Abstract
Abstract. The interior of western Canada, like many similar cold mid- to high-latitude regions worldwide, is undergoing extensive and rapid climate and environmental change, which may accelerate in the coming decades. Understanding and predicting changes in coupled climate–land–hydrological systems are crucial to society yet limited by lack of understanding of changes in cold-region process responses and interactions, along with their representation in most current-generation land-surface and hydrological models. It is essential to consider the underlying processes and base predictive models on the proper physics, especially under conditions of non-stationarity where the past is no longer a reliable guide to the future and system trajectories can be unexpected. These challenges were forefront in the recently completed Changing Cold Regions Network (CCRN), which assembled and focused a wide range of multi-disciplinary expertise to improve the understanding, diagnosis, and prediction of change over the cold interior of western Canada. CCRN advanced knowledge of fundamental cold-region ecological and hydrological processes through observation and experimentation across a network of highly instrumented research basins and other sites. Significant efforts were made to improve the functionality and process representation, based on this improved understanding, within the fine-scale Cold Regions Hydrological Modelling (CRHM) platform and the large-scale Modélisation Environmentale Communautaire (MEC) – Surface and Hydrology (MESH) model. These models were, and continue to be, applied under past and projected future climates and under current and expected future land and vegetation cover configurations to diagnose historical change and predict possible future hydrological responses. This second of two articles synthesizes the nature and understanding of cold-region processes and Earth system responses to future climate, as advanced by CCRN. These include changing precipitation and moisture feedbacks to the atmosphere; altered snow regimes, changing balance of snowfall and rainfall, and glacier loss; vegetation responses to climate and the loss of ecosystem resilience to wildfire and disturbance; thawing permafrost and its influence on landscapes and hydrology; groundwater storage and cycling and its connections to surface water; and stream and river discharge as influenced by the various drivers of hydrological change. Collective insights, expert elicitation, and model application are used to provide a synthesis of this change over the CCRN region for the late 21st century.
Highlights
Introduction and objectiveThe interior of western Canada is a region undergoing rapid, widespread, and severe hydro-climatic and environmental change
Against this backdrop of change, western Canada has been subjected to a series of recent, and in some instances record-breaking, extreme events such as floods, droughts, and wildfires
Changing Cold Regions Network (CCRN) developed a plausible scenario of post-fire replacement of evergreen needleleaf forest (ENF) with deciduous broadleaf forest (DBF) across the Boreal Forest, as described in the Appendix, for the purpose of use in hydrological model future projections (Fig. 6)
Summary
The interior of western Canada is a region undergoing rapid, widespread, and severe hydro-climatic and environmental change. In conjunction with the experimental and observational program, modelling research aimed at improving the capability of fine- and large-scale models to represent key cold-region processes and to diagnose the complex and interacting factors underlying the observed changes over the CCRN region These models have begun to be used, in conjunction with expert elicitation, to examine likely future system trajectories for the purposes of informing management and policy and addressing other stakeholder concerns. This article draws together the expert understanding and process insights from CCRN, together with modelling results at different scales, to examine the key drivers of change and to highlight the most likely anticipated future system trajectories across the interior of western Canada This follows Part 1 (Stewart et al, 2019), which synthesized CCRN’s collective assessments of future climate conditions and the associated seasonal patterns, along with particular P - and temperature-related phenomena.
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