scholarly journals Assymmetric eddy populations in adjacent basins – a high resolution numerical study of the Tyrrhenian and Ligurian Seas

2012 ◽  
Vol 9 (6) ◽  
pp. 3521-3566 ◽  
Author(s):  
R. M. A. Caldeira ◽  
X. Couvelard ◽  
E. Casella ◽  
A. Vetrano
Keyword(s):  
High Resolution ◽  
Ocean Circulation ◽  
Numerical Solutions ◽  
Numerical Study ◽  
Mesoscale Eddy ◽  
Leeward Side ◽  
Boundary Current ◽  
High Concentration ◽  
Eddy Activity ◽  
Tyrrhenian Basin

Abstract. A high-resolution ocean circulation modelling system forced with a high-resolution numerical wind product was used to study the mesoscale and sub-mesoscale eddy population of the North-Western Mediterranean Sea, contrasting eddy-activity between the Tyrrhenian and Ligurian sub-basins. Numerical solutions reproduced some of the known regional dynamics, namely the occurrence and oceanic implications of Mistral events, the convective cell leeward of the Gulf of Lion, as well as the Balearic frontal system. Calculated transport across the Corsica Channel followed a similar trend, when compared to the transport computed from a moored current meter. The analysis of the results showed that surface eddy activity is mostly confined to the boundary-currents, whereas in the deeper layers most eddies are concentrated on the central-deeper part of the basins. The Liguro-Provençal basin shows a much higher concentration of intermediate and deep-water eddies, when compared to the Tyrrhenian basin. Sub-mesoscale surface eddies tend to merge and migrate vertically onto intermediate waters. Intense eddy activity in the boundary-current surrounding the Liguro-Provençal Gyre, concentrate high-productivity, manifested by higher concentrations of mean sea surface chlorophyll, in the central part of the gyre, defined herein as the Ligurian Productive Pool (LPP). On average, the Tyrrhenian was mostly oligotrophic except for a small productive vortice in the south-eastern (leeward) side of Corsica. The transport in the Tyrrhenian Gyre, and across the basin is one order of magnitude higher than the transport calculated for the Liguro-Provençal basin. A high concentration of eddies in the passage between the Balearic Archipelago and Sardinia suggests retention and longer residence times of nutrient rich water in the "Ligurian pool", compared to a "fast draining" Tyrrhenian basin. Previous studies support the cyclonic gyre circulation generated in the Liguro-Provençal basin but more studies are needed to address the surface and deep mesoscale activity of the Tyrrhenian basin.

scholarly journals THE BIFURCATION OF THE WESTERN BOUNDARY CURRENT SYSTEM OF THE SOUTH ATLANTIC OCEAN

2014 ◽  
Vol 32 (2) ◽  
pp. 241 ◽  
Author(s):  
Janini Pereira ◽  
Mariela Gabioux ◽  
Martinho Marta Almeida ◽  
Mauro Cirano ◽  
Afonso M. Paiva ◽  
...  
Keyword(s):  
High Resolution ◽  
Atlantic Ocean ◽  
Ocean Circulation ◽  
South Atlantic ◽  
Western Boundary Current ◽  
South Atlantic Ocean ◽  
Western Boundary ◽  
Intermediate Water ◽  
Boundary Current ◽  
The South

