scholarly journals On the Patterns of Wind-Power Input to the Ocean Circulation

2011 ◽  
Vol 41 (12) ◽  
pp. 2328-2342 ◽  
Author(s):  
Fabien Roquet ◽  
Carl Wunsch ◽  
Gurvan Madec
Keyword(s):  
Wind Power ◽  
Ocean Circulation ◽  
General Circulation ◽  
Average Energy ◽  
Power Input ◽  
Ekman Pumping ◽  
Ekman Theory ◽  
Global Mean Sea Level ◽  
Circumpolar Current ◽  
Work Done

Abstract Pathways of wind-power input into the ocean general circulation are analyzed using Ekman theory. Direct rates of wind work can be calculated through the wind stress acting on the surface geostrophic flow. However, because that energy is transported laterally in the Ekman layer, the injection into the geostrophic interior is actually controlled by Ekman pumping, with a pattern determined by the wind curl rather than the wind itself. Regions of power injection into the geostrophic interior are thus generally shifted poleward compared to regions of direct wind-power input, most notably in the Southern Ocean, where on average energy enters the interior 10° south of the Antarctic Circumpolar Current core. An interpretation of the wind-power input to the interior is proposed, expressed as a downward flux of pressure work. This energy flux is a measure of the work done by the Ekman pumping against the surface elevation pressure, helping to maintain the observed anomaly of sea surface height relative to the global-mean sea level.

Variability in Southern Hemisphere Ocean Circulation from the 1980s to the 2000s

2013 ◽  
Vol 43 (9) ◽  
pp. 1981-2007 ◽  
Author(s):  
K. Katsumata ◽  
S. Masuda
Keyword(s):  
Southern Hemisphere ◽  
Ocean Circulation ◽  
General Circulation ◽  
Antarctic Circumpolar Current ◽  
General Circulation Models ◽  
Polar Front ◽  
Inverse Model ◽  
Meridional Overturning Circulation ◽  
Steady Increase ◽  
Circumpolar Current

Abstract Interannual-to-decadal variability of ocean circulation in the Southern Hemisphere was examined using data from the 1980s to the 2000s in a box inverse model to estimate transport across hydrographic sections and three ocean general circulation models (OGCMs). The westerly wind stress over the OGCM Southern Ocean showed a steady increase of 5%–8% decade−1. The meridional overturning circulation was quantified by the transport across 30°S. The OGCMs suggested a slight strengthening [from 0.2 ± 1.0 to 0.8 ± 1.3 Sv decade−1 (1 Sv ≡ 106 m3 s−1)] of the upper meridional cell (Deacon cell) and two OGCMs showed a weakening (−0.8 ± 0.6 and −1.0 ± 0.3 Sv decade−1) of the lower meridional [Antarctic Bottom Water (AABW)] cell, partly explained by contraction of the AABW volume. The box inverse estimates did not contradict these two findings. For Antarctic Circumpolar Current transport, quantified by zonal transport across four key sections, the box inverse model estimated a decrease of 5–21 Sv. Decomposition of the decrease into baroclinic transport by the Subantarctic and Polar Fronts, barotropic transport, and others shows that the decrease is mostly due to barotropic transport and transport carried by the flow north of the Subantarctic Front and south of the Polar Front. In the OGCMs, the variability of transport across key sections is often correlated with transport carried by a flow south of the Polar Front and with the southern annular mode index. In all models, then, the transport of the Antarctic Circumpolar Current, defined as the transport carried by the fronts, has not decreased significantly over the study period.

scholarly journals Rate of Work Done by Atmospheric Pressure on the Ocean General Circulation and Tides

2009 ◽  
Vol 39 (2) ◽  
pp. 458-464 ◽  
Author(s):  
Rui M. Ponte
Keyword(s):  
Atmospheric Pressure ◽  
General Circulation ◽  
Power Input ◽  
Time Variable ◽  
Ocean Tide ◽  
Mean Values ◽  
Low Latitudes ◽  
Order Of Magnitude ◽  
Wind Input ◽  
Work Done

