Model Simulation ofTemporal Variability of Suspended Matter in the North Sea
41
l. Information about the content of fine sediment (fraction < 20 11m) in the sea
bed sediment is given in Fig. 2.
2. The input of SPM (fraction < 20 11m) into the model domain is dominated by
the residual fluxes from the North Atlantic and the Straits of Dover. At the seaward model boundaries, the SPM flux into the model domain is the product
of a prescribed SPM concentration (constant in time) and the instantaneous
water flux. The prescribed SPM concentrations are 0.6 mg 1-1 between Scotland and Orkney, 0.4 mg 1-1 between Orkney and Shetland and 0.3 mg 1-1 between Shetland and Norway. This data is mainly based on measurements of
Eisma and Kalf (1987). In the Straits of Dover, prescribed SPM concentrations
are 7.2 mg 1-1 in the northern half and 4.6 mg 1-1 in the southern half, based
on data of Lafite et al. (1997). The residual SPM flux into the North Sea between Scotland and Shetland is calculated to be 9 Mt a-I as an average of
1986-1993. The SPM flux through the Straits of Dover is calculated to be 17
Mt a-I for the same time period.
SPM supply from the cliffs of eastern England (Holderness, East Anglia) is 4.7
Mt a- 1 (Odd and Murphy 1992). In order to achieve a good agreement of their
simulated SPM concentrations with measured data, Odd and Murphy (1992)
assumed that 90 % of the annual cliff erosion occurs in the four month period
N ovember-February.
The SPM masses entering the North Sea from rivers and by dumping (sewage
sludge, fly ash) can be taken from Pohlmann and PuIs (1994). The input from
rivers and by dumping is comparatively small, the sum is about 2 Mt a-I; the
highest mass flux comes from the Rhine/Meuse/Scheldt with 0.75 Mt a-I.
o ·2
2 - 6
6·12
%
_
>12
sediment fraclIon < 20 ,..m.
in percent of total sediment mass
Fig.2 North Sea model domain with the distribution
of fine sediment content
« 20 !-lm) in the bottom sed
iment
41
l. Information about the content of fine sediment (fraction < 20 11m) in the sea
bed sediment is given in Fig. 2.
2. The input of SPM (fraction < 20 11m) into the model domain is dominated by
the residual fluxes from the North Atlantic and the Straits of Dover. At the seaward model boundaries, the SPM flux into the model domain is the product
of a prescribed SPM concentration (constant in time) and the instantaneous
water flux. The prescribed SPM concentrations are 0.6 mg 1-1 between Scotland and Orkney, 0.4 mg 1-1 between Orkney and Shetland and 0.3 mg 1-1 between Shetland and Norway. This data is mainly based on measurements of
Eisma and Kalf (1987). In the Straits of Dover, prescribed SPM concentrations
are 7.2 mg 1-1 in the northern half and 4.6 mg 1-1 in the southern half, based
on data of Lafite et al. (1997). The residual SPM flux into the North Sea between Scotland and Shetland is calculated to be 9 Mt a-I as an average of
1986-1993. The SPM flux through the Straits of Dover is calculated to be 17
Mt a-I for the same time period.
SPM supply from the cliffs of eastern England (Holderness, East Anglia) is 4.7
Mt a- 1 (Odd and Murphy 1992). In order to achieve a good agreement of their
simulated SPM concentrations with measured data, Odd and Murphy (1992)
assumed that 90 % of the annual cliff erosion occurs in the four month period
N ovember-February.
The SPM masses entering the North Sea from rivers and by dumping (sewage
sludge, fly ash) can be taken from Pohlmann and PuIs (1994). The input from
rivers and by dumping is comparatively small, the sum is about 2 Mt a-I; the
highest mass flux comes from the Rhine/Meuse/Scheldt with 0.75 Mt a-I.
o ·2
2 - 6
6·12
%
_
>12
sediment fraclIon < 20 ,..m.
in percent of total sediment mass
Fig.2 North Sea model domain with the distribution
of fine sediment content
« 20 !-lm) in the bottom sed
iment