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Plastic contamination of coastal seas causes ecological and economic concerns; particularly in nations reliant on marine ecosystems for livelihoods, industries, and tourism, such as Indonesia. Within the growing literature concerning plastic contamination at the sea surface, spatiotemporal variability has been recognised for some time. Yet, efforts to explain and integrate underlying processes causing this variability are still limited, when addressing potential impacts and mitigation. Using a regional ocean modelling system and Lagrangian particle tracking, the first aim of this study was to assess the seasonal and inter-annual variability of plastic pathways and densities emitted from the Top 20 rivers in Indonesia. The second aim was to test the efficiency of two hypothetical mitigation approaches for select Areas of Interest (AOIs): at the river source, or within the AOIs. We found that high accumulations within the archipelago overlap with identifiable convergent fronts, which varied both in location and magnitude depending on monsoon seasons and El Nino Southern Oscillation (ENSO). Furthermore, we found interannual differences in the amount of contributing rivers, contamination levels, and residence times of particles within our selected AOIs. These differences were not consistent between AOIs, where for example one area showed an order of magnitude increase in densities during an El Nino year, for another this was true during a neutral ENSO. In conclusion, the localised variability of efficiency in mitigation strategies underlines the need to account for spatiotemporal differences in informing management approaches. The drivers of this variability can be predictable in the short to long-term., The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)

Sea-level oscillations and associated current variability, responding to meteorological forcing with periods in the range of 3-15 days (“weather-band”), are ubiquitous along continental shelves globally. However, the investigation of these weather-band sea-level (WBSL) variations over a long period (~10 years) and the understanding their forcing are limited, particularly along North-West Australia. The aims of this research were to: (1) investigate WBSL along North-West Australia from 2009 to 2018; (2) assess the different types of meteorological forcing that contribute to WBSL; and (3) evaluate different meteorological drivers that contribute to the generation of continental shelf waves (CSWs). These aims were achieved through the analysis of long-term sea level records from 7 tide gauge stations, between Port Hedland and Geraldton, separated by 1400 km, together with concurrent meteorological data. The most energetic weather events occurred during the cyclone season (Nov-Apr) and other strong weather events were present during austral winter, particularly along the southern stations. WBSL was linked to five different meteorological forcing conditions: tropical storms (cyclones and depressions); frontal systems, west coast trough and sub-tropical high pressure systems. Over the period of analysis, ~50% of WBSL were attributed to propagating signals and were identified as continental shelf waves (CSW). These waves had mean phase speeds of 4.92±0.6m/s within the study region. CSW’s occurred throughout the year with the most energetic being generated by tropical cyclones. Other WBSL signals were generated by large scale weather systems that resulted in simultaneous sea level changes over the study region., The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)

