Winter Air Temperature Research Articles

The effect of anomalous weather on the seasonal clothing market in New York

AbstractThe occurrences of losing the merchandising calendar for seasonal clothes have become more frequent due to anomalous weather changes. In order to develop accurate sales forecasts for clothing retailers, weather changes should be incorporated. The purpose of the study was to find the timing of consumers' seasonal clothing demands and the relationship between the timing of consumers' searches for seasonal clothes and temperature changes. Specifically, drawing upon the United States' seasonal clothing demand from winter jacket Google Trends (GT) and air temperature data from empirical evidence, the study provided a methodology to discover the time lag for seasonal clothing demand timing based on temperature changes. Using the past five years (2014–2019) of GT and temperature data for the US state of New York, abnormal weather due to a significant El Niño year (2015–2016) and a weak La Niña year (2017–2018) was analysed. It suggested that consumers' search activities start when the temperature decreased rapidly continuously for at least six days. Furthermore, a plausible index was employed to determine the timing of peak demand with cumulative sums (CUSUMs). Based on the CUSUMs of air temperature for 18 days, consumers started to search for winter jackets at about 118–128 CUSUMs for a La Niña year, 217–248 CUSUMs for an El Niño year and 281 CUSUMs for a normal year. The results give a guideline to meet consumers' seasonal needs in a timely manner.

Holocene ice wedge formation in the Eureka Sound Lowlands, high Arctic Canada

AbstractIce wedges are ubiquitous periglacial features in permafrost terrain. This study investigates the timing of ice wedge formation in the Fosheim Peninsula (Ellesmere and Axel Heiberg Islands). In this region, ice wedge polygons occupy ~50% of the landscape, the majority occurring below the marine limit in the Eureka Sound Lowlands. Numerical simulations suggest that ice wedges may crack to depths of 2.7–3.6 m following a rapid cooling of the ground over mean winter surface temperatures of −18°C to −38°C, corresponding to the depth of ice wedges in the region. The dissolved organic carbon (DOC)/Cl molar ratios suggest that the DOC in the ice wedges is sourced from snowmelt and not from leaching of the active layer. Based on 3214CDOCmeasurements from 15 ice wedges, the wedges were likely developing between 9000–2500 cal yr BP. This interval also corresponds to the period of peat accumulation in the region, a proxy of increased moisture. Considering that winter air temperatures remained favorable for ice wedge growth throughout the Holocene, the timing of ice wedge formation reflects changes in snowfall. Overall, this study provides the first reconstruction of ice wedge formation from a high Arctic polar desert environment.

Regional-Scale Model Analysis of Climate Changes Impact on the Water Budget of the Critical Zone and Groundwater Recharge in the European Part of Russia

Groundwater recharge by precipitation is the main source of groundwater resources, which are widely used in the European part of Russia (ER). The main goal of the presented studies is to analyze the effect of observed climate changes on the processes of groundwater recharge. For this purpose analysis of long-term meteorological data as well as water budget and groundwater recharge simulation were used. First, meteorological data of 22 weather stations, located from south (Lat 46°) to north (Lat 66°) of ER for historical (1965–1988) and modern (1989–2018) periods were compared to investigate the observed latitudinal changes in annual and seasonal averages of precipitation, wind speed, air temperature, and humidity. Second, water budget in critical zone was simulated, using codes SURFBAL and HYDRUS-1D. SURFBAL generates upper boundary conditions for unsaturated flow modelling with HYDRUS-1D, taking into account snow accumulation and melting as well as topsoil freezing, which are important processes that affect runoff generation and the infiltration of meltwater. Water budget and groundwater recharge simulations based on long-term meteorological data and soil and vegetation parameters, typical for the investigated region. The simulation results for the historical and modern periods were compared to find out the impact of climate change on the average annual and seasonal averages of surface runoff, evapotranspiration, and groundwater recharge, as well as to assess latitudinal differences in water budget changes. The results of the simulation showed, that despite a significant increase in air temperature, groundwater recharge in the southern regions did not change, but even increased up to 50–60 mm/year in the central and northern regions of ER. There are two main reasons for this. First, the observed increase in air temperature is compensated by a decrease in wind speed, so there was no significant increase in evapotranspiration in the modern period. Also, the observed increase in air temperature and precipitation in winter is the main reason for the increase in groundwater recharge, since these climate changes lead to an increase in water infiltration into the soil in the cold period, when there is no evapotranspiration.

