224
Wolffetal.
difficult to achieve. Future work is necessary to
improve:
1. the accuracy of the independent temperature
reconstruction methods,
2. the knowledge of the preferred environmental
conditions of planktonic foraminifera and possible
vital effects, and
3. the knowledge of the regional 8 18 0 W -salinity
relationships in the present and past and their determining factors.
Work on temperature sensitivities of some
planktonic foraminifera and the effect on the oxygen isotope record has shown that isotope analysis of three species has the potential to provide
direct estimates of the 8 18 0 W without the need for
independent temperature methods (Mulitza et al.
1998). Also, modelling might improve our understanding of the 8 18 0 w -salinity relationship
(Herterich, personal communication).
Salinity reconstructions methods using
foraminiferal species data do not provide reliable
results when they are applied to downcore data,
since foraminiferal species abundance patterns
seem to be primarily controlled by temperature.
Therefore salinity estimates are governed by the
present day temperature-salinity relationships.
Future work should focus on the ecological
constraints of foraminiferal assemblages. Transfer
functions and MAT isolate single environmental
parameters and try to reconstruct these disregarding other factors. ANN's have the potential of
combining several parameters and may impart a
better insight into the dependency of faunal assemblages on the environment's properties as a whole.
It may then become possible to improve the determination oftemperature, salinity, nutrient concentration, and other paleoceanographicaIly important
parameters by using foraminiferal count data.
Acknowledgments
We would like to thank R.Siegerwho provided the
program MacMAT. We thank B.Meyer-Schack
and M.Segl for performing the stable isotope analysis. Reviews by R. Zahn and W.H. Berger significantly improved the manuscript.
This research was funded
Deutsche Forschungsgemeinschaft
by the
(Sonderforschungsbereich 261 at Bremen University,
Contribution No. 179). Data are available under
www.pangaea.de/Projects/SFB261.
References
Barnett TP, Hasselmann K (1979) Techniques oflinear
prediction with application to oceanic and atmospheric fields in the tropical Pacific. Revs Geophys
Space Phys 17: 949-968
Berger WH, Gardner JV (1975) On the determination of
Pleistocene temperatures from planktonic
foraminifera. J ForamRes 5: 102-113
Berger WH (1981) Paleoceanography: the deep-sea
record. In: Emiliani C (ed) The Sea, Vol. 7. WileyInterscience, New York, pp 1437-1519
BijmaJ, Faber WW, Hemleben C (1990) Temperature and
salinity limits for growth and survival of some planktonic foraminifers in laboratory cultures. J F oram Res
20:95-116
Brassell SC, Eglington G, Pflaumann U, Sarnthein M
(1986) Molecular stratigraphy: a new tool for climatic
assessment. Nature 320: 129-133
Broecker WS (1986) Oxygen isotope constraints on
surface ocean temperatures. Quat Res 26: 2-14
Broecker WS (1989) The salinity contrast between the
Atlantic and Pacific oceans during glacial time.
Paleoceanography 4: 207-212
Broecker WS, Denton GH (1989) The role of ocean-atmosphere reorganisations in glacial cycles. Geochim
Cosmochim Acta 53: 2465-2501
Broecker WS (1990) Salinity history of the Northern
Atlantic during the last deglaciation. Paleoceanography 5: 459-467
Charles CD, Fairbanks RG (1990) Glacial to interglacial
changes in the isotopic gradients of southern ocean
surface waters. In: Bleil U, Thiede J (eds) Geological
History of the Polar Oceans: Arctic versus Antarctic. Kluwer Academic, Dordrecht, pp 519-538
Clapperton CM (1993) Nature of environmental changes
in South America at the last glacial maximum.
Paleogeogr Paleoclimatol Paleoecoll01: 189-208
CLIMAP Project Members (1976) The Surface of the IceAge Earth. Science 191: 1131-1137
CLIMAP Project Members (1981) Seasonal reconstructions of the Earth's surface at the last glacial maximum. GSA Map and ChartSerMC-36: 1-18
Craig H, Gordon LI (1965) Deuterium and oxygen-18
variations in the ocean and marine atmosphere. In:
Tongiorgi E (ed) Stable isotopes in oceanic studies
and paleotemperatures. Spoleto, Consiglio Naz Delle
Ricerche, Laboratorio di Geol Nuc, Pisa,
pp9-130
Wolffetal.
difficult to achieve. Future work is necessary to
improve:
1. the accuracy of the independent temperature
reconstruction methods,
2. the knowledge of the preferred environmental
conditions of planktonic foraminifera and possible
vital effects, and
3. the knowledge of the regional 8 18 0 W -salinity
relationships in the present and past and their determining factors.
