scholarly journals Moored current meter data from the Atlantic north equatorial counter current near 6�N 28�W (February-September, 1983) : vol. XXXIV

1984 ◽  
Author(s):  
Ellen Levy ◽  
Philip L. Richardson
Keyword(s):  
North Equatorial Counter Current ◽  
Counter Current ◽  
Moored Current Meter Data

scholarly journals Effect of the North Equatorial Counter Current on the generation and propagation of Internal Solitary Waves off the Amazon shelf (SAR observations)

2015 ◽  
Vol 12 (5) ◽  
pp. 2497-2534
Author(s):  
J. M. Magalhaes ◽  
J. C. B. da Silva ◽  
M. C. Buijsman ◽  
C. A. E. Garcia
Keyword(s):  
Seasonal Variability ◽  
Internal Tide ◽  
Ocean Model ◽  
Horizontal Structure ◽  
The North ◽  
Budget Analysis ◽  
North Equatorial Counter Current ◽  
Amazon Shelf ◽  
Sar Imagery ◽  
Counter Current

Abstract. Synthetic Aperture Radar (SAR) imagery from the Amazon shelf-break region in the tropical West Atlantic reveals for the first time the two-dimensional horizontal structure of an intense Internal Solitary Wave (ISW) field, whose first surface manifestations are detected several hundred kilometers away from the nearest forcing bathymetry. Composite maps and an energy budget analysis (provided from the Hybrid Coordinate Ocean Model – HYCOM) help to identify two major ISW pathways emanating from the steep slopes of a small promontory (or headland) near 44° W and 0° N, which are seen to extend for over 500 km into the open ocean. Further analysis in the SAR reveals propagation speeds above 3 m s−1, which are amongst the fastest ever recorded. ISWs main characteristics are further discussed based on a statistical analysis, and seasonal variability is found for one of the ISW sources. This seasonal variability is discussed in light of the North Equatorial Counter Current. The remote appearance of the ISW sea surface manifestations is explained by a late disintegration of the Internal Tide (IT), which is further investigated based on the SAR data and climatological monthly means (for stratification and currents). Acknowledging the possibility of a late disintegration of the IT may help explain the remote sensing views of other ISWs in the world's oceans.

scholarly journals Marine Reservoir Variation in the Bismarck Region: An Evaluation of Spatial and Temporal Change in ΔR and R Over the Last 3000 Years

Radiocarbon ◽  
2012 ◽  
Vol 54 (1) ◽  
pp. 45-58 ◽  
Author(s):  
Fiona Petchey ◽  
Sean Ulm
Keyword(s):  
Large Scale ◽  
Current System ◽  
Climatic Conditions ◽  
Ocean Eddies ◽  
North Equatorial Counter Current ◽  
Equatorial Current ◽  
Oceanographic Data ◽  
Counter Current ◽  
New Britain ◽  
Ekman Upwelling

Interactions between islands, ocean currents, and winds cause large-scale eddies and upwelling in the lee of islands that can result in spatial variation in the marine radiocarbon reservoir. For waters around New Ireland and the Bismarck Sea, ΔR values ranging from 365 to −320 14C yr have been reported (Kirch 2001; Petchey et al. 2004). Petchey et al. (2004) proposed that some of this variation was caused by seasonal reversals in the South Equatorial Current and North Equatorial Counter Current system, combined with Ekman upwelling from the Equator. McGregor et al. (2008) suggested additional complexity within this region caused by a change in the reservoir value over time in response to changing climatic conditions. We present a series of 14 new and extant published ΔR and R values on historic shells, combined with 8 values from archaeological terrestrial/marine pairs and U-Th dated coral, that support observations of localized variability caused by a complex interplay between seasonal currents, riverine input, and ocean eddies. On the basis of these values and oceanographic data, we divide the Bismarck Sea surface marine 14C reservoir into 6 tentative subregions. In particular, our results support significant variation within channels at the southwest and southeast ends of New Britain and towards the equatorial boundary of the sea. Our results indicate that within the Bismarck Sea geographical variation appears to be more extreme than temporal over the last 3000 yr.

scholarly journals Effect of the North Equatorial Counter Current on the generation and propagation of internal solitary waves off the Amazon shelf (SAR observations)

Ocean Science ◽  
2016 ◽  
Vol 12 (1) ◽  
pp. 243-255 ◽  
Author(s):  
J. M. Magalhaes ◽  
J. C. B. da Silva ◽  
M. C. Buijsman ◽  
C. A. E. Garcia
Keyword(s):  
Seasonal Variability ◽  
Internal Tide ◽  
Ocean Model ◽  
Horizontal Structure ◽  
The North ◽  
Budget Analysis ◽  
North Equatorial Counter Current ◽  
Amazon Shelf ◽  
Sar Imagery ◽  
Counter Current

Abstract. Synthetic aperture radar (SAR) imagery from the Amazon shelf break region in the tropical west Atlantic reveals for the first time the two-dimensional horizontal structure of an intense Internal Solitary Wave (ISW) field, whose first surface manifestations are detected several hundred kilometres away from the nearest forcing bathymetry. Composite maps and an energy budget analysis (provided from the Hybrid Coordinate Ocean Model – HYCOM) help to identify two major ISW pathways emanating from the steep slopes of a small promontory (or headland) near 44° W and 0° N, which are seen to extend for over 500 km into the open ocean. Further analysis in the SAR reveals propagation speeds above 3  m  s−1, which are amongst the fastest ever recorded. The main characteristics of the ISWs are further discussed based on a statistical analysis, and seasonal variability is found for one of the ISW sources. This seasonal variability is discussed in light of the North Equatorial Counter Current. The remote appearance of the ISW sea surface manifestations is explained by a late disintegration of the internal tide (IT), which is further investigated based on the SAR data and climatological monthly means (for stratification and currents). Acknowledging the possibility of a late disintegration of the IT may help explain the remote-sensing views of other ISWs in the world's oceans.

