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The purpose of this paper is to provide an overview of paleoceanography and paleoclimatology as a framework for other papers dealing with The Earth System: Geochemical Perspectives. An introduction to both paleoceanography and paleoclimatology is followed by examples of the temporal changes through the Phanerozoic. The important and interactive role of the biosphere is emphasized. Many important changes in the Earth system have affected the coupled ocean–atmosphere system and many, in turn, have been reflected in biotic events. Many such changes can be tracked through time using geochemical signatures as proxy indicators. Whereas the scale of past paleoceanographic and paleoclimatic changes have been generally appreciated for some time, the recognition of periodic rapid change in the ocean/climate state and the ability to study and measure these precisely is only a recent accomplishment. The potential for such rapid change in the ocean/climate/biosphere of the Earth system raises concerns for events in the near future that may be forced by anthropogenic activities that enhance natural variability.

The paper discusses and compares application of several stochastic and deterministic methods for analysis of geological time-series, taking the δ18Orecord of the Pacific core V28-239 as a test object. The stochastic techniques include finite parameter linear models, such as ARMA and ARIMA, while the deterministic chaos approach deals with the Lyapunov exponent and correlation dimension, utilizing the Wolf algorithm and the Grassberger–Procaccia procedure, respectively. Neither stochastic nor deterministic models lead to definitive and unique conclusions. This is true for our results as well as for those of the previous authors obtained on the same dataset. The major limitations are the small size of the sample set and the uncertainties in assigned ages for the δ18Ovalues. It may be that the emerging nonlinear stochastic techniques prove to be more suitable for treatment of geological time-series.

In this paper we investigate the presence of chaos in the system that underlies the Phanerozoic 87Sr/86Srisotope record of seawater carbonates by means of nonlinear time series analysis. The Fourier power spectrum estimation from the original time series together with the geological conjecture that the system is controlled only by a few (2 to 4) degrees of freedom point to an underlying chaotic system. The zero-order, correlation dimension and the largest Lyapunov exponent methods are employed to prove or to reject this assumption. Inherent problems of the data sets (non-equidistant and too sparse for a reliable application of these techniques) and the inability of the currently available methods to cope with them do not yet allow for a clear-cut decision.

This paper investigates the chemical variations and evolution of Lake Kinneret (LK), the Sea of Galilee after the diversion of onshore saline springs through the Salinity Diversion Channel (SDC) which reduced the salinity of the lake water. The mass-balance approach enables to determine the average chemical composition of the unknown internal lake sources of salinity that in addition to other known sources, contribute salts and control the chemistry of the lake water. This study reveals, for the first time, the average chemical composition of the internal lake salinity sources. Mass balances show that the water discharge of the lake internal sources is 61×106m3year−1and that these sources contribute 72,000 tons of chloride, annually. The SDC operation caused a long term decrease in the concentrations of Cl, Mg, Na, K, Ca, SO4and Br in lake water. Concomitantly, the ionic ratios of Na/Cl, Mg/Cl. Ca/Cl, K/Cl and SO4/Cl have increased and Br/Cl ratio has decreased. The average chemical composition of the lake internal sources, is characterized by Na/Cl and Mg/Cl ionic ratios which closely resemble those measured in the two well known submerged saline springs, of Fulyia a and Fulyia b, and in water of a deep observation well, located north of the lake (referred to as KIN-8). The decrease in Br/Cl ionic ratio from ≥3.58×10−3prior to the SDC operation, to 3.29(±0.11)×10−3in mid 1990s implies that the major internal sources of Cl and Br to the lake are characterized by Br/Cl ratios ≤3.29×10−3. Br/Cl ionic ratios somewhat lower than 3.29×10−3were found only in Fulyia a and Fulyia b springs and in KIN-8 water. It is therefore suggested that Fulyia like water is the internal saline source which supplies most of the Na, Cl and Br to the lake. Sulphate, however, is contributed to the lake mainly (over 80%) through freshwater streams. Calcium and alkalinity originate mainly from freshwater sources, including internal lake flow of groundwater, lower in salinity but saturated with CaCO3. Thus, internal sources of solutes are mostly composed of the saline end member of Fulyia like water and of fresher groundwater. These conclusions have practical implications for lake water management.

When seawater circulates through hot basalt at active spreading centers, the manganese concentration of the seawater increases by ∼ 106times. Eventually, this hydrothermal water is discharged back into ambient seawater through vents and fissures on the sea floor. Mn vs. silica relationships in water samples collected from active vent fields on the Galapagos Rift are linear but have different slopes. These relationships demonstrate that the Mn in the hydrothermal end-member mixes conservatively with ambient seawater (at least below 10°C) but the physical and chemical processes responsible for the Mn concentration of the hydrothermal fluid must be variable. The Mn concentrations measured for the Galapagos system predict that hydrothermal emanations are major sources of Mn to the oceans but only if these data are not anomalously high. This paper presents profiles of Mn in bottom waters at four locations along the East Pacific Rise (EPR) which support the hypothesis that Mn emanations comparable to those from the Galapagos are occurring along the EPR. Bottom water at one station in the Guatemala Basin, some 1000 km from the EPR crest, also has anomalously high Mn concentrations suggesting that this hydrothermal Mn signal can be transported far from the source.