NUMERICAL SIMULATION OF SURFACE CIRCULATION FEATURES OVER THE BAY OF BENGAL USING REGIONAL OCEAN MODELING SYSTEM

2011 ◽  
pp. 117-130 ◽  
Author(s):  
SOURAV SIL ◽  
ARUN CHAKRABORTY ◽  
M. RAVICHANDRAN
Keyword(s):  
Numerical Simulation ◽  
Bay Of Bengal ◽  
Ocean Modeling ◽  
Regional Ocean Modeling System ◽  
Surface Circulation

Vertical Analysis of Mesoscale Eddies in the Northern Bay of Bengal

2021 ◽  
Author(s):  
Abhijit Shee ◽  
Saikat Pramanik ◽  
Sourav Sil ◽  
Sudeep Das
Keyword(s):  
Chlorophyll A ◽  
Bay Of Bengal ◽  
Ecological Model ◽  
Mesoscale Eddies ◽  
Anticyclonic Eddy ◽  
Ocean Modeling ◽  
Height Anomaly ◽  
Regional Ocean Modeling System ◽  
Northern Bay Of Bengal ◽  
Anticyclonic Eddies

<p>Mesoscale eddies, coherent rotating structure with typical horizontal scale of ~100 km and temporal scales of a month, play a significant role in ocean energy and mass transports. Here both mesoscale cyclonic and anticyclonic eddies moving towards south in the northern Bay of Bengal during 20<sup>th </sup>March 2017 to 20<sup>th</sup> May 2017 are observed using a high resolution (~5 km) nitrogen-based nutrient, phytoplankton, zooplankton, and detritus (NPZD) ecological model embedded with Regional Ocean Modeling System (ROMS). Spatial maps of sea surface height anomaly (SSHA) from satellite-derived Archiving Validation, and Interpretation of Satellite Oceanographic (AVISO), and model are well matched. The centers and effective radii of both kind of eddies are identified using SSHA to proceed for their three-dimensional analysis. The extreme intensities of cyclonic and anticyclonic eddy centers are observed on 8<sup>th</sup> April 2017 at 86.40°E, 18.19°N and 84.80°E, 16.52°N respectively. Both kind of eddies are vertically extended upto 800 m and have radius ~100 km at surface. At these two locations, time-depth variations of zonal and meridional currents, and other physical (temperature and salinity) and bio-physical (chlorophyll-a, phytoplankton, zooplankton, detritus nutrient, dissolved oxygen and NO<sub>3</sub> nutrient) parameters are studied particularly from 8<sup>th</sup> March 2017 to 8<sup>th</sup> May 2017. Further vertical distribution of zonal and meridional currents, and other parameters are studied along the eddy diameters at their extreme intensity. In the vertical structure of both current components, an opposite sense between cyclonic and anticyclonic eddies are clearly captured, while other variables show strong upwelling and downwelling nature around the cyclonic and anticyclonic eddy centers respectively. Abundances (scarcities) of chlorophyll-a, phytoplankton, zooplankton and detritus nutrient are observed at 50 – 150 m depth of the cyclonic (anticyclonic) eddy center. The concentration of chlorophyll-a, phytoplankton, zooplankton and detritus nutrient reach to maximum of 1 mg/m<sup>3</sup>, 0.35 mMol/m<sup>3</sup>, 0.22 mMol/m<sup>3</sup> and 0.14 mMol/m<sup>3</sup> at ~80 m depth for the cyclonic eddy, while these are absent for the anticyclonic eddy.</p>

Seasonality of Submesoscale processes in the Bay of Bengal

2020 ◽  
Author(s):  
Lanman Li ◽  
Xuhua Cheng
Keyword(s):  
High Resolution ◽  
Mixed Layer ◽  
Bay Of Bengal ◽  
Gulf Stream ◽  
Strain Field ◽  
Mesoscale Eddies ◽  
Ocean Modeling ◽  
Small Scale ◽  
Regional Ocean Modeling System ◽  
Submesoscale Processes

