Patterns and Variations of Snow Accumulation over Greenland, 1979–98, from ECMWF Analyses, and Their Verification

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Abstract
ECMWF monthly climate analyses were used to retrieve surface temperature, precipitation, evaporation/sublimation, and in conjunction with a simple meteorological model, snow accumulation over Greenland for 1979–98. The modeled snow accumulation is compared with existing observational maps of Greenland accumulation and mass balance, and with widely distributed coincident and contemporaneous ice-core data, primarily from NASA's Program in Arctic Regional Climate Assessment (PARCA) program. ECMWF-derived accumulation gave more realistic values for substantial (2–3-km elevation) areas of the “intermediate” inland plateau than previous methods, although the estimates are still (∼20%–30%) too low over central Greenland. Overall, this ECMWF-driven model provides a reasonable first-order depiction, among the best currently available, of snow accumulation and its interannual variations. Mean annual ECMWF precipitation (snow accumulation) for the whole island (Greenland area >2 km) was 0.314 (0.260) m yr−1, with standard deviations (demarcating interannual variation) of 0.108 (0.098) m yr−1. The underlying cumulative 20-yr changes in precipitation and accumulation of, respectively, +0.044 and +0.019 m yr−1 (20 yr)−1 are therefore insignificant, neither are there any striking trends for the individual monthly (January–December) series. However, in line with other recent results, accumulation decreased substantially in southeast and northwest Greenland and increased in the southwest and northeast. Notable [∼2°–4°C (20 yr)−1] rises in 2-m air temperature in April, September, and November, possibly related to changes in the length of the melt season, may have increased ablation of the ice sheet and require key attention in determining the surface mass balance.