuration considered this amplification occurs in surface waters over the continental slope and off-shore but not over the shelf. Submesoscale structures consist of a mixture of fronts and eddies generated by frontogenesis and mixed layer instabilities, with elevated conversion rates of available potential energy (APE) into eddy kinetic energy (EKE). In all quantities a secondary maximum emerges during the summer season, when the mixed layer depth (MLD) is shallowest, barely 15–20 m. The secondary peak extends to the coast and is due to the intense lateral density gradients created by the fresh water inflow from the Mississippi River system. Submesoscale structures in summer consist predominately of fronts, as observed in the aftermath of the 2010 Deepwater Horizon oil spill, and their secondary circulations are impeded due to the limited depth of the mixed layer. Freshwater river input is key to the submesoscale activity in summer but modulates it also in winter, as shown with a sensitivity run in which the riverine inflow is absent. Implications for transport studies in regions characterized by intense freshwater fluxes and for submesoscale parameterizations are discussed. [ABSTRACT FROM AUTHOR]

Global Drifter Program (GDP) drifter data and Argo float data from 2006 to 2013 are used to provide quantitative description and comparison of the mean near-surface (15 m) and 1000 m velocity fields in the New Zealand region. These fields are estimated both from bin-averaging the drifter/float velocities and by fitting non-divergent streamfunctions to the velocities. At both levels, our velocity fields are broadly consistent with previous drifter/float estimates, but provide more detail on the local structure of the mean fields. North of the Subantarctic Front there are large differences between the surface and 1000 m flows, with the Tasman Front being largely absent at 1000 m. South of the Subantarctic Front, where the flow is expected to be more barotropic, there is a closer correspondence between the flows at both levels. Several previously undocumented eddies in the mean flows at both levels are described. [ABSTRACT FROM PUBLISHER]

The present study analyses the mean and seasonal mesoscale surface circulation of the Northern South China Sea (NSCS) and determines the influence of El Niño/Southern Oscillation (ENSO). High resolution Eulerian velocity field is derived by combining the available satellite tracked surface drifter data with satellite altimetry during 1993 - 2012. The wind driven current is computed employing the weekly ocean surface mean wind fields derived from the scatterometers on board ERS 1/2, QuikSCAT and ASCAT. The derived mean velocity field exhibits strong boundary currents and broad zonal flow across NSCS. The anomalous field is quite strong in the southern part and the Seasonal circulation clearly depicts the monsoonal forcing. Eddy Kinetic Energy (EKE) distribution and its spatial and temporal structures are determined employing Empirical Orthogonal Function (EOF) analysis. The ENSO influence on NSCS surface circulation has been analyzed using monthly absolute geostrophic velocity fields during 1996 - 1999. [ABSTRACT FROM AUTHOR]

The local wind-driven circulation off southern San Diego is addressed with two complementary statistical and dynamical frameworks based on observations and idealized numerical model simulations. The observations including surface currents from high-frequency radars, subsurface currents from a nearshore mooring, and wind records at a local wind station are analyzed with the idealized ocean model (MITgcm) simulations using realistic bottom topography and spatially uniform wind stress forcing. Statistically estimated anisotropic local wind transfer functions characterize the observed oceanic spectral response to wind stress separately in the x (east-west) and y (north-south) directions. We delineate the coastal circulation at three primary frequencies [low ( σ=0.0767 cycles per day (cpd)), diurnal ( σ=1 cpd), and inertial ( σ=1.07 cpd) frequencies] with the momentum budget equations and transfer functions. At low frequency, the magnitudes of transfer functions are enhanced near the coast, attributed to geostrophic balance between wind-driven pressure gradients and the Coriolis force on currents. The response diminishes away from the coast, returning to the balance between frictional and Coriolis terms, as in the classic Ekman model. On the contrary, transfer functions in the near-inertial frequency band show reduced magnitudes near the coast primarily due to friction, but exhibits the enhanced seaward response as a result of the inertial resonance. The idealized model simulations forced by local wind stress can identify the influences of remote wind stress and the biases in the data-derived transfer functions. [ABSTRACT FROM AUTHOR]

