Break-up Dates Research Articles

Drivers and consequences of apex predator diet composition in the Canadian Beaufort Sea.

Polar bears (Ursus maritimus) rely on annual sea ice as their primary habitat for hunting marine mammal prey. Given their long lifespan, wide geographic distribution, and position at the top of the Arctic marine food web, the diet composition of polar bears can provide insights into temporal and spatial ecosystem dynamics related to climate-mediated sea ice loss. Polar bears with the greatest ecological constraints on diet composition may be most vulnerable to climate-related changes in ice conditions and prey availability. We used quantitative fatty acid signature analysis (QFASA) to estimate the diets of polar bears (n = 419) in two western Canadian Arctic subpopulations (Northern Beaufort Sea and Southern Beaufort Sea) from 1999 to 2015. Polar bear diets were dominated by ringed seal (Pusa hispida), with interannual, seasonal, age- and sex-specific variation. Foraging area and sea ice conditions also affected polar bear diet composition. Most variation in bear diet was explained by longitude, reflecting spatial variation in prey availability. Sea ice conditions (extent, thickness, and seasonal duration) declined throughout the study period, and date of sea ice break-up in the preceding spring was positively correlated with female body condition and consumption of beluga whale (Delphinapterus leucas), suggesting that bears foraged on beluga whales during entrapment events. Female body condition was positively correlated with ringed seal consumption, and negatively correlated with bearded seal consumption. This study provides insights into the complex relationships between declining sea ice habitat and the diet composition and foraging success of a wide-ranging apex predator.

Implications of climate variability and changing seasonal hydrology for subarctic riverbank erosion

Warmer climatic conditions have been associated with numerous hydrologic changes that may impact riverbank erosion in cold regions, but the net effect is not well understood. We used regression and correlation analyses to examine the relationships among subarctic riverbank erosion and seasonal hydrology, the impact of climate change and variability, and the societal implications. Geomorphic change (loss and gain of vegetated land) was mapped along several river reaches in the Yukon River Basin, Alaska, throughout 1984 and 2017 using Landsat satellite imagery. Annual erosion rates were estimated from these spatial data. At most study sites, erosion rates (km2/year) were either positively correlated (r = 0.68–0.84, p = 0.0085–0.061) with monthly mean discharge within the cold season or inversely correlated (r = − 0.74 – −0.62, p < 0.10) with river ice breakup date in the spring. These proximate controls on erosion, in turn, were influenced both by climate variability and long-term climatic change. We conclude that increased cold season discharge and earlier freshet that occurs under warmer conditions enhance riverbank erosion in most areas. Climate-related changes to fluvial dynamics may impact communities through effects on infrastructure, travel safety, channel navigability, fish and wildlife habitat, and access to subsistence resources.

Ecosystem response to earlier ice break-up date: Climate-driven changes to water temperature, lake-habitat-specific production, and trout habitat and resource use.

Climate warming has yielded earlier ice break-up dates in recent decades for lakes leading to water temperature increases, altered habitat, and both increases and decreases to ecosystem productivity. Within lakes, the effect of climate warming on secondary production in littoral and pelagic habitats remains unclear. The intersection of changing habitat productivity and warming water temperatures on salmonids is important for understanding how climate warming will impact mountain ecosystems. We develop and test a conceptual model that expresses how earlier ice break-up dates influence within lake habitat production, water temperatures and the habitat utilized by, resources obtained and behavior of salmonids in a mountain lake. We measured zoobenthic and zooplankton production from the littoral and pelagic habitats, thermal conditions, and the habitat use, resource use, and fitness of Brook Trout (Salvelinus fontinalis). We show that earlier ice break-up conditions created a "resource-rich" littoral-benthic habitat with increases in zoobenthic production compared to the pelagic habitat which decreased in zooplankton production. Despite the increases in littoral-benthic food resources, trout did not utilize littoral habitat or zoobenthic resources due to longer durations of warm water temperatures in the littoral zone. In addition, 87% of their resources were supported by the pelagic habitat during periods with earlier ice break-up when pelagic resources were least abundant. The decreased reliance on littoral-benthic resources during earlier ice break-up caused reduced fitness (mean reduction of 12g) to trout. Our data show that changes to ice break-up drive multi-directional results for resource production within lake habitats and increase the duration of warmer water temperatures in food-rich littoral habitats. The increased duration of warmer littoral water temperatures reduces the use of energetically efficient habitats culminating in decreased trout fitness.