Il canale tra le isole di Sicilia e Malta si trova in una delle principali rotte marittime del Mediterraneo e in una regione strategica per le piattaforme di estrazione petrolifera, quindi seriamente esposta al rischio di eventi di sversamento di idrocarburi in mare. Ciò può costituire una grave minaccia agli ecosistemi locali e alle attività economiche, tra le quali il turismo e la pesca. I danni derivanti da un eventuale sversamento sarebbero incalcolabili per l'arcipelago maltese, dove le risorse marine ed il turismo rappresentano i principali proventi economici e, in maniera analoga, per la Sicilia. Le misure di prevenzione e di mitigazione, insieme a un rapido intervento e a un processo decisionale stabile e solido in caso di situazioni di emergenza, aiutano a minimizzare i rischi e a ridurre gli impatti. Grazie alla tecnologia radar ad alta frequenza (HF), la rete CALYPSO rappresenta lo strumento essenziale per il monitoraggio delle correnti superficiali del mare in tempo reale. La tecnologia radar HF fornisce uno strumento unico per determinare le correnti superficiali in tempo 'quasi' reale, consentendo l’applicazione efficace di modelli numerici di dispersione d’inquinanti in mare. Tale metodologia permette di prevedere origine e destinazione dell’inquinante attraverso l'assimilazione dei dati nei modelli di circolazione oceanica, o tramite previsioni statistiche delle correnti marine a breve termine. La rete CALYPSO, operativa da agosto 2012, è attualmente costituita da quattro sistemi SeaSonde (CODAR) che funzionano nella banda di frequenza dei 13.5 MHz. Le misure ottenute sono state ampiamente validate utilizzando sia correntometri che drifters che hanno ripetutamente fornito prove evidenti dell'affidabilità dei dati acquisiti. Le osservazioni a lungo termine hanno consentito una nuova descrizione oceanografica dell'area, documentando la presenza di una quantità di caratteristiche finora mai segnalate con un simile dettaglio spaziale e temporale. The Malta-Sicily Channel is located within one of the busiest commercial routes in the Mediterranean Sea. Due to the presence of oil tankers and oil rigs, this stretch of sea is prone to oil spill events (both deliberate or accidental) with potentially significant impacts on the local ecosystems and economic activities, such as fishing and tourism activities. Prevention and mitigation measures are needed to reduce risks and impacts. Within this framework the high-frequency (HF) radar technology is able to monitor in near-real time surface currents and waves, thus representing an extraordinary tool to reduce the impact of marine pollution events. Assimilation of near real-time surface current data into numerical models greatly improves the short-term forecast of sea state conditions and, consequently, the forecast of oil spill movements and fate. This paper describes the characteristics and potential of the CALYPSO HF radar observing system. The network, in operation since August 2012, currently includes 4 SeaSonde (CODAR) HF radars working at 13.5 MHz. The system is able to provide 2D surface current maps of the Malta-Sicily Channel with high resolution over a 3x3 km grid, every hour. Surface currents derived by the CALYPSO system were validated using independent measurements (acoustic current meter and drifters), and their accuracy extensively proven. The long term datasets show unprecedented descriptions of surface currents patterns within the studied area.

Located in one of the main shipping lanes in the Mediterranean Sea, and in a strategic region for oil extraction platforms, the Malta-Sicily channel is exposed to significant oil spill risks. Shipping and extraction activities constitute a major threat for marine areas of relevant ecological value in the area, and impacts of oil spills on the local ecosystems and the economic activities, including tourism and fisheries, can be dramatic. Damages would be even more devastating for the Maltese archipelago, where marine resources represent important economic assets. Additionally, North Africa coastal areas are also under threat, due to their proximity to the Malta-Sicily Channel. Prevention and mitigation measures, together with rapid-response and decision-making in case of emergency situations, are fundamental steps that help accomplishing the tasks of minimizing risks and reducing impacts to the various compartments. Thanks to state-of-art technology for the monitoring of sea-surface currents in real-time under all sea-state conditions, the CALYPSO network of High-Frequency Radars represents an essential and invaluable tool for the specific purpose. HF radars technology provide a unique tool to track surface currents in near-real time, and as such the dispersion of pollutants can be monitored and forecasted and their origin backtracked, for instance through data assimilation into ocean circulation models or through short-term data-driven statistical forecasts of ocean currents. The network is constituted of four SeaSonde systems that work in the 13.5MHz frequency band. The network is operative since August 2012 and has been extensively validated using a variety of independent platforms and devices, including current meter data and drifting buoys. The latter provided clear evidences of the reliability of the collected data as for tracking the drifting objects. Additionally, data have provided a new insight into the oceanographic characteristics of the region, documenting the presence of a number of previously unreported features. The observing network represents an unique opportunity that exploit HF radar in coastal seas to meet Europe's needs for operational mapping of the surface ocean. Additionally, it provides expertise and support for a new generation of scientists and technical staff.

Report on first methodological improvements on retrieval algorithms and HF radar network design. Results obtained to date in Subtasks 3.2.1-3.2.2 will provide first recommendations on the implementation of improved techniques for HF radar systems (M24)

La mappatura delle variabili di qualità delle acque, quali la clorofilla-a (CHL-a) e la Temperatura Superficiale del mare (SST-Sea Surface Temperature) viene effettuata routinariamente dai sensori satellitari per l’osservazione della terra. I satelliti forniscono una visione sinottica di questi parametri, praticamente in tempo reale e su larga scala. Ad ogni modo, le relazioni tra i parametri di qualità delle acque e le forzanti fisiche che ne determinano le variabilità spazio-temporali, quali campi di vento e di correnti, necessitano uno studio approfondito.

