Seasonal changes in the hydrological and biological environments off Port Hacking, Sydney

1966 ◽  
Vol 17 (1) ◽  
pp. 77 ◽  
Author(s):  
BS Newell
Keyword(s):  
Seasonal Changes ◽  
Algal Blooms ◽  
High Salinity ◽  
Vertical Mixing ◽  
Hydrological Regime ◽  
Offshore Water ◽  
Subtropical Water ◽  
Tropical Water ◽  
Land Drainage ◽  
The Western Pacific

Data obtained over 10 yr at the Port Hacking 100-m station show an annual cycle in some properties. In May the continental shelf is dominated by high salinity subtropical water from the western Pacific. From June to August, cooling and vertical mixing decrease temperatures and salinities at all depths. From September, tropical water of northern origin penetrates southwards, increasing temperatures and decreasing salinity at 10 and 50 m. This tropical water exerts its maximum influence in March. From September to March other offshore water from deeper than 100 m rises onto the shelf, decreasing temperature, salinity, and oxygen, but increasing nitrate. In addition there is probably a continual land drainage influence on the hydrological regime. Algal blooms occur from August to April, in association with the penetration of nitrate-rich water onto the shelf.

Origin and circulation of water types of the 25.00 sigma-t surface of the South-west Pacific

1969 ◽  
Vol 20 (2) ◽  
pp. 105 ◽  
Author(s):  
DJ Rochford
Keyword(s):  
Continental Margin ◽  
High Salinity ◽  
Vertical Mixing ◽  
Water Type ◽  
Subtropical Water ◽  
Water Types ◽  
Low Salinity ◽  
Tropical Water ◽  
South West ◽  
Mixed Transition

The salinity and oxygen of 25.00 sigma-t waters of the Tasman and Coral Seas have been averaged within 5� squares. From these average values four water types were identified by their salinity-oxygen relations. These were: a tropical high salinity (mean salinity 36.00‰, mean oxygen 3.50 ml/l.), a tropical low salinity (mean salinity 35.25‰, mean oxygen 3.10 ml/l.), a subtropical high salinity (mean salinity 35.75‰, mean oxygen 5.15 ml/l.), and a subtropical low salinity (mean salinity 35.46‰, mean oxygen 5.15 ml/l.). Waters north of 15�S. were all mixtures of the two tropical water types, and those south of 35� S. were all mixtures of the two subtropical water types. Topography of the 25.00 sigma-t surface showed easterly flow at around 15� S. and, as far as could be interpreted, easterly flow at 35� S. Between these two zones of tropical and subtropical water types there occurred a region of mixed transition waters in which large meridional gradients of oxygen but small gradients of salinity were found. This transition region occupied a much larger area off east Australia than elsewhere, mainly because there was greater meridional exchange of the tropical and subtropical water types off east Australia. North of 20� S. the high salinity subtropical water type spreads northward in the central Tasman and Coral Seas in summer and the low salinity tropical water type spreads southward along the Queensland continental margin in winter. South of 20� S. it was impossible to separate changes due to circulation from those caused by vertical mixing and winter formation of 25.00 sigma-t water at the surface.

Desalination of brackish water for agriculture: challenges and future perspectives for seawater intrusion areas in Vietnam

2018 ◽  
Vol 67 (3) ◽  
pp. 211-217 ◽  
Author(s):  
Vo Huu Cong
Keyword(s):  
Reverse Osmosis ◽  
Seawater Intrusion ◽  
Brackish Water ◽  
Large Scale ◽  
High Salinity ◽  
Hydrological Regime ◽  
Water Withdrawal ◽  
Electrochemical Processes ◽  
Nano Filtration ◽  
Exchange Resins

Abstract This research aims to provide an overview of the seawater encroachment threat on agriculture in lowland areas and potential solutions for better practices. It was found that the Mekong river delta experiences severe impacts from climate change with more than 75% of provinces affected by seawater intrusion, of which Kien Giang, Ca Mau and Ben Tre provinces are the most influenced with 70% affected areas. The salinity of river water was observed in the range of 15–30 g/L in 2015; meanwhile, the strongest tolerated rice species reached ceiling values of 3–4 g/L. Emerging challenges were identified due to the uncertain upstream hydrological regime coupled with high levels of tide, field evaporation and water withdrawal. The development strategies of affected provinces are given on the modification of rice tolerant capacity, and modification to aquaculture in areas with high salinity, in which water purification is in urgent demand. Desalination technologies have been proposed with various innovations which are still not practical on a large scale. The desalination of seawater and brackish water by reverse osmosis, nano-filtration, electro-dialysis, ion-exchange resins, electrochemical processes and thermal distillation has been applied to agriculture. The advance reverse osmosis shows most potential because of its advances in treating performance, cost effectiveness and effective rejection of brine.

scholarly journals Western Pacific SST Prediction with an Intermediate El Niño Prediction Model

2005 ◽  
Vol 133 (5) ◽  
pp. 1343-1352 ◽  
Author(s):  
Jong-Seong Kug ◽  
In-Sik Kang ◽  
Jong-Ghap Jhun
Keyword(s):  
Prediction Model ◽  
El Niño ◽  
El Nino ◽  
Vertical Mixing ◽  
Western Pacific ◽  
Central Pacific ◽  
Modified Model ◽  
Sst Variability ◽  
Predictive Skill ◽  
The Western Pacific

Abstract To improve forecasting skills in the western Pacific sea surface temperature (SST), the authors utilized and modified an intermediate El Niño prediction model. The original model does not have the major SST thermodynamics for western Pacific SST variability, so it cannot simulate interannual variation in the western Pacific correctly. Therefore, the authors have introduced some modifications, such as heat flux and vertical mixing, into the dynamical model in order to capture SST thermodynamics more realistically. The modified model has better forecast skill than the original one, not only for the western Pacific but also for the eastern-central Pacific. The model has predictive skill up to 6-months lead time as judged by a correlation exceeding 0.5.

scholarly journals On the Variability of the Circulation and Water Mass Properties in the Eastern Levantine Sea between September 2016–August 2017

Water ◽  
2019 ◽  
Vol 11 (9) ◽  
pp. 1741 ◽  
Author(s):  
Mauri ◽  
Sitz ◽  
Gerin ◽  
Poulain ◽  
Hayes ◽  
...  
Keyword(s):  
High Salinity ◽  
Autonomous Systems ◽  
Vertical Mixing ◽  
The North ◽  
Levantine Sea ◽  
Surface Circulation ◽  
Basin Scale ◽  
Geographical Position ◽  
Surface Drifters

The surface circulation and the thermohaline properties of the water masses of the eastern Levantine Sea (Mediterranean Sea) were monitored with mobile autonomous systems (surface drifters and gliders) during the period September 2016–August 2017. The drifters provided data for more than a year and revealed complex circulation features at scales ranging from the basin scale to the sub-mesoscale. Three drifters were captured in a semi-permanent gyre (Cyprus Eddy) allowing a quantitative study of its kinematics. During the experiment, three gliders were operated, in two different periods: September to December 2016 and February to March 2017. The autonomous instruments crossed the prevailing sub-basin structures several times. The collected in-situ observations were analyzed and interpreted in concert with remote sensing products (sea surface temperature and altimetry). The evolution of some of the prevailing features confirmed the complexity of the circulation of the basin. The Cyprus Eddy is the most persistent anticyclone, moving its geographical position and sometimes merging with the North Shikmona Eddy in a bigger structure. The gliders sampled this wide anticyclonic feature revealing its vertical structure in the two different periods. In fall, in stratified conditions, a high salinity core is evident below the thermocline. The isopycnals are characterized by an upward bending over the high salinity lens and a downward bending below it, typical of an anticyclonic modewater eddy. In winter, the core disappears following the vertical mixing that, homogenizes the upper Cyprus Eddy water down to 300 m.

