Papers by Yoshimine Ikeda
Boletim do Instituto Oceanográfico, 1980
A mesoscale study was made of the Ilha Grande area. The local circulation described through progr... more A mesoscale study was made of the Ilha Grande area. The local circulation described through progressive vector diagramsshowed a clockwise bottom circu-Zation determined in June 1976~ while in the upper 10 m the direction of the flow entering the Ilha Grande Bay was towards the center in the west and towards the Marambaia sandbank in the east side of the Bay. Short periods and amplitude fluctuations were evaluted using power spectral analysis~ Fourier and Maximum Entropy Method~ which shçwed that in the upper 10 m predominant peri~ds decrease from 1.lh (A = 6.3em sec-1) (position = 3C) to 1.Oh (A = •7.4emsec-1) (position = 2D) and increase to 5.8h (A = 6.8 em. . sec-1) (position = lD) ~ while at the bottom Zayer the predominant period increases from 0.4 h (A = 5. O em sec-1) (position = 3G) to 6.4 h (A = 7.0cmsec-1) (position = 2G) and to 4.4h (A = 7.9 emsec-1) (position = lG). From the original data it has been possible to determine an "intense pulsation" between 30-70óm sec-1 in the upper 10 m with about 1. Oh period and 10-20 min duration in all the stations.
Deep Sea Research, 1990
Geostrophic volume transports in the upper 500 m are computed from historical hydrographic data f... more Geostrophic volume transports in the upper 500 m are computed from historical hydrographic data for the area off the Brazilian coast west of 30*W and between 7 ° and 20"S. On the basis of water mass distributions, potential density surfaces of o0 = 27.05 kg m-3 (360-670 m) and o8 = 27.6 kg m-3 (-1200 m) are used for referencing the meridional and zonal components of the geostrophic shears, respectively. Near 15"S a northwestward flow of 8 Sv crosses 30*W. This current reaches the shelf near 10"S in February and March, the only two months for which observations are available near that latitude along the coast; of the 8 Sv, about 4 Sv continue towards the northwest into the North Brazil Current while another branch also carrying 4 Sv turns southward as the beginning of the Brazil Current. Between 10 ° and 20~S the Brazil Current does not appear to strengthen appreciably, but because of the likely existence of flow on the shelf these transport values represent lower limits to the actual ones. At 30°W, another westward flow of approximately 8-10 Sv enters the area near 10°S and serves to strengthen the North Brazil Current. The total transfer of 12 Sv or more from the South Equatorial Current into the North Brazil Current and later to other currents and the northern hemisphere may be an important factor contributing to the well-known weakness of the Brazil Current in its more northerly latitudes.
Deep-sea research, Dec 1, 1990
Geostrophic volume transports in the upper 500 m are computed from historical hydrographic data f... more Geostrophic volume transports in the upper 500 m are computed from historical hydrographic data for the area off the Brazilian coast west of 30*W and between 7 ° and 20"S. On the basis of water mass distributions, potential density surfaces of o0 = 27.05 kg m-3 (360-670 m) and o8 = 27.6 kg m-3 (-1200 m) are used for referencing the meridional and zonal components of the geostrophic shears, respectively. Near 15"S a northwestward flow of 8 Sv crosses 30*W. This current reaches the shelf near 10"S in February and March, the only two months for which observations are available near that latitude along the coast; of the 8 Sv, about 4 Sv continue towards the northwest into the North Brazil Current while another branch also carrying 4 Sv turns southward as the beginning of the Brazil Current. Between 10 ° and 20~S the Brazil Current does not appear to strengthen appreciably, but because of the likely existence of flow on the shelf these transport values represent lower limits to the actual ones. At 30°W, another westward flow of approximately 8-10 Sv enters the area near 10°S and serves to strengthen the North Brazil Current. The total transfer of 12 Sv or more from the South Equatorial Current into the North Brazil Current and later to other currents and the northern hemisphere may be an important factor contributing to the well-known weakness of the Brazil Current in its more northerly latitudes.
