New insights into the drainage of inundated Arctic polygonal tundra using fundamental hydrologic principles

Abstract

Abstract. The pathways and timing of drainage from inundated ice-wedge polygon centers in a warming climate have important implications for carbon flushing, advective heat transport, and transitions from carbon dioxide to methane dominated emissions. This research helps to understand this process by providing the first in-depth analysis of drainage from a single polygon based on fundamental hydrogeological principles. We use a recently developed analytical solution to evaluate the effects of polygon aspect ratios (radius to thawed depth) and hydraulic conductivity anisotropy (horizontal to vertical hydraulic conductivity) on drainage pathways and temporal depletion of ponded water heights of inundated ice-wedge polygon centers. By varying the polygon aspect ratio, we evaluate the effect of polygon size (width), inter-annual increases in active layer thickness, and seasonal increases in thaw depth on drainage. One of the primary insights from the model is that most inundated ice-wedge polygon drainage occurs along an annular region of the polygon center near the rims. This implies that inundated polygons are most intensely flushed by drainage in an annular region along their horizontal periphery, with implications for transport of nutrients (such as dissolved organic carbon) and advection of heat towards ice wedge tops. The model indicates that polygons with large aspect ratios and high anisotropy will have the most distributed drainage. Polygons with large aspect ratio and low anisotropy will have their drainage most focused near the their periphery and will drain most slowly. Polygons with small aspect ratio and high anisotropy will drain most quickly.

Permafrost and groundwater interaction: current state and future perspective

“…In addition, particular regions of discontinuous permafrost are entirely encircled by unfrozen ground. Another important issue in continuous permafrost environment is microtopography which can control the water balance and initiate terrestrial water drainage and discharge to the surface (Liljedahl et al, 2012;Liljedahl et al, 2016;Painter et al, 2016;Harp et al, 2020;Nitzbon et al, 2020;Painter et al, 2023). Ice-wedge polygons are examples of these kind of feature and commonly occur in polygonal tundra that occupies around 30% of the Arctic land.…”

“…These features of lowland tundra have an effect on suprapermafrost groundwater seepage into surface-water drainage channels. Transport of nutrients through the shallow groundwater fluxes into surface is greatly affected by ice-wedge polygons (Helbig et al, 2013;Harp et al, 2020). Furthermore, surface surveys conducted and data collected form remote sensing technique revealed that dramatic alteration of polygonal tundra occurred over the last decades (Liljedahl et al, 2016).…”

“…Recent studies also highlight the importance of microtopography in groundwater discharge (Liljedahl et al, 2016;Harp et al, 2020;Nitzbon et al, 2020;Painter et al, 2023). Harp et al (2020) described a new three dimensional mathematical model that demonstrated the impact of ice-wedge polygons on seeping of suprapermafrost groundwater into the surface. This water can potentially carry a significant concentration of DOC and nutrients into surface water.…”

“…The results of the simulations showed that geometric features have a strong effect on the seepage of groundwater. Studies of Harp et al (2020) focused on inundated low-centred polygons, and, as the authors stated, the noninundated low-centred and high-centred polygons may have different drainage mechanisms. Furthermore, Harp et al (2020) also revealed that polygon aspect ratios (width to thawed depth) and hydraulic conductivity anisotropy (conductivities in different directions, i.e., vertical to horizontal) influence strongly on drainage pathways and temporal decline of water volume from ice-edge polygon centres.…”

“…Studies of Harp et al (2020) focused on inundated low-centred polygons, and, as the authors stated, the noninundated low-centred and high-centred polygons may have different drainage mechanisms. Furthermore, Harp et al (2020) also revealed that polygon aspect ratios (width to thawed depth) and hydraulic conductivity anisotropy (conductivities in different directions, i.e., vertical to horizontal) influence strongly on drainage pathways and temporal decline of water volume from ice-edge polygon centres. Based on the calculations conducted by Harp et al (2020), it was concluded that decrease of the aspect ratio (thawed depth becomes deeper with respect to polygon width) causes increase in polygon volume accessibility for the drainage.…”