Lake Ice Research Articles

Pivotal role of snow depth, local atmospheric conditions, and large-scale climate signals on ice thinning in Finnish lakes.

Lake ice thickness is a critical indicator of climate change, with profound implications for aquatic ecosystems. Despite its importance, our understanding of changes in lake ice thickness is relatively limited. Additionally, the influence of snow depth on ice thickness at a regional scale is not well understood, primarily due to the lack of long-term, high-resolution in-situ data. In this study, we leveraged in-situ data from 35 stations across 32 deep Finnish lakes, collected from 1995 to 2023, to investigate and simulate changes in maximum ice thickness using traditional statistical tools and artificial intelligent models. Our results indicate a decrease in maximum ice thickness at nearly all (34 out of 35) studied sites, with an average annual decrease of ∼3.4mm/yr. The rate of decline was slower in lakes situated at higher latitude and at higher elevation. In the southern lakes of Finland, local atmospheric conditions were more effective in explaining the variance in ice thickness. However, at higher latitudes, the influence of these local factors decreased. Winter air temperature and snow depth were identified as the main drivers of maximum ice thickness. Snow depth was positively correlated with ice thickness (R=0.63), largely due to its insulating effect, which supports faster ice growth in deeper lakes. Among the large-scale climate signals tested, the North Atlantic Oscillation and Scandinavia Pattern, as well as global CO2 concentrations, were key drivers of the developed ice thickness models. Our findings suggest that readily accessible large-scale climate signals can be used to inform modelling efforts of lake ice thickness.

Fish mass mortality events in northern temperate lakes are happening later in the year than in the past

AbstractGlobally, mass mortality events are becoming more common across ecosystems and taxa. For fishes in northern temperate lakes, climate change is predicted to increase the frequency of summerkills and decrease the frequency of winterkills. We compiled reports of fish kills in Michigan inland lakes from 1936 to 2022 derived from historical records, management reports, and an online app for the public. Using this dataset of 525 reported fish kills in eight decades, we tested for changes in timing of fish kills. We found that fish kills in the early 20th century were most likely to be reported in early spring months, as lake ice thawed, while in the later 20th and early 21st centuries, more fish kills were reported through summer. Across our dataset, the median day of year fish kills were reported shifted later by more than 50 days. Shifts in the timing of these perturbations can alter population demography, and community resilience, and may have lasting and unprecedented impacts on lake ecosystems.

Comparative study on lake ice phenology changes and driving factors in large lakes of mid-latitude Xinjiang, China.

The changes in lake ice phenology (LIP) can intuitively reflect the climate evolution in the regions where lakes are located, serving as an important indicator of climate change. The Tianshan Mountains, situated at the southern edge of freezing lakes in the Northern Hemisphere, are a crucial water resource base in Xinjiang and support significant ecosystems closely related to human activities. In the context of intensified climate change, this study focuses on the geographical location, altitude, and water quality differences among large lake groups in the mid-latitude region of Xinjiang, aiming to explore the characteristics of LIP changes in these lakes and their responses to driving factors, thereby providing a basis for effective environmental management and protection. This research conducts a comparative analysis of the LIP changes and driving factors of three large lakes-Sayram Lake (SL), Bosten Lake (BL), and Ebnur Lake (EL)-using multi-source remote sensing data to reveal the response and adaptation mechanisms of lakes under global warming. It effectively captures the time series variations of ice formation and melting, as well as the common responses to environmental and climatic factors. The results indicate that SL has experienced significant climate change effects, with earlier freezing times and accelerated melting speeds; In contrast, EL and BL have shown relatively minor changes, suggesting that geographical and hydrological factors may buffer the impacts of climate. The study finds that all three lakes are jointly influenced by environmental factors such as temperature, wind speed, and precipitation; however, due to differences in altitude, lake surface area, and water transparency, their responses to these climatic factors vary significantly. For instance, SL's high altitude gives water transparency a dominant role in LIP, while BL's larger surface area enhances the impact of precipitation and thermal capacity on the melting process. This indicates that, despite facing similar climate pressures, local environmental conditions can lead to different trends in ice phenology changes. This study offers a novel and efficient monitoring method for LIP, providing valuable insights for future LIP research and water resource management.

