The Cold Region Critical Zone in Transition: Responses to Climate Warming and Land Use Change

Abstract

Global climate warming disproportionately affects high-latitude and mountainous terrestrial ecosystems. Warming is accompanied by permafrost thaw, shorter winters, earlier snowmelt, more intense soil freeze-thaw cycles, drier summers, and longer fire seasons. These environmental changes in turn impact surface water and groundwater flow regimes, water quality, greenhouse gas emissions, soil stability, vegetation cover, and soil (micro)biological communities. Warming also facilitates agricultural expansion, urban growth, and natural resource development, adding growing anthropogenic pressures to cold regions’ landscapes, soil health, and biodiversity. Further advances in the predictive understanding of how cold regions’ critical zone processes, functions, and ecosystem services will continue to respond to climate warming and land use changes require multiscale monitoring technologies coupled with integrated observational and modeling tools. We highlight some of the major challenges, knowledge gaps, and opportunities in cold region critical zone research, with an emphasis on subsurface processes and responses in both natural and agricultural ecosystems. Expected final online publication date for the Annual Review of Environment and Resources, Volume 46 is October 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Mobilization of subsurface carbon pools driven by permafrost thaw and reactivation of groundwater flow: a virtual experiment

“…Figure 5 illustrates the hydrogeological, thermal, and biogeochemical data needed to constrain the model's flow and transport parameters. Of these, the data most lacking are the biogeochemical observations that drive DOC production and mineralization rates (Pi et al 2021, Wright et al 2022.…”

“…Just as important as organic carbon content and distribution with depth is the bioavailability of permafrost organic carbon and DOC (e.g. molecular structure and chemical recalcitrance) for which there are even scarcer measurements (Pi et al 2021). DOC mineralization is driven by biogeochemical conditions such as aquifer/soil mineralogy, pH, dissolved oxygen content, redox conditions, and microbial activity.…”

The Spatiotemporal Variability of Snowpack and Snowmelt Water 18O and 2H Isotopes in a Subarctic Catchment

“…Changes in air temperatures, precipitation patterns, and moisture conditions are producing unprecedented changes in snow accumulation and melt in northern regions (Arp et al., 2015; Irannezhad et al., 2022; Kiewiet et al., 2022; Rasouli et al., 2022; Rixen et al., 2022; Ruosteenoja et al., 2020; Vormoor et al., 2015). The changes in magnitude and timing of snow precipitation and snowmelt runoff have gradually resulted in a hydrological regime shift from a snowmelt to a rainfall‐dominated system in cold climate regions (Berghuijs et al., 2014; Bintanja & Andry, 2017), with varying feedbacks at a catchment scale (Ala‐aho et al., 2021; Meriö et al., 2019; Pi et al., 2021). Meltwater is vital for replenishing water storage and exporting solutes and nutrients (Ågren et al., 2010; Tomco et al., 2019).…”

Nutrient-limited subarctic caves harbour more diverse and complex bacterial communities than their surface soil

“…These effects are exacerbated at high latitudes where ecosystem dynamics are tightly linked to natural freezing and thawing cycles [ 2 ]. Our knowledge of subarctic ecosystems and their responses to disrupted annual climatic cycles is growing [ 3 ], but the knowledge of underground ecosystem dynamics, such as in caves, has remained largely neglected. Cave ecosystems differ substantially from surface ecosystems due to the lower diurnal and seasonal variation in temperature, and their higher humidity [ 4 ].…”