Award: OCE-1153693

One of the longest open-ocean hydrographic stations in the world is maintained at the Hydrostation S site (formerly known as the Panulirus site) located ~25 km southeast of Bermuda in the North Atlantic Ocean. This program of repeat biweekly hydrographic observations was initiated by Stommel and co–workers began in 1954 and now, in its seventh decade, has proved to be the catalyst for numerous studies of ocean physics, biological processes and biogeochemistry. Hydrostation S continues to be recognized as one of the most important sustained ocean time–series. The renewal of the Hydrostation S program from this award has extended this invaluable time–series of ocean hydrography to almost 65 years. The upper ocean warming trend has strengthened (about 0.8° C since the 1970's) while the deep Labrador Sea has cooled by a few tenths of a degree. Over the past 65 years, this warming is equivalent to an increase in upper ocean heat content of ~1 W m-2. The signature of deoxygenation (i.e. loss of dissolved oxygen) has been observed at Hydrostation S in the upper ocean (about 7 μmoles/kg/decade decrease in dissolved oxygen) as well as the oxygen minimum zone. This is strongest evidence for deoxygenation in the North Atlantic Ocean at present. These findings indicate that while ocean warming has likely contributed to overall deoxygenation, through increased solubility effects, of the North Atlantic subtropical gyre, contemporaneous increases in biological productivity, as shown by higher rates of AOU change, have partially offset such changes in dissolved oxygen. In the contemporary narrative of examination of global environmental changes such as ocean deoxygenation, long-term ocean time-series illustrate the importance of other factors such as ocean productivity that may mitigate over multi-decadal timescales. Last Modified: 06/30/2017 Submitted by: Nicholas R Bates