Modeliranje neobičnog izranjanja morske vode opaženog duž zapadne obale Jadrana u ljeto 2003. godine

The goal of this research was to simulate and analyze the response of the Western Adriatic Current (WAC) to an abnormal event that occurred in the Adriatic Sea in mid-summer of 2003. At this time, a combination of extremely low discharge from the Po River and from other northwestern rivers caused by the prolonged dry season and the dominant Sirocco wind produced an "unusual" upwelling and caused the WAC to reverse along the northern and central Italian coasts. The simulations employed a high-resolution, low dissipative version of the DieCAST circulation model that was initialized with monthly averaged temperature and salinity data and spun up with a use of climatological wind data. Numerical experiments were performed with the use of COAMPS wind stress and heat flux data. The model runs performed under Sirocco wind forcing in combination with low river discharge (a quarter of the climatic mean) revealed that such these conditions do trigger upwelling and the reversal of the WAC along the Italian coast. The upwelling relaxation caused by changes in the wind direction was also studied. Qualitative simulation results were in agreement with the observations by Poulain et al. (2004).Motivacija ove studije je bila da se simulira i analizira odgovor zapadno-jadranske struje (WAC) na izrazito neobičnu dinamičku situaciju koja se dogodila u Jadranu sredinom ljeta 2003. godine. Tada je kombinacija ekstremno niskih protoka rijeke Po i drugih sjeverozapadnih rijeka (kao posljedica dugotrajnog sušnog razdoblja i dominantnog juga) izazvala tzv. "neobično" izranjanje morske vode i promjenu WAC duž sjeverne i centralne talijanske obale. Za simulacije smo koristili DieCAST model male disipativnosti i visoke rezolucije koji je inicijaliziran podacima srednjih mjesečnih temperatura i saliniteta te klimatološkim vjetrom. Numerički eksperimenti su rađeni pomoću napetosti vjetra i tokova topline dobivenih COAMPS modelom. Model je, simulirajući jugo epizodu u kombinaciji s niskim (četvrtinom klimatološkog prosjeka) riječnim protocima, pokazao da takvi uvjeti uzrokuju izranjanje morske vode i obrtanje WAC duž talijanske obale. Također se proučavaju i karakteristike slabljenja izranjanja vode uzrokovanih promjenama u smjeru vjetra. Rezultati simulacije se uspoređuju kvalitativno s opažanjima koje su napravili Poulain i sur. (2004) te daju dobro podudaranje s postojećim mjerenjima

Modeliranje neobičnog izranjanja morske vode opaženog duž zapadne obale Jadrana u ljeto 2003. godine

The goal of this research was to simulate and analyze the response of the Western Adriatic Current (WAC) to an abnormal event that occurred in the Adriatic Sea in mid-summer of 2003. At this time, a combination of extremely low discharge from the Po River and from other northwestern rivers caused by the prolonged dry season and the dominant Sirocco wind produced an "unusual" upwelling and caused the WAC to reverse along the northern and central Italian coasts. The simulations employed a high-resolution, low dissipative version of the DieCAST circulation model that was initialized with monthly averaged temperature and salinity data and spun up with a use of climatological wind data. Numerical experiments were performed with the use of COAMPS wind stress and heat flux data. The model runs performed under Sirocco wind forcing in combination with low river discharge (a quarter of the climatic mean) revealed that such these conditions do trigger upwelling and the reversal of the WAC along the Italian coast. The upwelling relaxation caused by changes in the wind direction was also studied. Qualitative simulation results were in agreement with the observations by Poulain et al. (2004).Motivacija ove studije je bila da se simulira i analizira odgovor zapadno-jadranske struje (WAC) na izrazito neobičnu dinamičku situaciju koja se dogodila u Jadranu sredinom ljeta 2003. godine. Tada je kombinacija ekstremno niskih protoka rijeke Po i drugih sjeverozapadnih rijeka (kao posljedica dugotrajnog sušnog razdoblja i dominantnog juga) izazvala tzv. "neobično" izranjanje morske vode i promjenu WAC duž sjeverne i centralne talijanske obale. Za simulacije smo koristili DieCAST model male disipativnosti i visoke rezolucije koji je inicijaliziran podacima srednjih mjesečnih temperatura i saliniteta te klimatološkim vjetrom. Numerički eksperimenti su rađeni pomoću napetosti vjetra i tokova topline dobivenih COAMPS modelom. Model je, simulirajući jugo epizodu u kombinaciji s niskim (četvrtinom klimatološkog prosjeka) riječnim protocima, pokazao da takvi uvjeti uzrokuju izranjanje morske vode i obrtanje WAC duž talijanske obale. Također se proučavaju i karakteristike slabljenja izranjanja vode uzrokovanih promjenama u smjeru vjetra. Rezultati simulacije se uspoređuju kvalitativno s opažanjima koje su napravili Poulain i sur. (2004) te daju dobro podudaranje s postojećim mjerenjima

