Twenty-first-century warming of a large Antarctic ice-shelf cavity by a redirected coastal current
The Antarctic ice sheet loses mass at its fringes bordering the Southern Ocean. At this boundary, warm circumpolar water can override the continental slope front, reaching the grounding line1,2 through submarine glacial troughs and causing high rates of melting at the deep ice-shelf bases3,4. The interplay between ocean currents and continental bathymetry is therefore likely to influence
future rates of ice-mass loss. Here we show that a redirection of the coastal current into the Filchner Trough and underneath the
Filchner–Ronne Ice Shelf during the second half of the twenty-first
century would lead to increased movement of warm waters into the
deep southern ice-shelf cavity. Water temperatures in the cavity
would increase by more than 2 degrees Celsius and boost average
basal melting from 0.2 metres, or 82 billion tonnes, per year to
almost 4 metres, or 1,600 billion tonnes, per year. Our results,
which are based on the output of a coupled ice–ocean model forced
by a range of atmospheric outputs from the HadCM35 climate
model, suggest that the changes would be caused primarily by an
increase in ocean surface stress in the southeastern Weddell Sea
due to thinning of the formerly consolidated sea-ice cover. The
projected ice loss at the base of the Filchner–Ronne Ice Shelf represents
80 per cent of the present Antarctic surface mass balance6.
Thus, the quantification of basal mass loss under changing climate
conditions is important for projections regarding the dynamics of
Antarctic ice streams and ice shelves, and global sea level rise.
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