4
IN03
Barents Sea
Scotia Sea
Table 2. Characteristic nutrient
before
after
before
after
levels (]JM) before and after the
9-14
~O
32
12
first bloom in Arctic and Antarctic
NH4
0-2
0-2
0-2
0-4
waters.
(t.) denotes the ratio for
P04
0.5-0.6 ~ 0.1
1.9
0.9
the decrease in nutrients during a
Si02
4-5
~O
102
44
bloom. Data from Ellertsen et al.
(1981 ) and Biggs et al. (1982)
N03/P04
17-23
17-23 (t.)
17
20 (ll)
N03/Si02
25-28 2.0-2.8(1l) 0.31
0.34 (t.)
instance in midsummer from 58 0 at 55 0 lat. to 23 0 at the poles. Coincidentally diurnal rhythms become attenuated. This is clearly reflected
in the diurnal variation in global radiation on a clear summer day (Fig.
3). Daily integrals will not differ much for clear days, when comparing
different places in summertime. Weather patterns do, however, influence
the global radiation considerably. Close to the Antarctic continent
where high pressures prevail, the weather is often lightly cloudy or
sunny, whereas the West Wind Drift is characterized by the continuous
passage of low pressures and hence, dominance of cloudy weather. Thus
the global radiation may be higher close to the continent than in the
West Wind Drift (Holm-Hansen et al. 1977). In the Arctic summer fog
and cloudy weather often prevails, but the variability is high. The
monthly average global radiation is hardly more than 20-40% of that of
clear days in that area (Spinnangr 1968).
"
70'
800
"
"
60'
600
so'
15
40'
N
E 400
;i:
JAN
MAR
MAY
JUL
SEP
I'.QV.
5 hemisph
JUL
SEP
NOV
JAN
MAR
MAY
N hemisph
MONTH
Fig. 2. Seasonal variation in day
length at various latitudes. Data
from Holm-Hansen et al. (1977) and
Spinnangr' (1968)
200
12
16
20
2'
hr.
Fig. 3. Diurnal variation in global radiation on clear midsummer days at Troms~
(700 N) and Ny-Alesund, Svalbard (79 0 N)
Submarine light measurements also reflect extreme seasonal variation at high latitudes.
In the Trondheimsfjord, Norway (630 N), measurements with a spherical collector at 0.5m depth indicated that the
peak photon flux density (aver. for the two brightest hours of the day)
ranged from 30 ]JE m- 2 s- 1 in December to 1500 ]JE m- 2 s- 1 in June (Hegseth
IN03
Barents Sea
Scotia Sea
Table 2. Characteristic nutrient
before
after
before
after
levels (]JM) before and after the
9-14
~O
32
12
first bloom in Arctic and Antarctic
NH4
0-2
0-2
0-2
0-4
waters.
(t.) denotes the ratio for
P04
0.5-0.6 ~ 0.1
1.9
0.9
the decrease in nutrients during a
Si02
4-5
~O
102
44
bloom. Data from Ellertsen et al.
(1981 ) and Biggs et al. (1982)
N03/P04
17-23
17-23 (t.)
17
20 (ll)
N03/Si02
25-28 2.0-2.8(1l) 0.31
0.34 (t.)
instance in midsummer from 58 0 at 55 0 lat. to 23 0 at the poles. Coincidentally diurnal rhythms become attenuated. This is clearly reflected
in the diurnal variation in global radiation on a clear summer day (Fig.
3). Daily integrals will not differ much for clear days, when comparing
different places in summertime. Weather patterns do, however, influence
the global radiation considerably. Close to the Antarctic continent
where high pressures prevail, the weather is often lightly cloudy or
sunny, whereas the West Wind Drift is characterized by the continuous
passage of low pressures and hence, dominance of cloudy weather. Thus
the global radiation may be higher close to the continent than in the
West Wind Drift (Holm-Hansen et al. 1977). In the Arctic summer fog
and cloudy weather often prevails, but the variability is high. The
monthly average global radiation is hardly more than 20-40% of that of
clear days in that area (Spinnangr 1968).
"
70'
800
"
"
60'
600
so'
15
40'
N
E 400
;i:
JAN
MAR
MAY
JUL
SEP
I'.QV.
5 hemisph
JUL
SEP
NOV
JAN
MAR
MAY
N hemisph
MONTH
Fig. 2. Seasonal variation in day
length at various latitudes. Data
from Holm-Hansen et al. (1977) and
Spinnangr' (1968)
200
12
16
20
2'
hr.
Fig. 3. Diurnal variation in global radiation on clear midsummer days at Troms~
(700 N) and Ny-Alesund, Svalbard (79 0 N)
Submarine light measurements also reflect extreme seasonal variation at high latitudes.
In the Trondheimsfjord, Norway (630 N), measurements with a spherical collector at 0.5m depth indicated that the
peak photon flux density (aver. for the two brightest hours of the day)
ranged from 30 ]JE m- 2 s- 1 in December to 1500 ]JE m- 2 s- 1 in June (Hegseth