Seasonal and interannual variability of Siberian river discharge in the Laptev Sea inferred from stable isotopes in modern bivalves |
| |
| Authors: | THOMAS MUELLER-LUPP HELMUT ERLENKEUSER HENNING A BAUCH |
| |
| Institution: | GEOMAR Research Center for Marine Geosciences, Wischhofstr.1–3, DE-24148 Kiel, Germany;Leibniz Laboratory for Radiometric Dating and Stable Isotope Research, Kiel University, DE-24098 Kiel, Germany;Alfred-Wegener-Institute for Polar and Marine Research, Columbusstr., DE-27515 Bremerhaven, Germany |
| |
| Abstract: | Stable oxygen and carbon isotope profiles from modern bivalve shells were investigated in order to reconstruct short-term hydrographical changes in the river-shelf system of the Laptev Sea. Oxygen isotopic profiles obtained from the aragonitic species Astarte borealis exhibit amplitude cycles interpreted as annual hydrographical cycles. These records reflect the strong contrast between summer and winter bottom water conditions in the Laptev Sea. The seasonal variations in δ18O are mainly controlled by the riverine freshwater discharge during summer with 0.5‰ per salinity unit. Corrected for a defined species-dependent fractionation offset of -0.37‰, time-dependent salinity records were reconstructed from these δ18O profiles. They indicate a good correspondence to seasonal hydrographic changes and synoptical data. Persistent trends with shell growth towards more negative δ13C values are observed in all specimens and appear to be related to metabolic changes of the bivalves during ontogeny. In contrast, short-term fluctuations are likely linked to seasonal variabilities of the river water outflow patterns and enhanced phytoplankton productivity during summer. This is corroborated by a clear watermass-related distinction of the various δ13C records made on the basis of water depth and distance from the riverine source. |
| |
| Keywords: | |
|
|
