Stable isotopic composition of total organic carbon in bottom sediments of Lake Baikal as a proxy for paleoclimatology.

摘要

As indicated by modern climate and a valuable paleoclimate record of Eastern Siberia and Inner Asia, this region is among the most climatically sensitive areas of the globe. The climatic conditions are highly dependent on insolation, and even in modern time the annual average climatic characteristics are heavily dependent on cold season processes.; Biogenic silica as a key-proxy for Lake Baikal sedimentary record, provides an accurate high-resolution climatic record. Three major aspects of biogenic silica are discussed: (1) paleoproductivity index, (2) basis for age control, and (3) highly sensitive indicator of how the East Siberia and Lake Baikal ecosystem respond to climate change.; The isotopic work in Lake Baikal presents ranges of variability and average values on {dollar}deltasp{lcub}13{rcub}{dollar}C and C/N of different sources of organic carbon such as soil organic matter, OM of riverine runoff, planktonic and particulate organic matter, dissolved inorganic carbon. Combined with water chemistry and calculations of nutrient balance, these results are the essential numerical contribution to the present understanding and future modeling of Lake Baikal carbon cycle. Organic matter from different sources in Lake Baikal sediments can be distinguished by its C/N and {dollar}deltasp{lcub}13{rcub}{dollar}C signatures. The sedimentary organic matter is primarily autochthonous.; The perspective on physical limnology suggests a physical mechanism explaining the relation of productivity signal of Lake Baikal to orbital forcing. The link between BioSi flux to the bottom rests on the concept of hydrodynamic limitation of diatom production in Lake Baikal which explains diatom blooms in spring under the ice. Long-term insolation changes control the heat balance of the water column, and production between glacial and interglacial periods dramatically changes in response to insolation orbital forcing.; Similar to marine isotopic records, the {dollar}deltasp{lcub}13{rcub}{dollar}C in Lake Baikal can be used as productivity index, and also {dollar}deltasp{lcub}13{rcub}{dollar}C shift over the last glacial/interglacial transition indicates atmospheric paleo-pCO{dollar}sb2{dollar} change. The paleo-pCO{dollar}sb2{dollar} record from Lake Baikal is the second known lacustrine record, however, with an exceptional temporal span. The fact that paleo-pCO{dollar}sb2{dollar} signal is truly present in Lake Baikal {dollar}deltasp{lcub}13{rcub}{dollar}C record, opens opportunity to obtain long high-resolution record of atmospheric paleo-pCO{dollar}sb2{dollar} from the interior of the largest continent on Earth.