Winter Water Research Articles

Technical note: Determining Arctic Ocean halocline and cold halostad depths based on vertical stability

Abstract. The Arctic Ocean halocline separates the cold surface mixed layer from the underlying warm Atlantic Water (AW), and thus provides a precondition for sea ice formation. Here, we introduce a new method in which the halocline base depth is determined from vertical stability and compare it to two existing methods. We also propose a novel method for detecting the cold halostad, a layer characterized by a small vertical salinity gradient, which is formed by the Pacific Winter Water in the Canada Basin or by meltwater off the eastern coast of Greenland and off Svalbard. Our main motivation for determining the halocline base depth depending on vertical stability was that vertical stability is closely related to vertical mixing and heat exchange. Vertical stability is a crucial parameter for determining whether the halocline can prevent vertical heat exchange and protect sea ice from warm AW. When applied to measurements from ice-tethered profilers, ships, and moorings, the new method for estimating the halocline base depth provides robust results with few artifacts. Analyzing a case in which water previously homogenized by winter convection was capped by fresh water at the surface suggests that the new method captured the beginning of new halocline formation in the Eurasian Basin. Comparatively large differences between the methods for detecting the halocline base depth were found in warm AW inflow regions for which climate models predict halocline thinning and increased net surface energy fluxes from the ocean to the atmosphere.

Alternative method for determining available winter water volumes from lakes to support small-scale projects

Abstract In Canada's Northwest Territories (NT), industrial activities conducted during the winter, such as ice road construction and exploratory drilling, require the use of water from ice-covered water bodies. Withdrawal in excess of 10% of available under-ice volume can threaten fish habitat or other users. The Land and Water Boards (LWBs) of the Mackenzie Valley require water licences for water withdrawal beyond regulated thresholds. Applicants must provide information including identification and location of proposed water sources, timing and proposed volume of water and winter water withdrawal must be limited to <10% of available volume to protect fish habitat under the ice. Many applicants are at early project stages and the necessary information on bathymetry and volumes of water is not readily available or requires expertise and effort that may not be feasible at the early stages of smaller projects. This paper describes the alternative method for determining available winter water volumes from lakes to support small-scale projects. A simple formula of ‘allowable volume (m3) = surface area (m2) * 0.1 m’ was developed and tested to provide a conservative estimate of under-ice volumes from easily available data which is protective in spite of uncertainties inherent in limited data.

Spatiotemporal evolution of dissolved organic matter (DOM) and its response to environmental factors and human activities.

The South-to-North Water Diversion East Project (SNWDP-E) is an effective way to realize the optimal allocation of water resources in China. The North Dasha River (NDR) is the reverse recharge section that receives water from the Yufu River to the Wohushan Reservoir transfer project line in the SNWDP. However, the dissolved organic matter (DOM) evolution mechanism of seasonal water transfer projects on tributary waters has not been fully elucidated. In this paper, the NDR is the main object, and the changes in the composition and distribution of spectral characteristics during the winter water transfer period (WT) as well as during the summer non-water transfer period (NWT) are investigated by parallel factor analysis (PARAFAC). The results showed that the water connectivity caused by water transfer reduces the environmental heterogeneity of waters in the basin, as evidenced by the ammonia nitrogen (NH4+-N) and total phosphorus (TP) in the water body were significantly lower (p<0.05, p<0.01) during the water transfer period than the non-water transfer period. In addition, the fluorescence intensity of DOM was significantly lower in the WT than the NWT (p<0.05) and was mainly composed of humic substances generated from endogenous sources with high stability. While the NWT was disturbed by anthropogenic activities leading to significant differences in DOM composition in different functional areas. Based on the redundancy analysis (RDA) and multiple regression analysis, it was found that the evolution of the protein-like components is dominated by chemical oxygen demand (COD) and NH4+-N factors during the WT. While the NWT is mainly dominated by total nitrogen (TN) and TP factors for the evolution of the humic-like components. This study helps to elucidate the impact of water transfer projects on the trunk basin and contribute to the regulation and management of inter-basin water transfer projects.

