Variations In Water Temperature Research Articles

Expanded, compressed, or equal? Interactions between spawning window and stream thermal regime generate three responses in modeled juvenile emergence for Pacific salmon

Climate warming poses challenges to native fish, particularly at high latitudes. We used incubation models to explore how interactions between spawning timing and daily varying water temperature affected emergence timing for five species of Pacific salmon in 33 thermally diverse streams in south-central Alaska. Interactions between spawning timing and stream thermal regime led to three different emergence timing responses: (1) “expanded” by typically 2–3 times the duration of the spawning window for summer spawning salmon at streams with a large annual water temperature range; (2) “equal” in duration to the spawning window, regardless of spawning timing, at streams with upwelling groundwater; and (3) “compressed” for late-spawning salmon where water temperature was cooler at spawning than at emergence. Across all sites, a ±15-day range in spawning timing had influence similar to anomalously warm winters (+2 °C to +3 °C) on the emergence timing window. Differences among species, spawning timing, and thermal regimes suggest that a range of adaptations in spawning behavior will likely enable Pacific salmon populations to accommodate shifting thermal regimes during their early life history.

Flow measurement in the southern coast of the Caspian Sea

Oceanographic monitoring was conducted in the southern basin of the Caspian Sea to evaluate the physical structure of seawater and sea currents. This monitoring aimed to gather data and analyze the characteristics of the seawater, including temperature, salinity, density, and other relevant parameters. Additionally, the monitoring also focused on studying the patterns and dynamics of sea currents in the region. The collected data and analysis from this monitoring period provided valuable insights into the oceanographic conditions of the southern basin of the Caspian Sea. During storm events, a high level of correlation between the current and wind data was observed in the southern basin of the Caspian Sea during the 2017-2018 monitoring period. The measured current data indicated that the predominant directions were north (N) and northwest (NW). It was observed that strong gusts predominantly originated from the north (N) and northwest (NW) directions. Additionally, a smaller portion of the strong gusts was observed to come from the South-Southeast (S-SE) direction. These findings indicate that the prevailing wind patterns during the monitoring period were primarily from the north and northwest, with a lesser contribution from the South-Southeast direction. The current profiles observed during the monitoring period in the southern basin of the Caspian Sea were primarily influenced by the general circulation pattern of the region. This circulation pattern played a significant role in shaping the current profiles observed during the measurements. In terms of the surface current speed, the maximum recorded value was approximately 200 cm/s, which occurred in January. This indicates that there were instances of relatively high-speed currents in the southern basin of the Caspian Sea during that time. The evaluation of inter-annual variability in vertical structure and seawater temperature profiles during the monitoring period confirmed the presence of seasonal stratification in the water column of the southern basin of the Caspian Sea. This stratification was observed to consist of different layers, including the surface mixed layer, thermocline, and deep-water layers. The formation of these layers is indicative of the seasonal variations in temperature and density within the water column. The vertical changes in the water’s physical parameters during the monitoring period revealed the formation of stratification in the southern basin of the Caspian Sea. In March, it was observed that the water temperature decreased from 11.5°C at the surface to 8.5°C at a depth of 100 m, indicating the presence of a temperature gradient. As the monitoring progressed into May, the stratification became stronger, with the surface water temperature reaching around 23°C. By August, the surface layer of the sea water experienced a significant increase in temperature, reaching 29°C. These observations highlight the development of stratification and the seasonal variations in water temperature during the monitoring period in spring and summer seasons. The water temperature beneath the thermocline layer, specifically at a depth of 100 meters, was recorded to be around 8-8.5 oC. Additionally, the water salinity in the water column exhibited fluctuations between 12-12.5 (psu). Monitoring and understanding physical properties variations are crucial for assessing the oceanographic conditions and their potential impact on marine ecosystems in the southern basin of the Caspian Sea.