Long-term variations of river ice breakup timing across Canada and its response to climate change

River ice breakup has extensive implications on cold-region hydrological, ecological and river morphological systems. However, spatial and temporal breakup patterns under the changing climate are not well explored on large scale. This study discusses the spatial-temporal variations of breakup timing over terrestrial ecozones and five selected river basins of Canada based on long-term (1950–2016) data record. The link between the discovered patterns and climatic drivers (including air temperature, snowfall and rainfall), as well as elevation and anthropogenic activities are analyzed. An overall earlier breakup trend is observed across Canada and the spring air temperature is found to be the main driver behind it. However, the most pronounced warming trends across Canada is observed in winter. Spring warming trend is not as strong as winter warming and even becomes weak as period changes from 1950–2016 to 1970–2016, resulting in more stations showing later and significant later breakup during 1970–2016. Breakup pattern also displays evident spatial differences. Significant earlier breakup trends are mainly seen in western Canada (e.g. the Nelson River basin) and Arctic where spring warming trends are evident. Later and mixed breakup trends are generally identified in regions with weak warming or even cooling trends, such as Atlantic Canada and the St. Lawrence River basin. Spring snowfall generally delays breakup. Spring rainfall usually advances breakup dates while winter-rainfall can also delay breakup through refreezing. The increased snowfall in the north and increased rainfall in the south may be the reason why breakup timing is more sensitive to climatic warming in lower latitude regions than in higher latitude regions. Additionally, breakup timing in main streams and large rivers appears to be less sensitive to the warming trend than the headwaters and small tributaries. Elevation and flow regulation are also found to be contributing factors to the changes in breakup timing.

A phenological comparison of grizzly (Ursus arctos) and polar bears (Ursus maritimus) as waterfowl nest predators in Wapusk National Park

Relatively little is known about the feeding ecology of grizzly bears (Ursus arctos) in Wapusk National Park. Other ursids, polar bears (Ursus maritimus), are well known predators of waterfowl nests in the area, and grizzly bears could feasibly make use of such resources. However, since the arrival of polar bears on land in the spring is largely dependent on date of sea-ice breakup, the timing of predation by each bear species may differ. We investigated the timing of bear predation in common eider (Somateria mollissima sedentaria) and lesser snow goose (Anser caerulescens caerulescens) colonies from 2012 to 2018 using nest cameras. We observed grizzlies consuming eggs of both species in all years except 2013 and confirmed that at least two individual grizzlies occupied the park in 2016. In the 3 years when both grizzly and polar bears were detected, grizzlies were observed earlier in the year than polar bears and had greater overlap with an estimated availability index of incubating waterfowl. We hypothesize that grizzly bears could have earlier access to waterfowl eggs in the park, potentially reducing availability of these terrestrial foods to polar bears.

Application of an ice-ocean coupled model to Bohai Sea ice simulation

The HAMSOM (Hamburg Shelf Ocean Model), a high-resolution regional ice-ocean coupled model, was applied to investigate the seasonal evolution of Bohai Sea ice for winter 2015/2016. HAMSOM was initialized with monthly climatological temperature and salinity data from WOA13 and driven by hourly meteorological data obtained from the NCEP above the sea surface and tides at the open boundary. The ice model used here is a modified Hibler-type dynamic-thermodynamic sea ice model based upon viscous-plastic rheology. The ice extent, concentration, area, thickness, length of ice season as well as the distance between the top of Liaodong Bay (North China) and the outer ice edge line were simulated and compared with the observed data. Three types of modeling experiments were carried out to investigate the effects of wind, tide, and both wind and tide on Bohai Sea ice. The results show that wind, as both a dynamic and a thermodynamic factor, has a significant impact on the ice thickness, ice area, and ice-freezing and ice breakup dates as well as the ice velocity, while tides are a dynamic factor that influences only the ice velocity. During the severe ice period, the wind speed intensity increased by 25%, the average ice thickness thickened by approximately 4.0 cm in Liaodong Bay, approximately 2.1 cm in Bohai Bay and approximately 2.5 cm in Laizhou Bay, and the total ice coverage area and total ice actual area increased by about 2×104 km2 and 1.4×104 km2, respectively. While the tidal amplitude intensity increased by 25%, the average ice velocity increased by approximately 0.1 m/s.

