Secular change

Abouchami W, Goldstein SL, Galer SJG, Eisenhauer A, Mangini A (1997) Secular changes of lead and neodymium in central Pacific seawater recorded by a Fe-Mn crast. Geochim Cosmochim Acta 61(18) 3957-3974... 

One implication of Earth - degassing models of metallogenesis is that there should be links between the formation of the Earth s resources, secular changes in architecture and geochemistry of the planet over some 4.5 billion years of evolution and phenomena such as mass extinction events, global anoxia, and atmospheric evolution. 

The second direction is connected with numerical modeling of climate change on a scale of decades and longer (in particular, with an explanation of the secular change in global annual mean SAT). Apparently, in the case of long-term climatic variability the influence of stochastic forcing (ISF) can be considered a zero hypothesis. 

Saltzman E.S., Lindh T.B. and Holser W.T. (1982) Secular changes in 813C and 834S, global sedimentation, P02 and PCO2 during the Phanerozoic. Geol. Soc. Amer. Abstr. 14, 607. 

Heath D.F., Secular changes in atmospheric ozone from satellite observations 1970-1979), presented at WMO-NASA meeting in Hampton, Virginia, May, 1981. 

Kohlmaier G., Revelle R. and Keeling C. D., Secular changes in the amplitude of the seasonal swings in atmospheric CO2 concentration. Report to the Department of Energy (1983). 

Mahva, R., Knoll, A., and Siever, R. (1989). Secular change in Chert distrihution A reflection of evolving biological participation in the sihca cycle. Palaios 4, 519—532. 

Wider R., Kehm K., Meshik A. P., and Hohenberg C. M. (1996) Secular changes in the xenon and krypton abundances in the solar wind recorded in single lunar grains. Nature 384, 46-49. 

Martin H. and Moyen J.-F. (2002) Secular changes in tonalite-trondhjemite-granodiorite compositions as markers of the progressive cooling of the Earth. Geology 30, 319-322. 

The principal sources of sulfate in formation waters are dissolved marine sulfate, sulfate derived from the dissolution of evaporites, and sulfate formed by the oxidation of sulfides. Sulfate is destroyed by reduction to hydrogen sulfide. The value of 5 " S in gypsum is only — 1.6%o heavier than sulfate in solutions from which it precipitates. The isotopic composition of sulfur in gypsum in Phanerozoic deposits precipitated from seawater during evaporation thus tracks the secular changes in the isotopic composition of sulfur in seawater ( 10% to 30%o). 

Cicero A. D. and Lohmann K. C. (2001) Sr/Mg variation during rock-water interaction implications for secular changes in the elemental chemistry of ancient seawater. Geochim. Cosmochim. Acta 65, 741—761. 

It is therefore difficult to gauge the current direction of secular change of mercury in the atmosphere. However, as suggested, it may be that the reduced emissions from relatively uncontrolled sources in Eastern Europe, for example, will be more than made up for by increased emissions associated with developing economies such as China. 

Secular change in the global mercury cycle as a result of human activity is one of the major themes in this chapter and a focus of research currently. One of the most insightful research activities in pursuit of this theme has been the development of historical archives of mercury change. As of early 2000s, this development effort has focused on three archives peat bogs, lake sediments, and ice cores. All are used to reconstmct historical changes in the flux of mercury from the atmosphere. 

Seabird feathers may provide a proxy for oceanic mercury secular change (Monteiro and Furness, 1997). This unique dataset includes feathers retrieved from museum specimens of exclusively pelagic, piscivorous seabirds such as shearwaters and petrels. While there is scatter associated with the values, as should be expected from such a natural archive, an increase of —3 X between 1885 and 1994 can be seen in the mercury concentration of the feathers. Furness, Monteiro and co-workers have extended their work to include studies on the movement of mercury within hving birds and the relationship between prey concentrations of mercury and those observed in the bird s feathers (Monteiro et al., 1998 Monteiro and Furness, 2001), which aid in the interpretation of the feather record. This approach has so far been apphed to the NE... 

Fig. 6. Global surface temperature and PCO2 histories for two otherwise identical models with high and low heat flows. The models assume a current mid-ocean ridge flux Fridge = 2 x 10 moles a". The low heat-flow models feature relatively little secular change in the oceanic crustal creation rate and the continental metamorphic recycling rate.

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