Introduction . The Labrador Sea is the coldest (Fig.? 1 ) and freshest deep subpolar North Atlantic (SPNA) basin1where intense vertical mixing driven by high winter surface heat losses (WSHL) produces Labrador Sea Water (LSW)—a major North Atlantic intermediate-depth water mass2 , 3 , 4 , 5 , 6 , 7 , 8. Cold fresh dense oxygen-rich LSW spreads across the ocean renewing and ventilating its intermediate and deeper layers9 , 10 , 11 , 12 , 13 , 14 , ...