The Innuitian Ice Sheet: configuration, dynamics and chronology

Portrayal of North American ice cover during the Last Glacial Maximum is dominated by the Laurentide Ice Sheet, leaving little detail for the adjacent Innuitian Ice Sheet (IIS). Four decades of geological fieldwork across the Queen Elizabeth Islands now warrant specific treatment of the IIS, including its chronology, configuration, dynamics and retreat. This reconstruction is relevant to the sedimentary history of the Arctic Ocean and to high latitude climate forcing. The IIS was composed of both an alpine and lowland sector. The advance of the alpine sector occurred as recently as 19 14C ka BP. Geological evidence configures outflow from alpine and lowland divides that produced several palaeo-ice streams, one extending northwestward across the Canadian Arctic Archipelago to the polar continental shelf. Retreat of the IIS commenced along its southwest margin ∼11.6 14C ka BP. However, most of the ice sheet remained on the continental shelf during the Younger Dryas. By ∼10 14C ka BP, marine-based ice experienced widespread calving through the western and central archipelago in response to Holocene warming and ongoing eustatic sea level rise. The sea penetrated the eastern archipelago by 8.5 14C ka BP, gutting the alpine sector of the IIS. Regional isobases record the glacioisostatic signature of the ice sheet, and are congruent with the primary geological evidence. The delayed buildup of the IIS was out-of-phase with the growth of the Laurentide Ice Sheet that occasioned climatic and glacio-eustatic forcing in the Innuitian region. Recent modelling experiments reinforce the hypothesis that growth of the Laurentide Ice Sheet culminated in a split jet stream that temporarily favoured augmented precipitation and growth of the IIS.