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.

scholarly journals Tropical Atlantic Mixed Layer Buoyancy Seasonality: Atmospheric and Oceanic Physical Processes Contributions

Atmosphere ◽  
2020 ◽  
Vol 11 (6) ◽  
pp. 649
Author(s):  
Ibrahima Camara ◽  
Juliette Mignot ◽  
Nicolas Kolodziejczyk ◽  
Teresa Losada ◽  
Alban Lazar
Keyword(s):  
Heat Flux ◽  
Mixed Layer ◽  
General Circulation ◽  
Circulation Model ◽  
Ocean General Circulation Model ◽  
Brazilian Coast ◽  
Freshwater Flux ◽  
Physical Processes ◽  
Inter Tropical Convergence Zone ◽  
Near Surface

This study investigates the physical processes controlling the mixed layer buoyancy using a regional configuration of an ocean general circulation model. Processes are quantified by using a linearized equation of state, a mixed-layer heat, and a salt budget. Model results correctly reproduce the observed seasonal near-surface density tendencies. The results indicate that the heat flux is located poleward of 10° of latitude, which is at least three times greater than the freshwater flux that mainly controls mixed layer buoyancy. During boreal spring-summer of each hemisphere, the freshwater flux partly compensates the heat flux in terms of buoyancy loss while, during the fall-winter, they act together. Under the seasonal march of the Inter-tropical Convergence Zone and in coastal areas affected by the river, the contribution of ocean processes on the upper density becomes important. Along the north Brazilian coast and the Gulf of Guinea, horizontal and vertical processes involving salinity are the main contributors to an upper water change with a contribution of at least twice as much the temperature. At the equator and along the Senegal-Mauritanian coast, vertical processes are the major oceanic contributors. This is mainly due to the vertical gradient of temperature at the mixed layer base in the equator while the salinity one dominates along the Senegal-Mauritania coast.

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 The Total Energy Flux Leaving the Ocean’s Mixed Layer

2016 ◽  
Vol 46 (6) ◽  
pp. 1885-1900 ◽  
Author(s):  
Antonija Rimac ◽  
Jin-Song von Storch ◽  
Carsten Eden
Keyword(s):  
Total Energy ◽  
Wind Stress ◽  
Energy Flux ◽  
Mixed Layer ◽  
General Circulation ◽  
Circulation Model ◽  
Power Input ◽  
Ocean General Circulation Model ◽  
Wind Stress Curl ◽  
Total Energy Flux

AbstractThe total energy flux leaving the ocean’s spatially and seasonally varying mixed layer is estimated using a global ⅝1/10° ocean general circulation model. From the total wind-power input of 3.33 TW into near-inertial waves (0.35 TW), subinertial fluctuations (0.87 TW), and the time-mean circulation (2.11 TW), 0.92 TW leave the mixed layer, with 0.04 TW (11.4%) due to near-inertial motions, 0.07 TW (8.04%) due to subinertial fluctuations, and 0.81 TW (38.4%) due to time-mean motions. Of the 0.81 TW from the time-mean motions, 0.5 TW result from the projection of the horizontal flux onto the sloped bottom of the mixed layer. This projection is negligible for the transient fluxes. The spatial structure of the vertical flux is determined principally by the wind stress curl. The mean and subinertial fluxes leaving the mixed layer are approximately 40%–50% smaller than the respective fluxes across the Ekman layer according to the method proposed by Stern. The fraction related to transient fluctuations tends to decrease with increasing depth of the mixed layer and with increasing strength of wind stress variability.

The Vertical Structure of Eddy Heat Transport Simulated by an Eddy-Resolving OGCM

2010 ◽  
Vol 40 (2) ◽  
pp. 340-353 ◽  
Author(s):  
Bo Young Yim ◽  
Yign Noh ◽  
Bo Qiu ◽  
Sung Hyup You ◽  
Jong Hwan Yoon
Keyword(s):  
Heat Transport ◽  
Mixed Layer ◽  
General Circulation ◽  
Vertical Structure ◽  
Mixed Layer Depth ◽  
Circulation Model ◽  
Ocean General Circulation Model ◽  
Spatial And Temporal Variation ◽  
Observation Data ◽  
Eddy Heat Transport

Abstract The vertical structure of meridional eddy heat transport (EHT) of the North Pacific was investigated by analyzing the results from an eddy-resolving ocean general circulation model (OGCM) with a horizontal resolution of , while comparing with previous simulation results and observation data. In particular, the spatial and temporal variation of the effective depth of EHT He was investigated, which is defined by the depth integrated EHT (D-EHT) divided by EHT at the surface. It was found that the annual mean value of He is proportional to the eddy kinetic energy (EKE) level at the surface in general. However, its seasonal variation is controlled by the mixed layer depth (MLD) in the extratropical ocean (>20°N). Examination of the simulated eddy structures reveals that the temperature associated with mesoscale eddies is radically modified by the surface forcing in the mixed layer, while the velocity field is not, and the consequent enhanced misalignment of temperature and velocity anomalies leads to the radical change of EHT across the seasonal thermocline.

