The future of Antarctica’s surface winds simulated by a high-resolution global climate model: 1. Model description and validation

Abstract

One of the key components of Antarctica’s harsh climate is its renowned katabatic winds, which are among the fiercest surface winds on Earth. Caused primarily by strong surface cooling over the sloping ice surface, these semipermanent winds result primarily from the strong surface temperature inversion and associated temperature deficit between the surface layer and the free atmosphere aloft. Katabatic winds exert a strong effect on the mass budget of the Antarctic ice sheet by affecting snowdrift (sublimation) and by (partially) regulating the net atmospheric moisture transports toward the Antarctic. It has been suggested that greenhouse warming may lead to reduced surface cooling and weakened katabatic winds. This is tested by using a global climate model (EC-Earth) in prescribed sea surface temperature simulations of the present-day (2002–2006) and future (2094–2098) climates. Because simulated topographically induced katabatic winds are likely to depend on the model grid, we employ two model resolutions: (1) T159L62 (~100 km, 62 vertical levels) and (2) T799L91 (~20 km, 91 vertical levels). It is shown here that present-day surface winds over Antarctica in high resolution are generally stronger than in low resolution, especially in the escarpment region with its steep orography. Simulated surface winds are generally underestimated with respect to observations, in particular the strongest winds (occurring over steep slopes), and especially in low resolution. The seasonal cycle in surface winds is simulated fairly accurately. Surface temperatures are also relatively well simulated (when corrected for elevation differences), especially in high resolution.