Ocean pumping of DOC

With a voice like Sean Connery, Professor Emeritus. Dr. Calvin of the UW School of Medicine (new book at http://williamcalvin.org )  talked about his ideas for how to mitigate rising CO2 levels.  His concerns arise in part from the 2-3x increase in the global drought index during the 20th century (Das et al., 2004; updated 2006).  He also noticed that around 1976 El Nino conditions began to predominate, though La Nina conditions were dominant beforehand.

In addition to more prevalent abrupt climate shifts, there were some near misses (like heart attacks?) since 1976:

  1. 1998 El Nino lasting longer
  2. 2005 Amazonia drought
  3. Antarctic flushing failure
  4. Labrador sea flushing failure

We need to sequester about 600 Gt of carbon over next 20 years to get back to pre-industrial levels.  Freeman Dyson’s favorite fix is doubling global forests, but climate conditions are getting worse for trees generally.  Photosynthesis already removes 210 GtC/yr, though it is mostly returned through respiration and decomposition.  This means we need new production that is sequestered for long time periods (probably best done in the voluminous oceans).

Much of the anthropogenic CO2 that has already been sunk is in the N Atlantic.  Major inputs are 2GtC/yr from deforestation and 8 from fossil fuels and cement.  92 are absorbed into ocean, and 90 are released.  In ocean 48 are photosynthesized, 37 are respired, and 11 settle through thermocline, and 0.01 are deposited on bottom.  So the big reservoir is dissolved organic carbon; it is 100x larger than the living biomass.

In the cold depths, about 1/2 of new DOC from upper ocean is soon converted into total CO2.  The rest has a 6kyr residence time (maybe because of multiple passes through surface system before removal).

Intervention A:  4x the settling rate (11 -> 44), but that would require a 4x increase in global productivity.

Intervention B: Pump down 30GtC/yr (600Gt over 20 years) maybe by fertilizing near downwelling zones (Greenland Sea whirl pools?) OR by mechanical pumping with wind or wave power.

Algaculture has advantage of controlling respiration.  Assume 50g of algae/m2/d about half of which is carbon.  Thus it takes 10-4 m2 (fingernail) to grow 1 gC/yr.  To sink 30Gt, you’d need 3×10^9 m2 or 3000 km2.

Field trials?  3,900 oil and gas platforms are in operation off coasts of Louisiana and Texas.  The north Sea presents a similar opportunity.

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