Hancy, R. L., and R. W. Davies. 1976. The role of surface 

 mixing in the seasonal variation of the ocean thermal 

 structure. J. Phys. Oc. 6:504-510. 



McCreary, J. 1976. Eastern tropical ocean response to chang- 

 ing wind systems: with application to El Nifio. J. Phys. 

 Oc. 6:632-645. 



Namias, J. 1976. Negative ocean-air feedback systems over the 

 North Pacific in the transition from warm to cold seasons. 

 Monthly Weath. Rev. 104:1107-1121. 



Royer, T. C. 1976. A note comparing historical sea-surface 

 temperature observations at Ocean Station P. J. Phys. Oc. 

 6:969-971. 



Sadler, J. C, L. Oda, and B. L, Kilonsky. 1976. Pacific Ocean 

 cloudiness from satellite observations. (Atlas). Dep. Met. 

 Univ. Hawaii UHMET 76-01, 137 p. 



Saur. J. F. T. 1976. Early April observations of the northeast 

 Pacific transition zone prior to the 1976 albacore fishing 

 season. Fishing information no. 4, April, U.S. Dep. Com- 

 mer. NOAA/NMFS, Southwest Fisheries Center, La 

 Jolla, Calif, p. 4-18. 



Stidd, C. K. 1974. Momentum transfer and surface pressure. 

 Geofisica Internacional 14:207-221. 



White, W. B., and J. B. McCreary. 1976. On the formation of 

 the Kuroshio meander and its relationship to the large- 

 scale ocean circulations. Deep-Sca Res. 23:33-47. 



Wyrtki, K. The dynamic topography of the Pacific Ocean and 

 its fluctuations. HlG-74-5, Hawaii Inst, of Geophys., 

 Univ. Hawaii, 56. p. 



International Southern Ocean Studies (ISOS) 



ISOS is concerned with understanding the long-term, 

 large-scale variability of dynamical processes in the Southern 

 Ocean. It consists of a series of experiments to determine global 

 atmospheric and oceanic circulation and their interaction. The 

 project has focused on the dynamics of the Antarctic Circum- 

 polar Current, the First Dynamic Response and Kinematics 

 Experiment (F DRAKE), but studies have been made of 

 bottom-water formation and the Polar Front. The objectives 

 of ISOS and F DRAKE cruises are to: 



1. Identify the statistical properties and space-time scales of 

 variability in selected regions of the Antarctic Circumpolar 

 Current system. 



2. Subject to critical test theories of local dynamical balance, 

 mixing, and exchange with other oceans. 



3. Develop a basis for understanding the role of large-scale 

 circulation and air-sea interaction in the Southern Ocean in 

 global climate dynamics. 



These objectives will be met through a sequence of 

 monitoring and dynamics experiments in several regions of the 

 Antarctic Circumpolar Current System (ACCS), long-term 

 monitoring of certain large-scale properties, analysis of exist- 

 ing data sets, and numerical, analytical, and laboratory model- 

 ing. ISOS projects are listed in table II. 



F DRAKE (First Dynamic Response and Kinematics Experi- 

 ment) 



The first such experiment, F DRAKE, combines both 

 a monitoring effort and local experiments. It began in the 

 austral summer of 1974-75 and will terminate in 1977. The 

 goals of F DRAKE are: 1) to describe the energy-containing 

 space and time scales in the Drake Passage in order to design 

 a long-term transport-monitoring experiment for the ACC to be 

 carried out during FGGE; and 2) to describe selected prop- 

 erty distributions within the Drake Passage and the Western 

 Scotia Sea for the continuing study of mixing processes, par- 

 ticularly in the Polar Front Zone (PFZ), which are involved 

 in the formation of Antarctic Intermediate Water. 



To assess the spatial and temporal variability of the cur- 

 rents and to estimate the yearly, mean flow at 2,700 m depth 

 in the Drake Passage, an array of 15 moorings instrumented 

 with current meters was deployed in March 1975. The array 

 consisted of 7 short-term (20 days duration) and 8 long-term 

 (1-year duration) moorings. The short-term array of 15 

 moorings was designed to study spatial variability; the long- 

 term array to study temporal variability and to estimate a 

 mean flow. During the short-term experiment, 14 current meters 

 yielded current measurements at an average depth of 2,750 

 m; during the long-term experiment, six current meters re- 

 corded velocity at a mean depth of 2,750 m for more than 

 250 days. An autocorrelation function from down-channel 

 velocities was calculated for each long-term current record. 

 The period of the first zero-crossing of the autocorrelation 

 function, which averaged 14 days, was used as an estimate of 

 the time-scale of independent sampling of the low-frequency 

 velocities. 



Cross-correlation coefficients between down-channel 

 velocities for each pair of moorings were not significantly non- 

 zero at 95 percent confidence limits even for the smallest long- 

 term mooring separation of 80 km. Fourteen-day averaged 

 velocities for the short-term array of 14 moorings (fig. 15) 

 illustrate the spatial noncorrelation. This noncorrelation may 

 be due to control of the currents at 2,750 m depth by small- 

 scale bottom topography that rises to depths as shallow as 

 2,400 m. The preferred explanation for the low correlation is 

 that the low-frequency velocities vary over spatial scales 

 smaller than the mooring separations. In other ocean experi- 

 ments, velocities have been found to vary over spatial scales 

 the size of the Rossby radius of deformation. Estimates of the 

 Rossby radius, based on measurements of temperature and 

 saHnity versus depth near 60°S, is 15 km. Thus, variations of 

 low-frequency currents may occur over distances of 15 km, 

 and nonsignificant correlations over separations of 80 km are 

 not unexpected. 



To estimate the spatial variability of the currents, a mean 

 velocity at 2,750 m in the Drake Passage for each 14-day 

 period and a variance about that mean are calculated from the 

 six long-term current records. An estimate of the standard devi- 

 ation for the population of current measurements at 2,750 m in 

 the Drake Passage is taken as the square-root of the average 

 variance, which equals 4.8 cm/s. 



The mean down-channel flow at 2,750 m depth in the 

 Drake Passage is estimated for each 14-day period (fig. 16) 

 by averaging the velocities available during each period. 

 Errors, representing standard errors of the mean, are 1.3 



30 