Investigation on overall energy performance of a novel multi-functional PV/T window

PV windows are considered to be a promising building-integrated PV technology due to their excellent electrical, daylighting and thermal performance. However, the shading of the PV cells increases the heating load in winter and the high temperature of PV cells exacerbates the cooling load in summer. Moreover, a significant portion of the heat absorbed by the PV modules is usually wasted. To address these issues, this paper proposed a multi-functional PV/T window. This system could recover the heat on PV cells for producing warm air in winter and hot water in other seasons. As a result, the proposed system can realize the combined PV/T utilization of solar energy and reduce the seasonal thermal needs of the building. First, the mathematical model of the proposed window was developed and validated. Next, the developed model was integrated into building energy software to evaluate the overall energy performance of the proposed window in four different cities of Yangtze River region: Shanghai, Nanjing, Wuhan, and Chongqing in China. These cities experience the subtropical humid climate (Cfa in the Köppen-Geiger classification) and belong to the zones with medium global horizontal irradiation. The sensitivity analysis revealed that the optimal slat angles are between 0o and 40o, while the optimal orientation angles range from 30o to 60o. Selecting low-iron glass as the inner glass resulted in the lowest overall energy consumption. By adopting the MFPV/T window, the annual operation cost of the studied case could be reduced by 34% (6.4 $/m2), 36% (7.0 $/m2), 28% (5.7 $/m2), and 16% (2.9 $/m2) in these four cites, respectively. Additionally, the annual CO2 emissions could be curtailed by 53.5, 58.5, 47, and 22.3 kg/m2, respectively.

Variations in the dairy wastewater properties and bacterial diversity of each unit in membrane-enclosed anaerobic lagoon treatment process in Heilongjiang Province

In order to meet the land use requirements of the treated wastewater from high density polyethylene (HDPE) membrane-enclosed anaerobic lagoons, the physical and chemical properties of the wastewater in an HDPE membrane-enclosed anaerobic lagoon were measured. The total nitrogen content (TN) in wastewater treated in membrane-enclosed anaerobic lagoons is 3165 and 1510 mg/L in winter and summer respectively. The wastewater can be used as liquid organic fertilizer, partly replacing chemical fertilizer. The safety dosage of the wastewater was 21.48 t/ha for rice and 9.54 t/ha for corn, respectively. Meanwhile, the wastewater has the characteristics of high salt (conductivity>16.0 mS/cm) and high organic matter content (COD>16,900 mg/kg). Therefore, the potential negative effects of the wastewater on soil salinity and pH should be assessed. 16S rRNA was used to investigate the bacterial population structure and assess potential biological risks of land use of the wastewater. The wastewater from lagoon has the least and the most bacterial abundance in summer and winter, respectively. The bacterial diversity of wastewater samples from lagoon is the most. 21 and 24 phyla were detected in winter and summer samples respectively. Clostridium is the absolute dominant bacteria in the summer water samples and the absolute dominant bacteria is Trichococcus in winter water samples. Several animal and plant bacterial pathogens such as Campylobacter, Corynebacterium, Facklamia and Erysipelothrix can be detected in the wastewater samples. More than 70% of pathogenic bacteria such as Campylobacter, Facklamia, Erysipelothrix and Acholeplasma can be removed by lagoon in summer, but only about 99% of Corynebacterium is still in the lagoon (XYH). While more than 60% of Corynebacterium, Facklamia and Erysipelothrix are not removed in winter. So the biological risk of land use of anaerobic pond wastewater needs to be considered.

Ecosystem and Commercializing of Fish in a Rich-Minerals, Low-Salinity Closed Lake

Wadi El Natrun is an elongated narrow depression in the Western Desert of Egypt. The depression characterized by many ancient alkaline salt lakes. These lakes are filled with water in winter and dried up in summer. Recently, some lakes become permanently dried, while others become submerged throughout the year as El Bieda Lake. El Bieda Lake has undergone ecological changes due to the prolonged extraction of minerals and the continual discharging of freshwater. This study investigates the recent biotic and abiotic changes of this lake and discusses its fisheries opportunities. The lake’s water is well-oxygenated, rich with different inorganic nutrients, and characterized by a low salinity. Sodium and chloride ion concentrations are lower than the equivalent surface seawater, while magnesium, calcium, potassium, sulfate, and bicarbonate ions are higher. The lake has low plankton species richness with high biomass and high nutritional values. More recently, two cichlid species, Oreochromis aureus and Coptodon zillii, have colonized the lake. Summer characterized by a very low mortality for Oreochromis aureus and a poor representation of Coptodon zillii. However, both species shared the catch the rest of the year. The high biomass and nutritional quality of plankton communities, as well as the dense phytobenthic film, indicate that the lake is currently below its carrying capacity. The well-oxygenated water, high biomass of plankton and phytobenthic diatoms, and the expected changes in salinity suggest that introducing the euryhaline, commercially valuable, and fast-growing Mugil cephalus or Chelon ramada in El Bieda Lake is highly advisable.

