Geoscience Reference
In-Depth Information
The concentration of nutrients B
6,A
(t,
φ
,
ʻ
,z) at the depth z is determined by
photosynthesis R
pA
, advection and destruction of suspended dead organic matter B
7
.
The role of the hydrodynamic conditions manifests itself in maintenance of the
concentration of nutrients required for photosynthesis which occurs via transport
from other layers or aquatories of the sea where the concentration is suf
ciently
high. Taking into account the designations of Table
6.5
we have:
<
E
0
ð
t,
u; kÞ
when z
ð
g
þ
r
Þ;
E
0
exp
a
g
z
when z
2ð
g
þ
r
Þ;
r
ð
; u; k;
Þ
¼
1
b
g
½
;
E
g
t
z
Et
ð
; u; k;
z
Þ
¼
E
r
t
ð
; u; k;
z
Þ
¼ 1
b
r
ð
Þ
E
g
ð
t,
u; k;
r
Þ
exp
a
r
ðÞ
when z
2
r
½
;
0
;
E
r
t
; u; k;
0
when z
2
0
;
f
:
E
f
ð
t
; u; k;
z
Þ
¼ 1
b
f
ð
Þ
exp
a
f
z
½
;
E
w
t
; u; k;
z
ð
Þ
¼ 1
b
w
ð
Þ
Et
; u; k;
f
ð
Þ
exp
a
w
z
ð
Þ
when z
[
f
:
where the values of
ʱ
A
(A = g, r, f, w) depend on the optical properties of the Ath
medium. The irradiance E
0
arrives at the surface
. The estimate of E
0
is obtained
from monitoring or is calculated from the climatic model. The
Ω
flow of E
0
is
attenuated by snow, ice and water according to the scheme of Table
6.5
. In each cell
Ω
ij
the structure of these layers is changed corresponding to the time of year. Within
each layer, the attenuation of the irradiance with depth is described by an expo-
nential model. The parameters
fl
ʲ
A
are functions of the salinity, turbidity,
temperature, and biomass. The form of this dependence is given as a scenario or
else the standard functions are used (block IM).
Block-diagram of Fig.
6.6
is realized as block MEF. The boxes with elements
denote the generalized trophic levels of the arctic ecosystem. All of the elements are
described by means of averaged parameters for the biological community of the
north seas. It is supposed that this trophic pyramid takes place in each of the Arctic
Basin seas. The trophic relations between the elements of the model are described
on the basis of the energetic principle (Nitu et al. 2000b). Biomasses, the rates of
production and exchange (respiration), and food rations are expressed in energy
units. Total nitrogen serves as a
ʱ
A
and
“
nutrient salts
”
prototype in the model.
flow of nutrients in the water, the scheme proposed by
Krapivin (1996) is accepted as corrected for the conditions of the Arctic Basin by
Legendre and Legendre (1998). It is supposed that the spatial distribution of
upwelling zones is given with seasonal variations. Block NM realizes this scheme
in reference to the current structure of the upwelling regions.
The dynamic equation for the nutrients B
6,A
in the environment, where A ={S
As a basic scheme for the
fl
—
snow, I
—
ice, W
—
water}, is given by
2
B
6
;
A
@
@
B
6
;
A
u
@
B
6
;
A
@u
k
@
B
6
;
A
@k
þ
v
z
@
B
6
;
A
@
z
¼ Q
A
þ
k
2
@
2
z
þ b
V
@
B
6
;
A
@
z
@
t
þ
v
A
þ
v
A
ð
6
:
2
Þ
þ q
1
X
5
A
1
H
1
T
i
d
R
pA
þ e
i¼1
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