An Investigation of the Thickness of Huhenuoer Lake Ice and Its Potential as a Temporary Ice Runway

The study of ice runways has significant practical importance. Regarding inland lake ice, while little of the practicality of ice runways during the ice formation period was explored in the published articles, the analysis of the time period and suitable locations may be used. This study focused on Huhenuoer Lake, located in Chen Barag Banner in northeastern China. The time-dependent law of ice growth in this lake has been investigated over a study period from 2023 to 2024. Utilizing the drilling approach, the ice thickness, recorded at each site on 29 February 2024, has surpassed 100 cm. On 14 March 2024, the recorded ice thickness at site #2 reached a record high of 139 cm. Second, to assess the project’s ease of use and safety, we used the Stefan equation to model the lake’s ice growth processes, resulting in a fitted Stefan coefficient of 2.202. For safety considerations, the Stefan coefficient used for the construction of the ice runway was set at 1.870. We investigated the distribution of lake ice and concluded that the lake ice runway should be established in the north. We established the relationship between ice thickness, cumulative snowfall, and negative accumulated temperature by integrating the fitting technique with the Stefan model. Utilizing the P-III method, the minimum value of the maximum negative accumulated temperature for the 50-year return period is 2092.46 °C·d, while the maximum cumulative snowfall for the 50-year period is 58.4 mm. We can apply these values to the aforementioned relationship to derive the ice thickness patterns across varying return periods. Finally, the study provides recommendations for the construction of the ice runway at Huhenuoer Lake. This study introduces ice field research and an ice growth model into the analysis of lake ice runway operations to provide technical assistance for ice runways.

Contrasting Changes in Lake Ice Thickness and Quality Due to Global Warming in the Arctic, Temperate, and Arid Zones and Highlands of Eurasia

Lake ice has a major impact on the functioning of lake ecosystems, the thermal and gas regimes of lakes, habitat conditions, socio-economic aspects of human life, local climate, etc. The multifaceted influence of lake ice makes it important to study its changes associated with global warming, including lake ice phenology, ice thickness, and the snow–ice fraction. This article presents a study of lake ice changes in different regions of Eurasia: the Arctic (Lake Imandra in the Murmansk region and Lake Kilpisjärvi in Finland), the temperate zone (six small and medium lakes in Karelia, Mozhaysk Reservoir in the Moscow region, and Lake Pääjärvi in Finland), the arid zone (Lake Ulansuhai in China), and the highlands (lakes Arpi and Sevan in Armenia). In the study regions, a statistically significant increase in winter air temperature has been recorded over the past few decades. The number of days with thaw (air temperature above 0 °C) has increased, while the number of days with severe frost (air temperature below −10 °C and −20 °C) has decreased. The share of liquid or mixed precipitation in winter increases most rapidly in the temperate zone. For two Finnish lakes, lakes Vendyurskoe and Vedlozero in Karelia, and Mozhaysk Reservoir, a decrease in the duration of the ice period was revealed, with later ice-on and earlier ice-off. The most dramatic change occurred in the large high-mountain Lake Sevan, where the water area has no longer been completely covered with ice every winter. In contrast, the small high-mountain Lake Arpi showed no significant changes in ice phenology over a 50-year period. Changes in the ice composition with an increase in the proportion of white ice and a decrease in the proportion of black ice have occurred in some lakes. In the temperate lakes Pääjärvi and Vendyurskoe, inverse dependences of the thickness of black ice on the number of days with thaw and frost in December–March for the first lake and on the amount of precipitation in the first month of ice for the second were observed. In the arid study region of China, due to the very little winter precipitation (usually less than 10 mm) only black ice occurs, and significant interannual variability in its thickness has been identified.

