Icebergs in the North Atlantic: Modelling Circulation
Changes and Glacio-Marine Deposition
c. Schafer-Neth and K. Stattegger
1
Introduction
Meltwater events (MWE) during and at the end of the last glaciation led to
dramatic changes in the oceanic circulation of the North Atlantic combined
with a strong reduction in deepwater formation or even a breakdown of the
conveyor belt (Bond 1995; Bond and Lotti 1995; Broecker 1991; Seidov et al.
1996). These changes depend on (i) the amount of freshwater brought in and
(ii) the locations of freshwater input and its transport path; that means the
conditions to form one or several large freshwater lenses on top of the water
column in the central Greenland, Iceland, and Norwegian (GIN) Seas.
Several episodes of rapid discharge of icebergs triggering MWEs are documented by the meltout and sedimentation of debris transported within these
icebergs, recognized as coarse-grained ice-rafted detritus (IRD) and building
up the well-known Heinrich layers on the seafloor (Heinrich 1988; Bond et al.
1992; Dowdeswell et al. 1995).
Recent investigations of Heinrich layers claim major iceberg discharge at
the end of the last glaciation (Termination I) mainly from the Hudson Strait
drainage basin of the North American Laurentide ice sheet (Dowdeswell et al.
1995; Andrews et al. 1994; Grousset et al. 1993) and, to a minor extent, from the
breakdown of the Barents ice sheet (Bischof 1994; Rosell-Mele and Koy 1997;
Svendsen et al. 1996; Vorren et al. 1990). On the other hand, numerical experiments demonstrate clearly that a significant weakening of the conveyor belt
predominantly would take place if a major freshwater injection entered the
northern North Atlantic (NNA) from the northeast caused by the breakdown
of the Barents-shelf ice sheet (Schafer-Neth and Stattegger 1997).
In this chapter, we present OGCM-based numerical experiments of the release, transport and melting of icebergs from various sources along the NNA
margins. Starting scenario is the Last Glacial Maximum (LGM) stage which
has been modelled successfully by Schafer-Neth (1994, 1997; Haupt et al. 1994).
Changes and Glacio-Marine Deposition
c. Schafer-Neth and K. Stattegger
1
Introduction
Meltwater events (MWE) during and at the end of the last glaciation led to
dramatic changes in the oceanic circulation of the North Atlantic combined
with a strong reduction in deepwater formation or even a breakdown of the
conveyor belt (Bond 1995; Bond and Lotti 1995; Broecker 1991; Seidov et al.
1996). These changes depend on (i) the amount of freshwater brought in and
(ii) the locations of freshwater input and its transport path; that means the
conditions to form one or several large freshwater lenses on top of the water
column in the central Greenland, Iceland, and Norwegian (GIN) Seas.
Several episodes of rapid discharge of icebergs triggering MWEs are documented by the meltout and sedimentation of debris transported within these
icebergs, recognized as coarse-grained ice-rafted detritus (IRD) and building
up the well-known Heinrich layers on the seafloor (Heinrich 1988; Bond et al.
1992; Dowdeswell et al. 1995).
Recent investigations of Heinrich layers claim major iceberg discharge at
the end of the last glaciation (Termination I) mainly from the Hudson Strait
drainage basin of the North American Laurentide ice sheet (Dowdeswell et al.
1995; Andrews et al. 1994; Grousset et al. 1993) and, to a minor extent, from the
breakdown of the Barents ice sheet (Bischof 1994; Rosell-Mele and Koy 1997;
Svendsen et al. 1996; Vorren et al. 1990). On the other hand, numerical experiments demonstrate clearly that a significant weakening of the conveyor belt
predominantly would take place if a major freshwater injection entered the
northern North Atlantic (NNA) from the northeast caused by the breakdown
of the Barents-shelf ice sheet (Schafer-Neth and Stattegger 1997).
In this chapter, we present OGCM-based numerical experiments of the release, transport and melting of icebergs from various sources along the NNA
margins. Starting scenario is the Last Glacial Maximum (LGM) stage which
has been modelled successfully by Schafer-Neth (1994, 1997; Haupt et al. 1994).