550
Wagner and Dupont
which accounts for about 0.5-1 % of the bulk
terrigenous production of biomass (Mackenzie
1981). About 60% of the modem total delivery of
riverine terrigenous POC occurs from the Asian
continent (Michaelis et al. 1986). Most of the
riverine POC is deposited nearshore and rarely is
transported across the shelf-slope break (Jones
1983; Romankevich 1984; Emerson and Hedges
1988). Flux estimates of terrestrial POC suggest
that about 65% of the total POC entering the ocean
is refractory (Ittekkot 1988) and apparently is laterally displaced by mid-water transport from continental margins to the open ocean (Walsh 1989).
Aquatic displacement ofterrestrial POC is favored
by its low density (1.2 to 1.7 g/cm 3 ) compared to
mineral grains leading to hydrodynamic grain size
sorting, mechanical grain size reduction, and increased chemical degradation (oxidation) of individual organic particles with increasing transport
distance (for comprehensive discussions see Littke
1993 and Tyson 1995). Jones (1987) adequately
named the organic facies covering modem deep
ocean basins "garbage can facies (D)" reflecting
its highly oxidized and detrital organic character. It
has to be stressed that the importance of lateral
advective and resuspensional processes, mainly
occurring along nephleoid layers, are not yet sufficiently constrained (McCave 1986; Walsh 1989;
Laine et al. 1994). After all, annual flux rates of
refractory POC (0.15*10 15 gC yr'I, Ittekkot 1988)
are surprisingly close to the current estimates of
organic carbon burial rates in deep-sea environments (Bruland et al. 1989). This implies that part
of the terrestrial 0 M contributes to the total organic
pool of deep-sea sediments and gets archived in the
geological record.
Deposition of terrestrial OM to the ocean via
eolian transport is more broader dispersed than
riverine discharge and difficult to quantify on a
global scale. A rough estimate ofthe annual eolian
flux ofterrestrial organic carbon is about 0.32*1Q15
gC yrl (Romankevich 1984) which is in the same
order of magnitude as the total global river discharge. Main depositional settings of wind-blown
organic carbon are transition zones between arid
and moderate humid climates and the equatorial
areas (Romankevich 1984). Similar sorting and degradation mechanisms as discussed for aquatic systerns operating during eolian transport. Distribution
patterns of terrigenous OM, however, are much
more complex since wind systems occur at variable latitudes and elevations with different wind
speeds. F or example, one ofthe best studied atmospheric circulation system with regard to eolian supply of terrigenous matter to the ocean is the subtropical and tropical eastern Atlantic (e.g. Sarnthein
et al. 1982; Ruddiman and Janecek 1989;
Tiedemann et al. 1989, 1994; DeMenocal et al.
1993; Ruddimann 1997). Here, the Trade Winds and
the Saharan Air Layer (SAL), which operate at different elevations and to some extent with different
destinations, transport huge amounts of dust from
dry African areas towards the ocean. Long-range
transport to the Carribean Sea is exclusively
achieved by the mid-tropospheric SAL, whereas
supply to near-continental settings and to the eastern Equatorial Atlantic is mainly maintained by the
Trade Winds, blowing at lower elevation. The N-S
displacement ofthe Innertropical Divergence Zone
(ITCZ) causes a seasonal shift in African dust
source areas from a NW summer position in the
Sahara to a SW winter position in the lake Chad
area. A steep lateral gradient regarding the amount
of eolian fall-out from near-continental to remote
oceanic settings is observed off NW-Africa
(Sarnthein et al. 1982; Koopmann 1981), reflecting the decreasing transport energy with increasing transport distance. It should be noted, however,
that even remote oceanic areas such as the central Pacific are reached by wind-carried terrestrial
OM (e.g. Gagosian and Peltzer 1985).
At the present stage, there is little data available
which enables a realistic estimation of average flux
rates of terrestrial organic carbon to high latitude
oceans. As part of the new international programs
in the Arctic Ocean and the Nordic Seas, there is a
rapidly increasing data base concerning general aspects and budgets of iceberg and sea-ice sediment
transport and organic geochemical characteristics
of modern and late Quaternary Arctic and
Nordic Sea deposits (Hebbeln 1992; Hi:ilemann
and Henrich 1994; Stein et al. 1994; Wagner
and Henrich 1994; Schubert 1995; Wagner and
Hi:ilemann 1995; Yunker et al. 1995; Stein and
Schubert 1996; Fahl and Stein 1997; Henrich et a\.