Abstract Quantitative analysis of the energetics of the ocean is crucial for understanding its circulation and mixing. The power input by fluctuations in atmospheric pressure pa resulting from the S1 and S2 air tides and the stochastic continuum is analyzed here, with a focus on globally integrated, time-mean values. Results are based on available 1° × 1° near-global pa and sea level fields and are intended as mainly order-of-magnitude estimates. The rate of work done on the radiational and gravitational components of the S2 ocean tide is estimated at 14 and −60 GW, respectively, mostly occurring at low latitudes. The net extraction of energy at a rate of −46 GW is about 10% of available estimates of the work rates by gravity on the S2 tide. For the mainly radiational S1 tide, the power input by pa is much weaker (0.25 GW). Based on daily mean quantities, the stochastic pa continuum contributes ∼3 GW to the nontidal circulation, with substantial power input being associated with the pa-driven dynamic response in the Southern Ocean at submonthly time scales. Missing contributions from nontidal variability at the shortest periods (≤ 2 days) may be substantial, but the rate of work done by pa on the general circulation is likely to remain < 1% of the available wind input estimates. The importance of pa effects when considering local, time-variable energetics remains a possibility, however.

scholarly journals The Ocean General Circulation near 1000-m Depth

2014 ◽  
Vol 44 (1) ◽  
pp. 384-409 ◽  
Author(s):  
Michel Ollitrault ◽  
Alain Colin de Verdière
Keyword(s):  
Ocean Circulation ◽  
General Circulation ◽  
Neumann Boundary ◽  
Reference Level ◽  
Western Boundary ◽  
Boundary Currents ◽  
Zonal Jets ◽  
The Mean ◽  
Circumpolar Current ◽  
The Antarctic

Abstract The mean ocean circulation near 1000-m depth is estimated with 100-km resolution from the Argo float displacements collected before 1 January 2010. After a thorough validation, the 400 000 or so displacements found in the 950–1150 dbar layer and with parking times between 4 and 17 days allow the currents to be mapped at intermediate depths with unprecedented details. The Antarctic Circumpolar Current (ACC) is the most prominent feature, but western boundary currents (and their recirculations) and alternating zonal jets in the tropical Atlantic and Pacific are also well defined. Eddy kinetic energy (EKE) gives the mesoscale variability (on the order of 10 cm2 s−2 in the interior), which is compared to the surface geostrophic altimetric EKE showing e-folding depths greater than 700 m in the ACC and northern subpolar regions. Assuming planetary geostrophy, the geopotential height of the 1000-dbar isobar is estimated to obtain an absolute and deep reference level worldwide. This is done by solving numerically the Poisson equation that results from taking the divergence of the geostrophic equations on the sphere, assuming Neumann boundary conditions.

scholarly journals Sensitivity study of the generation of mesoscale eddies in a numerical model of Hawaii islands

Ocean Science ◽  
2011 ◽  
Vol 7 (3) ◽  
pp. 277-291 ◽  
Author(s):  
M. Kersalé ◽  
A. M. Doglioli ◽  
A. A. Petrenko
Keyword(s):  
Ocean Circulation ◽  
General Circulation ◽  
Cumulative Effect ◽  
Mesoscale Eddies ◽  
Sensitivity Study ◽  
Ocean Model ◽  
Ekman Pumping ◽  
Oceanic Circulation ◽  
Wind Stress Curl ◽  
Trade Winds

Abstract. The oceanic circulation around the Hawaiian archipelago is characterized by a complex circulation and the presence of mesoscale eddies west of the islands. These eddies typically develop and persist for weeks to several months in the area during persistent trade winds conditions. A series of numerical simulations on the Hawaiian region has been done in order to examine the relative importance of wind, inflow current and topographic forcing on the general circulation and the generation of eddies. Moreover, numerical cyclonic eddies are compared with the one observed during the cruise E-FLUX (Dickey et al., 2008). Our study demonstrates the need for all three forcings (wind, inflow current and topography) to reproduce the known oceanic circulation. In particular, the cumulative effect plays a key role on the generation of mesoscale eddies. The wind-stress-curl, via the Ekman pumping mechanism, has also been identified as an important mechanism upon the strength of the upwelling in the lee of the Big Island of Hawaii. In order to find the best setup of a regional ocean model, we compare more precisely numerical results obtained using two different wind databases: COADS and QuikSCAT. The main features of the ocean circulation in the area are well reproduced by our model forced by both COADS and QuickSCAT climatologies. Nevertheless, significant differences appear in the levels of kinetic energy and vorticity. The wind-forcing spatial resolution clearly affects the way in which the wind momentum feeds the mesoscale phenomena. The higher the resolution, the more realistic the ocean circulation. In particular, the simulation forced by QuikSCAT wind data reproduces well the observed energetic mesoscale structures and their hydrological characteristics and behaviors.

