Formation Of Thermocline Research Articles

The Significance of Internal Variability for Numerical Experimentation and Analysis

When regional (limited-area) models of the hydrodynamics of the atmosphere and ocean are run over an extended time, variability unrelated to external “drivers” emerges: this variability is colloquially named “hydrodynamical noise” or just “noise”. This article summarises what we have learned in the past few years about the properties of such noise and its implications for numerical experimentation and analysis. The presence of this noise can be identified easily in ensembles of numerical simulations, and it turns out that the intensity of the noise is closely linked to scale-dependent “memory”. The “memory” in the atmosphere and ocean describes the persistence of atmospheric and oceanic conditions, usually quantified by an autocorrelation function. At the system level, this “memory” term, as given by Hasselmann’s stochastic climate model, plays a key role. In the case of marginal seas, the process of baroclinic instability modulated by tides and the formation of seasonal thermoclines are significant aspects. Some more general aspects are discussed, such as the applicability of the stochastic climate model to systems outside of atmospheric and oceanic dynamics, for example, biogeochemical systems, the irreversibility of tipping points, the challenges of detecting changes beyond a noise level, and the attribution of causes of change.

Coccolithophore Distribution in the Western Black Sea in the Summer of 2016

Coccolithophores are an important component of phytoplankton abundance and biomass in the brackish environments of the Black Sea. Here, the abundance, composition, and distribution of coccolithophores were investigated in water samples taken from the first 50 m at 18 stations in the western Black Sea during a coccolithophore bloom, in June 2016. The total cell abundances ranged from 2 to 763 × 104 coccospheres L−1; Emiliania huxleyi was the most dominant species, but also Syracosphaera spp. (S. dilatata and S. molischii), Acanthoica (A. acanthifera and A. quattrospina), and Algirosphaera robusta displayed remarkably high concentrations. The formation of the seasonal thermocline significantly affects the vertical distribution of coccolithophores. Emiliania huxleyi, Syracosphaera spp., and Acanthoica spp. were restricted to the upper part of the water column, whereas high abundances of Algirosphaera robusta occurred below the thermocline. Overall, our results show significant differences in the vertical (ANOSIM R = 0.50, p = 0.0001) and spatial (ANOSIM R = 0.18, p = 0.0006) distribution of coccolithophores. Higher abundances of E. huxleyi and Syracosphaera spp. were recorded in the northwestern inner shelf region when compared to the open-sea samples. The observed coccolithophore spatial distribution is suggested to be mostly associated with the influx of less saline river water with high nutrient concentrations.

Spatial and seasonal distribution of particulate phosphorous and nitrogen in the Persian Gulf: Nitrogen enrichment ties to diazotroph bloom in stratified warm waters

Understanding the particulate organic and inorganic forms of nutrients and their elemental stoichiometry in suspended particulate matter of marginal seas has important implications in several areas. Here, we present the findings from two consecutive research expeditions conducted in September 2021 and January 2022 aboard the Persian Gulf Explorer research vessel, focused on the particulate P and N in the Persian Gulf and the Strait of Hormuz. The prominent features of spatial and seasonal distribution characteristics were nearshore-offshore decreasing gradients in particulate nutrients, the summer-to-winter declining trend in particulate nutrients more notably for particulate organic nitrogen, and higher biomass N:P ratio in summer than in winter with high spatial inhomogeneity. The trends were mainly governed by shallow remineralization of organic matter, resuspension of fine sediments, summer stratification/winter mixing of the water column, and inflow of the Indian Ocean Surface Waters from the Gulf of Oman. The contribution of inorganic N in the particulate pool of N (1.8% in summer and 1.3% in winter) was much less than the contribution of inorganic P in the particulate pool of P (23.0% in summer and 32.4% in winter), and hence the biomass N:P was higher than the corresponding bulk N:P by a factor of ∼1.5. Seasonal pattern in biomass N:P was similar to those observed at many sites being higher in the summer and lower in the winter. The formation of summer thermocline, characterized by high surface temperature (∼33 °C) and limited upward flux of remineralized inorganic nutrients, coincided with the proliferation of nitrogen-fixing cyanobacteria. Samples collected from the deep offshore region in summer showed significantly higher biomass N:P ratio, reaching up to 47, which is far beyond the classical Redfield ratio of 16. The central Persian Gulf experienced less seasonal variations than the deep region in the western Persian Gulf, the northwestern Arvand estuary, and the northwestern Gulf of Oman.

