scholarly journals Surface Geostrophic Circulation of the Mediterranean Sea Derived from Drifter and Satellite Altimeter Data

2012 ◽  
Vol 42 (6) ◽  
pp. 973-990 ◽  
Author(s):  
Pierre-Marie Poulain ◽  
Milena Menna ◽  
Elena Mauri
Keyword(s):  
Kinetic Energy ◽  
Mediterranean Sea ◽  
Surface Waters ◽  
Energy Levels ◽  
Altimeter Data ◽  
Mean Flow ◽  
Satellite Altimeter ◽  
The Mean ◽  
Surface Geostrophic Circulation ◽  
Satellite Altimeter Data

Abstract Drifter observations and satellite-derived sea surface height data are used to quantitatively study the surface geostrophic circulation of the entire Mediterranean Sea for the period spanning 1992–2010. After removal of the wind-driven components from the drifter velocities and low-pass filtering in bins of 1° × 1° × 1 week, maps of surface geostrophic circulation (mean flow and kinetic energy levels) are produced using the drifter and/or satellite data. The mean currents and kinetic energy levels derived from the drifter data appear stronger/higher with respect to those obtained from satellite altimeter data. The maps of mean circulation estimated from the drifter data and from a combination of drifter and altimeter data are, however, qualitatively similar. In the western basin they show the main pathways of the surface waters flowing eastward from the Strait of Gibraltar to the Sicily Channel and the current transporting waters back westward along the Italian, French, and Spanish coasts. Intermittent and long-lived subbasin-scale eddies and gyres abound in the Tyrrhenian and Algerian Seas. In the eastern basin, the surface waters are transported eastward by several currents but recirculate in numerous eddies and gyres before reaching the northward coastal current off Israel, Lebanon, and Syria and veering westward off Turkey. In the Ionian Sea, the mean geostrophic velocity maps were also produced separately for the two extended seasons and for multiyear periods. Significant variations are confirmed, with seasonal reversals of the currents in the south and changes of the circulation from anticyclonic (prior to 1 July 2007) to cyclonic and back to anticyclonic after 31 December 2005.

scholarly journals Characteristics, Energetics, and Origins of Agulhas Current Meanders and Their Limited Influence on Ring Shedding

2015 ◽  
Vol 45 (9) ◽  
pp. 2294-2314 ◽  
Author(s):  
Shane Elipot ◽  
Lisa M. Beal
Keyword(s):  
Kinetic Energy ◽  
Single Mode ◽  
Cyclonic Circulation ◽  
Recent Analysis ◽  
Altimeter Data ◽  
Western Boundary ◽  
Mean Flow ◽  
Current Time ◽  
Agulhas Current ◽  
The Mean

AbstractThe Agulhas Current intermittently undergoes dramatic offshore excursions from its mean path because of the downstream passage of mesoscale solitary meanders or Natal pulses. New observations and analyses are presented of the variability of the current and its meanders using mooring observations from the Agulhas Current Time-Series Experiment (ACT) near 34°S. Using a new rotary EOF method, mesoscale meanders and smaller-scale meanders are differentiated and each captured in a single mode of variance. During mesoscale meanders, an onshore cyclonic circulation and an offshore anticyclonic circulation act together to displace the jet offshore, leading to sudden and strong positive conversion of kinetic energy from the mean flow to the meander via nonlinear interactions. Smaller meanders are principally represented by a single cyclonic circulation spanning the entire jet that acts to displace the jet without extracting kinetic energy from the mean flow. Synthesizing in situ observations with altimeter data leads to an account of the number of mesoscale meanders at 34°S: 1.6 yr−1 on average, in agreement with a recent analysis by Rouault and Penven (2011) and significantly less than previously understood. The links between meanders and the arrival of Mozambique Channel eddies or Madagascar dipoles at the western boundary upstream are found to be robust in the 20-yr altimeter record. Yet, only a small fraction of anomalies arriving at the western boundary result in meanders, and of those, two-thirds can be related to ring shedding. Most Agulhas rings are shed independently of meanders.

scholarly journals ENERGY INTERACTION OF THE JETS AND EDDIES OF ANTARCTIC CIRCUMPOLAR CURRENT IN THE NEAR-SURFACE LAYER OF THE SOUTHERN OCEAN

2019 ◽  
Vol 47 (3) ◽  
pp. 39-57
Author(s):  
M. N. Koshlyakov ◽  
R. Yu. Tarakanov ◽  
D. S. Savchenko
Keyword(s):  
Surface Layer ◽  
Antarctic Circumpolar Current ◽  
Altimeter Data ◽  
Satellite Altimeter ◽  
Near Surface ◽  
Synoptic Eddies ◽  
The Mean ◽  
Circumpolar Current ◽  
The Antarctic ◽  
Satellite Altimeter Data

