Ship Motion Instabilities in Coastal Regions

2009 ◽  
Author(s):  
Ray-Qing Lin ◽  
Weijia Kuang
Keyword(s):  
Ocean Circulation ◽  
Wind Waves ◽  
Bottom Topography ◽  
Circulation Model ◽  
Wave Interaction ◽  
Deep Ocean ◽  
Wave Model ◽  
Ship Motion ◽  
Ship Motions ◽  
Coastal Regions

Ship motion instabilities occur much more frequently in coastal regions than in the deep ocean because both nonlinear wave-wave interactions and wave-current interactions increase significantly as the water depth decreases. This is particularly significant in the coastal regions connecting to the open ocean, since the wave resonant interactions change from the four-equivalent-wave interaction in deep water to the interactions of three local wind waves with a long wave (e.g. swell, edge waves, bottom topography waves, etc.) in shallow water [1, 2], resulting in rapid growth of the incoming long waves. In this study, we use our DiSSEL (Digital, Self-consistent, Ship Experimental Laboratory) Ship Motion Model [3,4,5,6] coupled with our Coastal Wave Model [1,2,11] and an Ocean Circulation Model [7] to simulate strongly nonlinear ship motions in coastal regions, focusing on the ship motion instabilities arising from ship body-surface wave-current interactions.

scholarly journals A coarse resolution North Atlantic ocean circulation model: an intercomparison study with a paleoceanographic example

1996 ◽  
Vol 14 (2) ◽  
pp. 246-257 ◽  
Author(s):  
Dan Seidov ◽  
Ralf Prien
Keyword(s):  
Ocean Circulation ◽  
North Atlantic ◽  
Numerical Models ◽  
Bottom Topography ◽  
Circulation Model ◽  
Deep Ocean ◽  
Return Flow ◽  
Freshwater Flux ◽  
Surface Boundary

Abstract. Paleoreconstructions suggest that during the Last Glacial Maximum (LGM) the North Atlantic circulation was noticeably different from its present state. However, the glacial salt conveyor belt is believed to be similar to the present-day's conveyor, albeit weaker and shallower because of an increased freshwater flux in high-latitudes. We present here the investigation of the conveyor operation based on ocean circulation modelling using two numerical models in parallel. The GFDL primitive equation model and a planetary geostrophic model are employed to address the problem of the paleocirculation modelling in cases of uncertain and sparse data comprising the glacial surface boundary conditions. The role of different simplifications that may be used in the ocean climate studies, including the role of grid resolution, bottom topography, coast-line, etc., versus glacial-interglacial changes of the ocean surface climatology is considered. The LGM reverse conveyor gyre appeared to be the most noticeable feature of the glacial-to-interglacial alteration of the ocean circulation. The reversed upper-ocean conveyor, weaker and subducting 'normal' conveyor in the intermediate depths, and the change of the deep-ocean return flow route are robust signatures of the glacial North Atlantic climate. The results are found to be 'model-independent' and fairly insensitive to all factors other than the onset of the glacial surface conditions.

On the impact of sea ice in a global ocean circulation model

1997 ◽  
Vol 25 ◽  
pp. 111-115 ◽  
Author(s):  
Achim Stössel
Keyword(s):  
Southern Ocean ◽  
Sea Ice ◽  
Ocean Circulation ◽  
General Circulation ◽  
Thermohaline Circulation ◽  
Circulation Model ◽  
Deep Ocean ◽  
Global Ocean ◽  
Convective Activity ◽  
The Impact

This paper investigates the long-term impact of sea ice on global climate using a global sea-ice–ocean general circulation model (OGCM). The sea-ice component involves state-of-the-art dynamics; the ocean component consists of a 3.5° × 3.5° × 11 layer primitive-equation model. Depending on the physical description of sea ice, significant changes are detected in the convective activity, in the hydrographic properties and in the thermohaline circulation of the ocean model. Most of these changes originate in the Southern Ocean, emphasizing the crucial role of sea ice in this marginally stably stratified region of the world's oceans. Specifically, if the effect of brine release is neglected, the deep layers of the Southern Ocean warm up considerably; this is associated with a weakening of the Southern Hemisphere overturning cell. The removal of the commonly used “salinity enhancement” leads to a similar effect. The deep-ocean salinity is almost unaffected in both experiments. Introducing explicit new-ice thickness growth in partially ice-covered gridcells leads to a substantial increase in convective activity, especially in the Southern Ocean, with a concomitant significant cooling and salinification of the deep ocean. Possible mechanisms for the resulting interactions between sea-ice processes and deep-ocean characteristics are suggested.

