Assessing the Influence of Climate Forcing Data Resolution on Simulations of Glacier and Freshwater Dynamics for the Flade Isblink Ice Cap, Northeast Greenland

Abstract

High-resolution climate data is crucial for accurate glacier modeling in topographically complex regions. This study investigates the necessity of such data for accurate simulations of glacier and freshwater dynamics for the Flade Isblink Ice Cap (FIIC), Northeast (NE) Greenland. It also explores the potential of achieving comparable results using coarse-resolution global datasets with region-specific scaling. The study employed an advanced subdivision of FIIC, consisting of 299 glaciers, including six active marine-terminating ones. Four climate datasets (ERA5, CRU, W5E5, and ERA-Interim dynamically downscaled using polar WRF for NE Greenland) with 5-50 km spatial resolutions were used to force the Open Global Glacier Model (OGGM) from 2014 to 2018. OGGM was calibrated glacier-by-glacier against high-resolution geodetic-altimetric mass balance, frontal ablation, and volume data. Sensitivity analyses were conducted with and without regional scaling for all selected climate datasets and calibration parameters. The high-resolution WRF dataset provided an accurate initial regional volume estimate (with a minimal deviation of -0.6 % from the reference) without any local corrections, while other datasets underestimated volume, increasing with decreasing resolution from 8 % to 15 %. However, applying regional temperature bias and precipitation factor significantly improved the accuracy of these estimates, reducing the underestimation from just 2.1 % to 2.4 %. Sensitivity analysis revealed that the precipitation factor has a moderate influence, while temperature bias has a higher influence on the modeled volume. Without scaling, coarse datasets underestimated annual freshwater runoff by 25 % to 34 %, but with regional scaling, this discrepancy was markedly reduced to a near alignment with the WRF dataset at 0.5 % to 1.6 %, corresponding to 9.8 Gt/yr. Across datasets, summer months (June, July, August) runoff estimates showed no significant differences (p>0.05) after regional scaling. The study concludes that high-resolution climate data enhances the accuracy of initial volume estimates, thereby increasing confidence in simulated results. However, appropriate local adjustments to coarser datasets can yield comparable glacier and freshwater runoff simulations. Initial volume estimates are crucial for future projections. Future modeling efforts will explore the sensitivities of regional scaling and parametrization on improving projections of freshwater contributions into the ocean and their feedback on glacier-ocean interactions.