Formation of North Atlantic Deep Water (NADW) is an important component of the ocean thermohaline circulation but debate exists over the ocean circulation state during glacial stages. Some geological and modelling studies suggest decreased NADW and increased formation of Southern Ocean deep water during the Last Glacial Maximum (LGM); others indicate similar, or higher, rates of NADW advection. Here, we test three very different potential LGM ocean states by comparing the modelled iceberg trajectories each produces with magnetically-mapped patterns and sources of LGM ice-rafted debris (IRD). The three LGM states are characterised by: vigorous NADW formation; deep water production in the Southern Ocean; and a third, â��intermediateâ�� state, with Southern Ocean deep water formation but also some N. Atlantic intermediate water formation. Cluster analysis of diagnostic magnetic parameters was used to characterise N. Atlantic IRD patterns and sources, which match most closely iceberg trajectories arising from some combination of the â��southern-sinkingâ�� and â��intermediateâ�� ocean circulation states.