Kinetic energy six jets of the Antarctic Circumpolar Current (ACC), and of synoptic eddies generated by these jets is studied in application to the near-surface layer of the Antarctic Circle on the base of the satellite altimeter data during 1993–2015. The main results of the study were as follows: a) prevalence of the energy of middle jet of the Subantarctic Current over energy of the rest ACC jets in the whole of the Antarctic Circle; b) five times excess of the mean energy of jets proper over the mean summary (cyclones plus anticyclones) energy of eddies; c) two times excess of mean energy of cyclonic eddies over energy of anticyclones.

scholarly journals Nonlinear Cascades of Surface Oceanic Geostrophic Kinetic Energy in the Frequency Domain*

2012 ◽  
Vol 42 (9) ◽  
pp. 1577-1600 ◽  
Author(s):  
Brian K. Arbic ◽  
Robert B. Scott ◽  
Glenn R. Flierl ◽  
Andrew J. Morten ◽  
James G. Richman ◽  
...  
Keyword(s):  
Kinetic Energy ◽  
Frequency Domain ◽  
General Circulation ◽  
General Circulation Models ◽  
Altimeter Data ◽  
Satellite Altimeter ◽  
Frequency Spectra ◽  
Low Frequencies ◽  
Spectral Flux ◽  
Satellite Altimeter Data

Abstract Motivated by the ubiquity of time series in oceanic data, the relative lack of studies of geostrophic turbulence in the frequency domain, and the interest in quantifying the contributions of intrinsic nonlinearities to oceanic frequency spectra, this paper examines the spectra and spectral fluxes of surface oceanic geostrophic flows in the frequency domain. Spectra and spectral fluxes are computed from idealized two-layer quasigeostrophic (QG) turbulence models and realistic ocean general circulation models, as well as from gridded satellite altimeter data. The frequency spectra of the variance of streamfunction (akin to sea surface height) and of geostrophic velocity are qualitatively similar in all of these, with substantial variance extending out to low frequencies. The spectral flux Π(ω) of kinetic energy in the frequency ω domain for the QG model documents a tendency for nonlinearity to drive energy toward longer periods, in like manner to the inverse cascade toward larger length scales documented in calculations of the spectral flux Π(k) in the wavenumber k domain. Computations of Π(ω) in the realistic model also display an “inverse temporal cascade.” In satellite altimeter data, some regions are dominated by an inverse temporal cascade, whereas others exhibit a forward temporal cascade. However, calculations performed with temporally and/or spatially filtered output from the models demonstrate that Π(ω) values are highly susceptible to the smoothing inherent in the construction of gridded altimeter products. Therefore, at present it is difficult to say whether the forward temporal cascades seen in some regions in altimeter data represent physics that is missing in the models studied here or merely sampling artifacts.

scholarly journals Study of the Overflow Transport of the Nordic Sea

Water ◽  
2021 ◽  
Vol 13 (19) ◽  
pp. 2675
Author(s):  
Wenqi Shi ◽  
Ning Li ◽  
Xianqing Lv
Keyword(s):  
Ocean Circulation ◽  
Pressure Difference ◽  
Deep Convection ◽  
Volume Transport ◽  
Altimeter Data ◽  
Water Production ◽  
Satellite Altimeter ◽  
Salt Structure ◽  
The Mean ◽  
Satellite Altimeter Data

Changes in the climate system over recent decades have had profound impacts on the mean state and variability of ocean circulation, while the Nordic Sea overflow has remained stable in volume transport during the last two decades. The changes of the overflow flux depend on the pressure difference at the depth of the overflow outlet on both sides of the Greenland-Scotland Ridge (GSR). Combining satellite altimeter data and the reanalysis hydrological data, the analysis found that the barotropic pressure difference and baroclinic pressure difference on both sides of the GSR had a good negative correlation from 1993 to 2015. Both are caused by changes in the properties of the upper water, and the total pressure difference has no trend change. The weakening of deep convection can only change the temperature and salt structure of the Nordic Sea, but cannot reduce the mass of the water column. Therefore, the stable pressure difference drives a stable overflow. The overflow water storage in the Nordic Sea is decreasing, which may be caused by the reduction of local overflow water production and the constant overflow flux. When the upper interface of the overflow water body in the Nordic Sea is close to or below the outlet depth, the overflow is likely to greatly slow down or even experience a hiatus in the future, which deserves more attention.

A Feasibility Demonstration of Ocean Model Eddy-resolving Nowcast/Forecast Skill Using Satellite Altimeter Data

2000 ◽  
Author(s):  
Harley E. Hurlburt ◽  
Robert C. Rhodes ◽  
Charlie N. Barron ◽  
E. J. Metzger ◽  
Ole M. Smedstad
Keyword(s):  
Ocean Model ◽  
Forecast Skill ◽  
Altimeter Data ◽  
Satellite Altimeter ◽  
Satellite Altimeter Data

Estimating discharge of the Ganga River from satellite altimeter data

2021 ◽  
pp. 126860
Author(s):  
Atul Kumar Rai ◽  
Zafar Beg ◽  
Abhilash Singh ◽  
Kumar Gaurav
Keyword(s):  
Ganga River ◽  
Altimeter Data ◽  
Satellite Altimeter ◽  
Satellite Altimeter Data
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