Abstract: Biogenic fluxes from two sediment traps in the Ionian sea (35°13′N, 21°30′E) at 500 and 2800m water depth are discussed in relation with the main oceanographic and external forcing and compared with previous data from a nearby location. This study is part of a multi-year sediment trap deployment, aimed at assessing seasonality and interannual variability of biogenic and abiogenic fluxes. Here, we focus on fluxes related to two main phytoplankton groups: coccolithophores and diatoms. At our mooring site, high-coccolithophore and low-diatom fluxes confirm the oligotrophic character of the pelagic eastern Mediterranean year-round. Coccolithophore assemblages are dominated by the cosmopolitan species Emiliania huxleyi, followed by the deep-dwelling Florisphaera profunda and by several minor species. Diatom assemblages are dominated by Thalassionema bacillare and Nitzschia interruptestriata, with ~100 common and minor species. Overall, the combined flux pattern of coccolithophores and diatoms shows a clear seasonality throughout the study period, which can be related to changing oceanographic conditions and a different depth of production within the photic zone. Worth to note is the extremely high abundance, with respect to previous pelagic records, of species indicative of an intense deep chlorophyll maximum (DCM), which could indicate a shoaling of the nutricline. This feature can be related to the variability that affects surface hydrography and the deep water masses. Additionally, the occurrence of neritic, benthic and brackish to fresh-water diatom species, mainly in the deeper trap, could be linked to either lateral transport within the water column or the atmospheric input of Saharan dust, which is known to be common over the eastern Mediterranean especially during spring time. Finally, correlation of the flux pattern at different depths allowed sinking speeds for total and biogenic particles to be calculated, which ranged from 70 to >200mday−1. Three possible mechanisms can explain such high sinking rates and the coincidence of biogenic and total particle fluxes in the traps: a) the ballast effect of coccoliths; b) the packaging effect of fecal pellets related to the grazing activity of zooplankton; and c) the ballast effect of dust particles. [Copyright &y& Elsevier]

Abstract: The pattern of surface circulation in the Mozambique Channel was elucidated from the trajectories of 82 satellite-tracked drifters over the period 2000–2010 and complementary satellite-derived altimetry. Overall, the trajectories indicated that anticyclonic activity was mostly observed on the western side of the Channel, with cyclonic activity being more prevalent in the east. A lack of eddy activity was noted in the southeast corner of the Channel (i.e. SW of Madagascar). Drifter behaviour illustrated that surface water from the Comoros Basin, entrained into anticyclonic eddies during formation, can be retained and isolated for months whilst being transported southwards through the Channel. During a tropical cyclone weather event, a drifter was observed to switch between counter-rotating eddies indicating that horizontal mixing of the Ekman layer does occur. The drifters also illustrated and emphasised the flow field and transport between eddies (i.e. the interstitial flow) in the Mozambique Channel. Despite the dominance of southward propagating anticyclones, drifters were able to move north and south through the Channel in the frontal flow field between eddies within periods of 51–207 days. Cross-channel transport in both directions between the Madagascan and Mozambique shelf regions was similarly observed, with time spans of 19–30 days. Surprisingly, drifters from the southern limb of the East Madagascar Current were transported westward across the channel to the Mozambique shelf. This transport was similarly facilitated by the frontal flow field between eddies. It is hypothesised that the frontal zones between eddies and interstitial waters play an important role in distributing biota in the Mozambique Channel. [Copyright &y& Elsevier]

The surface circulation of the Marmara Sea was studied with satellite-tracked drifters during 2 field experiments. A total of 29 drifters were released in September 2008 and February 2009 at key locations south of the Bosphorus and in the central part of the sea. The spatial structures and temporal variability are described together with the atmospheric conditions of the Marmara Sea during the period of study. The behavior of drifters with respect to the wind was qualitatively analyzed. The pseudo-Eulerian velocity statistics were computed from the interpolated positions and maps of the mean currents were produced using the data sorted by experiment. The results are the first of their kind in the area and complement previous findings obtained by means of hydrographic and ADCP measurements. The overall surface flow is westward oriented from the Bosphorus Strait to the Dardanelles Strait. A jet-like flow that enters the Marmara Sea from the Bosphorus Strait and, meandering, crosses the sea prevailed during the entire study period. The surface circulation of the Marmara Sea is quite complex and displays very high variability. For example, the drifter data reveal that during the study period the mean flow was confined immediately north of Marmara Island in the western part of the sea. This was due to the presence of a large anticyclone in the northwestern area of the sea that had never been observed before. Additionally, sudden reversals and a complex eddy activity (mainly anticyclonic) were observed. Wind plays an important role in the surface circulation. The upper layer currents seem to respond very rapidly to the direct and indirect effect of the wind forcing. [ABSTRACT FROM AUTHOR]

