11 
The fact that the Labrador Sea Water mass all cooled by 0.5°C in less than a decade indi- 
cates that the intermediate waters of the ocean can respond to climatic changes over periods of 
a few years. In an analysis of the subsurface data collected between 1964 and 1974 at OWS 
Bravo, Lazier (1980) showed that beginning in 1967 or 1968, the salinity of the upper few 
hundred meters of the Central Labrador Sea began to decrease at a rate faster than 0.1°/oo/year 
at 10 meters (Figure 4). At 1,000 metres, salinity began increasing at a rate of 0.01°/oo/year. 
In the winter of 1972, the upper layer values returned to their more normal range while 1,000 
metre values decreased in salinity to values 0.04-0.06°/oo less than those seen in the period 
1964-1966. 
Lazier (1980) suggested that during the late 60's, increased Arctic outflow or increased 
offshore transport of low salinity Arctic outflow from the Labrador and Greenland currents 
spread a low salinity surface layer over the Central Labrador Sea. This increased the vertical 
stability within the upper water column and surpressed convection. Over a series of mild win- 
ters, the vertical stability increased making it more difficult for convection to take place. 
Finally, the intense winter of 1972 broke through the stability and mixed the fresh water deep 
into the water column. This low salinity input during the late 1960's resulted in the low salinity 
LSW that was observed forming in 1976. 
This freshening was not confined to the Labrador Sea. The section from Cape Farewell 
south to Flemish Cap (Figure 5) shows that the entire upper 2 km of water column except for the 
warm salty North Atlantic Current has decreased its salinity and cooled. It is also possible that 
there has been some freshening of the NADW near the boundaries, especially the northern one. 
This freshening therefore affected the Irminger Sea Water formed to the east of Greenland as 
well as the Labrador Sea Water and perhaps the waters formed north of Iceland and overflowing 
into the North Atlantic. What we are seeing is not just one component of the northern inter- 
mediate water masses changing; we are seeing all of them changing and this implies a change 
imposed over a large area of the sub polar Atlantic Ocean. 