Illegal migration often results in dramatic loss of lives that can be avoided with timely Search and Rescue (SAR) interventions; such SAR services require accurate information such as on sea-state and operational tools such as trajectory forecasting for floating objects at sea. The maritime transport of oil crossing this region accounts for 25% of the global maritime traffic and for nearly 7% of the world oil accidents over the last 25 years. In combination with localized oil extraction plants existing in the shelf zones this situation presents a serious threat to both the open-sea and coastal-zone habitats, with consequent impacts on local economic activities as tourism and fisheries, impacts on ecosystems and losses in revenue. In the case of both accidental/deliberate oil spills or drifting-vessel emergency, an operative response chain must include both the detection and the trajectory prediction steps, that take advantage of the most appropriate methodologies and data availability such as: updated meteorological information, near-surface current measurements, and hydrodynamic models with oil spill weathering processes modules. Indeed, both the knowledge of initial positions and an accurate, effective and prompt prediction of their future pathways are of fundamental importance to optimize response activities, shortening the intervention time and increasing their efficacy. In the particular case of oil spills, the knowledge of spill trajectories is very important to anticipate impacts on economic and environmental assets on threatened coasts; the provision of accurate information to decision makers together with training in best practices and damage recovery methods need to be adopted in order to minimize spill impacts.

Rapporto tecnico della campagna oceanografica PREPARED 2014 nell'ambito del progetto EU-H2020 EuroFleets 2

Coastal radars provide information on the environmental state of oceans, namely maps of surface currents at time intervals of the order of one hour with spatial coverage of the order of several km, depending on the transmission frequency. The observations are of crucial importance for monitoring ports and ship tracks close to the coast, providing support for safe navigation in densely operated areas and fast response in case of accidents at sea, such as oil spill or search and rescue. Besides these applications, coastal radar observations provide fundamental support in MPAs surveillance, connectivity and marine population circulation. In the framework of the Italian RITMARE flagship project coordinated by CNR (Consiglio Nazionale delle Ricerche), a coastal radar network has been designed and implemented with a number of innovative characteristics. The network includes both HF and X-band radars, allowing coverage of wide areas with different spatial and temporal resolutions. HF radars cover up to 80 km with a spatial resolution ranging between 1 and 5 km, while X-band radars provide 5 km coverage with a spatial resolution of 10 m. Joining these two capabilities, the RITMARE coastal radar network enables both a highly effective coverage of wide coastal areas and integrated monitoring of different phenomena, thus allowing the collection of current and wave parameters and detection of bathymetries of both open sea and coastal areas. A dedicated action to foster interoperability among data providers has been undertaken within RITMARE; an IT framework is under development to provide software tools for data collection and data sharing. It suggests standard, data format definitions, Quality Control strategies, data management and dissemination policies. In particular, the implementation of tools exploits both standards of OGC (Open Geospatial Consortium) and web services offered to manage, access and deliver geospatial data. Radar data produced in RITMARE by the coastal radar network represent a challenge to the nowadays definition of OGC web services: the network will suggest and test solutions.

Surface patterns of the low-frequency current in a 20 × 30 km 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 3 m/sec). Mean flow and vorticity spatial distributions were discussed for different wind conditions. The coastal area about 5 km 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 4–5 km 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 5 km 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 > 0.7 m s-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.

