256
Land-Ocean Systems in the Siberian Arctic: Dynamics and History
phosphorus in winter river water were low, 6-9 Ilg/I. A slightly reduced concentration of
silicon on May 26, may reflect an admixture of melted snow because the sample was not taken
under the ice, but from the water layer spreading over the surface of the ice-bound river.
In the period from May 31 to June 5, the concentration of silicon in the river water decreased
to 2100 Ilgll and remained at this level until the end of the observations at June 12. At this time
the water level in the river still increased, but the Bykovskaya channel remained ice-covered.
During the first survey along the N-S transect east off the delta the maximum silicon
concentration of 3840 Ilgll was measured in the layer above the pycnocline at a depth of 2 m at
Station 10. At this station, the silicon concentration was only about 700 Ilglliower than the
silicon concentration recorded in the Lena river during the same time period. Like salinity and
temperature, the vertical concentration of silicon also showed a strong gradient from 3800-2500
Ilgll in the surface layer to 1400-970 Ilg/l below the pycnocline (Figures 2 c).
During the second survey (3-6 June, Figure 3 c) the concentration of silicon in the surface
layer was 4100-4470 Ilg/l . This concentration range resembles the silicon signature typical for
winter river water (Figure 5).
The third survey revealed a decrease in silicon concentration above the pycnocline (Figure 4
c). Concentration were in the range between 2140 and 2340 Ilg/I. This corresponds to
concentration measured in river water during the period of high freshwater discharge. The
water column beneath the pycnocline only showed a small increase in silicon concentration
suggesting that input of remineralized silicon plays no significant role during this period.
Oxygen concentration
The concentration of dissolved oxygen in winter water of the Lena River was 5.7-5.8 mill, or
56 % of the theoretical saturation. Water above the pycnocline showed an oxygen saturation
ranging from 77 to 94 %. The highest oxygen saturation (85 %) was observed directly beneath
the ice cover (Figure 2 d). This is almost 30 % higher than the observed saturation percentage
in the river. During the second survey along the transect (3-6 June) minimum oxygen
concentration of 5.7-5.8 ml/l (56-57 % of saturation) in 2 m water depth at stations 10 and 4
reflect an inflow of winter river water (Figure 3 d). Low oxygen saturation in bottom water
were usually observed at the northern flanks of shoals.
The water column below the pycnocline was characterised by oxygen concentrations between
4.2-7.8 ml/l. The oxygen distribution shown in Figure 6 gives evidence that oxygenated water
from the polynya region (Station 12) sinks and flows towards the Lena delta where it ventilates
the bottom water layer.
Concentration of particulate suspended matter
River water in winter was clear with SPM values below I mgll (Figure 5). During the initial
phase of the breakup the SPM concentration increased to > 20 mg/l, reaching maximum
concentrations observed around June 8. A nearly twofold increase in SPM concentrations (> 35
mgll) was observed on June 13 in the course of the strong ice drift on the river.
During the first survey on the N-S transect the observed SPM concentrations in the water
column ranged between 0.5 and 3 mg/l (Figure 7). A two- to threefold increase in SPM was
observed during the second survey. Both stations near the river channels (8 and 11) showed
SPM concentrations between 7-10 mg/I. A strong increase in SPM concentrations above the
pycnocline was observed during the third survey. Concentrations between 16 and 29 mg/l were
recorded at the northern stations of the transect (3, 5, 10). The highest amount of suspended
matter (73 mgll) was measured near the Trofimovskaya branch (Station 8).
Below the pycnocline SPM concentration changed only slightly (below 5 mg/I), sea water
remained transparent although the turbidity of the surface layer was about 20 mg/l with
Land-Ocean Systems in the Siberian Arctic: Dynamics and History
phosphorus in winter river water were low, 6-9 Ilg/I. A slightly reduced concentration of
silicon on May 26, may reflect an admixture of melted snow because the sample was not taken
under the ice, but from the water layer spreading over the surface of the ice-bound river.
In the period from May 31 to June 5, the concentration of silicon in the river water decreased
to 2100 Ilgll and remained at this level until the end of the observations at June 12. At this time
the water level in the river still increased, but the Bykovskaya channel remained ice-covered.
During the first survey along the N-S transect east off the delta the maximum silicon
concentration of 3840 Ilgll was measured in the layer above the pycnocline at a depth of 2 m at
Station 10. At this station, the silicon concentration was only about 700 Ilglliower than the
silicon concentration recorded in the Lena river during the same time period. Like salinity and
temperature, the vertical concentration of silicon also showed a strong gradient from 3800-2500
Ilgll in the surface layer to 1400-970 Ilg/l below the pycnocline (Figures 2 c).
During the second survey (3-6 June, Figure 3 c) the concentration of silicon in the surface
layer was 4100-4470 Ilg/l . This concentration range resembles the silicon signature typical for
winter river water (Figure 5).
The third survey revealed a decrease in silicon concentration above the pycnocline (Figure 4
c). Concentration were in the range between 2140 and 2340 Ilg/I. This corresponds to
concentration measured in river water during the period of high freshwater discharge. The
water column beneath the pycnocline only showed a small increase in silicon concentration
suggesting that input of remineralized silicon plays no significant role during this period.
Oxygen concentration
The concentration of dissolved oxygen in winter water of the Lena River was 5.7-5.8 mill, or
56 % of the theoretical saturation. Water above the pycnocline showed an oxygen saturation
ranging from 77 to 94 %. The highest oxygen saturation (85 %) was observed directly beneath
the ice cover (Figure 2 d). This is almost 30 % higher than the observed saturation percentage
in the river. During the second survey along the transect (3-6 June) minimum oxygen
concentration of 5.7-5.8 ml/l (56-57 % of saturation) in 2 m water depth at stations 10 and 4
reflect an inflow of winter river water (Figure 3 d). Low oxygen saturation in bottom water
were usually observed at the northern flanks of shoals.
The water column below the pycnocline was characterised by oxygen concentrations between
4.2-7.8 ml/l. The oxygen distribution shown in Figure 6 gives evidence that oxygenated water
from the polynya region (Station 12) sinks and flows towards the Lena delta where it ventilates
the bottom water layer.
Concentration of particulate suspended matter
River water in winter was clear with SPM values below I mgll (Figure 5). During the initial
phase of the breakup the SPM concentration increased to > 20 mg/l, reaching maximum
concentrations observed around June 8. A nearly twofold increase in SPM concentrations (> 35
mgll) was observed on June 13 in the course of the strong ice drift on the river.
During the first survey on the N-S transect the observed SPM concentrations in the water
column ranged between 0.5 and 3 mg/l (Figure 7). A two- to threefold increase in SPM was
observed during the second survey. Both stations near the river channels (8 and 11) showed
SPM concentrations between 7-10 mg/I. A strong increase in SPM concentrations above the
pycnocline was observed during the third survey. Concentrations between 16 and 29 mg/l were
recorded at the northern stations of the transect (3, 5, 10). The highest amount of suspended
matter (73 mgll) was measured near the Trofimovskaya branch (Station 8).
Below the pycnocline SPM concentration changed only slightly (below 5 mg/I), sea water
remained transparent although the turbidity of the surface layer was about 20 mg/l with