Interrelated ecological impacts of climate change on an apex predator.

Climate change has broad ecological implications for species that rely on sensitive habitats. For some top predators, loss of habitat is expected to lead to cascading behavioral, nutritional, and reproductive changes that ultimately accelerate population declines. In the case of the polar bear (Ursus maritimus), declining Arctic sea ice reduces access to prey and lengthens seasonal fasting periods. We used a novel combination of physical capture, biopsy darting, and visual aerial observation data to project reproductive performance for polar bears by linking sea ice loss to changes in habitat use, body condition (i.e., fatness), and cub production. Satellite telemetry data from 43 (1991–1997) and 38 (2009–2015) adult female polar bears in the Baffin Bay subpopulation showed that bears now spend an additional 30 d on land (90 d in total) in the 2000s compared to the 1990s, a change closely correlated with changes in spring sea ice breakup and fall sea ice formation. Body condition declined for all sex, age, and reproductive classes and was positively correlated with sea ice availability in the current and previous year. Furthermore, cub litter size was positively correlated with maternal condition and spring breakup date (i.e., later breakup leading to larger litters), and negatively correlated with the duration of the ice‐free period (i.e., longer ice‐free periods leading to smaller litters). Based on these relationships, we projected reproductive performance three polar bear generations into the future (approximately 35 yr). Results indicate that two‐cub litters, previously the norm, could largely disappear from Baffin Bay as sea ice loss continues. Our findings demonstrate how concurrent analysis of multiple data types collected over long periods from polar bears can provide a mechanistic understanding of the ecological implications of climate change. This information is needed for long‐term conservation planning, which includes quantitative harvest risk assessments that incorporate estimated or assumed trends in future environmental carrying capacity.

Modeling River Ice Breakup Dates by k-Nearest Neighbor Ensemble

Forecasting of river ice breakup timing is directly related to the local ice-caused flooding management. However, river ice forecasting using k-nearest neighbor (kNN) algorithms is limited. Thus, a kNN stacking ensemble learning (KSEL) method was developed and applied to forecasting breakup dates (BDs) for the Athabasca River at Fort McMurray in Canada. The kNN base models with diverse inputs and distance functions were developed and their outputs were further combined. The performance of these models was examined using the leave-one-out cross validation method based on the historical BDs and corresponding climate and river conditions in 1980–2015. The results indicated that the kNN with the Chebychev distance functions generally outperformed other kNN base models. Through the simple average methods, the ensemble kNN models using multiple-type (Mahalanobis and Chebychev) distance functions had the overall optimal performance among all models. The improved performance indicates that the kNN ensemble is a promising tool for river ice forecasting. The structure of optimal models also implies that the breakup timing is mainly linked with temperature and water flow conditions before breakup as well as during and just after freeze up.

