Download or read book Dynamics of the Antarctic Circumpolar Current A C C written by Takashi Ichiye and published by . This book was released on 1967 with total page 52 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Dynamics of the Antarctic Circumpolar Current A C C written by Takashi Ichiye and published by . This book was released on 1967 with total page 48 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Dynamics of the Antarctic Circumpolar Current A C C written by Takashi Ichiye and published by . This book was released on 1967 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Contributions to the Dynamics of the Antarctic Circumpolar Current A C C II written by Takashi Ichiye and published by . This book was released on 1975 with total page 68 pages. Available in PDF, EPUB and Kindle. Book excerpt: Non-dimensional equations of motion are derived for the A.C.C. of the barotropic mode, including the bottom friction and the horizontal eddy viscosity. Integration of the vorticity equation leads to the zeroth order stream function which is dependent only on depth divided by Coriolis' parameter. Integration of the momentum equation along a streamline yields the relation between the momentum input by wind stress and its dissipation by the bottom friction and by the horizontal eddy viscosity. The relation determines the magnitude of the stream function. It also explains differences in the total transport of the A.C.C. obtained by Kamenkovich (1962) and by Bryan and Cox (1972).

Download or read book Dynamics of the Antarctic Circumpolar Current written by Sarah Tragler Gille and published by . This book was released on 1995 with total page 226 pages. Available in PDF, EPUB and Kindle. Book excerpt: Geosat altimeter data and numerical model output are used to examine the circulation and dynamics of the Antarctic Circumpolar Current (ACC). The mean sea surface height across the ACC has been reconstructed from height variability measured by the Geosat altimeter, without assuming prior knowledge of the geoid. For this study, an automated technique has been developed to estimate mean sea surface height for each satellite ground track using a meandering Gaussian jet model, and errors have been estimated using Monte Carlo simulation. The results are objectively mapped to produce a picture of the mean Subantarctic and Polar Fronts, which together comprise the major components of the ACC. The locations of the fronts are consistent with in situ observations and indicate that the fronts are substantially steered by bathymetry. The jets have an average Gaussian width of about 44 km in the meridional direction and meander about 75 km to either side of their mean locations. The width of the fronts is proportional to 1/f, indicating that with constant stratification, the width is proportional to the baroclinic. Rossby radius. The average height difference across the Subantarctic Front (SAF) is 0.7 m and across the Polar Front (PF) 0.6 m. The mean widths of the fronts are correlated with the size of the baroclinic Rossby radius. The meandering jet model explains between 40% and 70% of the height variance along the jet axes. Bathymetric constrictions are associated with increased eddy variability, a smaller percentage of which may be explained by the meandering of the ACC fronts, indicating that propagating eddies and rings may be spawned at topographic features. Detailed examination of spatial and temporal variability in the altimeter data indicates a spatial decorrelation scale of 85 km and a temporal e-folding scale of 34 days. The sea surface height variability is objectively mapped using these scales to define autocovariance functions. The resulting maps indicate substantial evidence of mesoscale eddy activity. Over 17-day time intervals, meanders of the PF and SAF appear to elongate, break off as rings, and propagate. Statistical analysis of ACC variability from altimeter data is conducted using empirical orthogonal functions (EOFs). The first mode EOF describes 16% of the variance in total sea surface height across the ACC; reducing the domain into basin scales does not significantly increase the variance represented by the first EOF, suggesting that the scales of motion are relatively short, and may be determined by local instability mechanisms rather than larger basin scale processes. Likewise, frequency domain EOFs indicate no statistically significant traveling wave modes. The momentum balance of the ACC has been investigated using both output from a high resolution primitive equation model and sea surface height measurements from the Geosat altimeter. In the Semtner-Chervin general circulation model, run with approximately quarter-degree resolution and time varying ECMWF winds, topographic form stress is the dominant process balancing the surface wind forcing. Detailed examination of form stress in the model indicates that it is due to three large topographic obstructions located at Kerguelen Island, Campbell Plateau, and Drake Passage. In order to reduce the effects of standing eddies, the model momentum balance is considered in stream coordinates; vertically integrated through the entire water column, topographic form drag is the dominant balance for wind stress. However, at mid-depth the cross-stream momentum transfer is dominated by horizontal biharmonic friction. In the upper ocean, horizontal friction, mean momentum flux divergence, transient momentum flux divergence, and mean vertical flux divergence all contribute significantly to the momentum balance. Although the relative importance of individual terms in the momentum balance does not vary substantially along streamlines, elevated levels of eddy kinetic energy are associated with the three major topographic features. In contrast, altimeter data show elevated energy levels at many more topographic features of intermediate scales, suggesting that smaller topographic effects are better able to communicate with the surface in the real ocean than in the model. Transient Reynolds stress terms play a small role in the the overall momentum balance; nonetheless, altimeter and model measurements closely agree, and suggest that transient eddies tend to accelerate the mean flow, except in the region between the major fronts which comprise the ACC. Potential vorticity is considered in the model output along Montgomery streamfunction. Even at about 1000 m depth, it varies in response to wind forcing, largely as a result of changes in vertical stratification, indicating that forcing and dissipation do not locally balance in the Southern Ocean. In order to compare model and altimeter potential vorticity estimates, two different proxies for potential vorticity on surface streamlines are considered. Both proxies show very similar results for model and altimeter, suggesting that differences in surface streamlines estimated by the altimeter and the model are not significant in explaining the Southern Ocean flow. The proxies are both roughly conserved along surface height contours but undergo substantial jumps near topographic features. However, they cannot capture stratification changes which may be critically important to the overall potential vorticity balance.

