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In the Panama Bight, two different seasonal surface circulation patterns coincide with a strong mean sea level variation, as observed from 27 years of absolute dynamic topography (ADT) and the use of self-organizing maps. From January to April, a cyclonic gyre with a strong southwestward Panama Jet Surface Current (PJSC) dominates the basin circulation, forced by the Panama surface wind jet that also produces upwelling, reducing sea surface temperature (SST), increasing sea surface salinity (SSS) and causing an ADT decrease. From June to December, the Choco surface wind jet enhances SST, precipitation and river runoff, which reduces SSS, causing an ADT rise, which in turn forces a weak circulation in the bight, vanishing the PJSC. Interannual variability in the region is strongly affected by El Niño–Southern Oscillation (ENSO); however this climatic variability does not modify the seasonal circulation patterns in the Panama Bight. In contrast, the positive (negative) ENSO phase increases (decreases) SST and ADT in the Panama Bight, with a mean annual difference of 0.9 ∘C and 9.6 cm, respectively, between the two conditions, while its effect on SSS is small. However, as the strong seasonal SST, SSS and ADT ranges are up to 2.2 ∘C, 2.59 g kg−1 and 28.3 cm, the seasonal signal dominates over interannual variations in the bight.

We study the impact of the Ekman currents and Stokes drift on the horizontal mixing and transport properties of the Mediterranean Sea. FSLE at the ocean surface are computed over the whole basin using 25 years of satellite altimetry derived geostrophic currents, 10-m wind velocity and wave fields. We find that the transport pathways unveiled by the geostrophic Lagrangian Coherent Structures (LCS) are significantly modified by the ageostrophic currents (i.e. Ekman and Stokes induced velocities), often leading to a decrease of the retention capacity of the eddies. An exhaustive assessment of the regional dependence and temporal variability of the FSLE shows an increase of the horizontal mixing activity, due to the ageostrophic component, up to 37% in regions such as the Gulf of Lion or the Aegean Sea, during the seasons where wind and waves are intense and persistent. Positive trends in the total FSLE (up to 1.2% of the value of FSLE per year in some regions) suggest that Mediterranean Sea has experienced a significant increase in mixing activity over the last decades. Ageostrophic features are considered to play a role in determining the properties of the relative dispersion. Through the analysis of the Lagrangian Anisotropy Index (LAI) using virtual and real pair of drifters, we observe that the particle dispersion is mainly dominated by the zonal flow, and that the ageostrophic currents induce meridional dispersion, particularly in regions where wind and wave are intensified.

In the Panama Bight, a reverse seasonal surface circulation coincides with a strong mean sea level variation, as observed from 27 years of Absolute Dynamic Topography (ADT) and the use of Self-Organizing Maps. From January to April, a cyclonic gyre dominates the basin circulation, forced by the Panama surface wind jet that also produce upwelling, reducing Sea Surface Temperature (SST) and increasing Sea Surface Salinity (SSS), causing an ADT decrease. From June to December, the Choco surface wind jet enhances SST, precipitation and river runoff, which reduces SSS causing an ADT rise, which forces a weak anticyclonic circulation. Interannual variability in the region is strongly affected by ENSO, however this climatic variability does not modify the seasonal circulation patterns in the Panama Bight. On the contrary, ENSO positive (negative) phase increases (decreases) SST and ADT in the Panama Bight, with a mean annual difference of 0.9 °C and 9.1 cm respectively between the two conditions, while its effect in SSS is small. However, as the strong seasonal SST, SSS and ADT ranges are up to 2.2 °C, 2.59 gr kg-1 and 28.5 cm, the seasonal signal dominates over interannual variations in the Bight.

Every year the Caribbean Sea faces the passage of several tropical cyclones that generate coastal extreme sea levels with potential strong and hazardous impacts. In this work we simulate the storm surges and wind waves induced by a set of 1000 tropical cyclones over the Caribbean Sea that are representative of the present-day climate. These events have been extracted from a global database of synthetic tropical cyclones spanning a 10 000-year period. The atmospheric forcing fields, associated with the set of tropical cyclones, are used to feed a coupled hydrodynamic–wave model with high resolution (∼ 2 km) along the continental and island coasts. Given the large number of events modelled, our results allow detailed statistical analyses of the magnitude and mechanisms of coastal extreme sea levels, as well as the identification of one of the most exposed areas to both storm surges and extreme wind waves.

The spatial distribution, the monthly and seasonal variability of mesoscale eddy-observations derived from the AVISO eddy atlas are assessed in the Caribbean Sea for the period between 1993 and 2019 (both included). The average lifetime for the whole set of eddies is 61.8±37.1days, mean amplitude of 7.4±4.2cm for ciclonic and 6.7±3.7cm for anticyclonic and mean radius of99.5±31.2km for cyclonic and108.0±32.4km for anticiclonic. Ciclonic eddies are on average more non-linear than anticiclonic. The spatio-temporal variability in the number of eddy-observations is evaluated against the Mean Eddy KineticEnergy (MEKE) derived from geostrophic currents as well as from seasonal winds. Spatial distribution of eddy-observations are correlated with MEKE while the migration of the intertropical convergence zone explains the advection of eddies towards the southern part of the basin.