European anchovy egg occurrence and density data from summer surveys (1998-2007) and oceanographic data were examined to study the mechanisms that control the spatial distribution of anchovy spawning habitat in the Strait of Sicily. Quotient analysis indicated habitat preference for temperature (18-19°C), bottom depth (50-100 m), water column stability (13-14 cycle h−1), fluorescence (0.10-0.15 μg m−3 Chl a), salinity (37.5-37.6 PSU), current speed (0.20-0.25 m s−1) and density (26.7-26.8 kg m−3, σt). Canonical discriminant analysis identified temperature, column stability and fluorescence as major drivers of anchovy spawning habitat. Three of the 4 years which had lower egg abundance were warmer years, with low values of primary productivity. A geostrophic current flowing through the Strait (the Atlantic Ionic Stream, AIS) was confirmed as the main source of environmental variability in structuring the anchovy spawning ground by its influence on both the oceanography and distribution of anchovy eggs. This 10-yr data series demonstrates recurrent but also variable patterns of oceanographic flows and egg distribution. A lack of freshwater flow in this area appears to depress productivity in the region, but certain and variable combinations of environmental conditions can elevate production in some sub-areas in most years or other sub-areas in fewer years. These temporal and spatial patterns are consistent with an ocean triad theory postulating that processes of oceanographic enrichment, concentration, and retention may help predict fishery yields. [ABSTRACT FROM AUTHOR]

Abstract: Salinity, temperature, and depth profiles from 1973 to 2010 were used to construct a seasonal climatology of surface temperature, surface salinity, mixed layer depth (MLD), potential energy of mixing, and surface geostrophic circulation in Prince William Sound (PWS) and the adjacent Gulf of Alaska. Surface salinity is greatest in winter and least in summer due to the influence of increased freshwater runoff in summer. It is generally lowest in the northwest and highest in the Gulf of Alaska. The surface temperature is lowest in the winter and highest in the summer when surface heating is greatest, with little spatial variability across the Sound. The MLD is deepest in winter (9–27m) and shallowest in summer (4–5m). The work by winds was estimated from meteorological buoy data in central PWS and compared to the potential energy of mixing of the upper water column. The potential depth to which winds mix the upper water column was generally consistent with the MLD. The surface geostrophic circulation in the central Sound has: a southerly flow in the western central Sound in the winter; a closed, weak anticyclonic cell in spring; a closed, cyclonic cell in the summer; an open, cyclonic circulation in the fall. In the western passages, a southerly flow occurs in spring, summer, and fall. These results have important implications for oil spill response in PWS, the use of oil dispersants, and for comparison to numerical studies. [Copyright &y& Elsevier]

Within the framework of the EGYTTO-EGYPT programs, the spatial structure and the temporal variability of the surface circulation in the eastern basin of the Mediterranean were studied using satellite-tracked drifters. A total of 81 SVP drifters were deployed in the Eastern Mediterranean area from September 2005 to October 2006. Only 5 drifters entered the Egyptian waters; three drifters were released during November 2005 and two in April 2006. The movement of these 5 drifters is used to study the surface circulation of the southeastern Mediterranean waters off Egypt. As computed until 29 August 2006, the maximum drifter lifetime was 128 days and the mean half-life (the time after deployment for which 50% of the instruments still provide useful data) was about 63 days. The movement of the drifters released during the present study indicated the existence of the eastward flow, Mersa Matruh and Ierapetra gyres. The calculated mean flow was strong of about 20-25 cm/sec and flow eastward along the continental slope off Egypt. Mean Kinetic Energy (MKE) and Eddy Kinetic Energy (EKE) for the study area were computed to point out the most energetic circulation features and the areas characterized by large variability. Summer was more energetic than winter. The MKE was 123 cm2/sec2 in summer and decreased to about 100 cm2/sec2 in winter. [ABSTRACT FROM AUTHOR]

The surface circulation in the Liguro-Provençal basin and Gulf of Lion (north-western Mediterranean) is studied using satellite-tracked drifters in the period 2007-2009. Complex circulation patterns prevailed in the eastern Ligurian Sea, before the drifters joined the Northern Current (NC) in the coastal area off Genoa. Between 5°E and 7°30'E, most drifters (especially in summer) were advected offshore before heading to the east and eventually closing a basin-wide cyclonic circulation. This offshore turning is related to the wind and wind stress curl during north-westerly wind events. In constrast, most drifters proceeded into the Catalan Sea in the fall. Although the Western Corsican Current was well delineated by the drifters, no signature of the Eastern Corsican Current was shown, indicating limited connectivity between the Tyrrhenian and Ligurian seas in summer 2007. Pseudo-Eulerian velocity statistics were calculated in the coastal region extending between Genoa and the Gulf of Lion. Fast currents are evident on the shelf break, especially off Imperia (maximum of 90 cm/s) where the NC is closer to shore and narrower. A stagnation area inshore of the NC near Fréjus is characterized by little mean flow and low velocity fluctuations. Mean currents are also reduced off Menton-Nice where the variability is maximum. More to the west, the NC broadens and slightly reduces in strength. [ABSTRACT FROM AUTHOR]

