Lago Umayo Isotope and Summary Diatom Data and Precipitation Reconstruction over the last 7000 years Baker, P.A.; Fritz, S.C. Baker, P.A. Fritz, S.C. Precipitation Reconstruction earth science/paleoclimate/paleolimnology (total benthic diatoms,null,null,percent,null,paleolimnology,null,null,N,null) earth science/paleoclimate/paleolimnology (depth,null,null,centimeter,null,paleolimnology,null,null,N,null) earth science/paleoclimate/paleolimnology (notes,null,null,null,null,paleolimnology,null,null,C,null) earth science/paleoclimate/paleolimnology (total saline diatoms,null,null,percent,null,paleolimnology,null,null,N,null) earth science/paleoclimate/paleolimnology (total planktic diatoms,null,null,percent,null,paleolimnology,null,null,N,null) earth science/paleoclimate/climate reconstructions|paleolimnology (precipitation,delta 18O,null,meter per year,null,climate reconstructions|paleolimnology,null,null,N,null) earth science/paleoclimate/paleolimnology (age,null,null,calendar year before present,null,paleolimnology,null,null,N,null) earth science/paleoclimate/paleolimnology (delta 18O,calcium carbonate,null,per mil PDB,null,paleolimnology,null,null,N,null) earth science/paleoclimate/paleolimnology earth science/paleoclimate/paleolimnology earth science/paleoclimate/paleolimnology (Lago Umayo>LATITUDE -15.44>LONGITUDE -70.1) This paper serves two purposes: to review current ideas about the nature and forcing of decadal to millennial scale precipitation variation in the southern tropics of South America during the late Quaternary and to present a new methodology for the reconstruction of precipitation as applied to a Holocene stable isotopic record of carbonate sediments in a tropical Andean lake, Lago Umayo, