Recent circum-Arctic ice-wedge degradation and its hydrological impacts
2016
Ice-wedges are common permafrost features formed
over hundreds to thousands of years of repeated frost
cracking and ice vein growth. We used field and remote
sensing observations to assess changes in areas
dominated by ice-wedges, and we simulated the effects
of those changes on snow accumulation and runoff.
We show that top melting of ice-wedges and subsequent
ground subsidence has occurred at multiple
sites in the North American and Russian Arctic. At
most sites, melting ice-wedges have initially resulted
in increased wetness contrast across the landscape,
evident as increased surface water in the ice-wedge
polygon troughs and somewhat drier polygon centers.
Most areas are becoming more heterogeneous with
wetter troughs, more small ponds (themokarst pits
forming initially at ice-wedge intersections and then
spreading along the troughs) and drier polygon centers.
Some areas with initial good drainage, such as
near creeks, lake margins, and in hilly terrain, highcentered
polygons form an overall landscape drying
due to a drying of both polygon centers and troughs.
Unlike the multi-decadal warming observed in permafrost
temperatures, the ice-wedge melting that we
observed appeared as a sub-decadal response, even
at locations with low mean annual permafrost temperatures
(down to -14 °C). Gradual long-term air
and permafrost warming combined with anomalously
warm summers or deep snow winters preceded the
onset of the ice-wedge melting. To assess hydrological
impacts of ice-wedge melting, we simulated tundra
water balance before and after melting. Our coupled
hydrological and thermal model experiments applied
over hypothetical polygon surfaces suggest that
1. ice-wedge melting that produces a connected
trough-network reduces inundation and increases
runoff, and that
2. changing patterns of snow distribution due to
differential ground subsidence has a major control
on ice-wedge polygon tundra water balance
despite an identical snow water equivalent at
the landscape-scale.
These decimeter-scale geomorphic changes are expected
to continue in permafrost regions dominated
by ice-wedge polygons, with implications for landatmosphere
and land-ocean fluxes of water, carbon,
and energy.
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