<p>Mesoscale eddies that known as a dominant reservoir of kinetic energy has been studied extensively for its dynamics and variation.In order to maintain energy budget equilibrium,the energy stored in mesoscale eddies is dissipated by small scale processes around centimeters.Submesoscale processes that lie between mesoscale and microscale motions effectively extract energy from mesoscale motions and transfer to smaller scales.The Bay of Bengal(the BOB) receives large fresh water from precipitation and river runoff resulting in strong salinity fronts that conducive to the generation of submesoscale processes.Using the Regional Ocean Modeling System(ROMS) data with two horizontal resolutions:a high-resolution(~1.6km) that is partially resolve submesoscale,and a low-resolution(~7km) that not resolves submesoscale,we focus on the seasonality of submesoscale processes in the Bay of Bengal.To ensure that only the submesoscale motions is considered,we choose 40km as the length to separate submesoscale from the flow field.Results show that submesocale processes is ubiquitous in the BOB,mainly trapped in the mixed layer.As resolution increasing,submesoscale motions become much stronger.Seasonality of submesoscale in the BOB is apparent and is different from the Gulf stream region  which is strongest in winter and weakest in summer.Submesoscale features in this region mostly present in fall,which the most important mechanisms is frontogenesis due to strong horizontal buoyancy flux associated with large strain.Submesoscale motions is also vigorous in winter.The proposed mechanism is that the depth of mixed layer is deep enough which contributes to the occurrence of mixed layer instability.During the whole year,mesoscale strain field is weakest in summer,which makes submesoscale weakest.</p>

scholarly journals On the long-range offshore transport of organic carbon from the Canary Upwelling System to the open North Atlantic

2017 ◽  
Vol 14 (13) ◽  
pp. 3337-3369 ◽  
Author(s):  
Elisa Lovecchio ◽  
Nicolas Gruber ◽  
Matthias Münnich ◽  
Zouhair Lachkar
Keyword(s):  
Organic Carbon ◽  
North Atlantic ◽  
Ecosystem Model ◽  
Ocean Modeling ◽  
Regional Ocean Modeling System ◽  
Net Community Production ◽  
Upwelling System ◽  
Canary Upwelling ◽  
Vertical Export ◽  
Offshore Transport

Abstract. A compilation of measurements of net community production (NCP) in the upper waters of the eastern subtropical North Atlantic had suggested net heterotrophic conditions, purportedly supported by the lateral export of organic carbon from the adjacent, highly productive Canary Upwelling System (CanUS). Here, we quantify and assess this lateral export using the Regional Ocean Modeling System (ROMS) coupled to a nutrient, phytoplankton, zooplankton, and detritus (NPZD) ecosystem model. We employ a new Atlantic telescopic grid with a strong refinement towards the northwestern African shelf to combine an eddy-resolving resolution in the CanUS with a full Atlantic basin perspective. Our climatologically forced simulation reveals an intense offshore flux of organic carbon that transports about 19 Tg C yr−1 away from the nearshore 100 km over the whole CanUS, amounting to more than a third of the NCP in this region. The offshore transport extends beyond 1500 km into the subtropical North Atlantic, adding organic carbon along the way to the upper 100 m at rates of between 8 and 34 % of the alongshore average NCP as a function of offshore distance. Although the divergence of this lateral export of organic carbon enhances local respiration, the upper 100 m layer in our model remains net autotrophic in the entire eastern subtropical North Atlantic. However, the vertical export of this organic carbon and its subsequent remineralization at depth makes the vertically integrated NCP strongly negative throughout this region, with the exception of a narrow band along the northwestern African shelf. The magnitude and efficiency of the lateral export varies substantially between the different subregions. In particular, the central coast near Cape Blanc is particularly efficient in collecting organic carbon on the shelf and subsequently transporting it offshore. In this central subregion, the offshore transport adds as much organic carbon as nearly 60 % of the local NCP to the upper 100 m, giving rise to a sharp peak of offshore respiration that extends to the middle of the gyre. Our modeled offshore transport of organic carbon is likely a lower-bound estimate due to our lack of full consideration of the contribution of dissolved organic carbon and that of particulate organic carbon stemming from the resuspension of sediments. But even in the absence of these contributions, our results emphasize the fundamental role of the lateral redistribution of the organic carbon for the maintenance of the heterotrophic activity in the open sea.