scholarly journals Tracing the sources of nutrients fueling dinoflagellate red tides occurring along the coast of Korea using radium isotopes

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Hyeong Kyu Kwon ◽  
Guebuem Kim ◽  
Yongjin Han ◽  
Junhyeong Seo ◽  
Weol Ae Lim ◽  
...  
Keyword(s):  
Harmful Algal Blooms ◽  
Algal Blooms ◽  
Red Tide ◽  
Subsurface Layer ◽  
Vertical Mixing ◽  
Eastern Coast ◽  
Nutrient Concentrations ◽  
Red Tides ◽  
Radium Isotopes ◽  
Nutrient Sources

Abstract It is a well held concept that the magnitude of red-tide occurrence is dependent on the amount of nutrient supply if the conditions are same for temperature, salinity, light, interspecific competition, etc. However, nutrient sources fueling dinoflagellate red-tides are difficult to identify since red tides usually occur under very low inorganic-nutrient conditions. In this study, we used short-lived Ra isotopes (223Ra and 224Ra) to trace the nutrient sources fueling initiation and spread of Cochlodinium polykrikoides blooms along the coast of Korea during the summers of 2014, 2016, and 2017. Horizontal and vertical distributions of nutrient concentrations correlated well with 224Ra activities in nutrient-source waters. The offshore red-tide areas showed high 224Ra activities and low-inorganic and high-organic nutrient concentrations, which are favorable for blooming C. polykrikoides in competition with diatoms. Based on Ra isotopes, the nutrients fueling red-tide initiation (southern coast of Korea) are found to be transported horizontally from inner-shore waters. However, the nutrients in the spread region (eastern coast of Korea), approximately 200 km from the initiation region, are supplied continuously from the subsurface layer by vertical mixing or upwelling. Our study highlights that short-lived Ra isotopes are excellent tracers of nutrients fueling harmful algal blooms in coastal waters.

A new hydrology: effects on ecosystem form and functioning

2012 ◽  
Vol 69 (8) ◽  
pp. 1377-1379 ◽  
Author(s):  
Daniel L. Roelke ◽  
Sofie Spatharis ◽  
Simon M. Mitrovic
Keyword(s):  
Climate Change ◽  
Population Growth ◽  
Harmful Algal Blooms ◽  
Algal Blooms ◽  
Human Population ◽  
Vertical Mixing ◽  
System Level ◽  
Hydrologic Processes ◽  
Human Population Growth ◽  
Altered Hydrology

Water cycles are changing because of human population growth and climate change. Such changes will affect fundamental system-level characteristics that in turn will greatly influence ecosystem form and functioning. Here, a collection of papers is offered that furthers our understanding of cause and effect relationships between altered hydrology and various ecosystem properties. Combined, these papers address issues related to inflows, connectivity, and circulation and vertical mixing. In regards to altered inflows, this collection of papers addresses how seagrass bed communities, incidence of some haptophyte harmful algal blooms, and biodiversity of intermittently flowing streams might respond. These papers also address factors that influence connectivity in wetlands, and in the case of a lake and its neighboring wetland, how connectivity between systems can profoundly affect ecosystem form and functioning. Finally, the effects of altered circulation and vertical mixing are addressed as they relate to the spread of some cyanobacteria blooms to higher latitudes. The reader of this collection of papers gains a better appreciation of how ecosystem form and functioning is influenced by hydrologic processes and can conclude that there is a need for continued research in this area to better understand the impacts of human population growth and climate change.

scholarly journals Rasgos hidrográficos y batimétricos del Refugio Nacional de Vida Silvestre Ostional y áreas adyacentes, Guanacaste, Costa Rica

2012 ◽  
Vol 3 ◽  
pp. 145
Author(s):  
Carlos Luis Brenes ◽  
Amaru Márquez ◽  
Wagner Quirós ◽  
Rosario Benavides
Keyword(s):  
Costa Rica ◽  
Mixed Layer ◽  
Surface Layers ◽  
Subtropical Water ◽  
Tropical Water ◽  
Surface Temperatures ◽  
Northern Pacific ◽  
Pacific Area

