– contributed by Jan Lenaerts, IMAU, Utrecht University, The Netherlands. Published as a result of a CliC co-sponsored 2013 Ice Rises workshop.

Fig. RACMO2 topography, doi: 10.3189/2014JoG14J040Ice rises, grounded features surrounded by floating ice shelves, are abundant on the Antarctic ice sheet. They are important for ice sheet stability, since they keep the ice shelf in place, thereby preventing the upstream ice from discharging into the ocean. Moreover, since the ice around ice rises flows very slowly, ice cores drilled locally may reveal the climate and glaciation history of Antarctica.

The importance of ice rises in ice sheet stability and climate reconstruction was discussed in August 2013 during a workshop in Trømso, Norway, which was partially sponsored by CliC. A team of experts was brought together to discuss latest scientific results and future directions in Antarctic ice rise research. One of the most pressing subjects involved the topography of ice rises: they are typically tens to hundreds of meter higher than the flat ice shelf, which might lead to important spatial variations in climate and accumulation. These variations were described and analysed using a unique combination of atmospheric model output, and firn core measurements and radar observations recently collected in East Antarctica in a recent paper. We found that ice rises have a strong orographic effect on precipitation, with a typical two- to five-fold increase in the amount of snowfall on the windward side of ice rises with respect to the leeward side. We also found spatial variability in near-surface temperature and wind around ice rises, enhancing snow redistribution and sublimation.

Our results are important for the ice coring community: an ice core on the windward side of an ice rise will retrieve annually-resolved, recent accumulation history, whereas a core on the lee side of the ice rise will allow climate reconstructions further back in time, but with poorer temporal resolution. We conclude that these climate and accumulation variations need to be considered in ice shelf mass balance studies and studies on Antarctic ice sheet stability.

J. T. M. Lenaerts, J. Brown, M. R. van den Broeke, K. Matsuoka, R. Drews, D. Callens, M. Philippe, I. V. Gorodetskaya, E. van Meijgaard, C. H. Reijmer, F. Pattyn, N. P. M. van Lipzig: High variability of climate and surface mass balance induced by Antarctic ice rises. J. Glaciol., 60, 224, doi: 10.3189/2014JoG14J040

For contact please e-mail: Jan Lenaerts