North Atlantic Subtropical Mode Water: A history of ocean-atmosphere interaction 1961-2000

Water masses that ventilate intermediate ocean depth, such as the North Atlantic Subtropical Mode Water (NASTMW), play important roles in various aspects of climate, but their basic properties and space-time variability need to be better quantified. Herein we examine the mean annual cycle and long-term variability of NASTMW for the 40-year period 1961-2000. Integrated NASTMW properties such as water mass volume, temperature, and heat content show a consistent annual cycle superimposed over a much larger interannual-to-decadal cycle that is strongly correlated to the North Atlantic Oscillation index. The 40-year record clearly shows the ocean's ability to integrate atmospheric forcing over several years and to exhibit an interannual memory of wintertime forcing by the atmosphere.