dication of the important scales, but more important, provides strong moti- 

 vation for further study. The tracking of neutrally buoyant floats off Ber- 

 muda in 1959-60 from RV Aries first indicated the existence of irregular 

 mesoscale motions in the deep water an order of magnitude more energetic 

 (5-10 cm/sec, 200km, 40 days) than the anticipated value for the mean 

 flow. These motions appear to be quasi-geostrophic, with significant energy 

 in both the barotropic and baroclinic modes. If these horizontal motions 

 are correlated with a coefl[icient of 0.1 they constitute a mid-ocean source 

 of mean vorticity comparable to that due to the mean wind stress curl. 



In the past decade significant technological advances have been made 

 in oceanographic instrumentation. The considerable data obtained from 

 moored current meters, together with some Lagrangian float tracks, time 

 series temperature records obtained off Bermuda, and towed thermistor 

 records, provide consistent empirical evidence for the existence of the low 

 frequency mesoscale eddies. 



Field Project 



The field project is scheduled to begin with several small arrays of 

 moored instruments in November 1971, to be followed by various tests 

 and trials of new instrumentation during 1972, and culminating in the 

 intensive MODE-I experiment during March through June of 1973. 



At that time measurements will be concentrated in a 200-km square 



near 28° N., 68° W. Three U.S. and one British research vessel, shown 



30 in Figure 12 will participate in launching various free-floating devices 



and moored instrumentation. The ships will also conduct a program of 

 standard measurements of the temperature and salinity fields. 



The fixed array of moored instruments consists of recording current 

 meters (about 50, on 16 buoy moorings) and some temperature recording 

 instruments of new design. Free-floating instruments will include about 

 20 widely dispersed, large, neutrally buoyant floats, situated at about 1200 

 meters depth in the sound channel, tracked acoustically by remote observa- 

 tion stations. A small cluster of about 50 floats will be tracked by a mov- 

 able hydrophone array. Free dropping vertical profiling instruments will 

 be launched from ships and aircraft, measuring salinity, temperature, 

 and horizontal currents. In addition, there will be two varieties of bottom 

 pressure gauges, inverted echo sounders, and geomagnetic electric field 

 recorders. These diverse measurement systems will be deployed in such 

 a way that the results will supplement each other, permitting optimum 

 synoptic mapping of the mesoscale velocity and density fields. 



Project Management 



The various components of MODE-I are substantial experiments in 

 their own right. From one point of view, MODE-I is an assembly of as- 

 sociated experiments with fairly loose coordination and a decentralized 

 technological base. But experiments performed simultaneously and in the 

 same place strengthen each other by providing intercomparison and a 

 richer field of data. More important is the demand that MODE-I makes 

 for explicit decisions and the careful weighing of differing needs. 