Abstract: A network of HF radars operated in the northeastern Adriatic Sea in the period September 2007 to August 2008. Surface currents were collected with the purpose of studying the temporal and spatial modes of surface circulation in the area. Their dependence on local wind forcing was investigated using wind records from coastal stations and the mesoscale meteorological model ALADIN/HR. EOF decomposition, spectral and tidal analyses, and time-lagged correlation extracted the dominant features in the area and their time scales. The time-averaged flow presented a cyclonic circulation pattern with relatively weak currents and standard deviations comparable to average values. Three dominant current patterns were extracted by the EOF analysis, which accounted for about 70% of total variance. In the region, wind was the major source of current variability over a wide portion of frequencies, whereas tidal forcing was weak and limited to the semidiurnal and diurnal frequencies, representing 10%–20% of the total variance. The response to wind forcing was immediate with veering angles consistent with Ekman dynamics in the majority of the area. Coherence analyses revealed strong correlation within the sub-tidal and diurnal bands, the latter related to diurnal sea-breezes variability. The seasonal variability of the inertial motions was also observed in the area. [Copyright &y& Elsevier]

Abstract: The surface circulation in the Sicily Channel and in the Ionian Sea is investigated using MODerate-resolution Infrared Spectro-radiometer (MODIS) chlorophyll-a images collected from 2003 to 2007. The use of chlorophyll as surface tracer in the area is verified by comparison with satellite altimeter measurements available during the same period. The interaction between waters with different concentrations of chlorophyll adds new particulars to the surface circulation of the Atlantic Water (AW) in the study area. In the Sicily Channel, warm anticyclonic structures located in the southern end drive the AW flow along their northern boundary to the south-east, towards the Libyan coast. In winter, the anticyclonic structures contract in a stable nucleus (the Sidra gyre) close to the African coast allowing AW intrusion over the Tunisian shelf (Atlantic Tunisian Current). In summer, the anticyclonic structure expands westwards, limiting the Atlantic Tunisian Current, and northwards, grazing the Atlantic Ionian Stream. It also fragments, allowing occasional AW intrusion into the central part of the Sicily Channel along different pathways. Due to the activity of the Sidra gyre, no evidence of the extension of the Atlantic Tunisian Current along the Libyan coast (east of 15°E) is found in the observation period. AW spreads into the central Ionian for long periods in summer but rarely in winter. It reaches the northern Ionian Sea via anticyclonic eddies (already observed in thermal imagery) departing from the northern and eastern border of the anticyclonic structure, captured by the prevalent clockwise offshore circulation in the northern Ionian (except in summer 2003). The deduced circulation is in agreement with recent studies based on the altimetric Mean Dynamic Topography and trajectories of drifters released in the Sicily Channel in recent years. [Copyright &y& Elsevier]

Abstract: Surface patterns of the low-frequency current in a 20×30km region in front of the Venice Lagoon were analysed from a 13-month-long HF radar data set. Surface circulation was related to prevalent wind regimes in the area and to the tidal flow through the lagoon inlet. Three different categories of wind-forcing were defined: bora (NE wind), sirocco (SE wind), and finally the category containing all other wind directions and calms (winds lower than 3m/sec). Mean flow and vorticity spatial distributions were discussed for different wind conditions. The coastal area about 5km wide is characterized by a flow field with maximum vorticity. Outside the coastal boundary layer the interior flow is part of the Adriatic basin-wide cyclonic circulation. Two counter-rotating vortices of the dimension of about 4–5km were evidenced in the average flow field in front of the lagoon inlet (Malamocco inlet) in all situations except for the bora. The vortex-pair is probably associated with the tidal flow through the inlet. The bora wind induces a strong southward coastal jet detached from the coast by about 5km homogenizing the flow and eliminating the dipole. The average coastal flow pattern in calm wind conditions was also analysed as a function of the strong inflow/outflow (currents in the inlet>0.7ms−1) from the lagoon inlet. In both cases the vorticity pattern is similar, with the negative vorticity to the left of the inlet and positive to the right looking seaward. [Copyright &y& Elsevier]

