TROPIC HIGHER HIGH WATER 



flood and successive ebb currents occur at this 

 time. 



tropic higher high water — (abbreviated 

 TcHHW). The mean higher high water of 

 tropic tides. (68) 



tropic higher high water interval — (abbreviated 

 (TcHHWI) . The lunitidal interval pertaining 

 to the mean higher high waters at the time of 

 tropic tides. (68) See lunitidal interval. 



tropic higher low water — (abbreviated 

 TcHLW). The mean higher low water of 

 tropic tides. (68) 



tropic high water inequality — (abbreviated 

 HWQ). The avei-age difference between tlie 

 lieights of the two high waters of the tidal day 

 at the time of tropic tides. See diurnal in- 

 equality. (68) 



tropic inequalities— Tropic high water inequal- 

 ity is tlie average difference between the two 

 high waters at the times of tropic tides. Tropic 

 low water inequality is tlie average difference 

 between the two low waters at the times of 

 tropic tides. The terms are applicable only 

 when the type of tide is semidiurnal or mixed. 



tropic intervals — Tropic higher high water in- 

 terval is the lunitidal interval of the higher high 

 waters at the time of the tropic tides. Tropic 

 lower low water interval is tlie lunitidal inter- 

 val of the lower low waters at the time of the 

 tropic tides. See lunitidal interval. 



tropic lower high water — (abbreviated Tc- 

 LHW) . The mean lower high water of tropic 

 tides. (68) 



tropic lower low water — (abbreviated TcLLW). 

 The mean lower low water of tropic tides. 

 (68) 



tropic lower low water interval — (abbreviated 

 TcLLWI). The lunitidal inten^al pertaining 

 to the mean lower low waters at the time of 

 tropic tides. (68) See lunitidal interval. 



tropic low water inequality — (abbreviated 

 LWQ). The average difference between tlie 

 heights of the two low waters of the tidal day 

 at the time of tropic tides. See diurnal in- 

 equality. (68) 



tropic range — Contracted form of great tropic 

 range. 



tropic tide — The tide that occurs twice monthly 

 wlien the effect of the moon's maximum declina- 

 tion north or south of the Equator is greatest. 

 See tropic currents. 



tropic velocity — The speed of the greater flood 

 or greater ebb tidal currents at the time of tropic 

 tides. (68) 



troposphere — From an analogy witli the atmos- 

 phere, the term applied by some oceanographers 

 to the upper layer of the oceans in middle and 

 low latitudes. This layer is characterized by 

 I'elatively high temperatures and strong cur- 

 rents, and is generally bounded by the top of 

 the thermocline. (54) See stratosphere. 



trough — 1. A long depression of the sea floor nor- 

 mally wider and shallower than a trench. (62) 

 2. See wave trough. 



try net — A small shrimp trawl 12 to 24 feet wide 

 designed for exploration of shrimp grounds. 

 This net is frequently used for biological sam- 

 pling of benthic fishes. 



T-S curve — See temperature-salinity diagram. 



T-S diagram — See temperature-salinity dia- 

 gram. 



T-S relation — See temperature-salinity dia- 

 gram. 



tsunami — (or funami, tidal wave, seismic sea 

 wave). A long-period sea wave produced by a 

 submarine earthquake or volcanic eruption. It 

 may travel unnoticed across the ocean for 

 thousands of miles from its point of origin and 

 builds up to great heights over shoal water. 



Tsushima Current — That part of the Kuroshio 

 flowing northeastward through Korea Strait and 

 along the Japanese coast in the Sea of Japan; 

 it sets strongly eastward through Tsugaru Strait 

 at speeds to 7 knots. 



T-3 — (also called Fletcher'' s ice island, Drift Sta- 

 tion Bravo). A drifting ice island of the Arctic 

 Ocean, probably formed by the calving of shelf 

 ice from Ward Hunt Island in the Canadian 

 Archipelago. T-3 is short for Target-3, so 

 named because it was first observed by radar 

 from aircraft in July 1950. (T-1, originally 

 called Target-X, was first seen on radar m Au- 

 gust 1946.) T-3 has been occupied intermit- 

 tently as a scientific drift station since 1952, 

 first by the U. S. Air Force, and since February 

 1962 by the Arctic Research Laboratory of Point 

 Barrow, Alaska. During the IGY, it was known 

 as Drift Station Bravo. It is also known as 

 Fletcher's ice island after Colonel Joseph O. 

 Fletcher, its first station leader. 



tubeworm — Any polychaete, chiefly the serpulids 

 or sabellids, that builds a calcareous or leathery 

 tube on a submerged svirface. Tubeworms are 

 notable fouling organisms. 



tufa — A chemical sedimentary rock composed of 

 calcium carbonate or silica, precipitated from 

 percolating ground water or from a spring. 



tuff — Cemented consolidated volcanic ash. 



tunami — See tsunami. 



tunic — The outer cuticular covering of tunicates. 

 (47) 



tunicate(s) — One of a subphylum (Tunicata or 

 Urochordata) of globular or cylindrical, often 

 saclike animals, many of which are covered by 

 a tough flexible tunic. Many are sessile, others 

 are pelagic, and some are strongly luminescent. 

 See ascidian, pyrosome, salp. 



turbidite — Turbidity current deposits charac- 

 terized by botli vertically and horizontally 

 graded bedding. 



turbidity — Reduced water clarity resulting from 

 the presence of suspended matter. Water is con- 

 sidered turbid when its load of suspended matter 



170 