Abiotic features of Sukhyi and Grygorivskyi Estuaries' ecosystems as seaport water areas (northwestern part of the Black Sea)

The article studies the location, origin and abiotic features of the ecosystems of Sukhyi and Grygorivskyi Estuaries that were transformed into water areas of Chornomorsk and Yuzhnyi, the major seaports of Ukraine, in the second half of the 20th century. It also presents a comparison of the abiotic conditions of such ecosystems based on the analysis of published data and additional database materials of the Institute of Marine Biology of the National Academy of Sciences of Ukraine.
 The construction of permanent and deep watercourses in the water areas of the estuaries alongside with large-scale dredging works led to their transformation into narrow sea bays with the depths significantly exceeding those in the adjacent sea. The construction of berths included levelling the coastline, changing the bottom profile and increasing the water volumes by more than three times. Now the volumes amount to 45–55 million m3 in Sukhyi Estuary and 60–70 million m3 in Grygorivskyi Estuary. The current abiotic features of the estuaries' ecosystems are determined by the processes occurring in Odesa sea region of the northwestern part of the Black Sea where such estuaries are located. The estuaries' hydrochemical regime depends on the yearly meteorological features, the intensity of water exchange with the sea, the amount of biogenic matter coming from natural (surface runoff, precipitation) and anthropogenic sources and the intra-aquatic processes of new organic matter production and destruction. Dredging activities resulted in emergence of the conditions for halocline and thermocline formation that hamper vertical water exchange. The formation of zones with extreme values of dissolved oxygen was also noted during the research. The maximum values in the surface layers result from photosynthesis development, while the minimum values in the bottom layers are caused by accumulation and destruction of dead organic matter. This information can be used to forecast the consequences arising from similar anthropogenic interference in the functioning of coastal marine ecosystems.

Experimental investigation of heat dispatch controllability through simultaneous charging-discharging and stand-alone discharging operations in vertical cylindrical sensible heat storage tank

Using a vertical cylindrical thermal energy storage (TES) tank with helical discharging coil fitted inside, the present study experimentally investigates the scarcely studied simultaneous charging and discharging (SCAD) mode, as well as the discharging-alone operation following a substantial stand-alone period. The temperature distributions within the tank, coil outlet temperature and primary thermocline thickness serve as the key performance trackers for the storage tank. The primary thermocline thickness increases with increasing coil side flow rate during the SCAD operation. The SCAD operation exhibited the splitting of the primary thermocline, leading to the formation of a secondary thermocline in the lower half of the tank. The sustenance of secondary thermocline, thermal gradients across the tank height, and the discharging efficiency are found to decrease with increasing charging flow rate, whereas the coil outlet temperature and the primary thermocline thickness increase. The highest average discharging efficiency of 80.1 % is observed for the TES charging at 0.5 L/min at 70 °C, accompanied by the 2 L/min discharging flow rate. The average thermal energy stored is the maximum (1758 kJ) for the TES charging at 1.25 L/min at 70 °C, with discharging rate of 0.5 L/min. The stand-alone period prior to the discharging-alone operation exhibits the heat content retention capability of the storage and allows for the thermocline formation. The time required for thermal stratification is more with the higher initial charging temperature. The time required for the complete discharging of the TES storage tank decreases with increasing coil-side flow rate. These modes provide ample operational flexibility and heat content dispatch controllability, resulting in the versatility of the system.

PANDA experiments within the OECD/NEA HYMERES-2 project on containment hydrogen distribution, thermal radiation and suppression pool phenomena

In this article, we summarize the experimental results obtained in the large-scale thermal-hydraulics PANDA facility (PSI, Switzerland) within the OECD/NEA HYMERES2 project. The experiments addressing hydrogen distribution allowed characterizing the flow patterns forming from jet flows impacting plates or grating platforms and the following interaction with a postulated hydrogen cloud in the containment dome. The experiments with activation of safety components allowed to compare the effects of multiple spray nozzles with a single spray nozzle or multiple cooler units with unique cooler and to assess the scalability of the related thermal hydraulics phenomena such as pressure histories, power removed, gas mixture distribution. The experiments related to thermal radiation confirmed that the presence of steam in a containment atmosphere even at very low concentration (in the order of 0.1 %) has a significant impact on the evolution of containment mixture temperature.The experiments studying pressure suppression pool phenomena provided insight on the formation and stability of thermocline under a variety of steam release conditions, e.g. from load reduction rings and from multi-hole sparger; moreover allowed to characterize containment pressure histories as function of sparger submergence in the suppression pool.