Soil pore water evaporation and temperature influences on clay mineral paleothermometry

Clay mineral isotope paleothermometry is fundamental to understanding Earth’s climate system and landscape evolution. Status quo methods, however, assume constant factors, such as formation temperature and water isotopic compositions, and ignore seasonality, soil water evaporation and depth-dependent temperature changes. We propose first-order modifications to address these factors and test them in a modeling framework using published data from various settings. Our forward model reveals that neglecting evaporation and seasonal soil temperature variability may lead to significant underestimations of clay formation temperatures, especially in Mediterranean settings. Our inverse model indicates that high-latitude Eocene clay formation temperatures were ~8 °C warmer than modern, while Eocene river sediments in the Sierra Nevada show evaporation-influenced trends, suggesting that previous paleoelevation estimates were underestimated. Our framework demonstrates that explicit consideration of soil pore water evaporation and temperature variability is necessary when interpreting clay mineral isotope data in the context of temperature, hydroclimate and elevation reconstructions.

The impact of extreme heat on lake warming in China

Global lake ecosystems are subjected to an increased occurrence of heat extremes, yet their impact on lake warming remains poorly understood. In this study, we employed a hybrid physically-based/statistical model to assess the contribution of heat extremes to variations in surface water temperature of 2260 lakes in China from 1985 to 2022. Our study indicates that heat extremes are increasing at a rate of about 2.08 days/decade and an intensity of about 0.03 °C/ day·decade in China. The warming rate of lake surface water temperature decreases from 0.16 °C/decade to 0.13 °C/decade after removing heat extremes. Heat extremes exert a considerable influence on long-term lake surface temperature changes, contributing 36.5% of the warming trends within the studied lakes. Given the important influence of heat extremes on the mean warming of lake surface waters, it is imperative that they are adequately accounted for in climate impact studies.

Two-stage stochastic robust optimization scheduling of electric–thermal microgrid with solid electric thermal storage

During the periods of high heat load (HL) demand in winter, the increased heat output of combined heat and power units (CHPs) can significantly compress the electric power regulation range, thereby posing a threat to the safety of the power system. The solid electric thermal storage (SETS) can be employed as the regulating resource for both electric and thermal systems, expanding the dispatch space of microgrids to promote renewable energy consumption. In this paper, a two-stage stochastic robust optimization scheduling model of an electric–thermal microgrid with SETS is proposed, and the electric–thermal bi-directional regulation characteristics of SETS are considered. First, a SETS operation model based on the heat transfer characteristics of the homogeneous material-type thermal storage unit is established. Second, a regional thermal inertia model under a constant-flow variable-temperature system is established, which integrates HL at different locations to the heat source, avoiding the calculation of variation in water temperature, thus reducing the calculation difficulty. Finally, the two-stage stochastic robust optimization scheduling model of an electric–thermal microgrid with SETS is established. The model decouples the power and heat generation of CHP through the bi-directional regulation function of SETS. Case studies demonstrate the validity and effectiveness of the proposed scheduling model.

Plane heating with a transparent heater film in a fish tank

The water temperature in a fish tank is important for fish health. A conventional aquarium heater produces localized heating that causes water temperature variation, resulting in thermal stress to fish. This study presents plane heating with a transparent heater film that is aesthetically attractive when applied to fish tanks. The transparent heater film comprises a metal mesh with an optical transparency of 81 %, sheet resistance of 0.6 Ω/□, and mean heating surface temperature of 57 °C at 20 W. In the test setup, 100 W is applied to compare an aquarium heater and a transparent heater film. Increasing the water temperature from 23 °C to 24 °C at the center of the fish tank needs 28 min with the transparent heater film operating at 33 °C, whereas the same temperature increase needs 50 min with an aquarium heater operating at 49 °C. The planar heater thus results in enhanced heat diffusion and reduced water temperature variation due to its extended heating surface area.

