Observing the Anomalous Plume of Labrador Sea Water Within the North Atlantic's Deep Western Boundary Current at 16 degrees N


OCCI Project Funded: 2001

Proposed Research

The meridional overturning circulation (MOC) of the North Atlantic Ocean is a major player in the redistribution of heat and fresh water by the world's ocean. The Atlantic's MOC is dominated by the transformation of northward flowing warm water into southward flowing cold water, a process that liberates considerable heat to the overlying atmosphere. The cold water limb, in turn, is dominated by two distinct water masses: Nordic Seas Outflow water at deep levels, and Labrador Sea Water (LSW) at intermediate depths. The properties of these two water masses have been demonstrated with modern instrumental data to have interannual/ interdecadal variability. On longer time scales, paleo-oceanographic data suggest even larger amplitude fluctuations of conditions in the formation areas and in the cold limb of the MOC. The key to linking such fluctuations to climate change dynamics, including so-called "abrupt" climate change, may lie in determining the changes in circulation intensity and structure that accompany the water mass formation fluctuations. In the most recent two decades, LSW formation underwent a large change in character, manifested by a prominent cooling and freshening of the LSW core. This anomalous LSW has spread through the subpolar gyre and invaded the subtropical gyre. In January 2000, the anomalous LSW was detected ubiquitously in the deep western boundary current east of the Leeward and Windward Islands of the Caribbean—its first detection within the tropical circulation regime. This proposal takes advantage of an existing mooring adjacent to Guadeloupe (~16 degrees N), scheduled to be reset in January 2002, to measure the growing LSW water mass anomaly and, simultaneously, the character of its associated circulation anomaly.