PDFFirst Paragraph
Before 2004, little was known about deep ocean circulation in the Lau Basin, a semi-enclosed basin in the South Pacific Ocean, about 1,500 km north of New Zealand. This basin hosts a number of back-arc spreading centers with active hydrothermal vents, including the Eastern Lau Spreading Center (ELSC), a Ridge 2000 Integrated Study Site where coordinated interdisciplinary experiments were carried out between 2004 and 2010 (Tivey et al., 2012, in this issue). Answering numerous important questions in hydrothermal research requires an understanding of oceanic circulation on a range of temporal and spatial scales. For example, we need to be able to make flux calculations of heat and hydrothermal chemicals and to know the pathways for larval dispersal, which determine colonization of new hydrothermal sites, gene flow, and ultimately the biogeography of vent species. Knowledge of turbulent dispersion (mean squared displacement averaged over groups of floats) enables quantification of spreading rates and direction in complex ocean circulation regimes, and Lagrangian measurement techniques are often used to observe dispersion. Near mid-ocean ridges, however, this approach is still relatively rare (Speer et al., 2003; Jackson et al., 2010).