Declined trend in herbaceous plant green-up dates on the Qinghai–Tibetan Plateau caused by spring warming slowdown

There has been much debate on the temporal change trend and existence of a turning point in spring green-up date (GUD) of plants on the Qinghai–Tibetan Plateau (QTP). Most previous studies on the QTP used remote sensing data, which have large uncertainties. In this study, using a large amount of long-term ground observation data at 27 phenological stations across the QTP (1694 GUD records), we showed that on the whole, QTP herbaceous plant GUD insignificantly advanced during 1982–2017. Although the direction of the GUD trend did not change from 1982 to 2017, the magnitude of the advancing trend greatly weakened after 1999. According to our estimated results from 28 paired GUD time series, the overall GUD trend shifted from −2.70 days/decade during 1982–1999 to −0.56 days/decade during 2000–2017. This finding contrasts with the conclusions of previous satellite-based studies, which either reported a continuous significant advancement of GUD or a turning point in the mid-to-late 1990s. Through partial correlation analysis and partial least squares regression, we found that winter and spring air temperatures were the primary climatic factors that influenced the temporal change in GUD, and both had negative effects on GUD. The decreased GUD trend was mainly attributable to the warming slowdown in spring. On average, the spring warming rate decreased by 52.43% after 1999, whereas the winter warming rate displayed no obvious change. This study also found that the GUD of forbs showed stronger sensitivity to air temperature change than that of sedges and grasses. This indicates that forbs are more competitive in adaptation to climate warming, which might shift plant community structure and affect ecosystem service function. Moreover, the declined advancement in GUD implies that the spring phenologically driven increase in carbon uptake may have also slowed in the past two decades.

Choosing an arbitrary calibration period for hydrologic models: How much does it influence water balance simulations?

AbstractThe selection of calibration and validation time periods in hydrologic modelling is often done arbitrarily. Nonstationarity can lead to an optimal parameter set for one period which may not accurately simulate another. However, there is still much to be learned about the responses of hydrologic models to nonstationary conditions. We investigated how the selection of calibration and validation periods can influence water balance simulations. We calibrated Soil and Water Assessment Tool hydrologic models with observed streamflow for three United States watersheds (St. Joseph River of Indiana/Michigan, Escambia River of Florida/Alabama, and Cottonwood Creek of California), using time period splits for calibration/validation. We found that the choice of calibration period (with different patterns of observed streamflow, precipitation, and air temperature) influenced the parameter sets, leading to dissimilar simulations of water balance components. In the Cottonwood Creek watershed, simulations of 50‐year mean January streamflow varied by 32%, because of lower winter precipitation and air temperature in earlier calibration periods on calibrated parameters, which impaired the ability for models calibrated to earlier periods to simulate later periods. Peaks of actual evapotranspiration for this watershed also shifted from April to May due to different parameter values depending on the calibration period's winter air temperatures. In the St. Joseph and Escambia River watersheds, adjustments of the runoff curve number parameter could vary by 10.7% and 20.8%, respectively, while 50‐year mean monthly surface runoff simulations could vary by 23%–37% and 169%–209%, depending on the observed streamflow and precipitation of the chosen calibration period. It is imperative that calibration and validation time periods are chosen selectively instead of arbitrarily, for instance using change point detection methods, and that the calibration periods are appropriate for the goals of the study, considering possible broad effects of nonstationary time series on water balance simulations. It is also crucial that the hydrologic modelling community improves existing calibration and validation practices to better include nonstationary processes.