Evaluating Effects of Observational Data Assimilation in General Ocean Circulation Model by Ensemble Kalman Filtering: Numerical Experiments with Synthetic Observations

2021 ◽  
pp. 50-66
Author(s):  
V. N. Stepanov ◽  
◽  
Yu. D. Resnyanskii ◽  
B. S. Strukov ◽  
A. A. Zelen’ko ◽  
...  
Keyword(s):  
Data Assimilation ◽  
Observational Data ◽  
Ocean Circulation ◽  
Numerical Experiments ◽  
Turbulent Viscosity ◽  
Bottom Topography ◽  
Synthetic Data ◽  
Circulation Model ◽  
Ocean Model ◽  
Global Ocean

The quality of simulation of model fields is analyzed depending on the assimilation of various types of data using the PDAF software product assimilating synthetic data into the NEMO global ocean model. Several numerical experiments are performed to simulate the ocean–sea ice system. Initially, free model was run with different values of the coefficients of horizontal turbulent viscosity and diffusion, but with the same atmospheric forcing. The model output obtained with higher values of these coefficients was used to determine the first guess fields in subsequent experiments with data assimilation, while the model results with lower values of the coefficients were assumed to be true states, and a part of these results was used as synthetic observations. The results are analyzed that are assimilation of various types of observational data using the Kalman filter included through the PDAF to the NEMO model with real bottom topography. It is shown that a degree of improving model fields in the process of data assimilation is highly dependent on the structure of data at the input of the assimilation procedure.

The source-sink flow in a rotating system and its oceanic analogy

1971 ◽  
Vol 45 (3) ◽  
pp. 441-464 ◽  
Author(s):  
Han-Hsiung Kuo ◽  
George Veronis
Keyword(s):  
Ocean Circulation ◽  
Bottom Topography ◽  
Circulation Model ◽  
Circulation Pattern ◽  
Theoretical Models ◽  
Outer Wall ◽  
Western Boundary ◽  
Shaped Container ◽  
Laboratory Analogue ◽  
Source Sink

Laboratory analogues of theoretical models of wind-driven ocean circulation are based on ideas presented by Stommel (1957). A particularly simple demonstration of the applicability of these ideas is contained in a paper by Stommel, Arons & Faller (1958). The present work develops the source-sink laboratory analogue of ocean circulation models to a point where chosen parametric values allow one to simulate the theoretical models of Stommel (1948) and Munk (1950) exactly. The investigation of the flow in a rotating cylinder generated by a source of fluid near the outer wall leads to a detailed description of the roles of the various boundary layers which occur. This knowledge is used to analyse the more complex source-sink flow in a pie-shaped basin. The laboratory analogue to the Stommel circulation model is analyzed in detail. It is shown that the change in the flow pattern brought about by a radial variation of the position of the eastern boundary in the pie-shaped basin is confined to the interior flow and the boundary layer is largely unaffected. When the bottom of the pie-shaped container slopes, the circulation pattern is changed significantly. For the particular case treated, the depth of the basin along the western boundary is unchanged and the maximum depth occurs at the southeast corner. The circulation generated by a source introduced at the apex of the pie has a gyre whose centre is shifted more toward the southwest corner than the corresponding centre of the gyre for a flat-bottomed basin. Two experiments are reported showing that the western boundary may separate because of the effect of bottom topography or because of the pressure of a cyclonic and an anti-cyclonic gyre generated by suitably placed sources and sinks.

scholarly journals The impact of wave physics in the CMEMS-IBI ocean system Part A: Wave forcing validation

2019 ◽  
Author(s):  
Romain Rainaud ◽  
Lotfi Aouf ◽  
Alice Dalphinet ◽  
Marcos Garcia Sotillo ◽  
Enrique Alvarez-Fanjul ◽  
...  
Keyword(s):  
Ocean Circulation ◽  
Wave Spectrum ◽  
Circulation Model ◽  
Wave Model ◽  
Heat Fluxes ◽  
Wave System ◽  
Peak Period ◽  
Wave Forecast ◽  
High Frequency Waves ◽  
The Impact

Abstract. The Iberian Biscay Ireland (IBI) wave system has the challenge to improve wave forecast and the coupling with ocean circulation model dedicated to western european coast. The momentum and heat fluxes at the sea surface are strongly controlled by the waves and there is a need of using accurate sea state from wave model. This work describes the more recent version of the IBI wave system and highlight the performance of system in comparison with satellite altimeters and buoys wave data. The validation process has been performed for 1-year run of the wave model MFWAM with boundary conditions provided by the global wave system. The results show on the one hand a slightly improvement on significant wave height and peak period, and on the other hand a better surface stress for high wind conditions. This latter is a consequence of using a tail wave spectrum shaped as the Philipps wave spectrum for high frequency waves.

