Late Quaternary and Modern Evolution of Permafrost Coasts at Beliy Island, Kara Sea

Baranskaya, A.V.; Novikova, A.V.; Shabanova, N.; Romanenko, F., and Ogorodov, S., 2020. Late Quaternary and modern evolution of permafrost coasts at Beliy Island, Kara Sea. In: Malvárez, G. and Navas, F. (eds.), Global Coastal Issues of 2020. Journal of Coastal Research, Special Issue No. 95, pp. 356–361. Coconut Creek (Florida), ISSN 0749-0208. The low coasts of Beliy Island, Kara Sea, composed of perennially frozen sands and silts with peat are extremely vulnerable to all changes in sea level and climate conditions in the Arctic. The complex Holocene history of the island is reflected in sediments outcropping in its coastal bluffs. Modern erosion leads to destruction of these bluffs, continuing to change the topography of the island. To reconstruct Late Quaternary history, coastal exposures were investigated. They generally consist of three units: the lower clays and sands with plant debris, parallel and rippled lamination formed in shallow marine conditions in MIS 3. The middle sandy unit with allochtonuous peat lenses was deposited in the mid-Holocene (5 to 8 ka BP) in coastal conditions. The upper peats, sandy loams and silts accumulated in continental conditions after 5 ka. To estimate modern coastal erosion rates, multitemporal satellite imagery (1969-2016) was used. The western coast retreated at higher average rates than the eastern coast (1.9±0.2 m/y and 1.2±0.2 m/y, respectively). Extreme rates during 47 years were higher from the eastern side (4.6 m/y compared to 3.1 m/y in the west). Both mean and extreme erosion rates are higher than the known erosion intensity of the Kara Sea coastal dynamics monitoring sites, evidencing considerable vulnerability of the low coasts to erosion in the changing climate. Evolution of the hydrometeorological parameters affecting coastal erosion in the XX-XXI century was estimated. High average retreat rates must have happened in the 2000s-2010s as a result of both temperature and wave energy increase providing unprecedent environmental forcing of coastal dynamics.