Occupational hazards at the Irkutsk region oil and gas production facilities

The oil and gas industry belongs to the high risk activity. Today, the enterprises engaged in this field including oil and gas production facilities implement a risk-based approach, which involves the identification of risk criteria and risk categories, timely reassessment of risks based on updated and formed normative legal documents. In this regard, the purpose of this research is the analysis of the management system of occupational hazards and measures to minimize them using innovations and innovative solutions at the oil and gas production facilities in the Irkutsk region of the Russian Federation. The object of the study is working conditions and occupational hazards at the oil and gas production facilities of two leading oil companies of the Irkutsk region: they are the Irkutsk branch of Gazprom Bureniye LLC and the Irkutsk branch of RN-Bureniye LLC. As a result possible reasons for the discrepancy between the physical factors of the working environment of oil industry workers when pеrforming works on oil rigs are analyzed. Professional risks having been assessed, a register of high-risk professions and hazardous areas of technological processes under the operation of oil and gas drilling rigs has been compiled. The professions studied in this paper are classified as high-risk and medium-risk ones. It is found out that the negative effects of moving machines and mechanisms, general vibration, local vibration, noise, low air temperatures in winter are unacceptable. To minimize unacceptable risks, it is proposed to introduce a low-cost technology for visualizing hazardous areas on a drilling rig with the installation of proven innovative safety barriers in addition to the related training of employees.

Good-quality Long-term Forecast of Spring-summer Flood Runoff for Mountain Rivers

The universal simulation model was developed with the use of system-analytical modeling to ensure a long-term forecast of mountain river runoff during spring-summer floods. Prediction quality of this SAM-model is characterized by Nash-Sutcliffe efficiency of 0.68–0.88 and is very high for long-term flood forecasts, including ones for inundations and mountain reservoirs filling in spring. The model was tested on the example of 34 medium and small rivers (1630 values of runoff observations for 1951–2016) located in the Altai-Sayan mountain country (2,000,000 km2). Its input factors include monthly precipitation, monthly mean air temperature, GIS data on landscape structure and orography of river basins. Meteorological factors are calculated as percentage of their “in situ” long-term mean values averaged for the whole study area. This helps to explain and quantify the influence of autumn-winter-spring soaking, freezing and thawing of mountain landscape soils on spring-summer flood. We apply a simple novel method to evaluate model sensitivity to variations in environmental factors expressed in terms of their contribution to variance of the observed flood runoff. It turns out that sensitivity of the latter decreases in the following sequence of factors: autumn precipitation, landscape structure of river basins, winter precipitation, winter air temperature, landscape altitude. The developed SAM-model provides a three-month lead-time estimate of runoff in a high water period with the threefold less variance as compared to forecasts based on the observed long-term mean values.

Indoor Daylighting and Thermal Response of a Passive Solar Building to Selective Components of Solar Radiation

Solar radiation provides the most significant natural energy in buildings for space heating and daylighting. Due to atmospheric interference, solar radiation received at the Earth’s surface consists of direct beam and diffuse radiation, where diffuse can be further broken down into longwave and visible radiation. Although each of these components co-occurs, their influence on the indoor visual and thermal conditions of a building differ. This study aims to analyze the influence of the various components of solar radiation on the indoor thermal and daylighting of a passive solar building. Thus, a pyrheliometer, pyranometer, shaded-pyranometer, and pyrgeometer mounted on a SOLYS 2 (Kipp & Zonen, Delft, Netherlands) dual Axis sun tracker, were used to monitor direct, global horizontal, diffuse and downward longwave radiation, respectively. The seasonal indoor air temperature and relative humidity were measured using an HMP 60 temperature relative humidity probe. A Li-210R photometric sensor was used to monitor the indoor illuminance. The summer and winter indoor air temperature, as well as relative humidity, were found to be influenced by diffuse horizontal and global horizontal irradiance, respectively. In summer, the indoor air temperature response to diffuse horizontal irradiance was 0.7 °C/ħW/m2 and 1.1 °C/ħW/m2 to global horizontal irradiance in winter, where ħ is 99.9 W/m2. The indoor daylighting which was found to be above the minimum office visual task recommendation in most countries, but within the useful daylight illuminance range was dominated by direct normal irradiance. A response of 260 lux/ħW/m2 was observed. The findings of the study support the strategic locating of the windows in passive solar design. However, the results show that north-facing clerestory windows without shading device could lead to visual discomfort.