ABSTRACT. The results of two high-resolution ocean global circulation models – OGCMs (Hybrid Coordinate Ocean Model – HYCOM and Ocean Circulation andClimate Advanced Modeling Project – OCCAM) are analyzed with a focus on the Western Boundary Current (WBC) system of the South Atlantic Ocean. The volumetransports are calculated for different isopycnal ranges, which represent the most important water masses present in this region. The latitude of bifurcation of the zonalflows reaching the coast, which leads to the formation of southward or northward WBC flow at different depths (or isopycnal levels) is evaluated. For the Tropical Water,bifurcation of the South Equatorial Current occurs at 13◦-15◦S, giving rise to the Brazil Current, for the South Atlantic Central Water this process occurs at 22◦S.For the Antarctic Intermediate Water, bifurcation occurs near 28◦-30◦S, giving rise to a baroclinic unstable WBC at lower latitudes with a very strong vertical shearat mid-depths. Both models give similar results that are also consistent with previous observational studies. Observations of the South Atlantic WBC system havepreviously been sparse, consequently these two independent simulations which are based on realistic high-resolution OGCMs, add confidence to the values presentedin the literature regarding flow bifurcations at the Brazilian coast.Keywords: Southwestern Atlantic circulation, water mass, OCCAM, HYCOM. RESUMO. Resultados de dois modelos globais de alta resolução (HYCOM e OCCAM) são analisados focando o sistema de Corrente de Contorno Oeste do Oceano Atlântico Sul. Os transportes de volume são calculados para diferentes níveis isopicnais que representam as principais massas de água da região. É apresentada a avaliação da latitude de bifurcação do fluxo zonal que atinge a costa, permitindo a formação dos fluxos da Corrente de Contorno Oeste para o sul e para o norte emdiferentes níveis de profundidades (ou isopicnal). Para a Água Tropical, a bifurcação da Corrente Sul Equatorial ocorre entre 13◦-15◦S, originando a Corrente do Brasil, e para a Água Central do Atlântico Sul ocorre em 22◦S. A bifurcação daÁgua Intermediária Antártica ocorre próximo de 28◦-30◦S, dando um aumento na instabilidade baroclínica da Corrente de Contorno Oeste em baixas latitudes e com um forte cisalhamento vertical em profundidades intermediárias. Ambos os modelos apresentamresultados similares e consistentes com estudos observacionais prévios. Considerando que as observações do sistema de Corrente de Contorno Oeste do Atlântico Sul são escassas, essas duas simulações independentes com modelos globais de alta resolução adicionam confiança aos valores apresentados na literatura, relacionadosaos fluxos das bifurcações na costa do Brasil.Palavras-chave: circulação do Atlântico Sudoeste, massas de água, OCCAM, HYCOM.

Multidecadal simulation of the tropical and subtropical South Atlantic Ocean with a high resolution ocean model forced by ERA-5 reanalysis data

2020 ◽  
Author(s):  
Martin Schmidt ◽  
Hadi Bordbar ◽  
Fernanda Nascimento ◽  
Claudia Frauen
Keyword(s):  
High Resolution ◽  
Wind Stress ◽  
Ocean Circulation ◽  
Reanalysis Data ◽  
Ocean Model ◽  
Ecosystem Dynamics ◽  
Boundary Current ◽  
Wind Stress Curl ◽  
Data Set ◽  
Upwelling Intensity

<p>High resolution regional ocean circulation models are needed to investigate regional ecosystem dynamics. However, these models may suffer from biases due to shortcomings in reanalysis datasets like NCEP or ERA-Interin, that have traditionally been used as atmospheric forcing. More realistic results can be achieved by replacing the reanalysed wind with scatterometer based winds. However, inconsistencies between different scatterometers like ASCAT and QuikSCAT introduce new uncertainty, which prevents a discussion of long-term trends in these models. The ERA-5 reanalysis offers a new consistent data set to force highly resolving regional ocean models. Based on such a simulation we analyse trends and anomalies in poleward currents in the Eastern Boundary Current off Southern Africa and Northern Benguela upwelling intensity due to changing wind stress and wind stress curl. Model results are validated with remote sensing as well as shipborne and mooring data. Further, variability of oxygen conditions in the Northern Benguela and the Angola Gyre oxygen minimum zone is discussed. </p>

scholarly journals Winter mixing, mesoscale eddies and eastern boundary current: Engines for biogeochemical variability of the central Red Sea during winter/early spring period

2018 ◽  
Author(s):  
Nikolaos D. Zarokanellos ◽  
Burton H. Jones
Keyword(s):  
Remote Sensing ◽  
Red Sea ◽  
Mixed Layer ◽  
Mesoscale Eddy ◽  
Early Spring ◽  
Boundary Current ◽  
Surface Cooling ◽  
Eddy Activity ◽  
Eastern Boundary ◽  
Eastern Boundary Current