scholarly journals Modeling ocean circulation and biogeochemical variability in the Gulf of Mexico

2013 ◽  
Vol 10 (11) ◽  
pp. 7219-7234 ◽  
Author(s):  
Z. Xue ◽  
R. He ◽  
K. Fennel ◽  
W.-J. Cai ◽  
S. Lohrenz ◽  
...  
Keyword(s):  
Gulf Of Mexico ◽  
Ocean Circulation ◽  
Function Analysis ◽  
Inorganic Nitrogen ◽  
Circulation Model ◽  
Deep Ocean ◽  
Global Ocean ◽  
Open Boundary ◽  
Biogeochemical Model ◽  
Open Boundary Conditions

Abstract. A three-dimensional coupled physical-biogeochemical model is applied to simulate and examine temporal and spatial variability of circulation and biogeochemical cycling in the Gulf of Mexico (GoM). The model is driven by realistic atmospheric forcing, open boundary conditions from a data assimilative global ocean circulation model, and observed freshwater and terrestrial nitrogen input from major rivers. A 7 yr model hindcast (2004–2010) was performed, and validated against satellite observed sea surface height, surface chlorophyll, and in situ observations including coastal sea level, ocean temperature, salinity, and dissolved inorganic nitrogen (DIN) concentration. The model hindcast revealed clear seasonality in DIN, phytoplankton and zooplankton distributions in the GoM. An empirical orthogonal function analysis indicated a phase-locked pattern among DIN, phytoplankton and zooplankton concentrations. The GoM shelf nitrogen budget was also quantified, revealing that on an annual basis the DIN input is largely balanced by the removal through denitrification (an equivalent of ~ 80% of DIN input) and offshore exports to the deep ocean (an equivalent of ~ 17% of DIN input).

scholarly journals Dynamically and Observationally Constrained Estimates of Water-Mass Distributions and Ages in the Global Ocean

2011 ◽  
Vol 41 (12) ◽  
pp. 2381-2401 ◽  
Author(s):  
Tim DeVries ◽  
François Primeau
Keyword(s):  
Southern Ocean ◽  
Ocean Circulation ◽  
North Pacific ◽  
Circulation Model ◽  
Deep Ocean ◽  
Water Masses ◽  
Sea Surface ◽  
Global Ocean ◽  
Deep Waters ◽  
The Mean

Abstract A data-constrained ocean circulation model is used to characterize the distribution of water masses and their ages in the global ocean. The model is constrained by the time-averaged temperature, salinity, and radiocarbon distributions in the ocean, as well as independent estimates of the mean sea surface height and sea surface heat and freshwater fluxes. The data-constrained model suggests that the interior ocean is ventilated primarily by water masses forming in the Southern Ocean. Southern Ocean waters, including those waters forming in the Antarctic and subantarctic regions, make up about 55% of the interior ocean volume and an even larger percentage of the deep-ocean volume. In the deep North Pacific, the ratio of Southern Ocean to North Atlantic waters is almost 3:1. Approximately 65% of interior ocean waters make first contact with the atmosphere in the Southern Ocean, further emphasizing the central role played by the Southern Ocean in the regulation of the earth’s climate. Results of the age analysis suggest that the mean ventilation age of deep waters is greater than 1000 yr throughout most of the Indian and Pacific Oceans, reaching a maximum of about 1400–1500 yr in the middepth North Pacific. The mean time for deep waters to be reexposed at the surface also reaches a maximum of about 1400–1500 yr in the deep North Pacific. Together these findings suggest that the deep North Pacific can be characterized as a “holding pen” of stagnant and recirculating waters.

scholarly journals Modeling ocean circulation and biogeochemical variability in the Gulf of Mexico

2013 ◽  
Vol 10 (5) ◽  
pp. 7785-7830 ◽  
Author(s):  
Z. Xue ◽  
R. He ◽  
K. Fennel ◽  
W.-J. Cai ◽  
S. Lohrenz ◽  
...  
Keyword(s):  
Gulf Of Mexico ◽  
Ocean Circulation ◽  
Function Analysis ◽  
Circulation Model ◽  
Deep Ocean ◽  
Global Ocean ◽  
Open Boundary ◽  
Biogeochemical Model ◽  
Open Boundary Conditions ◽  
Nutrient Input