Temporal Variability of Equivalent Black Carbon Components in Atmospheric Air in Southern Poland

This study assesses the air quality in Zabrze (southern Poland) based on the ambient concentrations of equivalent black carbon (eBC). eBC measurement campaigns were carried out from April 2019 to March 2020 using a modern AE33 Aethalometer, accompanied by parallel measurements of gaseous pollutants, PM10 and meteorological parameters. The use of the two-component AE33 model allows for the determination of the eBC from fossil fuel combustion (eBCff) and biomass burning (eBCbb). The obtained results showed a clear seasonal variability of eBC concentrations, with higher average levels in the heating season (4.70 µg·m−3) compared to the non-heating one (1.79 µg·m−3). In both seasons, the eBCff component had a dominant share in total eBC, which indicates significant emissions from the combustion of fossil fuels for heating purposes and from local traffic sources. The obtained results showed high correlation coefficients with gaseous and particulate pollutants, with the strongest relationship for eBC and carbon monoxide (CO). During the non-heating and heating period, both anticyclone and cyclone systems played an important role in shaping eBC, eBCff and eBCbb concentrations. High concentrations of all components occurred with a significant decrease in air temperature and solar radiation in winter.

Forecasting the Permanent Loss of Lake Ice in the Northern Hemisphere Within the 21st Century

AbstractLake ice cover is essential to conserving the global freshwater supply for the 50 million lakes that freeze each winter. Here, we ask when lakes across the Northern Hemisphere may permanently lose ice cover. A K‐means cluster analysis from 31 lakes identified four clusters of lakes vulnerable to losing ice cover, including shallow and deep lakes in regions where winter air temperatures hover ∼0 °C and larger and deeper lakes in colder regions. By the end of this century, we estimate that up to 5,679 lakes of 1.35 million HydroLAKES may permanently lose ice cover if greenhouse gas emissions (GHG) continue to be emitted at current levels. In the Northern Hemisphere, lakes in southern and coastal regions, some of which are among the largest lakes in the world and in close proximity to large human populations, are the most vulnerable to permanently losing ice.

Changes in Air Temperature and Snow Cover in Winter in Poland

The primary objective of the paper was to characterize the climatic conditions in the winter season in Poland in the years 1966/67–2019/20. The study was based on daily values of minimum (Tmin) and maximum air temperature (Tmax), and daily values of snow cover depth. The study showed an increase in both Tmin and Tmax in winter. The most intensive changes were recorded in north-eastern and northern regions. The coldest winters were recorded in the first half of the analyzed multiannual period, exceptionally cold being winters 1969/70 and 1984/85. The warmest winters occurred in the second half of the analyzed period and among seasons with the highest mean Tmax, particularly winters 2019/20 and 1989/90 stood out. In the study period, a decrease in snow cover depth statistically significant in the majority of stations in Poland was determined, as well as its variability both within the winter season and multiannual.

