scholarly journals Spatial distribution of turbulent diapycnal mixing along the Mindanao current inferred from rapid-sampling Argo floats

2022 ◽  
Author(s):  
Ying He ◽  
Jianing Wang ◽  
Fan Wang ◽  
Toshiyuki Hibiya
Keyword(s):  
Turbulent Mixing ◽  
North Pacific ◽  
Water Mass ◽  
Strong Mixing ◽  
Western Boundary ◽  
Diapycnal Mixing ◽  
The North ◽  
Rapid Sampling ◽  
Mindanao Current ◽  
The North Pacific

AbstractThe Mindanao Current (MC) bridges the North Pacific low-latitude western boundary current system region and the Indonesian Seas by supplying the North Pacific waters to the Indonesian Throughflow. Although the previous study speculated that the diapycnal mixing along the MC might be strong on the basis of the water mass analysis of the gridded climatologic dataset, the real spatial distribution of diapycnal mixing along the MC has remained to be clarified. We tackle this question here by applying a finescale parameterization to temperature and salinity profiles obtained using two rapid-sampling profiling Argo floats that drifted along the MC. The western boundary (WB) region close to the Mindanao Islands and the Sangihe Strait are the two mixing hotspots along the MC, with energy dissipation rate ε and diapycnal diffusivity Kρ enhanced up to ~ 10–6 W kg−1 and ~ 10–3 m2 s−1, respectively. Except for the above two mixing hotspots, the turbulent mixing along the MC is mostly weak, with ε and Kρ to be 10–11–10–9 W kg−1 and 10–6–10–5 m2 s−1, respectively. Strong mixing in the Sangihe Strait can be basically attributed to the existence of internal tides, whereas strong mixing in the WB region suggests the existence of internal lee waves. We also find that water mass transformation along the MC mainly occurs in the Sangihe Strait where the water masses are subjected to strong turbulent mixing during a long residence time.

scholarly journals Interdecadal Baroclinic Sea Level Changes in the North Pacific Based on Historical Ocean Hydrographic Observations

2015 ◽  
Vol 28 (11) ◽  
pp. 4585-4594 ◽  
Author(s):  
Tatsuo Suzuki ◽  
Masayoshi Ishii
Keyword(s):  
Sea Level ◽  
Wind Stress ◽  
North Pacific ◽  
Water Mass ◽  
Mass Density ◽  
Baroclinic Mode ◽  
Sea Level Changes ◽  
The North ◽  
Basin Scale ◽  
The North Pacific

Abstract Using historical ocean hydrographic observations, decadal to multidecadal sea level changes from 1951 to 2007 in the North Pacific were investigated focusing on vertical density structures. Hydrographically, the sea level changes could reflect the following: changes in the depth of the main pycnocline, density gradient changes across the pycnocline, and modification of the water mass density structure within the pycnocline. The first two processes are characterized as the first baroclinic mode. The changes in density stratification across the pycnocline are sufficiently small to maintain the vertical profile of the first baroclinic mode in this analysis period. Therefore, the first mode should represent mainly the dynamical response to the wind stress forcing. Meanwhile, changes in the composite of all modes of order greater than 1 (remaining baroclinic mode) can be attributed to water mass modifications above the pycnocline. The first baroclinic mode is associated with 40–60-yr fluctuations in the subtropical gyre and bidecadal fluctuations of the Kuroshio Extension (KE) in response to basin-scale wind stress changes. In addition to this, the remaining baroclinic mode exhibits strong variability around the recirculation region south of the KE and regions downstream of the KE, accompanied by 40–60-yr and bidecadal fluctuations, respectively. These fluctuations follow spinup/spindown of the subtropical gyre and meridional shifts of the KE shown in the first mode, respectively. A lag correlation analysis suggests that interdecadal sea level changes due to water mass density changes are a secondary consequence of changes in basin-scale wind stress forcing related to the ocean circulation changes associated with the first mode.

scholarly journals On the Relationship between Synoptic Wintertime Atmospheric Variability and Path Shifts in the Gulf Stream and the Kuroshio Extension

2009 ◽  
Vol 22 (12) ◽  
pp. 3177-3192 ◽  
Author(s):  
Terrence M. Joyce ◽  
Young-Oh Kwon ◽  
Lisan Yu
Keyword(s):  
North Atlantic ◽  
North Pacific ◽  
Gulf Stream ◽  
Kuroshio Extension ◽  
Storm Track ◽  
Western Boundary ◽  
Atmospheric Variability ◽  
The North ◽  
The Kuroshio ◽  
The North Pacific

Abstract Coherent, large-scale shifts in the paths of the Gulf Stream (GS) and the Kuroshio Extension (KE) occur on interannual to decadal time scales. Attention has usually been drawn to causes for these shifts in the overlying atmosphere, with some built-in delay of up to a few years resulting from propagation of wind-forced variability within the ocean. However, these shifts in the latitudes of separated western boundary currents can cause substantial changes in SST, which may influence the synoptic atmospheric variability with little or no time delay. Various measures of wintertime atmospheric variability in the synoptic band (2–8 days) are examined using a relatively new dataset for air–sea exchange [Objectively Analyzed Air–Sea Fluxes (OAFlux)] and subsurface temperature indices of the Gulf Stream and Kuroshio path that are insulated from direct air–sea exchange, and therefore are preferable to SST. Significant changes are found in the atmospheric variability following changes in the paths of these currents, sometimes in a local fashion such as meridional shifts in measures of local storm tracks, and sometimes in nonlocal, broad regions coincident with and downstream of the oceanic forcing. Differences between the North Pacific (KE) and North Atlantic (GS) may be partly related to the more zonal orientation of the KE and the stronger SST signals of the GS, but could also be due to differences in mean storm-track characteristics over the North Pacific and North Atlantic.

