RECOMMENDATIONS 
Oceanographic Measurements 
A program to study the formation of North Atlantic Deep Water (NADW) should include an 
observational strategy which provides a measure of the amount of deep water formed each year 
and its temperature/salinity (T/S) properties. Also the oceanographic and atmospheric parame- 
ters which affect deep water formation processes must be monitored over the same time period. 
These processes are likely to exhibit considerable interannual variability; therefore, the 
measurement program should continue for at least 10 years. 
Production of NADW is believed to occur in the Norwegian, Greenland and Labrador Seas. 
However, it does not become NADW until it is able to escape over the 'sill'’ formed by the 
Greenland-Iceland-Faeroes-Scotland ridges into the North Atlantic. Our proposed strategy for 
minimum observations would include annual hydrographic cruises into the region of deep water 
formation and monitoring of the outflows across the sill. In addition, it is desirable to monitor 
the several inflows into the region of deep water formation, because each of these sources may 
have its own variability and sensitivity to environmental factors. An alternative to monitoring 
these sources may be provided by annual measurements of transient tracers and nutrients, which 
provide a mechanism to help identify the origin of different water masses. 
Hydrographic cruises each April/May into the Labrador Sea, Greenland Sea and Iceland Sea 
using high accuracy CTD (conductivity/temperature/salinity) systems would provide estimates of 
the amount and properties of NADW formed each winter. Existing data sets could be analyzed to 
determine the minimum station spacing required for this purpose. 
It is important also to monitor the outflows across the Greenland-Iceland-Faeroes-Scotland 
ridges. An overflow experiment conducted in 1973 and subsequent programs indicate that the 
mass flux and the T/S properties can be monitored with existing mooring and current meter tech- 
nology, although the accuracy, precision and long term stability of moored salinity sensors is 
still less than desired. While a proper design study would have to be made, it seems likely that 
such a moored array would need to include of the order of 10-12 moorings with 40-50 current 
meters equipped with temperature, conductivity and pressure sensors. T/S chains would also be 
valuable, if these can be developed. 
Monitoring of the outflows of deep water to the North Atlantic is not a sufficient measure- 
ment strategy by itself, because it does not allow one to distinguish between mechanisms which 
transform the source water masses and mechanisms which control the blending together of the 
source waters at the sills. It is therefore necessary to include a survey of the properties of 
the source waters in the regions of deep water formation each spring, as described above. 
In addition, over the same period, it is desirable to monitor the waters entering the for- 
mation regions. This would require monitoring the inflows from the Arctic as well as the 
inflows from the subtropical gyre, and the inflows of intermediate waters from the Labrador, 
Irminger and Mediterranean Seas. The flows from the Arctic in fact will be monitored, assuming 
that a proposed multi-year observational program centered on the Fram Strait goes forward as 
planned. If a similar monitoring of the inflow/outflow across the Greenland-Scotland-Norway 
ridges were put in place at the same time, this would create an excellent data set from which 
the processes of water mass transformation in the entire Norwegian/Greenland/Iceland Seas could 
be modeled and parameterized. 
Such a monitoring of inflows from the Arctic is not easy with present technology. Volume 
transport can probably be measured beneath sea ice using bottom mounted doppler or correlation 
sonar packages. These instruments are just now becoming available. These instruments might 
also be further modified to allow the pycnocline depth to be inferred in a manner similar to that 
of an inverted echo sounder. Monitoring of the T/S of the new surface waters of the East 
Greenland Current in the presence of ice will be very difficult. T/S chains could be deployed 
through holes in large ice floes and interrogated and tracked by satellites; however, they would 
have to be reseeded every few months. Subsurface moored instrumentation would have to be 
below the keel depths of pressure ridges and perhaps icebergs. The development of a self- 
contained bottom mounted wired/deck unit/recorder package which would take a profile of the 
water column at regular intervals using a S/T/P set up to a few meters of the bottom of the ice 
would be a useful component of this program. 
Recovery of moored instrumentation is expensive and difficult in remote and ice covered 
areas. On the other hand, surface instrumentation moored to the bottom is unlikely to survive a 
winter season. Consideration should be given to the modification of a package such as used in 
Rossby's 'RAFOS' floats which would record the data from the instrumentation in some reduced 
form (perhaps daily averages), return to the surface at some preset time and transmit the entire 
data via satellite over a period of several days. Such packages could be equipped with sensors 
