Stable Oxygen Isotope Ratios in Benthic Carbonate Shells of
Ostracoda, Foraminifera, and Bivalvia from Surface Sediments
of the Laptev Sea, Summer 1993 and 1994
H. Erlenkeuser l and U. von Grafenstein 2
(I) Leibniz-Labor fiir Altersbestimmung und Isotopenjorschung, Universitat Kiel, Max-Eyth-Strasse 11,
D 24118 Kiel, Germany
(2) Laboratoire des Sciences du Climat et de I'Environnement (LSCE), Domaine du CNRS, Ave de fa Terrasse,
F - 91199 Gif-sur- Yvette Cedex, France.
Received 3 April 1997 and accepted in revised form 5 May 1998
Abstract - Shells of benthic carbonate producers - ostracoda, foraminifera and bivalvia,
with emphasis lain on the ostracoda - have been picked for stable isotope analysis from
surface sediments sampled on the Transdrift I and II expeditions in summer 1993 and 1994,
respectively, all over the middle and southern Laptev Sea. This work presents mean 1) 18 0
values of single shell analyses made on a total of 19 benthic species - bivalvia: 3;
foraminifera (Elphidium): 3; ostracoda: 13 - from 49 stations. The 1) 18 0 figures are related
to water depth and reflect the competition of isotopically light riverine waters added from
the south and normal marine waters from the north-west. Although a numerical link to
actual salinities has not been evaluated, the results nevertheless attest benthic isotopes from
sediment cores an interesting potential to reconstruct the lateral field of the riverine impact
on the hydrography of the Laptev Sea for past climates. - The vital offsets in 1) 18 0 were
roughly quantified for most of the benthic species.
Introduction
The Laptev Sea is one of the large shallow seas in the Arctic domain of the Siberian shelf. Its
meridional extension measures about 800 km, from 113° to 140 °E, and the latidudinal range
covers a similar distance, roughly from 71 ° to 78°N, the northern shelf break. Water depth is
low, at about 20 to 40 m, in most parts of the shelf sea, but the bottom relief shows some
deeper submarine valleys, running northward, which have been formed by the Siberian rivers
in Glacial and Postglacial time when sea level was low.
The wide dimension of the shallow water province of the Laptev Sea largely controls the
hydrographic coupling with the open Arctic Ocean in the north. Salinity and nutrients, two
major factors in the shelf water ecology, are strongly related to the fresh water discharged by
the Siberian rivers from the south and to their pronounced seasonally modulated impact. In the
south-eastern Laptev Sea, far distant and oceanographically shielded from the high marine
environment in the north (see Hass et aI., 1995, for a circulation pattern), the fresh water
discharge of the rivers Lena and Yana make salinity of the surface waters drop to 10 psu or less
in the surface waters (Karpiy, 1994). The freshwater contribution also imprints on the physical
and chemical properties of the bottom waters, both directly by seasonal convection and shelf
brine water formation and by the biogeochemical response of the sediment-water interface as to
the planktonic productivity in the surface waters. This response is readily seen in the light
isotopic composition of the dissolved inorganic carbon (DIC) of bottom waters (Erlenkeuser et
aI., 1995), a feature largely resulting from remineralisation of organic matter. In the northern
Laptev Sea, where the advection of high marine waters is more effective, bottom water salinity
may attain almost normal marine values. Sea ice formation may have additional effects on
salinity and in detail could have contributed to the often found complex stratification of the
water column (Karpiy et aI., 1994; Churun and Timokhov, 1995).
In: Kassens, H., H.A. Bauch, l. Dmitrenko, H. Eicken, H.-W. Hubberten, M. Melles, J. Thiede and L. Timokhov (eds.)
Land-Ocean Systems in the Siberian Arctic: Dynamics and History. Springer-Verlag, Berlin, 1999,503-514.
Ostracoda, Foraminifera, and Bivalvia from Surface Sediments
of the Laptev Sea, Summer 1993 and 1994
H. Erlenkeuser l and U. von Grafenstein 2
(I) Leibniz-Labor fiir Altersbestimmung und Isotopenjorschung, Universitat Kiel, Max-Eyth-Strasse 11,
D 24118 Kiel, Germany
(2) Laboratoire des Sciences du Climat et de I'Environnement (LSCE), Domaine du CNRS, Ave de fa Terrasse,
F - 91199 Gif-sur- Yvette Cedex, France.
Received 3 April 1997 and accepted in revised form 5 May 1998
Abstract - Shells of benthic carbonate producers - ostracoda, foraminifera and bivalvia,
with emphasis lain on the ostracoda - have been picked for stable isotope analysis from
surface sediments sampled on the Transdrift I and II expeditions in summer 1993 and 1994,
respectively, all over the middle and southern Laptev Sea. This work presents mean 1) 18 0
values of single shell analyses made on a total of 19 benthic species - bivalvia: 3;
foraminifera (Elphidium): 3; ostracoda: 13 - from 49 stations. The 1) 18 0 figures are related
to water depth and reflect the competition of isotopically light riverine waters added from
the south and normal marine waters from the north-west. Although a numerical link to
actual salinities has not been evaluated, the results nevertheless attest benthic isotopes from
sediment cores an interesting potential to reconstruct the lateral field of the riverine impact
on the hydrography of the Laptev Sea for past climates. - The vital offsets in 1) 18 0 were
roughly quantified for most of the benthic species.
Introduction
The Laptev Sea is one of the large shallow seas in the Arctic domain of the Siberian shelf. Its
meridional extension measures about 800 km, from 113° to 140 °E, and the latidudinal range
covers a similar distance, roughly from 71 ° to 78°N, the northern shelf break. Water depth is
low, at about 20 to 40 m, in most parts of the shelf sea, but the bottom relief shows some
deeper submarine valleys, running northward, which have been formed by the Siberian rivers
in Glacial and Postglacial time when sea level was low.
The wide dimension of the shallow water province of the Laptev Sea largely controls the
hydrographic coupling with the open Arctic Ocean in the north. Salinity and nutrients, two
major factors in the shelf water ecology, are strongly related to the fresh water discharged by
the Siberian rivers from the south and to their pronounced seasonally modulated impact. In the
south-eastern Laptev Sea, far distant and oceanographically shielded from the high marine
environment in the north (see Hass et aI., 1995, for a circulation pattern), the fresh water
discharge of the rivers Lena and Yana make salinity of the surface waters drop to 10 psu or less
in the surface waters (Karpiy, 1994). The freshwater contribution also imprints on the physical
and chemical properties of the bottom waters, both directly by seasonal convection and shelf
brine water formation and by the biogeochemical response of the sediment-water interface as to
the planktonic productivity in the surface waters. This response is readily seen in the light
isotopic composition of the dissolved inorganic carbon (DIC) of bottom waters (Erlenkeuser et
aI., 1995), a feature largely resulting from remineralisation of organic matter. In the northern
Laptev Sea, where the advection of high marine waters is more effective, bottom water salinity
may attain almost normal marine values. Sea ice formation may have additional effects on
salinity and in detail could have contributed to the often found complex stratification of the
water column (Karpiy et aI., 1994; Churun and Timokhov, 1995).
In: Kassens, H., H.A. Bauch, l. Dmitrenko, H. Eicken, H.-W. Hubberten, M. Melles, J. Thiede and L. Timokhov (eds.)
Land-Ocean Systems in the Siberian Arctic: Dynamics and History. Springer-Verlag, Berlin, 1999,503-514.