Experimental investigation of ice-covered deltas : the effects of ice cover on delta morphology

Deltas are dynamic systems that can provide important information on past climate conditions (Helland-Hansen and Martinsen, 1996; Hill et al., 2001; Kim et al., 2006; Bianchi and Allison, 2009). Arctic deltas have the potential to preserve significant information about climate change in one of the most temperature-sensitive regions of the Earth (Walker 1998; Walker and Hudson, 2003; Bianchi and Allison, 2009; Stocker, 2014). Here we present experimental results assessing the effects of ice cover on delta morphodynamics and depositional processes to identify signatures of ice cover presence during deposition. Ice cover drives spatially varying sediment transport on the subaqueous delta clinoform through sub-ice channels, which then leads to the development of (1) multiple extended delta lobes built by elongated, subaqueous sediment wedges and (2) highly variable bathymetry with increasing topographic roughness up to a water depth above which bottom-fast ice cover exists. These seascape features are unique to ice-covered deltas, and can therefore serve as diagnostic markers of past climate conditions and indicators of climate change captured on vulnerable Arctic coasts.