Role of model initialization for projections of 21st-century Greenland ice sheet mass loss

TY - JOUR

T1 - Role of model initialization for projections of 21st-century Greenland ice sheet mass loss

AU - Adalgeirsdóttir, G.

AU - Aschwanden, A.

AU - Khroulev, C.

AU - Boberg, F.

AU - Mottram, R.

AU - Lucas-Picher, P.

AU - Christensen, J. H.

PY - 2014/1/1

Y1 - 2014/1/1

N2 - Model simulations of the Greenland ice sheet contribution to 21st-century sea-level rise are performed with a state-of-the-art ice-sheet model (Parallel Ice Sheet Model (PISM)). The climate-forcing fields are obtained from the European Union's Seventh Framework Programme project ice2sea, in which three regional climate models are used to dynamically downscale two scenarios (A1B and E1) from two general circulation models (ECHAM5 and HadCM3). To assess the sensitivity of the projections to the model initial state, four initialization methods are applied. In these experiments, the simulated contribution to sea-level rise by 2100 ranges from an equivalent of 0.2 to 6.8 cm. The largest uncertainties arise from different formulations of the regional climate models (0.8-3.9 cm) and applied scenarios (0.65-1.9 cm), but an important source of uncertainty is the initialization method (0.1-0.8 cm). These model simulations do not account for the recently observed acceleration of ice streams and consequent thinning rates, the changing ice discharge that may result from the spatial and temporal variability of ocean forcing, or the feedback occurring between ice-sheet elevation changes and climate forcing. Thus the results should be considered the lower limit of Greenland ice sheet contributions to sea-level rise, until such processes have been integrated into large-scale ice-sheet models.

AB - Model simulations of the Greenland ice sheet contribution to 21st-century sea-level rise are performed with a state-of-the-art ice-sheet model (Parallel Ice Sheet Model (PISM)). The climate-forcing fields are obtained from the European Union's Seventh Framework Programme project ice2sea, in which three regional climate models are used to dynamically downscale two scenarios (A1B and E1) from two general circulation models (ECHAM5 and HadCM3). To assess the sensitivity of the projections to the model initial state, four initialization methods are applied. In these experiments, the simulated contribution to sea-level rise by 2100 ranges from an equivalent of 0.2 to 6.8 cm. The largest uncertainties arise from different formulations of the regional climate models (0.8-3.9 cm) and applied scenarios (0.65-1.9 cm), but an important source of uncertainty is the initialization method (0.1-0.8 cm). These model simulations do not account for the recently observed acceleration of ice streams and consequent thinning rates, the changing ice discharge that may result from the spatial and temporal variability of ocean forcing, or the feedback occurring between ice-sheet elevation changes and climate forcing. Thus the results should be considered the lower limit of Greenland ice sheet contributions to sea-level rise, until such processes have been integrated into large-scale ice-sheet models.

KW - Ice and climate

KW - Ice-sheet modeling

UR - http://www.scopus.com/inward/record.url?scp=84909996017&partnerID=8YFLogxK

U2 - 10.3189/2014JoG13J202

DO - 10.3189/2014JoG13J202

M3 - Journal article

AN - SCOPUS:84909996017

SN - 0022-1430

VL - 60

SP - 782

EP - 794

JO - Journal of Glaciology

JF - Journal of Glaciology

IS - 222

ER -