Response of Permafrost Thermal Regime to Climate Change over Northern Hemisphere in the 21st Century

Based on the CMIP5 simulation and numerical model, the permafrost thermal regimes over Northern Hemisphere land during the early (2016-2035), middle (2046-2065) and late (2080-2099) period of 21st century are projected, and its relationship with climate change is also analyzed. The results show that, relative to the reference period of 1986-2005, the mean annual ground temperature (MAGT) over Northern Hemisphere shows an increasing trend, with a decreasing trend of the depth of zero annual amplitude (DZAA), and the most significant changes occur in Siberia, Tibetan Plateau, Canada arctic and Alaska, and the changes in MAGT and DZAA grow larger with time and emission, especially during the LP for RCP8.5, MAGT will increase by 4 and DZAA decreases by 1.5 m (the relative change exceeds 20%) in most regions. The changes of permafrost in the 21st century mainly depend on the changes of cold permafrost. The relationship between MAGT and air temperature as well as that between DZAA and air temperature suggests that the increase of MAGT and the decrease of DZAA are related to the increase of air temperature in winter, especially in January. However, the rate of change in MAGT and DZAA gradually declines, with the temperature increasing.

Restoration of woodland belts and sustainable development of agroecosystems of steppe zone of the Orenburg oblast (Russia)

Orenburg oblast is situated in the steppe zone. The climate is continental, characterized by a large amplitude of fluctuations in both summer and winter air temperatures, and insufficient precipitation. Due to such low climate potential, the development of agricultural production in the region needs constant improvement (increasing soil fertility, erosion control, planting sustainable crops). Therefore, optimization of agricultural production in order to restore the productive potential of land is one of the most actual problems in the region. Orenburg oblast due to its geographical location is characterized by dry winds, which not only dry up the soil, but also sharply reduce its fertility, effect on the water balance, and reduce yield. Therefore, the creation of forest protection treestands in this case is a priority method that contributes to the preservation of soil fertility in the region and, consequently, to the increased rate of agricultural production. In this article, we consider some species of plants belonging to the genera Sorbus L., Crataegus L., Aronia Pers., Syringa L., which have a number of positive ecological and biological characteristics, compared to plants that are widely used in forest protection plantations in the region today (Betula pendula Roth., Pinus sylvestris L., etc.). Using plants that have significant advantages in creating protective forests, it becomes possible to solve the problem of sustainable development of the land fund, and, consequently, to increase the rate of agricultural production. This will allow regulating land use processes not only at the regional level, but also at the state level.

Динамика припая Азовского моря в XXI веке

The article is dedicated to the investigation of the fast ice dynamics for the period 2000–2020 according to satellite data and field observations using GIS technologies. We used data from International Data Center – Sea Ice and coastal observation points to analyze long-term changes. Data processing and analysis was carried out using the ArcGIS 10.4 software package. As a result, data were obtained on the spatial and temporal variability of fast ice in the Sea of Azov for the 2000–2020. The area and width of fast ice, the periods of formation, destruction and duration were analyzed. The maps of the fast ice formation frequency were constructed for each month of the winter period: December–March. It is shown that the duration of fast ice on all coastal observation points decreased: for points on the northern coast Taganrog and Mariupol—by 3–5 days, for points on the southern coast of Taganrog Bay—Yeisk and Dolzhanskaya—by 10–12 days, for point Genichesk—7 days. Average long-term fast ice area for 2000–2020 is 1800 km2. But against the background of an increase in winter air temperatures, the fast ice area is decreasing, and in the last winter periods it is not observed. The width of the fast ice at the northern coast of the Sea of Azov and the Taganrog Bay is 5–10 km. In the western and southeastern parts of the sea (sections Temryuk, Arabatskaya and Obitochny), the fast ice width is 2–5 km on average over the winter and was observed in 25 % of cases.

ВЛИЯНИЕ СНЕЖНОГО ПОКРОВА НА ОХЛАЖДЕНИЕ ПОВЕРХНОСТНОГО СЛОЯ ЛЕДНИКА ВОСТОЧНЫЙ ГРЁНФЬОРД (ШПИЦБЕРГЕН)