Work on temperature sensitivities of some
planktonic foraminifera and the effect on the oxygen isotope record has shown that isotope analysis of three species has the potential to provide
direct estimates of the 8 18 0 W without the need for
independent temperature methods (Mulitza et al.
1998). Also, modelling might improve our understanding of the 8 18 0 w -salinity relationship
(Herterich, personal communication).
Salinity reconstructions methods using
foraminiferal species data do not provide reliable
results when they are applied to downcore data,
since foraminiferal species abundance patterns
seem to be primarily controlled by temperature.
Therefore salinity estimates are governed by the
present day temperature-salinity relationships.
Future work should focus on the ecological
constraints of foraminiferal assemblages. Transfer
functions and MAT isolate single environmental
parameters and try to reconstruct these disregarding other factors. ANN's have the potential of
combining several parameters and may impart a
better insight into the dependency of faunal assemblages on the environment's properties as a whole.
It may then become possible to improve the determination oftemperature, salinity, nutrient concentration, and other paleoceanographicaIly important
parameters by using foraminiferal count data.
Acknowledgments
We would like to thank R.Siegerwho provided the
program MacMAT. We thank B.Meyer-Schack
and M.Segl for performing the stable isotope analysis. Reviews by R. Zahn and W.H. Berger significantly improved the manuscript.
This research was funded
Deutsche Forschungsgemeinschaft
by the
(Sonderforschungsbereich 261 at Bremen University,
Contribution No. 179). Data are available under
www.pangaea.de/Projects/SFB261.
References
Barnett TP, Hasselmann K (1979) Techniques oflinear
prediction with application to oceanic and atmospheric fields in the tropical Pacific. Revs Geophys
Space Phys 17: 949-968
Berger WH, Gardner JV (1975) On the determination of
Pleistocene temperatures from planktonic
foraminifera. J ForamRes 5: 102-113
Berger WH (1981) Paleoceanography: the deep-sea
record. In: Emiliani C (ed) The Sea, Vol. 7. WileyInterscience, New York, pp 1437-1519
BijmaJ, Faber WW, Hemleben C (1990) Temperature and
salinity limits for growth and survival of some planktonic foraminifers in laboratory cultures. J F oram Res
20:95-116
Brassell SC, Eglington G, Pflaumann U, Sarnthein M
(1986) Molecular stratigraphy: a new tool for climatic
assessment. Nature 320: 129-133
Broecker WS (1986) Oxygen isotope constraints on
surface ocean temperatures. Quat Res 26: 2-14
Broecker WS (1989) The salinity contrast between the
Atlantic and Pacific oceans during glacial time.
Paleoceanography 4: 207-212
Broecker WS, Denton GH (1989) The role of ocean-atmosphere reorganisations in glacial cycles. Geochim
Cosmochim Acta 53: 2465-2501
Broecker WS (1990) Salinity history of the Northern
Atlantic during the last deglaciation. Paleoceanography 5: 459-467
Charles CD, Fairbanks RG (1990) Glacial to interglacial
changes in the isotopic gradients of southern ocean
surface waters. In: Bleil U, Thiede J (eds) Geological
History of the Polar Oceans: Arctic versus Antarctic. Kluwer Academic, Dordrecht, pp 519-538
Clapperton CM (1993) Nature of environmental changes
in South America at the last glacial maximum.
Paleogeogr Paleoclimatol Paleoecoll01: 189-208
CLIMAP Project Members (1976) The Surface of the IceAge Earth. Science 191: 1131-1137
CLIMAP Project Members (1981) Seasonal reconstructions of the Earth's surface at the last glacial maximum. GSA Map and ChartSerMC-36: 1-18
Craig H, Gordon LI (1965) Deuterium and oxygen-18
variations in the ocean and marine atmosphere. In:
Tongiorgi E (ed) Stable isotopes in oceanic studies
and paleotemperatures. Spoleto, Consiglio Naz Delle
Ricerche, Laboratorio di Geol Nuc, Pisa,
pp9-130