Pacific Common Water

The Circumpolar Current is a blend of waters of North Atlantic ( 47%) and Antarctic margin ( 53%) origin (Broecker, 1997). This current is referred to as the Pacific Common Water and is the source of deep water to the Indian and... 

Aside from identifying air injection as a common feature in most waters and excess He in Pacific deep waters, noble gas elemental abundances have also been used as tracers for water masses and to study mixing in intermediate waters. Discussions are given by Bieri et al. (1966, 1968), Craig, Weiss and Clarke (1967), Craig and Weiss (1968), and Bieri and Koide (1972). On the whole, the arguments cut finer and are therefore closer to the limit of experimental uncertainties than the air injection and excess He features discussed earlier, and so are less definitive in any case, they seem not to have made any large impact on marine science. 

When REE fractionation is discussed, it is common to normalize the data to the values in shale which are thought to be representative of the REEs in the upper continental crust. The shale-normalization not only helps to eliminate the well-known distinctive even-odd variation in natural abundance (the Oddo-Har-kins effect) of REEs but also visualizes, to a first approximation, fractionation relative to the continental source. It should be noted, however, that different shale values in the literature have been employed for normalization, together with the ones of the Post-Archean Australian Sedimentary rocks (PAAS) adopted here (Table 1). Thus, caution must be paid on the choice of the shale values if one ought to interpret small anomalies at the strictly trivalent lanthanides such as Gd and Tb. Alternatively, for detailed arguments concerning fractionation between different water masses in the ocean, it has been recommended that the data are normalized relative to the REE values of a distinctive reference water mass, for example, the North Pacific Deep Water (NPDW, Table 1). The NPDW-normalization eliminates the common features of seawater that appeared in the shale-normalized REE pattern and can single out fractionation relative to the REEs in the dissolved end product in the route of the global ocean circulation. 

Over the past decade, plastic debris has become a common feature of beaches and coastal waters adjoining populated areas of Europe (36-38), the Mediterranean (39-41), North and Central America (42-44) and New Zealand (45). Plastics are also present in the open ocean both near the major shipping lanes and in the most remote regions of the world (the Arctic (46), the Benguela Current (47), the Cape Basin area of the South Atlantic (48), the Humboldt Current in the South Pacific (49), and the Antarctic (50, 51). 

The vertical trends in POM fluxes exhibit temporal and geographic variability. This was shown in Figure 23.3, in which seasonal shifts in surface productivity were seen to affect the subsurface particle fluxes even in deep waters. Other processes that can affect the sinking flux of POM include (1) in situ production by mid-water microbes or zooplankton and (2) lateral transport of POM via advective currents. Both can produce mid-water maxima in the sinking organic matter fluxes. Geographic variability in these fluxes is common. As illustrated in Figure 23.6 for the central equatorial Pacific Ocean,... 

The aqueous solution (No. 1) cannot be doubted. Quartz (No. 2) is common in sediments, and since Si02 is an excess component, quartz seems to be a strong candidate. Four clay minerals, kaolinite (No. 3), illite = hydromica (No. 4), chlorite (No. 5), and montmorillonite (No. 6) have been found together in various proportions in most parts of the ocean. These all seem to be good candidates. Phillipsite (No. 7), a zeolite, has been found growing in sea water (especially in the Pacific... 

For example, a 3 per cent, solution of common salt at 10° C. is much more corrosive than tap water at the same temperature but as the temperature rises the relative corrosivity falls, so much so that at 21° C. the salt solution is the 1 ess corrosive of the two. Since sea water contains some 3 per cent, of sodium chloride, it is of interest to inquire into the effect of temperature upon its corrosive powers. The few laboratory tests that have been carried out on the subject2 indicate that at temperatures below 13° C. sea water is more corrosive than tap water, whilst at all higher temperatures it is less so. Now, in the western part of the tropical Pacific Ocean a temperature of 32° C. is sometimes attained, and in the Red Sea and Persian Gulf temperatures of 34 4° C. and 35 5° C. respectively have been registered. Such waters should therefore prove less corrosive than river waters at the same temperatures. 

Marine processes. Sea water reacts with ocean-bed sediments containing volcanic ash, or biogenic silica from Radiolarians, to form zeolites. This process is common in deep-sea sediments and phillipsite makes up 80% of the sediment in the Indian and Pacific Oceans. Clinoptilolite is abundant in Atlantic sediments and both phillipsite and clinoptilolite are found in manganese nodules on the ocean beds. 

G. oceanica, the other known alkenone-synthesizing species of importance, has a more limited oceanic distribution. G. oceanica apparently does not occur in waters colder than —12 °C (Okada and McIntyre, 1979). It commonly occurs in tropical and subtropical waters, in particular, the high fertility regions of the eastern Pacific and... 

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