Changes in energy balance and total evaporation with age, and between two commercial forestry species in South Africa

Expansion of the area planted to eucalypts has been observed in the last two decades due to an improvement in markets for products from this tree species. This has raised concerns over the management of freshwater resources as other species are replaced by Eucalyptus, which has been shown to use more water than other commercial forestry species. The energy balance (EB) and total evaporation (ET) over Acacia mearnsii was previously monitored at the Two Streams research catchment, and the site harvested in 2018 with subsequent re-planting of E. dunnii. This presented an opportunity to measure the two-year-old E. dunnii (Edun2) EB and ET for comparison on the same site with the previously planted A. mearnsii with results from two-year-old A. mearnsii (Amear2) and six-year-old A. mearnsii (Amear6) crops. ET and EB measurements on Amear2 were obtained using a large aperture scintillometer, while eddy covariance was used for Amear6 and Edun2. Measurements were conducted in October 2007 to September 2008, October 2012 to September 2013 and October 2019 to September 2020 for Amear2, Amear6 and Edun2. The leaf area index (LAI) was measured using a LAI 2200 plant canopy analyser for all crops. The annual plantation water productivity (PWPWOOD) was calculated as a ratio of productive stand volume to ET for Amear2, Amear6 and Edun2. Results showed that latent energy fluxes dominated the EB in all crops for both summer and winter seasons, indicating a possibility that trees were not limited by plant available water in winter (dry season). The Edun2 and Amear2 annual ET was statistically (p > 0.05) similar, while ET of the younger crops (Amear2 and Edun2) was 12% greater than Amear6. High ET in Edun2 was caused by high LAI while Amear2 was caused by high transpiration per unit leaf area in young trees than in mature trees. Monthly crop factors were derived from FAO ETo and ET for all three crops, providing a convenient and transferable method of estimating ET from meteorological data over a large scale. The Edun2 PWPWOOD was greater than Amear2, while Amear6 was greater than both the young crops. This study provides insight into the total water-use by different species at different stages of growth at the same site. It is recommended that catchment water balance measurements be continued on the current E. dunnii crop for the full crop rotation to assess the long-term impact of E. dunnii on streamflow.

Relationship between environmental conditions and biennial growth of kelp Saccharina japonica var. ochotensis, northern Hokkaido, Japan

The kelp Saccharina japonica var. ochotensis occurs in the northern Sea of Japan. A monthly diving survey was conducted at two sampling stations, Tsugaru in Rebun Island and Hourai in Wakkanai district in northern Hokkaido, Japan, from March 2013 to November 2014. Oceanographic conditions, water temperature, nitrate, and irradiance were recorded, and several differences were observed between Tsugaru and Hourai. Higher irradiance at Tsugaru during July and August led to enhanced photosynthesis by sporophytes, and the lower temperature in this area led to increased storage of mannitol from April to September, with more sulfated polysaccharide in sporophytes and greater blade thickness compared to kelp specimens at Hourai. Higher water temperatures in Tsugaru during September and February led to larger sporophytes, whereas lower winter water temperatures in Hourai led to smaller sporophytes. Higher water temperatures from September to February and lower nitrate concentrations throughout the year except in April 2013 and March 2014 in Tsugaru were associated with higher sorus formation rates and lower regeneration (transition from annual to biennial sporophytes) rates than at Hourai. Irradiance at Tsugaru was higher than at Hourai from July to August. Lower temperatures and lower radiation result in a lower rate of sorus formation; whereas higher nitrate concentrations give rise to higher rates of regeneration.