Medicanes, for Mediterranean hurricanes, are mesoscale cyclones with morphological and physical characteristics similar to tropical cyclones. Although less intense, smaller, and rarer than their Atlantic counterparts, medicanes are very hazardous events threatening islands and continental coasts within the Mediterranean Sea. The latest strong episode, Medicane Ianos (September 2020), resulted in severe damages in Greece and several casualties. This work investigates the oceanic response to these extreme events along the Mediterranean coasts under present-day and future (late 21st century) climate conditions. To this end, a coupled hydrodynamic-wave model is used to simulate both storm surges and wind-waves generation and propagation in the Mediterranean Sea at high resolution (∼2 km) along the coastlines. A data set of thousands of medicanes synthetically generated from 20 global climate models and two atmospheric reanalyses is used to derive the atmospheric forcing fields. Regional coastal hazards assessment is performed for the present and future climates. For the first period, highest medicane-induced waves are found in the central and the southwest part of the western Mediterranean, while greatest storm surges are found in the Adriatic Sea and regions characterized by wide and gently sloping continental shelves. Results obtained for future changes show amplitudes generally smaller than the associated uncertainty due to limited agreement among models (especially for coastal elevation). Though, model consensus is reached (60–75%) and relative intensity change is significant (10–20%) at some locations (e.g., 1 m increase of medicane-induced significant wave height on average for south coasts of Sicilia)., This study was supported by the Project RTI2018-093941-B-C31 funded by MCIN/AEI/10.13039/501100011033/and by FEDER Una manera de hacer Europa. Tim Toomey acknowledges an FPI grant associated with the MOCCA project (Grant No. PRE2019-088046). Angel Amores was funded by the Conselleria d’Educació, Universitat i Recerca del Govern Balear through the Direcció General de Política Universitària i Recerca and by the Fondo Social Europeo for the period 2014–2020 (Grant No. PD/011/2019). Marta Marcos was supported by the Ministerio de Ciencia e Innovación and la Agencia Estatal de Investigación through Grant No. IED2019-000985-I. Romu Romero was funded by FEDER/Ministerio de Ciencia, Innovación y Universidades—Agencia Estatal de Investigación through the COASTEPS project (Grant No. CGL2017-82868-R).

Wave energy flux (WEF) is assessed in the Caribbean Sea from a 60-year (1958--2017) wave hindcast. We use a novel approach, based on neural networks, to identify coherent regions of similar WEF and their association with different climate patterns. This method allows for a better evaluation of the underlying dynamics behind seasonal and inter-annual WEF variability, including the effect induced by the latitudinal migration of the Intertropical Convergence Zone (ITCZ), and the influence of El Ni\~no-Southern Oscillation events. Results show clear regional differences of the WEF variability likely due to both a clear regionalization of the WEF due to both the intensification and migration of the ITCZ. WEF exhibits a strong semiseasonal signal in areas of the continental shelf, with maximums in January and June, in agreement with the sea surface temperature and sea level pressure variability. At larger scales, WEF shows a significant correlation with the Oceanic Ni\~no Index depicting positive values in the central and western basin and negative ones at the eastern side.

Following on from a theoretical solution to the Kelvin–Helmholtz (KH) instability under submerged canopy-oscillatory flow environments a relationship between the incoming free surface wave frequency and KH frequency was developed. The KH frequencies (fKH) are higher than those from the incoming wave expressed by fKH ≈[2.83,5.02]fw. In addition, the analytical expression, along with the energy spectra analysis of the vertical turbulent flux of momentum (Su′w′) for cases when the KH dominates vertical mixing, allowed us to observe the spectral shortcut mechanism. Based on comparisons between the KH time scale and the mean horizontal transport of mass time scale, it can be concluded that the instability has no effect on the wave-induced steady current process. The instability plays an important role on vertical mixing but not on the horizontal transport of mass., A. Cáceres-Euse wants to thank COLCIENCIAS for the scholarship 647, the Universidad Nacional de Colombia - Medellín and the University of California - Berkeley. AO acknowledges financial support from Ministerio de Ciencia, Innovación y Universidad through MOCCA project (RTI2018-095441-B-C21).

