. Discovery reports. Discovery (Ship); Scientific expeditions; Ocean; Antarctica; Falkland Islands. HORIZONTAL DISTRIBUTION, GROWTH AND DYNAMICS OF DISPERSAL 319 picture that emerges is not always a very tidy one. Variation in the growth-rate alone must produce many seeming anomalies and the vagaries of the bottom and warm deep currents, and above all those of the surface drift, many more. Retarding winds, for instance, would tend to delay the arrival of the swarms in the east in certain years and assisting winds to advance it. Variation in the volume and speed of the cold deep current must al
. Discovery reports. Discovery (Ship); Scientific expeditions; Ocean; Antarctica; Falkland Islands. HORIZONTAL DISTRIBUTION, GROWTH AND DYNAMICS OF DISPERSAL 319 picture that emerges is not always a very tidy one. Variation in the growth-rate alone must produce many seeming anomalies and the vagaries of the bottom and warm deep currents, and above all those of the surface drift, many more. Retarding winds, for instance, would tend to delay the arrival of the swarms in the east in certain years and assisting winds to advance it. Variation in the volume and speed of the cold deep current must also play a part. It may be, for instance, that in exceptionally cold winters more bottom water is formed at the head of the Weddell Sea than usual, and that the flow of the bottom current itself is in consequence stronger after such winters than after mild ones.^ From this it would follow that the colder the winter the more swiftly the deep larvae would sub- sequently be carried away to the north and east, and conversely, the milder the winter the slower. c I OOn 090 oeo 0 70 0 60 0 50- 040 0 30 020- o 10 000. TEMPERATURE DEEP CATCH - 100 200 3005 4 00 500 1928 1929 I930 1931 1932 1933 1934 1935 1937 1938 Fig. 8i. Average annual catch of deep larvae and average temperature at 1500 m. The dynamics are further complicated by the existence of the warm crosswise intermediate current they must traverse before they reach the surface stream. Where it flows directly below the surface drift the major effect of this current would be to divert the deep larvae from their easterly course, tending in general to carry them farther south. The stronger the flow the greater the diversion, involving sometimes, it seems possible (p. 302), their transference from the Weddell to the East Wind zone. In general, however, its most likely effect would be to carry them away from a region where the surface drift was strong into another where it was weak, or vice versa, and so in the end again tend to advan
Size: 1810px × 1381px
Photo credit: © Paul Fearn / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, booksubjectocean, booksubjectscientificexpediti
