Many studies have considered that large scale meridional circulation may be sensitive to freshwater input, whether from changes in river runoff, to outflow from the Arctic Ocean, to melt from glaciers and ice caps. Here we consider some of these issues from a physical oceanography perspective, looking at sources of freshwater to the sub-polar North Atlantic Ocean as well as potential impacts, including processes whereby freshwater is exchanged from coastal boundary currents to the interior of gyres where deep convection occurs. A series of historical sections across the West Greenland Current from the 1960’s to present will be examined and discussed. Also, output from high resolution numerical ocean general circulation models will be presented, including a series of global hindcasts covering 1958 to 2004, as well as regional simulations.