338
Riihlemann et al.
sess the reliability and suitability of any single index in a particular environment.
The dichotomy ofthe modern tropical Atlantic
with the highly productive eastern upwelling system and the oligotrophic western ocean prevailed
throughout the last 300 ka. However, during the
cold climatic stages, the share of organic carbon
accumulation was shifted drastically in favor of the
eastern continental slope sediments. The reason
was probably an intensification of the SE-trades
increasing the upwelling of nutrient-rich subsurface
waters. Concurrently, paleoproductivity in the open
ocean decreased probably due to a lowered nutrient concentration of glacial intermediate waters.
Moreover, the countercyclic deposition of organic
carbon could have been caused by a wind-driven
deepening of the nutricline in the West - connected
with the synchronous shallowing in the East - analogous to the modern seasonal pattern.
An intensification of paleoproductivity and
seasonality in the upwelling regions during the cold
climatic stages - connected with a corresponding
increase in export production - would have resulted
in a more efficient drawdown of carbon from surface waters and thus, enhanced organic carbon
burial in continental margin sediments. This would
have contributed to a glacial atmospheric pCO,
reduction as documented in continental ice cores.
Francois et al. (1990) emphasized the importance
of the inverse relationship in paleoproductivity between high and low productivity areas calling upon
the 'rain ratio model' of Berger and Keir (1984).
A sharp Glacial-to-Holocene decrease in
paleoproductivity in the upwelling areas (dominated
by non-carbonate producers), occurring contemporaneously with an increase in the oligotrophic open
ocean (dominated by carbonate producers), should
have resulted in a global decrease in the organic
carbon-to-carbonate carbon rain ratio possibly contributing to the observed Glacial-to-Holocene increase in pCO,.
Acknowledgments
We thank G. Fischer, G. Mollenhauer and S.
Mulitza for critical comments on an earlier version
ofthe manuscript and G. Fischer and G. Wefer for
providing unpublished sediment trap flux data.
S. van Kreveld kindly provided material for preparation of figures. The paper benefited from helpful
reviews ofM. Lyle and G .l.A. Brummer. Research
was funded by the Deutsche Forschungsgemeinschaft (Sonderforschungsbereich 261
at Bremen University, Contribution No. 224). Data
are available under www.pangaea.de/Projects/
SFB261.
References
Abrantes F, Winn K, Sarnthein M (1994) Late Quaternary paleoproductivity variations in the NE and
Equatorial Atlantic: Diatom and Coc, evidence. In:
Zahn R, Pedersen TF, Kaminski MA, Labeyrie L (eds)
Carbon Cycling in the Glacial Ocean: Constraints on
the Ocean's Role in Global Change. NATO ASI Series, Vol 17, Springer, Berlin Heidelberg New York,
pp425-441
Anderson DM, Prell WL (1993) A 300 kyr record of
upwelling off Oman during the Late Quaternary:
Evidence of the Asian southwest monsoon.
Paleoceanography 8: 193-208
Antoine D, Andre J.M, Morel A (1996) Oceanic primary
production. 2. Estimation at global scale from satellite (coastal zone color scanner) chlorophyll. Global
Biogeochem Cycles 10: 43-55.
Archer D (1991) Modeling the calcite lysocline. J
Geophys Res 96: 17,037-17,050
Archer D, Emerson S, Reimers C (1989) Dissolution of
calcite in deep-sea sediments: pH and 0,
microelectrode results. Geochim Cosmochim Acta 53:
2831-2846
Bacon MP (1984) Glacial to interglacial changes in carbonate and clay sedimentation in the Atlantic ocean
estimated from '30Th measurements. Isotope Geosci
2:97-111
Bainbridge AE (\ 981) GEOSECS Atlantic Expedition (Vol
I: Hydrographic data). US Govt Printing Office,
WashingtonDC20402,pp 1-121
Bamo1a JM, Raynaud D, Korotkevich YS, Lorius C (1987)
Vostok ice core provides 160,000-year record of
atmospheric CO,. Nature 392: 408-414
Barnola JM, Pimienta P, Raynaud D, Korotkevich YS
(1991) CO, -climate relationship as deduced from the
Vostok ice core: A re-examination based on new
measurements and on a re-evaluation of the air dating. Tellus 43B: 83-90
Be A WH, To1derlund DS (1971) Distribution and ecology ofliving planktonic foraminifera in the surface
waters of the Atlantic and Indian Oceans. In: Funnell
Riihlemann et al.
sess the reliability and suitability of any single index in a particular environment.
