C23C-0799
The Surface Mass Balance of the Antarctic Peninsula at 5.5 km horizontal resolution, as simulated by a regional atmospheric climate model

Tuesday, 15 December 2015
Poster Hall (Moscone South)
Melchior van Wessem1, Carleen Reijmer2, Michiel R van den Broeke3, Stefan Ligtenberg4, Ted A Scambos5, Nicholas E Barrand6, Willem Jan Van De Berg2, Elizabeth R Thomas7, Jan Wuite8, Erik van Meijgaard9 and John Turner7, (1)Institute for Marine and Atmospheric Research Utrecht, Utrecht, 3584, Netherlands, (2)Institute for Marine and Atmospheric Research Utrecht, Utrecht, Netherlands, (3)Utrecht University, Utrecht, Netherlands, (4)University Utrecht / IMAU, Utrecht, Netherlands, (5)National Snow and Ice Data Center, Boulder, CO, United States, (6)British Antarctic Survey, Cambridge, United Kingdom, (7)NERC British Antarctic Survey, Cambridge, United Kingdom, (8)ENVEO, Innsbruck, Austria, (9)Royal Netherlands Meteorological Institute, De Bilt, Netherlands
Abstract:
The Antarctic Peninsula (AP) is one of the most rapidly changing regions on earth, but limited detailed information is available about AP climate due to a lack of observational data. Here, we present a high-resolution (5.5 km) estimate of the surface mass balance (SMB) for the AP, from 1979 to 2014, calculated by the regional atmospheric climate model RACMO2.3, that is specifically adapted for use over the polar regions. Next to this, a firn densification model is used to calculate the processes in the snowpack, such as firn compaction and meltwater percolation, refreezing, and runoff. A comparison with the few available in-situ observations shows that the AP SMB is well modeled, but that discrepancies remain that are mainly related to the highly variable AP topography compared to the model resolution.

Integrated over an ice sheet area of 4.1 105 km2, the climatological (1979-2014) SMB of the AP amounts to 351 Gt y-1 (with interannual variability = 58 Gt y-1), which mostly consists of snowfall (363 ± 56 Gt y-1). The other SMB components, sublimation, drifting snow erosion and meltwater runoff, are small (11, 0.5 and 4 Gt y-1, respectively).

The AP mountains act as an important climate barrier, leading to distinct differences between the climate of the western AP (WAP) and the eastern AP (EAP). For instance, 77% of all AP snowfall falls over the WAP, where strong orographic forcing leads to snowfall rates >4 m w.e. y-1 on the northwestern slopes, while snowfall rates are <400 mm w.e. y-1 over the EAP ice shelves. These results, and further investigations of this sharp west-to-east climate distinction, clearly highlight the different forcing mechanisms of the SMB over the WAP and the EAP: over the WAP most snowfall is orographically induced, while over the EAP it is generated by depressions over the Weddell Sea. Furthermore, no significant trends are found in any of the SMB components, except for a slight decrease in snowmelt.

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