Abstract: The Gulf of Cádiz, strategically situated between the North Atlantic Ocean and the Mediterranean Sea, has been the focus of attention of a few oceanographic studies dealing with the deep circulation in order to understand the dynamics of the dense plume of Mediterranean water. Much less attention has been paid to the surface pelagic layer which holds important living resources of commercial and ecological interest. This overview summarizes the recent advances that have been made concerning the regional oceanography of the northern half of this important basin from an interdisciplinary point of view. Probably the most relevant oceanographic feature of the basin is its strong seasonality, which is linked to the meteorologically-induced seasonality of the eastern boundary current system of the North Atlantic. The prominent cape Santa Maria divides the continental shelf off the southern Iberian Peninsula in two shelves of different shape that hold different oceanographic processes, which in turn determine the characteristics of the pelagic ecosystem. Mass and energy inputs from land as well as tidally-driven processes makes the wider eastern shelf be more productive while the narrower western shelf, cut by a sharp submarine canyon, is under the influence of the almost-permanent upwelling spot off cape San Vicente. Under easterlies, the west-going, warm coastal countercurrent that is observed in the eastern shelf may invade the western shelf thus connecting biologically both shelves in an east-to-west direction. Westerlies induce generalised upwelling off the southern Iberia Peninsula, which adds to the almost-permanent one off cape San Vicente and generates an upwelling jet that moves eastwards. Cape Santa Maria may deflect this flow by generating a cold filament that extends southward and diverts water from the western shelf to the open ocean. This pattern of circulation hampers the biological connection between shelves in the west-to-east direction, which is therefore less effective. The eastern shelf is prone to hold a cyclonic circulation cell during summer. This cell seems to be part of the reproductive strategy of fish species like anchovy with significant commercial interest in the region. The coupling between spawning and circulation is particularly beneficial under westerlies, when productivity in the eastern shelf is enhanced and the plankton is confined within the cyclonic cell. Easterlies favour oligotrophy and the westward export of plankton, which has an adverse effect on the recruitment and correlates low anchovy catches with periods of noticeable easterly intensity. [Copyright &y& Elsevier]

Abstract: The surface circulation in the central Mediterranean, including the Sicily Channel, the southern Tyrrhenian and western Ionian seas, is studied using the data of more than 150 satellite-tracked drifters for the period spanning 1990–99. Pseudo-Eulerian maps of mean flow, eddy variability and energy levels are produced using all the data, the data sorted by seasons and the data divided in major wind categories, to study the circulation variability at meso to seasonal scales, and in terms of the local wind forcing. In general, the new results revealed by the drifter data confirm the general characteristics of the surface circulation as detected in previous Eulerian investigations. However, they provide a new broad quantitative description of the central Mediterranean surface circulation and they shed light on the dynamics of the Channel at large, including the Tunisian shelf and the area south of Malta, which shows unexpected characteristics of the surface velocity field, sometimes stagnant or even directed the opposite way with respect to the currents flowing further to the north. In addition, the drifter dataset allows to underline the seasonal character of the surface circulation in the area, and to assess the importance of the wind forcing. It was found that when winds blow from the northwestern sector (like the Mistral) the surface eastward transport in the Sicily Channel is enhanced. In contrast, for opposing wind conditions (blowing from the southeastern sector), the transport trough the Channel is significantly reduced. The quasi-Lagrangian nature of the drifters is also exploited to estimate Lagrangian statistics, such as the auto-covariance, the horizontal diffusivity and the integral time and space scales. Diffusivities and scales ranging in 1–5×107 cm2 s−1, 1–2 days and 10–30km were found, respectively. [Copyright &y& Elsevier]

Abstract: A realistic 4-year dataset of the surface velocity field of the western Mediterranean Sea obtained with the Mediterranean Forecasting System and the GFDL-MOM model was used to obtain the finite-scale Lyapunov exponents (FSLE) and finite-size diffusion coefficients. Dispersive properties and Lagrangian parameters in four sub-basins are discussed, and a comparison is made between the FSLE and the Eulerian Okubo–Weiss parameter obtained for the same area with the same dataset. An additional comparison is made with the FSLE calculated from independent datasets obtained from 15 drifters launched in the Algerian basin during October of 1996. [Copyright &y& Elsevier]