Lo studio della circolazione costiera e dello scambio di flussi d’acqua tra la laguna di Venezia ed il mare aperto attraverso le sue bocche di porto è stato uno dei temi principali di un progetto di ricerca, finanziato dal CORILA (Consorzio Ricerche Lagunari) negli anni 2001-2004 Un aspetto preso in considerazione in questa ricerca è il ruolo fondamentale che le correnti marine superficiali giocano nell’ambiente costiero per la loro influenza nell’ecosistema, e come il campo di corrente adiacente alle bocche, nella fascia costiera fuori della laguna, interviene nell’efficienza dei flussi attraverso le bocche nel rinnovare le acque della laguna. Lo studio della circolazione superficiale e del suo impatto sulle caratteristiche ambientali richiede l’acquisizione di lunghe serie di dati di corrente di alta qualità, che spesso risultano carenti a causa delle limitazioni nelle tecniche di misura disponibili. Una nuova tecnica di misura basata su una rete di sistemi Radar HF per produrre le mappe della corrente marina superficiale al largo della bocca di porto di Malamocco, è stata utilizzata, permettendo l’analisi della completa serie temporale dal 2001 al 2003. Questa tecnologia, già ampiamente utilizzata negli Stati Uniti e sperimentata per la prima volta in Italia dal gruppo di ricerca del CNR – ISMAR di Venezia, in collaborazione con l’OGS di Trieste ha permesso di superare le difficoltà fino ad ora incontrate nello studio delle correnti in ampie aree di mare. La circolazione costiera é stata studiata con l’utilizzo di radar costieri ad alta frequenza (25-30 MHz). Il radar utilizza due sistemi di antenne ricetrasmittenti posizionate sulle isole di Lido e di Pellestrina, più una terza antenna Rx/Tx installata sulla piattaforma “Acqua Alta”, 8 miglia al largo delle bocche di porto. Con questa configurazione é stata coperta dalle misure una zona larga 20km davanti alla bocca di Malamocco, con una risoluzione spaziale di 1km, ottenendo le serie temporali desiderate.

The analysis of bivariate space–time series with linear and circular components is complicated by (1) multiple correlations, across time, space and between variables, (2) different supports on which the variables are observed, the real line and the circle, and (3) the periodic nature of circular data. We describe a multivariate hidden Markov model that includes these features of the data within a single framework. The model integrates a circular von Mises Markov field and a Gaussian Markov field, with parameters that evolve in time according to a latent (hidden) Markov chain. It allows to describe the data by means of a finite number of time-varying latent regimes, associated with easily interpretable components of large-scale and small-scale spatial variation. It can be estimated by a computationally feasible expectation–maximization algorithm. In a case study of sea currents in the Northern Adriatic Sea, it provides a parsimonious representation of the sea surface in terms of alternating environmental states.

Two years of sea surface current measurements acquired since August 2012 by High-Frequency SeaSonde radars over the relatively shallow shelf area dividing the Maltese Islands from Sicily (the Malta - Sicily Channel), are used to characterize the surface tidal currents in the region. Tidal currents are generally weak and concentrated in the semidiurnal and diurnal bands, barely exceeding 3cms-1 in the semidiurnal band (M2, S2), and below 6cms-1 in the diurnal band (K1, O1). In the middle part of the basin, the M2 currents oscillate along the main Channel axis; on the contrary the S2 oscillations are oriented along the energetic Atlantic Ionian Stream (AIS) flow. Diurnal tides have a more circular pattern, also following the AIS path and with a significant intensification in proximity of the shelf break, thus suggesting a substantial contribution from internal tides in the region. Phase contours suggest the presence of amphidromic points for both the semidiurnal and diurnal constituents, located in the central area of the Channel for S2, O1 and K1, but slightly shifted towards north-west for the M2 component.

Chlorophyll-a (CHL-a) and Sea Surface Temperature (SST), amongst others, are proxies or indicators for water quality and can be easily retrieved synoptically and almost in near-real time through satellite remote-sensing. However, as they evolve in space and time in response to winds and currents, a full resolution of the temporal and spatial scales of these latters is required and their influence in shaping the distribution of water quality parameters needs to be assessed. While providing synoptic views and revealing mesoscale features, satellites suffer, indeed, from inadequate representation of sub-grid physical processes and lack of temporal resolution. Conventional point-wise measurements provide data to study high-frequency motions such as tides or high-frequency wind-driven circulation, lacking on the other hand of the spatial resolution required to resolve their spatial variability. We show here that a combined use of near-surface currents, available through High-Frequency (HF) radars, and satellite data (e.g., TERRA and AQUA/MODIS, VIIRS/NPP), are complementary tools as they help solving both fine-scale structures, especially at the coastal boundaries where satellite imageries lack of the required resolution, as well as satellite-derived mesoscale structures are fundamental aid to understand and interpret finer-scale structures in terms of larger-scale ocean dynamics.