The Mediterranean Sea is a prominent climate-change hot spot, with many socioeconomically vital coastal areas being the most vulnerable targets for maritime safety, diverse met-ocean hazards and marine pollution. Providing an unprecedented spatial and temporal resolution at wide coastal areas, high-frequency radars (HFRs) have been steadily gaining recognition as an effective land-based remote sensing technology for continuous monitoring of the surface circulation, increasingly waves and occasionally winds. HFR measurements have boosted the thorough scientific knowledge of coastal processes, also fostering a broad range of applications, which has promoted their integration in coastal ocean observing systems worldwide, with more than half of the European sites located in the Mediterranean coastal areas. In this work, we present a review of existing HFR data multidisciplinary science-based applications in the Mediterranean Sea, primarily focused on meeting end-user and science-driven requirements, addressing regional challenges in three main topics: (i) maritime safety, (ii) extreme hazards and (iii) environmental transport process. Additionally, the HFR observing and monitoring regional capabilities in the Mediterranean coastal areas required to underpin the underlying science and the further development of applications are also analyzed. The outcome of this assessment has allowed us to provide a set of recommendations for future improvement prospects to maximize the contribution to extending science-based HFR products into societally relevant downstream services to support blue growth in the Mediterranean coastal areas, helping to meet the UN's Decade of Ocean Science for Sustainable Development and the EU's Green Deal goals., peer-reviewed

Wave Energy Flux (WEF) in the Colombian Caribbean Sea is assessed using a 60 years wave reanalysis from 1958 to 2017. Significant wave height (Hs) and mean wave energy period (Tm_1,0) are validated against in situ buoy data from the National Oceanic and Atmospheric Administration and from the Dirección General Marítima in the Central Caribbean Sea and in front of the Colombian shelf. WEF is calculated at virtual buoys allocated in the central Caribbean, at the continental shelf and around insular territories revealing a long-term decrease in magnitude with an annual rate between 0.01 and 0.2% with different regional behavior. In addition, WEF variations at interannual scale are found to be associated with ENSO phases. Wave energy power decreased from 1989 to 2017 in all analyzed locations., This work was supported by COLCIENCIAS (Departamento Administrativo de Ciencia, Tecnología e Innovación), convocatoria 727. A. Orfila would like to thank financial support from Ministerio de Ciencia, Innovación y Universidades of Spain through the MOCCA project (grant no. RTI2018-095441-B-C21).

The Tumaco multivariate index (TMI) is a multidecadal monthly index constructed with unique time series of sea surface temperature, surface air temperature and rain measured at Tumaco bay, in the southern Pacific coast of Colombia, and available since 1961. In this work, this index is re-evaluated after the addition of in situ sea level data, and its properties for different standardization periods are compared against oceanic El Niño–Southern Oscillation (ENSO) and other derived indices. In particular, we propose a modified TMI, hereinafter referred as TMI4, whose potential to identify the expected sign and the amount of future variations of rain induced by ENSO events in Colombia is analysed for selected extreme episodes. Results indicate that after the inclusion of sea level data, TMI4 can anticipate the development of El Niño events before the ENSO 3 and some other sea surface temperature-based regional indices, although its predictability depends on the ENSO type (canonical or Modoki). The explanation is that sea level includes new information into TMI4 on the onset of El Niño events. In particular, the signal of intraseasonal sea level anomalies carried by downwelling Kelvin waves is detected at Tumaco tide-gauge. Moreover, the analysis of the differences, both in magnitude and spatial distribution, of rainfall anomalies induced by positive (El Niño) and negative (La Niña) ENSO events characterized by TMI4 are regionally presented. As a result, we find that TMI4 is especially suited for extensive northern and western areas of mainland Colombia. For completeness, in the appendix we briefly introduce the semi-automated implementation of TMI4, including a visual interface, which is currently being tested by personnel within the operational oceanography area at Centro de Investigaciones Oceanográficas e Hidrográficas del Pacífico (Dimar-CCCP)., J. M. Sayol, L. M. Vásquez and J. L. Valencia thank funding from Centro de Investigaciones Oceanográficas e Hidrográficas del Pacífico – Dirección General Marítima de Colombia (Dimar), Ministry of National Defense of Colombia. J. M. Sayol also thanks the joint funding received from the Generalitat Valenciana and the European Social Fund under Grant APOSTD/2020/254. The work of DGG and IV was partially supported by Spanish Project RTI2018-093874-B-100 funded by MCIN/AEI/10.13039/501100011033 and by the Generalitat Valenciana Grant PROMETEO/2021/030. A. Orfila acknowledges financial support from FEDER/Ministerio de Ciencia, Innovación y Universidades – Agencia Estatal de Investigación through MOCCA project (grant # RTI2018-093941-B-C31).

