Diagnosing changes in glacier hydrology from physical principles using a hydrological model with snow redistribution, sublimation, firnification and energy balance ablation algorithms

Pietroniro

et al. 2022

Hydrological Processes

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Cold regions provide water resources for half the global population yet face rapid change. Their hydrology is dominated by snow, ice and frozen soils, and climate warming is having profound effects. Hydrological models have a key role in predicting changing water resources but are challenged in cold regions. Ground‐based data to quantify meteorological forcing and constrain model parameterization are limited, while hydrological processes are complex, often controlled by phase change energetics. River flows are impacted by poorly quantified human activities. This paper discusses the scientific and technical challenges of the large‐scale modelling of cold region systems and reports recent modelling developments, focussing on MESH, the Canadian community hydrological land surface scheme. New cold region process representations include improved blowing snow transport and sublimation, lateral land‐surface flow, prairie pothole pond storage dynamics, frozen ground infiltration and thermodynamics, and improved glacier modelling. New algorithms to represent water management include multistage reservoir operation. Parameterization has been supported by field observations and remotely sensed data; new methods for parameter identification have been used to evaluate model uncertainty and support regionalization. Additionally, MESH has been linked to broader decision‐support frameworks, including river ice simulation and hydrological forecasting. The paper also reports various applications to the Saskatchewan and Mackenzie River basins in western Canada (0.4 and 1.8 million km2). These basins arise in glaciated mountain headwaters, are partly underlain by permafrost, and include remote and incompletely understood forested, wetland, agricultural and tundra ecoregions. These illustrate the current capabilities and limitations of cold region modelling, and the extraordinary challenges to prediction, including the need to overcoming biases in forcing data sets, which can have disproportionate effects on the simulated hydrology.

Section: Discussionmentioning

confidence: 99%

Advances in modelling large river basins in cold regions with Modélisation Environmentale Communautaire—Surface and Hydrology (MESH), the Canadian hydrological land surface scheme

Wheater

Pietroniro

et al. 2022

Hydrological Processes

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“…1), were chosen for this research, namely the Peyto Glacier research basin (PGRB; 22.43 km 2 ) in Banff National Park and Athabasca Glacier research basin (AGRB; 29.3 km 2 ) in Jasper National Park. The details of these basins are provided by Pradhananga and Pomeroy (2022) and Pradhananga et al (2021). Both glaciers are instrumented with on-ice meteorological stations on the lower ice tongues of the glacier and off-ice meteorological stations on moraine below the tongue, and their outlet streams are gauged at the outlets of their current proglacial lakes.…”

Section: Study Basinsmentioning

confidence: 99%

Section: Crhm-glacier Modelmentioning

confidence: 99%

“…The CRHM-glacier model (Pradhananga and Pomeroy, 2022), developed in the Cold Regions Hydrological Modelling platform (Pomeroy et al, 2007), was applied in this study to evaluate the impacts of changes in climate and in glacier configuration on the hydrology of glacierized basins. CRHM-glacier is a physically based, flexible, multi-physics hydrological model (Pradhananga and Pomeroy, 2022). It downscales and distributes meteorological variables (shortwave and longwave radiation, air temperature, relative humidity, wind speed, precipitation, and its phase) to differing slopes, aspects, elevations, and groundcover defined by hydrological response units (HRUs), using in-built algorithms and macros (Ellis et al, 2010;Harder and Pomeroy, 2013).…”

Section: Crhm-glacier Modelmentioning

confidence: 99%

“…It downscales and distributes meteorological variables (shortwave and longwave radiation, air temperature, relative humidity, wind speed, precipitation, and its phase) to differing slopes, aspects, elevations, and groundcover defined by hydrological response units (HRUs), using in-built algorithms and macros (Ellis et al, 2010;Harder and Pomeroy, 2013). The HRUs used to discretize these basins are presented in Pradhananga and Pomeroy (2022). CRHM-glacier simulates the hydrology of both glacier and non-glacier areas in a basin.…”

Section: Crhm-glacier Modelmentioning

confidence: 99%

See 2 more Smart Citations

Recent hydrological response of glaciers in the Canadian Rockies to changing climate and glacier configuration

Pradhananga

Hydrol. Earth Syst. Sci.

