A new study, led by a number of Nunataryuk researchers, shows that optical and radar remote sensing can be used to map ice frozen to the riverbed (bedfast ice) vs. ice, resting on top of the unfrozen water layer (floating or so-called serpentine ice) within the Arctic’s largest delta, the Lena River Delta (see figure below, showing the consistent mapping of serpentine ice using optical and radar remote sensing).
They show that the serpentine ice spatially coincides with the location of thawed riverbed sediment (talik) observed with in situ geoelectrical measurements and as simulated with the thermal model (see figure below, showing remote sensing, geophysical and model data for a cross section of a Lena River channel). The spatial correspondence between the river ice regime (bedfast or serpentine) and the thermal state of the sub-river sediments demonstrates the great potential of remote sensing to identify not only the long existing taliks beneath deep river channels but also areas, subject to potential change of the ice regime, which can, in turn, trigger either formation of new permafrost or thaw of existing permafrost beneath the riverbed.
Besides insight into sub-river thermal properties, our study shows the potential of remote sensing for identifying river channels with active sub-ice flow during winter vs. channels, presumably disconnected for winter water flow. These results reveals how bedfast ice limits hydrological routing in winter compared to summer in the Lena River Delta (see figure below, showing the difference of connected channels in summer on the left compared to winter on the right).
Their results demonstrate that annual-scale monitoring of the ice regime (bedfast vs serpentine) and the deep channels position is possible. These maps may be used as an aid for summer navigation for shallow-draught vessels, particularly in regions where navigational charts may not be regularly updated (see figure below, showing a ship track of an expedition in 2016 in red and the serpentine ice indicating deep channels in black).
Read the complete article here.
Juhls, B., Antonova, S., Angelopoulos, M., Bobrov, N., Grigoriev, M., Langer, M., Maksimov, G., Miesner, F., & Overduin, P. P. (2021). Serpentine (floating) ice channels and their interaction with riverbed permafrost in the Lena River Delta, Russia. Frontiers in Earth Science, 9, 548.