Deep-water enrichment

The nutrient profiles are characterized by much higher concentrations in the deep-waters than in the surface. In some locations, such as shown in Figure 9.1, mid-water concentration maxima are present. The depth region over which concentrations exhibit the largest vertical gradients is usually defined by the thermocline. All biolimiting elements have similar depth profiles, having surfece-water depletions and deep-water enrichments. 

The vertical distribution of biolimiting elements is characterized by deep-water enrichments and surface-water depletions. As described above, this vertical segregation is caused by the remineralization of biogenic particles in the deep sea. Not all particulate matter that sinks into the deep zone is remineralized. Some survives to become buried in the sediments. How much of the biogenic particle flux escapes from surfece waters How much of this particle flux is remineralized in the deep zone How much is lost from the ocean by burial in the sediments What effect does this have on the concentrations of the biolimiting elements ... 

These dissolved constituents of seawater have concentration versus depth profiles characterized by surface water depletion and deep water enrichment caused by plant consumption in the euphotic zone and release at depth when the biological material dies, sinks and degrades. Examples of these elements are nutrients required for ph5d oplankton growth (P, NO3 and HCO3), oxygen consumed during... 

Walter HJ, Geibert W, Rutgers van der Loeff MM, Fischer G, Bathman U (2001) Shallow vs. deep-water scavenging of Pa and °Th in radionuclide enriched waters of the Atlantic sector of the Southern Ocean. Deep-Sea Res 148 471-493... 

The aqueous chemistry of Ra is expected to be very similar to that of Ba. Thermodynamically driven Ra enrichments in celestite and barite are expected based on Sr/Ba/Ra coprecipitation systematics (Bernstein et al., 1998). Ra concentrations in the water column should reflect such processes to some degree. Significant differences in Ba and Ra distributions in seawater should be attributable to differences in the sources of these elements. 226Ra is the daughter of 230Th with resulting strong sources in deep water and sediments. 

The increasing concentrations of neodymium with depth indicate that neodymium is added to deep water as water masses laterally advect in the Atlantic, however, the neodymium that enriches deep waters along the advective path in the Atlantic has isotope ratios expected for the respective water masses. The isotope ratios appear... 

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