ИССЛЕДОВАНИЕ ИЗМЕНЕНИЙ ДИНАМИКИ СТРАТОСФЕРЫ СЕВЕРНОГО ПОЛУШАРИЯ В XXI ВЕКЕ ПО РАСЧЕТАМ КЛИМАТИЧЕСКОЙ МОДЕЛИ ИВМ РАН

Simulations of 5th version of INM RAS (Institute of Numerical Mathematics of the Russian Academy of Science) climate model performed in the framework of CMIP6 project for the future climate under ssp2–4.5 (moderate) and ssp5–8.5 (business as usual or hard) scenarios of green house gases (GHG) increase are employed to analyze temperature, zonal mean wind, stratospheric polar vortex, planetary wave activity, meridional circulation, sudden stratospheric warming (SSW) events, and stratospheric circulation spring break-up date changes during boreal winters from 2015 to 2100. Comparison of averages over two periods of 2080–2100 and 2015–2035 revealed that temperature will decrease from 1° in the lower stratosphere to 4° in the upper stratosphere under moderate scenario and up to 11° under hard scenario. Cooling of stratosphere will be accompanied by strengthening of zonal circulation and planetary wave activity propagation in the middle – upper stratosphere that in turn leads to increase (stronger under hard scenario) of planetary wave with zonal wave number 1 amplitude (wavenumber 1). 13 major sudden stratospheric warming events and 16 very cold stratospheric winter seasons were revealed under hard scenario. Under both scenarios early spring break-up dates will be accompanied by stronger wavenumber 1 in comparison with winter seasons with later spring break-up dates. Strengthening of zonal mean meridional circulation is expected in the late XXI century

MODIS-observed variations of lake ice phenology in Xinjiang, China

Lakes sensitively respond to global and regional climate change, especially in arid areas. Using Moderate Resolution Imaging Spectroradiometer (MODIS) daily snow products, the lake ice phenology of 23 lakes in the Xinjiang Uygur Autonomous Region of China from 2001 to 2018 was extracted based on thresholds of ice/water pixel numbers, and their change trends over 18 years were calculated. The results of MODIS-derived lake ice phenology showed consistent variations with existing ice phenology data sets derived from passive microwave data. Generally, lakes in Xinjiang begin to freeze from October to December every year, and their ice cover periods end from March to June. The average ice cover duration for the 23 lakes is 167 days, of which 16 lakes have an average shortening rate of − 1.08 days/year and seven lakes have an average extending rate of 1.18 days/year. The majority of lakes experienced later freeze-up (17 lakes) and earlier break-up (18 lakes) from 2001 to 2018. Lake ice phenology is affected by both climatic factors and lake physicochemical characteristics, in which freeze-up dates are more easily affected by lake-specific factors such as lake area (r = 0.535), while climatic factors especially water surface temperature have greater impacts on lake break-up dates (r = − 0.874). Compared to air temperature, water surface temperature changes have a more direct influence on the variations in lake ice phenology, 1° increase in water surface temperature may cause the ice cover duration to decrease by 12 days, while precipitation changes have almost no effect on the lakes in Xinjiang. In some cases, lake changes such as changes to the area and mineralization may also have dominant impacts on lake ice phenology.

Influence of climate change on the ice conditions of the Curonian Lagoon

Summary The Curonian Lagoon is a shallow freshwater lagoon of significant environmental value in the south-eastern part of the Baltic Sea. The objective of the study was to evaluate changes of ice indices (duration, thickness and breakup dates) of this lagoon and to assess their possible tendencies in the 21st century. A methodology was developed combining the assessment of past changes (1960–2017) of ice indices and their projections in the near (2021–2040) and far (2081–2100) future periods using a hydrometeorological database, statistical methods and regression analysis as well as regional climate models and RCP scenarios. Climate change has a considerable impact on ice conditions in the Curonian Lagoon. During the historical period of 1960–2017, the Curonian Lagoon was covered with ice for 72 days a year, ice thickness reached 23 cm, whereas ice breakup was observed in the middle of March on average. According to the different scenarios, in the near and far future periods, ice duration will last 35–45 and 3–34 days, respectively. Ice thickness is projected to be 13–15 cm in the near future, whereas, at the end of the century, it is expected to decline to 0–13 cm. In the past, the lagoon ice cover remained until the middle of the third decade of February. At the end of the 21st century, RCP8.5 scenario projects the most drastic shifts: the permanent ice cover might be absent, whereas short-term ice cover is expected to melt already in the beginning of January.