scholarly journals Wind-Generated Power Input to the Deep Ocean: An Estimate Using a 1/10° General Circulation Model

2007 ◽  
Vol 37 (3) ◽  
pp. 657-672 ◽  
Author(s):  
Jin-Song von Storch ◽  
Hideharu Sasaki ◽  
Jochem Marotzke
Keyword(s):  
General Circulation Model ◽  
Ocean Circulation ◽  
General Circulation ◽  
Circulation Model ◽  
Deep Ocean ◽  
Power Input ◽  
Ocean General Circulation Model ◽  
Sea Surface ◽  
Total Power ◽  
The Earth

Abstract Recent studies on the wind-generated power input to the geostrophic and nongeostrophic ocean circulation components have used expressions derived from Ekman dynamics. The present work extends and unifies previous studies by deriving an expression from the kinetic energy budget of the upper layer based on the primitive equations. Using this expression, the wind-generated power available to the deep ocean is estimated from an integration with the 1/10° ocean general circulation model of the Earth Simulator Center. The result shows that the total power generated by the wind at the sea surface is about 3.8 TW. About 30% of this power (1.1 TW) is passed through a surface layer of about 110-m thickness to the ocean beneath. Approximating the wind-generated power to the deep ocean using Ekman dynamics produces two large errors of opposite signs, which cancel each other to a large extent.

scholarly journals On the Wind Power Input to the Ocean General Circulation

2012 ◽  
Vol 42 (8) ◽  
pp. 1357-1365 ◽  
Author(s):  
Xiaoming Zhai ◽  
Helen L. Johnson ◽  
David P. Marshall ◽  
Carl Wunsch
Keyword(s):  
Wind Power ◽  
Gulf Stream ◽  
General Circulation ◽  
Kuroshio Extension ◽  
Storm Track ◽  
Deep Ocean ◽  
Power Input ◽  
Surface Velocity ◽  
Ocean General Circulation

Abstract The wind power input to the ocean general circulation is usually calculated from the time-averaged wind products. Here, this wind power input is reexamined using available observations, focusing on the role of the synoptically varying wind. Power input to the ocean general circulation is found to increase by over 70% when 6-hourly winds are used instead of monthly winds. Much of the increase occurs in the storm-track regions of the Southern Ocean, Gulf Stream, and Kuroshio Extension. This result holds irrespective of whether the ocean surface velocity is accounted for in the wind stress calculation. Depending on the fate of the high-frequency wind power input, the power input to the ocean general circulation relevant to deep-ocean mixing may be less than previously thought. This study emphasizes the difficulty of choosing appropriate forcing for ocean-only models.

ON EVALUATION OF THE ROLE OF THERMAL AND WIND FACTORS FOR A PHYSICAL MODEL OF THE WORLD OCEAN GENERAL CIRCULATION SYSTEM

2019 ◽  
Vol 47 (3) ◽  
pp. 80-91
Author(s):  
V. G. Neiman
Keyword(s):  
Physical Model ◽  
Ocean Circulation ◽  
General Circulation ◽  
World Ocean ◽  
Circulation System ◽  
The Public ◽  
The World ◽  
Almost All ◽  
Conceptual Foundations

The main content of the work consists of certain systematization and addition of longexisting, but eventually deformed and partly lost qualitative ideas about the role of thermal and wind factors that determine the physical mechanism of the World Ocean’s General Circulation System (OGCS). It is noted that the conceptual foundations of the theory of the OGCS in one form or another are contained in the works of many well-known hydrophysicists of the last century, but the aggregate, logically coherent description of the key factors determining the physical model of the OGCS in the public literature is not so easy to find. An attempt is made to clarify and concretize some general ideas about the two key blocks that form the basis of an adequate physical model of the system of oceanic water masses motion in a climatic scale. Attention is drawn to the fact that when analyzing the OGCS it is necessary to take into account not only immediate but also indirect effects of thermal and wind factors on the ocean surface. In conclusion, it is noted that, in the end, by the uneven flow of heat to the surface of the ocean can be explained the nature of both external and almost all internal factors, in one way or another contributing to the excitation of the general, or climatic, ocean circulation.

