Abstract
AbstractLakes and drained lake basins (DLBs) together cover up to ∼80% of the western Arctic Coastal Plain of Alaska. The formation and drainage of lakes in this continuous permafrost region drive spatial and temporal landscape dynamics. Postdrainage processes including vegetation succession and permafrost aggradation have implications for hydrology, carbon cycling, and landscape evolution. Here, we used surface nuclear magnetic resonance (NMR) and transient electromagnetic (TEM) measurements in conjunction with thermal modeling to investigate permafrost aggradation beneath eight DLBs on the western Arctic Coastal Plain of Alaska. We also surveyed two primary surface sites that served as nonlake affected control sites. Approximate timing of lake drainage was estimated based on historical aerial imagery. We interpreted the presence of taliks based on either unfrozen water estimated with surface NMR and/or TEM resistivities in DLBs compared to measurements on primary surface sites and borehole resistivity logs. Our results show evidence of taliks below several DLBs that drained before and after 1949 (oldest imagery). We observed depths to the top of taliks between 9 and 45 m. Thermal modeling and geophysical observations agree about the presence and extent of taliks at sites that drained after 1949. Lake drainage events will likely become more frequent in the future due to climate change and our modeling results suggest that warmer and wetter conditions will limit permafrost aggradation in DLBs. Our observations provide useful information to predict future evolution of permafrost in DLBs and its implications for the water and carbon cycles in the Arctic.
Highlights
Lakes and drained lake basins (DLBs) combined are estimated to cover up to ∼80% of the western Arctic Coastal Plain of Alaska (∼30,000 km2) (Grosse et al, 2013; Hinkel et al, 2005; Jones & Arp, 2015)
We interpreted the presence of taliks based on either unfrozen water estimated with surface nuclear magnetic resonance (NMR) and/or transient electromagnetic (TEM) resistivities in DLBs compared to measurements on primary surface sites and borehole resistivity logs
The surface NMR data quality was divided into three categories of signal detection (Figure 2): (1) very low signal-tonoise ratio (SNR) (∼3:1) with limited or no evidence of NMR relaxation and no peak on the Larmor frequency of water in the spectrum (Figure 2a), we interpret this as no liquid water detected; (2) low SNR (∼10:1) with evidence of exponential relaxation and an identifiable low peak at the Larmor frequency of water (Figure 2b), indicating the presence of low, but real liquid volumetric water content (VWC), and insufficient information to quantitatively interpret VWC distribution with depth; and (3) high SNR (∼30:1) with strong evidence of exponential relaxation and clear peak on Larmor frequency of water (Figure 2c), indicating ample subsurface liquid water and sufficient information to interpret VWC distribution with depth
Summary
Lakes and drained lake basins (DLBs) combined are estimated to cover up to ∼80% of the western Arctic Coastal Plain of Alaska (∼30,000 km2) (Grosse et al, 2013; Hinkel et al, 2005; Jones & Arp, 2015). Remote-sensing analysis of historical imagery of the western Arctic Coastal Plain of Alaska identified that 1–2 lakes larger than 10 ha have partially (>25% area reduction) or completely drained per year between 1955 and 2017 (Hinkel et al, 2007; Jones & Arp 2015; Jones et al, 2020), and 1,900 lakes are prone to drainage in the future (Jones et al, 2020).
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