2022

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Abstract. Mountain snow and ice greatly influence the hydrological cycle of alpine regions by regulating both the quantity of and seasonal variations in water availability downstream. This study considers the combined impacts of climate and glacier changes due to recession on the hydrology and water balance of two high-elevation basins in the Canadian Rockies. A distributed, physically based, uncalibrated glacier hydrology model developed in the Cold Regions Hydrological Modelling platform (CRHM) was used to simulate the glacier mass balance and basin hydrology of the Peyto and Athabasca glacier basins in Alberta, Canada. Bias-corrected reanalysis data were used to drive the model. The model calculates the water balance of glacierized basins, influenced by the surface energy and mass balance, and considers the redistribution of snow by wind and avalanches. It was set up using hydrological response units based on elevation bands, surface slope, and aspect, as well as changing land cover. Aerial photos, satellite images and digital elevation models (DEMs) were assimilated to represent the changing configurations of glacier area and the exposure of ice and firn. Observations of glacier mass balance, snow, and glacier ice surface elevation changes at glacier and alpine tundra meteorological stations and streamflow discharge at the glacier outlets were used to evaluate the model performance. Basin hydrology was simulated over two periods, 1965–1975 and 2008–2018, using the observed glacier configurations for those time periods. Both basins have undergone continuous glacier loss over the last 3 to 5 decades, leading to a 6 %–31 % reduction in glacierized area, a 78 %–109 % increase in ice exposure, and changes to the elevation and slope of the glacier surfaces. Air temperatures are increasing, mainly due to increasing winter maximum and summer minimum daily temperatures. Annual precipitation has increased by less than 11 %, but rainfall ratios have increased by 29 %–44 %. The results show that changes in both climate and glacier configuration have influenced the melt rates and runoff and a shift of peak flows in the Peyto Glacier basin from August to July. Glacier melt contributions increased/decreased from 27 %–61 % to 43 %–59 % of the annual discharges. Recent discharges were 3 %–19 % higher than in the 1960s and 1970s. The results suggest that increased exposure of glacier ice and lower surface elevation due to glacier thinning were less influential than climate warming in increasing streamflow. Streamflow from these glaciers continues to increase.

Hydrological process controls on streamflow variability in a glacierized headwater basin

Aubry‐Wake

Pradhananga

2022

Hydrological Processes

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Mountain glacierized headwaters are currently witnessing a transient shift in their hydrological and glaciological systems in response to rapid climate change. To characterize these changes, a robust understanding of the hydrological processes operating in the basin and their interactions is needed. Such an investigation was undertaken in the Peyto Glacier Research Basin, Canadian Rockies over 32 years (1988–2020). A distributed, physically based, uncalibrated glacier hydrology model was developed using the modular, object‐oriented Cold Region Hydrological Modelling Platform to simulate both on and off‐glacier high mountain processes and streamflow generation. The hydrological processes that generate streamflow from this alpine basin are characterized by substantial inter‐annual variability over the 32 years. Snowmelt runoff always provided the largest fraction of annual streamflow (44% to 89%), with smaller fractional contributions occurring in higher streamflow years. Ice melt runoff provided 10% to 45% of annual streamflow volume, with higher fractions associated with higher flow years. Both rainfall and firn melt runoff contributed less than 13% of annual streamflow. Years with high streamflow were on average 1.43°C warmer than low streamflow years, and higher streamflow years had lower seasonal snow accumulation, earlier snowmelt and higher summer rainfall than years with lower streamflow. Greater ice exposure in warmer, low snowfall (high rainfall) years led to greater streamflow generation. The understanding gained here provides insight into how future climate and increased meteorological variability may impact glacier meltwater contributions to streamflow and downstream water availability as alpine glaciers continue to retreat.