Due to the semi-enclosed nature of the Mediterranean Sea, natural disasters and anthropogenic activities impose stronger pressures on its coastal ecosystems than in any other sea of the world. With the aim of responding adequately to science priorities and societal challenges, littoral waters must be effectively monitored with high-frequency radar (HFR) systems. This land-based remote sensing technology can provide, in near-real time, fine-resolution maps of the surface circulation over broad coastal areas, along with reliable directional wave and wind information. The main goal of this work is to showcase the current status of the Mediterranean HFR network and the future roadmap for orchestrated actions. Ongoing collaborative efforts and recent progress of this regional alliance are not only described but also connected with other European initiatives and global frameworks, highlighting the advantages of this cost-effective instrument for the multi-parameter monitoring of the sea state. Coordinated endeavors between HFR operators from different multi-disciplinary institutions are mandatory to reach a mature stage at both national and regional levels, striving to do the following: (i) harmonize deployment and maintenance practices; (ii) standardize data, metadata, and quality control procedures; (iii) centralize data management, visualization, and access platforms; and (iv) develop practical applications of societal benefit that can be used for strategic planning and informed decision-making in the Mediterranean marine environment. Such fit-for-purpose applications can serve for search and rescue operations, safe vessel navigation, tracking of marine pollutants, the monitoring of extreme events, the investigation of transport processes, and the connectivity between offshore waters and coastal ecosystems. Finally, future prospects within the Mediterranean framework are discussed along with a wealth of socioeconomic, technical, and scientific challenges to be faced during the implementation of this integrated HFR regional network., This study has been partially developed in the framework of the Interreg MED Strategic Project SHAREMED, co-financed by the European Regional Development Fund under the funding program Interreg MED 2014–2020. Website: https://sharemed.interreg-med.eu/ (last access: 31 March 2022). We are also grateful for the partial support of the (i) the project PO FEAMP 2014/2020 (Misura 2.51) funded by Regione Campania (Italy), (ii) the 2017 PRIN project EMME (Exploring the fate of Mediterranean microplastic: from distribution pathways to biological effects) funded by the Italian Ministry for Research (grant agreement no. 2017WERYZP), and (iii) the CMEMS-INSTAC phase II, which provides the context of the activities for HFR data harmonization, standardization, and distribution. Collaborative discussion on data management harmonization at the European level has also been carried out thanks to the contribution of the projects INCREASE (CMEMS Service Evolution Call for Tenders 21-SE-CALL1) and SeaDataCloud (EU-H2020 GA no. 730960).

The spatial distribution, and the monthly and seasonal variability of mesoscale eddy observations derived from the AVISO eddy atlas are assessed in the Caribbean Sea during 1993–2019. The average lifetime for the whole set of eddies is 62 ± 37 days, mean amplitude of 7 ± 4 cm for cyclonic and 7 ± 4 cm for anticyclonic and mean radius of 100 ± 31 km for cyclonic and 108 ± 32 km for anticyclonic. Cyclonic eddies are on average more nonlinear than anticyclonic ones. The spatio-temporal variability in the number of eddy observations is evaluated against the Mean Eddy Kinetic Energy (MEKE) derived from geostrophic currents as well as from seasonal winds. Spatial distribution of eddy observations is correlated with MEKE while the migration of the intertropical convergence zone explains the advection of eddies towards the southern part of the basin., Open Access funding provided thanks to the CRUE-CSIC agreement with Springer Nature. JMS received the joint funding from the Generalitat Valenciana and the European Social Fund under Grant APOSTD/2020/254. AO received financial support from projects Mocca and Lamarca (grants # RTI2018-093941-B-C31 and PID2021-123352OB-C31) funded by MCIN/AEI/ and by “ERDF A way of making Europe”, and from Fundación Iberostar and Université de Toulon-VAR. MELA is funded by Corporación CE-Marin through Convocatoria 14, 2018 supporting PhD candidates.

The Mediterranean Sea is a prominent climate change hot spot, being their socio-economically vital coastal areas the most vulnerable targets for maritime safety, diverse met-ocean hazards and marine pollution. Providing an unprecedented spatial and temporal resolution at wide coastal areas, High-frequency radars (HFRs) have been steadily gaining recognition as an effective land-based remote sensing technology for a continuous monitoring of the surface circulation, increasingly waves and occasionally winds. HFR measurements have boosted the thorough scientific knowledge of coastal processes, also fostering a broad range of applications, which has promoted their integration in the Coastal Ocean Observing Systems worldwide, with more than half of the European sites located in the Mediterranean coastal areas. In this work, we present a review of existing HFR data multidisciplinary science-based applications in the Mediterranean Sea, primarily focused on meeting end-users and science-driven requirements, addressing regional challenges in three main topics: i) maritime safety; ii) extreme hazards; iii) environmental transport process. Additionally, the HFR observing and monitoring regional capabilities in the Mediterranean region required to underpin the underlying science and the further development of applications are also analyzed. The outcome of this assessment has allowed us to finally provide a set of recommendations for the future improvement prospects to maximize the contribution in extending the science-based HFR products into societal relevant downstream services to support the blue growth in the Mediterranean coastal areas, helping to meet the UN’s Decade of Ocean Science for Sustainable Development and the EU’s Green Deal goals.

