Subsurface Temperature Observations Research Articles

An early theory of ocean circulation: J.S. Von Waitz and his explanation of the currents in the strait of gibraltar

THE TASK of unravelling the factors governing the circulation of the oceans is one of the foremost in physical oceanography, yet the origin of the idea of the internal circulation of the ocean is obscure. Only since the time of the Challenger expedition, which sailed in 1872, has it been generally accepted that density differences within the ocean, due to variations in salinity and temperature, can set great water masses in motion. It was W. B. Carpenter's conviction, based on the earlier work of H.M.S's Lightning and Porcupine between 1868 and 1870, that cold dense water flowed from polar regions towards the equator in the ocean depths while a return flow of warmer lighter water took place at the surface, which led him to promote the expedition (DEACON, 1971). PRESTWlCH (1875) traced back similar ideas to the early 1800s. In the intervening years they had fallen out of favour when confusion arose over results obtained with Six self-registering thermometers, insufficiently protected against the effects of pressure (McCONNELL, 1978) and the widespread belief that sea water's maximum density occurred at the same temperature as in fresh water. Temperature differences were generally held to be responsible for circulation but some writers, such as MAURY (1855) in The Physical Geography of the Sea, thought that salinity was more important. Before the end of the 18th century it would not have been at all obvious from studying observations of subsurface temperature that such a situation existed. Measurements in the Mediterranean, such as those made by MARSIGLI (1725), indicated a mean temperature below the level affected by seasonal changes. There was no reason to think of this as exceptional and it fitted in well with the ideas of those who believed the centre of the earth to be warm, and its heat to be transmitted through the sea floor. If it were not for this and the vertical mixing which ensued, said DORTOUS DE MAIRAN (1749), the water in the depths of the sea would turn to ice. Measurements in the Southern Ocean, made on Captain Cook's second voyage, appeared to confirm this view by showing the existence of warmer water beneath the cold surface layer (DEACON, 1971). Proof of the presence of polar water in the depths of tropical seas was not obtained until after 1800 but THOMPSON (1798) had already explained examples of deep-sea temperature, below the atmospheric mean prevailing in the latitudes where they were taken, by the spread of cold water, due to its greater density. However, his was not the first attempt to outline a theory of ocean circulation. A similar idea, but relying on salinity instead of temperature differences, had been put forward in a remarkable paper nearly half a century earlier. In 1755 the Royal Swedish Academy of Sciences published in its Transactions a paper by a German author, HerrWAITZ, Privy Councillor to the Landgrave of Hesse-Cassel. It was entitled: 'An investigation into the reasons why the water of the Atlantic Ocean always flows into the Mediterranean Sea through the Straits of Gibraltar.' WAITZ (1755) argued that the difference

Subsurface Temperature in South Louisiana

Many subsurface temperature observations from South Louisiana were obtained from the Federal Power Commission. Most of the measurements were made with calibrated maximum thermometers long after the wells had been completed. Temperature-depth curves could be obtained for 123 fields. The temperature gradients ranged from 18 to 36° C/km of depth; most were between 22 and 24° C/km. At a depth of 3,048 m (10,000 ft) there is a belt of high temperature near the present coastline. This hot belt is located approximately where the sedimentary strata are believed to be of maximum thickness, which is estimated to be about 15,000 m. It is suggested that metamorphism and recrystallization already have begun in the lowest part of the sedimentary section, and the consequent increased thermal conductivity may account for the high temperatures along the belt of maximum thickness.

Subsurface Temperatures in South Louisiana: ABSTRACT

Subsurface-temperature observations, made by gas-producing companies in south Louisiana during the course of bottom-hole pressure determinations, were compiled on a magnetic tape by the Federal Power Commission. The measurements were taken long after the wells were completed, and they are therefore more nearly true than those taken during electric-logging operations. Reliable temperature versus depth plots could be made for 132 gas fields. The temperature End_Page 724------------------------------ gradients range from 1 to 2°F and most are between 1.2 and 1.3°F per 100 ft of depth. At a depth of 10,000 ft the temperature ranges between 190 and 230°F. The most prominent features of the temperature distribution at 10,000 ft is a of high temperature about 30 mi wide close to the present coastline. The location of this hot belt is puzzling because it is located approximately where the greatest thickness of Cenozoic sediments is believed to occur. Extrapolating the temperature and pressure downward, it seems possible that conditions necessary for regional metamorphism are present in the lower part of the sedimentary column at depths below 40,000 ft. Possibly the recrystallization of the sediments accounts for the high temperature values. End_of_Article - Last_Page 725------------