MOdel Shopping Tool ( MOST )
"CaCO3 (calcium carbonate) budget module" from PISCES v1 Equations
Equation Description :
In PISCES, calcium carbonate is supposed to be only in the form of calcite. Thus, aragonite is not considered, for instance, for the computation of the chemical dissolution in the water column.
Calcite budget is controlled by the rain ratio of calcifying phytoplankton, R CaCO3, fecal pellet production by microzooplankton (Z) and mesozooplankton (M), calcifiers mortality, minus calcite dissolution and particulate organic carbon settling (POCb).
The rain ratio, R CaCO3, is variable. The proportion of calcifying phytoplankton is generally very low in oligotrophic regions. When the nanophytoplankton blooms, the dominant species are often calcifiers. To mimic these very general considerations, the rain ratio varies between 0.01 and 0.8 using the parameterization of Moore et al. (2002) as shown above.
Only half of the grazed shells is routed to sinking calcite. The rest is supposed to dissolve in the acidic guts of zooplankton (Jansen and Wolf-Gladrow, 2001). This dissolution is still debated. However, observations tend to show that a significant proportion of the sinking shells is lost in the upper ocean, whether during grazing or by other mechanisms (Milliman et al., 1999).
The dissolution rate constant is defined following Maier-Reimer (1993), i.e. dissolution increases with the undersaturation level, and no dissolution is allowed in case of over-saturation.
Parameter definitions and values:
lambda* CaCO3 = calcite dissolution rate;
sigma = 0.3 no units (fecal pellets production);
g = 4, 0.7 d -1 (max grazing rate for micro- and mesozooplankton);
K CaCO3 = ? micro mol C l-1 (half-saturation constant for calcite);
K P = 0.1 micro mol C l-1 (half-saturation constant for mortality);
M = concentration of mesozooplankton in micro mol C l-1;
m P = 0.01 d-1 (phytoplankton mortality rate);
P = concentration of nanophytoplankton in micro mol C l-1;
R CaCO3 = rain ratio of calcifiers, variable from 0.01 to 0.8 depending on nanophytoplankton concentration;
T = in situ temperature in °C;
w POC = sinking speed of large POC (m d-1);
w P = 0.01 d-1 molC-1 (quadratic phytoplankton mortality);
Z = concentration of microzooplankton in micro mol C l-1;
References:
Jansen, H., and D. A.Wolf-Gladrow 2001. Mar. Ecol. Prog. Ser., 221, 199-207;
Maier-Reimer, E. 1993. Global Biogeochem. Cycles, 7, 645677;
Milliman, J. D., et al 1999. Deep Sea Res. Part I, 46, 1653-1669;
Moore, J. K., et al 2002. Deep Sea Res. Part II, 49, 403-462;