Vertical Convergence of Turbulent and Double-Diffusive Heat Flux Drives Warming and Erosion of Antarctic Winter Water in Summer

Abstract The seasonal warming of Antarctic Winter Water (WW) is a key process that occurs along the path of deep water transformation to intermediate waters. These intermediate waters then enter the upper branch of the circumpolar overturning circulation. Despite its importance, the driving mechanisms that mediate the warming of Antarctic WW remain unknown, and their quantitative evaluation is lacking. Using 38 days of glider measurements of microstructure shear, we characterize the rate of turbulent dissipation and its drivers over a summer season in the northern Weddell Sea. Observed dissipation rates in the surface layer are mainly forced by winds and explained by the stress scaling (r2 = 0.84). However, mixing to the base of the mixed layer during strong wind events is suppressed by vertical stratification from sea ice melt. Between the WW layer and the warm and saline circumpolar deep water, a subsurface layer of enhanced dissipation is maintained by double-diffusive convection (DDC). We develop a WW layer temperature budget and show that a warming trend (0.2°C over 28 days) is driven by a convergence of heat flux through mechanically driven mixing at the base of the mixed layer and DDC at the base of the WW layer. Notably, excluding the contribution from DDC results in an underestimation of WW warming by 23%, highlighting the importance of adequately representing DDC in ocean models. These results further suggest that an increase in storm intensity and frequency during summer could increase the rate of warming of WW with implications for rates of upper-ocean water mass transformation. Significance Statement Around Antarctica, the summer warming of the subsurface cold Antarctic Winter Water feeds the upper layer of the overturning circulation. This study aims to quantify the mechanisms that mediate the warming of Antarctic Winter Water. Our results reveal that the observed warming of this layer can be explained by both surface wind-driven mixing processes as well as double-diffusive convection occurring beneath the Winter Water layer. Understanding the role of these mechanisms is important for understanding the regions upper-ocean heat distribution, the rates of water mass transformation and how they might respond to changes in sea ice, stratification, and the overlying large-scale winds.

Revisiting hydro-ecological impacts of climate change on a restored floodplain wetland via hydrological / hydraulic modelling and the UK Climate Projections 2018 scenarios

The hydro-ecological impacts of 40 UK Climate Projections 2018 scenarios on a restored lowland England river floodplain are assessed using a MIKE SHE / MIKE 11 model. Annual precipitation declines for 60% of scenarios (range: -26%–21%, with small, <5%, declines for the central probability level). Potential evapotranspiration increases for all probability levels except the most extreme, very unlikely, 10% level (range: -4%–43%, central probability 9%–20%) Mean, peak and low river discharges are reduced for all but the extreme 90% probability level. Reduced frequency of bankfull discharge dominates (at least halved for the central probability level). Floodplain inundation declines for over 97% of 320 scenario-events. Winter water table levels still intercept the surface, while mean and summer low levels are reduced. Declines in mean summer floodplain water table levels for the central probability level (0.22 m and 0.28 m for the 2050s and 2080s, respectively) are twice as large as those in the more dynamic riparian area. Declines reach 0.39 m for some 10% probability level scenarios. Simulated hydrological changes differ subtly from a previous assessment using earlier UK climate projections. A soil aeration stress index demonstrates that, under baseline conditions, prolonged high winter floodplain water tables drive long periods of low root-zone oxygen, in turn favouring vegetation communities adapted to waterlogged conditions. Climate change reduces aeration stress and the extent of appropriate conditions for these plant communities in favour of communities less tolerant of wet conditions.

Fate of herbicides in cropped lysimeters: 1. Influence of different processes and model structure on vadose zone flow

AbstractUnderstanding transport and fate processes in the subsurface is of fundamental importance to identify the leaching potentials of herbicides or other compounds to groundwater resources. HYDRUS‐1D was used to simulate water flow and solute transport in arable land lysimeters. Simulations were compared to observed drainage rates and stable water isotopes (δ18O) in the drainage. Four different model setups were investigated and statistically evaluated for their model performance to identify dominant processes for water flow characterization in the vadose zone under similar cultivation management and climatic conditions. The studied lysimeters contain soil cores dominated by sandy gravel (Ly1) and clayey sandy silt (Ly2), both cropped with maize located in Wielenbach, Germany. First, a single‐porosity setup was chosen. For Ly1, modeling results were satisfactory, but for Ly2, the damping observed in the isotope signature of the drainage could not be fully covered. By considering immobile water with a dual‐porosity setup for Ly2, model performance improved. This could be due to a higher fraction of fine pores in Ly2 available for water storage, leading to mixing processes of isotopically enriched summer precipitation and lighter winter water. Accounting for isotopic evaporation fractionation processes in both model setups did not lead to improved model performance. Consequentially, the difference in soil hydraulic properties between the two lysimeters seems to impact water flow processes. Knowledge of such differences is crucial to prevent contamination and mitigate potential risks to soil and groundwater.

