1 |
edhill |
1.1 |
\section {DIC Package} |
2 |
edhill |
1.2 |
\label{sec:pkg:dic} |
3 |
|
|
\begin{rawhtml} |
4 |
|
|
<!-- CMIREDIR:package_dic: --> |
5 |
|
|
\end{rawhtml} |
6 |
edhill |
1.1 |
|
7 |
|
|
\subsection {Introduction} |
8 |
|
|
This is one of the biogeochemical packages handled from the |
9 |
|
|
pkg gchem. The main purpose of this package is to consider |
10 |
|
|
the cycling of carbon in the ocean. It also looks at the |
11 |
|
|
cycling of phosphorous and oxygen. There are five tracers |
12 |
|
|
$DIC$, $ALK$, $PO4$, $DOP$ and $O2$. The air-sea exchange |
13 |
|
|
of CO$_2$ and O$_2$ are handled as in the OCMIP experiments |
14 |
|
|
(reference). The export of biological matter is computed |
15 |
|
|
as a function of available light and PO$_4$. This export is |
16 |
|
|
remineralized at depth according to a Martin curve (again, |
17 |
|
|
this is the same as in the OCMIP experiments). There is |
18 |
|
|
also a representation of the carbonate flux handled as in |
19 |
|
|
the OCMIP experiments. The air-sea exchange on CO$_2$ |
20 |
|
|
is affected by temperature, salinity and the pH of the |
21 |
|
|
surface waters. The pH is determined following the |
22 |
|
|
method of Follows et al. |
23 |
|
|
|
24 |
|
|
\subsection {Key subroutines and parameters} |
25 |
|
|
|
26 |
|
|
\noindent |
27 |
|
|
{{\bf INITIALIZATION}} \\ |
28 |
|
|
{\it DIC\_ABIOTIC.h} contains the common block for the |
29 |
|
|
parameters and fields needed to calculate the air-sea |
30 |
|
|
flux of $CO_2$ and $O_2$. The fixed parameters are set in |
31 |
|
|
{\it dic\_abiotic\_param} which is called from {\it gchem\_init\_fixed.F}. |
32 |
|
|
The parameters needed for the biotic part of the calculations |
33 |
|
|
are initialized in {\it dic\_biotic\_param} and are stored |
34 |
|
|
in {\it DIC\_BIOTIC.h}. The first guess of pH is calculated |
35 |
|
|
in {\it dic\_surfforcing\_init.F}. |
36 |
|
|
|
37 |
|
|
\vspace{.5cm} |
38 |
|
|
|
39 |
|
|
\noindent |
40 |
|
|
{{\bf LOADING FIELDS}}\\ |
41 |
|
|
The air-sea exchange of $CO_2$ and $O_2$ need wind, atmospheric |
42 |
|
|
pressure (although the current version has this hardwired to 1), |
43 |
|
|
and sea-ice coverage. The calculation of pH needs silica fields. |
44 |
|
|
These fields are read in in {\it dic\_fields\_load.F}. These |
45 |
|
|
fields are initialized to zero in {\it dic\_ini\_forcing.F}. |
46 |
|
|
The fields for interpolating are in common block in |
47 |
|
|
{\it DIC\_LOAD.h}. |
48 |
|
|
|
49 |
|
|
\vspace{.5cm} |
50 |
|
|
|
51 |
|
|
\noindent |
52 |
|
|
{{\bf FORCING}}\\ |
53 |
|
|
The tracers are advected-diffused in {\it ptracers\_integrate.F}. |
54 |
|
|
The updated tracers are passed to {\it dic\_biotic\_forcing.F} |
55 |
|
|
where the effects of the air-sea exchange and biological |
56 |
|
|
activity and remineralization are calculated and the tracers |
57 |
|
|
are updated for a second time. Below we discuss the |
58 |
|
|
subroutines called from {\it dic\_biotic\_forcing.F}. |
59 |
|
|
|
60 |
|
|
|
61 |
|
|
Air-sea exchange of $CO_2$ is calculated in {\it dic\_surfforcing}. |
62 |
|
|
Air-Sea Exchange of $CO_2$ depends on T,S and pH. The determination |
63 |
|
|
of pH is done in {\it carbon\_chem.F}. There are three subroutines |
64 |
|
|
in this file: {\it carbon\_coeffs} which determines the coefficients |
65 |
|
|
for the carbon chemistry equations; {\it calc\_pco2} which calculates |
66 |
|
|
the pH using a Newton-Raphson method; and {\it calc\_pco2\_approx} |
67 |
|
|
which uses the much more efficient method of Follows et al. |
68 |
|
|
The latter is hard-wired into this package, the former is kept |
69 |
|
|
here for completeness. |
70 |
|
|
|
71 |
|
|
Biological productivity is determined following |
72 |
|
|
McKinely et al. and is calculated in {\it bio\_export.F} |
73 |
|
|
The light in each latitude band is calculate in {\it insol.F}. |
74 |
|
|
The formation of hard tissue (carbonate) is linked to |
75 |
|
|
the biological productivity and has an effect on the |
76 |
|
|
alkalinity - the flux of carbonate is calculated in |
77 |
|
|
{\it car\_flux.F}. The flux of phosphate to depth where |
78 |
|
|
it instantly remineralized is calculated in {\it phos\_flux.F}. |
79 |
|
|
|
80 |
|
|
Alkalinity tendency comes from changes to the salinity from |
81 |
|
|
addition/subtraction of freshwater in the surface. This |
82 |
|
|
is handled in {\it alk\_surfforcing.F}. |
83 |
|
|
|
84 |
|
|
Oxygen air-sea exchange is calculated in {\it o2\_surfforcing.F}. |
85 |
|
|
|
86 |
|
|
\vspace{.5cm} |
87 |
|
|
|
88 |
|
|
\noindent |
89 |
|
|
{{\bf DIAGNOSTICS}}\\ |
90 |
|
|
Averages of air-sea exchanges, biological productivity, |
91 |
|
|
carbonate activity and pH are calculated. These are |
92 |
|
|
initialized to zero in {\it dic\_biotic\_init} and |
93 |
|
|
are stored in common block in {\it DIC\_BIOTIC.h}. |
94 |
|
|
|
95 |
|
|
\subsection{Do's and Don'ts} |
96 |
|
|
|
97 |
|
|
This package must be run with both ptracers and gchem enabled. |
98 |
|
|
It is set up for 5 tracers, but there is the provision of |
99 |
|
|
a 6th tracer (iron) that is not discussed here. |
100 |
|
|
|
101 |
|
|
\subsection{Reference Material} |
102 |
|
|
|