Oceans circulation, oceanic marine

We begin the book with a brief discussion of background information about the chemical constituents of seawater, the basics of ocean circulation and marine biological processes. Some important information about the volumes and areas of the ocean and atmosphere are presented in Table 1.1. The goal of this chapter is to create a foundation for the discussion of mechanisms later in the book. 

Joly observed elevated "Ra activities in deep-sea sediments that he attributed to water column scavenging and removal processes. This hypothesis was later challenged with the hrst seawater °Th measurements (parent of "Ra), and these new results conhrmed that radium was instead actively migrating across the marine sediment-water interface. This seabed source stimulated much activity to use radium as a tracer for ocean circulation. Unfortunately, the utility of Ra as a deep ocean circulation tracer never came to full fruition as biological cycling has been repeatedly shown to have a strong and unpredictable effect on the vertical distribution of this isotope. 

Ocean prevents eutrophication. Much more water flows into the Mediterranean Sea than is required to replace evaporation from it. The excess, high salinity water exits Gibraltar below the water flowing in af fhe surface. Nufrients that enter the Mediterranean Sea from pollution sources are utilized by marine phytoplankton that sinks and exits with the outflow. Another example is that estuaries often have lower salinity or even freshwater at the surface with a denser saline layer at the bottom. An estuarine circulation occurs with nutrients being trapped in the saline bottom water. 

Nozaki Y, Yamada M, Nikaido H (1990) The marine geochemistry of actinium-227 evidence for its migration through sediment pore water. Geophys Res Lett 17 1933-1936 Nozaki Y (1993) Actinium-227 a steady state tracer for the deep-se basin wide circulation and mixing studes. In Deep Ocean Circulation, Physical and Chemical Aspects. Teramoto T (ed) Elsevier p 139-155... 

The geochemistry of marine sediments is a major source of information about the past environment. Of the many measurements that provide such information, those of the U-series nuclides are unusual in that they inform us about the rate and timescales of processes. Oceanic processes such as sedimentation, productivity, and circulation, typically occur on timescales too short to be assessed using parent-daughter isotope systems such as Rb-Sr or Sm-Nd. So the only radioactive clocks that we can turn to are those provided by cosmogenic nuclides (principally or the U-series nuclides. This makes the U-series nuclides powerful allies in the quest to understand the past ocean-climate system and has led to their widespread application over the last decade. 

Yu E-F, Francois R, Bacon M (1996) Similar rates of modem and last-glacial ocean thermohaline circulation inferred from radiochemical data. Nature 379 689-694 Zheng Y, Anderson RF, van Geen A, Fleisher MQ (2002) Preservation of particulate non-lithogenic uranium in marine sediments. Geochim Cosmochim Acta 66(17) 3085-3092. 

The research published in this book uses the presently most comprehensive multicompartment model, the first which comprises a coupled atmosphere-ocean general circulation model (GCM). GCMs are the state-of-the-art tools used in climate research. The study is on the marine and total environmental distribution and fate of two chemicals, an obsolete pesticide (DDT) and an emerging contaminant (perflu-orinated compound) and contains the first description of a whole historic cycle of an anthropogenic substance, i.e. from the introduction into the environment until its fading beyond phase-out. 

Distributions of DOC in the deep ocean. The x-axis is viewed in the context of the deep-ocean circulation, with formation in the North Atlantic, circulation around the Southern Ocean, and flow northward into the Indian and Pacific oceans. Source-. From Mansell, D. A. (2002) Biogeochemistry of Marine Dissoived Organic Matter, Academic Press, pp. 685-715. 

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