ws) 
ee ee Ce Sa 1000 
sees egestas, : sl, a at hoes ca ee 
F * : fee, : . mae 200 
a “es eS 3 
0 : 
fe} 
o~ 
> 
ae 
£ 
w lO 
O.W.S. Bravo depth (m) 
34 
IS64 IS66 1968 1970 Ie 
Fig. 4. Salinity on various levels as measured at OWS Bravo (after Lazier, 1980). 
These three scales of organization (cyclonic gyre, mesoscale and eddy scale) seen in the 
Labrador Sea were also observed during Mediterranean Water formation in the Western 
Mediterranean. There, convection extends to the bottom and both the mesoscale and eddy scale 
circulations were cyclonic rather than anti-cyclonic. In the Mediterranean Sea, the structures 
break up quickly (over a few days) once the strong forcing is turned off and once convection 
has reached the bottom. In the Labrador Sea, the eddy scale features showed no sign of 
breaking up over the period we were studying them, even though the strong forcing was turned 
off. Work on "meddies", lenses of anomalous water in the ocean at depth, would suggest that 
the Labrador Sea Water eddies would be long-lived (several years) provided they were not 
destroyed through contact with the bottom or by strong shears. 
It is also interesting that in the winter of 1978, which was dominated by SE winds rather 
than NW winds, there was no deep convection. The cyclonic gyre did form; however, there was 
weak evidence of mesoscale and eddy scale features. This might suggest that the convection is 
a component of the generation mechanisms for these features. 
What can be done from space to monitor these processes? Surface temperature differences 
within such an area are on the order of 0.1 °C and thus are unlikely to be measurable. Satellite 
tracked T and S chains are a possibility. Surface buoys do remain in the region for periods of 
months; the difficulty is the accuracy of the temperature and salinity measurements which would 
have to be maintained at a variety of levels down to 2.5 km. These accuracies need to be 0.01 
°C and 10 ppm in salinity. The mesoscale features may be detectable from surface velocity 
measurements. 
Water types had usually been thought of as invariant by oceanographers. Oceanographic 
surveys in the 1960's in the Western North Atlantic identified Labrador Sea Water as being 3.4°C, 
34.9°/oo (Lazier, 1973). In 1976, we observed Labrador Sea Water being formed at the same 
density but at 2.9°C and 34.84°/oo. One sees that there has been a considerable range of T and 
S; however, LSW always appears as a salinity minimum at o, = 27.78. This density restraint is 
applied by the presence of the higher salinity North Atlantic Deep Water beneath the LSW. For 
example, to increase the density of a 2 km column of LSW by 0.01 Kg/m3 would require the heat 
and fresh water loss equivalent to evaporating 40 cm of water from the sea surface. This would 
require strong cooling conditions to continue for another month. Since formation of LSW itself 
only occurs during intense winters, such an occurrence would be an exceptionally intense and 
prolonged winter cooling. 0.01 Kg/m3 is about the detection limit for changes in the density of 
LSW from decade to decade. 