Air–Ice–Water Temperature and Radiation Transfer Via Different Surface Coverings in Ice-Covered Qinghai Lake of the Tibetan Plateau

There are numerous lakes in the Tibetan Plateau (TP) that significantly impact regional climate and aquatic ecosystems, which often freeze seasonally owing to the high altitude. However, the special warming mechanisms of lake water under ice during the frozen period are poorly understood, particularly in terms of solar radiation penetration through lake ice. The limited understanding of these processes has posed challenges to advancing lake models and improving the understanding of air–lake energy exchange during the ice-covered period. To address this, a field experiment was conducted at Qinghai Lake, the largest lake in China, in February 2022 to systematically examine thermal conditions and radiation transfer across air–ice–water interfaces. High-resolution remote sensing technologies (ultrasonic instrument and acoustic Doppler devices) were used to observe the lake surface changes, and MODIS imagery was also used to validate differences in lake surface conditions. Results showed that the water temperature under the ice warmed steadily before the ice melted. The observation period was divided into three stages based on surface condition: snow stage, sand stage, and bare ice stage. In the snow and sand stages, the lake water temperature was lower due to reduced solar radiation penetration caused by high surface reflectance (61% for 2 cm of snow) and strong absorption by 8 cm of sand (absorption-to-transmission ratio of 0.96). In contrast, during the bare ice stage, a low reflectance rate (17%) and medium absorption-to-transmission ratio (0.86) allowed 11% of solar radiation to penetrate the ice, reaching 11.70 W·m−2, which increased the water temperature across the under-ice layer, with an extinction coefficient for lake water of 0.39 (±0.03) m−1. Surface coverings also significantly influenced ice temperature. During the bare ice stage, the ice exhibited the lowest average temperature and the greatest diurnal variations. This was attributed to the highest daytime radiation absorption, as indicated by a light extinction coefficient of 5.36 (±0.17) m−1, combined with the absence of insulation properties at night. This study enhances understanding of the characteristics of water/ice temperature and air–ice–water solar radiation transfer through effects of different ice coverings (snow, sand, and ice) in Qinghai Lake and provides key optical radiation parameters and in situ observations for the refinement of TP lake models, especially in the ice-covered period.

Seasonal lake ice cover drives the restructuring of bacteria-archaea and bacteria-fungi interdomain ecological networks across diverse habitats.

The coexistence of different microbial communities is fundamental to the sustainability of many ecosystems, yet our understanding of the relationships among microbial communities in plateau cold-region lakes affected by seasonal ice cover remains limited. This research involved investigating three lakes in the Inner Mongolia segment of the Yellow River basin during frozen and unfrozen periods in two habitats: water bodies and sediments. The research examined the composition and function of bacteria, archaea, and fungi across different times and habitats within the basin, their response to environmental variables in water and sediment, and inter-domain interactions between bacteria-archaea and bacteria-fungi were compared using interdomain ecological network (IDEN). The findings indicate significant variations in the structures of bacterial, archaeal, and fungal communities across different periods and habitats, with the pH of the water body being a crucial environmental variable affecting microbial community composition. In the frozen period, the functionality of microbial communities, especially in terms of energy metabolism, was significantly impacted, with water bodies experiencing more pronounced effects than sediments. Archaea and fungi significantly contribute to the stability of bacterial communities across various habitats, especially in ice-covered conditions, where stronger associations between bacterial communities, archaea, and fungi promote the microbial communities' adaptability to cold stress. Furthermore, our results indicate that the primary environmental variable influencing the structure of IDENs is the nutrient salt content in both water bodies and sediments. This study broadens our understanding of the responses and feedback mechanisms of inter-domain microbial interactions in lakes influenced by seasonal ice cover.

The formation conditions of subglacial Lake Vostok’s accreted ice based on its stable water isotope composition

In this paper, we present a new dataset on the stable water isotopic composition (δD and δ18O) in a sequence of subglacial Lake Vostok’s accreted ice (3538–3769 m) measured along three parallel ice cores. The high precision of the new data has allowed us to characterize the formation conditions of different sections of the ice. The whole lake ice interval may be divided into 3 zones: 1) “zone 0”, 3538.8–3549.8 m, is under the strong influence of the local water formed from melted meteoric ice likely entering from under the glacier on the lake’s west coast; 2) “zone 1” (accreted ice 1), 3549.8–3607.4 m, is experiencing significant variability due to the slightly different effective fractionation coefficient in the course of “water inclusions” in the ice matrix during the freezing process; 3) “zone 2” (accreted ice 2), 3607.4–3768.8 m, is under the influence of glacial melt water from the northern part of the lake and the hydrothermal flux from the lake’s bottom. We defined the exact boundary between the accreted ice 1 and ice 2, which corresponds to a sharp isotopic excursion at a depth of 3607.4 m. In this work, we present for the first time data on the “17O-excess” parameter in the lake ice and water, which allowed us to make a direct calculation of the equilibrium fractionation coefficient for oxygen 17 during water freezing.

