scholarly journals Multidecadal Sea Level and Gyre Circulation Variability in the Northwestern Tropical Pacific Ocean

2012 ◽  
Vol 42 (1) ◽  
pp. 193-206 ◽  
Author(s):  
Bo Qiu ◽  
Shuiming Chen
Keyword(s):  
Pacific Ocean ◽  
Sea Level Rise ◽  
Sea Level ◽  
Model Simulation ◽  
Surface Wind ◽  
Tropical Pacific ◽  
North Equatorial Current ◽  
Altimeter Data ◽  
Upper Ocean ◽  
Tropical Pacific Ocean

Abstract Sea level rise with the trend >10 mm yr−1 has been observed in the tropical western Pacific Ocean over the 1993–2009 period. This rate is 3 times faster than the global-mean value of the sea level rise. Analyses of the satellite altimeter data and repeat hydrographic data along 137°E reveal that this regionally enhanced sea level rise is thermosteric in nature and vertically confined to a patch in the upper ocean above the 12°C isotherm. Dynamically, this regional sea level trend is accompanied by southward migration and strengthening of the North Equatorial Current (NEC) and North Equatorial Countercurrent (NECC). Using a 1½-layer reduced-gravity model forced by the ECMWF reanalysis wind stress data, the authors find that both the observed sea level rise and the NEC/NECC’s southward migrating and strengthening trends are largely attributable to the upper-ocean water mass redistribution caused by the surface wind stresses of the recently strengthened atmospheric Walker circulation. Based on the long-term model simulation, it is further found that the observed southward migrating and strengthening trends of the NEC and NECC began in the early 1990s. In the two decades prior to 1993, the NEC and NECC had weakened and migrated northward in response to a decrease in the trade winds across the tropical Pacific Ocean.

scholarly journals Impacts of the Indian Ocean Dipole on Sea Level and Gyre Circulation of the Western Tropical Pacific Ocean

2020 ◽  
Vol 33 (10) ◽  
pp. 4207-4228 ◽  
Author(s):  
Jing Duan ◽  
Yuanlong Li ◽  
Lei Zhang ◽  
Fan Wang
Keyword(s):  
Pacific Ocean ◽  
Indian Ocean ◽  
Sea Level ◽  
Indian Ocean Dipole ◽  
Tropical Pacific ◽  
Upper Ocean ◽  
Tropical Pacific Ocean ◽  
Western Tropical Pacific ◽  
The Indian Ocean ◽  
Gyre Circulation

AbstractInterannual variabilities of sea level and upper-ocean gyre circulation of the western tropical Pacific Ocean (WTPO) have been predominantly attributed to El Niño–Southern Oscillation (ENSO). The results of the present study put forward important modulation effects by the Indian Ocean dipole (IOD) mode. The observed sea level in the WTPO shows significant instantaneous and lagged correlations (around −0.60 and 0.40, respectively) with the IOD mode index (DMI). A composite of 14 “independent” IOD events for 1958–2017 shows negative sea level anomalies (SLAs) of 4–7 cm in the WTPO during positive IOD events and positive SLAs of 6–8 cm in the following year that are opposite in sign to the El Niño effect. The IOD impacts are reproduced by large-ensemble simulations of a climate model that generate respectively 430 and 519 positive and negative independent IOD events. A positive IOD induces westerly winds over the western and central tropical Pacific and causes negative SLAs through Ekman upwelling, and it facilitates the establishment of a La Niña condition in the following year that involves enhanced Pacific trade winds and causes positive SLAs in the WTPO. Ocean model experiments confirm that the IOD affects the WTPO sea level mainly through modulating the tropical Pacific winds. Variability of the Indonesian Throughflow (ITF) induced by IOD winds has a relatively weak effect on the WTPO. The IOD’s impacts on the major upper-ocean currents are also considerable, causing anomalies of 1–4 Sv (1 Sv ≡ 106 m3 s−1) in the South Equatorial Current (SEC) and North Equatorial Countercurrent (NECC) volume transports.

Anomalous transport of heat and salt by a long-lived anticyclonic eddy  in the northeast tropical Pacific Ocean

2021 ◽  
Author(s):  
Kaveh Purkiani ◽  
Maren Walter ◽  
Matthias Haeckel ◽  
Katja Schmidt ◽  
André Paul ◽  
...  
Keyword(s):  
Pacific Ocean ◽  
Dissolved Oxygen ◽  
Mesoscale Eddy ◽  
Tropical Pacific ◽  
Anticyclonic Eddy ◽  
Altimeter Data ◽  
Positive Temperature ◽  
Tropical Pacific Ocean ◽  
High Rotational Speed ◽  
The Impact

<p><span>During RV Sonne expedition SO268 to the northeast tropical Pacific Ocean between March and May 2019, the impact of a mesoscale eddy on the seawater properties was investigated by conducting a multiple of observations. A subsequent analysis of an altimeter data revealed the formation of an anticyclonic mesoscale eddy in the Tehuantepec gulf between 15 and 20 June 2018 with a mean radius of 185 km and an average speed of 13 cm/s. This extremely long-lived eddy carried sea-water characteristics from near coastal Mexican waters westward far into the open ocean. The water mass stayed largely isolated during the 11 months of travel time due to high rotational speed.</span></p><p><span>The eddy exhibited a conical-shape vertical structure with concurrent deepening of the main thermocline. The water in the eddy core showed an extreme positive temperature anomaly of 8</span><sup><span>◦</span></sup><span>C, a negative salinity anomaly of -0.5 psu and a positive dissolved oxygen concentration anomaly of +160 μmol/kg centered at 80 m depth. The sub-surface impact of the eddy is clearly evident in the temperature and salinity profiles at a depth of 1500 m. For dissolved oxygen the eddy-induced anomaly reached even deeper to the seafloor.</span></p><p><span>This study provides new insights to the offshore transport of heat and salt driven by the long-lived anticyclonic eddy in the northeast tropical Pacific Ocean. Considering the water column trapped within the eddy, a positive heat transport anomaly of 1-3 ×10</span><sup><span>11</span></sup><span> W and a negative salt transport anomaly of -8×10</span><sup><span>3</span></sup><span> kg/s were estimated. However, due to the rare occurrence of long-lived anticyclone eddies in this region, they likely do not play a significant role in affecting the heat and salt balance of the northeastern tropical Pacific Ocean. </span></p>

