The impact of paleoatmospheric forcing and sea ice distribution on the circulation of the subpolar North Atlantic is examined in a regional eddy-permitting ocean model. We focus on water mass formation and the pathway of the North Atlantic Current. Paleofluxes are obtained from a coupled atmospheric general circulation model, while the seasonal sea ice cover is based on a pair of Last Glacial Maximum sea ice reconstructions. Labrador Sea Water formation, the pathway of the North Atlantic Current, and the strength of the Atlantic Meridional Overturning Circulation are found to be dependent on the structure of the sea ice representation. Here, the key role played by the sea ice is its isolation of the underlying ocean from the wintertime atmospheric fluxes. The results highlight the need for accurate seasonal sea ice fields for validating paleomodeling simulations.