33.5°/oo and the arrival 33.0°/oo water found during 

 the thu'd survey. The salinity reduction m this 

 area and on the Banks would cause the calculated 

 elevation of the sea surface as the Banks are 

 approached. In the trough area, the dynamic 

 height change between the first survey, station 

 9259 ; and the check survey; station 9305, as shown 

 in figure SA, is almost negligible. A significant 

 change is detected on the third survey. Exami- 

 nation of the temperature and salinity curves of 

 figure lOA discloses that significant salinity 

 changes were not found in this area until the third 

 survey, when both s^ reduction in salinity and 

 temperature was observed. Because the trough 

 stations showed little elevation change over the 

 short period between the first and check surveys, 

 it would seem that the flow of the Labrador 

 Current at this time affected or was affected by 

 the characteristics of the Banks and adjacent 

 continental slope water. 



Isobaric Slope 



The Labrador Current can be thought of as an 

 edge phenomenon, flowing as the result of steady 

 state requii'ements of the sea height difference 

 between light, low salmity water on the Grand 

 Banks and slope and the heavier, higher salinity 

 water located off the slope between the Labrador 

 and the Atlantic Current. This edge phenomenon 

 can be obsers^ed from the velocity profiles and 

 isotherms for the Labrador Current m section U, 

 figure 1 lA. It can be seen that the fastest flowing 

 water is not necessarily the coldest, but grades 

 colder and less saline as the Banks are approached. 

 Thus, a wedge of low tempei-ature, low salinity 

 water overrides mixed water of less scAcre char- 

 acteristics. Because light-cold water and heavy- 

 warm water are anomalous relationships, it is 

 apparent tluit sainiity cojitrols the density in this 

 current regime. 



Figure SA sliows the section U plot of the 

 dynamic heights indicating the gross changes that 

 occurred over the periods between the surA-eys. 

 Note that only snudl changes occurred on the 

 Banks between the check siu'vey and tlie third 

 survey which were separated by more than a 

 month. Observe also the gradual elevation of the 

 trough station during the two periods, leading to 

 the s])eculati()n that this mixed water is slowly 

 changing its characteristics as the spring pro- 

 gresses. However, this cannot be conclusively 

 proved because the location of tiie lowest station, 

 in dynamic height, does not mean thiit it was 



actually situated at the lowest sea surface eleva- 

 tion point. Figure 12A, a T-S plot from stations 

 9259 and 9388 of the first and third surveys in the 

 mixed water trough shows a density decrease with 

 time above 600 meters, with the reduced salinity 

 causing the density to decrease even under condi- 

 tions of decreasing temperature at mid-depth. 



The changing isobaric slope between the two 

 water masses allows greater or lesser volumes of 

 water to be transported. This slope can be ad- 

 justed either by a changing of the dynamic height 

 of the trough (mixed water) or the surface dynamic 

 height on the Banks. 



The changes observed between the survey 

 periods leads to the hypothesis that an increase 

 in the dynamic height of the water on the Banks 

 and slope caused a swifter warmer current to flow 

 during the check survey than during the first 

 survey. This increase of the height of the water 

 on the Banks could be caused by the influx of 

 arctic and sub-arctic melt water from the north. 

 It could be assumed here that we were observing 

 cause, adjustment, and affect. This means that 

 the increase in elevation of water on the Banks 

 and slope, with a resulting water volume flow- 

 increase, causes entrainment of the existing water 

 in the area. This slope water woidd then become 

 colder with the arrival from the north of greater 

 volumes of cold w-ater to fulfill the mass continuity 

 requirements being satisfied by entrainment. 

 Alternately, the warmer mean temperatures ob- 

 served during the check survey could be the result 

 of linearizing the velocity data between stations 

 thus causing an apparent volume flow in warmer 

 water. The small reduction of the volvune flow, as 

 seen on the third survey, would result from the 

 greater elevation of the sea surface in the trough 

 area due to the eventual mixing of these more 

 severe water properties as the water transits to 

 the Tail-of-the-Banks and then back up through 

 section U. 



Eastern Banks and Slope Controls 



The concepts discussed above are postulated 

 from only three sections and need further work to 

 be completely substantiated; however, the spring 

 fresliening of the Grand Banks water is a fact 

 and its influence on the mixed water and the 

 resulting slope of llie sea surface between tiie two 

 water masses is a logical outcome. It is apparent 

 from a fiu'tlier amilysis of the data, that tlie 

 water on the Grand Banks changes as the season 

 progresses aiul wovdd require some form of ad- 