Download or read book Dynamics of the Antarctic Circumpolar Current A C C written by Takashi Ichiye and published by . This book was released on 1967 with total page 68 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Observations of Antarctic Circumpolar Current Dynamics in the Drake Passage and Small scale Variability Near the Antarctic Peninsula written by Yueng Djern Lenn and published by . This book was released on 2006 with total page 136 pages. Available in PDF, EPUB and Kindle. Book excerpt: Recent high-resolution underway observations in Drake Passage are employed to study the surface-layer currents and momentum balance of the Antarctic Circumpolar Current (ACC). Ocean currents were measured with a ship-mounted acoustic Doppler current profiler and upper ocean temperatures surveyed with expendable bathythermographs deployed from the R/V Laurence M Gould, during every season of the annual cycle over a 5-year period. The finely-resolved mean flow estimated from observed currents shows the topographic control of the mean Subantarctic Front (SAF) and the along-stream convergence of multiple filaments of the Polar Front (PF) and Southern ACC Front (SACCF) into single mean jets. Mean cross-track transport above 250 m is 28.7 " 1 Sv and accounts for 20% of the total Drake Passage transport. Subtracting geostrophic current anomalies inferred from altimetry from the instantaneous velocity observations markedly reduces the velocity variance and results in an improved estimate of mean currents. Variance is attributed to mesoscale eddies, inertial currents, and least of all, baroclinic tides. Horizontal-wavenumber spectra of velocity fluctuations peak at wavelengths of?200 km and are significantly anisotropic in a manner consistent with aspects of geostrophic turbulence. Eddy kinetic energy is surface intensified and decreases poleward in Drake Passage; in situ estimates are significantly higher than altimetric estimates everywhere. A mean Ekman spiral observed in Drake Passage verifies the Ekman balance; the Ekman layer is approximately 100 m deep. Eddy momentum and heat fluxes are averaged along streamlines inferred from the improved mean flow. These indicate that eddies flux vorticity along the axis of the SAF in the vicinity of the Patagonian continental slope and accelerate the PF in Drake Passage. However, the eddy forcing is small, implying that eddies transmit the surface wind stress downwards undiminished via an interfacial form stress. Variability in specific dynamic height contours correlated with each ACC front is used to examine the meandering and topographic control of the Drake Passage fronts. Finally an analysis of the annual cycle of the circulation of Port Foster, Deception Island is presented. Moored observations of water temperature, currents and acoustic backscatter show that seasonal, tidal and diurnal processes dominate the variability of this ecosystem.

Download or read book Dynamics of a Quasigeostrophic Antarctic Circumpolar Current written by Louis-Philippe Nadeau and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Structure and Variability of the Antarctic Circumpolar Current written by Ėduard Iosifovich Sarukhani︠a︡n and published by . This book was released on 1985 with total page 124 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Structure and Dynamical Balance of the Antarctic Circumpolar Current in Drake Passage written by Yvonne L. Firing and published by . This book was released on 2012 with total page 172 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis investigates the structure and dynamics of the Antarctic Circumpolar Current (ACC) in Drake Passage using observations that resolve spatial scales from 100 m to 1000 km and temporal scales from inertial to interannual. The structure and variability of the current, the eddy and mean contributions to the vorticity balance, and the patterns of internal wave activity are examined. The two primary sources of data are a long time series (2005-present) of upper ocean currents from the ARSV Laurence M. Gould (LMG) shipboard acoustic Doppler current profiler (SADCP), and a four-year process study (cDrake) providing time series of near-bottom currents, bottom pressures, and bottom-surface sound travel times as well as bathymetry, lowered ADCP, and CTD data from five yearly cruises. The vertical structure in the upper 1000 m is equivalent barotropic, with variable vertical length scale. The mean transport in the upper 1000 m is 95±2 Sv. Transport variability is approximately equally divided between shear and depth-mean components. Eddy kinetic energy decreases with depth faster than mean kinetic energy, reinforcing the view of the ACC as a barrier to mixing. Using empirical relationships determined from historical hydrography, travel time data from the cDrake array in the PFZ can be converted to baroclinic streamfunction. The near-bottom current and bottom pressure measurements provide the barotropic reference velocity. Streamfunction derivatives can be computed by objective mapping. We used independent measurements and simulated idealized fields to validate the objectively mapped fields and error estimates. Mean and eddy nonlinear vorticity advection and bottom pressure torque dominate the mean vorticity balance. The residual is first order. SOSE has the same balance and similar scales, with the residual accounted for by sub-grid-scale dissipation. In the southeastern Pacific a Rossby-wave-like balance between mean relative vorticity advection and planetary vorticity advection is observed. Downward-propagating internal wave energy and shear-strain ratios consistent with near-inertial frequencies predominate over deep waters and in the surface layer. Over shallower topography upward-propagating energy and supra-inertial frequencies dominate. The seasonal cycles in wind stress and internal wave energy south of the Polar Front are aligned; the seasonal cycle north of the Polar Front matches that in surface-layer stratification.

