Transport patterns and hydrodynamic context of the MERITE-HIPPOCAMPE cruise: Implications for contaminants distribution and origin.

This study aims at characterizing the hydrodynamic context and transport patterns that prevailed during the MERITE-HIPPOCAMPE cruise to assist in the interpretation of in-situ observations. The main physical attributes and structures (mesoscale eddies as well as fine-scale fronts and filaments) are analyzed based on various physical diagnostics. They were computed from satellite data and data-assimilative model outputs to describe ocean dynamics. The Northern and Algerian Currents were prominent features during the cruise while the western basin is divided by the vertically-tilted Balearic front. Temperature and salinity were used to distinguish different water masses at both surface and sub-surface. Sea-level anomalies, relative vorticity, and Okubo-Weiss parameter distributions have shown the presence of marked eddies around stations St10 and St11. Furthermore, Finite-Size Lyaponuv Exponents revealed that the former was rather located on a fine-scale filament near the edge of a cyclonic eddy while the latter was closer to the core of an anticyclone. Nearshore thermal fronts were detected with the Belkin and O'Reilly Algorithm (BOA), especially around stations St17 and St19. The potential coastal sources of contaminants were tested using Lagrangian Origin Maps (LOM), suggesting that stations St1, St2, St4, St11, and St15 were most likely influenced by coastal waters. Additionally, an atmospheric reanalysis combined with a Lagrangian dispersal model allowed for estimating wet deposition events of contaminants while tracking the fate of water masses where rainfall took place. Finally, we provide a set of explanatory quantitative and qualitative variables for future statistical analyses that aim at explaining the distribution of both chemical and biological samples collected during the cruise.

A 25-years dataset of ageostrophic, Ekman and Stokes surface currents in the Mediterranean Sea (AGESC-Med).

A 25-years surface velocity data-set for the Mediterranean Sea is presented in this paper. The velocity data is obtained using a modified Ekman model which allows us to obtain an analytical solution for the surface currents using satellite altimetry and available wind and waves data from synoptic observations. The new database consists of 6-hourly ocean surface velocities (integrated over one-meter depth) including the geostrophic component and the Ekman and Stokes velocity components driven by the wind and waves, between 1993 to 2018, and covering the whole Mediterranean Sea with a spatial resolution of 1/8∘. The resulting Ageostrophic, Ekman and Stokes Currents in the Mediterranean basin (AGESC-Med) was validated validated with real drifters collected by the Italian National Institute of Oceanography and Experimental Geophysics (OGS). The AGECS-Med product improves the currently available sea surfave velocity fields obtained from altimetry, as well as analyze the meoscale ageostrophic dynamics induced by wind and waves.

An ocean front dataset for the Mediterranean sea and southwest Indian ocean.

Fronts are ubiquitous discrete features of the global ocean often associated with enhanced vertical velocities, in turn boosting primary production. Fronts thus form dynamical and ephemeral ecosystems where numerous species meet across all trophic levels. Fronts are also targeted by fisheries. Capturing ocean fronts and studying their long-term variability in relation with climate change is thus key for marine resource management and spatial planning. The Mediterranean Sea and the Southwest Indian Ocean are natural laboratories to study front-marine life interactions due to their energetic flow at sub-to-mesoscales, high biodiversity (including endemic and endangered species) and numerous conservation initiatives. Based on remotely-sensed Sea Surface Temperature and Height, we compute thermal fronts (2003-2020) and attracting Lagrangian coherent structures (1994-2020), in both regions over several decades. We advocate for the combined use of both thermal fronts and attracting Lagrangian coherent structures to study front-marine life interactions. The resulting front dataset differs from other alternatives by its high spatio-temporal resolution, long time coverage, and relevant thresholds defined for ecological provinces.

Explicit and implicit network connectivity: Analytical formulation and application to transport processes.

Connectivity is a fundamental structural feature of a network that determines the outcome of any dynamics that happens on top of it. However, an analytical approach to obtain connection probabilities between nodes associated with to paths of different lengths is still missing. Here, we derive exact expressions for random-walk connectivity probabilities across any range of numbers of steps in a generic temporal, directed, and weighted network. This allows characterizing explicit connectivity realized by causal paths as well as implicit connectivity related to motifs of three nodes and two links called here pitchforks. We directly link such probabilities to the processes of tagging and sampling any quantity exchanged across the network, hence providing a natural framework to assess transport dynamics. Finally, we apply our theoretical framework to study ocean transport features in the Mediterranean Sea. We find that relevant transport structures, such as fluid barriers and corridors, can generate contrasting and counterintuitive connectivity patterns bringing novel insights into how ocean currents drive seascape connectivity.

Corrigendum to 'A 60 year wave hindcast dataset in the Caribbean Sea' Data in Brief, 37 (2021)/ 107153.

[This corrects the article DOI: 10.1016/j.dib.2021.107153.].

A 60 year wave hindcast dataset in the Caribbean Sea.

This article presents a 60 years wave hindcast from 1958 to 2017, covering the Colombian Caribbean basin. Each output consists on 6-hour field of significant wave height H s , mean wave period T m - 01 , T mm - 10 and mean direction θ m with a resolution of 11.8 km × 11.4 km. The simulation was performed using SWAN model forced with JRA-55 wind fields. Model data is validated against NOAA buoy 42058 located in the central Caribbean. The resolution and time spam of this database allows to perform either coastal engineering projects as well as to perform research in seasonal and interannual wave climate variability including large return periods to evaluate coastal vulnerability.

Effect of small scale transport processes on phytoplankton distribution in coastal seas.

Coastal ocean ecosystems are major contributors to the global biogeochemical cycles and biological productivity. Physical factors induced by the turbulent flow play a crucial role in regulating marine ecosystems. However, while large-scale open-ocean dynamics is well described by geostrophy, the role of multiscale transport processes in coastal regions is still poorly understood due to the lack of continuous high-resolution observations. Here, the influence of small-scale dynamics (O(3.5-25) km, i.e. spanning upper submesoscale and mesoscale processes) on surface phytoplankton derived from satellite chlorophyll-a (Chl-a) is studied using Lagrangian metrics computed from High-Frequency Radar currents. The combination of complementary Lagrangian diagnostics, including the Lagrangian divergence along fluid trajectories, provides an improved description of the 3D flow geometry which facilitates the interpretation of two non-exclusive physical mechanisms affecting phytoplankton dynamics and patchiness. Attracting small-scale fronts, unveiled by backwards Lagrangian Coherent Structures, are associated to negative divergence where particles and Chl-a standing stocks cluster. Filaments of positive divergence, representing large accumulated upward vertical velocities and suggesting accrued injection of subsurface nutrients, match areas with large Chl-a concentrations. Our findings demonstrate that an accurate characterization of small-scale transport processes is necessary to comprehend bio-physical interactions in coastal seas.