Abstract. The central Red Sea (CRS) has been shown to be characterized by significant eddy activity throughout the year. Weakened stratification in winter may lead to enhanced vertical exchange contributing to physical and biogeochemical processes. In the winter of 2014–2015, we began an extended glider time series to monitor the CRS where eddy activity is significant. Remote sensing and glider observations that include temperature, salinity, oxygen, carbon dissolved organic matter (CDOM), chlorophyll fluorescence (CHL) and multi-wavelength optical backscatter have been used to characterize the effects of winter mixing, eddy activity and lateral advection. During winter and early spring, mixing up to 90m driven by surface cooling and strong winds combined with eddy features was insufficient to penetrate the nutricline and supply nutrients into the upper layer. However, the mixing events did disperse the phytoplankton from the deep chlorophyll maximum throughout the upper mixed layer (ML) increasing the chlorophyll signature detected by ocean colour imagery. In early spring, the eastern boundary current (EBC) is evident in CRS. The EBC brings relative high concentrations of CHL and CDOM along with lower oxygen concentrations indicative of previous nutrient availability. In addition to the vertical mixing, mesoscale eddy activity cause 160 m vertical displacement of the 180 µM isopleth of oxygen, proxy of the nutricline interface. Within the cyclonic feature, this oxygen isopleth shallowed to 60 m, well within the euphotic layer. Remote sensing analyses indicate that these eddies also contribute to significant horizontal dispersion, including the exchange between the open sea and coastal coral reef ecosystems. When the phytoplankton is distributed through the mixed layer clear diel variability was evident in CHL concentration. The biogeochemical responses provide a sensitive indicator of the mixing and eddy processes that may not be detectable via remote sensing. Sustained in situ autonomous observations were essential to understand these processes.

scholarly journals Modeling of the Turkish Strait System Using a High Resolution Unstructured Grid Ocean Circulation Model

2021 ◽  
Vol 9 (7) ◽  
pp. 769
Author(s):  
Mehmet Ilicak ◽  
Ivan Federico ◽  
Ivano Barletta ◽  
Sabri Mutlu ◽  
Haldun Karan ◽  
...  
Keyword(s):  
High Resolution ◽  
Ocean Circulation ◽  
Layer Structure ◽  
Circulation Model ◽  
Open Boundary ◽  
The Black Sea ◽  
Leeward Side ◽  
Marmara Sea ◽  
Open Boundary Conditions ◽  
Bosphorus Strait

The Turkish Strait System, which is the only connection between the Black Sea and the Mediterranean Sea, is a challenging region for ocean circulation models due to topographic constraints and water mass structure. We present a newly developed high resolution unstructured finite element grid model to simulate the Turkish Strait System using realistic atmospheric forcing and lateral open boundary conditions. We find that the jet flowing from the Bosphorus Strait into the Marmara creates an anticyclonic circulation. The eddy kinetic energy field is high around the jets exiting from the Bosphorus Strait, Dardanelles Strait, and also the leeward side of the islands in the Marmara Sea. The model successfully captures the two-layer structure of the Sea of Marmara. The volume transport at the Bosphorus is around 120 km3/year which is consistent with the recent observations. The largest bias in the model is at the interface depth due to the shallower mixed layer.

scholarly journals Global changes in oceanic mesoscale currents over the satellite altimetry record

2020 ◽  
Author(s):  
Josue Martinez-Moreno ◽  
Andrew Hogg ◽  
Matthew England ◽  
Navid C. Constantinou ◽  
Andrew E. Kiss ◽  
...  
Keyword(s):  
Climate Change ◽  
Ocean Circulation ◽  
Climate Model ◽  
Global Climate ◽  
Future Climate ◽  
Future Climate Change ◽  
Global Changes ◽  
Boundary Current ◽  
Eddy Activity ◽  
Mesoscale Currents

Abstract Oceanic eddies play a profound role in mixing tracers such as heat, carbon, and nutrients, thereby regulating regional and global climate. Yet, it remains unclear how global oceanic eddy kinetic energy has evolved over the past few decades. Furthermore, coupled climate model predictions generally fail to resolve oceanic mesoscale dynamics, which could limit their accuracy in simulating future climate change. Here we show a global statistically significant increase of the eddy activity using two independent observational datasets of mesoscale variability, one directly measuring currents and the other from sea surface temperature. Regions characterized by different dynamical processes show distinct evolution in the eddy field. For example, eddy-rich regions such as boundary current extensions and the Antarctic Circumpolar Current show a significant increase of 2% and 5% per decade in eddy activity, respectively. In contrast, most of the regions of observed decrease are found in the tropical oceans. Because eddies play a fundamental role in the ocean transport of heat, momentum, and carbon, our results have far-reaching implications for ocean circulation and climate, and the modelling platforms we use to study future climate change.