Spatial-temporal characteristics of inorganic anions in the Middle Route of South-North Water Diversion project in Henan province (China)

Atmospheric deposition is a vital source of nutrient input into lakes and reservoirs. Therefore, it is of great significance to study the spatial-temporal variation of inorganic anions during the dry and wet atmospheric deposition to ensure the water ecological security of the South-North Water Diversion Middle Route Project (MRP). This study investigated the spatial-temporal variation of inorganic anions (F−, Cl−, NO3−, and SO42−) concentration and its sedimentation fluxes in dry and wet deposition, and their influence on water quality through 10 automatic dust rainfall collection devices installed in the Henan section of the MRP from October 2018 to October 2020. Results indicated that the anion concentration and deposition flux in dry and wet deposition varied in space and time, and SO42− was the highest anion in dry deposition (178.88 ± 175.60 mg/L) and NO3− was the highest anion in wet deposition (52.02 ± 24.63 mg/L). Furthermore, correlation analysis showed that there was a correlation between the wet deposition of anions (F−, Cl−, NO3−, and SO42−) and water quality in winter in the Henan section of the MRP (p < 0.05), and anions dry deposition fluxes have an effect on spring and winter water quality, while the wet deposition fluxes only have an impact on summer and autumn water quality due to the abundant precipitation in summer and autumn. This study could provide new data support for management measures such as strengthening the ecological environment and water quality protection in the MRP.

Simulation and optimisation of a medium scale reverse osmosis brackish water desalination system under variable feed quality: Energy saving and maintenance opportunity

In this work, we considered model-based simulation and optimisation of a medium scale brackish water desalination process. The mathematical model is validated using actual multistage RO plant data of Al- Hashemite University (Jordan). Using the validated model, the sensitivity of different operating parameters such as pump pressure, brackish water flow rate and seasonal water temperature (covering the whole year) on the performance indicators such as productivity, product salinity and specific energy consumption of the process is conducted. For a given feed flow rate and pump pressure, winter season produces less freshwater that in summer in line with the assumption that winter water demand is less than that in summer.With the soaring energy prices globally, any opportunity for the reduction of energy is not only desirable from the economic point of view but is an absolute necessity to meet the net zero carbon emission pledge by many nations, as globally most desalination plants use fossil fuel as the main source of energy. Therefore, the second part of this paper attempts to minimise the specific energy consumption of the RO system using model-based optimisation technique. The study resulted not only 19 % reduction in specific energy but also 4.46 % increase in productivity in a particular season of the year. For fixed product demand, this opens the opportunity for scheduling cleaning and maintenance of the RO process without having to consider full system shutdown.

Machine Learning Predicts the Methane Clumped Isotopologue (12CH2D2) Distributions Constrain Biogeochemical Processes and Estimates the Potential Budget.

Methane (CH4) is a matter of environmental concern; however, global methane isotopologue data remain inadequate. This is due to the challenges posed by high-resolution testing technology and the need for larger sample volumes. Here, worldwide methane clumped isotope databases (n = 465) were compiled. We compared machine-learning (ML) models and used random forest (RF) to predict new Δ12CH2D2 distributions, which cover valuable and hard-to-replicate methane clumped isotope experimental data. Our RF model yields a reliable and continuous database including ruminants, acetoclastic methane, multiple pyrolysis, and controlled experiments. We showed the effectiveness of utilizing a new data set to quantify isotopologue fractionations in biogeochemical methane processes, as well as predicting the steady-state atmospheric methane clumped isotope composition (Δ13CH3D of +2.26 ± 0.71‰ and Δ12CH2D2 of +62.06 ± 4.42‰) with notable biological contributions. Our measured summer and winter water emitted gases (n = 6) demonstrated temperature-driven seasonal microbial community evolution determined by atmospheric clumped isotope temporal variations (Δ 13CH3D ∼ -0.91 ± 0.25 ‰ and Δ12CH2D2 ∼ +3.86 ± 0.84 ‰), which in turn is relevant for future models quantifying the contribution of methane sources and sinks. Predicting clumped isotopologues translates our methane geochemical understanding into quantifiable variables for modeling that can continue to improve predictions and potentially inform global greenhouse gas emissions and mitigation policy.