Widespread loss of safe lake ice access in response to a warming climate.

Millions of people rely on lake ice for safe winter recreation. Warming air temperatures impact the phenology (timing of formation and breakup) and quality (ratio of black to white ice) of lake ice cover, both critical components of ice safety. Later formation and earlier breakup of lake ice lead to overall shorter periods of use. However, greater proportions of white ice may further inhibit safe ice use owing to its lower weight-bearing capacity. As ice cover duration decreases and ice quality changes in a warming world, the period of safe ice use will similarly diminish. We use a large ensemble modeling approach to predict ice safety throughout the winter period in the Northern Hemisphere. We used the Community Earth System Model Version 2 Large Ensemble (CESM2-LE) to calculate the period when ice first appears until it is of sufficient thickness for safe use, which depends on the ratio of black to white ice. We conducted this analysis for 2,379 to 2,829 ~1° by 1° grid cells throughout the Northern Hemisphere. We focus on the period between ice formation (≥ 2 cm) to a safe thickness for general human use (i.e., ≥10, ≥15, or ≥20 cm, depending on the ratio of black to white ice). We find that the transition period from unsafe to safe ice cover is growing longer, while the total duration of safe ice cover is getting shorter. The transition period of unsafe ice increases by 5.0 ± 3.7 days in a 4°C warmer world, assuming 100% black ice. Diminished ice quality further limits safe ice conditions. The unsafe transition period increases by an average of 19.8 ± 8.9 days and 8.8 ± 6.6 days for the ice formation and breakup periods, respectively in a 4°C warmer world assuming 100% white ice conditions. We show that although many lakes are forecasted to freeze, they will be unsafe to use for an average of 5 to 29 fewer days in a 4°C warmer world for 100% black and 100% white ice ratios, respectively. This wide range indicates that ice quality has a strong influence on ice safety. This work highlights the need to understand both lake ice phenology and quality to better assess safe lake ice use during the formation and melt periods.

Simulation and Prediction of Thermokarst Lake Surface Temperature Changes on the Qinghai–Tibet Plateau

Thermokarst lakes are shallow bodies of freshwater that develop in permafrost regions, and they are an essential focus of international permafrost research. However, research regarding the mechanisms driving temperature fluctuations in thermokarst lakes and the factors that influence these changes is limited. We aimed to analyze seasonal variations in the surface water temperature, clarify historical trends in the phenological characteristics of lake ice, and predict future temperature changes in surface water of the thermokarst lakes using the air2water model. The results indicated that in comparison with air temperature, the thermokarst lake’s surface water temperature showed a certain lag and significantly higher values in the warm season. The warming rate of the thermokarst lake’s average surface water temperature based on historical data from 1957 to 2022 was 0.21 °C per decade, with a notably higher rate in August (0.42 °C per decade) than in other months. Furthermore, the ice-covered period steadily decreased by 2.12 d per decade. Based on the Coupled Model Intercomparison Project 6 projections, by 2100, the surface water temperatures of thermokarst lakes during the warm season are projected to increase by 0.38, 0.46, and 2.82 °C (under scenarios SSP126, SSP245, and SSP585), respectively. Compared with typical tectonic lakes on the Qinghai–Tibet Plateau, thermokarst lakes have higher average surface water temperatures during ice-free periods, and they exhibit a higher warming rate (0.21 °C per decade). These results elucidate the response mechanisms of thermokarst lakes’ surface water temperature and the phenological characteristics of lake ice in response to climate change.

