scholarly journals Volume Transport Variability in the Western Equatorial Pacific and its Relations to Halmahera Throughflow

2021 ◽  
Vol 29 (2) ◽  
Author(s):  
Marlin Chrisye Wattimena ◽  
Agus Saleh Atmadipoera ◽  
Mulia Purba ◽  
I Wayan Nurjaya ◽  
Fadli Syamsudin
Keyword(s):  
General Circulation ◽  
Circulation Model ◽  
Ocean General Circulation Model ◽  
Volume Transport ◽  
Equatorial Pacific ◽  
Equatorial Pacific Ocean ◽  
Western Equatorial Pacific ◽  
North Equatorial Counter Current ◽  
Mindanao Current ◽  
Transport Volume

This study investigates the coherency of volume transport between Halmahera throughflow and current major system in the western equatorial Pacific Ocean (Mindanao Current – MC, New Guinea Coastal/Under Current – NGCC/NGCUC, and North Equatorial Counter Current – NECC). The validated daily ocean general circulation model datasets of INDESO (2010-2014) were used in this study. The results showed that the estimated average transport volume was 25.6 Sv flowing southward through MC, 34.5 Sv flowing eastward through NECC, 18.3 Sv flowing northwestward through NGCC/NGCUC, and 2.5 Sv flowing southward through the Halmahera Sea. The variability of volume transport was dominated by intraseasonal, semiannual, and annual time-scales. The increased transport of NECC corresponded to the intensification of MC and NGCC/NGCUC transports. NGCC/ NGCUC significantly controlled the South Pacific water inflow into the Halmahera Sea because of the positively high correlation between NGCC/NGCUC transport and Halmahera throughflow transport.

scholarly journals Argon as a Tracer of Cross-Isopycnal Mixing in the Thermocline

2006 ◽  
Vol 36 (11) ◽  
pp. 2090-2105 ◽  
Author(s):  
Cara C. Henning ◽  
David Archer ◽  
Inez Fung
Keyword(s):  
General Circulation Model ◽  
General Circulation ◽  
Vertical Mixing ◽  
Circulation Model ◽  
Ocean General Circulation Model ◽  
Global Ocean ◽  
Equatorial Pacific Ocean ◽  
Subsurface Waters ◽  
Different Temperatures ◽  
Ocean Gyre

Abstract Noble gases such as argon are unaffected by chemical reactions in the ocean interior, but a number of physical mechanisms can lead to measurable sea level atmospheric disequilibrium in subsurface waters of the ocean. One such mechanism is the mixing of waters of different temperatures, which can lead to supersaturation in the ocean interior. The authors simulate the supersaturation mixing signature in the thermocline in a global ocean general circulation model, Parallel Ocean Program model, version 1.4 (POP 1.4). In contrast to existing mixing diagnostics such as dye tracers or microstructure measurements, which yield the local, recent rate of diabatic mixing, argon disequilibrium traces an integrated lifetime history of subsurface mixing. A theoretical model of the subtropical Atlantic Ocean gyre is built, based on the competing time scales of horizontal and vertical mixing, that agrees well with the full general circulation model argon supersaturation gradient in the thermocline. These results suggest that gyre-scale argon data from the real ocean could be similarly interpreted. The variation of the argon supersaturation with diffusivity in the equatorial Pacific Ocean is also investigated.

scholarly journals Excitation of equatorial Kelvin and Yanai waves by tropical cyclones in an ocean general circulation model

2012 ◽  
Vol 3 (2) ◽  
pp. 999-1020
Author(s):  
R. L. Sriver ◽  
M. Huber ◽  
L. Chafik
Keyword(s):  
Tropical Cyclones ◽  
General Circulation ◽  
Circulation Model ◽  
Ocean Waves ◽  
Ocean General Circulation Model ◽  
Equatorial Pacific ◽  
Wind Forcing ◽  
Equatorial Ocean ◽  
Ocean General Circulation ◽  
The Tropical Pacific

Abstract. Tropical cyclones (TCs) actively contribute to the dynamics of Earth's coupled climate system. They influence oceanic mixing rates, upper-ocean heat content, and air-sea fluxes, with implications for atmosphere and ocean dynamics on multiple spatial and temporal scales. Using an ocean general circulation model with modified surface wind forcing, we explore how TC winds can excite equatorial ocean waves in the tropical Pacific. We highlight a situation where three successive TCs in the western North Pacific region, corresponding to events in 2003, excite a combination of Kelvin and Yanai waves in the equatorial Pacific. The resultant thermocline adjustment significantly modifies the thermal structure of the upper equatorial Pacific and leads to eastward zonal heat transport. Observations of upper-ocean temperature by the Tropical Atmosphere Ocean (TAO) buoy array and sea-level height anomalies using altimetry reveal wave passage during the same time period with similar properties to the modeled wave, although our idealized model methodology disallows precise identification of the TC forcing with the observed waves. Results indicate that direct oceanographic forcing by TCs may be important for understanding the spectrum of equatorial ocean waves, thus remotely influencing tropical mixing and surface energy budgets. Because equatorial Kelvin waves are closely linked to interannual variability in the tropical Pacific, these findings also suggest TC wind forcing may influence the timing and amplitude of El Niño events.