Abstract. A three-dimensional coupled physical-biogeochemical model is applied to simulate and examine temporal and spatial variability of circulation and biogeochemical cycling in the Gulf of Mexico (GoM). The model is driven by realistic atmospheric forcing, open boundary conditions from a data assimilative global ocean circulation model, and observed freshwater and terrestrial nutrient input from major rivers. A 7 yr model hindcast (2004–2010) was performed, and validated against satellite observed sea surface height, surface chlorophyll, and in-situ observations including coastal sea-level, ocean temperature, salinity, and nutrient concentration. The model hindcast revealed clear seasonality in nutrient, phytoplankton and zooplankton distributions in the GoM. An Empirical Orthogonal Function analysis indicated a phase-locked pattern among nutrient, phytoplankton and zooplankton concentrations. The GoM shelf nutrient budget was also quantified, revealing that on an annual basis ~80% of nutrient input was denitrified on the shelf and ~17% was exported to the deep ocean.

scholarly journals A salty deep ocean as a prerequisite for glacial termination

2021 ◽  
Vol 14 (12) ◽  
pp. 930-936
Author(s):  
Gregor Knorr ◽  
Stephen Barker ◽  
Xu Zhang ◽  
Gerrit Lohmann ◽  
Xun Gong ◽  
...  
Keyword(s):  
Ocean Circulation ◽  
General Circulation ◽  
Late Quaternary ◽  
Temperature Response ◽  
Circulation Model ◽  
Deep Ocean ◽  
Ocean General Circulation Model ◽  
Glacial Maximum ◽  
Meridional Overturning Circulation ◽  
Salinity Stratification

AbstractDeglacial transitions of the middle to late Pleistocene (terminations) are linked to gradual changes in insolation accompanied by abrupt shifts in ocean circulation. However, the reason these deglacial abrupt events are so special compared with their sub-glacial-maximum analogues, in particular with respect to the exaggerated warming observed across Antarctica, remains unclear. Here we show that an increase in the relative importance of salt versus temperature stratification in the glacial deep South Atlantic decreases the potential cooling effect of waters that may be upwelled in response to abrupt perturbations in ocean circulation, as compared with sub-glacial-maximum conditions. Using a comprehensive coupled atmosphere–ocean general circulation model, we then demonstrate that an increase in deep-ocean salinity stratification stabilizes relatively warm waters in the glacial deep ocean, which amplifies the high southern latitude surface ocean temperature response to an abrupt weakening of the Atlantic meridional overturning circulation during deglaciation. The mechanism can produce a doubling in the net rate of warming across Antarctica on a multicentennial timescale when starting from full glacial conditions (as compared with interglacial or subglacial conditions) and therefore helps to explain the large magnitude and rapidity of glacial terminations during the late Quaternary.

Wave-currents interaction in the Black Sea: new modelling approach for next generation of operational forecasting system.

2021 ◽  
Author(s):  
Salvatore Causio ◽  
Piero Lionello ◽  
Stefania Angela Ciliberti ◽  
Giovanni Coppini
Keyword(s):  
Black Sea ◽  
Ocean Circulation ◽  
Wave Spectrum ◽  
Circulation Model ◽  
Wave Model ◽  
Bias Reduction ◽  
Hydrodynamical Model ◽  
The Black Sea ◽  
Surface Boundary ◽  
The Impact

<p>This study analyzes wave-currents interactions in the Black Sea basin focusing on deep water processes by using a coupled two-ways off-line numerical system, based on the ocean circulation model NEMO v4.0 and the third-generation wave model WaveWatchIII v5.16. The coupling between wave and hydrodynamical models is carried out at hourly frequency. The physical processes taken in consideration are: Stokes-Coriolis force, sea-state dependent momentum flux, wave induced vertical mixing, Doppler shift, and the stability parameter for the computation of effective wind speed. </p><p>The hydrodynamical model is implemented over the Black Sea at the horizontal resolution of about 3km and 31 vertical levels, with closed boundary at the Bosporus Strait. The impact of the Bosporus Strait on the Black Sea dynamics is modeled using a surface boundary condition, taking into account the barotropic transport, which balances the freshwater fluxes on monthly basis (Stanev and Beckers, 1999; Peneva et al., 2001; Ciliberti et al., 2021). Additionally, Mediterranean waters inflow is represented by applying a local damping to high resolution temperature and salinity profiles (Aydogdu et al., 2018) at the Bosporus exit.</p><p>The wave model adopts the WW3 implementation of the WAM Cycle4 model physics, with Ultimate Quickest propagation scheme and GSE alleviation, over the same spatial grid as the hydrodynamical model Wind input and dissipation are based on Ardhuin et al. (2010), wave-wave interactions are based on Discrete Interaction Approximation. The wave spectrum is discretized using 24 directional sectors, and 30 frequencies, with 10% increment starting from 0.055Hz. Validation and statistical analysis of the results have been carried out to compare coupled and uncoupled runs, aiming to identify the model set-up to upgrade in the future the near real time operational system.</p><p>The evaluation of the coupling impact on significant wave height and temperature shows BIAS reduction, and even slight improvement of RMSE.</p>

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