Ocean Circulation, Iron and Carbon Cycles during the Last Glacial Maximum

MUGLIA, JUAN; SCHMITTNER, ANDREAS

Conferencia; 12th International Conference on Paleoceanography; 2016

PAGES-SCOR-PAIS-University of Utrecht-NESSC

In  this  work  we  study  changes  in  the  ocean  circulation  and  carbon  cycle  that  could  explain reconstructed  concentrations  of  atmospheric  CO2  and  nitrogen  and  carbon  isotope  distributions  for the  Last  Glacial  Maximum  (LGM).  We  evaluate  the  effect  of  preindustrial-to-LGM  changes  in  iron solubility,  ligand  concentration,  dust  flux  into  the  ocean,  and  sedimentary  iron  flux  on  the  ocean component  of  an  isotope  enabled  biogeochemical  model,  coupled  with  a  global  ocean  circulation model.  These  changes  are then  combined  with sedimentary  reconstructions  or  nitrogen  and  carbon isotopes to evaluate effects on the carbon cycle of the LGM. We find that higher dust fluxes into the ocean  in  the  LGM  increase  productivity  and  enhance  the  biological  pump,  trapping  carbon  in  deep waters.However, the effect is countered by changes in sedimentary release of iron due to lower sea level, and its significance depends on the assumed solubility of iron in dust.Effects of circulation changes are also evaluated. We produce LGM simulations with different ocean circulation  states.  An  ocean  with  shallow  North  Atlantic  Deep  Water  and  high  penetration  of Antarctic  Bottom  Water  into  the  northern  hemisphere  preserves  more  deep  dissolved  carbon,  and has  isotope  distributions  more  similar  to  reconstructions  than  an  ocean  with  deep  and  fast  Atlantic Meridional Overturning Circulation.