Impact of ocean acidification on pelagic calcification

1
Impact of ocean acidification on pelagic
calcification
(Gehlen and Schneider, CARBOOCEAN 511176 (GOCE),
deliverable 16.4, unpublished results)
2

• The slide shows results of a model simulation
  (PISCES/NEMO) where marine pelagic calcification
  is dependent on the saturation state (O) of
  seawater with respect to the CaCO3 polymorph
  calcite. With increasing CO2 uptake by the ocean
  (acidification) the saturation state decreases.
  When O is larger than 1 the water is
  supersaturated, and for O between 0 and 1 the
  water is undersaturated, the latter being a
  prerequisite for pelagic CaCO3 dissolution.
• Upper left
• Atmospheric CO2 concentrations are prescribed to
  increase from preindustrial values of 286 ppm
  (1xCO2) to four times the preindustrial value
  (1153 ppm, 4xCO2). This is realized by a 1
  increase each year over a time period of 140
  years. The full black line shows the prescribed
  atmospheric CO2 concentration in the scenario
  run, the dashed line is the control experiment,
  where CO2 is kept constant on the preindustrial
  value.
• Upper middle
• Global annual integrals of pelagic calcite
  production (black) and export flux (red) in
  gigatons carbon per year. Export is the amount of
  CaCO3 that falls through the 100m depth level.
  Both rates are decreasing by about 25 .
• Upper right
• Mean value for the saturation state of seawater
  with respect to calcite (O) for the top 0-100m of
  the water column. O is rapidly decreasing from
  about 5 to 2.
• Bottom
• Map of O for the top 0-100m of the water column
  at 1xCO2 (left) and 4xCO2 (right).
• Left green (and blue) areas mark those areas
  where Ogt4 (see also contour line), which is an
  important threshold value for calcification of
  coral reefs (not taken into account in this
  study)
• Right O is lower than 4 everywhere and in some
  high latitude areas even undersaturation Olt1 (see
  contour line) occurs.