A discussion on ocean currents and their dynamics - Time-varying currents

1971 ◽  
Vol 270 (1206) ◽  
pp. 371-390 ◽  
Keyword(s):  
Bottom Topography ◽  
Vertical Mixing ◽  
Southwest Monsoon ◽  
Dynamical Theory ◽  
Ocean Current ◽  
Nonlinear Interactions ◽  
Time Varying ◽  
Output Data ◽  
The Indian Ocean ◽  
Heat And Momentum Transfer

It would be desirable to have a dynamical theory of how ocean current patterns vary with time in response to variation in the patterns of mass, heat and momentum transfer at the surface, but severe difficulties, particularly the uncertain effects of vertical mixing, nonlinear interactions and bottom topography, oppose the development of such a theory, while its evaluation through comparison with observation is impeded by the insufficiency of both input and output data. The characteristic wavenumber components associated with different parts of the input frequency spectrum at different latitudes can, however, be expected to play a particularly important role in determining response. Several of the means by which this may happen are discussed, with some particular reference to the dynamic response of the Indian Ocean to onset of the Southwest Monsoon.

scholarly journals Beaching patterns of plastic debris along the Indian Ocean rim

2020 ◽  
Author(s):  
Mirjam van der Mheen ◽  
Erik van Sebille ◽  
Charitha Pattiaratchi
Keyword(s):  
Indian Ocean ◽  
Bay Of Bengal ◽  
Plastic Material ◽  
Monsoon Season ◽  
Southwest Monsoon ◽  
Plastic Waste ◽  
Ocean Dynamics ◽  
Global Ocean ◽  
The Indian Ocean ◽  
Southwest Monsoon Season

Abstract. A large percentage of global ocean plastic waste enters the northern hemisphere Indian Ocean (NIO). Despite this, it is unclear what happens to buoyant plastics in the NIO. Because the subtropics in the NIO is blocked by landmass, there is no subtropical gyre and no associated subtropical garbage patch in this region. We therefore hypothesise that plastics "beach" and end up on coastlines along the Indian Ocean rim. In this paper, we determine the influence of beaching plastics by applying different beaching conditions to Lagrangian particle tracking simulation results. Our results show that a large amount of plastic likely ends up on coastlines in the NIO, while some crosses the equator into the southern hemisphere Indian Ocean (SIO). In the NIO, the transport of plastics is dominated by seasonally reversing monsoonal currents, which transport plastics back and forth between the Arabian Sea and the Bay of Bengal. All buoyant plastic material in this region beaches within a few years in our simulations. Countries bordering the Bay of Bengal are particularly heavily affected by plastics beaching on coastlines. This is a result of both the large sources of plastic waste in the region, as well as ocean dynamics which concentrate plastics in the Bay of Bengal. During the intermonsoon period following the southwest monsoon season (September, October, November), plastics can cross the equator on the eastern side of the NIO basin into the SIO. Plastics that escape from the NIO into the SIO beach on eastern African coastlines and islands in the SIO or enter the subtropical SIO garbage patch.

scholarly journals Hydrography, Circulation, and Mixing at the Calypso Deep (the Deepest Mediterranean Trough) during 2006–09

2016 ◽  
Vol 46 (4) ◽  
pp. 1255-1276 ◽  
Author(s):  
H. Kontoyiannis ◽  
V. Lykousis ◽  
V. Papadopoulos ◽  
S. Stavrakakis ◽  
E. G. Anassontzis ◽  
...  
Keyword(s):  
Bottom Topography ◽  
Vertical Mixing ◽  
Average Error ◽  
Surrounding Water ◽  
Local Maxima ◽  
Vertical Diffusivity ◽  
Station Grid ◽  
Vertical Scale ◽  
Bottom Depth ◽  
Lens Center

