The strong anticyclone gyre has tracked mostly west and slightly south and appears to be headed for an intersection with BATS with the eddy’s center about 20 km south of BATS. Jack’s track for the past week or so has allowed it to circle the eddy and the glider is now on a northerly track through the eddy center. Profiles of T, S, and O2 are beginning to show the elevated values that are typical of a Gulf of Cadiz eddy (see the 9 April 2017 update).

An anticyclonic eddy is approaching BATS from the east that contains water properties characteristic of the Gulf of Cadiz. Jack has explored the eddy properties in the last week and discovered unusually high temperatures, salinities and dissolved oxygen concentrations in the lower parts of the thermocline. In the last several weeks, O2 concentrations at about 900 m have varied dramatically from low values of about 120 mmoles kg-1 to high values of 220 mmoles kg-1.

Anna and Minnie were deployed from RV Atlantic Explorer on February 20, 2017 – Anna at Hydrostation S and Minnie at BATS. Anna is quipped with a standard set of sensors: CTD, optical fluorescence, backscatter and CDOM, and dissolved oxygen; Minnie is similarly equipped with the addition of a nitrate sensor. Both gliders are holding station and making about 8 dives each day. Jack was recovered February 27, had its battery replaced and redeployed on March 13, with standard sensors plus an Acoustic Doppler Current Profiler (ADCP).

“Jack” has been profiling the water column at Hydrostation S since early January.   From February to June 2017, all three gliders will be used to conduct intensive sampling as part of continued efforts to understand plankton production and the “Spring Bloom” in the Sargasso Sea.

All three gliders are presently in the water measuring water column conditions and chronicling inventories of chlorophyll, dissolved oxygen and nitrate. Principal objectives of this summer mission are to gain experience with the SUNA nitrate sensor and acoustic Doppler profiler (ADP), to continue high-resolution time series profiling records near the BATS site, and to simultaneously measure conditions about 60 km to the northeast as a strong cyclonic eddy approaches. As of July 31, the center of the cyclone is still >100 km from Jack and Minnie.