ASCENDANT 



their chai-acteristics as they move southward. 



(5) 



arctic anticyclone — See arctic high. 



Arctic Convergence — (or Arctic Convergence 

 zone, Arctic Convergence line). The Northern 

 Hemisphere polar convergence. Because of 

 the configuration of the oceans in the northern 

 latitudes, this convergence zone is poorly defined. 

 See convergence. 



Arctic Convergence line — See Arctic Conver- 

 gence. 



Arctic Convergence zone — See Arctic Conver- 

 gence. 



arctic high — (also called arctic anticyclone, folar 

 anticyclone, pol-ar high). A weak high that 

 appears on mean charts of sea-level pressure over 

 the Arctic Basin during late spring, summer, 

 and early autumn. ( 5 ) 



Arctic Intermediate Water — See water mass. 



arctic pack — 1. (sometimes called inany-year ice) . 

 Sea ice more than two years old. This nearly 

 salt-free ice has a smoothly undulating surface 

 due to the smoothing of pressure ice by weather- 

 ing. It also has a thickness of more than 2.5 

 meters (8.2 feet), and often is colored in differ- 

 ent tints of blue. (74) 



2. /S'ee polar ice (sense 1). (59) 



3. ( sometimes called jjolar ice ) . The drifting 

 ice floes of the Arctic Basin; specifically, the 

 thick, heavily hummocked polar ice of the cen- 

 tral Arctic Ocean. (59) 



arctic sea smoke — Same as steam fog ; but often 

 specifically applied to steam fog rising from 

 small areas of open water within sea ice. See 

 frost smoke, steam fog. ( 5 ) 



arctic smoke — See steam fog, frost smoke. 



arcuate delta — ^A curved or bowed delta with the 

 convex side toward the sea. 



arenaceous — Applied to rocks or sediments de- 

 rived from or containing sand. 



arenite — (also spelled arenyte). See sandstone. 



argillaceous — Applied to all rocks or sediment 

 composed partly or completely of clay. 



argil lite — A rock derived either from siltstone, 

 claystone, or shale. 



argonaut — See nautilus. 



Argus Island — An oceanographic research tower 

 erected on Plantagenet Bank 22 miles southwest 

 of Bermuda. 



arithmetic mean — (also called mean, average). 

 The sum of a set of individual values of any 

 quantity, divided by the number of values in the 

 set. 



arm — Any deep and comparatively narrow branch 

 of the sea extending inland, as opposed to gulfs 

 and firths. 



array — A group of two or more devices such as 

 hydrophones which feed into a common re- 

 ceiver. The purpose of thus grouping hydro- 

 phones is to increase coverage and sensitivity of 

 the listening unit and also to determine the bear- 

 ing of a target. 



arrival — The chronologic appearance (such as 

 first, second, third arrival) of different wave 

 energies on a seismic or acoustic record. 



arrow worm — (or chastognath, glass worm). 

 One of a phylum (Chaetognatha) of small, elon- 

 gate, transparent, wormlike animals pelagic in 

 all seas from the surface to great depths. They 

 are abundant and may multiply rapidly into vast 

 swarms. Some species of the group, especially 

 of the genus Sagitta, have been identified as 

 indicator species. 



arthropod — One of a phylum (Arthropoda) of 

 animals, most with a segmented external skele- 

 ton of chitin but some with plates of calcium 

 carbonate, and with jointed appendages; for ex- 

 ample, the crustaceans, spiders, and insects. 



artificial radioactivity — 1. A term used to denote 

 the phenomenon of radioactivity produced by 

 particle bombardment or electromagnetic irra- 

 diation. 



2. The radioactivity of synthetic nuclides. 

 See induced radioactivity. 

 (41) 



artificial sea water — Prepared solutions that 

 duplicate sea water as exactly as possible. The 

 following table shows three formulas for arti- 

 ficial sea water : (54) 



(SVERDRUP, ET. AL., 



artificial upwelling — The concept of having a 

 nuclear reactor (or other unnatural source) sit- 

 ting on the bottom of the ocean in cold, low 

 productivity parts of the sea to create warmth 

 needed to generate turbulence and subsequent 

 fertility to the area. 



ascendant — The vector representing the rate of 

 increase of a property. See gradient. 



207-109 0—66 



11 