Seasonality of zooplankton communities in the Hudson Bay system

The strong seasonality of sub-Arctic seas needs to be considered to understand their ecosystems. The Hudson Bay system undergoes strong seasonal changes in 1) sea ice conditions, alternating between complete ice cover in winter and open water in summer; 2) river discharge, which peaks in the spring and influences the stratification of the bay; and 3) surface circulation that consists of a weak double gyre system in spring and summer and a cyclonic system in the autumn. Recent studies that included data collected during spring have shown that the annual primary productivity in the Hudson Bay system is higher than previously reported. Similarly, the regional zooplankton assemblages have been studied mostly in late summer, possibly leading to an underestimation of the annual secondary production. Here, we use data collected during five one to six week-long expeditions of the CCGS Amundsen in the Hudson Bay system between 2005 and 2018 to describe the seasonality in mesozooplankton assemblages and investigate how it depends on environmental variables. In general, small pan-Arctic and boreal copepods such as Microcalanus spp., Oithona similis and Pseudocalanus spp. dominated the assemblages. From spring to summer, the relative abundance of the Arctic-adapted Calanus hyperboreus and Calanus glacialis decreased, while the proportion of the boreal Pseudocalanus spp. and Acartia spp. increased. The day of the year and the ice break-up date explained most of the variation in mesozooplankton assemblages. Physical processes explained most of the species distribution in spring, while the lack of lipid-rich zooplankton species in late summer and autumn, especially in coastal regions, suggests some top-down control. This lack of lipid-rich zooplankton late in the season contrasts with other seasonally ice-covered seas. More data are needed to fully understand the implications of these dynamics under climate change, but this study establishes a baseline against which future changes can be compared.

Ecological state of the small Plyushchikha river within the boundaries of the city of Novosibirsk

The Plushykha River is one of the nine small urban rivers of Novosibirsk feeding the Ob. In its coastal zone there are garden societies, highways, railways, which have a significant impact on its condition. The purpose of this work was to assess the state of the coastal zone and some hydrochemical and physical indicators of the water of the Plyushchikha River within the city of Novosibirsk. According to the results of the observations, erosion of coastal slopes by thawed and stormwater was noted, siltation of the Ivy riverbed is observed in the summer. When studying the physical parameters of water, an increase in the intensity of odor in the spring, summer and winter period was noted to 3.0; 4.8 and 2.8 points, respectively. The color index in winter and spring is 44°, which is 2 times higher than the MPC, in summer — 54°, which is 2.7 times higher than the MPC. There was also an excess of the permissible turbidity value in the spring period by 2.6 times, and in the summer and winter periods by 3.6 times. The pH of the water in summer and winter is slightly alkaline, and in spring it is alkaline (9.0 units), the hardness of the water of the Plushykha River varies depending on the season. In spring, this indicator was 4.62°F, in summer — 5.32°F, and in winter — 10.56°F, which is slightly higher than the MPC (10.0°F). The total alkalinity of the water was 9.5 mg*eq/l in spring, 7.5 mg*eq/l in summer, and 12.54 mg*eq/l in winter, with a norm of up to 7.9 mg*eq/l. The concentration of nitrates in the spring and summer periods exceeded the maximum permissible value for natural reservoirs (0.2–1 mg/l) and amounted to 10.0 and 12.3 mg/l, respectively. The level of nitrite ions in river water in spring and summer was 0.7; 0.4 mg/l at MPC — 0.2 mg/l.

Nutrient Flux under the Influence of Melt Water Runoff from Volcanic Territories and Ecosystem Response of Vilyuchinskaya and Avachinskaya Bays in Southeastern Kamchatka

Nutrient fluxes with river runoff can largely determine the state of coastal water ecosystems. The Vilyuchinskaya and Avachinskaya Bays of Kamchatka Peninsula were surveyed on 4–5 July 2022, just after the peak of the spring–summer flood of the Vilyucha and Avacha Rivers associated with the snow melting in volcanic areas. Additionally, water sampling was performed in river water in December 2022, in the period of winter low water. A general undersaturation of CO2 of surface waters was observed in the Vilyuchinskaya and Avachinskaya Bays. Strong supersaturation of CO2 of the near-bottom waters was observed, due to microbial destruction of organic matter, especially in Avachinskaya Bay. This organic matter was formed as a result of photosynthesis in the water column, which subsequently gravitated to the bottom and concentrated in specific bottom depressions in the studied bays. In these depressions, black sediments were found, in which sulfate reduction occurred. The porewater of sediments had a very high concentration of organic carbon, dissolved and organic nitrogen, and phosphates, as well as CO2 partial pressure. The source of nutrients for the studied bays is tephra (volcanic suspended particles), which covers all the watersheds, including the soil and snow, as a result of volcanic activity in the study region. Based on the calculated nutrient fluxes in river runoff for the summer and winter seasons and the DIN/DIP ratios in river, sea, and pore waters, the causes of phytoplankton blooms, including the occurrence of red tides, are discussed. The maximum flux of nutrients and, accordingly, phytoplankton blooms should be expected in the years with the highest volcanic activity and high summer air temperatures, since the melting of nutrient-rich snow and ice will be maximum. This will determine the flux of nutrients in the river runoff of the Kamchatka Peninsula and contribute to phytoplankton blooms.