Evolution From Past to Future Conditions of Fast Ice Coverage in James Bay

Fast ice is often used by coastal communities in the James Bay area for transportation in winter using snowmobiles. Therefore, the extent of fast ice along the James Bay coastline is important for land use and any changes to these extents may have significant impacts on the lifestyles of local communities. The eastern coastline has experienced changes in recent decades that might have affected the ice processes, namely hydrologic modifications due to hydroelectric development by Hydro-Québec along with climatic changes that have been observed worldwide. A statistical analysis in the form of summarized ice charts of the ice extents in the middle of winter have been compiled for the past four decades to highlight any recent changes in ice coverage using data from satellite imagery and ice charts produced by the Canadian Ice Service. A statistical analysis has also been carried out on the freeze-up and breakup dates using historical data. Moreover, a statistical analysis of hydrological data and climatic data has been carried out to determine the long-term and short-term trends in the parameters influencing the ice processes. After testing sensitivity of the past ice regime to climatic and hydrological parameters, the trends detected in the extents of fast ice, as well as freeze-up and breakup conditions, have been correlated with climatic parameters. Using the dominant parameters, a simplified model of the extents of fast ice has been developed, as well as criteria to determine freeze-up and breakup dates. Air temperature projections have also been obtained for two greenhouse gas emissions scenarios using global climate model results to establish future climatic conditions. Finally, projections of the fast ice regime around the year 2050 have been developed to determine a long-term trend covering both historical changes and future conditions. We expect around the year 2050 a recession of the landfast ice coverage of several kilometers, a delay of one to three weeks of the freeze-up dates and an advance of two to ten days of the breakup dates in comparison to the period of 1998-2016 in the James Bay area.

Correlates of seasonal change in the body condition of an Arctic top predator.

Climate-driven sea ice loss has led to changes in the timing of key biological events in the Arctic, however, the consequences and rate of these changes remain largely unknown. Polar bears (Ursus maritimus) undergo seasonal changes in energy stores in relation to foraging opportunities and habitat conditions. Declining sea ice has been linked to reduced body condition in some subpopulations, however, the specific timing and duration of the feeding period when bears acquire most of their energy stores and its relationship to the timing of ice break-up is poorly understood. We used community-based sampling to investigate seasonality in body condition (energy stores) of polar bears in Nunavut, Canada, and examined the influence of sea ice variables. We used adipose tissue lipid content as an index of body condition for 1,206 polar bears harvested from 2010-2017 across five subpopulations with varying seasonal ice conditions: Baffin Bay (October-August), Davis Strait and Foxe Basin (year-round), Gulf of Boothia and Lancaster Sound (August-May). Similar seasonal patterns were found in body condition across subpopulations with bears at their nadir of condition in the spring, followed by fat accumulation past break-up date and subsequent peak body condition in autumn, indicating that bears are actively foraging in late spring and early summer. Late season feeding implies that even minor advances in the timing of break-up may have detrimental effects on foraging opportunities, body condition, and subsequent reproduction and survival. The magnitude of seasonal changes in body condition varied across the study area, presumably driven by local environmental conditions. Our results demonstrate how community-based monitoring of polar bears can reveal population-level responses to climate warming in advance of detectable demographic change. Our data on the seasonal timing of polar bear foraging and energy storage should inform predictive models of the effects of climate-mediated sea ice loss.

Global Warming Influence on Major Seasonal and Intra-seasonal Rainfall Indicators for Sustainable Cocoa Production in West-central Côte d'Ivoire

Ivorian cocoa production, which still remains the driving force of the national economy today, despite the increasingly pronounced diversification of the State's resources, has long benefited from relatively favorable climatic conditions. However, since the 1970s, recurrent disruptions in key rainfall indicators for cocoa production have posed significant risks to the yields and incomes of many Ivorians who depend directly or indirectly on the agronomic performance of this speculation. Using a methodological approach based on descriptive statistical analysis, this study provides an understanding of the evolution of the main climatic factors involved in cocoa production in the Central West, which is one of the country's natural cocoa production basins. To carry out this task, daily rainfall data from Divo and Gagnoa, covering the period 1946-2015, were collected and processed. The results of the various statistical analyses indicate that the seasonal and intra-seasonal rainfall indicators in Gagnoa and Divo are generally declining after the break-up years detected in 1972 in Divo and 1966 in Gagnoa. After the breaks, the Useful Rainy Season (URS) starts later and the ends are earlier than before, which results in a shortening of the length of the URS and a reduction in the intra-seasonal rainfall totals of the two localities. Conversely, the maximum dry sequences during the URS show a slight increase after the break-up dates. The station of Gagnoa was less affected by the rainfall recession than that of Divo where the downward trend in seasonal and intra-seasonal rainfall events is more severe. This makes the Gagnoa region the one with the best rainfall capacities for cocoa production in the study area.