Due to the semi-enclosed nature of the Mediterranean Sea, natural disasters and anthropogenic activities impose stronger pressures on its coastal ecosystems than in any other sea of the world. With the aim of responding adequately to science priorities and societal challenges, littoral waters must be effectively monitored with High-Frequency radar (HFR) systems. This land-based remote sensing technology can provide, in near real-time, fine-resolution maps of the surface circulation over broad coastal areas, along with reliable directional wave and wind information. The main goal of this work is to showcase the current status of the Mediterranean HFR network and the future roadmap for orchestrated actions. Ongoing collaborative efforts and recent progress of this regional alliance are not only described but also connected with other European initiatives and global frameworks, highlighting the advantages of this cost-effective instrument for the multi-parameter monitoring of the sea state. Coordinated endeavours between HFR operators from different multi-disciplinary institutions are mandatory to reach a mature stage at both national and regional levels, striving to: i) harmonize deployment and maintenance practices; ii) standardize data, metadata and quality control procedures; iii) centralize data management, visualization and access platforms; iv) develop practical applications of societal benefit, that can be used for strategic planning and informed decision-making in the Mediterranean marine environment. Such fit-for-purpose applications can serve for search and rescue operations, safe vessel navigation, tracking of marine pollutants, the monitoring of extreme events or the investigation of transport processes and the connectivity between offshore waters and coastal ecosystems. Finally, future prospects within the Mediterranean framework are discussed along with a wealth of socio-economic, technical and scientific challenges to be faced during the implementation of this integrated HFR regional network.

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

In this work, the backward wave breaking process by the presence of flow separation vortices under a solitary wave is studied. Based on a set of non-dimensional variables defined from the Buckingham Π theorem, a set of numerical experiments are performed in order to analyze the effect of varying the submerged obstacle geometry on the surrounding flow and free surface by using a RANS-VOF model. Model simulations are tested against available experiments showing a good performance of numerical results. The structure-submergence ratio and the structure-based Reynolds number modulate the type of breaking (collapsing-plunging). The structure aspect ratio defines the location and number of backward breaking points for rectangular structures and the breaking wave direction for triangular structures (either forward or backward). Moreover, when the flow separation vortex diameter is comparable to the local water depth a backward wave breaking process is originated. The vortex behaves as a rigid body that accelerates the flow at the upper side of the vortex, accumulating mass at the downstream side where a very large slope on the free surface makes the water fall backward due to gravity., A. Cáceres-Euse wants to thank COLCIENCIAS for the scholarship #647. A. Orfila thanks financial support from LAMARCA Project (PID2021-123352OB-C31) funded by MCIN/AEI/ and by “ERDF A way of making Europe”. I. Hernández-Carrasco is supported by the TRITOP Project (UIB2021-PD06) funded by the Universidad de las Islas Baleares – FEDER (UE) . M. Wyssmann thanks support by the Chancellor’s Fellowship awarded by the University of Tennessee at Knoxville

A novel procedure based on filtering and interpolation approaches is proposed to estimate the sea state parameters, including significant wave height, peak wave direction, peak period, peak wavenumber, and peak wavelength in shallow waters using the X-band marine radars. The method compensates the distortions introduced by the radar acquisition process and the power decay of the radar signal along the distance applying image-enhancement techniques instead of empirical and semiempirical calibration methods that use signal-to-noise ratio and in situ measurements as external references. To determine the threshold value for the interpolation approach, the influence of the antenna height on shadowing modulation effects is examined through performing an analysis of variance (ANOVA) that uses data from two X-band radars deployed at 10 and 20 m above MSL. ANOVA results reveal that it is possible to explain the increment of intensities affected by shadowing throughout the distance using an adaptive threshold retrieved from a third-order polynomial function of the mean radar cross section (RCS). Finally, an X-band radar is installed at 13 m above MSL to test the proposed technique. During measurements, the wind and wave conditions varied, and the antenna-look direction remained constant. Errors for H, θ, and T calculated as the difference between estimated and true data show a mean bias and a relative value of 0.05 m (2.72%), 1.52° (5.94%), and 0.15 s (1.67%), respectively. The directional and wave energy spectra derived from radar estimates, acoustic wave and current, ADVs record, as well as JONSWAP formulation are presented to illustrate the improvement resulting from the proposed method over the frequency domain.

The response of the wave climate to tropical cyclones (TCs) is investigated using the significant wave height (SWH) observed from satellites and the WAVEWATCH III (WW3) model. Tropical cyclone wind generates local waves (wind seas) under the TC and longer-period waves (swells) that propagate long distances. The genesis location, intensity, and frequency of tropical cyclones over the global ocean are strongly affected by the phases of the El Niño Southern Oscillation (ENSO). It is shown that the interannual variation of global ocean surface waves in the subtropics during summer is dominated by ENSO-related TC activity. In particular, in the subtropical western North Pacific, the wind power is stronger in the TC season before an El Niño and weaker before a La Niña. These ENSO-related TC variations are shown, through composite and empirical orthogonal function analyses, as well as modeling, to dominate the spatial distribution and temporal variation of the SWH over the western North Pacific. The model confirms that longer-period waves (swells) are driven into northern South China Sea, toward Japan in mid latitudes and toward the central Pacific along the equator due to ENSO-related TC activities. The wind power and SWH over the subtropical western North Pacific lead and regress well with the ENSO index, suggesting that they may potentially serve as useful ENSO predictors., Authors were supported by Taiwan Ministry of Science & Technology Grant#107-2611-M-008-003, awarded to the National Central University.