Effects of mesoscale eddies on behavior of an oil spill resulting from an accidental deepwater blowout in the Black Sea: an assessment of the environmental impacts

Because of the environmental sensitivity of the Black Sea, as a semi-enclosed sea, any subsea oil spill can cause destructive impacts on the marine environment and beaches. Employing numerical modeling as a prediction tool is one of the most efficient methods to understand oil spill behavior under various environmental forces. In this regard, a coupled circulation/deepsea oil spill model has been applied to the Black Sea to address the behavior of the oil plume resulting from a representative hypothetical deepwater blowout. With climatological forcing, the hydrodynamic module based on DieCAST ocean circulation model realistically reproduces seasonally-varying circulation from basin-scale dominant structures to meso- and sub-mesoscale elements. The oil spill model utilizes pre-calculated DieCAST thermo-hydrodynamic fields and uses a Lagrangian tracking algorithm for predicting the displacement of a large number of seeded oil droplets, the sum of which forms the rising oil plume resulting from a deepwater blowout. Basic processes affecting the transport, dispersal of oil and its fate in the water column are included in the coupled model. A hypothetical oil source was set at the bottom, at the northwestern edge of the Shatsky Ridge in the area east of the Crimea Peninsula where the oil exploration/development is likely to be planned. Goals of the study are to elucidate the behavior of the subsea oil plume and assess scales of contamination of marine environment and coastlines resulting from potential blowouts. The two 20-day scenarios with the oil released by a hypothetical blowout were examined to reveal combined effects of the basin-scale current, near-shore eddies, and winds on the behavior of the rising oil plume and its spreading on the surface. Special attention is paid to the Caucasian near-shore anticyclonic eddy which is able to trap surfacing oil, detain it and deliver it to shores. The length of contaminated coastlines of vulnerable Crimean and Caucasian coasts are assessed along with amounts of oil beached and deposited

Mesoscale Eddies in the Black Sea and Their Impact on River Plumes: Numerical Modeling and Satellite Observations

The Northeast Caucasian Current (NCC) is the northeastern part of the cyclonic Rim Current (RC) in the Black Sea. As it sometimes approaches the narrow shelf very closely, topographically generated cyclonic eddies (TGEs) can be triggered. These eddies contribute to intense, along- and cross-shelf transport of trapped water with enhanced self-cleaning effects of the coastal zone. Despite intense studies of eddy dynamics in the Black Sea, the mechanisms of the generation of such coastal eddies, their unpredictability, and their capacity to capture and transport impurities are still poorly understood. We applied a 3-D low-dissipation model DieCAST/Die2BS coupled with a Lagrangian particle transport model supported by analysis of optical satellite images to study generation and evolution of TGEs and their effect on river plumes unevenly distributed along the northeastern Caucasian coast. Using the Furrier and wavelet analyses of kinetic energy time series, it was revealed that the occurrence of mesoscale TGEs ranges from 10 up to 50 days. We focused on one particular isolated anticyclonic TGE that emerged in late fall as a result of instability of the RC impinging on the abrupt submarine area adjoining the Pitsunda and Iskuria capes. Being shed, the eddy with a 30-km radius traveled along the coast as a coherent structure during ~1.5 months at a velocity of ~3 km/day and vertical vorticity normalized by the Coriolis parameter ~(0.1 ÷ 1.2). This eddy captured water from river plumes localized along the coast and then ejected it to the open sea, providing an intense cross-shelf transport of riverine matter