Влияние погодных условий на процесс массового развития цианобактерий в Куйбышевском водохранилище

According to observation data in the summer period 2016-2021. The interannual variability of weather conditions, water temperature and chlorophyll (Chl) content in the Kuibyshev Reservoir was considered. Regular observations were carried out at the outlet section of the reservoir (Zhigulevsky hydroelectric complex) under conditions of complete mixing of water masses. It has been established that the main factors influencing the process of mass development of cyanobacteria (MDC) are thermal regime and weather conditions. With increasing water temperature, the interval and degree of favorable activity of cyanobacteria increases. Over a 6-year period, the average interval was 44 days, the largest was 72 days, and the smallest was 11 days. The degree of favorability varied widely: from low (23 °С ˃ t ˃ 22 °С) to extreme high (t ˃ 26 °С). The most favorable years for the MRC process were 2016 and 2021, when the Chl content during the summer period was 6.2 and 7.2 μg/dm3, respectively. The least favorable years were 2017 and 2019, when the Chl content during the summer period was 0.6 and 1.4 μg/dm3, respectively. Seasonally, the temperature optimum was observed annually in July. The Chl content in July 2021 was 12.6 μg/dm3, and in the cold July 2017 – 0.7 μg/dm3. Significant variability of the MRC process is due to synoptic cyclicity and changing weather conditions. The established influence of thermal regime and weather conditions on the content of chlorophyll suggests that in conditions of global warming, the process of mass development of cyanobacteria is expected to intensify, which will negatively affect the ecological state and water quality of the Kuibyshev Reservoir.

Effect of Intake Conditions and Combustion Factors on Gasoline and Diesel Engines Performance and Exhaust Emissions

The study aimed to investigate the effects of intake conditions, including water injection, filter presence, and temperature variations, on the performance of petrol and diesel engines. The experiment was conducted on single-cylinder four-stroke engines at varying speeds and loads. The composition of the exhaust emissions was analyzed to determine the combustion method. The results indicated that injecting a mixture of water and air into the engine inlet could reduce engine emissions by 17-33% and exhaust temperature by 13-35% for both engines. When an air filter and water injection were present, air flow restrictions in the air inlet led to better combustion and less unburned mixture due to increased air availability. The study also investigated the impact of combustion parameters on heat generation and emissions inside the combustion chamber of gasoline and diesel engines. The parameters studied included intake temperature, intake pressure, equivalence ratio, compression ratio, engine speed, turbulence kinetic energy, and combustion chamber design. The test results showed that higher intake temperatures lead to increased heat generation, increased overall engine efficiency, and reduced CO2 and NOx emissions in gasoline engines. Increasing the value of the parity ratio also led to improved overall efficiency of the two engines.

High water temperature significantly influences swimming performance of New Zealand migratory species.

Anthropogenic structures in freshwater systems pose a significant threat by fragmenting habitats. Effective fish passage solutions must consider how environmental changes introduce variability into swimming performance. As temperature is considered the most important external factor influencing fish physiology, it is especially important to consider its effects on fish swimming performance. Even minor alterations in water properties, such as temperature and velocity, can profoundly affect fish metabolic demands, foraging behaviours, fitness and, consequently, swimming performance and passage success. In this study, we investigated the impact of varying water temperatures on the critical swimming speeds of four migratory New Zealand species. Our findings revealed a significant reduction in critical swimming speeds at higher water temperatures (26°C) compared to lower ones (8 and 15°C) for three out of four species (Galaxias maculatus, Galaxias brevipinnis and Gobiomorphus cotidianus). In contrast, Galaxias fasciatus exhibited no significant temperature-related changes in swimming performance, suggesting species-specific responses to temperature. The cold temperature treatment did not impact swimming performance for any of the studied species. As high water temperatures significantly reduce fish swimming performance, it is important to ensure that fish passage solutions are designed to accommodate a range of temperature changes, including spatial and temporal changes, ranging from diel to decadal fluctuations. Our research underscores the importance of incorporating temperature effects into fish passage models for habitat restoration, connectivity initiatives, and freshwater fish conservation. The influence of temperature on fish swimming performance can alter migration patterns and population dynamics, highlighting the need for adaptive conservation strategies. To ensure the resilience of freshwater ecosystems it is important to account for the impact of temperature on fish swimming performance, particularly in the context of a changing climate.