scholarly journals An estimate of the Sunda Shelf and the Strait of Malacca transports: a numerical study

2015 ◽  
Vol 12 (1) ◽  
pp. 275-313 ◽  
Author(s):  
F. Daryabor ◽  
A. A. Samah ◽  
S. H. Ooi ◽  
S. N. Chenoli
Keyword(s):  
Numerical Study ◽  
Ocean Modeling ◽  
Sea Surface Salinity ◽  
Andaman Sea ◽  
Regional Ocean Modeling System ◽  
Sunda Shelf ◽  
Surface Salinity ◽  
Volume Heat ◽  
Ocean Data Assimilation ◽  
Strait Of Malacca

Abstract. Using the Regional Ocean Modeling System (ROMS), this study aims to provide an estimate of the volume, freshwater, heat, and salt transports through the Sunda Shelf and the Strait of Malacca in the southern region of the South China Sea (SSCS). The modeling system is configured with two one-way nested domains representing parent and child with resolutions of 1/2 and 1/12°, respectively. The simulated currents, sea surface salinity, temperature and various transports (e.g., volume, heat, etc) agree well with the observed values as well as those estimated from the Simple Ocean Data Assimilation (SODA) re-analysis product. The ROMS estimated seasonal and mean annual transports are in accord with those calculated from SODA and those of limited observations. The ROMS estimates of mean annual volume, freshwater, heat and salt transports through the Sunda Shelf into the Java Sea are 0.32Sv (1 Sv = 106 m3 s−1), 0.023 Sv, 0.032 PW (1 PW = 1015 j s−1), and 0.010 × 109 kg s−1 respectively. The corresponding ROMS estimates for mean annual transports through the Strait of Malacca into Andaman Sea are 0.14, 0.009 Sv, 0.014 PW, and 0.0043 × 109 kg s−1 respectively. The relative percentages of mean annual transports computed individually from those of volume, heat, salinity, and freshwater between the Strait of Malacca and the Sunda Shelf range from 39 to 43.8%. This reflects that the Strait of Malacca plays an equally significant role in the annual transports from the SSCS into the Andaman Sea.

scholarly journals Dynamics of the Block Island Sound Estuarine Plume

2016 ◽  
Vol 46 (5) ◽  
pp. 1633-1656 ◽  
Author(s):  
Qianqian Liu ◽  
Lewis M. Rothstein ◽  
Yiyong Luo
Keyword(s):  
Seasonal Variation ◽  
River Discharge ◽  
Long Island ◽  
Long Island Sound ◽  
Ocean Modeling ◽  
Surface Heating ◽  
Buoyant Plume ◽  
Regional Ocean Modeling System ◽  
Block Island ◽  
Island Sound

AbstractBuoyant discharge of freshwater from Long Island Sound (LIS) forms a seasonal buoyant plume outside Block Island Sound (BIS) between the coast of Long Island and the denser shelf waters. The plume’s seasonal variability and its response to tides, winds, and surface heating are investigated through a series of process-oriented experiments using the Regional Ocean Modeling System (ROMS). Results show the importance of river discharge, wind directions, and surface heating in the seasonal variation of the BIS buoyant plume. In winter and spring, the plume is intermediate with a large surface offshore extension detached from the bottom. From winter to spring, the river discharge increases; meanwhile, upwelling-favorable winds keep dominating. They compete with the increase of surface heating and generate a broader buoyant plume in spring than in winter. In summer, the plume is bottom advected with most of its width in contact with the bottom and is featured with the steepest isopycnals and narrowest plume, which is driven by a combination of strong insolation, weak buoyant discharge from LIS, and feeble winds. In fall, although the river discharge is comparable to that in winter, the upwelling-favorable wind is relatively weaker, corresponding to a narrower intermediate plume.

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