scholarly journals Glider Observations of a Mesoscale Oceanic Island Wake

2019 ◽  
Vol 49 (9) ◽  
pp. 2217-2235 ◽  
Author(s):  
Kristin L. Zeiden ◽  
Daniel L. Rudnick ◽  
Jennifer A. MacKinnon
Keyword(s):  
Time Series ◽  
North Pacific Ocean ◽  
Boundary Layer Separation ◽  
North Equatorial Current ◽  
Return Flow ◽  
First Order ◽  
Large Island ◽  
Equatorial Current ◽  
Instantaneous Values ◽  
Island Wake

AbstractIn this study, a 2-yr time series of velocity profiles to 1000 m from meridional glider surveys is used to characterize the wake in the lee of a large island in the western tropical North Pacific Ocean, Palau. Surveys were completed along sections to the east and west of the island to capture both upstream and downstream conditions. Objectively mapped in time and space, mean sections of velocity show the incident westward North Equatorial Current accelerating around the island of Palau, increasing from 0.1 to 0.2 m s−1 at the surface. Downstream of the island, elevated velocity variability and return flow in the lee are indicative of boundary layer separation. Isolating for periods of depth-average westward flow reveals a length scale in the wake that reflects local details of the topography. Eastward flow is shown to produce an asymmetric wake. Depth-average velocity time series indicate that energetic events (on time scales from weeks to months) are prevalent. These events are associated with mean vorticity values in the wake up to 0.3f near the surface and with instantaneous values that can exceed f (the local Coriolis frequency) during periods of sustained, anomalously strong westward flow. Thus, ageostrophic effects become important to first order.

Spawning time and place of the Japanese eel Anguilla japonica in the North Equatorial Current of the western North Pacific Ocean

2001 ◽  
Vol 67 (6) ◽  
pp. 1097-1103 ◽  
Author(s):  
Satoshi Ishikawa, ◽  
Kunihiro Suzuki, ◽  
Tadashi Inagaki, ◽  
Shun Watanabe, ◽  
Yobuo Kimura, ◽  
...  
Keyword(s):  
Pacific Ocean ◽  
North Pacific ◽  
Western North Pacific ◽  
North Pacific Ocean ◽  
Anguilla Japonica ◽  
Japanese Eel ◽  
North Equatorial Current ◽  
The North ◽  
Spawning Time ◽  
Equatorial Current

scholarly journals Interannual-to-Decadal Variability in the Bifurcation of the North Equatorial Current off the Philippines

2010 ◽  
Vol 40 (11) ◽  
pp. 2525-2538 ◽  
Author(s):  
Bo Qiu ◽  
Shuiming Chen
Keyword(s):  
Wind Stress ◽  
Decadal Variability ◽  
North Pacific Ocean ◽  
The Philippines ◽  
Wind Forcing ◽  
North Equatorial Current ◽  
The North ◽  
Equatorial Current ◽  
Nec Bifurcation

Abstract Satellite altimeter sea surface height (SSH) data from the past 17 yr are used to investigate the interannual-to-decadal changes in the bifurcation of the North Equatorial Current (NEC) along the Philippine coast. The NEC bifurcation latitude migrated quasi decadally between 10° and 15°N with northerly bifurcations observed in late 1992, 1997–98, and 2003–04 and southerly bifurcations in 1999–2000 and 2008–09. The observed NEC bifurcation latitude can be approximated well by the SSH anomalies in the 12°–14°N and 127°–130°E box east of the mean NEC bifurcation point. Using a 1 ½-layer reduced-gravity model forced by the ECMWF reanalysis wind stress data, the authors find that the SSH anomalies in this box can be simulated favorably to serve as a proxy for the observed NEC bifurcation. With the availability of the long-term reanalysis wind stress data, this helps to lengthen the NEC bifurcation time series back to 1962. Although quasi-decadal variability was prominent in the last two decades, the NEC bifurcation was dominated by changes with a 3–5-yr period during the 1980s and had low variance prior to the 1970s. These interdecadal modulations in the characteristics of the NEC bifurcation reflect similar interdecadal modulations in the wind forcing field over the western tropical North Pacific Ocean. Although the NEC bifurcation on interannual and longer time scales is generally related to the Niño-3.4 index with a positive (negative) index corresponding to a northerly (southerly) bifurcation, the exact location of bifurcation is determined by wind forcing in the 12°–14°N band that contains variability not fully representable by the Niño-3.4 index.

scholarly journals Trends of the Pathways and Intensities of Surface Equatorial Current System in the North Pacific Ocean

2016 ◽  
Vol 29 (18) ◽  
pp. 6693-6710 ◽  
Author(s):  
Yi-Chia Hsin
Keyword(s):  
Pacific Ocean ◽  
North Pacific ◽  
North Pacific Ocean ◽  
Current System ◽  
North Equatorial Current ◽  
Ocean Reanalysis ◽  
The North ◽  
Equatorial Current ◽  
The North Pacific

Abstract An ensemble of ocean reanalysis products is utilized to quantify the long-term tendencies of pathways and along-pathway transports of the three surface equatorial currents (North Equatorial Current, North Equatorial Countercurrent, and northern branch of the South Equatorial Current) in the North Pacific Ocean during the period of the 1900s–2000s. This study uses 12 ocean reanalysis products in the ensemble for the period after the 1960s, while only 2 Simple Ocean Data Assimilation (SODA) products are taken into consideration for the period prior to 1960s. The analyses indicate that the three currents in the western (eastern) Pacific Ocean have more southern (northern) mean central positions and tend to move southward (northward) over the past 100 years. All three currents have weakening tendencies, with the exception of the North Equatorial Current having intensified in the western Pacific Ocean. The Sverdrup dynamics, which directly relates the wind-driven circulation in the interior ocean to wind stress curl and Earth rotation, can be applied to simply address the long-term changes of intensities and pathways of the three surface currents in the tropical North Pacific Ocean.

scholarly journals Empirical Insights from a Study on Outlier Preserving Value Generalization in Animated Choropleth Maps

2021 ◽  
Vol 10 (4) ◽  
pp. 208
Author(s):  
Christoph Traun ◽  
Manuela Larissa Schreyer ◽  
Gudrun Wallentin
Keyword(s):  
Time Series ◽  
Empirical Research ◽  
Global Trends ◽  
First Order ◽  
Choropleth Maps ◽  
Temporal Generalization ◽  
Perceptual Limits ◽  
Local Outlier

Time series animation of choropleth maps easily exceeds our perceptual limits. In this empirical research, we investigate the effect of local outlier preserving value generalization of animated choropleth maps on the ability to detect general trends and local deviations thereof. Comparing generalization in space, in time, and in a combination of both dimensions, value smoothing based on a first order spatial neighborhood facilitated the detection of local outliers best, followed by the spatiotemporal and temporal generalization variants. We did not find any evidence that value generalization helps in detecting global trends.

Seasonal variability of the bifurcation of the North Equatorial Current

2013 ◽  
Vol 25 (4) ◽  
pp. 550-555 ◽  
Author(s):  
Qiang-chang Ju ◽  
Song Jiang ◽  
Ji-wei Tian ◽  
Ling-hai Kong ◽  
Guo-xi Ni
Keyword(s):  
Seasonal Variability ◽  
North Equatorial Current ◽  
The North ◽  
Equatorial Current
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