Abstract
Abstract. Permafrost is an important feature of cold-region hydrology, particularly in river basins such as the Mackenzie River basin (MRB), and it needs to be properly represented in hydrological and land surface models (H-LSMs) built into existing Earth system models (ESMs), especially under the unprecedented climate warming trends that have been observed. Higher rates of warming have been reported in high latitudes compared to the global average, resulting in permafrost thaw with wide-ranging implications for hydrology and feedbacks to climate. The current generation of H-LSMs is being improved to simulate permafrost dynamics by allowing deep soil profiles and incorporating organic soils explicitly. Deeper soil profiles have larger hydraulic and thermal memories that require more effort to initialize. This study aims to devise a robust, yet computationally efficient, initialization and parameterization approach applicable to regions where data are scarce and simulations typically require large computational resources. The study further demonstrates an upscaling approach to inform large-scale ESM simulations based on the insights gained by modelling at small scales. We used permafrost observations from three sites along the Mackenzie River valley spanning different permafrost classes to test the validity of the approach. Results show generally good performance in reproducing present-climate permafrost properties at the three sites. The results also emphasize the sensitivity of the simulations to the soil layering scheme used, the depth to bedrock, and the organic soil properties.
Highlights
Earth system models (ESMs) are widely used to project climate change, and they show a current global warming trend that is expected to continue during the 21st century and beyond (IPCC, 2014)
Permafrost is an important feature of cold regions, such as the Mackenzie River basin, and needs to be properly represented in land surface hydrological models, especially under the unprecedented climate warming trends that have been observed in these regions
We analysed the conventional layering schemes used by other LSMs, which tend to use an exponential formulation to maximize the number of layers near the surface and minimize the total number of layers (Oleson et al, 2013; Park et al, 2014)
Summary
Earth system models (ESMs) are widely used to project climate change, and they show a current global warming trend that is expected to continue during the 21st century and beyond (IPCC, 2014). Recent analysis of trends in Arctic freshwater inputs (Durocher et al, 2019) highlights that Eurasian rivers show a significant annual discharge increase during the 1975–2015 period, while in North America, only rivers flowing into the Hudson Bay region in Canada show a significant annual discharge change during that same period. Those rivers in Canada flowing directly into the Arctic, of which the Mackenzie River provides the majority of flow, show very little change at the annual scale. Jacques and Sauchyn, 2009; Walvoord and Striegl, 2007)
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