scholarly journals Decreasing Biological Production and Carbon Export Due to the Barrier Layer: A Case Study in the Bay of Bengal

2021 ◽  
Vol 8 ◽  
Author(s):  
Huangchen Zhang ◽  
Linbin Zhou ◽  
Kaizhi Li ◽  
Zhixin Ke ◽  
Yehui Tan
Keyword(s):  
Barrier Layer ◽  
Bay Of Bengal ◽  
Coastal Waters ◽  
Physical Phenomenon ◽  
Vertical Mixing ◽  
Carbon Export ◽  
Biological Production ◽  
One Dimensional ◽  
Lower Carbon

A freshwater-induced barrier layer (BL) is a common physical phenomenon both in coastal waters and the open ocean. To examine the effects of BL on the biological production and the associated carbon export, a physical-biogeochemical survey was conducted in the Bay of Bengal. Severe depletions of surface phosphorus and the deepening of the nutricline were observed at the BL-affected stations due to the vertical mixing prohibition. The lowered surface chlorophyll a (Chl a) and squeezed deep Chl a maximum (DCM) layer also resulted in the ~18% lowered vertically integrated Chl a at the said stations. The composition of the net-sampled zooplankton was altered, and the abundance decreased by half at the BL-affected station (29.68 ind. m−3) compared with the unaffected station (55.52 ind. m−3). Such reductions in major zooplankton groups were confirmed by a video plankton recorder (VPR). The VPR observation indicated that there was a lower (by one-half) abundance of detritus at the BL-affected station, while the much lower carbon export flux rates were estimated to be at the BL-affected station (0.31 mg C m−2 d−1) rather than the unaffected station (0.77 mg C m−2 d−1). An idealized one-dimensional nutrient-phytoplankton-detritus model identified that the existence of BL can lead to decreased surface nutrients and phytoplankton concentrations, squeezed DCM layers, and lower detritus abundances. Finally, this study indicated that BL layers inhibit biological production and reduce carbon export, thus playing an important role in the ocean biogeochemical cycles.

scholarly journals Response of the Salinity-Stratified Bay of Bengal to Cyclone Phailin

2019 ◽  
Vol 49 (5) ◽  
pp. 1121-1140 ◽  
Author(s):  
Dipanjan Chaudhuri ◽  
Debasis Sengupta ◽  
Eric D’Asaro ◽  
R. Venkatesan ◽  
M. Ravichandran
Keyword(s):  
Barrier Layer ◽  
Bay Of Bengal ◽  
Sea Surface ◽  
Density Stratification ◽  
Upper Ocean ◽  
Dimensional Model ◽  
Cyclone Track ◽  
Surface Salinity ◽  
Near Surface ◽  
One Dimensional

AbstractCyclone Phailin, which developed over the Bay of Bengal in October 2013, was one of the strongest tropical cyclones to make landfall in India. We study the response of the salinity-stratified north Bay of Bengal to Cyclone Phailin with the help of hourly observations from three open-ocean moorings 200 km from the cyclone track, a mooring close to the cyclone track, daily sea surface salinity (SSS) from Aquarius, and a one-dimensional model. Before the arrival of Phailin, moored observations showed a shallow layer of low-salinity water lying above a deep, warm “barrier” layer. As the winds strengthened, upper-ocean mixing due to enhanced vertical shear of storm-generated currents led to a rapid increase of near-surface salinity. Sea surface temperature (SST) cooled very little, however, because the prestorm subsurface ocean was warm. Aquarius SSS increased by 1.5–3 psu over an area of nearly one million square kilometers in the north Bay of Bengal. A one-dimensional model, with initial conditions and surface forcing based on moored observations, shows that cyclone winds rapidly eroded the shallow, salinity-dominated density stratification and mixed the upper ocean to 40–50-m depth, consistent with observations. Model sensitivity experiments indicate that changes in ocean mixed layer temperature in response to Cyclone Phailin are small. A nearly isothermal, salinity-stratified barrier layer in the prestorm upper ocean has two effects. First, near-surface density stratification reduces the depth of vertical mixing. Second, mixing is confined to the nearly isothermal layer, resulting in little or no SST cooling.

Particle Backscattering Variability in the Coastal Waters of Bay of Bengal: A Case Study Along Off Kakinada and Yanam Regions

2013 ◽  
Vol 10 (6) ◽  
pp. 1517-1521 ◽  
Author(s):  
T. Preethi Latha ◽  
P. V. Nagamani ◽  
B. Srinivasa Rao ◽  
P. Amarendra ◽  
K. H. Rao ◽  
...  
Keyword(s):  
Bay Of Bengal ◽  
Coastal Waters ◽  
Particle Backscattering

scholarly journals Importance of vertical mixing and barrier layer variation on seasonal mixed layer heat balance in the Bay of Bengal

2017 ◽  
Author(s):  
Ullala Pathiranage Gayan Pathirana ◽  
Gengxin Chen ◽  
Tilak Priyadarshana ◽  
Dongxiao Wang
Keyword(s):  
Heat Flux ◽  
Mixed Layer ◽  
Barrier Layer ◽  
Bay Of Bengal ◽  
Heat Balance ◽  
Seasonal Cycle ◽  
Sensible Heat Flux ◽  
Vertical Mixing ◽  
Shortwave Radiation ◽  
Barrier Layer Thickness

