The modelled surface mass balance of the Antarctic Peninsula at 5.5 km horizontal resolution

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 highaccumulation 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 icesheet-integrated SMB, including ice shelves (an area of 4.1 × 10 5 km 2 ), 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 × 10 5 km 2 ) SMB (276 ± 47 Gt yr −1 ), where PR is large (276 ± 47 Gt yr −1 ), dominates over the EAP (1.7 × 10 5 km 2 ) 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 ).

Increased West Antarctic ice discharge and East Antarctic stability over the last seven years

“…Here we estimate SMB for the 2008-2015 period from Regional Atmospheric Climate Model version 2.3 (RACMO2.3) output at a horizontal resolution of 5.5 km for the Antarctic Peninsula (van Wessem et al, 2016) and 27 km elsewhere 295 (van Wessem et al, 2014). In RACMO2.3, SMB is calculated as the total precipitation (from snow and rain) minus total sublimation (directly from the surface and from drifting snow), wind-driven snow erosion, and meltwater runoff.…”

“…For the determination of ice discharge we provide a novel approach to defining the cross-sectional area of ice flow (flux gate -Section 2.2) that greatly reduces uncertainties in estimates of ice discharge. By differencing estimates of ice discharge and basal melt rates (Van Liefferinge and Pattyn, 2013) from published 55 estimates of the surface mass balance (van Wessem et al, 2016;van Wessem et al, 2014) we are able to estimate the net mass balance of the ice sheet at the basin scale, revealing recent patters of ice sheet imbalance.…”

Changes in glacier dynamics at the northern Antarctic Peninsula since 1985

“…The climatic mass balance at the northern AP shows a strong spatial 15 variability, with very high accumulation rates along the west coast, significantly lower values on the east coast and an increase towards higher altitudes (Turner, 2002;van Wessem et al 2016). Consequently, the mass input depends on the elevation range and the hypsometry.…”

“…The foehn events are characterized by strong winds 5 and high air temperatures. Consequently, the climatic mass balance (b clim ) shows a strong gradient across the mountain chain (Turner, 2002;van Wessem et al, 2016). Apart from those that are ice shelf tributaries, nearly all glaciers on the AP are marine terminating, and most of the glacier catchments extend up to the high elevation plateau regions.…”

“…at Bruce Plateau, 66.03°S, 64.07°W, Goodwind, 2013;at Detroit Plateau, 64.08°S, 59.68° W, Potocki et al, 2011, Palmer Land, 73.59° S, 70.36° W, Thomas et al, 2008) and climate models (e.g. Dee et al, 2011), whereas van Wessem et al (2016) obtained insignificant trends in precipitation.…”