Tracer model-based quantitative separation of precipitation and permafrost waters used for evapotranspiration in a boreal forest

Abstract

Arctic precipitation (PG) that occurs as rainfall (Pr) or snowfall (Ps) depending on the prevailing climatic conditions results in seasonally specific hydrological events. Climate change can affect the PG-and permafrost-originated water (Pi) regimes, resulting in change to ecohydrological processes. However, the relative influences of source waters (i.e., Pr, Ps, and Pi) on terrestrial hydrological processes have not yet been fully established. Here, we report the development and implementation of a numerical water tracer model designed to quantify changes in the storages and fluxes of the source waters and the hydrogen and oxygen isotopic tracers associated with hydrometeorological events. The presented tracer model was used to illustrate the spatiotemporal variability of the tracers in the surface-subsurface system of a deciduous needleleaf boreal forest, and to separate the contribution rates of the tracer waters to evapotranspiration (ET). Although Ps accounted for 14%-40% of ET and the subcomponents, the contribution rates to soil evaporation and transpiration were significant only during the spring season. The major source water for soil moisture was Pr, which accounted for 80.1% of ET and showed an increasing trend. Additionally, Pr also accounted for 85.7% of transpiration. Under the present conditions of warming permafrost, Pi demonstrated negligibly low impact on ET. The tracer model was shown capable of quantifying the contribution rates of tracer waters to ET, highlighting the advantages of the tracer model for similar quantitative separation regarding future climate change.

Numerical Assessments of Excess Ice Impacts on Permafrost and Greenhouse Gases in a Siberian Tundra Site Under a Warming Climate

“…CHANGE includes a water tracer model that is designed to illustrate the spatiotemporal variability of water originating from precipitation and ground ice in the hydrologic system and quantify their contributions to hydrological processes (Park et al, 2021). It therefore has an ability to assess the contribution ratio of excess ice meltwater to the subsurface flow under future climate warming, which is important to understand the dynamics of hydrological processes.…”

“…The objective of this study was to examine the impact of excess ice melt on permafrost hydrology and associated changes in CO 2 and methane (CH 4 ) fluxes under future climate scenarios following the strongest representative concentration pathways (RCP8.5) in a tundra site in northeastern Siberia using the improved CHANGE model. We also quantified the contribution of excess ice meltwater to the surface-subsurface hydrologic system, which is likely achieved because of the inclusion of a water tracer scheme within CHANGE to track pathways of water originating from precipitation and ground ice meltwater (Park et al, 2021).…”