Cosmogenic isotopes oceanic sources

The production rates of several cosmogenic isotopes in the earth s atmosphere are given in Table 2, along with their estimated global inventories. Some of the cosmogenic isotopes are also produced directly, in situ, in the upper layers of the oceans. The source strengths of cosmic ray-produced nuclei in the oceans, due to their production in the atmosphere, and direct production in the ocean water, are given in... 

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. 

As apparent from the properties listed in Table 1, ocean chemists have a variety of tracers at hand, covering a range of residence times and chemical behaviors. Those tracers varying due to radioactive decay have distinct isotopic compositions in their various source materials (Table 2). This makes them particularly useful both as water mass tracers, and to reconstruct the flux from these various sources into the oceans. It may be surprising to And the cosmogenic nuclide °Be in this list of otherwise radiogenic tracers. The reason is that Be behaves very similarly to the other tracers in that the ratio °Be/ Be is distinct in different water masses. Given that °Be is the only tracer of which the flux into the oceans is known, t can be calculated precisely from its water column concentration. Further, the continent-derived isotope Be is the only tracer of which the flux into the oceans can be calculated from the °Be/ Be ratio. 

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