Limnological controls on stable isotope records of late-holocene palaeoenvironment change in sw greenland: A paired lake study

摘要

Stable isotope records are increasingly being used in palaeoenvironmental studies of Arctic lakes. Here we compare stable isotope and elemental records (δ~(13)C, δ~(15)N, C/N) with high resolution XRF-derived geochemical and colour data from low Arctic lakes (SS1220 and SS85) in southwest Greenland. Lake SS1220 sediments are laminated gyttja whereas SS85 consist of homogeneous gyttja, both records cover the last c. 5000 years. d13C and carbon content suggest that organic matter in both lakes is predominantly autochthonous. The C/N variability, ranging between 11 and 15, is interpreted to be a function of nitrogen deficiency which is further supported by δ~(15)N values (at SS1220) falling close to atmospheric δ~(15)N_(atmosphere). Although some changes in the geochemical stratigraphies presented here can be related to regional environmental change (i.e. hydrology, effective precipitation, aeolian activity), these effects are filtered through the lake catchments. These changes alter the nutrient supply and hence lake productivity which appear to be the primary controls on the stable isotope data. We suggest that information of past environmental change can only be gained from the stable isotope composition of lake sediments when there is a reasonable understanding of limnological processes, and records may be lake specific.