We present a phenomenological description and dynamical analysis of the Alboran fronts using a realistic simulation at submesoscale resolution. The study is focused on east Alboran fronts emerging within relatively strong flows that separate from the Spanish coast into the basin interior. Despite modest lateral shifting associated with the position of the Alboran anticyclonic gyres and variations in intensity, these fronts present a similar structure and dynamical configuration as the climatological Almeria–Oran front. The statistical analysis of our solution shows that strained-induced frontogenesis is a recurrent submesoscale mechanism associated with these fronts, and the process is assessed in terms of the advective Lagrangian frontogenetic tendencies associated with buoyancy and velocity horizontal gradients. Intermittency in their strength and patterns is indicative of high variability in the occurrence of active frontogenesis in association with the secondary (overturning) circulation across the frontal gradient. As a result, we find many episodes with strong surface fronts that do not have much associated downwelling. Frontogenesis and the associated secondary circulation are further explored during two particular frontal events, both showing strong downwelling of O(1) cm s−1 extending down into the pycnocline. A frontogenetic contribution of turbulent vertical momentum mixing to the secondary circulation is identified in the easternmost region during the cold season, when the dynamics are strongly influenced by the intrusion of the salty Northern Current. The background vertical velocity fields observed during the analyzed events indicate other currents in the submesoscale range, including tidal and topographic internal waves.

The variability of La Guajira upwelling system, in the south-central Caribbean Sea, is strongly influenced by the intensity and location of the atmospheric Caribbean Low-Level Jet (CLLJ), a near-surface branch of the easterlies, as well as by the regional ocean circulation. During favorable conditions (i.e., strong easterlies blowing almost parallel to the coast), upwelling is enhanced and a large amount of primary productivity occurs in La Guajira area. In contrast, during relatively mild wind conditions, the CLLJ is misaligned to the coast and the Caribbean Counter Current (CCC, locally also known as the Darien Current), which forms as a branch from the Panama-Colombia Gyre, flows northeastward over the continental shelf advecting waters from the southwestern Caribbean basin toward La Guajira. The CCC has a clear signature at the surface layer that extends from the Darien Gulf toward La Guajira peninsula during mild wind periods, while disappears during the months of strong winds. The direction and the magnitude of the easterlies, and more specifically of the CLLJ, control the position and pathway of the CCC, which extends more than 900 km in the southern Caribbean Sea during May, June, August, September, and October. The high concentration of chlorophyll-a at the sea surface evidenced by satellite-based color images is semi-seasonally modulated by the CLLJ, which during its relaxation phase allows the irruption of the CCC toward the east up to La Guajira., AO acknowledge financial support from Ministerio de Ciencia, Innovación y Universidad through MOCCA project (RTI2018-095441-B-C21). JS thanks the funding received from Generalitat Valenciana and the European Social Fund (ESF) under Grant APOSTD/2020/254. IH-C was supported by the Vicenç Mut grant funded by the Government of the Balearic Island and the ESF. AC-E wants to thank the University of Toulon—France for the support during his postdoctoral research. ÁM was partially supported by the NOAA grant NA18OAR4310275.

A novel approach for estimating wave energy dissipation on a coral reef barrier is studied using X-Band radar technology. The prominent features of coral reefs, including the delineation of reef morphological structure, wave energy dissipation and wave transformation processes are obtained in a reef lagoon in San Andres Island, Colombia. Results show that reef attenuates incident waves by approximately 75% due to both frictional processes and wave breaking, with an equivalent bottom roughness of 0.20 m and a wave friction factor of 0.18. These parameters are comparable with estimates reported in other shallow coral reef lagoons as well as at seagrass meadows obtained using in-situ measurements. Also, the mean height of the reef elements Hbed and its standard deviation σb are also estimated in the entire radar coverage area. Hbed and σb (0.5 and 7.66 cm respectively) are in the same order of magnitude of measured data reported by previous studies and in good agreement with the geometric parameters proposed by in-canopy flow models for branched species, such as Stylophora and Pocillopora, which are also common in the coral carpets of San Andres Island. This work proposes a completely novel use for X-Band radars by describing prominent features in barrier-reef systems including the delineation of the reef structure and wave energy dissipation., This research has been possible thanks to financial support from Colombian Science and Technology Ministry Projects FP44842-144-2016 (Wave propagation and sediment transport on coral reefs) and 0376-2013 (Developing and modeling of a sea state sensor through the processing of radar signals). Wendy Navarro was supported by Universidad del Norte, COLCIENCIAS (Call 757) and iCOOP+2016 (CSIC) fellowships. Andres Orejarena-Rondon was supported by COLCIENCIAS (Call 727). The authors thank Universidad del Norte for providing equipment and the Colombian Naval Academy Almirante Padilla (Dept. of Oceanography) for field support. Alejandro Orfila acknowledges financial support from the Spanish Government MICINN/FEDER through MOCCA Project (RTI2018-093941-B-C31).