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.

scholarly journals A Time History of Pre- and Post-Bomb Radiocarbon in the Barents Sea Derived from Arcto-Norwegian Cod Otoliths

Radiocarbon ◽  
2001 ◽  
Vol 43 (2B) ◽  
pp. 843-855 ◽  
Author(s):  
John M Kalish ◽  
Reidar Nydal ◽  
Kjell H Nedreaas ◽  
George S Burr ◽  
Gro L Eine
Keyword(s):  
Time Series ◽  
Ocean Circulation ◽  
General Circulation ◽  
Barents Sea ◽  
Dissolved Inorganic Carbon ◽  
Time History ◽  
General Circulation Models ◽  
Fine Tuning ◽  
Birth Date ◽  
The Barents Sea

Radiocarbon measured in seawater dissolved inorganic carbon (DIC) can be used to investigate ocean circulation, atmosphere/ocean carbon flux, and provide powerful constraints for the fine-tuning of general circulation models (GCMs). Time series of 14C in seawater are derived most frequently from annual bands of hermatypic corals. However, this proxy is unavailable in temperate and polar oceans. Fish otoliths, calcium carbonate auditory, and gravity receptors in the membranous labyrinths of teleost fishes, can act as proxies for 14C in most oceans and at most depths. Arcto-Norwegian cod otoliths are suited to this application due to the well-defined distribution of this species in the Barents Sea, the ability to determine ages of individual Arcto-Norwegian cod with a high level of accuracy, and the availability of archived otoliths collected for fisheries research over the past 60 years. Using measurements of 14C derived from Arcto-Norwegian cod otoliths, we present the first pre- and post-bomb time series (1919–1992) of 14C from polar seas and consider the significance of these data in relation to ocean circulation and atmosphere/ocean flux of 14C. The data provide evidence for a minor Suess effect of only 0.2‰ per year between 1919 and 1950. Bomb 14C was evident in the Barents Sea as early as 1957 and the highest 14C value was measured in an otolith core from a cod with a birth date of 1967. The otolith 14C data display key features common to records of 14C obtained from a Georges Bank mollusc and corals from the tropical and subtropical North Atlantic.

The geography of numerical mixing in a suite of global ocean models

2021 ◽  
Author(s):  
Ryan Holmes ◽  
Jan Zika ◽  
Stephen Griffies ◽  
Andrew Hogg ◽  
Andrew Kiss ◽  
...  
Keyword(s):  
Ocean Circulation ◽  
General Circulation ◽  
Horizontal Resolution ◽  
Global Ocean ◽  
Vertical Diffusivity ◽  
Mixing Parameters ◽  
Ocean Models ◽  
Numerical Mixing ◽  
Comparable Magnitude ◽  
Ice Model

<p>Numerical mixing, the physically spurious diffusion of tracers due to the numerical discretization of advection, is known to contribute to biases in ocean circulation models. However, quantifying numerical mixing is non-trivial, with most studies utilizing specifically targeted experiments in idealized settings. Here, we present a precise method based on water-mass transformation for quantifying numerical mixing, including its spatial structure, that can be applied to any conserved variable in global general circulation ocean models. The method is applied to a suite of global MOM5 ocean-sea ice model simulations with differing grid spacings and sub-grid scale parameterizations. In all configurations numerical mixing drives across-isotherm heat transport of comparable magnitude to that associated with explicitly-parameterized mixing. Numerical mixing is prominent at warm temperatures in the tropical thermocline, where it is sensitive to the vertical diffusivity and resolution. At colder temperatures, numerical mixing is sensitive to the presence of explicit neutral diffusion, suggesting that much of the numerical mixing in these regions acts as a proxy for neutral diffusion when it is explicitly absent. Comparison of equivalent (with respect to vertical resolution and explicit mixing parameters) 1/4-degree and 1/10-degree horizontal resolution configurations shows only a modest enhancement in numerical mixing at the eddy-permitting 1/4-degree resolution. Our results provide a detailed view of numerical mixing in ocean models and pave the way for future improvements in numerical methods.</p>

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