Cyanobacteria in winter: seasonal dynamics of harmful algal blooms and their driving factors in boreal lakes

Lake cyanobacteria can overgrow and form blooms, often releasing life-threatening toxins. Harmful algal blooms (HABs) are typically caused by excess nutrients and high temperatures, but recent observations of cyanobacteria beneath the ice in boreal lakes suggest that the dynamics are more complex. This study investigates the seasonal dynamics of HABs in boreal lakes and identifies their driving factors. We study cyanobacteria assemblages in two boreal lakes in Abitibi-Témiscamingue (Quebec, Canada): Lake Fortune, noted for its under-ice cyanobacteria, and Lake Beauchamp, which has experienced recurrent summer-only cyanobacterial blooms. From June 2021 to July 2022, we identified monthly cyanobacterial communities and estimated water nutrients, organic carbon, temperature, oxygen, and pH. Cyanobacterial communities were dominated by the genus Planktothrix in Lake Fortune, and this genus was in a bloom state for each month of the year. Cyanobacterial abundance was highest (210000cells/mL) in November and lowest (28000cells/mL) in March. The abundance of Planktothrix correlated with total nitrogen and phosphorus and dissolved organic carbon concentrations. Planktothrix dominated even under ice cover, because of its ability to thrive in low-light and low phosphorus conditions. In Lake Beauchamp, Aphanothece was found throughout the year, highest (27800cells/mL) in August and lowest (2100cells/mL) in March. In Lake Beauchamp, cyanobacterial blooms correlated with total dissolved phosphorus, nitrogen and organic carbon concentrations during summer and fall. The dominance of Aphanothece was especially pronounced during the summer and fall. Our study provides new knowledge about the seasonal dynamics of cyanobacterial blooms to help guide the future management of HABs in boreal lakes.

Threshold Ranges of Multiphase Components from Natural Ice CT Images Based on Watershed Algorithm

The multiphase components of natural ice contain gas, ice, unfrozen water, sediment and brine. X-ray computed tomography (CT) analysis of ice multiphase components has the advantage of high precision, non-destructiveness and visualization; however, it is limited by the segmentation thresholds. Due to the proximity of the CT value ranges of gas, ice, unfrozen water, sediment and brine within the samples, there is uncertainty in the artificial determination of the CT image segmentation thresholds, as well as unsuitability of the global threshold segmentation methods. In order to improve the accuracy of multi-threshold segmentation in CT images, a CT system was used to scan the Yellow River ice, the Wuliangsuhai lake ice and the Arctic sea ice. The threshold ranges of multiphase components within the ice were determined by watershed algorithm to construct a high-precision three-dimensional ice model. The results indicated that CT combined with watershed algorithm was an efficient and non-destructive method for obtaining microscopic information within ice, which accurately segmented the ice into multiphase components such as gas, ice, unfrozen water, sediment, and brine. The gas CT values of the Yellow River ice, the Wuliangsuhai lake ice and the Arctic sea ice ranged from −1024 Hu~−107 Hu, −1024 Hu~−103 Hu, and −1024 Hu~−160 Hu, respectively. The ice CT values of the Yellow River ice, the Wuliangsuhai lake ice and the Arctic sea ice ranged from −103 Hu~−50 Hu, −100 Hu~−38 Hu, −153 Hu~−51 Hu. The unfrozen water CT values of the Yellow River ice and the Wuliangsuhai lake ice ranged from −8 Hu~18 Hu, −8 Hu~13 Hu. The sediment CT values of the Yellow River ice and the Wuliangsuhai lake ice ranged from 20 Hu~3071 Hu, 20 Hu~3071 Hu, and the brine CT values of the Arctic sea ice ranged from −6 Hu~3071 Hu. The errors between the three-dimensional ice model divided by threshold ranges and measured sediment content were less than 0.003 g/cm3, which verified the high accuracy of the established microscopic model. It provided a scientific basis for ice engineering, ice remote sensing, and ice disaster prevention.