Abstract. Time series measurements from the Research Moored Array for African-Asian-Australian Monsoon Analysis and Prediction (RAMA) moorings at 15° N, 90° E; 12° N, 90° E; 8° N, 90° E; 4° N, 90° E; 1.5° N, 90° E; 0° N, 90° E are used to investigate the seasonal mixed-layer heat balance and the importance of barrier layer thickness (BLT) and vertical mixing (Q−h) in the Bay of Bengal (BoB). It is found that the BLT, Q−h and mixed-layer heat balance all have a strong seasonality in the central BoB. Sea surface temperature (SST), salinity and wind are important for the observed strongest seasonal cycle of BLT in the central BoB, and wind is more important than the SST in the southern BoB. The heat storage rate (HSR) is primarily driven by latent heat flux and shortwave radiation (QSW and QL). Seasonal variations and the magnitudes of longwave radiation (QLW), sensible heat flux (QS), and horizontal mixed-layer heat advection are much weaker compared to those of QSW and QL. Q−h follows a pronounced seasonal cycle in the central BoB and is significantly positively correlated with the seasonal cycle of BLT at each mooring location. The seasonal variability of the stability favors the Q−h during winter and summer monsoon and suppress Q−h during monsoon transition periods. We found that Q−h plays the secondary role in the seasonal mixed-layer heat balance in the BoB. It is evident from the analysis that Q−h associated with temperature inversion (∆T) warms the mixed layer during winter and cools the mixed layer during summer. The warming tendency during winter is strong in the central BoB and weakens towards the equator, indicating a cooling tendency around the year. Our analysis further indicates the weakening of Q−h during monsoon transition periods favors the existence of warmer SST in the BoB, associated with thermal and salinity stratification in the central BoB.

scholarly journals Stimulating Mechanistic Reasoning in Physics Using Student-Constructed Stop-Motion Animations

2021 ◽  
Author(s):  
Rayendra Wahyu Bachtiar ◽  
Ralph F. G. Meulenbroeks ◽  
Wouter R. van Joolingen
Keyword(s):  
Conceptual Understanding ◽  
Physical Phenomenon ◽  
Ninth Grade ◽  
Abstract Concepts ◽  
Projectile Motion ◽  
Mechanistic Reasoning ◽  
Stop Motion ◽  
Ninth Grade Students ◽  
Scientific Phenomena

AbstractThis article reports on a case study that aims to help students develop mechanistic reasoning through constructing a model based stop-motion animation of a physical phenomenon. Mechanistic reasoning is a valuable thinking strategy for students in trying to make sense of scientific phenomena. Ten ninth-grade students used stop-motion software to create an animation of projectile motion. Retrospective think-aloud interviews were conducted to investigate how the construction of a stop-motion animation induced the students’ mechanistic reasoning. Mechanistic reasoning did occur while the students engaged in creating the animation, in particular chunking and sequencing. Moreover, all students eventually exhibited mechanistic reasoning including abstract concepts, e.g., not directly observable agents. Students who reached the highest level of mechanistic reasoning, i.e., chaining, demonstrated deeper conceptual understanding of content.

Numerical simulation of gas-solid two-phase reaction flow with multiple moving boundaries

2015 ◽  
Vol 25 (2) ◽  
pp. 375-390 ◽  
Author(s):  
Qiao Luo ◽  
Xiaobing Zhang
Keyword(s):  
Numerical Simulation ◽  
Physical Phenomenon ◽  
Great Influence ◽  
Moving Boundaries ◽  
Charge Weight ◽  
Phase Reaction ◽  
Two Phase ◽  
Content Type ◽  
One Dimensional ◽  
Chamber Volume

Purpose – In engineering applications, gas-solid two-phase reaction flow with multi-moving boundaries is a common phenomenon. The launch process of multiple projectiles is a typical example. The flow of adjacent powder chambers is coupled by projectile’s motion. The purpose of this paper is to study this flow by numerical simulation. Design/methodology/approach – A one-dimensional two-phase reaction flow model and MacCormack difference scheme are implemented in a computational code, and the code is used to simulate the launch process of a system of multiple projectiles. For different launching rates and loading conditions, the simulated results of the launch process of three projectiles are obtained and discussed. Findings – At low launching rates, projectiles fired earlier in the series have little effect on the launch processes of projectiles fired later. However, at higher launching rates, the projectiles fired first have a great influence on the launch processes of projectiles fired later. As the launching rate increases, the maximum breech pressure for the later projectiles increases. Although the muzzle velocities increase initially, they reach a maximum at some launching rate, and then decrease rapidly. The muzzle velocities and maximum breech pressures of the three projectiles have an approximate linear relationship with the charge weight, propellant web size and chamber volume. Originality/value – This paper presents a prediction tool to understand the physical phenomenon of the gas-solid two-phase reaction flow with multi-moving boundaries, and can be used as a research tool for future interior ballistics studies of launch system of multiple projectiles.

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