High-Resolution Numerical Model for Predicting the Transport and Dispersal of Oil Spilled in the Black Sea

The coupled DieCAST-SSBOM (Shirshov-Stony Brook Oil spill transport Model) circulation-oil spill transport model is used to predict the transport and dispersal of contaminants resulting from representative hypothetical oil spills in the Black Sea. With climatological forcing, the DieCAST model realistically simulates many of the dominant mesoscale features of seasonally-varying large scale circulation and meso-scale features of the circulation including the Rim Current, anticyclonic coastal eddies, headland eddy shedding and vertical stratification. The oil spill model ingests DieCAST surface currents and employs a Lagrangian tracking algorithm to predict the motion of a large number of seeded particles, the sum of which (~1 million) form the oil plume. Basic processes affecting the transport of oil and its fate (advection, sinking, evaporation, etc.) are included as parameters. Various scenarios of hypothetical blowouts of oil in different regions of the sea are simulated and discussed as to their structure, transport and likelihood of coastal contamination. The ultimate objective is to develop an operational oil slick model forced with synoptic winds and air-sea interaction

Variability of turbulent quantities in the tidal bottom boundary layer : Case study in the eastern English Channel

International audienceTidal current structure and turbulent quantities within a tidal bottom boundary layer (BBL) have been examined using an upward-looking acoustic Doppler current profiler (ADCP). The instrument was deployed on the seafloor, off the north-eastern French coast in the eastern English Channel over 12 tidal cycles and covered the period of the transition from mean spring to neap tide. Forcing regimes varied from calm to moderate storm conditions during the deployment. For the study of turbulent quantities in the BBL, we have chosen a calm period, when an effect of surface waves on the velocity structure was negligible. Stresses were found to vary regularly with the predominantly semidiurnal tidal flow, with the along-shore stress being generally greater during the flood flow (∼3.0 Pa) than during the ebb flow (∼−1.5 Pa). The turbulent kinetic energy (TKE) production rate, P, TKE density, Q, and its dissipation rate, ε, followed a nearly regular cycle with close to quarter-diurnal period. Near the seabed, peak values of P, Q and ε were found to be 0.5 W m−3, 0.5 m2 s−2 and, 0.04 W m−3, respectively, during the flood while, during the ebb, these quantities reached lesser values: 0.1 W m−3, 0.1 m2 s−2 and 0.03 W m−3, respectively. Near the bottom, eddy viscosity, Az, peak ranged from about 0.1 m2 s−1 during the flood to 0.03 m2 s−1 during the ebb flow. Away from the bottom, Az increased to reach a maximum near the mid-depth. Time-depth variation of the P/ε ratio indicated that the turbulence in the BBL, most of the time, was at a non-equilibrium state (P/ε≠1). The largest deviation from the equilibrium occurred during the flood, when P/ε exceeded about one decade near the bottom. During the ebb, P/ε was close to the equilibrium state, slightly decreasing with height above the bottom. Results are found to be in a good agreement with those of the other researches working on direct measurements of turbulence in tidal flows

Calculation-Driven Regioselective Functionalization of the Imidazo[1,2-a]pyrazine Scaffold via Zinc and Magnesium Organometallic Intermediates

Straightforward calculations such as determinations of pKa values and N-basicities have allowed the development of a set of organometallic reactions for the regioselective functionalization of the underexplored imidazo[1,2 a]pyrazine. Thus, regioselective metalations of 6 chloroimidazo[1,2-a]pyrazine using TMP-bases (TMP = 2,2,6,6-tetramethylpiperidyl) such as TMPMgCl∙LiCl and TMP2Zn∙2MgCl2∙2LiCl provided Zn- and Mg-intermediates, that after quenching with various electrophiles gave access to polyfunctionalized imidazopyrazine heterocycles. Additionally, the use of TMP2Zn∙2MgCl2∙2LiCl as base for the first metalation allowed an alternative regioselective metalation. Nucleophilic additions at position 8 as well as selective Negishi cross-couplings complete the set of methods for selectively decorating this heterocycle of the future