Hydrometeorological forcing of coastal dynamics in the Russian Arctic:
link to erosion rates in the last decades
Abstract
Coasts in the Russian Arctic are extremely vulnerable to the ongoing
environmental changes. Temporal evolution of their retreat rates is
driven by hydrometeorological processes. Permafrost of the coastal
bluffs rapidly thaws under the influence of air and water temperature
increase. Along with that, sea ice decline results in wave energy
increase because of longer wave fetch and ice-free period when the waves
are able to erode the unprotected coasts. The combined thermal and wave
action is defined as hydrometeorological forcing of coastal erosion. We
estimated temporal variability of the air thawing index (sum of annual
positive temperatures) reflecting the thermal factor, and the wind-wave
energy flux since the 1970s for five sites in both the western and
eastern Russian Arctic where observations of coastal erosion rates
derived from both field measurements and remotely sensed data are
available: Varandey (Pechora Sea), Yamal and Ural coasts of the
Baydaratskaya Bay (Kara Sea), Cape Chukochiy (East Siberian Sea) and
Lorino (Bering Sea). We further calculated the total hydrometeorological
forcing of coastal erosion for the periods with known retreat rates and
compared the temporal variability of the two parameters. Comparison of
the hydrometeorological forcing shows a link between erosion rates and
the hydrometeorological forcing in all the areas. The best correlation
is noted for sites where remotely sensed data for relatively long
periods were analyzed. For areas with more frequent direct field
observations, the variability of the two parameters shows more
differences. Such findings imply that while long-term erosion rates are
determined by general trends of climate and sea ice extent change in the
Arctic seas, coastal retreat in one single year can be driven by local
factors, such as lake drainage, random failure of large blocks or peat
lenses, exposure and burial of ice bodies, and other reasons. Therefore
estimation of mechanisms and trends of coastal erosion in the Russian
Arctic should be made based on average retreat rates over relatively
long timescales (several years or even decades). Studies on the
variability of climate parameters were funded by the RFBR grant
18-05-60300 (S.Ogorodov, N. Shabanova). Studies on rates of coastal
erosion were funded by the RSF grant 16-17-00034 (A.Baranskaya, A.
Novikova). B.Jones was supported by US National Science Foundation award
OISE- 1927553.