Higher surface mass balance of the Greenland ice sheet revealed by high‐resolution climate modeling

Abstract

High‐resolution (∼11 km) regional climate modeling shows total annual precipitation on the Greenland ice sheet for 1958–2007 to be up to 24% and surface mass balance up to 63% higher than previously thought. The largest differences occur in coastal southeast Greenland, where the much higher resolution facilitates capturing snow accumulation peaks that past five‐fold coarser resolution regional climate models missed. The surface mass balance trend over the full 1958–2007 period reveals the classic pattern expected in a warming climate, with increased snowfall in the interior and enhanced runoff from the marginal ablation zone. In the period 1990–2007, total runoff increased significantly, 3% per year. The absolute increase in runoff is especially pronounced in the southeast, where several outlet glaciers have recently accelerated. This detailed knowledge of Greenland's surface mass balance provides the foundation for estimating and predicting the overall mass balance and freshwater discharge of the ice sheet.

Deglacial ice sheet meltdown: orbital pacemaking and CO<sub>2</sub> effects

“…3f). Compared to high-resolution model results by Ettema et al (2009, Fig. 4b, c), the surface mass balance in CTR at present is overestimated, in particular in northeast and central Greenland.…”

Spatially extensive estimates of annual accumulation in the dry snow zone of the Greenland Ice Sheet determined from radar altimetry

“…Meanwhile, there are reports of an increase in the surface elevation at higher altitudes since 1990 (Krabill et al, 2000;Nghiem et al, 2005;Hanna et al, 2006), supporting calibrated climate models which show that some regions of the ice sheet have experienced higher than average accumulation rates, especially in the south (Burgess et al, 2010). A recent modelling study found larger than average accumulation rates across the GrIS between 1958 and 2007, and that the surface mass balance over the same period is between 32-63% higher than previous estimates (Ettema et al, 2009). However, Greenland's weather and accumulation patterns have high spatial and temporal variability (MosleyThompson et al, 2001;Steffen et al, 2004;Wang et al, 2007), and elevation changes may be caused by factors other than accumulation and melt such as snow compaction and densification processes and by the redistribution of drifting snow .…”

“…The differences seen between the model and our estimates provide insight on uncertainties in surface mass balance estimates. Assuming similar accumulation patterns, the difference would mean an uncertainty in the mean annual mass gain due to accumulation of approximately 44.5 km 3 (275 km 3 for ASIRAS and 320 km 3 for the model) if applied to a dry snow area of 7.7×10 5 km 2 (approximately 55% of the GrIS), significant if compared to a 1958-2007 estimate of total surface mass balance for the whole GrIS of of 422 ± 37 km 3 yr −1 (Ettema et al, 2009). …”

The seasonal cycle and interannual variability of surface energy balance and melt in the ablation zone of the west Greenland ice sheet

“…In the absence of detailed observations, estimating melt and runoff from the GrIS requires the use of a regional atmospheric model that solves the full surface energy balance (SEB) at high spatial resolution (Fettweis, 2007;Ettema et al, 2009;Fettweis et al, 2010). In turn, these models require validation from in situ observations at the ice sheet surface (Ettema et al, 2010a, b).…”