Abstract
Abstract. This study presents a high-resolution (∼ 5.5 km) estimate of surface mass balance (SMB) over the period 1979–2014 for the Antarctic Peninsula (AP), generated by the regional atmospheric climate model RACMO2.3 and a firn densification model (FDM). RACMO2.3 is used to force the FDM, which calculates processes in the snowpack, such as meltwater percolation, refreezing and runoff. We evaluate model output with 132 in situ SMB observations and discharge rates from six glacier drainage basins, and find that the model realistically simulates the strong spatial variability in precipitation, but that significant biases remain as a result of the highly complex topography of the AP. It is also clear that the observations significantly underrepresent the high-accumulation regimes, complicating a full model evaluation. The SMB map reveals large accumulation gradients, with precipitation values above 3000 mm we yr−1 in the western AP (WAP) and below 500 mm we yr−1 in the eastern AP (EAP), not resolved by coarser data sets such as ERA-Interim. The average AP ice-sheet-integrated SMB, including ice shelves (an area of 4.1 × 105 km2), is estimated at 351 Gt yr−1 with an interannual variability of 58 Gt yr−1, which is dominated by precipitation (PR) (365 ± 57 Gt yr−1). The WAP (2.4 × 105 km2) SMB (276 ± 47 Gt yr−1), where PR is large (276 ± 47 Gt yr−1), dominates over the EAP (1.7 × 105 km2) SMB (75 ± 11 Gt yr−1) and PR (84 ± 11 Gt yr−1). Total sublimation is 11 ± 2 Gt yr−1 and meltwater runoff into the ocean is 4 ± 4 Gt yr−1. There are no significant trends in any of the modelled AP SMB components, except for snowmelt that shows a significant decrease over the last 36 years (−0.36 Gt yr−2).
Highlights
The Antarctic Peninsula (AP) is one of the most rapidly changing regions on Earth (Turner et al, 2005)
RACMO2.3 has been adapted for use over the large ice sheets of Greenland and Antarctica: it includes a multi-layer snow model to calculate melt, percolation, refreezing and runoff of liquid water (Ettema et al, 2010); a prognostic scheme to calculate surface albedo based on snow grain size (Kuipers Munneke et al, 2011); and a routine that simulates the interaction of drifting snow with the surface and the lower atmosphere (Lenaerts et al, 2012a)
We assume these to be in balance (SMB − D = 0), as the data date from well before the significant thinning and retreat of the Larsen B ice shelf, that culminated in its disintegration in 2002 (Wuite et al, 2015); we exclude basins that are too small to be resolved by the model resolution, or were not in balance
Summary
The Antarctic Peninsula (AP) is one of the most rapidly changing regions on Earth (Turner et al, 2005). Remote sensing techniques, such as radar backscatter to identify melt episodes (Barrand et al, 2013b) or satellite products like the Gravity Recovery and Climate Experiment (GRACE; Tapley et al, 2004), often don’t resolve the small-scale features of the AP SMB Other methods, such as using ice discharge estimates to calculate the mass balance of the ice sheet, or satellite altimetry to measure elevation changes, need detailed SMB fields (Rignot et al, 2011; Mouginot et al, 2012; Wuite et al, 2015), or require a correction for firn processes (Gunter et al, 2009), which is dependent on the SMB.
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