Multivariate objective analysis of the coastal circulation of Barbados, West Indies: implication for larval transport

A multivariate spatial objective analysis (MVOA) assimilating high
spatio-temporal resolution of hydrographic (CTD) and acoustic (ADCP)
observations near Barbados provided a comprehensive view of the local surface
circulation (0-100 m) during early spring of two consecutive years (1996 and
1997). Significant submesoscale fluctuations of the velocity and salinity
fields exhibit a very dynamic environment. In the middle of each cruise,
low-salinity water originating from the Amazon and entrained by a North Brazil
Current Ring (NBCR) intruded from offshore and persisted on the west coast of
Barbados throughout the rest of the survey. Principal component analysis
(PCA) of velocity relative to the vertical structure and temporal factors in
the study area demonstrated that the local circulation was mostly baroclinic
and was dominated by a strong salinity front impinging on the island and
large amplitude current reversals with a periodicity of ca. 20d. During
transition times, indicated by a change of the sign of the amplitude of the
empirical orthogonal function (EOF), the flow became barotropic. This situation
produced strong southward currents followed by the onset of vertical velocity
shear. Most of the flow variability occurred in the upper 40 m of the water
column, which was also found to be the depth of penetration of the
low-salinity lenses. These results indicate that the NBCR structure was
retained during both intrusions. Langrangian trajectories using the MVOA
currents were found to be consistent with in situ drifter trajectories,
suggesting that the analyzed flow field is representative of the near-shore
circulation. Tracking of particles released in the surface layer (0-20 m)
from the reef shows a maximum residence time of 18 d indicating the possibility
of larval retention within the island-scale flow field. Finally, our results
suggest that MVOA, within its limitations, is a powerful tool that can be
applied elsewhere to infer circulation and larval transport, even in situations
when forcing is unknown. "To accurately define and predict larval transport,"
examine larval retention vs. dispersal, and to "... quantify the time/space
scales of the complex coastal current features that promote retention or
dispersal."

Spatial Data Organization Information - Indirect Spatial Reference: Barbados,
West Indies Direct Spatial Reference: Vector

Spatial Reference Information - Horizontal Coordinate System Definition -
Geodetic Model: