Shown are forward flowmaps in the Gulf region during the period May 16-31, 2025, with a focus on two cyclonic Loop Current (LC) Frontal Eddies (FE). We first compute the 3D forward flowmaps for different time windows (0, 3, 6, 9, 12, and 15 days) for the whole Gulf domain. Forward flowmaps link the initial location of a water parcel to its final position as it is advected over a specified time window.
We identify the locations (region in space) where the two cyclonic LCFEs are. We define these initial LCFE locations based on watermass analyses (T, S, σT) at several depths, velocity and vorticity at several depths, and Lagrangian feature analysis (coherent structures, FTLE, etc.). Once these initial locations are defined, we then select these locations of the forward flowmaps at initial time and draw a curve on the edge of the LCFE at each depth plotted (see the white curves in the plots in the first column, labeled in white text). We then color their final positions at the different intermediate times of the forward flow map (see the red and blue regions in the plots in the other columns). This basically highlights where eddies 1 (blue) and 2 (red) are going over time.
Material starting in eddy 1 is advected northeast along the LC but remains entrained in the same eddy, which has moved to the northern flank of the LC. At shallow depths, the material first becomes distorted, then reshapes into an eddy structure. At 1000m depth, most material remains near its starting location. Material starting in eddy 2 is stretched (advected) southward with the LC and, and moves along with the eddy, though some material at shallower depths is advected out through the Florida Strait.
Overall, the cyclonic LCFEs become tilted due to advection differential in the vertical. The cyclonic LCFEs shed filaments as they rotate, advect with entrainment, and lead to spiraling of water masses as they erode in turbulent shear. In some cases, part of the surface LCFE waters may detach from their deeper waters.
| Depth (m) | Starting regions | Initial position | May 16 to May 19 | May 16 to May 22 | May 16 to May 25 | May 16 to May 28 | May 16 to May 31 |
|---|---|---|---|---|---|---|---|
| 300 |
|
|
|
|
|
|
|
| 500 |
|
|
|
|
|
|
|
| 1000 |
|
|
|
|
|
|
|