Recent Changes in the Pacific Subtropical Cells Inferred from an Eddy-Resolving Ocean Circulation Model*

2007 ◽  
Vol 37 (5) ◽  
pp. 1340-1356 ◽  
Author(s):  
Wei Cheng ◽  
Michael J. McPhaden ◽  
Dongxiao Zhang ◽  
E. Joseph Metzger
Keyword(s):  
Ocean Circulation ◽  
General Circulation ◽  
Control Volume ◽  
Circulation Model ◽  
Ocean General Circulation Model ◽  
Volume Transport ◽  
Western Boundary ◽  
Equatorial Undercurrent ◽  
Model Driven ◽  
The Pacific

Abstract In this study the subtropical cells (STC) in the Pacific Ocean are analyzed using an eddy-resolving ocean general circulation model driven by atmospheric forcing for the years 1992–2003. In particular, the authors seek to identify decadal changes in the STCs in the model and to compare them with observations in order to understand the consequences of such changes for the equatorial ocean heat and mass budgets. The simulation shows a trend toward increasing pycnocline volume transport at 9°N and 9°S across the basin from 1992 to 2003. This increase [4.9 ± 1.0 Sv (Sv ≡ 106 m3 s−1)] is in qualitative agreement with observations and is attributed primarily to changes in the interior ocean transport, which are partially compensated by opposing western boundary transports. The subtropical meridional volume transport convergence anomalies in the model pycnocline are found to be consistent with anomalous volume transports in both the observed and modeled Equatorial Undercurrent, as well as with the magnitude of simulated anomalous upwelling transport at the base of the mixed layer in the eastern Pacific. As a result of the increased circulation intensity, heat transport divergence through the lateral boundaries of the tropical control volume (defined as the region between 9°N and 9°S, and from the surface to σθ = 25.3 isopycnal) increases, leading to a cooling of the tropical upper ocean despite the fact that net surface heat flux into the control volume has increased in the same time. As such, these results suggest that wind-driven changes in ocean transports associated with the subtropical cells play a central role in regulating tropical Pacific climate variability on decadal time scales.

The Equatorial Pacific Cold Tongue Bias in a Coupled Climate Model

2008 ◽  
Vol 21 (22) ◽  
pp. 5852-5869 ◽  
Author(s):  
Vasubandhu Misra ◽  
L. Marx ◽  
M. Brunke ◽  
X. Zeng
Keyword(s):  
General Circulation ◽  
Low Frequency ◽  
Coupled Model ◽  
Circulation Model ◽  
Equatorial Pacific ◽  
Cold Tongue ◽  
Equatorial Pacific Ocean ◽  
Time Step ◽  
Coupling Interval ◽  
The Mean

Abstract A set of multidecadal coupled ocean–atmosphere model integrations are conducted with different time steps for coupling between the atmosphere and the ocean. It is shown that the mean state of the equatorial Pacific does not change in a statistically significant manner when the coupling interval between the atmospheric general circulation model (AGCM) and the ocean general circulation model (OGCM) is changed from 1 day to 2 or even 3 days. It is argued that because the coarse resolution of the AGCM precludes resolving realistic “weather” events, changing the coupling interval from 1 day to 2 or 3 days has very little impact on the mean coupled climate. On the other hand, reducing the coupling interval to 3 h had a much stronger impact on the mean state of the equatorial Pacific and the concomitant general circulation. A novel experiment that incorporates a (pseudo) interaction of the atmosphere with SST at every time step of the AGCM was also conducted. In this unique coupled model experiment, the AGCM at every time step mutually interacts with the skin SST. This skin SST is anchored to the bulk SST, which is updated from the OGCM once a day. Both of these experiments reduced the cold tongue bias moderately over the equatorial Pacific Ocean with a corresponding reduction in the easterly wind stress bias relative to the control integration. It is stressed from the results of these model experiments that the impact of high-frequency air–sea coupling is significant on the cold tongue bias. The interannual variation of the equatorial Pacific was less sensitive to the coupling time step between the AGCM and the OGCM. Increasing (reducing) the coupling interval of the air–sea interaction had the effect of weakening (marginally strengthening) the interannual variations of the equatorial Pacific Ocean. It is argued that the low-frequency response of the upper ocean, including the cold tongue bias, is modulated by the atmospheric stochastic forcing on the coupled ocean–atmosphere system. This effect of the atmospheric stochastic forcing is affected by the frequency of the air–sea coupling and is found to be stronger than the rectification effect of the diurnal variations of the air–sea interaction on the low frequency. This may be a result of a limitation in the coupled model used in this study in which the OGCM has an inadequate vertical resolution in the mixed layer to sustain diurnal variations in the upper ocean.

