Award: OCE-1332667

The Line W research program was conceived to observe and characterize the time-averaged structure and intensity of the Deep Western Boundary Current (DWBC) and Gulf Stream, and to investigate the nature and causes of their variability. These two oppositely-directed flows: the Gulf Stream carrying warm water northwards and the DWBC transporting cold water equatorward, are major contributors to the so-called Atlantic Meridional Overturning Circulation. A long-term community research goal is to develop better understanding of the role of these time-varying circulations in earth?s climate system. The Line W study's approach centered around a sustained observational program that spanned the continental slope on a line running approximately from Woods Hole towards Bermuda. The field program, that employed moored instruments, repeated ship-based sampling and analyses of remote sensing data, produced a 10-year-long time series of boundary current data that were (and continue to be be) used together with companion programs at other latitudes in the Atlantic to characterize the Meridional Overturning Circulation in the North Atlantic Ocean. The field program ended in May 2014; the present grant supported the processing of the final set of recovered data and continued scientific analysis of the full 10 years of observations. Highlights of the latter (reported in peer-reviewed journal articles) include quantifying the time averaged fluxes of water carried by the Gulf Stream and DWBC and a suggestion that these flows weakened by approximately 30% over the measurement period. It is not known at this time if this finding reflects a decadal timescale oscillation that was not fully resolved by the 10-year observational program or manifests a sustained climate change. In addition to the scientific research, the entire Line W program supported three (female) graduate students through to successful doctoral dissertation defenses, hosted many 10s of students and junior support staff on research cruises to gain sea going experience, and provided a testbed for several oceanographic sensors and measurement systems. Last Modified: 03/20/2020 Submitted by: John M Toole