Thermocline Formation in the Persian Gulf

Persian Gulf (PG) is a semi-enclosed water basin that is connected to the Gulf of Oman through the Strait of Hormuz. There are different forcing and climatic parameters influencing the thermocline development in the PG from winter to summer. These factors include tide, river inflow, solar radiation, evaporation, northwestern wind, and water exchange with the Gulf of Oman. In fact, the thermocline, which is often observed in the oceans and open seas, can be considered as a seasonal phenomenon in the ocean. In the present study, it is studied theoretically; and compared with the results of the Princeton Ocean Model (POM) in the PG. During winter to summer, solar heating created an intense thermocline that decoupled the surface mixed layer from the interior water. The data are reviewed as the measurements collected in 1992 and recent modeling results. Overall, through a theoretical study, it is concluded that thermocline formation is a seasonal phenomenon in the PG.

Variations in the Temporal and Spatial Distribution of Microalgae in Aquatic Environments Associated with an Artificial Weir

The construction of weirs causes changes in the aquatic environment and affects several aquatic organisms. To understand the ecosystem in the Sangju Weir, Gyeongsangbuk-do Province, variations in the spatiotemporal distribution and composition of microalgae communities were analyzed. Microalgae were collected fortnightly from April to November 2018 from six sites in the Nakdonggang River. There was significant variation in environmental factors, microalgal community structure, and flora. Microalgae communities were dominated by diatoms (e.g., Fragilariacrotonensis, Ulnariaacus, and Aulacoseiraambigua), green algae (e.g., genera Eudorina and Desmodesmus), cyanobacteria (e.g., genera Anabaena and Microcystis). Multidimensional scaling indicated that species composition and diversity were generally similar among sites but varied between the bottom and the surface and middle water layers. Vertical migration of microalgae was difficult to investigate because of the thermocline in the study area and high turbidity in the lower layer. The distribution of microalgae was little affected by the construction of the weir, but the formation of thermocline changed microalgae communities in the water layer.

Summer Wind-driven Upwelling and Tidal Mixing on the Western Kamchatka Shelf in the Sea of Okhotsk

The response of the thermohaline structure of water off the western Kamchatka shelf of the Sea of Okhotsk to the wind-driven upwelling and tidal mixing is analyzed, and the results are presented. The upwelling intensity was estimated based on the offshore Ekman mass transport (the upwelling index). The mean position of the tidal mixing front was determined using the spatial distribution of the Simpson-Hunter stratification parameter. The hydrographic observations and the results of the upwelling index calculation revealed the occurrence of the summer transient upwelling on the western Kamchatka shelf under certain synoptic conditions. The favorable meteorological conditions for the upwelling development were associated with the propagation of atmospheric cyclones to the Kamchatka Peninsula. The zone of intensive tidal mixing is located in the northwestern part of the Kamchatka shelf in the open part of the Shelikhov Bay. The western Kamchatka tidal mixing front which separates tidally mixed coastal water from stratified open shelf water emerges in May during the period of seasonal thermocline formation and disappears in July due to enhanced thermal stratification. The wind-driven coastal upwelling and the tidal mixing might support the high biological productivity of the western Kamchatka shelf.

Numerical characterization of thermocline behaviour of combined sensible-latent heat storage tank using brick manganese rod structure impregnated with PCM capsules

