ENERGY BUDGET AND CIRCULATION 



DYNAMICS 



Sea -Air Interaction Study 



During the year, data from a laboratory 

 study were analyzed to describe rates of 

 evaporation and sensible heat exchange across 

 an air-water interface. The objectives were to 

 measure certain features expected to exist in 

 the few centimeters on either side of the inter- 

 face, to correlate these features with the 

 physics of air-water interaction, and to derive 

 a method for determining the rates of evapora- 

 tion and sensible heat exchange. The features 

 of interest were: (1) an evaporatively cooled 

 layer of surface water, (Z) temperature inver- 

 sions in the lowest few centimeters of air, 

 and (3) an intense moisture gradient in the 

 lowest layer of air. 



Characteristics of the temperature inver- 

 sions are apparently related to the configura- 

 tion of the associated moisture profiles. Be- 

 cause the inversions seem to be associated 

 with alternate layers of evaporation and con- 

 densation in the air, they also must indicate 

 the exchange rates of heat and moisture between 

 the air and water. With increasing air-water 

 tennperature differences, the exchange rates 

 seemingly do not increase linearly as pre- 

 dicted by equations, but rather stepwise. These 

 "steps" are apparently associated with the 

 necessity for a nnore efficient vertical flux of 

 heat and nnoisture. 



Level -of -No-Motion Study 



Determination of relative ocean currents by 

 geostrophic computations of serial hydro- 

 graphic station data is a basic tool in oceanog- 

 raphy. Converting the "relative" currents to 

 "absolute" values is accomplishedby defining a 

 "level-of-no-motion"; no acceptable technique, 

 however, has been devised for defining the 

 no-motion level. During the year, a method for 

 determining this level was devised and is being 

 exannined by using data gathered in the Gulf of 

 Mexico. If this technique proves correct, our 

 ability to describe the ocean current structure 

 will be greatly improved. 



Reed S. Armstrong, Project Leader 



TRENDS IN OCEANIC CONDITIONS 



A study to describe the physical properties 

 of water of the Gulf of Mexico was begun during 

 the year with three cruises (9th, 1 0th, and 1 Zth) 

 of the R/V Geronimo . 



One of the activities of the ninth cruise was 

 a hydrographic survey of the upper 300 m. 

 (164 fathoms) of water over the slope of the 

 Continental Shelf off Florida in the Gulf of 



Mexico. Twenty hydrographic stations were 

 occupied between June 30 and July 13, 1966. 

 During August 4-18, about a month later, the 

 R/V Alaminos (Texas A&M Research vessel) 

 made hydrographic observations during a 

 cruise in the eastern Gulf. A comparison of 

 the data from the two cruises indicated the 

 presence of two clockwise-rotating gyres 

 superinnposed on the mean flow. One gyre was 

 in the northern portion, and the other in the 

 southeastern sector of the eastern Gulf. Both 

 gyres were still present in February- March 

 1967 during cruise 1 2 of the R/V Geronimo . 



The gyres had changed in position and con- 

 figuration during the month between cruise 9 

 and that of the R/V Alaminos . These results 

 were interpreted to mean that ocean circu- 

 lations are not steady and that the character- 

 istics of water masses might change over 

 rather short time periods. 



Cruise 10 of the R/'V Geronimo was nnade 

 November 8-17 to obtain data on the waters 

 around the Mississippi River Delta. The pri- 

 mary purpose of the operation was to establish 

 "ground truth" for the photographs taken from 

 the Gemini XII manned space flight. The station 

 plan of the cruise was organized to exhibit the 

 scale of oceanic features observable fronn 

 satellite photographs. Although cloudiness pre- 

 vented photographing the surveyed area, the 

 cruise was successful in obtaining detailed 

 information on this sparsely sampledarea. 



Data on temperature, salinity, dissolvedoxy- 

 gen, and inorganic nutrients were collected 

 from 79 hydrographic stations during cruise 10. 

 Analysis of these data revealed that the water 

 from the Mississippi River was not discharged 

 in any regular pattern, but moved seaward in 

 three different forms: (1) flows that hugged 

 the coastline, (Z) tongues that penetrated di- 

 rectly seaward, and (3) a tongue that extended 

 into a well-defined, semipermanent, cyclonic 

 eddy to the east of the delta (fig. Z4). 



Although the Mississippi River is the largest 

 river emptying into the Gulf of Mexico, the 

 discharge from the river (salinities less than 

 34 p.p.t.) generally was kept within 55 km. 

 (30 nautical miles) of the coast. The large eddy 

 to the east of the delta apparently resulted 

 from the low-salinity river water being drawn 

 seaward by an offshore, northeasterly current. 



Cruise IZ of the R/V Geronimo (February ZO 

 to April I, 1967) was the first of an expected 

 series of hydrographic surveys of all the 

 waters of the Gulf. Repeated problems with the 

 ship's navigational gear required that the 

 operations be curtailed in the eastern Gulf, 

 but the cruise plan was rearranged so that 

 a survey of the entire Gulf could be made. 

 During this cruise, 1 14 hydrographic stations 

 were occupied and Z81 bathythernnograph casts 

 were made. Vertical plankton hauls to 100-m. 

 (55-fathonn) depth at each hydrographic station 

 and a nun-iber of vertical hauls to near the bot- 

 tonn in the basins of the Gulf were planned, but 



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