Holocene climate change and carbon cycling in a groundwater-fed, boreal forest lake: Dune Lake, Alaska

摘要: Opal, organic C and N contents, δ13C δ15N stable isotopes were analyzed on a sedimentary sequence spanning the past ~12,000 years from Dune Lake, shallow groundwater-fed lake in boreal forest region of central interior Alaska. The chronology, based 210Pb 15 AMS radiocarbon dates terrestrial materials, indicates that 5 m biogenic sediment accumulated following dune stabilization at ~10,000 cal yr BP. Previous studies level pollen synthesized with these data to assess Holocene changes hydrogeology climate. Variability groundwater flux has strong control are negatively correlated matter produced within lake. This relationship results input high pCO2 dissolved inorganic carbon depleted 13C, which subsequently affects phytoplankton signatures. A rapid rise between ca. 11,000 9,500 BP coincided field adjacent expansion vegetation around lake, including white spruce. Organic values relatively low constant about 10,000 6,000 BP, then steadily increase until 2,000 suggesting pattern followed by dropping levels generally consistent core-transect studies. Higher-frequency fluctuations 2–3 ‰ common, suggest variability aspects lake-carbon cycle over multi-decadal timescales. Recent trends level, river discharge, precipitation an important role for wintertime regional system. unusual hydrology this system relative most other lakes studied paleoclimate provides novel insight into different seasonal Alaskan paleoclimatology. record is general long-term decrease precipitation, possibly accompanied permafrost extent, Holocene.