Eulerian current measurements in the Strait of Otranto and in the Southern Adriatic
54
Citation
15
Reference
10
Related Paper
Citation Trend
Keywords:
Outflow
Sill
Drifter
Inflow
Empirical orthogonal functions
Barotropic fluid
Geostrophic current
Abstract The Northern Lembata Waters (NLW) is located in the Flores Sea that its dynamics is strongly affected by Monsoon Current and the Indonesian Throughflow (ITF). This study aims to describe the physical characteristics of the waters and geostrophic current, using observation CTD data from OTEC Cruise 2017. The type of water mass is identified using T-S diagram, and geostrophic currents is determined using a reference level at 600 dbar. From its characteristics such as temperature, salinity, and density it can be deduced that the waters vertically stratified. It is revealed a strong geostrophic flow due to water density differences. In the upper layer (0–300 dbar) geostrophic velocity ranged from 12.59 to 343.93 cm s −1 flowing eastward and in the deeper layer (300–600 dbar) geostrophic velocity (in section B) ranged from 7.66 to 49.19 cm s −1 flowing westward. The eastward flow is considered to be part of the ITF, and the westward flow at deeper layer may be associated with density-driven flow between Banda and Flores Seas.
Geostrophic current
Throughflow
Cite
Citations (1)
The flow characteristics in the region of the Azores Current are investigated by assimilating TOPEX/POSEIDON and ERS 1 altimeter data into the multilevel Harvard quasigeostrophic (QG) model with open boundaries (Miller et al., 1983) using an adjoint variational scheme (Moore, 1991). The study site lies in the path of the Azores Current, where a branch retroflects to the south in the vicinity of the Madeira Rise. The region was the site of an intensive field program in 1993, SEMAPHORE. We had two main aims in this adjoint assimilation project. The first was to see whether the adjoint method could be applied locally to optimize an initial guess field, derived from the continous assimilation of altimetry data using optimal interpolation (OI). The second aim was to assimilate a variety of different data sets and evaluate their importance in constraining our QG model. The adjoint assimilation of surface data was effective in optimizing the initial conditions from OI. After 20 iterations the cost function was generally reduced by 50–80%, depending on the chosen data constraints. The primary adjustment process was via the barotropic mode. Altimetry proved to be a good constraint on the variable flow field, in particular, for constraining the barotropic field. The excellent data quality of the TOPEX/POSEIDON (T/P) altimeter data provided smooth and reliable forcing; but for our mesoscale study in a region of long decorrelation times O (30 days), the spatial coverage from the combined T/P and ERS 1 data sets was more important for constraining the solution and providing stable flow at all levels. Surface drifters provided an excellent constraint on both the barotropic and baroclinic model fields. More importantly, the drifters provided a reliable measure of the mean field. Hydrographic data were also applied as a constraint; in general, hydrography provided a weak but effective constraint on the vertical Rossby modes in the model. Finally, forecasts run over a 2‐month period indicate that the initial conditions optimized by the 20‐day adjoint assimilation provide more stable, longer‐term forecasts.
Barotropic fluid
Dynamic height
Drifter
Sea-surface height
Cite
Citations (35)
governed by the seasonal wind system. During November 1977 and December 1982 geostrophic currents were directed in a north-northwest direction under the influence of the south-southeasterly winds of the southern half of the Red Sea. In March 1982 the currents were weak and variable ex cept at the northernmost section where the current had reversed to southsoutheast under the influence of the north-northwesterly winds. In May 1978 geostrophic currents were in a south-southeasterly direction. The current meter data during May 1978 also show that the current direction is the same as obtained from geostrophic computations.
Geostrophic current
Current meter
Thermal wind
Cite
Citations (1)
On the basis of CTD data obtained on 4 repeat-observed stations located at 121°E,19.5°N ~21°N in the Luzon Strait of the cruise in the summer of 2008,the role of disturbances caused by internal tides in temperature and salinity profiles in calculating of the geostrophic currents is discussed.The result shows that the role of disturbances caused by internal tides in temperature and salinity profiles in calculating of the geostrophic currents is significant.When we use hydrographic data to calculate the geostrophic currents we have to take measures to remove the disturbances caused by internal tides in temperature and salinity profiles,unless there would be great errors.By using the time-averaged CTD data,the geostrophic currents in the Luzon Strait is calculated.The result reveals that the significant part of the geostrophic currents appear above 350 m.Kuroshio intrusion mainly happens between 19.5°N and 21°N,especially at the upper layer.Between 19.5°N and 21°N,the water volume transport shows a in at upper and flowing out at deeper layer vertical structure,above 350 m the transport is westward(2.6 Sv) and below 350 m it is eastward(3.1 Sv).The distribution of the geostrophic currents we get is confirmed by the salinity distribution along 121°E Section.
