The impacts of regional Arctic lake change on remotely sensed methane emission hotspots in Alaska, USA

Arctic and boreal wetlands and lakes are experiencing complex ecological changes as a result of warming. The potential for rapidly thawing permafrost to promote large increases in methane (CH₄) emissions via ground subsidence and ponding (thermokarst), and permafrost carbon mineralization is of particular concern for accelerating the permafrost carbon feedback (PCF) [Turetsky et al. 2020]. However, complex hydrological dynamics produce large uncertainties regarding the sign and magnitude of carbon loss in modeling and forecasting efforts. Determining CH₄’s current and future contributions to the PCF is challenging due to sparse observations, high spatiotemporal variability, and heterogeneous Arctic landscapes. As a result, top-down (observation-based) and bottom-up (model/inventory-based) evaluations of annual Arctic and boreal CH₄ emissions disagree by 50-200% [McGuire et al. 2012; Peltola et al. 2019]. Constraining the current budget and forecast uncertainty in future Arctic emissions will require scale-bridging approaches that reconcile fine spatiotemporal variability and regional to continental scale coverage. To this end, we compiled multiple large remote sensing datasets to study relationships between Arctic lake and thermokarst landscape morphology trends with remotely-sensed (AVIRIS-NG) CH­₄ emission hotspot detections. Preliminary analyses from a lake-and-wetland-rich 1,750 km² study area of the Yukon Kuskokwim Delta, AK, USA reveal discrete correlations between recently wetted areas and CH₄ hotspot detections. However, in an analysis of over 1,200 lakes > 1 ha, hotspots were detected in greater abundance surrounding lakes that have shrunk in area since 1999 (p < 0.05) (Fig. 2). Our preliminary results imply a complex response of CH₄ emissions surrounding dynamic permafrost environments. Ongoing analyses seek to further elucidate patterns related to waterbody size, permafrost ice and carbon contents, and relationships between terrestrial and limnetic hotspot detections.