Boletim do Instituto Oceanográfico, 1977
Continuous records of temperature and sa1inity wer.e obtained on the surface waters as function o... more Continuous records of temperature and sa1inity wer.e obtained on the surface waters as function of the horizontal distances around Ilha Grande region, on June 21, 1975; an outflow of less sa1ine (S-33.10 0/00) and slight1y warmer water was detected throughout the region between Ponta de Castelhanos and Ponta Grossa da Marambãia and a visible manifestation of a saline front was observed in the interaction of this outflow with the coas tal and more saline water (S ~ 35.4 to 35.6 0/00). The recorded sa1inity va1ues in the east region of Ilha Grande, suggest that the source of 1ess saline water is the runoff in the Baía de Sepetiba. * Grants were awarded to the authors by Fundação de Amparo a Pesquisa do Estado de são Paulo (FAPESP).
Remote Sensing of Environment, Oct 1, 1978
ABSTRACT Through time series analysis of GOSSTCOMP satellite data, time differences in the occurr... more ABSTRACT Through time series analysis of GOSSTCOMP satellite data, time differences in the occurrence of maximum and minimum mean monthly SST's off the coast of Brazil were observed in the region of 20–28° S by 34–47° W and showed the maximum surface water temperature to lag the coastal land station (Cananeia) by two months and the minimum by one month. For annual components of SST, maximum amplitudes were observed at Cabo Frio (influenced by upwelling) and Cananeia (influenced by Malvinas current) and minimum amplitudes at coastal and oceanic area between Ubatuba and Santos, a more thermally stable area.
Journal of Geophysical Research, Mar 15, 1998
Current measurements from three moored arrays on the Brazilian continental slope between 20øS and... more Current measurements from three moored arrays on the Brazilian continental slope between 20øS and 28øS are investigated for the existence and strength of western boundary currents from near the surface down to the North Atlantic Deep Water. The Brazil Current is found to deepen southward from 100 rn to more than 670 rn and to strengthen its volume transport to 16.2 x !06 m3/s. Antarctic Intermediate Water is transported in a well-developed boundary current southward at 28øS and northward north of Cabo Frio (24øS). This result supports earlier suggestions derived from the analysis of hydrographic data that Antarctic Intermediate Water enters the Brazil Basin from the east and bifurcates as it meets the continental break off Brazil. North Atlantic Deep Water is transported southward in a weakly developed boundary current that leads to lower estimates of volume transport than expected from earlier hydrographic data analysis. 1. Introduction The South Atlantic is known to be the highway on which the major interoceanic exchange of water masses and, consequently, of heat and salt occurs. As a result of the Meteor expedition 1925-1927 into the South Atlantic, Wast [!935] and Defant [1936a, b] illustrated the South Atlantic's deep and near-surface circulation, which in its general structure still holds for the subtropical western South Atlantic off Brazil. Much of the associated volume transports is carried in western boundary currents that in early theories are required to balance the interior ocean circulation [Stommel, 1948; Stommel and Aarons, 1960]. Principally, this concept could apply to all layers of deep and intermediate waters. For the Brazil Basin, one therefore would expect not only the near-surface Brazil Current balancing the wind-driven circulation, but also bound~ ary currents in the layers of the Antarctic Intermediate Water (AAIW), the Upper Circumpolar Deep Water (UCDW), the three layers of the North Atlantic Deep Water (NADW), and the Antarctic Bottom Water (AABW). While deep boundary currents carrying NADW southward and AABW northward have been described in the literature, a northward spreading of AAIW and UCDW within boundary currents has been less studied, and analysis was restricted to hydrographic data. For broad reviews of the present knowledge of the South Atlantic's water masses and general circulation as derived from hydrographic measurements, the reader is referred to Reid [!989], Peterson and Stramma [199!], DeMadron and Weatherly [1994], and Tsuchiya et al. [!994]. Few direct current observations were available from the boundary current system along the South American coast when the World Ocean Circulation Experiment (WOCE) began with its Deep Basin Experiment (DBE) in 1990. The then available records from moored current meters show the existence of a
Boletim do Instituto Oceanográfico, 1982
Seasonal differences in sigma-t (1.8), temperature (4.0 0 C) and salinity (0.9% 0) were observed ... more Seasonal differences in sigma-t (1.8), temperature (4.0 0 C) and salinity (0.9% 0) were observed during February/June 1976 in the vicinity of Ilha Grande off the coast of Brazi~. Estimates of static and dynamic stability were made through the calcu-Zation of Brunt-Vàisala frequencies and Richardson numbers, respectively. Both static and dynamic stability values were larger in February than in June for the same location and suggest a greater column stability in February than in June. Stations located in the northern and western channels of Ilha Grande, however, contained greater density reversals than to the east of the Island. SrraU scale dispersion studies were made using Rhomamine B dye to determine horizontal diffusion coefficients (K) east of the IsZand and in an embayment of the Island. The estimate for K was 9X10 3 cm 2 S-l east of the Island, about 2.6 times greater than the value estirrated for the protected embayment.