Geostrophic current
Temperature salinity diagrams
Dynamic height
Cite
Citations (2)
Abstract : Dynamical features of polar oceans, captured by traditional treatment of hydrographic data sets, are only two fields: dynamical height of sea surface relative to certain depth, and geostrophic currents by assuming a certain level of no motion. Much information about the polar water is lost by such a treatment. In fact, the ocean flow is not purely geostrophically balanced. It contains two parts: geostrophic currents and ageostrophic circulations. The geostrophic currents are obtained from the hydrographic data sets (traditional physical oceanographic treatment), and the ageostrophic circulation is forced the geostrophic flow (called the geostrophic forcing) and surface wind field. Therefore, the three-dimensional circulation (both geostrophic and ageostrophic) can also be calculated by the hydrographic and surface wind data sets. There are potentially significant errors with the traditional treatment of the hydrographic data (e.g., only computing geostrophic currents), particularly in regions having strong temperature and salinity gradient, such as in the west Spitsbergen current. Neither geostrophic current nor dynamical height can provide detail information about the three-dimensional flow field near the west Spitsbergen current. In order to diagnose the three dimensional flow field, a new theory should be adapted.
Geostrophic current
Hydrographic survey
Forcing (mathematics)
Sea-surface height
Cite
Citations (0)
Drifter
Geostrophic current
Sea-surface height
Anomaly (physics)
Cite
Citations (15)
Geostrophic velocity and transport of water in the Drake Passage relative to a newly defined zero reference layer indicate that the circumpolar current is basically north of 59 degrees S, with its axis north 57 degrees S, and that the total volume transport exceeds 200 x 10(6) cubic meters per second. The calculated geostrophic velocities are consistent with results of descriptive water-structure studies.
Geostrophic current
Circumpolar star
Cite
Citations (23)
A 1965 survey of currents and geostrophic currents in the St. Lawrence estuary is described. An innovation employed in the survey was to moor the strings of oceanographic bottles in the cross-section and trip them simultaneously. A tidal oscillation was detected in the vertical shear of the geostrophic current as well as in the vertical shear of the axial and cross-channel current components. The observations qualitatively confirm predictions from a simple theory that is presented for geostrophic response on one-and two-layer canals. The theory suggests that the period of resonant cross-channel oscillation is an important time scale since current fluctuations of much longer periods reflect accurately in the geostrophic current, while fluctuations of shorter periods may appear as considerable distortions in the geostrophic current. From this, it is concluded that a single determination of geostrophic current may represent neither the instantaneous nor the long-term average current. The average geostrophic current over a time interval longer than the resonant period may, however, represent the average current over the same interval.
Geostrophic current
Oscillation (cell signaling)
Cite
Citations (9)
Geostrophic current
Sea-surface height
Ocean surface topography
Ocean dynamics
Cite
Citations (1)
Thermal wind relation is applied to compute the upper 1000-m layer meridional geostrophic velocity across the 18°N section in the South China Sea(SCS),based on the hydrographic data collected during the open cruises of northern SCS from 2005 to 2008 and merged altimetry data.The geostrophic velocity is compared with the Acoustic Doppler Current Profilers(ADCP) observations,and the upper 1000-m layer geostrophic volume,heat and salt transports across the 18°N section in the SCS are estimated.The results indicate that the meridional geostrophic velocities display belt distribution along the section during the cruises.The estimated geostrophic velocities are in good agreement with the ADCP data except at few stations.Sea surface height distribution derived from altimeter data shows that the distribution of meridional geostrophic velocities is closely related with mesoscale eddies.The total geostrophic volume,heat and salt transports of 2005 2007 in the upper 1000 m are all southward across 18°N,and the three-year-averaged values are 11.8 Sv,0.38 PW,and 418.8 Gg.s 1,respectively.However,the transport varies greatly from year to year.The volume,heat and salt transports of 2005 were the largest,while those of 2007 were the smallest.The geostrophic volume,heat and salt transports of 2008 from 110°E to 117°E are 7.3 Sv,0.22 PW,and 259.4 Gg.s 1,respectively.
Geostrophic current
Thermal wind
Cite
Citations (2)