AbstractThe mass and flow fields from June 2006 to May 2009 in the Calypso Deep (bottom depth ~5.2 km) are investigated using eddy-resolving surface-to-bottom hydrography (station grid spacing ~0.2°) and two tall moorings yielding current-meter records at depths from 700 m to near bottom. A salty warm lens (excess core salinity and temperature are ~0.01 and 0.025°C relative to the surrounding water) of Cretan Deep Water with a core at ~3000 m and a horizontal (vertical) scale of ~50 km (1.5 km) is identified in June 2006 to be locked over the trough. The lens coincides with local maxima in dissolved oxygen. In October 2006 the salinity content of the lens and of all deeper layers is increased; the oxygen maxima are shifted to the bottom layers, indicating an episodic intrusion of higher-density ventilated Adriatic water. The circulation changes from anticyclonic at all depths in June 2006 to cyclonic below ~2.5 km in October 2006, whereas after January 2007 it is cyclonic at all instrumented depths. The measured currents are weak (mean speeds < 5 cm s−1) and persistent in direction, being mostly along the bottom topography at all current-meter depths. After October 2006, the lens erodes due to salt/heat loss caused predominantly by lateral (intrusive) mixing, which works from the outside toward the lens center. The horizontal diffusivity is on the order of ~10 m2 s−1, near the center of the lens, and ~102 to 103 m2 s−1, at its periphery, with an average error ~15 times the diffusivity value. In the deepest part of the trough and in periods of predominance of vertical mixing the vertical diffusivity at 4400 m is ~(4 ± 3) × 10−3 m2 s−1.

scholarly journals Low-Frequency Currents from Deep Moorings in the Southern Bay of Bengal

2016 ◽  
Vol 46 (10) ◽  
pp. 3209-3238 ◽  
Author(s):  
H. W. Wijesekera ◽  
W. J. Teague ◽  
D. W. Wang ◽  
E. Jarosz ◽  
T. G. Jensen ◽  
...  
Keyword(s):  
Bay Of Bengal ◽  
Low Frequency ◽  
Southwest Monsoon ◽  
Naval Research ◽  
Northeast Monsoon ◽  
Intraseasonal Oscillations ◽  
The Indian Ocean ◽  
Inertial Currents ◽  
Large Eddies ◽  
Measurement Period

AbstractHigh-resolution currents and hydrographic fields were measured at six deep-water moorings in the southern Bay of Bengal (BoB) by the Naval Research Laboratory as part of an international effort focused on the dynamics of the Indian Ocean. Currents, temperature, and salinity were sampled over the upper 500 m for 20 months between December 2013 and August 2015. One of the major goals is to understand the space–time scales of the currents and physical processes that contribute to the exchange of water between the BoB and the Arabian Sea. The observations captured Southwest and Northeast Monsoon Currents, seasonally varying large eddies including a cyclonic eddy, the Sri Lanka dome (SLD), and an anticyclonic eddy southeast of the SLD. The observations further showed intraseasonal oscillations with periods of 30–70 days, near-inertial currents, and tides. Monthly averaged velocities commonly exceeded 50 cm s−1 near the surface, and extreme velocities exceeded 150 cm s−1 during the southwest monsoon. Tides were small and dominated by the M2 component with velocities of about 3 cm s−1. The average transport into the BoB over the measurement period was 2 Sv (1 Sv ≡ 106 m3 s−1) but likely exceeded 15 Sv during summer of 2014. This study suggests the water exchange away from coastal boundaries, in the interior of the BoB, may be largely influenced by the location and strength of the two eddies that modify the path of the Southwest Monsoon Current. In addition, there is a pathway below 200 m for transport of water into the BoB throughout the year.

scholarly journals On the Generation of Bottom-Trapped Internal Tides

2015 ◽  
Vol 45 (2) ◽  
pp. 526-545 ◽  
Author(s):  
Saeed Falahat ◽  
Jonas Nycander
Keyword(s):  
Energy Density ◽  
Energy Flux ◽  
General Circulation ◽  
Bottom Topography ◽  
Vertical Mixing ◽  
Internal Tides ◽  
The Arctic ◽  
Linear Wave ◽  
Tidal Constituent ◽  
Tidal Constituents