scholarly journals Weak Thermocline Mixing in the North Pacific Low-Latitude Western Boundary Current System

2017 ◽  
Vol 44 (20) ◽  
pp. 10,530-10,539 ◽  
Author(s):  
Zhiyu Liu ◽  
Qiang Lian ◽  
Fangtao Zhang ◽  
Lei Wang ◽  
Mingming Li ◽  
...  
Keyword(s):  
North Pacific ◽  
Current System ◽  
Western Boundary Current ◽  
Western Boundary ◽  
Boundary Current ◽  
Low Latitude ◽  
The North ◽  
The North Pacific

Viscosity-Dependent Internal Variability in a Model of the North Pacific

2005 ◽  
Vol 35 (5) ◽  
pp. 747-756 ◽  
Author(s):  
Jordan T. Dawe ◽  
Lu Anne Thompson
Keyword(s):  
North Pacific ◽  
Time Scale ◽  
Flow Instability ◽  
North Pacific Ocean ◽  
Subtropical Gyre ◽  
Mode Analysis ◽  
Western Boundary ◽  
Driving Mechanism ◽  
The North ◽  
The North Pacific

Abstract A 2°-resolution isopycnal model of the North Pacific Ocean is shown to produce anomalies that propagate around the subtropical gyre on the decadal time scale that do not appear in a 1°-resolution version of the same model. A principal oscillation pattern (POP) analysis of the isopycnal interface anomaly is performed to examine the dynamics responsible for the anomaly generation. The POPs show a coherent oscillation around the entire subtropical gyre with two centers of action, one in the Central Mode Water (CMW) region, the other in the Subtropical Countercurrent (STCC). Lead–lag covariances between the subduction rate in the CMW and the layer thickness along the oscillation path indicate that anomalous subduction events are not the driving mechanism for the oscillation. A linearized quasigeostrophic mode analysis shows that the anomalies are generated by flow instability in the region of the STCC. The instability disappears in the 1° model because of changes in the horizontal viscosity, which is set in each model to the minimum value necessary to resolve the western boundary current and preserve numerical stability. A criterion for model resolution of an instability of a given length and time scale damped by biharmonic viscosity is derived. The enhancement of the large-scale instabilities in the low-resolution model emphasizes the importance of achieving mesoscale resolution in ocean models used for climate studies.

scholarly journals Pacific Abyssal Transport and Mixing: Through the Samoan Passage versus around the Manihiki Plateau

2019 ◽  
Vol 49 (6) ◽  
pp. 1577-1592 ◽  
Author(s):  
Larry J. Pratt ◽  
Gunnar Voet ◽  
Astrid Pacini ◽  
Shuwen Tan ◽  
Matthew H. Alford ◽  
...  
Keyword(s):  
North Pacific ◽  
Strong Mixing ◽  
Hydraulic Jumps ◽  
Bypass Flow ◽  
Frictional Drag ◽  
The North ◽  
Abyssal Circulation ◽  
Transport And Mixing ◽  
The North Pacific ◽  
Manihiki Plateau

AbstractThe main source feeding the abyssal circulation of the North Pacific is the deep, northward flow of 5–6 Sverdrups (Sv; 1 Sv ≡ 106 m3 s−1) through the Samoan Passage. A recent field campaign has shown that this flow is hydraulically controlled and that it experiences hydraulic jumps accompanied by strong mixing and dissipation concentrated near several deep sills. By our estimates, the diapycnal density flux associated with this mixing is considerably larger than the diapycnal flux across a typical isopycnal surface extending over the abyssal North Pacific. According to historical hydrographic observations, a second source of abyssal water for the North Pacific is 2.3–2.8 Sv of the dense flow that is diverted around the Manihiki Plateau to the east, bypassing the Samoan Passage. This bypass flow is not confined to a channel and is therefore less likely to experience the strong mixing that is associated with hydraulic transitions. The partitioning of flux between the two branches of the deep flow could therefore be relevant to the distribution of Pacific abyssal mixing. To gain insight into the factors that control the partitioning between these two branches, we develop an abyssal and equator-proximal extension of the “island rule.” Novel features include provisions for the presence of hydraulic jumps as well as identification of an appropriate integration circuit for an abyssal layer to the east of the island. Evaluation of the corresponding circulation integral leads to a prediction of 0.4–2.4 Sv of bypass flow. The circulation integral clearly identifies dissipation and frictional drag effects within the Samoan Passage as crucial elements in partitioning the flow.

Circulation and Heat Flux along the Western Boundary of the North Pacific

2019 ◽  
Vol 19 (1) ◽  
pp. 1-12
Author(s):  
Xia Ju ◽  
Chao Ma ◽  
Xuejun Xiong ◽  
Yanliang Guo ◽  
Long Yu
Keyword(s):  
Heat Flux ◽  
North Pacific ◽  
Western Boundary ◽  
The North ◽  
The North Pacific
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