Fig. 4: CCFZ sediment ambient plume tracking.

a The dynamic plume was released over 45 min at the location marked by the blue cross producing an ambient plume. The grey line represents the ship track during the tow-yo sampling. The dots on top of the ship track are the start locations of the tow-yo downcasts with (red) and without (blue) ambient plume detections. The open circles (blue and red) correspond to ship position (and ambient plume observations) at the indicated time in minutes from the start of the plume release. The red circles indicate where water samples were taken for the results presented in Fig. 6b–d. The numbers 0–17 in green indicate the start of the R/V transects (i.e., transect 0 starts at label 0 and goes to label 1) and correspond to the numbers indicated on top of Fig. 5a, b. b The ambient plume location estimated using the ADCP advection model (hatched patches) and forecast by the MIT-MSEAS model (shaded patches) 78 (blue), 120 (grey), 250 (green), and 371 (red) minutes after the start of the plume release (see “MIT-MSEAS numerical model” section). The brown line next to the release location corresponds to the initial centerline (streakline) of the ambient plume, obtained with the ADCP advection model. The width of the ADCP advection model plume is based on the initial tow-yo observations (~120 m), plus the consideration of a lateral effective diffusivity of 0.1 m² s⁻¹ (since the ADCP advection model can only estimate the location of the ambient plume’s centerline).