|
The reconstruction of climatic variations of the last 1000 years isregarded as a priority target in current climate research (WCRP CLIVAR,IGBP PAGES). This period covers three phases of the global climate systemin a warm atmosphere: 1) the Medieval Climatic Anomaly (MCA, sometimesreferred to as the Medieval Warm Period, ca. 900 to 1300 AD), 2) LittleIce Age Type Events (LIATES, ca. 1400 - 1900 AD), and 3) the last 100years when anthropogenic perturbations became important and atmosphericgreenhouse gas concentrations increased to unprecedented levels. The last1000 years cover mostly the range of Holocene climate anomalies, providedetailed insight into the spatial and temporal structure of naturalclimate variability, and may answer the question to what extent the 20thcentury is unusual in light of the MCA or the LIATES. Many new well-calibrated and high resolution paleoclimate reconstructionsand time series have been produced for regional, hemispheric and globalscales. Also the main forcing factors are well established, and knowledgeabout the underlying mechanisms and processes is rapidly growing. However,only few paleoclimate records are from tropical areas and only a handfulare from the Southern Hemisphere, which puts serious limitations to globalreconstructions and their interpretations.This proposal seeks funding for research towards a subdecadal multi-proxypaleoclimate reconstruction for the last ca. 1000 years based on sedimentsfrom high-elevation pro-glacial lakes in the Central Andes of Chile 33°S.This area is today in the domain of the extratropical Westerlies withprecipitation mainly during austral winter, and shows a strong ENSO signal(negative correlations between SOI and winter rainfall). Seven small lakes were explored and short cores were retrieved in March2004. Preliminary field and laboratory results show that the sediments ofthese lakes have much potential for high-resolution paleoclimate research.The questions are:-Which climate parameters and processes are recorded today in the lakesediments?-Can this information be used for downcore extrapolation and climatereconstruction?-How do the sediment records compare with other regional climatereconstructions (e.g. ice core data from Mercedario, work in progress;Austrocedrus chilensis tree ring chronology AD 956 - 1996 from Rio delPlomo 32°S)?-How does the regional climate reconstruction compare with (a)large-scale climate indices (e.g., SOI, SAM) derived from GCM ensembleruns (work within the frame of the NCCR Climate) for selected windows oftime during the last 1000 years, (b) time series for forcing factors, and(c) multi-proxy data sets along the IGBP-PAGES pole-equator-pole PEP-1transect through the Americas and in the circum Pacific (ENSO) area.We select the three most promising lakes with complementary basin andsediment characteristics: Laguna del Inka LI (32°50’S, 2840 m), LagunaNegra LN (33°38’S, 2680 m) and Laguna El Ocho LO (34°S, 3250 m). Theselakes are between 44 and >200 m deep. LN has a glaciated catchment (Nev.Echaurren, mass balance observed by the World Glacier Monitoring Service),LO is monomict, has turbidites and sub-mm laminations.
|