On the basis of hydrographic data collected by the Texas-Louisiana She
lf Circulation and Transport Processes Study (LATEX A) and on earlier
cruises, we examined the energetic scales of spatial variability over
the Texas-Louisiana continental shelf. Shelf-scale spatial reference f
ields were sought to represent the general distributions of circulatio
n and water properties over the shelf at the time of the observations.
Various methods were explored for determining such reference fields o
f potential temperature, salinity, and geopotential anomaly at the sea
surface relative to 70 dB. Spatial reference fields obtained from mea
n May fields and from polynomials fitted to individual May cruise data
were compared. On the basis of those comparisons, quadratics were sel
ected to fit property distributions from individual cruises and so to
yield reference fields. Smaller-scale anomaly fields were obtained by
removing the reference fields from the observed distributions. Calcula
tion of correlation versus separation distance based on these anomaly
fields then allowed estimation of spatial scales of anomaly fields for
cross-shelf and along-shelf transects. The zero-crossing scale and th
e Gaussian decay scale are shown to be essentially the same, and the z
ero-crossing scale is used. The principal results for the anomaly scal
es are (1) cross-shelf scales over the western shelf are shorter (orde
r 15 km) than those in the eastern and central regions (order 20 km),
(2) along-shelf spatial scales are of the order of 35 km, (3) there is
no significant difference in cross-shelf scales at the surface, midde
pth, and bottom, and (4) along-shelf scales are essentially the same o
ver the western and eastern regions of the shelf, over the midshelf (5
0-m isobath) and along the shelf break (200-m isobath), and at differe
nt depths along the 200-m isobath. The same spatial scales are found w
hen using data with spatial resolution of 1-10 km cross shelf and 10-2
0 along shelf to obtain the anomaly fields, so the data resolution use
d is adequate to represent the scales. The variances of the observed (
shelf-wide) salinity, temperature, and geopotential anomaly are greate
r cross shelf than along shelf. The variance of the cross-shelf anomal
y fields is around 10% of the shelf-wide fields; that of the along-she
lf anomaly fields is about 35% of that in the shelf-wide fields, The a
nalysis of scales when grouped by season did not show persuasive evide
nce of seasonal variation.