Abstract: The “Wind Events and Shelf Transport” (WEST) program was an interdisciplinary study of coastal upwelling off northern California in 2000–03. WEST was comprised of modeling and field observations. The primary goal of WEST was to better describe and understand the competing influences of wind forcing on planktonic productivity in coastal waters. While increased upwelling-favorable winds lead to increased nutrient supply, they also result in reduced light exposure due to deeper surface mixed layers and increased advective loss of plankton from coastal waters. The key to understanding high levels of productivity, amidst these competing responses to wind forcing, is the temporal and spatial structure of upwelling. Temporal fluctuations and spatial patterns allow strong upwelling that favors nutrient delivery to be juxtaposed with less energetic conditions that favor stratification and plankton blooms. Observations of winds, ocean circulation, nutrients, phytoplankton and zooplankton off Bodega Bay and Point Reyes (38°N) were combined with model studies of winds, circulation and productivity. This overview of the WEST program provides an introduction to the WEST special issue of Deep-Sea Research, including the motivation for WEST, a summary of study components, an integrative synthesis of major research results to-date, and background on conditions during field studies in May–June 2001 (the upwelling period on which this special issue is focused). [Copyright &y& Elsevier]

Abstract: The Gascoyne continental shelf is located along the north-central coastline of Western Australia between latitudes 21° and 28°S. This paper presents CTD and ADCP data collected in November 2000 together with concurrent wind and satellite imagery, to provide a description of the summer surface circulation pattern along the Gascoyne continental shelf and slope. It is shown that the region comprises a complex system of currents that are influenced by offshore eddies, wind stress, varying shelf-widths, coastal topography and outflow from the hypersaline Shark Bay. Four different water types and current systems were identified from the field measurements. The Leeuwin Current (LC) is the major current flowing through the region. It transports lower salinity, warmer water along the 200m isobath, poleward. The signature of the LC gradually transformed from a warm (24.7°C), lower salinity (34.6) water in the north to a cooler (21.9°C), more saline (35.2) water in the south resulting from geostrophic inflow of offshore waters. The width and depth of the current also changed continuously responding to the changing bottom topography and the orientation of the coastline: in the northern section under the influence of the narrow shelf and steep slope, the current was strong (∼0.75ms−1) and extended deeper into the water column. In contrast, the current decelerated (to ∼0.2–0.4ms−1) when flowing past the wider continental shelf offshore of Shark Bay and then accelerated along the southern section along the steep continental slope. Downwelling events were persistently associated with the current. The Ningaloo Current (NC) was confined to the northern Gascoyne shelf within 35km of the coast. Although upwelling was detected along the northern section of the study region, adjacent to the Ningaloo coral reef, water properties suggest a re-circulation of LC water from the south. Changes in the shelf width at Point Cloates have a significant influence on the NC resulting in bifurcation of the northward current. The higher salinity outflow from Shark Bay influences the continental shelf region immediately offshore of the main entrances to the Bay through the mixing of the higher salinity outflow water with the shelf waters. The Capes Current, a wind-driven current originating to the south of the study region was identified as a cooler, more saline water mass flowing northward. [Copyright &y& Elsevier]

Abstract: In time, the circulation of the Atlantic Water (AW) in the eastern basin of the Mediterranean Sea has been described differently, according to two major representations. The historical one, which began with the scheme from Nielsen in 1912 and has been refined up to the 1980s, favours a counterclockwise circulation in the whole basin, with AW flowing in its southern part as a broad flow off Libya and Egypt (from the Ionian to the Levantine subbasins), then continuing along Middle-East and Turkey before flowing back westwards. The more recent one, issued in the 1990s, favours a clockwise circulation in the northern part of the Ionian continuing offshore across the basin from the Cretan to the central part of the Levantine as the so-called “Mid-Mediterranean Jet”. This jet is depicted then as splitting both clockwise in the southeastern part of the basin and counterclockwise off Turkey (where this representation agrees with the former). Because the recent representation cannot be considered as a refinement of the historical ones, we have been interested in understanding why a given data set available to everybody is interpreted in such different ways. In the Algerian subbasin, the combined use of satellite infrared images and a significant amount of in situ data sets (hydrology and both Eulerian and Lagrangian current measurements) allowed us to solve a similar controversy. Therefore, we examined the circulation features in the eastern basin, undertaking the detailed analysis of ∼1000 daily and weekly composite images spanning the period 1996–2000, and of monthly composite images available since 1985. Whenever in situ observations were available, we have confronted them with the satellite thermal signatures and have shown that both are consistent. This paper focuses on the overall (basin scale) results while the detailed ones are published in an other paper. The new scheme we propose is basically a refined version of the historical ones: the circulation of AW is counterclockwise in the whole eastern basin but it is more constrained alongslope than previously thought, and the broadening historically schematised appears to be due to intense mesoscale eddies mainly generated by the instability of this circulation. [Copyright &y& Elsevier]