Validation of lake surface state in the HIRLAM v.7.4 numerical weather prediction model against in situ measurements in Finland

Abstract. The High Resolution Limited Area Model (HIRLAM), used for the operational numerical weather prediction in the Finnish Meteorological Institute (FMI), includes prognostic treatment of lake surface state since 2012. Forecast is based on the Freshwater Lake (FLake) model integrated into HIRLAM. Additionally, an independent objective analysis of lake surface water temperature (LSWT) combines the short forecast of FLake to observations from the Finnish Environment Institute (SYKE). The resulting description of lake surface state – forecast FLake variables and analysed LSWT – was compared to SYKE observations of lake water temperature, freeze-up and break-up dates, and the ice thickness and snow depth for 2012–2018 over 45 lakes in Finland. During the ice-free period, the predicted LSWT corresponded to the observations with a slight overestimation, with a systematic error of +0.91 K. The colder temperatures were underrepresented and the maximum temperatures were too high. The objective analysis of LSWT was able to reduce the bias to +0.35 K. The predicted freeze-up dates corresponded well to the observed dates, mostly within the accuracy of a week. The forecast break-up dates were far too early, typically several weeks ahead of the observed dates. The growth of ice thickness after freeze-up was generally overestimated. However, practically no predicted snow appeared on lake ice. The absence of snow, presumably due to an incorrect security coefficient value, is suggested to be also the main reason for the inaccurate simulation of the lake ice melting in spring.

Remote Sensing of Lake Ice Phenology across a Range of Lakes Sizes, ME, USA

Remote sensing of ice phenology for small lakes is hindered by a lack of satellite observations with both high temporal and spatial resolutions. By merging multi-source satellite data over individual lakes, we present a new algorithm that successfully estimates ice freeze and thaw timing for lakes with surface areas as small as 0.13 km2 and obtains consistent results across a range of lake sizes. We have developed an approach for classifying ice pixels based on the red reflectance band of Moderate Resolution Imaging Spectroradiometer (MODIS) imagery, with a threshold calibrated against ice fraction from Landsat Fmask over each lake. Using a filter derived from the Modern-Era Retrospective Analysis for Research and Applications, version 2 (MERRA-2) surface air temperature product, we removed outliers in the time series of lake ice fraction. The time series of lake ice fraction was then applied to identify lake ice breakup and freezeup dates. Validation results from over 296 lakes in Maine indicate that the satellite-based lake ice timing detection algorithm perform well, with mean absolute error (MAE) of 5.54 days for breakup dates and 7.31 days for freezeup dates. This algorithm can be applied to lakes worldwide, including the nearly two million lakes with surface area between 0.1 and 1 km2.

Reaching a breaking point: How is climate change influencing the timing of ice breakup in lakes across the northern hemisphere?

AbstractThe duration of seasonal winter ice cover has declined in many mid‐ and high‐latitude regions around the world as climate continues to warm. We obtained data on lake ice breakup dates, air temperature, precipitation, and large‐scale climate oscillations for 152 lakes across the northern hemisphere from 1951 to 2014. Ninety‐seven percent of study lakes exhibited earlier ice breakup trends. Forty‐six percent of the variation in ice breakup trends was driven by spring air temperatures and elevation across the northern hemisphere. However, changes in ice breakup have not always been in a gradual or linear pattern. Using the sequential T‐test analysis of regime shifts, we found evidence of abrupt changes in mean ice breakup for 53% of lakes with shift years identified between 1970 and 2002. Concurrently, we found abrupt changes in mean spring and winter air temperatures, winter precipitation, and large‐scale climate oscillations that occurred either the same year or 1 yr prior. Earlier ice breakup and the shortening of the ice season will have consequences for winter heritage, local economies, and lake ecosystems around the world.

