Arctic Moisture Source for Eurasian Snow Cover Variations in Autumn

Abstract:

Global warming is enhanced at high northern latitudes where the Arctic surface air
temperature has risen at twice the rate of the global average in recent decades - a
feature called Arctic amplification. This recent Arctic warming signal likely results
from several factors such as the albedo feedback due to a diminishing cryosphere,
enhanced poleward atmospheric and oceanic transport, and change in humidity. Moreover, Arctic
summer sea-ice extent has declined by more than 10% per decade since the start of
the satellite era (e.g. Stroeve et al., 2012), culminating in a new record low in
September 2012.
Eurasian snow cover changes have been suggested as a driver for changes in the
Arctic Oscillation and might provide a link between sea ice decline in the Arctic
during summer and atmospheric circulation in the following winter. However, the
mechanism connecting snow cover in Eurasia to sea ice decline in autumn is still
under debate.

Our analysis focuses on sea ice decline in the Barents-Kara Sea region, which allows
us to specify regions of interest for FLEXPART forward and backwards moisture
trajectories. Based on Eularian and Lagrangian diagnostics from ERA-INTERIM, we
can address the origin and cause of late autumn snow depth variations in a dense
(snow observations from 820 land stations), unutilized observational datasets over the
Commonwealth of Independent States.
Open waters in the Barents and Kara Sea have been shown to increase the diabatic
heating of the atmosphere, which amplifies baroclinic cyclones and might induce a
remote atmospheric response by triggering stationary Rossby waves (Honda et al.
2009).
In agreement with these studies, our results show enhanced storm activity originating
at the Barents and Kara with disturbances entering the continent through a small
sector from the Barents and Kara Seas. Maxima in storm activity trigger increasing uplift, often
accompanied by positive snowfall and snow depth anomalies.
We show that declining sea ice in the Barents and Kara Seas acts as moisture source
for enhanced Siberian snow cover as a result of changed tropospheric moisture
transport. Transient disturbances enter the continent from the Barents and Kara Seas
region, related to anomalies in the planetary wave pattern and move southward along
the Ural mountains.