Boletim do Instituto Oceanográfico, 1976
Boletim do Instituto Oceanográfico, 1985
ComputationJ developed by NOAAjNESS, USA, and sea surface current data based from ships drift inf... more ComputationJ developed by NOAAjNESS, USA, and sea surface current data based from ships drift info~ation obtained from Pilot Charts, published by the Diretoria de Hidrografia e Navegação (DHN, Brazilian NavyJ. The annual mean value of the heat flux balance at the sea surface off southeast Brazil for 19??, is estimated from data on the balance between the heat transported by the currents and that transported by eddy diffusion for each volume defined as 2° x 2° (Lat. x Long.J square with a constant depth equivalent to an oceanic mixed layer, 100 m thick. Results show several oceanic areas where there are net flows of heat from atmosphere towards the sea surface. In front of Rio de Janeiro the heat flow was downward and up to ?O ly day-l and is probably related to the upwelling phenomenon normally occurring in that area. Another coastal are a between Lat. 25°S to 28°S indicated an ábwnward flow up to 50 ly day-l; and for an area south of Lat. 2?oS, Long. 040 0 W-048°Wan ábwYU;Jard flow up to 200 ly day_l, where the transfer was probably due to the cold tUater of a nortward flux from the Falkland (MalvinasJ Current. Results also show several oceanic areas where net flows of heat (of about-100 ly day-lJ were toward the atmosphere. In the oceanic are as Lat. 19°5-23°S and Lat. 24°S-30 0 S, the flows were probably due to the warm water of a southward flux of the Brazil Current. The resulting fluxes from the warm waters of the Brazil Current when compared with those from warm waters of the Gulf Stream and Kuroshio, indicate that the Gulf Stream carries about 3.3 times and the Kuroshio 1.? times more heat than the Brazil Current. These values agree with those of data available on the heat fluxes of the above mentioned Currents calculated by different methods (Budyko, 19?4J.
DOAJ (DOAJ: Directory of Open Access Journals), 1974
A brief outline is given of the results of surface temperature and salinity to the west and south... more A brief outline is given of the results of surface temperature and salinity to the west and southwest of Cabo Frio obtained in August of 1971 with a continuous recording Thermo-Salinograph (Bissett-Berman, Model 6600T). A rapid change was observed in the field distribution of temperature from 2l.5-2l.9 0 C to l5-2l o C, and similary change in the distribution of salinity from 34.1-35.0 0 /00 to 35.3-36.0 0 /00, over a time scale of seven days. The changes were accredited to the process of upwelling at the coastal region under the influence of E and NE winds. The occurrence of a surface counter-current moving upwind was detected. This anomaly, not explained on the basis of the Ekman's classical theory, was qualitatively explained as the result of a horizontal divergence in the wind-stress field.
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Papers by Yoshimine Ikeda