[Eoas-seminar] EOAS Colloquium Friday Sept 7

eoas-seminar at lists.fsu.edu eoas-seminar at lists.fsu.edu
Fri Aug 31 16:32:04 EDT 2018

Dr. William Landing will be giving our next EOAS Seminar on Friday Sept 
7 at 3:30 pm in CAR 101.
We look forward to seeing you there!

*Atmospheric Deposition to the Oceans Controls Biological Productivity*


The atmospheric flux of trace elements and isotopes (TEIs) to the oceans 
can be extremely important in marine biogeochemical cycles, especially 
for bioactive trace elements. This includes many trace elements and 
isotopes of interest to the GEOTRACES program such as Al, V, Mn, Fe, Co, 
Ni, Cu, Zn, Cd, Pb, and others. However, there are large uncertainties 
associated with converting aerosol TEI concentrations into atmospheric 
deposition fluxes. We need to use an aerosol tracer whose atmospheric 
deposition can be tracked as a function of time. Following production by 
cosmic-ray spallation, tropospheric Be-7 (half-life 53.3d) quickly 
attaches to aerosols and is deposited to the oceans by wet and dry 
deposition. Due to its radioactive decay, the inventory of Be-7 in the 
upper ocean is balanced by its flux from the atmosphere. The ability to 
derive the atmospheric flux of Be-7 from its ocean inventory provides a 
key linkage between the atmospheric concentrations of chemical species 
and their deposition to the ocean. By measuring upper ocean inventories 
and aerosol concentrations of Be-7, we can derive a “bulk deposition 
velocity” that accounts for both wet and dry deposition. The bulk 
deposition velocities can then be applied to any other aerosol species 
to calculate its flux. Where the fractional solubility of aerosol TEIs 
has been measured, the bulk deposition velocities can be used to 
calculate the atmospheric flux of soluble TEIs. This is especially 
useful for estimating the impact of atmospheric deposition on biological 
productivity since soluble TEIs are expected to be intrinsically 
bioavailable to phytoplankton. We will present results from field 
campaigns in the Sargasso Sea (Bermuda) and the Arctic Ocean to test 
this approach.

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