140
B. J. Haupt· K. Stattegger . D. Seidov
across these walls, we cannot arrive at reasonable sediment dynamics in this location.
The high sediment input to the English and French shelf areas from southern
England and the French rivers Seine and Loire is responsible for the observed
high sedimentation rates (Einsele 1992). Contrarily, the runoff from the German
rivers Elbe and Weser is not limited to the river mouths. Although most of the
sediment is deposited in the eastern German Bight, some is still transported to
and deposited in the Norwegian Channel and on the southern V 0ring Plateau
(63°N,SO-7°W).
A comparison of the experiments El and E2 shows that small local changes in
the sediment supply can affect the sediment distribution in remote areas. Theses
changes are dearly seen in the transport through gateways and along vertical
cross sections. Figure 21a (experiment El) and Fig. 21b (experiment E2) show
the transport in the water column and at the bottom in tons km- 2 year-I. Both
experiments indicate that most of the sediment transport occurs in the bottom
layer. The transport through the cross section increases with the increase of additionallateral sediment supply everywhere except for two locations. Whether
the decrease found between Svalbard and Franz Josef Land is a real feature or an
artifact created by the dosed northern boundary cannot be answered with this
model. In Experiment E2 (Fig. 21b), the bottom transport over the Iceland-Faeroe-Ridge changes from a southward sediment transport (Fig. 21a) to a northward transport. In this region, the currents are generally parallel to the IcelandFaeroe-Ridge (Figs. ISb, 20). In a set of several supplementary experiments we
discovered that a small shift of this cross section to the north or to the south resulted in a change in the transport direction.
7
Conclusions
Integrated numerical models of oceanic circulation, sedimentation, and tracing
water volumes lead to a better understanding of the complexity of interactions in
the climatically forced ocean-sediment system. Two 3-D numerical models, SEDLOB and PATLOB, were developed to reconstruct the sedimentary history of the
North Atlantic. Both models consist of a 3-D submodel for the water column and
a 2-D bottom layer to model the specific features of near-bottom process motion.
The models were tested using different horizontal and vertical resolutions in the
North and northeastern Atlantic. High resolution experiments aimed at the simulation of detailed features of sediment flux through gateways and cross sections
were discussed. The models are initialized using the output of an OGCM and different sediment sources. We supplied material by vertical eolian input from the atmosphere and from lateral sediment input by rivers and ice. In all experiments, the
critical velocities for movement of bed load and suspension load were reduced to
arrive at more realistic transports at the bottom in ocean basins. The employed
polynominal equations for the sediment transport and the critical velocities were
modified by an empirical function to introduce the dependence on bottom slope.
B. J. Haupt· K. Stattegger . D. Seidov
across these walls, we cannot arrive at reasonable sediment dynamics in this location.
The high sediment input to the English and French shelf areas from southern
England and the French rivers Seine and Loire is responsible for the observed
high sedimentation rates (Einsele 1992). Contrarily, the runoff from the German
rivers Elbe and Weser is not limited to the river mouths. Although most of the
sediment is deposited in the eastern German Bight, some is still transported to
and deposited in the Norwegian Channel and on the southern V 0ring Plateau
(63°N,SO-7°W).
A comparison of the experiments El and E2 shows that small local changes in
the sediment supply can affect the sediment distribution in remote areas. Theses
changes are dearly seen in the transport through gateways and along vertical
cross sections. Figure 21a (experiment El) and Fig. 21b (experiment E2) show
the transport in the water column and at the bottom in tons km- 2 year-I. Both
experiments indicate that most of the sediment transport occurs in the bottom
layer. The transport through the cross section increases with the increase of additionallateral sediment supply everywhere except for two locations. Whether
the decrease found between Svalbard and Franz Josef Land is a real feature or an
artifact created by the dosed northern boundary cannot be answered with this
model. In Experiment E2 (Fig. 21b), the bottom transport over the Iceland-Faeroe-Ridge changes from a southward sediment transport (Fig. 21a) to a northward transport. In this region, the currents are generally parallel to the IcelandFaeroe-Ridge (Figs. ISb, 20). In a set of several supplementary experiments we
discovered that a small shift of this cross section to the north or to the south resulted in a change in the transport direction.
7
Conclusions
Integrated numerical models of oceanic circulation, sedimentation, and tracing
water volumes lead to a better understanding of the complexity of interactions in
the climatically forced ocean-sediment system. Two 3-D numerical models, SEDLOB and PATLOB, were developed to reconstruct the sedimentary history of the
North Atlantic. Both models consist of a 3-D submodel for the water column and
a 2-D bottom layer to model the specific features of near-bottom process motion.
The models were tested using different horizontal and vertical resolutions in the
North and northeastern Atlantic. High resolution experiments aimed at the simulation of detailed features of sediment flux through gateways and cross sections
were discussed. The models are initialized using the output of an OGCM and different sediment sources. We supplied material by vertical eolian input from the atmosphere and from lateral sediment input by rivers and ice. In all experiments, the
critical velocities for movement of bed load and suspension load were reduced to
arrive at more realistic transports at the bottom in ocean basins. The employed
polynominal equations for the sediment transport and the critical velocities were
modified by an empirical function to introduce the dependence on bottom slope.