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).

scholarly journals Seasonal Modulations of El Niño–Related Atmospheric Variability: Indo–Western Pacific Ocean Feedback

2017 ◽  
Vol 30 (9) ◽  
pp. 3461-3472 ◽  
Author(s):  
Shang-Ping Xie ◽  
Zhen-Qiang Zhou
Keyword(s):  
Pacific Ocean ◽  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
North Indian Ocean ◽  
Equatorial Pacific ◽  
Western Pacific ◽  
Northwest Pacific ◽  
Western Pacific Ocean ◽  
Combination Mode

The spatial structure of atmospheric anomalies associated with El Niño–Southern Oscillation varies with season because of the seasonal variations in sea surface temperature (SST) anomaly pattern and in the climatological basic state. The latter effect is demonstrated using an atmospheric model forced with a time-invariant pattern of El Niño warming over the equatorial Pacific. The seasonal modulation is most pronounced over the north Indian Ocean to northwest Pacific where the monsoonal winds vary from northeasterly in winter to southwesterly in summer. Specifically, the constant El Niño run captures the abrupt transition from a summer cyclonic to winter anticyclonic anomalous circulation over the northwest Pacific, in support of the combination mode idea that emphasizes nonlinear interactions of equatorial Pacific SST forcing and the climatological seasonal cycle. In post–El Niño summers when equatorial Pacific warming has dissipated, SST anomalies over the Indo–northwest Pacific Oceans dominate and anchor the coherent persisting anomalous anticyclonic circulation. A conceptual model is presented that incorporates the combination mode in the existing framework of regional Indo–western Pacific Ocean coupling.

scholarly journals Biophysical responses near equatorial islands in the Western Pacific Ocean during El Niño/La Niña transitions

2013 ◽  
Vol 40 (20) ◽  
pp. 5473-5479 ◽  
Author(s):  
Michelle M. Gierach ◽  
Monique Messié ◽  
Tong Lee ◽  
Kristopher B. Karnauskas ◽  
Marie-Hélène Radenac
Keyword(s):  
Pacific Ocean ◽  
El Niño ◽  
El Nino ◽  
La Niña ◽  
Western Pacific ◽  
Western Pacific Ocean ◽  
La Nina ◽  
The Western Pacific

scholarly journals Why Was the August Rainfall Pattern in the East Asia–Pacific Ocean Region in 2016 Different from That in 1998 under a Similar Preceding El Niño Background?

2019 ◽  
Vol 32 (18) ◽  
pp. 5785-5797 ◽  
Author(s):  
Dong Chen ◽  
Ya Gao ◽  
Huijun Wang
Keyword(s):  
Pacific Ocean ◽  
El Niño ◽  
El Nino ◽  
Southern China ◽  
Western Pacific ◽  
Asia Pacific ◽  
Western Pacific Ocean ◽  
El Niño Event ◽  
Ocean Region ◽  
The Western Pacific

AbstractPrevious studies have noted that a strong El Niño event occurring in the preceding winter will result in westward stretching of the western North Pacific subtropical high (WPSH) in the following summer, causing anomalously high precipitation in the Yangtze–Huaihe River basin and anomalously low precipitation in southern China. The winters preceding the summers of 1998 and 2016 featured strong El Niño events, which, along with the El Niño event of 1982, represented the strongest El Niño events since 1950. Under these similar El Niño event backgrounds, the July precipitation anomaly in 2016 was similar to that in 1998, but the August precipitation anomalies in the two years featured opposite distributions. According to the atmospheric circulation analysis, we found that an anomalous ascending motion appeared over the Indian Ocean, while an anomalous descending motion appeared over the Pacific Ocean in August 1998. In addition, the WPSH stretched westward over southern China. However, the atmospheric circulation distribution in August 2016 was the opposite of that in 1998, and the WPSH was divided into eastern and western parts by the anomalous western Pacific cyclone. Further analysis showed that the number of tropical cyclones and typhoons over the western Pacific Ocean increased significantly in August 2016, and their activities were concentrated in the South China Sea (SCS)–southern China region and the western Pacific Ocean, resulting in the division of the WPSH. Therefore, the numbers, tracks, and strengths of tropical cyclones and typhoons were responsible for the differences in the anomalous precipitation distributions over the East Asia–Pacific Ocean region between August 2016 and August 1998.

