Abstract
We construct a climatology of Lagrangian coherent structures (LCSs), the
concealed skeleton that shapes transport, with a twelve-year-long
data-assimilative simulation of the sea-surface circulation in the Gulf of
Mexico (GoM). Computed as time-mean Cauchy-Green strain tensorlines of the
climatological velocity, the climatological LCSs (cLCSs) unveil recurrent
Lagrangian circulation patterns. cLCSs strongly constrain the ensemble-mean
Lagrangian circulation of the instantaneous model velocity, thus we show that a
climatological velocity may preserve meaningful transport information. Also,
the climatological transport patterns we report agree well with GoM kinematics
and dynamics, as described in several previous observational and numerical
studies. For example, cLCSs identify regions of persistent isolation, and
suggest that coastal regions previously identified as high-risk for pollution
impact, are regions of maximal attraction. Also, we show examples where cLCSs
are remarkably similar to transport patterns observed during the Deepwater
Horizon and Ixtoc oil spills, and during the Grand LAgrangian Deployment (GLAD)
experiment. Thus, it is shown that cLCSs are an efficient way of synthesizing
vast amounts of Lagrangian information. The cLCS method confirms previous GoM
studies, and contributes to our understanding by revealing the persistent
nature of the dynamics and kinematics treated therein.