Download or read book The Variability and Dynamics of the Antartic Circumpolar Current South of Africa Using Proxy Techniques written by Sebastiaan Swart and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The general circulation of the Southern Ocean is dominated by the eastward flowing Antarctic Circumpolar Current (ACC). This is a continuous feature linking the three major ocean basins and thus forms a vital link in the transport of heat and salt on a global scale. These exchanges provide a vital mechanism for the global thermohaline circulation (THC), which regulates the Earthâs climate. In the high latitudes, where conditions are hostile, routine hydrographic observations are scarce resulting in a poor understanding of the physical and dynamic processes controlling the variability of the ACC and its influence on the THC. The GoodHope program launched in early 2004 aimed to establish an intensive monitoring platform that would provide detailed information on the physical structure and volume flux of water masses south of Africa. Sustained observations along the GoodHope cruise track provide the means to monitor the vertical structure and variability of the ACC and its associated fronts south of Africa. Such intense monitoring has been under way in the Drake Passage and south of Australia since the 1970s. A major objective of this thesis is to provide sound estimates of ACC transport and variability using both in situ measurements and remote sensing techniques. These estimates are crucial in understanding the role the ACC plays in the global thermohaline circulation (THC) and how the region south of Africa acts as a major conveyor of heat and salt to the higher latitudes. Baroclinic transports of the ACC, relative to 2500 dbar, are calculated from altimetry data alone. These transports agree with simultaneous observed estimates (rms difference in net transport is 5.2 Sv). These observations suggest that sea level anomalies largely reflect baroclinic transport variations above 2500 dbar. The transports contribution per ACC front shows that the SAF is responsible for the highest variability signals (>50%) even though its net transport contribution to

Download or read book Antarctic Climate Evolution written by Fabio Florindo and published by Elsevier. This book was released on 2008-10-10 with total page 606 pages. Available in PDF, EPUB and Kindle. Book excerpt: Antarctic Climate Evolution is the first book dedicated to furthering knowledge on the evolution of the world's largest ice sheet over its ~34 million year history. This volume provides the latest information on subjects ranging from terrestrial and marine geology to sedimentology and glacier geophysics. - An overview of Antarctic climate change, analyzing historical, present-day and future developments - Contributions from leading experts and scholars from around the world - Informs and updates climate change scientists and experts in related areas of study

Download or read book Dynamics of the Antarctic Circumpolar Current written by Michael Devine and published by . This book was released on 1969 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The dynamics of the Antarctic Circumpolar Current written by V.O. IVCHENKO and published by . This book was released on 1996 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Dynamics of the Antarctic Circumpolar Current written by Patrick Cooper and published by . This book was released on 2011 with total page 41 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Ocean Circulation and Climate written by Stephen R. Rintoul and published by Elsevier Inc. Chapters. This book was released on 2013-10-22 with total page 58 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Southern Ocean circulation connects the ocean basins as well as the upper and deep layers of the ocean. As a result, the region has a profound influence on the global ocean circulation and climate. The Antarctic Circumpolar Current and the overturning circulation are dynamically linked through interactions between the mean flow, eddies, topography, air–sea forcing, and mixing and stirring by small- and mesoscale processes. A new dynamical paradigm is emerging that emphasizes the fully three-dimensional nature of the circulation, including the localization of meridional and vertical exchange of momentum, vorticity, and tracers by interactions between the flow and topography. Changes observed in the Southern Ocean in recent decades have implications for global climate and provide insight into the response of the Southern Ocean circulation to changes in forcing.

Download or read book Oceanography of the Ross Sea Antarctica written by Giancarlo Spezie and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 415 pages. Available in PDF, EPUB and Kindle. Book excerpt: The era of the exploration of the World Ocean is not yet over: some areas still lack an adequate number of observations. The relationships between the physical, chemical and biological processes, which sustain the life on this planet, are not yet fully understood. In short, knowledge of the oceans is still far from satisfactory. This book covers an important period in the study of one of the last investigated areas of the World Ocean: the Ross Sea, Antarctica. During the 1990s, long-term experiments were conducted in this area as part of the Climatic Long-term Interaction for the Mass balance in Antarctica (CLIMA) project of the Italian National Programme for Antarctic Research (PNRA), providing a wealth of oceanographic information. This book is an outcome of the CLIMA field obser vations and international collaborations with the most important programmes in the Ross Sea-Southern Ocean area. It contributes to the st!ldies of the spatial and temporal variability of Ross Sea water masses and circulation and their relation ship with the Southern Ocean circulation. A comprehensive review of historical data is offered, and new data sets are analysed. The studies presented in this book show that much progress has been achieved during the last decade, but large gaps in our understanding of the physical processes in the Ross Sea are still to be filled. However, these studies contribute significantly to the investigation of some specific aspects regarding the circula tion of the main water masses.