Entre el 6 y el 11 de febrero del 2012, se realizó un levantamiento hidrográfico y batimétrico en la región situada entre Punta Guiones y Cuajiniquil, en el Pacífico norte de Costa Rica. Las temperaturas superficiales se ubicaron entre los 25.5 y 27.5°C, y el rango salino superficial estuvo entre 33.2 y 33.8 PSU. La termoclina se localizó a los 20 m en el extremo norte de la región, mientras que en el extremo sur, desde Ostional hasta Guiones, se observó ligeramente más profunda, alrededor de los 25 m. El espesor de la capa de mezcla fue de 10 m en toda el área estudiada. Dos giros, uno ciclónico y otro anticiclónico, se registraron en la región frente a Ostional. Los estratos superficiales estuvieron ocupados por el Agua Superficial Tropical (AST), con salinidades inferiores a 34 PSU y temperaturas superiores a 26°C, y los niveles intermedios (~ 50 m), por el Agua Subsuperficial Subtropical (ASS), caracterizada por un núcleo salino cercano a las 35 PSU. La batimetría de la región muestra isóbatas paralelas a la costa, con una elevación alrededor de los 20 m de profundidad en el extremo sur de la zona estudiada. El grado de inclinación o pendientes no sobrepasaron los 14.5°. Abstract Between February 6 and 11, 2012, a hydrographic cruise and bathymetric sounding were conducted in the region located between Guiones and Cuajiniquil, in the Northern Pacific area of Costa Rica. The range of surface temperatures is 25.5 to 27.5°C, and the saline surface ranges between 33.2 and 33.8 PSU. The thermocline is located at 20 m at the northern end of the region, while at the southern end, from Ostional up to Guiones, it was observed slightly deeper, approximately 25 m deep. The thickness of the mixed layer was 10 m in virtually all the studied area. Two gyres, one cyclonic and another anticyclonic, were observed in front of Ostional. The surface layers were occupied by the Surface Tropical Water (STW), with salinities below 34 PSU and temperatures greater than 26°C, and the intermediate levels (~ 50 m) by the Subsurface Subtropical Water (SSW), characterized by a saline core near 35 PSU. The bathymetry of the region shows isobaths parallel to the coast, with an elevation close to 20 m deep at the southern end of this area. The degree of inclination did not exceed 14.5°.

Relating River Plume Structure to Vertical Mixing

2005 ◽  
Vol 35 (9) ◽  
pp. 1667-1688 ◽  
Author(s):  
Robert D. Hetland
Keyword(s):  
Coordinate System ◽  
Critical Thickness ◽  
High Salinity ◽  
Near Field ◽  
Vertical Mixing ◽  
River Plume ◽  
Plume Structure ◽  
Shear Mixing ◽  
Wind Mixing ◽  
Work Done

Abstract The structure of a river plume is related to the vertical mixing using an isohaline-based coordinate system. Salinity coordinates offer the advantage of translating with the plume as it moves or expanding as the plume grows. This coordinate system is used to compare the relative importance of different dynamical processes acting within the plume and to describe the effect each process has on the structure of the plume. Vertical mixing due to inertial shear in the outflow of a narrow estuary and wind mixing are examined using a numerical model of a wind-forced river plume. Vertical mixing, and the corresponding entrainment of background waters, is greatest near the estuary mouth where inertial shear mixing is large. This region is defined as the near field, with the more saline, far-field plume beyond. Wind mixing increases the mixing throughout the plume but has the greatest effect on plume structure at salinity ranges just beyond the near field. Wind mixing is weaker at high salinity classes that have already been mixed to a critical thickness, a point where turbulent mixing of the upper layer by the wind is reduced, protecting these portions of the plume from further wind mixing. The work done by mixing on the plume is of similar magnitude in both the near and far fields.

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