Temporal partitioning of Chironomidae emergence in an insular, tropical rainforest stream

Annual water temperature variation strongly influences larval growth of aquatic insects in streams located in temperate regions or at high elevations, which produces cohorts with highly synchronized emergence periods and short average annual durations of emergence. Studies of Chironomidae in tropical streams indicate that species in these habitats have longer average durations of emergence due to reduced annual variation in water temperature. We used emergence trap data collected over one year from Quebrada Prieta (El Verde Field Station, Puerto Rico) to test the prediction that chironomids of an insular rainforest stream should have longer average annual durations of emergence than chironomids in both temperate streams and mainland streams in continental tropical regions. Taxa richness was relatively low with twenty-eight Chironomidae taxa collected from Quebrada Prieta. Emergence patterns of the most common taxa demonstrated some seasonally with the highest emergence generally occurring during the dry season (January through April). The estimated average emergence duration of Chironomidae in Quebrada Prieta was 205 days/species/year, which was greater than estimates of average durations for chironomids of three streams in Pennsylvania, USA (70 days/species/year), 6 streams in Minnesota, USA (89 days/species/year), and four streams in Guanacaste National Park in northwestern Costa Rica (116 days/species/year). The emergence duration for the chironomid community in Quebrada Prieta was most similar to another tropical, mountain stream in the Democratic Republic of the Congo (255 days/species/year). Although many taxa emerged throughout the one-year sampling period, some taxa in Quebrada Prieta had distinct emergence peaks. This demonstrates that although environmental conditions are stable enough to allow for emergence throughout the year for many species, there is some seasonality in the development of chironomid taxa in this tropical stream. These results are consistent with predictions that invertebrates in tropical streams will have longer, less synchronous emergence periods than species in temperate regions with high annual fluctuations in temperature. However, this research is also similar to several other studies that have identified seasonal emergence peaks in tropical chironomids which demonstrates a need to better understand the exogenous cues that affect these patterns.

Interannual variability of ice cover across Davis Strait and the Labrador Sea for the period from 1979 to 2023

In conditions of rapid development of trade and transport communications, the issue of navigation through ice regime zones became of greater importance. In particular, reduction of the area of ice cover in the Canadian Arctic because of global warming opens up favourable prospects for further development of maritime shipping in this zone. Considering that the routes through the Northwest Passage are the shortest ones of all the routes connecting the Atlantic and Pacific oceans, it is clear that all aspects of this topic are of great importance and relevance. This especially applies to the aspects dedicated to studying the characteristics of appearance, formation, concentration, physical characteristics, trajectory of ice movement and forecasting the area of the ice cover in a given zone, i.e. the characteristics affecting the conditions of ice navigation and serving as determining factors in terms of navigation safety.
 The research examines some of these issues, namely the spread of the ice cover during the period of its maximum formation across Davis Strait and the Labrador Sea (where the routes through the Northwest Passage start) and the establishment of statistical relations between the ice spread and the temperatures of surface water and surface air. The research method to be used: synoptic-climatic and statistical analysis of numerical series of ice cover deviations from its average limit as of April 15 over the period of 1979-2023 within the zone in study.
 Based on the set goal, the study processed raw data on distribution of ice cover across Davis Strait and the Labrador Sea for the period of 1979-2023 and completed its statistical analysis. The results of the analysis showed presence of a statistically significant negative trend and cyclical fluctuations with periods of 3-6, 9, 10 and 13 years in relation to the interannual variability of ice cover distribution for the studied period. Positive trends are also observed in the interannual variability of surface water temperature and surface air temperature. After bringing the original series to a quasi-stationary form, a correlation analysis of the relationships between the ice cover distribution and the temperature of water and air was carried out. The results of the analysis determined zones and points with statistically significant correlation coefficients between them during the year. It turned out that the highest values of coefficients are observed from December to March, and the maximum one occurs in March.
 Systematization and analysis of the ice field across Davis Strait and the Labrador Sea during the period of maximum development made it possible to establish that the spread of ice between 60° and 55° north parallels was the most stable during the studied period, and the least stable was observed in the area below 55° north parallel.
 The results of the conducted research open up prospects for development of methods for forecasting the distribution of ice cover across Davis Strait and the Labrador Sea. This will make ice navigation in this area safer.

