scholarly journals Carbonate dissolution rates at the deep ocean floor

2013 ◽  
Vol 40 (4) ◽  
pp. 744-748 ◽  
Author(s):  
Bernard P. Boudreau
Author(s):  
Steinar Løve Ellefmo ◽  
Thomas Kuhn

AbstractMinerals and metals are of uttermost importance in our society, and mineral resources on and beneath the deep ocean floor represent a huge potential. Deciding whether mining from the deep ocean floor is financially, environmentally and technologically feasible requires information. Due to great depths and harsh conditions, this information is expensive and time and resource consuming to obtain. It is therefore important to use every piece of data in an optimum way. In this study, data retrieved from images and expert knowledge were used to estimate minimum and maximum nodule abundances at image locations from an area in the Clarion-Clipperton-Zone of the equatorial North East Pacific. From the minimum and maximum values, box cores and the spatial correlation quantified through variogram, a conditional expectation and associated uncertainty were obtained through the Gibbs sampler. The conditional expectation and the uncertainty were used with the assumed certain abundance data from the box cores in a kriging exercise to obtain better informed estimates of the block by block abundance. The quality assessment of the estimations was done based on distance criterion and on kriging quality indicators like the slope of regression and the weight of the mean. From the original image locations, alternative image configurations were tested, and it was shown that such alternatives produce better estimates, without extra costs. Future improvements will focus on improving the estimation of the minimum and the maximum values at image locations.


1978 ◽  
Vol 10 (1) ◽  
pp. 112-129 ◽  
Author(s):  
Teh-Lung Ku ◽  
Tadamichi Oba

A method is proposed by which the degree of attrition of the tests of certain foraminifera species, such as Globorotalia menardii and Globorotalia tumida, is used to “scale” the amount of CaCO3 that has been dissolved from sediment. The scale is calibrated experimentally in the laboratory. The method has been applied to three calcareous cores from the Pacific and the Indian Oceans. It is shown that the original CaCO3 contents in these cores were high (82–95%) and relatively uniform compared to the present down-core values. About 65 to 85% of the originally deposited CaCO3 has been dissolved, corresponding to dissolution rates on the order of 0.1-0.3 moles/cm2/yr. These results indicate that appreciable solution could have occurred on sea floor rich in calcareous sediments and that the variation in CaCO3 content in a core may have resulted largely from dissolution. The difference in the degree of solution between glacial and interglacial sediments in these cores is not so distinct, with ⋍ 10% less intense dissolution during glacial times on the average. However, the dissolution minimum occurring around the late Wisconsin glaciation (10,000–20,000 yr B.P.) previously noted in several cores elsewhere is confirmed. At that time, near the site of core M70 PC-20 in the southwest Pacific, the CO32− concentration of the bottom water is estimated to have been approximately 5% higher than the present value, and the calcite lysocline was about 300 m deeper. To evaluate possible variations in CaCO3 deposition rate across the glacial-interglacial transitions requires precise age control, which the present study lacks.


2004 ◽  
Vol 89 (516) ◽  
pp. 437-440 ◽  
Author(s):  
Maurice N. Brearley

A tsunami usually starts on deep ocean water as a result of a submarine earthquake. A tsunami wave is very long, even as much as tens of kilometres, but of only very small amplitude, typically less than half a metre (Bascom [1]). In mid-ocean, the passage of a tsunami is imperceptible, but on reaching a shore it can achieve great heights and can deliver massive surges of water. Before the arrival of the first surge, and between subsequent surges, the water at a shore line usually retracts for a long distance, leaving bare large areas of ocean floor that are normally under water. This paper analyses the behaviour of a tsunami, and explains how its mid-ocean character is transformed to produce such massive surges of water at a shore line.


1971 ◽  
Vol 11 (1) ◽  
pp. 27
Author(s):  
J. B. R. Livermore

For countless centuries the activities of man were bounded, in the main, by the limits of the dry land on which he lived. Some of the more intrepid ventured out upon the seas and oceans — to fish, to explore, to trade, or to fight. In the twentieth century man has conquered the air and circled the globe in space.Now the world looks to another new frontier — the field of exploration of the seabed beneath the oceans. In recent decades there has been an awakening to the existence of natural resources in the seabed and ocean floor.Tliis prospect of discoiering, and more importantly producing, minerals from the deep ocean floor, appears to offer the potential of expanding the resource base of modern civilisation at a time when a growing world population, coupled with rising standards of living, are throwing increased demands on the world's known stock of natural resources.For three years the United Nations, following an initiative by the island state of Malta, has been discussing the reservation, exclusively for peaceful purposes, of the seabed and ocean floor beyond the limits of national jurisdiction, and the use of the resources of this area, in the interests of mankind as a whole.During these discussions diverse points of view have emerged: some would restrict the jurisdiction of a coastal state severely; others argue for extensive coastal state jurisdiction. Some want elaborate and comprehensive international machinery to control all activities on the seabed in accordance with a regime agreed internationally; others support more modest arrangements arguing that elaborate machinery would swallow up the financial benefits and leave little or nothing for the world community; still others contend that the regime and machinery should, initially at least, be resource oriented.The Australian delegation has put the view that any international arrangements for the deep seabed must be effective, credible and impartial. Such arrangements must not only command the support of the nations of the world regardless of geographical location or political system, they must also instil confidence in the minds of operators that rights granted can, and will, be upheld.Moves are developing for a further comprehensive law of the sea conference — perhaps within two or three years - which will tackle several outstanding matters including, importantly, that of a suitable regime and administrative machinery for the seabed and ocean floor beyond national jurisdiction. Inevitably this will involve consideration of the imprecision of the limits of the continental shelf as presently defined by the Geneva Convention of 1958. Other subjects requiring attention are the breadth of the territorial sea, rights of passage through straits and fisheries matters.Australia, an island continent with a long coastline and an extensive continental shelf, has a vital interest in the course of these deliberations.


2009 ◽  
Vol 2009 (0) ◽  
pp. _1P1-A14_1-_1P1-A14_4
Author(s):  
Takeshi NAKATANI ◽  
Tamaki URA ◽  
Takashi SAKAMAKI ◽  
Junichi Kojima

Geophysics ◽  
1991 ◽  
Vol 56 (8) ◽  
pp. 1153-1157 ◽  
Author(s):  
Andrew R. Ochadlick

Magnetic data sets over deep ocean areas may contain clues to the existence of craters formed by the impact of an extraterrestrial body with the Earth’s ocean crust. To aid in the magnetic exploration of the ocean crust for oceanic impact craters, basic but effective computations from an impact model are studied from an aeromagnetic point of view. The main assumption of the analysis is that a sufficiently large impact can excavate large volumes of magnetized basalt, vaporize basalt, and raise basalt to temperatures above the Curie temperature (approximately 500°C) to alter the preimpact magnetization of the ocean floor and result in a magnetic anomaly being associated with an oceanic impact crater. In the absence of an existing theory on the influence of impacts on ocean crustal magnetization, the representation of a crater on the ocean floor by a simple potential provides, apparently for the first time, quantitative estimates of the crater’s magnetic anomaly along a horizontal surface. Numerical results from the model suggest that the detection of the anomaly of a Cretaceous‐Tertiary (K-T) type of impact is well within the capabilities of aeromagnetic technology.


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