Understanding the Ecohydrological Role of Seasonal Ground Ice in a Boreal Peatland

• Main Author: Van Huizen, Brandon
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: University of Waterloo 2022
• Subjects: seasonal ground ice; peatlands; evapotranspiration; ground heat flux; moss surface resistance; Fort McMurray; Ice; permafrost
• Online Access: http://hdl.handle.net/10012/18440

Seasonal Ground Ice (SGI) in peatlands forms in late fall when air temperatures begin to cool, and water in peat pores freeze. It differs from permafrost peatlands in that the SGI freezes and completely melts away every fall and subsequent winter. Despite its presence in many boreal peatlands, the ecohydrological impact it has on peatland processes has been largely understudied. Large amounts of SGI require significant energy inputs every spring to melt completely, potentially reducing available energy for evapotranspiration. This is of particular importance in the Western Boreal Plains (WBP), where precipitation is often exceeded by potential evapotranspiration annually, creating a sub-humid climate. Despite this dry climate, peatlands comprise a large proportion of the landscape. Their persistence is attributed to various negative feedbacks that help reduce water losses. The melting of SGI may be one such negative feedback. Furthermore, the presence of SGI can have a profound impact on the spring freshet, influencing the peatland’s role as a source or sink of water within the landscape. Despite the potential for SGI influence on peatland ecohydrological processes, it is not well represented in SVAT models. However, properly parameterizing these effects is complicated by the apparent small scale spatial heterogeneity in SGI melting as well as the presence of bi-directional melting during the spring thaw. Finally, incorporating these processes into a model are further complicated by the poor representation of moss evaporation in such models. Therefore, the purpose of this thesis is to establish a conceptual understanding of the ecohydrological role of SGI in peatlands within the WBP and begin to incorporate some of these processes into the Cold Regions Hydrological Model (CRHM). This study took place at a Boreal fen peatland (named Pauciflora), approximately 40 km south of Fort McMurray on the Stoney Mountain complex. The conceptual role of SGI was assessed through in-situ measurements of SGI both directly by ...