Calving of icebergs is the dominant ablation mechanism for large outlet glaciers from the Greenland ice sheet except in northernmost Greenland where bottom melting from floating glaciers dominates. This difference is controlled by present climate conditions. Glacial geological evidence indicates that the transition between the associated types of fjord-glaciations moved north-south in response to past climate change. In cold periods, local melt-out of debris from the bottom of an increasing number of floating glaciers reduces the potential for iceberg transport of IRD. Thus, the marine IRD signal of Greenland origin is not a simple cold climate signal. Our findings are discussed in the context of the ongoing debate about the kind of ice transporting IRD - icebergs or sea ice.