Investigating snowmelt infiltration into tundra soils on Qeqertarsuaq (Disko Island), Greenland

Snow represents the single largest water source in most regions of the Arctic, but few investigations of snowmelt infiltration into frozen and unfrozen soils have been conducted in this region. To investigate the infiltration of snowmelt into tundra soils, we collected vertical soil cores before snowmelt (mid-April), mid-snowmelt (mid-May), and after snowmelt (early June) from Blæsedalen, Qeqertarsuaq (Disko Island), Greenland at sites varying in soil properties, snow depth, and landscape position. Soil cores were separated into sections, after which we measured bulk density, gravimetric water content (GWC), soil texture, organic content, and the water isotope composition of the soil water of each soil core section. Water isotope composition was also measured for vertically-integrated snowpack samples at each sampling location, so that we could attribute any changes in soil moisture to infiltrating snowmelt runoff. Post-snowmelt cores were separated into frozen and unfrozen sections, to compare the infiltration of snowmelt into frozen and unfrozen soil.Initial results show that the GWC varied widely from 0.25 – 43 among soil core sections, the extremes reflecting differences between dense loamy soils with little organic material and porous, saturated peat. After snowmelt, soil water in the top 0 – 20 cm of the soil column experienced a significant shift towards the isotope composition of snow, regardless of whether the soil was frozen or not. There was little change in soil water isotope composition mid-snowmelt. Changes in GWC mirrored these results: the average GWC increased by 46% post-snowmelt in soil core sections from the top 20 cm of the soil column, with no significant change in GWC mid-snowmelt. Interestingly, frozen soils from the top 20 cm of the soil column experienced a larger increase in GWC than unfrozen soils, suggesting that frozen soils did not hinder the ability of snowmelt to infiltrate into soil. Below 20 centimetres in the soil column, no significant changes in water isotope composition or GWC were observed. We also observed no clear link between the snow water equivalent of the overlying snowpack, and the increase in GWC after snowmelt.The landscape of Qeqertarsuaq is abundant with large snow drifts that last well into July, which could provide a significant source of water for soils downslope of drifts. We were unable to test this hypothesis because an exceptionally late snowmelt meant we collected post-snowmelt soil cores immediately after soils became snow-free, giving little time for lateral runoff from melting snow drifts to travel downslope. However, we did observe that peat soils, which develop in wet areas, were often present immediately downslope from large snow drifts, while only thin organic layers combined with other vegetation covers were present upslope of snow drifts. With this study, we have been able to provide the first insights into snowmelt infiltration on Qeqertarsuaq, and how it may be playing a role in the spatial variability of soil development.