Water quality impact on flotation Response: A focus on specific ions and temperature

Plant water recycling causes an accumulation of ions in the process water which may affect plant processes since processing routes are water intensive. Seasonal temperature differences affect the water quality through variation of the available recycled water within the plant between the summer and winter seasons. The objective of this study was therefore to investigate the effect of specific ions and temperature, relevant to onsite process water recycling and temperature variations brought about by seasonal changes, on the separation of gangue from valuable minerals in batch flotation of a low-grade Cu-Ni-PGE ore. Water and solids recoveries were impacted by Ca2+ and SO42-. At high SO42- concentrations, an increase in Ca2+ increased the mass of water and solids recovered. An increase in SO42- alone caused an increase in copper recovery whilst decreasing the copper grade. S2O32- alone affected the nickel recovery. An increase in S2O32- caused an increase in nickel recovery whilst the nickel grade was affected by the interaction of S2O32- and temperature. Furthermore, copper showed similar trends as those observed for nickel in the responses for the mineral grade. At high S2O32- concentration there was no observable change in the nickel and copper grades when temperature increased. At low S2O32- concentrations, an increase in temperature decreased the nickel and copper grades. In addition to the interactive effect of temperature and S2O32-, nickel was more temperature sensitive in comparison to copper. The study demonstrated that there are specific ion concentration ranges beyond which flotation performance was adversely affected and other ranges beyond which no observable effect on flotation was visible. Based on this understanding, it may be possible to predict the ideal operating conditions for the number of water recycles in a plant. The higher ionic concentrations and their corresponding ionic strengths resulted in a more stable froth in comparison to lower ionic concentrations and consequently an improvement in the recoveries.

Experimental Analysis of the Dual Source Heat Pump with Varying Water Temperature

Purpose: The aim is to examine how water temperature influence the coefficient of performance (COP) of a dual-source heat pump (DSHP) and to show how water temperature influence the relationship between heating capacity and power consumption of the DSHP. Methods: An experimental method to examine an installed 5kW DSHP system with an attached converters and other connected components, which arrangement properly controls for the indoor temperature and relative humidity of the laboratory. Results and Conclusions: The findings reflects that the COP of the DSHP pumps increases at low water temperature. As water temperature increases, the heat loss to water and compressor power consumption decreases, and in turn reduce the COP. The average temperature increases from 36.55oC to 59.15oC and COP reduces, by 40%, from 2.83–1.12. Implications: The implication is that the DSHP which is shown to be energy efficient is environmentally friendly, and as a result, would remain very useful in the fifth generation of heating systems with the use of smart technology in future. Originality/Value: The value of the article lies in its focus on the performance of the DSHP as an energy and efficiency device for in heating and cooling in buildings.

Control strategies and performance analysis for a novel nuclear heating system with heat storage

A nuclear heating system integrated with a heat storage tank (HST-NHS) is a promising technical solution for countries with large-scale heating demand. HST-NHS can greatly curtail carbon dioxide emissions and contribute to sustainable development. Appropriate control strategies are not only crucial to realize the real-time matching between HST-NHS heat supply and heat demand, but also ensure the stable and safe operation of HST-NHS. Until now, control strategies for HST-NHS have received limited attention. A refined dynamic simulation model for HST-NHS is established based on APROS software. The verification of the built model in steady state and transient state is completed. Two basic control strategies for the primary heating network (PHN) of HST-NHS, constant supply water temperature and variable flow rate (CT-VF) and variable supply water temperature and constant flow rate (VT-CF) are presented in detail. Based on various typical working conditions of a central heating region in Liaoyuan City, the control effects of two control strategies are investigated. Additionally, a comprehensive performance comparison between the two strategies is explored. Simulation results indicated that under the two control strategies, the indoor temperature can be effectively controlled at a high comfort level. During the same typical day, the total energy consumption cost under the VT-CF control strategy is 0.5 × 105 yuan lower than that under the CT-VF control strategy.