1997; Hebbeln eta\. 1998). The general dominance
Wagner and Dupont
which accounts for about 0.5-1 % of the bulk
terrigenous production of biomass (Mackenzie
1981). About 60% of the modem total delivery of
riverine terrigenous POC occurs from the Asian
continent (Michaelis et al. 1986). Most of the
riverine POC is deposited nearshore and rarely is
transported across the shelf-slope break (Jones
1983; Romankevich 1984; Emerson and Hedges
1988). Flux estimates of terrestrial POC suggest
that about 65% of the total POC entering the ocean
is refractory (Ittekkot 1988) and apparently is laterally displaced by mid-water transport from continental margins to the open ocean (Walsh 1989).
Aquatic displacement ofterrestrial POC is favored
by its low density (1.2 to 1.7 g/cm 3 ) compared to
mineral grains leading to hydrodynamic grain size
sorting, mechanical grain size reduction, and increased chemical degradation (oxidation) of individual organic particles with increasing transport
distance (for comprehensive discussions see Littke
1993 and Tyson 1995). Jones (1987) adequately
named the organic facies covering modem deep
ocean basins "garbage can facies (D)" reflecting
its highly oxidized and detrital organic character. It
has to be stressed that the importance of lateral
advective and resuspensional processes, mainly
occurring along nephleoid layers, are not yet sufficiently constrained (McCave 1986; Walsh 1989;
Laine et al. 1994). After all, annual flux rates of
refractory POC (0.15*10 15 gC yr'I, Ittekkot 1988)
are surprisingly close to the current estimates of
organic carbon burial rates in deep-sea environments (Bruland et al. 1989). This implies that part
of the terrestrial 0 M contributes to the total organic
pool of deep-sea sediments and gets archived in the
geological record.
Deposition of terrestrial OM to the ocean via
eolian transport is more broader dispersed than
riverine discharge and difficult to quantify on a
global scale. A rough estimate ofthe annual eolian
flux ofterrestrial organic carbon is about 0.32*1Q15
gC yrl (Romankevich 1984) which is in the same
order of magnitude as the total global river discharge. Main depositional settings of wind-blown
organic carbon are transition zones between arid
and moderate humid climates and the equatorial
areas (Romankevich 1984). Similar sorting and degradation mechanisms as discussed for aquatic systerns operating during eolian transport. Distribution
patterns of terrigenous OM, however, are much
more complex since wind systems occur at variable latitudes and elevations with different wind
speeds. F or example, one ofthe best studied atmospheric circulation system with regard to eolian supply of terrigenous matter to the ocean is the subtropical and tropical eastern Atlantic (e.g. Sarnthein
et al. 1982; Ruddiman and Janecek 1989;
Tiedemann et al. 1989, 1994; DeMenocal et al.
1993; Ruddimann 1997). Here, the Trade Winds and
the Saharan Air Layer (SAL), which operate at different elevations and to some extent with different
destinations, transport huge amounts of dust from
dry African areas towards the ocean. Long-range
transport to the Carribean Sea is exclusively
achieved by the mid-tropospheric SAL, whereas
supply to near-continental settings and to the eastern Equatorial Atlantic is mainly maintained by the
Trade Winds, blowing at lower elevation. The N-S
displacement ofthe Innertropical Divergence Zone
(ITCZ) causes a seasonal shift in African dust
source areas from a NW summer position in the
Sahara to a SW winter position in the lake Chad
area. A steep lateral gradient regarding the amount
of eolian fall-out from near-continental to remote
oceanic settings is observed off NW-Africa
(Sarnthein et al. 1982; Koopmann 1981), reflecting the decreasing transport energy with increasing transport distance. It should be noted, however,
that even remote oceanic areas such as the central Pacific are reached by wind-carried terrestrial
OM (e.g. Gagosian and Peltzer 1985).
At the present stage, there is little data available
which enables a realistic estimation of average flux
rates of terrestrial organic carbon to high latitude
oceans. As part of the new international programs
in the Arctic Ocean and the Nordic Seas, there is a
rapidly increasing data base concerning general aspects and budgets of iceberg and sea-ice sediment
transport and organic geochemical characteristics
of modern and late Quaternary Arctic and
Nordic Sea deposits (Hebbeln 1992; Hi:ilemann
and Henrich 1994; Stein et al. 1994; Wagner
and Henrich 1994; Schubert 1995; Wagner and
Hi:ilemann 1995; Yunker et al. 1995; Stein and
Schubert 1996; Fahl and Stein 1997; Henrich et a\.
1997; Hebbeln eta\. 1998). The general dominance