Large eddy simulations of the interaction between the Atmospheric
Boundary Layer and degrading Arctic permafrost
Abstract
Arctic permafrost thaw holds the potential to drastically alter the
Earth’s surface in Northern high latitudes.
We utilize high-resolution Large Eddy Simulations to investigate the
impact of the changing surfaces onto the neutrally stratified
Atmospheric Boundary Layer (ABL). A stochastic surface model based on
Gaussian Random Fields modeling typical permafrost landscapes is
established in terms of two land cover classes: grass land and open
water bodies, which exhibit different surface roughness length and
surface sensible heat flux. A set of experiments is conducted where two
parameters, the lake areal fraction and the surface correlation length,
are varied to study the sensitivity of the boundary layer with respect
to surface heterogeneity.
Our key findings from the simulations are the following: The lake areal
fraction has a substantial impact on the aggregated sensible heat flux
at the blending height. The larger the lake areal fraction, the smaller
the sensible heat flux. This result gives rise to a potential feedback
mechanism. When the Arctic dries due to climate heating, the interaction
with the ABL may accelerate permafrost thaw. Furthermore, the blending
height shows significant dependency on the correlation length of the
surface features.
A longer surface correlation length causes an increased blending height.
This finding is of relevance for land surface models concerned with
Arctic permafrost as they usually do not consider a heterogeneity metric
comparable to the surface correlation length.