Centurial-millenial ice-rafted debris pulses from ablating marine ice sheets



We use an ice-sheet model to show that (i) margins of marine ice-sheets can be expected to be frozen to the bed, except where ice-streams discharge; (ii) 20–50km retreats induced by ablation rates of 2 m/yr provide sufficient debris flux through the grounding line to produce large sedimentation events. Such ablation would reduce ice-shelf extent markedly, permitting debris to reach the calving front and be transported by icebergs leading to ice-rafted debris (IRD) events. Ice shelf break-up takes around a century (start of IRD pulse), while the creation of warm-based conditions (end of IRD pulse) due to upwards motion of warm ice takes a few more centuries. Such IRD pulses are unlikely to explain Heinrich events, which are associated with relatively cold periods within glaciations. Surges are not necessary conditions for the production of large IRD events.