Geophysical monitoring of hydrological dynamics within a discontinuous permafrost environment

Increasing temperatures are rapidly changing the Arctic ecosystem. Yet, we are missing a predictive understanding of the interactions within the bedrock to atmosphere column that are driving ecosystem evolution and carbon-climate feedback. A critical knowledge gap within these systems are the dynamics of surface water - groundwater interactions, and infiltration and groundwater flow processes, which drive permafrost thaw and biogeochemical processes. Geophysical techniques have been shown to be a valuable tool to assess the intermediate depths (1 - 10’s of m) that are particularly important to understanding the impact of climate change on permafrost thaw and related hydrological dynamics. In this study we highlight how automated geophysical monitoring can reveal rapid and heterogeneous changes in thermohydrological conditions that are characteristic for discontinuous permafrost systems.

Given the remote environment, we will first introduce the field setup that allowed us to acquire continuous data for over 4 years. We present the variations in ground conditions and associated changes in data quality, which highlight the expected poor data during the winter season, once the ground is frozen. Focusing on the monitoring data, we show that summer rainfall events drive distinct infiltration patterns at locations of a deep active layer. Snowmelt and rainfall events drive considerable variations in groundwater level, which are confirmed by borehole information and driven by flow below the permafrost. Data acquired in early winter shows spatially heterogeneous ground freezing, mostly controlled by the microtopography. These observations provide novel information that will help in better understanding the complex hydrological processes taking place in discontinuous permafrost environments, and will eventually lead to better parameterization of ecosystem models.