Популяционные характеристики двустворчатого моллюска Macoma calcarea (Gmelin, 1791) во фьордах Шпицбергена с разным гидрологическим режимом

The features of the distribution and biology of the bivalve mollusk Macoma calcarea in the fjords of Western Svalbard with different hydrological regimes in 2019 have been established. Two groups of settlements are distinguished, differing in terms of abundance, size and age structure, and growth rate. The most favorable conditions for the formation of colonies with high abundance, diverse size and age structure, and high lifespan of M. calcarea were noted in the Atlantic and transformed Atlantic water masses with a temperature of more than 2 oC in Grenfjord Inlet and Koles Bay, due to the influence of the warm Atlantic currents. The least favorable conditions are typical for fjords with negative water temperatures and high salinity in the layer of winter water masses (Sturfjord), where an unstable settlement with low abundance, high growth rate and shorter life expectancy has formed.

Unsupervised classification identifies coherent thermohaline structures in the Weddell Gyre region

Abstract. The Weddell Gyre is a major feature of the Southern Ocean and an important component of the planetary climate system; it regulates air–sea exchanges, controls the formation of deep and bottom waters, and hosts upwelling of relatively warm subsurface waters. It is characterised by low sea surface temperatures, ubiquitous sea ice formation, and widespread salt stratification that stabilises the water column. Observing the Weddell Gyre is challenging, as it is extremely remote and largely covered with sea ice. At present, it is one of the most poorly sampled regions of the global ocean, highlighting the need to extract as much value as possible from existing observations. Here, we apply a profile classification model (PCM), which is an unsupervised classification technique, to a Weddell Gyre profile dataset to identify coherent regimes in temperature and salinity. We find that, despite not being given any positional information, the PCM identifies four spatially coherent thermohaline domains that can be described as follows: (1) a circumpolar class, (2) a transition region between the circumpolar waters and the Weddell Gyre, (3) a gyre edge class with northern and southern branches, and (4) a gyre core class. PCM highlights, in an objective and interpretable way, both expected and underappreciated structures in the Weddell Gyre dataset. For instance, PCM identifies the inflow of Circumpolar Deep Water (CDW) across the eastern boundary, the presence of the Weddell–Scotia Confluence waters, and structured spatial variability in mixing between Winter Water and CDW. PCM offers a useful complement to existing expertise-driven approaches for characterising the physical configuration and variability of oceanographic regions, helping to identify coherent thermohaline structures and the boundaries between them.

Subglacial hydrology modeling predicts high winter water pressure and spatially variable transmissivity at Helheim Glacier, Greenland

AbstractWater pressure beneath glaciers influences ice velocity. Subglacial hydrology models are helpful for gaining insight into basal conditions, but models depend on unconstrained parameters, and a current challenge is reproducing elevated water pressures in winter. We eliminate terms related to englacial storage, opening by sliding, and melt due to changes in the pressure-melting-point temperature, to create a minimalist version of the Subglacial Hydrology And Kinetic, Transient Interactions (SHAKTI) model, and apply this model to Helheim Glacier in east Greenland to explore the winter base state of the subglacial drainage system. Our results suggest that meltwater produced at the bed alone supports active winter drainage with large areas of elevated water pressure and preferential drainage pathways, using a continuum approach that allows for transitions between flow regimes. Transmissivity varies spatially over several orders of magnitude from 10−4to 103m2s−1, with regions of weak transmissivity representing poorly connected regions of the system. Bed topography controls the location of primary drainage pathways, and high basal melt rates occur along the steep valley walls. Frictional heat from sliding is a dominant source of basal melt; different approaches for calculating basal shear stress produce significantly different basal melt rates and subglacial discharge.