205 pages, 12 figures, 1 table, 3 appendixes.-- Data Availability Statement: All data are accessible from https://apps.ecmwf.int/datasets/data/interim-full-daily/levtype=sfc/, https://www.cpc.ncep.noaa.gov/data/teledoc/telecontents.shtml and from https://resources.marine.copernicus.eu/?option=com_csw&view=details&product_id=SEALEVEL_MED_PHY_L4_REP_OBSERVATIONS_008_051, Effects of wind and waves on the surface dynamics of the Mediterranean Sea are assessed using a modified Ekman model including a Stokes-Coriolis force in the momentum equation. Using 25 years of observations, we documented intermittent but recurrent episodes during which Ekman and Stokes currents substantially modulate the total mesoscale dynamics by two nonexclusive mechanisms: (a) by providing a vigorous input of momentum (e.g., where regional winds are stronger) and/or (b) by opposing forces to the main direction of the geostrophic component. To properly characterize the occurrence and variability of these dynamical regimes, we perform an objective classification combining self-organizing maps and wavelet coherence analyses. It allows proposing a new regional classification of the Mediterranean Sea based on the respective contributions of wind, wave, and geostrophic components to the total mesoscale surface dynamics. We found that the effects of wind and waves are more prominent in the northwestern Mediterranean, while the southwestern and eastern basins are mainly dominated by the geostrophic component. The resulting temporal variability patterns show a strong seasonal signal and cycles of 5–6 years in the total kinetic energy arising from both geostrophic and ageostrophic components. Moreover, the whole basin, specially the regions characterized by strong wind- and wave-induced currents, shows a characteristic period of variability at 5 years. This can be related to climate modes of variability. Regional trends in the geostrophic and ageostrophic currents show an intensification of 0.058 ± 1.43 · 10−5 cm/s per year, Authors acknowledge financial support from MINECO/FEDER through projects MOCCA (RTI2018-093941-B-C31) and from the Balearic Islands Goverment Project ADAPTA. V. Morales-Márquez is supported by an FPI grant from the Ministerio de Ciencia, Innovación y Universidades. I. Hernandez-Carrasco acknowledges the Vicenç Mut contract funded by the Government of the Balearic Island and the European Social Fund (ESF) Operational Programme and the financial support from the Fundacion Universidad Empresa de las Islas Baleares, Spain, through project ALERTA (REF-190121). V. Rossi acknowledges financial support from the European project SEAMoBB, funded by ERA-Net Mar-TERA and managed by ANR (number ANR_17_MART-0001_01, P.I.: A.C.). This work was partially performed while V. Morales-Márquez was staying in MIO (Marseille, France) with the support of FPI grant from the Ministerio de Ciencia, Innovación y Universidades. In addition, this work was carried out in part when A. Orfila was a visiting scientist at the Earth, Environmental and Planetary Sciences Department at Brown University through a Ministerio de Ciencia, Innovación y Universidades fellowship (PRX18/00218), With the institutional support of the ‘Severo OchoaCentre of Excellence’ accreditation (CEX2019-000928-S)