scholarly journals Potential Vorticity Dynamics of Tropical Instability Vortices

2014 ◽  
Vol 44 (3) ◽  
pp. 995-1011 ◽  
Author(s):  
Ryan M. Holmes ◽  
Leif N. Thomas ◽  
LuAnne Thompson ◽  
David Darr
Keyword(s):  
Potential Vorticity ◽  
Relative Vorticity ◽  
Equatorial Region ◽  
Equatorial Pacific ◽  
Vertical Shear ◽  
Coriolis Parameter ◽  
Equatorial Undercurrent ◽  
North Equatorial Counter Current ◽  
Lateral Mixing ◽  
Counter Current

Abstract Tropical instability vortices (TIVs) in the equatorial Pacific exhibit energetic horizontal and vertical circulation characterized by regions of high Rossby number and low Richardson number. Their strong anticyclonic vorticity and vertical shear can influence the broader-scale circulation by driving lateral mixing and vertical exchange between the ocean surface and interior. The authors use a set of nested high-resolution simulations of the equatorial Pacific, with a finest grid size of 3 km, to examine the vortex dynamics associated with TIV core water formation. TIV cores are characterized by low values of the Ertel potential vorticity (PV) as the relative vorticity is anticyclonic with magnitude comparable to the local Coriolis parameter. A study of the variation of PV and other scalars along Lagrangian fluid parcel tracks entering the TIVs shows that the low-PV water in their cores is a mix of Equatorial Undercurrent (EUC) water and North Equatorial Counter Current (NECC) water. The EUC water is characterized by strong horizontal vorticity, and thus, the baroclinic component of the PV is nonnegligible and acts as a source for the anticyclonic vorticity of TIVs. This horizontal vorticity is tilted by an ageostrophic secondary circulation associated with strain-induced frontogenesis that tends to form along the path of the EUC water that enters the vortex. Frontogenesis disrupts the cyclogeostrophic balance of the frontal flow and drives differential vertical motions across the front. These results emphasize the role of submesoscale physics in the equatorial region, which are active when both the Rossby and Richardson numbers are O(1).

scholarly journals On the role of the North Equatorial Counter Current during a strong El Niño

Ocean Science ◽  
2018 ◽  
Vol 14 (4) ◽  
pp. 633-660 ◽  
Author(s):  
David John Webb
Keyword(s):  
Ocean Model ◽  
Warm Water ◽  
Ekman Transport ◽  
Global Ocean ◽  
Instability Waves ◽  
Tropical Instability Waves ◽  
The North ◽  
The Pacific ◽  
North Equatorial Counter Current ◽  
Counter Current

Abstract. An analysis of archived data from the NEMO 1∕12th degree global ocean model shows the importance of the North Equatorial Counter Current (NECC) in the development of the strong 1982–1983 and 1997–1998 El Niños. The model results indicate that in a normal year the core of warm water in the NECC is diluted by the surface Ekman transport, by geostrophic inflow and by tropical instability waves. During the development of the 1982–1983 and 1997–1998 El Niños, these processes had reduced effect at the longitudes of warmest equatorial temperatures and to the west. During the autumns of 1982 and 1997, the speed of the NECC was also increased by a stronger-than-normal annual Rossby wave. The increased transport of warm water by the NECC due to these changes resulted in warm water reaching the far eastern Pacific and appears to have been a major factor in moving the centre of deep atmospheric convection eastwards across the Pacific.

scholarly journals The observed North Equatorial Counter Current in the far western Pacific Ocean during the 2014-2016 El Niño

2021 ◽  
Author(s):  
Hui Zhou ◽  
Hengchang Liu ◽  
Shuwen Tan ◽  
Wenlong Yang ◽  
Yao Li ◽  
...  
Keyword(s):  
Energy Source ◽  
Pacific Ocean ◽  
El Niño ◽  
El Nino ◽  
Western Pacific ◽  
Altimeter Data ◽  
Western Pacific Ocean ◽  
Mean Flow ◽  
North Equatorial Counter Current ◽  
Counter Current

AbstractThe structure and variations of the North Equatorial Counter Current (NECC) in the far western Pacific Ocean during 2014-2016 are investigated using repeated in-situ hydrographic data, altimeter data, Argo data, and reanalysis data. The NECC shifted ~1 degree southward and intensified significantly with its transport exceeding 40 Sv (1 Sv = 106 m3 s-1), nearly double its climatology value, during the developing phase of the 2015/16 El Niño event. Observations show that the 2015/16 El Niño exerted a comparable impact on the NECC with that of the extreme 1997/98 El Niño in the far western Pacific Ocean. Baroclinic instability provided the primary energy source for the eddy kinetic energy (EKE) in the 2015/16 El Niño, which differs from the traditional understanding of the energy source of EKE as barotropic instability in low latitude ocean. The enhanced vertical shear and the reduced density jump between the NECC layer and the subsurface North Equatorial Subsurface Current (NESC) layer renders the NECC–NESC system baroclinically unstable in the western Pacific Ocean during El Niño developing phase. The eddy-mean flow interactions here are diverse associated with various states of the El Niño Southern Oscillation (ENSO).

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