Variations of Lake Ice Phenology Derived from MODIS LST Products and the Influencing Factors in Northeast China

Lake ice phenology serves as a sensitive indicator of climate change in the lake-rich Northeast China. In this study, the freeze-up date (FUD), break-up date (BUD), and ice cover duration (ICD) of 31 lakes were extracted from a time series of the land water surface temperature (LWST) derived from the combined MOD11A1 and MYD11A1 products for the hydrological years 2001 to 2021. Our analysis showed a high correlation between the ice phenology measures derived by our study and those provided by hydrological records (R2 of 0.89) and public datasets (R2 > 0.7). There was a notable coherence in lake ice phenology in Northeast China, with a trend in later freeze-up (0.21 days/year) and earlier break-up (0.19 days/year) dates, resulting in shorter ice cover duration (0.50 days/year). The lake ice phenology of freshwater lakes exhibited a faster rate of change compared to saltwater lakes during the period from HY2001 to HY2020. We used redundancy analysis and correlation analysis to study the relationships between the LWST and lake ice phenology with various influencing factors, including lake properties, local climate factors, and atmospheric circulation. Solar radiation, latitude, and air temperature were found to be the primary factors. The FUD was more closely related to lake characteristics, while the BUD was linked to local climate factors. The large-scale oscillations were found to influence the changes in lake ice phenology via the coupled influence of air temperature and precipitation. The Antarctic Oscillation and North Atlantic Oscillation correlate more with LWST in winter, and the Arctic Oscillation correlates more with the ICD.

Characteristics and Correlation Study of Mountainous Lake Ice Phenology Changes in Xinjiang, China Based on Passive Microwave Remote Sensing Data

Lake ice phenology directly reflects local climate changes, serving as a key indicator of climate change. In today’s rapidly evolving climate, utilizing advanced remote sensing techniques to quickly extract long-term lake ice phenology features and studying their correlation with other climate factors is crucial. This study focuses on lakes in Xinjiang, China, with a mountainous area greater than 100 km2, including Sayram Lake, Ayahkum Lake, Achihkul Lake, Jingyu Lake, and Ahsaykan Lake. The Bayesian ensemble change detection algorithm was employed to extract lake ice phenology information, and the Mann–Kendall (MK) non-parametric test was used to analyze trends. The visual interpretation method was used to interpret the spatial evolution characteristics of lake ice, and the Pearson correlation coefficient was used to explore the driving factors of lake ice phenology. Results indicate the following: (1) Jingyu Lake exhibited the most significant delay in both freezing and complete freezing days, while Ayahkum Lake showed the most stable pattern. Ahsaykan Lake demonstrated the least delay in both starting and complete melting days. (2) Sayram Lake’s ice evolution was unstable, with wind causing variability in the locations where freezing begins and melting spreading from the west shore. Ayahkum Lake, Ahsaykan Lake, and Jingyu Lake exhibited similar seasonal variations, while Achihkul Lake’s ice spatial changes spread from the east to the center during freezing and from the center to the shore during melting. (3) The study found that the freeze–thaw process is influenced by a combination of factors including lake area, precipitation, wind speed, and temperature.

Distribution of mercury and methylmercury in ice-water-sediments in lakes during the freezing period under the influence of ice cover

The presence of lake ice cover alters the subglacial water environment, thereby influencing the migration and transformation of mercury (Hg) and methylmercury (MeHg) within the ice-water-sediment media of lakes. This study investigated the occurrence characteristics of mercury and methylmercury in various environmental compartments within lakes located at high latitudes in cold regions during the freezing period. To this end, Wuliangsuhai Lake, the largest freshwater lake situated at 40°N in China, was selected as the study site. The contents of mercury and methylmercury in lake ice were determined for the first time. The percentage of methylmercury (MeHg%) and ice-water partition coefficient were analyzed. The pollution situation and health risk were evaluated by single factor pollution index. The results show that the ice body and water body of Wuliangsuhai are not polluted by mercury and methylmercury, but some sampling points in the sediment are slightly polluted. The mercury content in sediment is negatively correlated with the ice thickness, and the methylmercury content in water is positively correlated with the methylmercury content in sediment, but negatively correlated with the ice thickness. The migration ability of methylmercury in ice-water system is stronger than that of mercury. The MeHg% of water in ice period is higher than that in non-freezing period, which is different from other lakes without ice sheet. The results show that in the dynamic equilibrium of methylation and demethylation in the high-latitude lake water, the methylation is higher in the ice period than in the non-freezing period due to the influence of light intensity, while the mercury in the non-freezing period is more susceptible to the demethylation.