The dichotomy ofthe modern tropical Atlantic
with the highly productive eastern upwelling system and the oligotrophic western ocean prevailed
throughout the last 300 ka. However, during the
cold climatic stages, the share of organic carbon
accumulation was shifted drastically in favor of the
eastern continental slope sediments. The reason
was probably an intensification of the SE-trades
increasing the upwelling of nutrient-rich subsurface
waters. Concurrently, paleoproductivity in the open
ocean decreased probably due to a lowered nutrient concentration of glacial intermediate waters.
Moreover, the countercyclic deposition of organic
carbon could have been caused by a wind-driven
deepening of the nutricline in the West - connected
with the synchronous shallowing in the East - analogous to the modern seasonal pattern.
An intensification of paleoproductivity and
seasonality in the upwelling regions during the cold
climatic stages - connected with a corresponding
increase in export production - would have resulted
in a more efficient drawdown of carbon from surface waters and thus, enhanced organic carbon
burial in continental margin sediments. This would
have contributed to a glacial atmospheric pCO,
reduction as documented in continental ice cores.
Francois et al. (1990) emphasized the importance
of the inverse relationship in paleoproductivity between high and low productivity areas calling upon
the 'rain ratio model' of Berger and Keir (1984).
A sharp Glacial-to-Holocene decrease in
paleoproductivity in the upwelling areas (dominated
by non-carbonate producers), occurring contemporaneously with an increase in the oligotrophic open
ocean (dominated by carbonate producers), should
have resulted in a global decrease in the organic
carbon-to-carbonate carbon rain ratio possibly contributing to the observed Glacial-to-Holocene increase in pCO,.
Acknowledgments
We thank G. Fischer, G. Mollenhauer and S.
Mulitza for critical comments on an earlier version
ofthe manuscript and G. Fischer and G. Wefer for
providing unpublished sediment trap flux data.
S. van Kreveld kindly provided material for preparation of figures. The paper benefited from helpful
reviews ofM. Lyle and G .l.A. Brummer. Research
was funded by the Deutsche Forschungsgemeinschaft (Sonderforschungsbereich 261
at Bremen University, Contribution No. 224). Data
are available under www.pangaea.de/Projects/
SFB261.
References
Abrantes F, Winn K, Sarnthein M (1994) Late Quaternary paleoproductivity variations in the NE and
Equatorial Atlantic: Diatom and Coc, evidence. In:
Zahn R, Pedersen TF, Kaminski MA, Labeyrie L (eds)
Carbon Cycling in the Glacial Ocean: Constraints on
the Ocean's Role in Global Change. NATO ASI Series, Vol 17, Springer, Berlin Heidelberg New York,
pp425-441
Anderson DM, Prell WL (1993) A 300 kyr record of
upwelling off Oman during the Late Quaternary:
Evidence of the Asian southwest monsoon.
Paleoceanography 8: 193-208
Antoine D, Andre J.M, Morel A (1996) Oceanic primary
production. 2. Estimation at global scale from satellite (coastal zone color scanner) chlorophyll. Global
Biogeochem Cycles 10: 43-55.
Archer D (1991) Modeling the calcite lysocline. J
Geophys Res 96: 17,037-17,050
Archer D, Emerson S, Reimers C (1989) Dissolution of
calcite in deep-sea sediments: pH and 0,
microelectrode results. Geochim Cosmochim Acta 53:
2831-2846
Bacon MP (1984) Glacial to interglacial changes in carbonate and clay sedimentation in the Atlantic ocean
estimated from '30Th measurements. Isotope Geosci
2:97-111
Bainbridge AE (\ 981) GEOSECS Atlantic Expedition (Vol
I: Hydrographic data). US Govt Printing Office,
WashingtonDC20402,pp 1-121
Bamo1a JM, Raynaud D, Korotkevich YS, Lorius C (1987)
Vostok ice core provides 160,000-year record of
atmospheric CO,. Nature 392: 408-414
Barnola JM, Pimienta P, Raynaud D, Korotkevich YS
(1991) CO, -climate relationship as deduced from the
Vostok ice core: A re-examination based on new
measurements and on a re-evaluation of the air dating. Tellus 43B: 83-90
Be A WH, To1derlund DS (1971) Distribution and ecology ofliving planktonic foraminifera in the surface
waters of the Atlantic and Indian Oceans. In: Funnell