Edwards, T. L., Fettweis, X., Gagliardini, O., Gillet-Chaulet, F., Goelzer, H., Gregory, J.M., Hoffman, M., Huybrechts, P., Payne, A. J., Perego, M., Price, S., Quiquet, A. and Ritz, C.
Probabilistic parameterisation of the surface mass balance--elevation feedback in regional climate model simulations of the Greenland ice sheet.
The Cryosphere, 8 (1).
To link to this article DOI: 10.5194/tc-8-181-2014
We present a new parameterisation that relates surface
mass balance (SMB: the sum of surface accumulation
and surface ablation) to changes in surface elevation of the
Greenland ice sheet (GrIS) for the MAR (Modèle Atmosphérique
Régional: Fettweis, 2007) regional climate model.
The motivation is to dynamically adjust SMB as the GrIS
evolves, allowing us to force ice sheet models with SMB simulated
by MAR while incorporating the SMB–elevation feedback,
without the substantial technical challenges of coupling
ice sheet and climate models. This also allows us to assess
the effect of elevation feedback uncertainty on the GrIS
contribution to sea level, using multiple global climate and
ice sheet models, without the need for additional, expensive
We estimate this relationship separately below and above
the equilibrium line altitude (ELA, separating negative and
positive SMB) and for regions north and south of 77� N, from
a set of MAR simulations in which we alter the ice sheet surface
elevation. These give four “SMB lapse rates”, gradients
that relate SMB changes to elevation changes. We assess uncertainties
within a Bayesian framework, estimating probability
distributions for each gradient from which we present
best estimates and credibility intervals (CI) that bound 95%
of the probability. Below the ELA our gradient estimates are
mostly positive, because SMB usually increases with elevation:
0.56 (95% CI: −0.22 to 1.33) kgm−3 a−1 for the north,
and 1.91 (1.03 to 2.61) kgm−3 a−1 for the south. Above the
ELA, the gradients are much smaller in magnitude: 0.09
(−0.03 to 0.23) kgm−3 a−1 in the north, and 0.07 (−0.07 to
0.59) kgm−3 a−1 in the south, because SMB can either increase
or decrease in response to increased elevation.
Our statistically founded approach allows us to make probabilistic
assessments for the effect of elevation feedback uncertainty
on sea level projections (Edwards et al., 2014).
|Date Deposited:||26 Nov 2014 10:43|
|Last Modified:||16 Jun 2015 11:41|
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