Efficient medium temperature thermal energy storage (TES) can help to eliminate the imbalance between energy demand and supply. In this study the issue of thermal ratcheting in TES system is avoided by using structured sensible heat storage material. Another technical issue of temperature drops at the end of discharging cycles occurring in only sensible material filled TES is overcome to some extent by using phase change material (PCM) between sensible rod structure (SRS) providing stable fluid outlet temperature. A comprehensive transient numerical model is formulated by solving separate equations for heat transfer fluid and storage materials using energy balance method coupled with enthalpy technique to study the influence of phase change temperature in the PCM. The numerical model predicts thermal stratification behaviour and thermocline formation along the symmetry-axis. A detailed parametric analysis of the combined sensible-latent heat thermal energy storage is performed to investigate the effect of porosity variation, inlet velocity and feature size of sensible heat storage material on total energy utilization, effective discharging efficiency and effective discharging time using thermocline characterization. The results indicate that discharging efficiency of hybrid TES tank can be increased by using lower velocity of fluid at inlet, by decreasing porosity or by using reduced SRS feature size. The study offers suggestions for optimized design and governing parameters of a new type of combined sensible-latent heat TES configuration, while avoiding thermal ratcheting with stable fluid outlet temperature for an application specific process.

Microplastic content variation in water column: The observations employing a novel sampling tool in stratified Baltic Sea

A new tool was developed for microplastics (MPs) investigation in the water column. It can collect several cubic meters of water from predefined water layers down to 100 m. The tool was tested in the Baltic Sea during the period of spring thermocline formation. Strong MPs stratification was observed at all of the sampled stations. On coastal stations (~30 m deep), stratification with high fibers content was associated with the proximity of terrestrial sources and estuarine discharges, while on off-shore stations the variability of MPs was related to vertical thermohaline structure. Mean MPs content was the 32.2 (SD 50.4) pcs/m3. Elevated MPs concentrations were observed in subsurface, near-bottom and thermohaline layers compared with intermediate layers. The heterogeneity of MPs distribution suggests that MPs particles can be retained above the density-gradient layers in coastal seas and the World Ocean.

Investigation of Stratified Thermal Storage Tank Performance for Heating and Cooling Applications

A large amount of energy is consumed by heating and cooling systems to provide comfort conditions for commercial building occupants, which generally contribute to peak electricity demands. Thermal storage tanks in HVAC systems, which store heating/cooling energy in the off-peak period for use in the peak period, can be used to offset peak time energy demand. In this study, a theoretical investigation on stratified thermal storage systems is performed to determine the factors that significantly influence the thermal performance of these systems for both heating and cooling applications. Five fully-insulated storage tank geometries, using water as the storage medium, were simulated to determine the effects of water inlet velocity, tank aspect ratio and temperature difference between charging (inlet) and the tank water on mixing and thermocline formation. Results indicate that thermal stratification enhances with increased temperature difference, lower inlet velocities and higher aspect ratios. It was also found that mixing increased by 303% when the temperature difference between the tank and inlet water was reduced from 80 °C to 10 °C, while decreasing the aspect ratio from 3.8 to 1.0 increased mixing by 143%. On the other hand, increasing the inlet water velocity significantly increased the storage mixing. A new theoretical relationship between the inlet water velocity and thermocline formation has been developed. It was also found that inlet flow rates can be increased, without increasing the mixing, after the formation of the thermocline.

Experimental investigation of single media thermocline storage with eccentrically mounted vertical porous flow distributor

This paper provides an experimental analysis of a single media thermocline storage system equipped with a perforated, eccentrically mounted, vertical and porous flow distributor. The eccentrically mounted vertical porous flow distributor allows the fluid to ooze according to the matching density. Thermocline formation and propagation during the charging cycle are analysed through multiple sets of experiments for different flow rates. It is observed that thermocline layer is thinner for higher flow rates. Lower diffusion rate at higher Peclet number leads to thinner thermocline layer. The results obtained are useful for validation and design of single tank thermocline systems. Also, it provides guidelines for flow control and operation of the charging cycle.

A Machine Learning Approach to Argo Data Analysis in a Thermocline.

With the rapid development of sensor networks, big marine data arises. To efficiently use these data to predict thermoclines, we propose a machine learning approach. We firstly focus on analyzing how temperature, salinity, and geographic location features affect the formation of thermocline. Then, an improved model based on entropy value method for the thermocline selection is demonstrated. The experiments adopt BOA Argo data sets and the experimental results show that our novel model can predict thermoclines and related data effectively.

