| Summary: | The contribution to sea level to 2200 from the grounded, mainland Antarctic Peninsula ice sheet (APIS) was calculated using an ice-sheet model initialized with a new technique computing ice fluxes based on observed surface velocities, altimetry and surface mass balance, and computing volume response using a linearized method. Volume change estimates of the APIS resulting from surface massbalance anomalies calculated by the regional model RACMO2, forced by A1B and E1 scenarios of the global models ECHAM5 and HadCM3, predicted net negative sea-level contributions between –0.5 and –12mm sea-level equivalent (SLE) by 2200. Increased glacier flow due to ice thickening returned 15% of the increased accumulation to the sea by 2100 and 30% by 2200. The likely change in volume of the APIS by 2200 in response to imposed 10 and 20km retreats of the grounding line at individual large outlet glaciers in Palmer Land, southern Antarctic Peninsula, ranged between 0.5 and 3.5mm SLE per drainage basin. Ensemble calculations of APIS volume change resulting from imposed grounding-line retreat due to ice-shelf break-up scenarios applied to all 20 of the largest drainage basins in Palmer Land (covering 40% of the total area of APIS) resulted in net sea-level contributions of 7–16mm SLE by 2100, and 10–25mm SLE by 2200. Inclusion of basins in the northern peninsula and realistic simulation of grounding-line movement for AP outlet glaciers will improve future projections.
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