Cn. Flagg et al., SUMMERTIME THERMOCLINE SALINITY MAXIMUM INTRUSIONS IN THE MID-ATLANTIC BIGHT, Deep-sea research. Part 2. Topical studies in oceanography, 41(2-3), 1994, pp. 325
Mooring data with high vertical resolution have been combined with hyd
rographic data to investigate the character of high salinity thermocli
ne intrusions in the shelf water-slope water frontal zone in the south
ern Mid-Atlantic Bight. The coincidence of current, temperature and sa
linity data has allowed a detailed investigation of how the intrusion
process is initiated. The data show that the time scale for both the o
nset and duration of the intrusions is very short. Most intrusions at
a single location seem to last no more than a day, while the onshore f
low associated with many, but not all, intrusions accelerates very qui
ckly attaining amplitudes of 10-20 cm s(-1). As has been noted in earl
ier studies, there is a correlation between the intrusions and upwelli
ng favorable winds, but the magnitude of the wind stress is not suffic
ient to account for the onshore transport of the intrusions. The combi
nation of current measurements with density profiles has allowed the c
alculation of gradient Richardson numbers associated with the intrusio
ns. These calculations show that during the strong onshore flow period
s there is significant mixing at the boundaries of the intrusions. At
other times when the high salinity water is being passively advected a
long the shelf, there appears to be little shear turbulence at the int
rusion boundaries. Continuous data coverage during the summer suggests
that the intrusion process is actually fairly infrequent, apparently
requiring an offshore preconditioning in which high salinity waters of
the correct density are located just offshore in addition to upwellin
g favorable winds.