scholarly journals Differences in the Reaction of North Equatorial Countercurrent to the Developing and Mature Phase of ENSO Events in the Western Pacific Ocean

Climate ◽  
2021 ◽  
Vol 9 (4) ◽  
pp. 57
Author(s):  
Yusuf Jati Wijaya ◽  
Yukiharu Hisaki
Keyword(s):  
Pacific Ocean ◽  
El Niño ◽  
El Nino ◽  
Enso Event ◽  
Western Pacific ◽  
Western Pacific Ocean ◽  
Mature Phase ◽  
La Nina ◽  
La Nina Event ◽  
The Western Pacific

The North Equatorial Countercurrent (NECC) is an eastward zonal current closely related to an El Niño Southern Oscillation (ENSO) event. This paper investigated the variations of NECC in the Western Pacific Ocean over 25 years (1993–2017) using satellite data provided by the Copernicus Marine Environment Monitoring Service (CMEMS) and the Remote Sensing System (RSS). The first mode of empirical orthogonal function (EOF) analysis showed that the NECC strengthened or weakened in each El Niño (La Niña) event during the developing or mature phase, respectively. We also found that the NECC shifting was strongly coincidental with an ENSO event. During the developing phase of an El Niño (La Niña) event, the NECC shifted southward (northward), and afterward, when it entered the mature phase, the NECC tended to shift slightly northward (southward). Moreover, the NECC strength was found to have undergone a weakening during the 2008–2017 period.

scholarly journals Changes in Sea Salt Emissions Enhance ENSO Variability

2016 ◽  
Vol 29 (23) ◽  
pp. 8575-8588 ◽  
Author(s):  
Yang Yang ◽  
Lynn M. Russell ◽  
Sijia Lou ◽  
Maryam A. Lamjiri ◽  
Ying Liu ◽  
...  
Keyword(s):  
Pacific Ocean ◽  
El Niño ◽  
El Nino ◽  
Sea Salt ◽  
La Niña ◽  
Western Pacific ◽  
Interannual Variations ◽  
Enso Variability ◽  
La Nina ◽  
The Tropical Pacific

Abstract Two 150-yr preindustrial simulations with and without interactive sea salt emissions from the Community Earth System Model (CESM) are performed to quantify the interactions between sea salt emissions and El Niño–Southern Oscillation (ENSO). Variations in sea salt emissions over the tropical Pacific Ocean are affected by changing wind speed associated with ENSO variability. ENSO-induced interannual variations in sea salt emissions result in decreasing (increasing) aerosol optical depth (AOD) by 0.03 over the equatorial central-eastern (western) Pacific Ocean during El Niño events compared to those during La Niña events. These changes in AOD further increase (decrease) radiative fluxes into the atmosphere by +0.2 (−0.4) W m−2 over the tropical eastern (western) Pacific. Thereby, sea surface temperature increases (decreases) by 0.2–0.4 K over the tropical eastern (western) Pacific Ocean during El Niño compared to La Niña events and enhances ENSO variability by 10%. The increase in ENSO amplitude is a result of systematic heating (cooling) during the warm (cold) phase of ENSO in the eastern Pacific. Interannual variations in sea salt emissions then produce the anomalous ascent (subsidence) over the equatorial eastern (western) Pacific between El Niño and La Niña events, which is a result of heating anomalies. Owing to variations in sea salt emissions, the convective precipitation is enhanced by 0.6–1.2 mm day−1 over the tropical central-eastern Pacific Ocean and weakened by 0.9–1.5 mm day−1 over the Maritime Continent during El Niño compared to La Niña events, enhancing the precipitation variability over the tropical Pacific.

scholarly journals Effects of Ocean Currents in the Western Pacific Ocean on Net-Phytoplankton Community Compositions

