Hydrostation 'S' located some 25 km south east of Bermuda in the Sargasso Sea represents the site of the longest maintained oceanographic hydrography timeseries. Initiated by oceanographer Henry Stommel and co-workers in 1954, this invaluable biweekly timeseries has been in existence for nearly 58 years. Historically, the Hydrostation 'S' program through its core hydrography measurements and other ancillary work has facilitated a diversified measurement program. The dominant theme of these studies has been long term change relating to climate issues using the unprecedented near six decades of physical hydrography. These data clearly show substantial inter-annual and decadal variability throughout the full water column although significant long term trends exist in the thermohaline properties of both the upper ocean and deep waters. For waters consistent with subtropical mode water at this site (~300 m depth), the long term trend in temperature and salinity is + 0.009 C per year and 0.002 salinity units per year, respectively, while for deeper waters consistent with Labrador Sea Water , the observed trends are -0.005 C per year and -0.001 salinity units per year . Interestingly, for the past five years, the observed trends for these water masses are opposite to the long term trends. Hydrostation 'S' data have been an important resource in helping understand variability in the various water masses of the subtropical gyre by establishing links to climate state (North Atlantic Oscillation) and large scale mass transport (Atlantic Meridional Overturning Circulation). As a result of collaboration with other investigators, the Hydrostation 'S' program continues to deliver a broad research list and complementary to the core hydrography, these ancillary projects have yielded the longest time-series of carbon dioxide (now 29 years old), tritium and helium and trace organics.
Perhaps one of the more important aspects of this timeseries is the support framework and multi-decadal synthesis context it provides for other oceanographic programs in this region. These data are considered as a service to the community as a whole being openly distributed and subsequently an invaluable resource for understanding ocean processes. All data for this current award have been processed and data through December 2010 are available for full access while data through July 2011 can be accessed as preliminary data. This renewal will maintain the same sampling program of near biweekly sampling consisting of deep CTD casts and discrete samples for salinity and dissolved oxygen.
Broader Impacts: Hydrostation 'S' cruises have played a large role in education at BIOS by providing students one day trips to the Sargasso Sea such that these cruises now routinely host large student groups (e.g., Princeton University graduates). Hydrostation 'S' cruises have also proved to be a key platform for resident undergraduate, graduate and local high school students, for gaining experience and conducting independent research projects. Due to their short duration, Hydrostation 'S' cruises continue to prove useful for both local and international media reporters. During this past year media teams from Time Magazine, National Geographic and NBC News have participated on Hydrostation 'S' cruises resulting in articles and documentaries highlighting this time-series and its role in helping understand ocean variability and climate change. In the past few years, there has been a large increase in educational and outreach activities on these cruises primarily due to the arrival of the R/V Atlantic Explorer at BIOS.