Numerical analysis of the heat and mass transfer process in absorbers using water and lithium bromide

This study aimed to simulate the heat and mass transfer process of a spiral tubular Lithium Bromide/Water (LiBr/H2O) absorber based on a non-linear mathematical model developed in MATLAB program, using an iterative numerical method and experimental data from the literature for calibration and validation. For this, the absorber was simplified as a descending film flat plate and the simulation considered three different cases of cooling water temperature variation: 21.5°C, 23.5°C, 25.6°C. The effective mass transfer coefficient, Kef, was obtained from the literature, and the overall heat transfer coefficient, U, was calculated using the overall thermal resistance within the absorber. The distributions for the temperature and concentration of the solution and cooling water, obtained by the model, showed good agreement when compared to the literature. It was found that the heat and mass transfer increased when varying the absorber length up to 14.25 m, and from this value on, they remained nearly constant. Increasing the mass flow rate of the cooling water inlet decreases the temperature and concentration of the LiBr/H2O. In addition, copper and aluminum proved to be more suitable for use in the absorber tube than stainless steel.

Effects of winter water quality conditions on Atlantic Salmon embryo mortality and deformity rates in the Serpentine River (New Brunswick, Canada)

In-stream incubation of Atlantic Salmon (Salmo salar) embryos within artificial redds using Jordan/Scotty fish egg incubator boxes is an alternative to traditional hatchery-based incubation methods. Winter water quality conditions, such as temperature and dissolved oxygen vary within natural redds and influence wild embryo development and survival. The differences in landscape characteristics and in-stream habitat features at catchment-, reach-, and site spatial scales were investigated to determine how they influenced water quality conditions within the Serpentine River, New Brunswick. A total of 14,400 hatchery-fertilized salmon embryos were incubated within river substrates from November 2020 to January 2021. The proportion of embryo mortalities within our experiment was high (44.9%), but still within the range observed in the literature from other incubation experiments, and the proportion of embryo deformities between our sites was very low (2.7%). Despite variations in average water temperature, cumulative degree days, and coefficient of variation in dissolved oxygen (DO) concentration, none were statistically significant for explaining embryo mortalities or deformities. Patterns were, however, evident across sites showing trends towards a decrease in mortality with cumulative degree days, and an increase in deformities with greater variation in DO. Improving our knowledge on Atlantic Salmon incubation habitat supports future research and restoration opportunities for adaptation under a changing climate.

Concrete with clinker‐efficient cements ‐ Robustness to variations in water content and temperature

AbstractThe use of multi‐component cements (CEM II‐CEM VI), which contain main constituents other than Portland cement clinker in significant quantities, can significantly help to reduce the CO2 footprint of the cement or concrete industry. Clinker‐efficient cements (CEM II/C‐M) have been standardized in the current version of DIN EN 197‐5. In a systematic experimental program, the influence of water content variations and temperature on the robustness of concrete with clinker‐efficient cements with high contents of granulated blast furnace slag or fly ash and limestone (CEM II/C‐M (S‐LL) and CEM II/C‐M (V‐LL)) was studied. As a reference, concretes representative for construction elements used indoor (XC1) or in protected outdoor environment (XC3) with standard Portland composite cement (CEM II/A‐M) and blast furnace slag cement (CEM III/A) were investigated. The influence of variations in water content and temperature on fresh (rheological properties, bleeding) and mechanical concrete properties (compressive strength, elastic modulus) were investigated. The results obtained show similar performance and robustness of such concretes with clinker‐efficient cements compared to the reference concretes.

Gene expression patterns of Salpa thompsoni reveal remarkable differences in metabolism and reproduction near the Antarctic Polar Front.