Labrador Sea waters export routes in an idealised model and a global high-resolution ocean model

2020 ◽  
Author(s):  
Caroline Katsman ◽  
Sotiria Georgiou ◽  
Juan-Manuel Sayol ◽  
Stefanie Ypma ◽  
Nils Brüggemann ◽  
...  
Keyword(s):  
High Resolution ◽  
Sea Water ◽  
Model Simulation ◽  
Ocean Model ◽  
Water Masses ◽  
Meridional Overturning Circulation ◽  
Global Ocean ◽  
Labrador Sea ◽  
Boundary Current ◽  
Eddy Activity

<p>The water masses exiting the Labrador Sea, and in particular the dense water mass formed by convection (i.e. Labrador Sea Water, LSW), are important components of the Atlantic Meridional Overturning Circulation (AMOC). Several studies have suggested that the eddy activity within the Labrador Sea is of high importance for the properties of the LSW and the export routes. In this study, the pathways and the associated timescales of the water masses exiting the Labrador Sea are investigated by using a Lagrangian particle tracking tool. This method is applied to two different model simulations: to an eddy- permitting idealized model able to reproduce the essential features of the Labrador Sea, and to a high-resolution global ocean model simulation under a repeated annual climatological forcing.</p><p>In both model configurations, the Lagrangian trajectories reveal that the water masses that exit the Labrador Sea have followed either a fast route within the boundary current or a slow route that involves extensive boundary current-interior exchanges. Regions characterized by enhanced eddy activity play a significant role in determining the properties and the timescales of the water masses exiting the marginal sea, as the interior-boundary current exchange is governed by eddy activity.</p><p>Analysis of the properties of the water masses along the different pathways shows that the water masses that pass through the interior experience stronger densification than those that follow the boundary current.</p><p>This study highlights the importance of the exchanges between the boundary current and the convection area in the interior in setting the properties of the water masses that leave the Labrador Sea and the associated timescales.</p>

scholarly journals A 50,000-Year History of Current Flow Yields New Climate Clues

Eos ◽  
2021 ◽  
Vol 102 ◽  
Author(s):  
Sarah Stanley
Keyword(s):  
Climate Change ◽  
High Resolution ◽  
Ocean Circulation ◽  
Current Flow ◽  
Ice Sheet ◽  
Historical Record ◽  
Boundary Current ◽  
Eastern Boundary Current ◽  
History Of ◽  
Ice Sheet Dynamics

The first high-resolution historical record of Europe’s Glacial Eastern Boundary Current sheds new light on ocean circulation, ice sheet dynamics, and climate change.

scholarly journals Spatial Analysis (Measurements at Heights of 10 m and 20 m above Ground Level) of the Concentrations of Particulate Matter (PM10, PM2.5, and PM1.0) and Gaseous Pollutants (H2S) on the University Campus: A Case Study

Atmosphere ◽  
2021 ◽  
Vol 12 (1) ◽  
pp. 62
Author(s):  
Robert Cichowicz ◽  
Maciej Dobrzański
Keyword(s):  
Spatial Distribution ◽  
Hydrogen Sulfide ◽  
Particulate Matter ◽  
Air Quality ◽  
Spatial Analysis ◽  
Ground Level ◽  
Leeward Side ◽  
High Concentration ◽  
Above Ground Level ◽  
High Concentrations

Spatial analysis of the distribution of particulate matter PM10, PM2.5, PM1.0, and hydrogen sulfide (H2S) gas pollution was performed in the area around a university library building. The reasons for the subject matter were reports related to the perceptible odor characteristic of hydrogen sulfide and a general poor assessment of air quality by employees and students. Due to the area of analysis, it was decided to perform measurements at two heights, 10 m and 20 m above ground level, using measuring equipment attached to a DJI Matrice 600 unmanned aerial vehicle (UAV). The aim of the measurements was air quality assessment and investigate the convergence of the theory of air flow around the building with the spatial distribution of air pollutants. Considerable differences of up to 63% were observed in the concentrations of pollutants measured around the building, especially between opposite sides, depending on the direction of the wind. To explain these differences, the theory of aerodynamics was applied to visualize the probable airflow in the direction of the wind. A strong convergence was observed between the aerodynamic model and the spatial distribution of pollutants. This was evidenced by the high concentrations of dust in the areas of strong turbulence at the edges of the building and on the leeward side. The accumulation of pollutants was also clearly noticeable in these locations. A high concentration of H2S was recorded around the library building on the side of the car park. On the other hand, the air turbulence around the building dispersed the gas pollution, causing the concentration of H2S to drop on the leeward side. It was confirmed that in some analyzed areas the permissible concentration of H2S was exceeded.

Sign in / Sign up

Export Citation Format

Share Document