Diversity ◽  
2021 ◽  
Vol 13 (9) ◽  
pp. 428
Author(s):  
Zhuo Chen ◽  
Jun Sun ◽  
Dawei Chen ◽  
Shihao Wang ◽  
Hao Yu ◽  
...  
Keyword(s):  
Pacific Ocean ◽  
Phytoplankton Community ◽  
Ocean Currents ◽  
Western Pacific ◽  
Coastal Current ◽  
Western Pacific Ocean ◽  
Phytoplankton Communities ◽  
Nitrite Nitrate ◽  
Counter Current ◽  
The Western Pacific

Phytoplankton are known as important harbingers of climate change in aquatic ecosystems. This study investigated phytoplankton community structure in the western Pacific Ocean (WPO) in 2017 and revealed the spatial variability of phytoplankton in community composition and abundance, as well as their relationship to physical processes and environmental factors. The phytoplankton community was mainly composed of Dinophyta (221), followed by Bacillariophyta (105), Cyanophyta (4), and Chrysophyta (2). The cyanobacteria Trichodesmium were the dominants throughout the study period. Correlation analysis showed that dinoflagellates were mainly affected by temperature, while diatoms were significantly correlated with nutrients (silicate, phosphate, nitrite, nitrate). Phytoplankton was divided into five groups by cluster analysis, and the distribution of different groups was related to circulation and hydrological characteristics. In contrast, the highest abundance of diatoms and dinoflagellates was found in the New Guinea Coastal Current (NGCC) region, while the highest abundance of cyanobacteria was found in the Northern Equatorial Counter Current (NECC) region. Overall, we found that not only temperature and salinity, but also ocean currents and nutrients, influence the distribution of phytoplankton communities in the WPO.

scholarly journals Spatiotemporal Variability of Remote Sensing Ocean Net Primary Production and Major Forcing Factors in the Tropical Eastern Indian and Western Pacific Ocean

2019 ◽  
Vol 11 (4) ◽  
pp. 391 ◽  
Author(s):  
Fanping Kong ◽  
Qing Dong ◽  
Kunsheng Xiang ◽  
Zi Yin ◽  
Yanyan Li ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Pacific Ocean ◽  
Indian Ocean ◽  
Primary Production ◽  
El Nino ◽  
Net Primary Production ◽  
Western Pacific ◽  
Sea Surface ◽  
Spatiotemporal Variability ◽  
Western Pacific Ocean

Based on widely used remote sensing ocean net primary production (NPP) datasets, the spatiotemporal variability of NPP is first analyzed over the tropical eastern Indian and western Pacific Ocean for the period 1998–2016 using the conventional empirical orthogonal function (EOF), the lead–lag correlation and the ensemble empirical mode decomposition (EEMD) technique. Barnett and Preisendorfer’s improved Canonical Correlation Analysis (BPCCA) is also applied to derive covariability patterns of NPP with major forcing factors of the chlorophyll a concentration (Chla), sea surface temperature (SST), sea level anomaly (SLA), ocean rainfall (Rain), sea surface wind (Wind), and current (CUR) under climate changes of El Niño–Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD). We find that: (1) The first two seasonal EOF modes capture significant temporal and meridional NPP variability differences, as NPP reaches peaks approximately three months later in the western Pacific Ocean than that of in the eastern Indian Ocean. (2) The second and third interannual EOF modes are closely related with ENSO with a two-month lag and synchronous with IOD, respectively, characterized by southwesterly positive anomaly centers during positive IOD years. (3) NPP presents different varying tendencies and similar multiscale oscillation patterns with interannual and interdecadal cycles of 2~3 years, 5~8 years, and 9~19 years in subregions of the Bay of Bengal, the South China Sea, the southeastern Indian Ocean, and the northwestern Pacific Ocean. (4) The NPP variability is strongly coupled with negative SST, SLA, and Rain anomalies, as well as positive Chla, Wind and CUR anomalies in general during El Niño/positive IOD years. The results reveal the diversity and complexity of large-scale biophysical interactions in the key Indo-Pacific Warm Pool region, which improves our understanding of ocean productivity, ecosystems, and carbon budgets.

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