The purpose of this research is to estimate the effect of snow cover on the store of cold of the glacier surface layer. The store of cold is a complex parameter that shows the degree of cooling of the surface layer of the glacier at the end of the cold period. This value is determined with regard for the dynamics of air temperature and snow cover, changes in the density and structure of snow, and the moisture content (water store) in the snow and firn layer by the beginning of the cold period. Analysis of data from measurements of the thermal regime of the upper 11‑meter layer of the East Grenfjord Glacier demonstrated that effect of the snow cover depth (thickness) on the store of cold is ambiguous: when the depth increases, the store of cold can both increase and decrease. For example, in the colder winter of 2013, the store of cold in the upper 11‑meter layer of the glacier was smaller than the similar value in the warmer and snowier winter of 2014. It was found that this was caused by influence of thaws and rains in the winter of 2014. They could produce changes in the structure of the snow cover: an increase in its density and hardness after freezing of ice grains, as well as increase thermal conductivity that could result in more significant cooling of the surface layer of the glacier this winter. Numerical experiments made possible to establish the dependence of the store of cold in the upper layer of the glacier on meteorological conditions and the snow depth. Calculations have shown that with the depth of 50 cm, a rise of winter air temperature by 1 °C reduces the store of cold, on average, by 8.5 MJ/m2, whereas with a snow thickness of 200 cm, the decrease is 6 MJ/m2. Increasing the snow thickness from 50 to 100 cm reduces the store of cold by 11 MJ/m2 at −6 °C, and by 15 MJ/m2 at −10 °C. And growth of snow thickness from 150 to 200 cm decreases the store of cold by 4 MJ/m2 at the temperature of −6 °C, and by 3 MJ/m2 at −10 °C. According to calculations for the compact snow with a thickness of 150 cm at −10 °C, the store of cold increases by 12% as compared with the average snow hardness. A more significant difference in the value of the store of cold happens when the stratigraphy of the snow cover is not taken into account. Note also, that when modeling the temperature regime and estimating the store of cold in the ice at the end of the cold period, one should take into account the moisture content of the upper 1-m ice layer at the end of the ablation period.

Анализ влияния Атлантико-Европейских крупномасштабных атмосферных мод на зимние аномалии температуры воздуха приземного слоя в Черноморско-Каспийском регионе

The manifestations of the main large-scale atmospheric processes, typical for the Atlantic–European sector, in winter air temperature anomalies in the Black Sea–Caspian region (40–50 °N 28–50 °E) were clarified according to the atmospheric reanalysis NCEP 20CR V2c data at an isobaric surface of 1000 hPa for 1851–2014. After removing the linear trend, the air temperature anomalies in December-January were decomposed into empirical orthogonal functions (EOF). It is shown that the first three leading EOFs describe ~ 96% of the total air temperature variability. The first EOF is a manifestation of the East Atlantic – Western Russia mode. The second EOF is due to the North Atlantic Oscillation. The third EOF corresponds to the Scandinavian pattern.

Stable isotopes in cave ice suggest summer temperatures in east-central Europe are linked to Atlantic Multidecadal Oscillation variability

Abstract. The climate of east-central Europe (ECE) is the result of a combination of influences originating in the wider North Atlantic realm, the Mediterranean Sea, and the western Asian and Siberian regions. Previous studies have shown that the complex interplay between the large-scale atmospheric patterns across the region results in strongly dissimilar summer and winter conditions on timescales ranging from decades to millennia. To put these into a wider context, long-term climate reconstructions are required, but, largely due to historical reasons, these are lacking in ECE. We address these issues by presenting a high-resolution, radiocarbon-dated record of summer temperature variations during the last millennium in ECE, based on stable isotope analysis of a 4.84 m long ice core extracted from Focul Viu Ice Cave (Western Carpathians, Romania). Comparisons with both instrumental and proxy-based data indicate that the stable isotope composition of cave ice records the changes in summer air temperature and has a similar temporal evolution to that of the Atlantic Multidecadal Oscillation on decadal to multidecadal timescales, suggesting that changes in the North Atlantic are transferred, likely via atmospheric processes towards the wider Northern Hemisphere. On centennial timescales, the data show little summer temperature differences between the Medieval Warm Period (MWP) and the Little Ice Age (LIA) in eastern Europe. These findings are contrary to those that show a marked contrast between the two periods in terms of both winter and annual air temperatures, suggesting that cooling during the LIA was primarily the result of wintertime climatic changes.