AbstractThe interaction of the barotropic tide with bottom topography when the tidal frequency ω is smaller than the Coriolis frequency f is examined. The resulting waves are called bottom-trapped internal tides. The energy density associated with these waves is computed using linear wave theory and vertical normal-mode decomposition in an ocean of finite depth. The global calculation of the modal energy density is performed for the semidiurnal M2 tidal constituent and the two major diurnal tidal constituents K1 and O1. An observationally based decay time scale of 3 days is then used to transform the energy density to energy flux in units of watts per square meter. The globally integrated energy fluxes are found to be 1.99 and 1.43 GW for the K1 and O1 tidal constituents, respectively. For the M2 tidal constituent, it is found to be 1.15 GW. The Pacific Ocean is found to be the most energetic basin for the bottom-trapped diurnal tides. Two regional estimates of the bottom-trapped energy flux are given for the Kuril Islands and the Arctic Ocean, in which the bottom-trapped waves play a role for the tidally induced vertical mixing. The results of this study can be incorporated into ocean general circulation models and coupled climate models to improve the parameterization of the vertical mixing induced by breaking of the internal tides.

scholarly journals POTENSI ENERGI ARUS LAUT SEBAGAI ENERGI TERBARUKAN DI SELAT LOMBOK BERDASARKAN DATA INSTANT WEST MOORING DEPLOYMENT 1

2017 ◽  
Vol 14 (2) ◽  
Author(s):  
Yogo Pratomo ◽  
Widodo Setiyo Pranowo ◽  
Sahat Monang Simanjuntak
Keyword(s):  
Renewable Energy ◽  
Water Depth ◽  
Current Speed ◽  
Ocean Currents ◽  
Ocean Current ◽  
The Pacific ◽  
Through Flow ◽  
The Indian Ocean ◽  
The Pacific Ocean ◽  
Harmonic Components

Selat Lombok merupakan salah satu perlintasan massa air laut dunia, yang mengalir dari Samudera Pasifik menuju ke Samudera Hindia yang disebut sebagai Arus Lintas Indonesia (ARLINDO). Hal ini terbukti dengan adanya komponen harmonik periode panjang yang di pengaruhi oleh Matahari (SA, SSA), dan dipengaruhi Bulan (MSF). Hasil rekaman mooring selama 1,5 tahun, selat ini memiliki kecepatan arus harmonik rata-rata sebesar 0,25219 m/dt di kedalaman 100 meter. Arus laut merupakan salah satu energi baru terbarukan yang dapat di manfaatkan sebagai pembangkit listrik. Arus laut diolah dengan menggunakan modul toolbox T-Tide 1,3 beta, dan menghasilkan arus harmonik dan arus non harmonik. Berdasarkan komputasi skenario pertama, dengan menggunakan turbin Helix LC 500 dan menghasilkan listrik 3,56 KW (harmonic), dan 1,86 KW (non harmonik) dengan kecepatan arus terbesar terjadi pada kedalaman 146,31 meter. Nilai kecepatan arus rata-rata terdapat pada kedalaman 178,31 meter dengan daya yang dihasilkan sebesar 92,17 W pada kondisi arus non harmonik. Kecepatan arus rata-rata pada kondisi arus harmonik terdapat pada kedalaman 162,31 meter, dengan daya yang dihasilkan sebesar 32,943 W.Kata Kunci : arus laut, energi baru terbarukan, Selat Lombok, INSTANT West Mooring.Lombok Strait is one of seawater mass outlet, flowing from the Pacific Ocean toward the Indian Ocean called as Indonesian Through Flow (ITF). It is proven by long period of harmonic components influenced by sun (SA, SSA) and moon (MSF). The result of mooring record for 1.5 years, this strait has average speed of the harmonic ocean current is 0.25219 m/s at 100 meters water depth. Ocean current is one of renewable energy that can be used for generating power electric. Ocean currents processed by using T-tide matlab toolbox 1.3 beta to identified the harmonic and non harmonic currents. Based on first scenario of the computer conversion, by using a Helix turbine LC 500 and produce an electricity energy about 3.56 KW (harmonic), and 1.86 KW (non harmonic) ocean currents, with the maximum current speed at the 146.31 meters water depth. The average of current speed average found at 178.31 meters water depth, and it produces a power of 92.17 W (non harmonic). The current speed averages from the harmonic condition is found at 162.31 meters water depth, which can produce a power about 32.943 W.Keyword : ocean currents, potential renewable energy, Lombok Strait, INSTANT West Mooring.

scholarly journals Activity of southern Indiar1 Ocean convergence zone as seen in satellite cloud data during pre-monsoon months