Salpa thompsoni is an important grazer in the Southern Ocean and most abundant in the Antarctic Polar Front (APF) region. During recent decades, their distribution expanded southwards. However, it is unclear whether salps can maintain their populations in the high Antarctic regions throughout the year owing to a poor understanding of their physiological responses to changing environmental conditions. We examined gene expression signatures of salps collected in two geographically close regions south of the APF that differed in water mass composition and productivity. The observed differences in the expression of genes related to reproductive, cellular and metabolic processes reflect variations in water temperature and food supply between the two regions studied here. Our study contributes to a better understanding of the physiological responses of S. thompsoni to changing environmental conditions, and how the species may adapt to a changing environment through potential geographical population shifts under future climate change scenarios.

Seasonal and Inter-Annual Variability of Water Temperature in Petrozavodsk Bay of Lake Onega

Abstract—Based on year-round measurements of water temperature at an autonomous station (an anchored chain equipped with temperature sensors), the features of the temperature and ice regimes of the Petrozavodsk Bay of Onega Lake in modern climatic conditions were studied; the dates and duration of the main hydrological phenomena in the water area of the bay were specified. In the abnormally warm winter of 2019–2020, the water area of the Petrozavodsk Bay was not completely covered with ice for the first time in a long period of observations; in the area of the measurement station, ice fields were observed from late January to mid-March. The duration of ice-covered period in the next two winters was 3.5 and 5 months. Data were obtained on the timing of the onset and duration of the spring under-ice convection, a phenomenon that plays an important role in the thermal regime of the lake at the end of winter. It is shown that 2016, 2021 and 2022 spring under-ice convective mixing lasted 4–6.5 weeks, covering the entire water column by the end of ice period. Mixing of the water column after breaking the ice (spring homothermy) continued for another 3–4 weeks. In the spring of 2020, under-ice convection was not observed; spring overturn continued for two months from mid-March to mid-May. The dates of the upward transition of water temperature through 4°C in the years of measurements (5–19 May) were ahead of the long-term average by 2–3 weeks (end of May). Thermal stratification was established from 12 to 27 May and existed for 3–3.5 months. Complete mixing of the water mass of the bay took place in late August–early September, and then, until ice settling, the water column cooled in a state of homothermy. Immediately before ice formation, the water temperature dropped to very low values and did not exceed 0.1°С in the water column. The period with an average daily water temperature of the surface layer of the Petrozavodsk Bay above 10°C lasted from 121 to 144 days during the years of measurements.

Resolution and trade-offs in global anelastic full-waveform inversion

Summary Improving the resolution of seismic anelastic models is critical for a better understanding of the Earth’s subsurface structure and dynamics. Seismic attenuation plays a crucial role in estimating water content, partial melting, and temperature variations in the Earth’s crust and mantle. However, compared to seismic wavespeed models, seismic attenuation tomography models tend to be less resolved. This is due to the complexity of amplitude measurements and the challenge of isolating the effect of attenuation in the data from other parameters. Physical dispersion caused by attenuation also affects seismic wavespeeds, and neglecting scattering/defocusing effects in classical anelastic models can lead to biased results. To overcome these challenges, it is essential to account for the full 3D complexity of seismic wave propagation. Although various synthetic tests have been conducted to validate anelastic Full-Waveform Inversion (FWI), there is still a lack of understanding regarding the trade-off between elastic and anelastic parameters, as well as the variable influence of different parameter classes on the data. In this context, we present a synthetic study to explore different strategies for global anelastic inversions. To assess the resolution and sensitivity for different misfit functions, we first perform mono-parameter inversions by inverting only for attenuation. Then, to study trade-offs between parameters and resolution, we test two different inversion strategies (simultaneous and sequential) to jointly constrain the elastic and anelastic parameters. We found that a sequential inversion strategy performs better for imaging attenuation than a simultaneous inversion. We also demonstrate the dominance of seismic wavespeeds over attenuation, underscoring the importance of determining a good approximation of the Hessian matrix and suitable damping factors for each parameter class.