The three-dimensional structure of an upper ocean vortex in the tropical Pacific Ocean

Nature ◽  
1996 ◽  
Vol 383 (6601) ◽  
pp. 610-613 ◽  
Author(s):  
Pierre J. Flament ◽  
Sean C. Kennan ◽  
Robert A. Knox ◽  
Pearn P. Niiler ◽  
Robert L. Bernstein
Keyword(s):  
Pacific Ocean ◽  
Three Dimensional ◽  
Tropical Pacific ◽  
Dimensional Structure ◽  
Upper Ocean ◽  
Tropical Pacific Ocean ◽  
Three Dimensional Structure ◽  
The Tropical Pacific

Intraseasonal Variability of the Surface Zonal Currents in the Western Tropical Pacific Ocean: Characteristics and Mechanisms

2016 ◽  
Vol 46 (12) ◽  
pp. 3639-3660 ◽  
Author(s):  
Fan Wang ◽  
Yuanlong Li ◽  
Jianing Wang
Keyword(s):  
Pacific Ocean ◽  
Ocean Circulation ◽  
General Circulation ◽  
Intraseasonal Variability ◽  
Circulation Model ◽  
Tropical Pacific ◽  
North Equatorial Current ◽  
Tropical Pacific Ocean ◽  
Western Tropical Pacific ◽  
Equatorial Current

AbstractThe surface circulation of the tropical Pacific Ocean is characterized by alternating zonal currents, such as the North Equatorial Current (NEC), North Equatorial Countercurrent (NECC), South Equatorial Current (SEC), and South Equatorial Countercurrent (SECC). In situ measurements of subsurface moorings and satellite observations reveal pronounced intraseasonal variability (ISV; 20–90 days) of these zonal currents in the western tropical Pacific Ocean (WTPO). The amplitude of ISV is the largest within the equatorial band exceeding 20 cm s−1 and decreases to ~10 cm s−1 in the NECC band and further to 4–8 cm s−1 in the NEC and SECC. The ISV power generally increases from high frequencies to low frequencies and exhibits a peak at 50–60 days in the NECC, SEC, and SECC. These variations are faithfully reproduced by an ocean general circulation model (OGCM) forced by satellite winds, and parallel model experiments are performed to gain insights into the underlying mechanisms. It is found that large-scale ISV (>500 km) is primarily caused by atmospheric intraseasonal oscillations (ISOs), such as the Madden–Julian oscillation (MJO), through wind stress forcing. These signals are confined within 10°S–8°N, mainly as baroclinic ocean wave responses to ISO winds. For scales shorter than 200 km, ISV is dominated by ocean internal variabilities with mesoscale structures. They arise from the baroclinic and barotropic instabilities associated with the vertical and horizontal shears of the upper-ocean circulation. The ISV exhibits evident seasonal variation, with larger (smaller) amplitude in boreal winter (summer) in the SEC and SECC.

The unexpected salinity trend shifts in upper Tropical Pacific Ocean under the global hydrological cycle framework

2021 ◽  
Author(s):  
Huangyuan Shi ◽  
Ling Du
Keyword(s):  
Global Warming ◽  
Pacific Ocean ◽  
Water Cycle ◽  
Tropical Pacific ◽  
Secular Change ◽  
Upper Ocean ◽  
Tropical Pacific Ocean ◽  
Surface Salinity ◽  
Ocean Salinity ◽  
The Impact

<p>The secular change of ocean salinity is regarded as an indicator of the global water cycle by measuring the surface freshwater flux which is the most important component of earth hydrological budget. Under the effect of remarkable global warming, the surface salinity patterns in ocean basins illustrated that the intensified water cycle resulted in the continuous and significant freshening phenomena in tropical ocean. With the recent boom in salinity measurements and observations, the variability of surface salinity was examined to explore its relationship with anthropogenic warming. In this paper, we found that the salinity varied on the decadal to centurial time scales and responded significantly to the global warming in tropical Pacific Ocean by using the multi-source reanalysis datasets. An unexpected distribution was figured out and what is noteworthy is that, the robust salinification occurred in the central tropic Pacific in the first two decades of 21<sup>st</sup> which was demonstrated by Argo observations. Nevertheless, it did not follow the typical salinity patterns that ‘wet get wetter’ mentioned by several literatures and illustrated a significant trend shift. Similarly, the subsurface ocean salinity revealed the same shift but an opposite tendency to that on surface. It may involve that the controlling influence of surface freshwater reduced and the impact of ocean thermodynamic adjustment became gradually pronounced to the upper ocean. The salinity budget suggested that salinity advection and subsurface entrainment played key roles to induce the reversed trend of salinity change. In addition, the isopycnals variability caused by wind-driven ocean pumping and subtropical gyre may be acted as a trigger of the salinity enhancement in the upper ocean. What’s more, the impact of PDO decadal shift and the moderate global warming was seemed to be the essential factors to change the feedback of ocean-atmosphere processes, potentially and was finally reflected on ocean salinity field.</p>

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