MAUSAM ◽  
2021 ◽  
Vol 42 (2) ◽  
pp. 145-150
Author(s):  
G. R. GUPTA ◽  
ONKARI PRASAD
Keyword(s):  
Indian Ocean ◽  
Cloud Cover ◽  
Monsoon Rainfall ◽  
Indian Monsoon ◽  
Negative Relationship ◽  
Southwest Monsoon ◽  
Convergence Zone ◽  
Indian Monsoon Rainfall ◽  
Cloud Data ◽  
The Indian Ocean

The weekly mean cloud cover data for the pre-monsoon months of April and May over the Indian Ocean between20°S to 20°N latitudes and 40°E to 100" E longitudes have been studied for three good moon- soon years (1977, 1983, 1988) and three drought years (1972,1979, 1987). It is shown that while the characteristics of weekly mean cloud cover data during pre-monsoon months are similar for all the good monsoon years, they varied from one drought year to another. The study reveals some of the interesting features of southwest monsoon. An overall negative relationship between southern Indian Ocean convergence zone (SIOCZ) and monsoon activity is indicated. While at intraseasonal scale this may only be a simultaneous association, the pre-monsoon activity of SIOCZ may possibly have long-range predictive potential to some extent, for Indian monsoon rainfall.  

scholarly journals Mechanisms of asymmetry in sea surface temperature anomalies associated with the Indian Ocean Dipole revealed by closed heat budget

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Mai Nakazato ◽  
Shoichiro Kido ◽  
Tomoki Tozuka
Keyword(s):  
Indian Ocean ◽  
Surface Temperature ◽  
Indian Ocean Dipole ◽  
Heat Budget ◽  
Vertical Mixing ◽  
Sea Surface ◽  
Subsurface Temperature ◽  
Thermocline Feedback ◽  
The Indian Ocean ◽  
Sst Anomalies

AbstractThe Indian Ocean Dipole (IOD) is an interannual climate mode of the tropical Indian Ocean. Although it is known that negative sea surface temperature (SST) anomalies in the eastern pole during the positive IOD are stronger than positive SST anomalies during the negative IOD, no consensus has been reached on the relative importance of various mechanisms that contribute to this asymmetry. Based on a closed mixed layer heat budget analysis using a regional ocean model, here we show for the first time that the vertical mixing plays an important role in causing such asymmetry in SST anomalies in addition to the contributions from the nonlinear advection and the thermocline feedback proposed by previous studies. A decomposition of the vertical mixing term indicates that nonlinearity in the anomalous vertical temperature gradient associated with subsurface temperature anomalies and anomalous vertical mixing coefficients is the main driver of such asymmetry. Such variations in subsurface temperature are induced by the anomalous southeasterly trade winds along the Indonesian coast that modulate the thermocline depth through coastal upwelling/downwelling. Thus, the thermocline feedback contributes to the SST asymmetry not through the vertical advection as previously suggested, but via the vertical mixing.

scholarly journals Assimilative capacity of the atmosphere at Lucknow with respect to air pollution

MAUSAM ◽  
2021 ◽  
Vol 50 (3) ◽  
pp. 263-268
Author(s):  
P .K. NANDANKAR
Keyword(s):  
Air Pollution ◽  
Meteorological Data ◽  
Vertical Mixing ◽  
Uttar Pradesh ◽  
Southwest Monsoon ◽  
Pollution Potential ◽  
Mixing Height ◽  
Assimilative Capacity ◽  
Diffusion Capacity ◽  
Ventilation Coefficient

The present study aim at seasonal and diurnal pollution potential at Lucknow, the capital of Uttar Pradesh. To assess the pollution potential, meteorological data for five year period (1982-86) of Lucknow have been analyzed for four season, viz.; Winter (December-February), Summer (March-May), Southwest Monsoon (June-September) and Post Monsoon (October-November). Seasonwise wind roses, stability, stability wind roses have been prepared and season wise diurnal variation of mixing height and ventilation coefficient have also been worked out. It is found that Lucknow has a better diffusion capacity in summer and poor in winter. Afternoon hours are better for vertical mixing. The winds are predominant from west to north direction in all season except in monsoon where it blows from east direction.

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