NOAA/WDS Paleoclimatology - Lake Qinghai Surface Sediment Isotope and Geochemical Data

Multi-proxy indices on annual/decadal scales during the past 600 years were developed from the surface sediments of Lake Qinghai based on 210Pb and 137Cs geochronology. The d13Ccarb, d18Ocarb, and total carbonate content are consistent with one another in trends and their variations have been mainly ascribed to regional temperature. It is suggested that the strong evaporation contributes in modifying d18O of lake water and d13C of the dissolved inorganic carbon of the surface water, and appears to be responsible for the covariance between d13Ccarb and d18Ocarb. Photosynthesis of the aquatic plants appears to have played a significant role in determining d15N of organic matter. The discrimination of 14N and 15N during photosynthesis may have triggered a positive linkage between temperatures and d15Norg (after removal of the stratigraphic trend).Variations of total organic carbon (TOC), C/N ratio, and d13Corg have been ascribed to local precipitation. TOC (after removal of the stratigraphic trend) is positively correlated with the C/N ratio (r = 0.45, a < 0.01), and negatively correlated with d13C of organic matter (d13Corg) (r = - 0.55, a < 0.01); while d13Corg is negatively correlated with the C/N ratio (r = - 0.48, a < 0.01). The climatic significance of these multi-proxy indices has been verified by comparing with the meteorological records and the climates inferred from tree rings in adjacent regions.