Variability of the lower circumpolar deep water in Drake Passage 1926-2004

Lower Circumpolar Deep Water (LCDW) is an important component of the global overturning circulation as it upwells south of the Antarctic Circumpolar Current (ACC) renewing the ocean interior. The LCDW also aids the transport of water properties between the major ocean basins. The property variability of the LCDW Salinity Maximum layer was examined using 37 meridional sections across Drake Passage between 1926–2004. Within the limits of experimental error and high frequency variability, the core properties of this layer have remained constant between 1926–2004. A comparison of modern sections and the 1932 Discovery II cruise indicates that this observation may be true for LCDW throughout the Southern Ocean. The significance of this result in terms of the observations of decadal changes in the Southern Ocean Intermediate and Mode waters is that these changes are most likely due to contemporary atmospheric forcing and not due to variations in the source water properties.