En el ano 2002, el entonces Centro de Control de Contaminacion del Pacifico (CCCP) publico el libro titulado COMPILACION OCEANOGRAFICA DE LA CUENCA PACIFICA COLOMBIANA, lo que seria un referente bibliografico de vital importancia para la caracterizacion de las zonas marino-costeras del Pacifico colombiano, abarcando un total de cinco capitulos en temas tan variados como las particularidades geograficas de la Cuenca Pacifica Colombiana (CPC) y su investigacion oceanografica, la busqueda de la relacion entre las condiciones oceanograficas de la Cuenca y el ciclo de El Nino Oscilacion del Sur (ENOS), ademas del plan cientifico del grupo de investigacion en oceanografia para el periodo 2001-2010. Han transcurrido 18 largos anos desde entonces, y la comunidad cientifica marina del pais, asi como la Autoridad Maritima colombiana y el gremio maritimo requieren no solo una actualizacion de dichas lineas de investigacion, sino tambien mayor cantidad y mejor nivel de detalle en la informacion disponible para la toma de decisiones con base en el rigor tecnico; asi como el claro y amplio soporte de conocimiento del medio en el que se desenvuelven para el diario devenir en sus actividades en el mar y en la costa, teniendo en cuenta que las aguas del gran Pacifico no representan la frontera que separa, sino el puente que une a Colombia y los paises de Oceania y del sudeste asiatico, considerada como la zona con los mercados de mayor proyeccion del mundo. Esta es una mas de las principales razones, sumada a las necesidades de desarrollo y las aspiraciones nacionales de consolidar factores de seguridad multidimensional y de presencia estatal en las areas de frontera, para aprovechar las multiples potencialidades que ofrece el vasto oceano Pacifico para una nacion en desarrollo, y con la aspiracion nacional de llegar a ser una potencia media regional influyente como lo es Colombia. Por lo anterior, el mismo CCCP, ahora denominado Centro de Investigaciones Oceanograficas e Hidrograficas del Pacifico, presenta con orgullo el resultado de un esfuerzo por satisfacer estos requerimientos a traves de la publicacion del titulo COMPILACION OCEANOGRAFICA DEL PACIFICO COLOMBIANO II, el cual consta de siete capitulos que garantizan la continuidad en los anteriores temas y proporciona algunos nuevos, complementando y ampliando la informacion ofrecida por la primera edicion. Dentro de estas lineas de investigacion fueron incluidas las particularidades geograficas y geomorfologia de la CPC, su meteorologia, la investigacion oceanografica en la Cuenca e influencia de los eventos ENOS, las condiciones de oleaje en el Pacifico colombiano, la variabilidad del nivel del mar, la amenaza por tsunami en la CPC y, finalmente, las tendencias en la biogeoquimica del oceano Pacifico Oriental Tropical y Sureste bajo diferentes escenarios de cambio climatico. Bienvenidos entonces a una ventana mas del conocimiento sobre nuestra Cuenca Pacifica Colombiana, desde donde contribuimos a la “consolidacion de Colombia como pais maritimo” y aportamos nuestro pequeno pero representativo grano de arena a la defensa del enorme, hermoso e imponente azul de la bandera. El reconocimiento de los espacios maritimos para el desarrollo de un pais es de vital importancia. Desde su exploracion oceanica y costera, la hidrografia ha representado el conocimiento cientifico sobre el territorio maritimo colombiano y ha brindado informacion, instrumentos y herramientas para una mejor compresion y desarrollo de las actividades maritimas en el pais. La produccion de la cartografia nautica para asegurar las rutas maritimas y el comercio internacional de la nacion es un aspecto fundamental, que a su vez ha cumplido un papel importante en el reconocimiento de las profundidades y el descubrimiento de riquezas economicas y culturales en los fondos oceanicos, ademas de aportar seguridad en la navegacion por el espacio maritimo colombiano y un mejor conocimiento de nuestros litorales y sus potencialidades. La hidrografia entonces ha desempenado eficientemente el rol de fortalecer y desarrollar las riquezas que se encuentran en nuestras aguas jurisdiccionales, y ha sido la disciplina cientifica que ha aportado al reconocimiento de los territorios costeros y oceanicos, y, consecutivamente, al avance en el desarrollo de la infraestructura maritima para el pais. Objetivos que podemos hallar desde sus comienzos y que fueron evidenciados y visibilizados a lo largo de su labor y trabajo en los espacios y frentes marinos, que le han permitido a la Autoridad Maritima Colombiana, a traves de un interes nacional y una vision internacional, mantener una navegacion segura que haga parte del impulso y progreso economico y nacional, en contribucion paralela a los objetivos de desarrollo sostenible de la Organizacion de las Naciones Unidas.

Properly modeling the sediment transport under water waves is critical to understanding morphodynamic processes such as, e.g., sandbar migration at beaches. In the last two decades, the influence of the wave asymmetries (mainly velocity and acceleration skewnesses) has been shown to be a key issue for explaining onshore sandbar migrations under mild wave conditions when wave-induced currents are small. However, there is still a lack of knowledge, and the expressions that relate the sediment transport to the velocity and/or acceleration skewnesses are site-specific. In this work, an intrawave process-based sediment transport model was applied to provide a general expression for bedload sediment transport under wave action within a proper dimensional framework. The new expression is not site-specific, and it is based on the process-based model which was checked against experimental data. Furthermore, the obtained equation has some similarities with expressions in the literature that are discussed, With the funding support of the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S), of the Spanish Research Agency (AEI)

The use of High Frequency Radar (HFR) data is increasing worldwide for operational oceanography and data assimilation, as it provides real-time coastal surface currents at high temporal and spatial resolution. In this work, a Lagrangian based empirical real-time, Short-Term Prediction (L-STP) system is presented in order to provide short term forecasts of up to 48 hours of ocean currents from HFR data. The method is based on the finding of historical gridded analogues of Lagrangian trajectories obtained from HFR surface currents. Then, assuming that the present state will follow the same temporal evolution as did the historical analogue, we obtain a short-term prediction of the surface currents. The method is applied to two HFR systems covering two areas with different dynamical characteristics: the southeast Bay of Biscay and the central Red Sea. The L-STP improves on previous prediction systems implemented for the SE Bay of Biscay and provides good results for the Red Sea study area. A comparison of the L-STP methodology with predictions based on persistence and reference fields has been performed in order to quantify the error introduced by this Lagrangian approach. Furthermore, a temporal sensitivity analysis has been addressed to determine the limit of applicability of the methodology regarding the temporal horizon of Lagrangian prediction. A real-time skill-score has been developed using the results of this analysis which allows to identify periods when the short-term prediction performance is more likely to be low and persistence can be used as a better predictor for the future currents.