Abiotic and biotic influences on the performance of two biological control agents, Neochetina bruchi and N. eichhorniae, in the Sacramento-San Joaquin River Delta, California (USA)

Variability in the effectiveness of biological control programs can be due to a myriad of abiotic and biotic interactions. Here, we explore these interactions in relation to the suboptimal biological control on the invasive water hyacinth, Pontederia (=Eichhornia) crassipes, by two weevils, Neochetina bruchi and N. eichhorniae, in the Sacramento-San Joaquin River Delta in California, USA (Delta). We conducted monthly surveys from 2015 to 2017 throughout 1667 km2 to analyze the impacts of temperature, nutrients, river flow, pathogens and genetic variation in relation to the performance of these biological control agents. Weevils (predominantly N. bruchi) demonstrated a positive numerical response to increased nitrogen content in water hyacinth crown and roots. Weevil densities and water hyacinth biomass declined significantly during periods of high river flow. We found negative impacts of cooler temperatures on weevil performance, with a significant lagged-response of weevil densities in the field to water temperature from three months prior and a lack of population growth under laboratory conditions simulating winter air temperatures in the Delta (3.9–13.9 °C). We confirmed the presence of a microsporidian pathogen, with 10.7% average prevalence of infection across four seasons and low infection loads. In addition, we found low genetic diversity of N. bruchi in the Delta compared to native populations, low population genetic structure and a lack of genetic isolation by distance among metapopulations. Overall we conclude that cooler temperatures and periods of high river flow are likely the main factors limiting the current biological control program in the Delta.

Drivers and projections of ice phenology in mountain lakes in the western United States

AbstractClimate change is causing rapid warming and altered precipitation patterns in mountain watersheds, both of which influence the timing of ice breakup in mountain lakes. To enable predictions of ice breakup in the future, we analyzed a dataset of mountain lake ice breakup dates derived from remote sensing and historical downscaled climate data. We evaluated drivers of ice breakup, constructed a predictive statistical model, and developed projections of mountain lake ice breakup date with global climate models. Using Random Forest analysis, we determined that winter and spring cumulative snow fraction (portion of precipitation falling as snow) and air temperature are the strongest predictors of ice breakup on mountain lakes. Interactions between precipitation, cumulative winter air temperature and lake surface area indicate that shifts in air temperature and precipitation affect smaller lakes (< 2 km2) more than larger lakes (> 2–10 km2). A linear mixed effects model (RMSE of 18 d), applied with an ensemble of 15 global climate models, projected that end‐of‐century ice breakup in mountain lakes will be earlier by 25 ± 4 and 61 ± 5 (mean ± SE) days for representative concentration pathways 4.5 and 8.5, respectively.

Increased winter drownings in ice-covered regions with warmer winters.

Winter activities on ice are culturally important for many countries, yet they constitute a high safety risk depending upon the stability of the ice. Because consistently cold periods are required to form stable and thick ice, warmer winters could degrade ice conditions and increase the likelihood of falling through the ice. This study provides the first large-scale assessment of winter drowning from 10 Northern Hemisphere countries. We documented over 4000 winter drowning events. Winter drownings increased exponentially in regions with warmer winters when air temperatures neared 0°C. The largest number of drownings occurred when winter air temperatures were between -5°C and 0°C, when ice is less stable, and also in regions where indigenous traditions and livelihood require extended time on ice. Rates of drowning were greatest late in the winter season when ice stability declines. Children and adults up to the age of 39 were at the highest risk of winter drownings. Beyond temperature, differences in cultures, regulations, and human behaviours can be important additional risk factors. Our findings indicate the potential for increased human mortality with warmer winter air temperatures. Incorporating drowning prevention plans would improve adaptation strategies to a changing climate.