Simulation of the planktonic ecosystem response to pre- and post-1976 forcing in an isopycnic model of the North Pacific

2001 ◽  
Vol 58 (4) ◽  
pp. 703-722 ◽  
Author(s):  
S P Haigh ◽  
K L Denman ◽  
W W Hsieh
Keyword(s):  
Mixed Layer ◽  
North Pacific ◽  
General Circulation ◽  
Current System ◽  
Mixed Layer Depth ◽  
Circulation Model ◽  
Ecosystem Model ◽  
Ocean General Circulation Model ◽  
Export Production ◽  
Ocean Station Papa

To investigate the hypothesis that the 1976 "regime shift" in North Pacific fish populations resulted from climatic change propagating up the fisheries food web, we have embedded a four-component planktonic ecosystem model in an ocean general circulation model. The Miami isopycnic model (MICOM) has been implemented on a 2° grid over the domain from 18°S to 61°N, with a Kraus–Turner-type mixed layer model overlaying 10 isopycnal layers. An initial baseline run with forcing for the period 1952–1988 reasonably reproduces the spatial patterns and seasonal changes in SeaWiFS images. Estimates of annual net and export production compare well with contemporary observations of primary and export production at Ocean Station Papa in the subarctic North Pacific but are low by a factor of 8–10 at station ALOHA near Hawaii. Two subsequent runs with forcing for the periods 1952–1975 and 1977–1988 show the main gyres to strengthen after 1976 with large areas of increased mixed layer depth. In the light-limited subarctic, limited areas of shallower spring mixed layer produced increased phytoplankton biomass, whereas in the nutrient-limited subtropical gyre, increased nutrients (or migration of the subarctic front and the equatorial current system into the gyre) after 1976 correlated with increased plankton biomass.

scholarly journals The use of tidally induced vertical-mixing schemes in simulating the Pacific deep-ocean state

2021 ◽  
Author(s):  
Satoshi Osafune ◽  
Nozomi Sugiura ◽  
Toshimasa Doi ◽  
Tadashi Hemmi ◽  
Shuhei Masuda
Keyword(s):  
General Circulation ◽  
Vertical Mixing ◽  
Circulation Model ◽  
Deep Ocean ◽  
Ocean General Circulation Model ◽  
Physical Parameters ◽  
Surface Mixed Layer ◽  
Water Properties ◽  
The Pacific ◽  
Mixing Schemes

AbstractAn optimization experiment was conducted to reproduce the climatological distribution of water properties with an ocean general circulation model in which interior vertical mixing below the surface mixed layer is represented by tidally induced near- and far-field vertical-mixing schemes. Globally constant parameters in the tidally induced mixing schemes along with other physical parameters are optimally estimated based on the Green’s function method. The optimized model performs reasonably well in reproducing the deep-water properties of the Pacific Ocean, suggesting that the combination of tidally induced vertical-mixing schemes is useful in providing a reliable simulation of the deep-ocean state, consistent with both observed broad-scale hydrographic characteristics and recent knowledge of mixing. Adjustment of the parameters in the near-field mixing scheme was effective in improving simulation of the deep-ocean state. These results suggest that the adjustment of a small number of globally constant parameters in tidally induced and other mixing schemes based on recent knowledge of mixing through data assimilation may enable improvements in ocean state estimation throughout the entire water column, including the deep 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

scholarly journals Impact of the regional climate and substance properties on the fate and atmospheric long-range transport of persistent organic pollutants – examples of DDT and γ-HCH

2005 ◽  
Vol 5 (6) ◽  
pp. 12569-12615 ◽  
Author(s):  
V. S. Semeena ◽  
J. Feichter ◽  
G. Lammel
Keyword(s):  
Steady State ◽  
Mixed Layer ◽  
General Circulation ◽  
Regional Climate ◽  
Chemical Properties ◽  
Circulation Model ◽  
Sea Surface ◽  
Surface Mixed Layer ◽  
Quasi Steady State ◽  
Physico Chemical

Abstract. A global multicompartment model which is based on a 3-D atmospheric general circulation model (ECHAM5) coupled to 2-D soil, vegetation and sea surface mixed layer reservoirs, is used to simulate the atmospheric transports and total environmental fate of dichlorodiphenyltrichloroethane (DDT) and γ-hexachlorocyclohexane (γ-HCH, lindane). Emissions into the model world reflect the substance's agricultural usage in 1980 and 1990 and same amounts in sequential years are applied. Four scenarios of DDT usage and atmospheric decay and one scenario of γ-HCH are studied over a decade. The global environment is predicted to be contaminated by the substances within ca. 2 a (years). DDT reaches quasi-steady state within 3–4 a in the atmosphere and vegetation compartments, ca. 6 a in the sea surface mixed layer and near to or slightly more than 10 a in soil. Lindane reaches quasi-steady state in the atmosphere and vegetation within 2 a, in soils within 8 years and near to or slightly more than 10 a and in the sea surface mixed layer. The substances' differences in environmental behaviour translate into differences in the compartmental distribution and total environmental residence time, τoverall. τoverall≈0.8 a for γ-HCH's and ≈1.0–1.3 a for the various DDT scenarios. Both substances' distributions are predicted to migrate in northerly direction, 5–12° for DDT and 6.7° for lindane between the first and the tenth year in the environment. Cycling in various receptor regions is a complex superposition of influences of regional climate, advection, and the substance's physico-chemical properties. As a result of these processes the model simulations show that remote boreal regions are not necessarily less contaminated than tropical receptor regions. Although the atmosphere accounts for only 1% of the total contaminant burden, transport and transformation in the atmosphere is key for the distribution in other compartments. Hence, besides the physico-chemical properties of pollutants the location of application (entry) affects persistence and accumulation emphasizing the need for georeferenced exposure models.

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