Abstract
The present work investigates the relationships between the Loop Current Frontal Eddies (LCFEs) and Loop Current Eddy (LCE) detachment using model simulations and observations. A first goal is to understand how uncertainties in the initial conditions of a forecast, particularly those pertaining to the location and strengths of the LCFEs, impact the detachment forecast. A second goal is to investigate whether observational altimetric data of LCFE properties can be used as predictors of LCE detachment probability.
In the first part, the dynamics of the LC system prior to Eddy Franklin detachment in 2010 are investigated using an ensemble of simulations that perturb the strength and size of a West Florida Shelf Cyclonic Eddy (WFCE). Ensemble members with stronger and larger WFCE in their initial conditions lead to an early detachment of the Loop Current while members with weaker and smaller WFCE lead to a late or no detachment during the sixty days of the simulation period. The size and strength of the initial WFCE are also found to impact the evolution of Campeche Bank Cyclonic Eddies (CBCE). When a large and strong WFCE intrudes into the LC, potential vorticity (PV) over the eastern Campeche Bank (CB) grows fast and a CBCE is prone to form. Ensemble members with stronger and larger WFCE agree with mooring data very well on the velocity evolution over the eastern CB and CBCE northeastwards offshore displacement.
In the second part, we collect information on WFCEs' size and strength, from 12 LCE detachment events and 5 non-detachment events in altimetry observations. Logistic regression models to predict LCE detachment probability are built based on the size and the strength of the WFCE, respectively. The WFCE strength proves to be a better predictor than the WFCE size, because of lower prediction error and less sensitivity to the selection of events for training and testing. An analysis of the predictability of LC detachments using WFCE strength as a predictor reveals that the model performs best 29 days before LCE detachment.