Identifying historic river ice breakup timing using MODIS and Google Earth Engine in support of operational flood monitoring in Northern Ontario

River ice breakup and resulting flood risk is a nearly annual concern for communities along the five major rivers draining to the James and Hudson Bay Coasts in Ontario (Moose, Albany, Attawapiskat, Winisk and Severn Rivers). Ice breakup within this region has historically been monitored using flight reconnaissance supplemented by assessment of hydrometric data. More recently, remote sensed imagery have been used to monitor near real-time ice breakup and flood risk. However, the near real-time remotely sensed breakup information was found to have limited utility in the absence of a broader spatial and temporal understanding of breakup progression. The primary purpose of this study was to develop a method for generating a dataset of breakup dates. A secondary objective was to calculate statistics from this dataset that can be used to provide context to operational near real-time imagery analysis and improve understanding of ice processes in the study area. An automated method for detecting river ice breakup dates from 2000 to 2017 using MODIS imagery was developed. This method uses a threshold-based technique that aims to maximize river coverage and minimize effects of cloud obstruction. Image processing was completed in the high-performance Google Earth Engine application which enabled iterative classification and model calibration. The breakup date dataset was used to calculate statistics on breakup timing, duration, annual variability and breakup order. An assessment of patterns within these data is discussed, relationships between breakup timing, duration and highwater years is explored and the operational utility of these statistics is described. The classification compared well with Water Survey of Canada derived breakup dates with mean bias ranging from −2.0 days to 6.7 days and mean absolute error of 3.4 days to 6.9 days across the rivers. Latitude and distance upstream were found to be primary controls on breakup timing with drainage network configuration and reach morphology also having an influence. No relationships between highwater years and calculated breakup statistics were found. It is recommended that future studies use the dataset developed in this study in combination with hydrometric and remotely sensed data to improve prediction of highwater and understanding of breakup processes within these rivers.

Variations of Lake Ice Phenology on the Tibetan Plateau From 2001 to 2017 Based on MODIS Data

AbstractLake ice is a robust indicator of climate change. The availability of information contained in Moderate Resolution Imaging Spectroradiometer daily snow products from 2000 to 2017 could be greatly improved after cloud removal by gap filling. Thresholds based on open water pixel numbers are used to extract the freezeup start and breakup end dates for 58 lakes on the Tibetan Plateau (TP); 18 lakes are also selected to extract the freezeup end and breakup start dates. The lake ice durations are further calculated based on freezeup and breakup dates. Lakes on the TP begin to freezeup in late October and all the lakes start the ice cover period in mid‐January of the following year. In late March, some lakes begin to break up, and all the lakes end the ice cover period in early July. Generally, the lakes in the northern Inner‐TP have earlier freezeup dates and later breakup dates (i.e., longer ice cover durations) than those in the southern Inner‐TP. Over 17 years, the mean ice cover duration of 58 lakes is 157.78 days, 18 (31%) lakes have a mean extending rate of 1.11 day/year, and 40 (69%) lakes have a mean shortening rate of 0.80 day/year. Geographical location and climate conditions determine the spatial heterogeneity of the lake ice phenology, especially the ones of breakup dates, while the physico‐chemical characteristics mainly affect the freezeup dates of the lake ice in this study. Ice cover duration is affected by both climatic and lake specific physico‐chemical factors, which can reflect the climatic and environmental change for lakes on the TP.

A hydrological and water temperature modelling framework to simulate the timing of river freeze-up and ice-cover breakup in large-scale catchments

Ice phenology, defined as the timing of freeze-up and ice-cover breakup, plays a key role in streamflow regimes in cold-region river catchments. River freeze-up and ice-cover breakup events are controlled by meteorological and hydrological variables. In this study, we present a modelling framework consisting of a physically-based semi-distributed hydrological model and the integration of a 1D stream temperature model that can predict the ice duration in cold region rivers. The hydrological model provides streamflow and hydraulic parameters for the stream temperature model to obtain instream water temperature. The model was successfully applied in the Athabasca River basin in western Canada. Calibration was carried out using the water temperature recorded in the stations at the towns of Hinton, Athabasca and Fort McMurray. Model results show consistent correspondence between simulated freeze-up and breakup dates and the hydrometric station data. In the main tributaries of the basin, freeze-up timing spans from the last week of September to the second week of November and ice-cover breakup occurs from the second week of March to the last week of May. The model presents an application of water temperature and ice phenology simulation which can be incorporated in ice-jam flood forecasting and future climate change studies.