Analyzing floating and bedfast lake ice regimes across Arctic Alaska using 25 years of space-borne SAR imagery

Contrasting lake ice responses to winter climate indicate future variability and trends on the Alaskan Arctic Coastal Plain

“…Peninsula study areas correspond to a recently completed multi-temporal late winter SAR analysis from 1992-2016 (Engram et al 2018). In addition to providing comparable 25 year records of bedfast ice extent, this study also reports basic lake-centric landscape attributes and their variability.…”

“…Many lakes in this study area are oriented NNW to SSE (Carson and Hussey 1962) and are of thermokarst origin with shallow bathymetry (<2 m depth) (Brewer 1958). Engram et al (2018) reported that 52% of the Barrow Peninsula lake area had bedfast ice averaged over a 25 year period. The Fish Creek study area is located on the Inner ACP with 1331 lakes covering 15% of a 1265 km 2 area.…”

“…Due to lower ice content permafrost in this region, lakes are not considered of 'true' thermokarst origin (Jorgenson and Shur 2007), though thermokarst processes result in lake expansion and a large portion of lakes are formed and shaped by fluvial processes as well (Jones et al 2017). Engram et al (2018) reported that 52% of the Fish Creek lake area had bedfast ice averaged over the same 25 year period. Both study areas lie in close proximity to the Arctic Sea coastline ( figure 1(a)), yet the Barrow Peninsula juts out prominently into the Arctic Ocean with the Chukchi Sea to the west and the Beaufort Sea to the east, whereas Fish Creek lies adjacent to the Colville River delta that enters the Beaufort Sea at Harrison Bay.…”

“…Remote sensing of bedfast and floating lake ice As described in Engram et al (2018), C-band SAR can be used to accurately determine lake ice regimes in shallow lakes because of the interaction of microwave energy with the physical properties of lake ice and ability to image at night and through dry snow to detect the presence or absence of liquid water below ice. In this study, we compared Sentinel-1 data acquired over the Barrow Peninsula on 12 April 2016 as reported in Engram et al (2018) and RADARSAT-2 data for Fish Creek acquired 9 April 2016 with a new Sentinel-1 image that covered both study areas on 27-April in 2017. April SAR scenes were selected to capture ice conditions as close as possible to MIT, but before the onset of spring melt, which typically occurs in mid-May, to avoid dampening the SAR signal from the presence of liquid water in melting snow or ponded on the ice surface.…”

“…Climate model experiments demonstrate the role of sea ice decline in this lake ice response by isolating the effects of early winter warming and snowfall in the growth of lake ice (Alexeev et al 2016), but also underscore the complex role of snowfall amount and timing. An updated multitemporal SAR analysis for the Barrow Peninsula and other regions of Arctic Alaska in fact reveal very high interannual variability and more complex lake responses to winter climate than only considering air temperature would suggest (Engram et al 2018).…”