Characterization and temporal analysis of SAR-detected superseeps near Utqiagvik, AK
Natalie Tyler, University of Alaska Fairbanks, natyler@alaska.edu (Presenter)
Melanie Engram, University of Alaska, Fairbanks, melanie.engram@alaska.edu
Hillary Nyström, University of Alaska, Fairbanks, hlsaucy@alaska.edu
Guido Grosse, Alfred Wegener Institute/University of Potsdam, guido.grosse@awi.de
Katey Marion Walter Anthony, University of Alaska, Fairbanks, kmwalteranthony@alaska.edu
Ebullition, often the dominant pathway for methane (CH4) emission from Arctic lakes, is an important consideration for the global atmospheric CH4 budget and climate models. Lake CH4 ebullition bubbles generally originate from ecologic or geologic sources. Ecologic CH4 seeps, produced through microbial decomposition of organic matter within lake sediments and the underlying talik, have been quantified and scaled based on existing field-based and remote-sensing methods. Geologic CH4 seeps, often fossil (14C-free) and originating from microbial, thermogenic, or a combination of both altering buried organics in ancient sedimentary basins, are thought to be rarer and are not well quantified. Ebullition rates from these “superseeps” are much higher than ecologic ebullition and are often strong enough to maintain holes in thick (>1 m) lake ice. Overall, quantification and upscaling of geologic CH4 seepage is challenging due to complex, site-specific geologic and cryospheric settings.
Space-borne synthetic aperture radar (SAR) is a powerful tool for detecting ecologic ebullition in Arctic lakes (Engram et al., 2020). Specifically, L-band (~24 cm wavelength) backscatter correlates with roughness caused by stratigraphically-layered ecologic CH4 bubbles trapped during lake freeze-up: the stronger the ebullition, the higher the backscatter (Engram et al, 2013). Notably, Engram et al. (unpublished data) observed very high perennial backscatter features in L- and P-band (~ 70 cm wavelength) SAR imagery at the locations of known superseeps. We previously developed an L-band SAR intensity threshold method to detect potential superseeps on a landscape-scale and identified 209 high-confidence SAR-detected superseep (SDS) sites (i.e. lakes with superseep features) in the Utqia?vik region of Alaska. Here, we present our preliminary results from: characterizing SDS to correlate them to targeted future field investigations, analyzing historical L-band SAR imagery to see how often SDS appear, and analyzing regional lake ice regime data to determine whether this influences the visibility (or lackthereof) of SDS.
Presentation: RH_Tyler_0_136_31.pptx
Associated Project(s):
Presentation Type: Research Highlight
Session: Carbon Dynamics
Session Date: Tuesday (5/10) 10:30 AM