scholarly journals CHARACTERISTICS AND VARIABILITY OF THE FLORES ITF AND ITS COHERENCE WITH THE SOUTH JAVA COASTAL CURRENT

2018 ◽  
Vol 9 (2) ◽  
pp. 537-556 ◽  
Author(s):  
Agus S. Atmadipoera ◽  
Paradita Hasanah
Keyword(s):  
High Velocity ◽  
General Circulation ◽  
Circulation Model ◽  
Ocean General Circulation Model ◽  
Vertical Dimension ◽  
Coastal Current ◽  
Indonesian Throughflow ◽  
The South ◽  
Near Surface ◽  
Transport Volume

Characteristics and transport variability of the Indonesian Throughflow (ITF) in the western Flores Sea (FS) and its coherency with the South Java Coastal Current (SJCC) fluctuation are investigated using validated ocean general circulation model output (2008-2014) from the INDESO configuration.  The results show that near-surface circulation in the study area is characterized by two distinct regimes:  strong southwestward ITF flow and quasi-transient anti-cyclonic eddies. Vertical dimension of ITF crossing 7.5°S is about 112 km width, 250 m depth, and high velocity core at thermocline >0.3 m/s.  Transport volume estimates along this latitude is -4.95 Sv (southward).  Bifurcation of ITF flow appears north offshore Lombok Island where -2.92 Sv flowing into Lombok Strait and the rest flowing eastward into FS. Meanwhile, vertical dimension of SJCC crossing 114°E is about 89 km width, 120 m depth, and high velocity core at sub-surface >0.35 m/s. Mean transport of SJCC is +2.65 Sv. Coherency between Flores ITF and SJCC transport variability on intra-seasonal scales is significantly high, e.g., on 30 day period (coher=0.92) and phase-lags of 0.6-day with SJCC leading to Flores ITF. This result confirmed previous studies, related to intrusion of coastally trapped Kelvin waves into Flores Sea via Lombok Strait. Keywords: Indonesian Throughflow, western Flores Sea, South Java Coastal Current

Observations of the Mindanao Current during the western equatorial Pacific Ocean circulation study

1991 ◽  
Vol 96 (C4) ◽  
pp. 7089 ◽  
Author(s):  
Roger Lukas ◽  
Eric Firing ◽  
Peter Hacker ◽  
Philip L. Richardson ◽  
Curtis A. Collins ◽  
...  
Keyword(s):  
Pacific Ocean ◽  
Ocean Circulation ◽  
Equatorial Pacific ◽  
Equatorial Pacific Ocean ◽  
Western Equatorial Pacific ◽  
Mindanao Current

scholarly journals Seasonal Upwelling in the Northern Arafura Sea from Multi-datasets in 2017

2020 ◽  
Vol 28 (4) ◽  
Author(s):  
Agus Saleh Atmadipoera ◽  
Agits Agnia Almatin ◽  
Rina Zuraida ◽  
Yani Permanawati
Keyword(s):  
Mixed Layer ◽  
General Circulation ◽  
Standard Procedure ◽  
Subsurface Layer ◽  
Circulation Model ◽  
Ocean General Circulation Model ◽  
Surface Mixed Layer ◽  
Fisheries Resources ◽  
Arafura Sea ◽  
Transport Volume

Seasonal upwelling phenomenon in the Arafura Sea plays an important role on supplying upwelled nutrient-rich water to sustain biogeochemistry processes and thus contributes to high marine primary productivity and fisheries resources in this region. The objective of this research was to investigate physical process and dynamics of upwelling by analyzing stratification of seawater properties, evolution of surface ocean-atmosphere parameters, and current structure and transport volume in the northern Arafura Sea. The multi-datasets in 2017 were used in this study, acquired from field CTD measurement, satellite-derived sea surface parameters, and the ocean general circulation model outputs, which were processed and analyzed using the available standard procedure. It was found that upwelling event was associated with a sharp subsurface thin layer that upsloping isotherms (23.5 - 25.5°C), isohalines (33.50 - 34.25 psu), and isopycnals (21.8 - 23.2 kg/m³) from the shelf-break region to the inner shelf region at a distance of approximately 167 km. This barrier layer separated the first surface mixed layer from the second mixed layer beneath the subsurface layer. The model suggests that the current in these two layers is in the opposite direction, to the west in the first layer as a response to the Ekman drift and to the east in the second layer as a current extension from deep Aru basin. Therefore, upwelling dynamics here is not only generated by the southeasterly monsoon winds from May (onset) to November (termination) that transport warm and fresh surface water away from the shelf, but also modulated by the presence of strong inflow currents beneath subsurface that supply colder saltier nutrient-rich water into the shelf. During the upwelling period, mean transport volume in the upper 25 m depth between Aru and Papua at 134.25°E was -0.28 (±0.34) Sv (westward), but the transport volume between 25m and 110m depth was +1.06 (±0.29) Sv (eastward), suggesting this inflow may regulate the upwelling and supply Arafura shelf water.

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