Abstract: Northward flowing coastal currents along the western margin of India during winter–spring advect low-salinity Bay of Bengal water in to the Eastern Arabian Sea producing a distinct low-salinity tongue, the strength of which is largely governed by the freshwater flux to the bay during summer monsoons. Utilizing the sedimentary records of δ18O G. sacculifer , we reconstructed the past salinity-gradient within that low-salinity tongue, which serves as a proxy for the variation in freshwater flux to the Bay of Bengal and hence summer monsoon intensity. The north–south contrast in the sea level corrected (residual)-δ18O G. sacculifer can be interpreted as a measure of surface salinity-contrast between those two locations because the modern sea surface temperature and its past variation in the study region is nearly uniform. The core-top residual-δ18O G. sacculifer contrast of 0.45‰ between the two cores is assumed to reflect the modern surface salinity difference of 1 psu and serves as a calibration for past variations. The residual-δ18O G. sacculifer contrast varies between ∼0.2‰ at ∼75 ky B.P. (i.e., late-Marine Isotope Stage 5) and ∼0.7‰ at ∼20 ky B.P. (i.e., Last Glacial Maximum), suggesting that the overall salinity difference between the northern- and southern-end of the low-salinity tongue has varied between ∼0.6 and ∼1.6 psu. Considerably reduced difference during the former period than the modern suggests substantially intensified and northward-extended low-salinity tongue due to intense summer monsoons than today. On the other hand, larger difference (∼1.6 psu) during the latter period indicates that the low-salinity tongue was significantly weakened or withdrawn due to weaker summer monsoons. Thus, the salinity-gradient in the eastern Arabian Sea low-salinity tongue can be used to understand the past variations in the Indian summer monsoons. [Copyright &y& Elsevier]

We performed sensitivity experiments using an ocean general circulation model at two stages of the Late Ordovician (Caradoc, ∼454 Ma; Ashgill, ∼446 Ma) under a range of atmospheric pCO2 values (8–18× PAL; pre-industrial atmospheric level) at high and low sea level.The model results indicate that the long-term cooling trend during the Late Ordovician can be explained by progressive cooling of the global ocean in response to falling levels of atmospheric pCO2, sea level change, and paleogeographic change. These results also explain the occurrence of low latitude cool-water carbonates in North America.In all simulations, a drop in sea level led to a reduction in poleward ocean heat transport. This indicates a possible positive feedback that could have enhanced global cooling in response to sea level drop during the Late Ordovician. Alterations in poleward ocean heat transport linked to changes of atmospheric pCO2 also indicate that there is a threshold of 10× PAL, above which ocean current change cannot be responsible for glaciation in the Late Ordovician. Continental drift could explain the observed global cooling trend in the Late Ordovician through a combined poleward ocean heat transport feedback and increased ice-albedo effect if atmospheric pCO2 was low during the entire Late Ordovician.The model results further indicate that the response of meridional overturning to changes in paleogeography, atmospheric pCO2, and sea level is stronger than the response of surface circulation to these perturbations. Because the overturning circulation is so strong, meridional overturning was the dominant mechanism for described changes in heat transport in the Late Ordovician. [Copyright &y& Elsevier]

For improved understanding of ocean circulation in the northern Indian Ocean region, long term continuous record of radiocarbon measurement is required. Limited radiocarbon records from the region demands investigations of natural archives. Coral core records along with some literature data were analysed to study the temporal changes in 14C values over the northern Indian Ocean. The major fraction of the bomb radiocarbon appears to have transferred in to the ocean, as recent records from the surface seawater Δ14C values show comparable or even higher than the atmospheric Δ14C values. The northern Andaman region showed higher Δ14C decline rate between 1978 and 2014 compared to the southern Bay of Bengal and the Lakshadweep region. The comparable southern Bay of Bengal and the Lakshadweep Δ14C values could be due to transfer of Arabian Sea waters to the southern Bay of Bengal. The southern Andaman region shows lower Δ14C values compared to the northern Andaman region, suggesting the influence of 14C depleted waters in the region. • Comparison of temporal changes in surface Δ14C value of the northern Indian Ocean. • Northern Andaman shows enriched Δ14C value compared to the atmosphere. • Δ14C decline rate in the Southern Bay of Bengal is lower than the Northern Andaman. • Lakshadweep and Southern Bay of Bengal show comparable surface Δ14C values. [ABSTRACT FROM AUTHOR]

