  Coherent filaments at the ocean surface often appear to be transient
watermass boundaries, where currents converge, surfactants accumulate, and
frontal structure at depth can possibly delineate enhanced biological activity
in the upper water column. Spaceborne synthetic aperture radar (SAR) permits
filaments to be observed at O[1-km] resolution, but extensive coherent
structures are more apparent in weaker winds. A wind speed adjustment is
proposed for filaments (i.e., contiguous SAR contrasts) of at least 10 km in
length. Measures of dependence (distance correlation and the linear and
nonlinear components of Pearson correlation) are examined to identify a broad
peak in the relationship between filament contrast and weak or moderate values
of surface wind speed, where a variable wind speed exponent is employed to
maximize these measures.
  Three locations of recent North Atlantic right whale (Eubalaena glacialis)
sightings in the Gulf of St. Lawrence are sampled between 2008 and 2020 by 324
Radarsat-2 SAR scenes and 10-m wind speed from the ERA5 reanalysis. The inverse
relationship between SAR contrast magnitude and wind speed is quantified, and a
reduced correlation is obtained for all three domains when SAR contrast is
weighted by wind speed to the power of 0.8. A more uniform emphasis on ocean
surface structure within a SAR scene, or across multiple scenes, can thus be
considered in the search for prey aggregations of the North Atlantic right
whale.

Applications;Methodology