Study of the patterns of ice lake variation and the factors influencing these changes in the western Nyingchi area

Abstract The current ice lake dataset in the western region of Nyingchi requires further improvement. Due to the intricate distribution of ice lakes and imprecise boundary delineation, research tends to overlook small-scale ice lakes in this area. Moreover, most related studies have focused solely on variations in ice lake areas within key regions, such as the Himalayas, with little attention given to changes occurring in southeastern Tibet. The frequency of ice and snow disasters in the study area has been steadily increasing over the years. Therefore, this study utilizes Landsat satellite images and employs visual interpretation methods to generate more precise and comprehensive maps depicting the distribution of ice lakes in the western region of Nyingchi Province for the years 1994, 2010, 2018, and 2022. Additionally, changes in scale and spatial patterns of different types of ice lakes were investigated. Between 1994 and 2022, the ice lake area in the study area significantly increased by 22.5%, reaching a total of 35.8 ± 3.0 km2. This expansion was primarily driven by glacier-fed lakes, which experienced a remarkable growth rate of 30.8%. In contrast, the non-glacier-fed lakes experienced an increase by only 15.6%. Notably, ice lakes at higher elevations exhibited a peak in expansion, with those above 5143.0 m experiencing the most substantial growth rate of 44.8%. The long-term expansion rate of ice lakes is investigated through the measurement of changes in their boundaries, with the aim to understand the factors contributing to their growth. These findings indicate the rapid expansion of the ice lake near the glacier, with an annual growth rate of 1.3% per annum. Specifically, the glacial-fed section exhibited an expansion rate of 1.1% per annum, while the nonglacial-fed section experienced a growth rate of 0.6% per annum. The seasonal variability in marine glaciers is the primary factor influencing the expansion of ice lakes in this region, with temperature and precipitation serving as the principal driving forces impacting the transformation of these lakes. The data provided by the research results will facilitate a comprehensive understanding of the dynamics and mechanisms governing the ice lake in western Nyingchi, thereby contributing to an enhanced scientific comprehension of potential disaster risks associated with this ice lake.

Simulating lake ice phenology using a coupled atmosphere–lake model at Nam Co, a typical deep alpine lake on the Tibetan Plateau

Abstract. Simulating the ice phenology of deep alpine lakes is important and challenging in coupled atmosphere–lake models. In this study, the Weather Research and Forecasting (WRF) model, coupled with two lake models, the freshwater lake (WRF–FLake) model and the default lake (WRF–CLake) model, was applied to Nam Co, a typical deep alpine lake located in the centre of the Tibetan Plateau, to simulate its lake ice phenology. Due to the large errors in simulating lake ice phenology, related key parameters and parameterizations were improved in the coupled model based on observations and physics-based schemes. By improving the momentum, hydraulic, and thermal roughness length parameterizations, both the WRF–FLake model and the WRF–CLake model reasonably simulated the lake freeze-up date. By improving the key parameters associated with shortwave radiation transfer processes when lake ice exists, both models generally simulated the lake break-up date well. Compared with WRF–CLake without improvements, the coupled model with both revised lake models significantly improved the simulation of lake ice phenology. However, there were still considerable errors in simulating the spatial patterns of freeze-up and break-up dates, implying that significant challenges in simulating the lake ice phenology still exist in representing some important model physics, including lake physics such as grid-scale water circulation and atmospheric processes such as snowfall and surface snow dynamics. Therefore, this work can provide valuable new implications for advancing lake ice phenology simulations in coupled models, and the improved model also has practical application prospects in weather and climate forecasts.

Hypoxia cycle in shallow lakes during winter (ice-covered to melting period): Stable and decay, hypoxia, and recovery phases

This study investigates hypoxic processes beneath lake ice and explores the interactions between water environmental factors and dissolved oxygen (DO) during winter, aiming to systematically assess the influence of winter climate changes on lake ecosystems through environmental variables (physical, chemical, and biological characteristics of water). A complete hypoxic cycle in a high-altitude shallow lake was recorded using high-frequency monitoring technology, and based on a predetermined hypoxic threshold (DO<2mg/L), it was divided into three phases: stable and decay phase, hypoxic phase, and recovery phase. Significant trend changes of environmental variables under different levels of DO were analyzed for each phase using the Mann-Kendall non-parametric test. On the basis of evaluating the overall trend of the time series, a GAM multi-factor optimization model integrating interactive effects was constructed to explore the response mechanism of environmental variables to hypoxic processes. The optimized model showed excellent explanatory performance with R2 values of 0.833 for the stable and decay phase and 0.932 for the recovery phase, with AIC values of 1554.72 and 721.03, respectively. The trend test combined with model analysis indicates that: (1) the decay of DO under the ice is primarily affected by the increase in EC, BGA, and EC*Temp, (2) the phytoplankton biomass in shallow lakes during winter has a definite contribution to the occurrence of oxygen deficiency, and (3) the water body experiences rapid reoxygenation after the ice layer breaks, but the DO level is restricted by the increase in temperature. This study highlights the ecosystem characteristics of shallow ice-covered lakes in cold arid regions, advancing our understanding of the response relationship between hypoxic aquatic environments under ice and environmental factors.

Linking Boundary Organizations to Coproduce Actionable Knowledge: A Case Study of Ice Forecasting for Great Lakes Navigation

Abstract Navigating the Great Lakes during icy conditions poses significant safety challenges for the shipping sector. Available ice information is uncertain and fragmented, and navigators must seek out multiple sources for information at the spatial and temporal scales they require, if the information is available at all. Navigators have expressed that they require more highly localized and easily usable information for current and predicted ice conditions to support decision-making. In this study, we seek to meet this information need by applying a boundary organization chain (BOC) approach to facilitate the coproduction of an actionable short-term Great Lakes ice forecast. We focus on two main aspects of this research: 1) producing an actionable decision-support product that meets the needs of Great Lakes ice navigators and 2) contributing to the knowledge coproduction scholarship on BOCs by providing a detailed account of our methods to create a BOC and coproduce an actionable ice forecast. Our results support incorporating existing communities of practice (COPs) into BOCs to enhance the coproduction of actionable knowledge, specifically through increasing their complementarity and embeddedness. COPs are informal networks of users that meet voluntarily to share knowledge and develop professional skills, which we found naturally builds the coproduction capacities of participants (e.g., embeddedness and complementarity). We also find that COP members are well positioned to disseminate coproduced knowledge across wider user groups. Significance Statement In this study, we identified critical gaps in available ice information to support Great Lakes winter navigation, including predictions of current ice concentration and thickness at localized spatial scales and predicted ice movement. We coproduced an ice forecast with a format that is accessible and usable for navigators, while increasing crew and vessel safety by enabling more informed decisions regarding where and when to travel. We also contributed to theoretical understanding of how boundary organization chains work in context to coproduce actionable knowledge. This is a burgeoning area of research with a small number of empirical studies. By expanding both its thematic breadth (e.g., ice forecasting) and methodological approach (an in-depth account of our engagement efforts), we believe we critically contribute to the existing literature.

Dye tracing of upward brine migration in snow

Abstract Salt is often present in the snow overlying seasonal sea ice, and has profound thermodynamic and electromagnetic effects. However, its provenance and behaviour within the snow remain uncertain. We describe two investigations tracing upward brine movement in snow: one conducted in the laboratory and one in the field. The laboratory experiments involved the addition of dyed brine to the base of terrestrial snow samples, with subsequent wicking being measured. Our field experiment involved dye being added directly (without brine) to bare sea-ice and lake ice surfaces, with snow then accumulating on top over several days. On the sea ice, the dye migrated upwards into the snow by up to 5 cm as the snow's basal layer became more salty, whereas no migration occurred in our control experiment over non-saline lake ice. This occurred in relatively dry snowpacks where brine took up $&lt; 6\%$ of the snow's calculated pore volume, suggesting pore saturation is not required for upward salt transport. Our results highlight the potential role of microstructural parameters beyond those currently retrievable with penetrometry, and the potential value of longitudinal, process-based field studies of young snowpacks.