The surface hydrography of the Indian Ocean (north of the equator) is influenced by the seasonal wind reversals, which affect the thermocline depth and mixed layer thickness as well as sea surface temperature (SST). We analyzed the surface-subsurface hydrographic changes in the Tropical Eastern Indian Ocean (TEIO) during the late Neogene and Quaternary, using planktic foraminiferal census data from ODP Hole 758A combined with surface-dwelling planktic foraminiferal stable oxygen and carbon isotope ratios. The occurrence of dominant thermocline-dwelling species and high surface productivity during the latest Miocene - Early Pliocene (between 6 and 3.4 Ma) reflects an intense Indian summer monsoon (ISM). Deepening of the thermocline and thickening of the mixed layer in the TEIO were driven by the weakening of the ISM after 3.4 Ma, causing fluctuations in surface productivity. Heat budget capacity increased after 3.4 Ma in the TEIO due to the thickening of the mixed layer, which may have also reduced the heat transport towards the South Pole. Further, the hydrography of the TEIO was affected by the advection of nutrient-rich saline water from the western Indian Ocean by the strong equatorial eastward flow between 2.7 and 1.2 Ma. We suggest that the development of the equatorial zonal Westerlies (Walker circulation) across the tropical Indian Ocean was a gradual process starting at ~3.4 Ma, which intensified at 2.7 Ma due to regional strengthening of the Indian winter monsoon. • Indian monsoon variability during the Plio-Pleistocene • Dynamics of the thermocline and mixed layer depth at Hole 758A • Shallow thermocline depth during 6 to 3.4 Ma and 1.2 Ma to Holocene • Deepening of thermocline depth with increasing SST s due to weakening of the ISM • Convergence of warm water at ~2.7 Ma enhanced the precipitation. [ABSTRACT FROM AUTHOR]

Lateral advection affects the spatial distribution of dissolved substances in the ocean but very few studies, so far, have been devoted to describe and quantify its impact on the distribution of dissolved organic carbon (DOC) which, in oligotrophic environments, accounts for the largest fraction of chemical energy. In this contribution, using an integrated approach, we explore the importance of surface advection on carbon dynamics in the Western Mediterranean Sea, where strong inter-basin differences in primary production do exist. Detailed information on the surface circulation, derived from high-resolution model simulations, is combined with the analysis of spatially resolved, accurate DOC vertical profiles, repeated over time. Our data show that surface circulation plays a crucial role in regulating DOC concentrations and distributions in the Tyrrhenian Sea and that horizontal transport of DOC into the Tyrrhenian Sea is of the same order of magnitude as in-situ DOC production. Our study addresses this process for the first time in the Mediterranean Sea, whose small size allows for fast, inter-basin transfer times which, in turn, favors the preservation of the DOC stock produced elsewhere. We highlight that this mechanism may be important also in other regions of the oceans, where surface advection may set up a sort of compensation among regions with different trophic regimes, thus smoothing trophic gradients. We posit that understanding these transport processes is a crucial and preliminary step to understand and quantify all the other processes (biological, chemical, geological) that influence DOC distribution on a variety of timescales. • Surface advection can supply chemical energy in the form of dissolved organic carbon to oligotrophic basins. • Trophic spatial gradients may be mitigated via the transport of dissolved organic carbon. • Integration of models and in-situ data unveils overlooked processes in the ocean. [ABSTRACT FROM AUTHOR]

This study evaluated the possibility of studying mesoscale surface circulation in coastal areas, as is the Gulf of Cádiz, Spain, using high-resolution altimetry data (20-Hz of posting rate) along with the use of wind and bottom friction ageostrophic corrections. Absolute cross-track surface zonal current velocities, derived from filtered along-track CryoSat-2 SIRAL-SARM Absolute Dynamic Topography (ADT) measurements, are compared with high-frequency radar (HFR) data in the coastal area of the Gulf of Cádiz. The filter strategy followed in this study for the altimetry data is dependent on the HFR measurements for each track. Absolute surface geostrophic velocities obtained from 20-Hz altimetry data agree well HFR further than 25 km from the coast. Close to land ([3–25] km) the ageostrophic component of the surface current (due to the wind drag and the bottom friction) needs to be considered in the altimeter data. On average, the correlation between altimetry and HFR improved from 0.61 (no correction) to 0.72 (correcting these effects). The root mean square error (RMSE) lowered from 12.54 cm·s−1 to 7.35 cm·s−1. Furthermore, it has also been demonstrated that corrected altimeter measurements are useful for the study of dynamics and patterns of coastal areas. • High frequency radar as tool for validating altimetry derived surface currents. • Bottom friction correction improves the results in the first 15 km from the coast. • Potencial of altimetry for dynamics in coastal areas using ageostrophic corrections. [ABSTRACT FROM AUTHOR]