Moored Array

GAGE, the Guiana Abyssal Gyre Experiment, was conceived, designed and proposed as a combined current meter mooring array (6 moorings and 47 current meters – stars on the figure to the right) and hydrographic survey in the Guiana Basin, with a two-year field phase involving a single array setting with supportive hydrography during array deployment and recovery, all directed towards the Guiana Abyssal Gyre hypothesis. The design emphasized the interior circulation while including enough measurements in the Deep Western Boundary Current (DWBC) to establish its amplitude.

We learned during our proposal review cycle that German colleagues were funded to do a CLIVAR pilot experiment, the Meridional Overturning Variability Experiment (MOVE, based at Kiel). MOVE was designed to measure Meridional Overturning Circulation cold limb transport variability using a sparse array of three tall “dynamic height” moorings, each mooring having multiple fixed point CTDs with adjacent PIES (inverted echo sounders with bottom pressure gauges). The dynamic height measurements and bottom pressures were intended to provide horizontally-integrated baroclinic transport indices for the net cold limb flow and for the two limbs of the Guiana Abyssal Gyre. To estimate the contribution to fluctuations from the part of the DWBC west of the westernmost tall mooring, a fourth mooring with 4 current meters (circles on the figure to the right) was to be placed at the 3000 m isobath of the continental slope. 

This provided a splendid collaborative opportunity, and we redesigned a joint GAGE/MOVE array of 10 moorings. With great largesse our German colleagues enhanced their planned dynamic height moorings with 21 current meters beyond the 4 they had planned for the continental slope mooring. This joint design much strengthened the resolution of the structure and intensity of the abyssal gyre limbs and the DWBC. The combined GAGE/MOVE array contained a total of 72 current meters equipped with temperature sensors, with the three tall German Moorings additionally having 48 MicroCAT CTDs.