Spring thermocline formation in the coastal zone of the southeastern Baltic Sea based on field data in 2010–2013

The transition from winter vertical mixing to the formation of the spring thermocline in the southeastern Baltic Sea is studied based on data from the hydrophysical measurements program (11 expeditions) in the Russian part of Gdansk Bay in March–June 2010, 2011, and 2013. CTD measurements were taken along the standard 18-km transect across the isobaths with a 500-m step abeam the city of Baltiysk. A set of frequently measured data was collected in a 1–2 week interval from the end of March to the beginning of May, which made it possible to analyze the transformation of the vertical thermal structure of water from inverse winter type to the summer stratification with the transition of temperature over the temperature of the density maximum. Series of repeated measurements at the deep and coastal stations as well as surface and subsurface towed measurements were carried out. The fact that lenses of freshened warmer water appear at the surface almost simultaneously with intensification of cold intrusions in intermediate (10–40 m) layers makes it possible not only to confirm the advective nature of the formation of the spring thermocline in the Baltic Sea, but also to hypothesize about the intensification of intrabasin exchange when winter-time vertical mixing ceases: the potential energy excess supported by vertical mixing in the 60-m upper quasi-homogeneous layer (UQL) of the Baltic Proper, in which the horizontal estuarine salinity gradient is significant, is converted to kinetic energy of exchange currents as the mixing process terminates. Such water dynamics makes it possible to explain the intensification of intrusions in the Baltic in spring and the formation of the cold intermediate layer due to the fast propagation of late-winter UQL water from the Bornholm Basin to the Baltic Proper. The results agree well with earlier published studies of other authors.

Effects of thermal anomalies on the growth dynamics of Dysidea avara (Porifera)

Effects of thermal anomalies on the growth dynamics of Dysidea avara (Porifera)

Seasonal patterns of cephalopod paralarvae distribution in relation to oceanographic features off South Brazil Bight (SBB)

Seasonal patterns of cephalopod paralarvae distribution in relation to oceanographic features off South Brazil Bight (SBB)

Formation of thermocline and behavior of dissolved oxygen in Lake Waku-ike

Formation of thermocline and behavior of dissolved oxygen in Lake Waku-ike

Experimental investigation of a packed bed thermal energy storage system

In this work experimental investigations on a thermal energy storage system with a solid material as storage media and air as heat transfer fluid will be presented. The experimental test rig, installed at the DIMCM of the University of Cagliari, consists of a carbon steel tank filled with freely poured alumina beads that allows investigations of heat transfer phenomena in packed beds. The aim of this work is to show the influence of the operating conditions and physical parameters on thermocline formation and, in particular, the thermal behaviour of the thermal energy storage for repeated charging and discharging cycles. Better charging efficiency is obtained for lower values of mass flow rate and maximum air temperature and for increasing aspect ratio. A decreasing influence of the metal wall with continuous operation is also highlighted. In conclusion, the analysis focuses on the thermal hysteresis phenomenon, which causes degradation of the thermocline and the reduction of the energy that can be stored by the accumulator as the repeated number of cycles increases.

The importance of year-to-year variation in meteorological and runoff forcing for water quality of a temperate, dimictic lake

<p><strong>Abstract.</strong> Natural stochasticity can pose challenges in managing the quality of the environment, or hinder understanding of the system structure. It is problematic because unfavourable stochastic events cancel management efforts and because a favourable stochastic event may overestimate perceived success. This paper presents a variance-based modelling method that can be used to quantify the extent to which natural stochasticity can affect the target environment. We use a case study of a eutrophication assessment of a Norwegian lake, Årungen, using a lake model, MyLake, in order to present the method, and to investigate how this method could assist in answering scientific and management questions. Here we contrasted two effects of nutrient loading in runoff (partially controllable by policies) and meteorology (purely natural stochastic events), illustrated in the case study, in order to achieve the season-by-season quantification of mutually confounding factors of stochastic events. The results indicate that, for example, variation in runoff volume was most prevalent during autumn and winter, while variation in phosphorus inflow was most extensive from late winter to early spring. Thermal-related properties in the lake were well predicted by the model, and showed that the time of thermocline formation varied among years by more than 1 month, from mid-April to mid-May, whereas loading was the most important factor for phytoplankton biomass and water transparency. Mild winters and greater inputs of suspended matter and phosphorus were followed by increased phytoplankton biomass and light attenuation. These findings also suggest that future changes in the global climate may have important implications for local water management decision-making. The present method of disentangling mutually confounding factors is not limited to lake water quality studies and may also provide utility in other types of aquatic system modelling.</p>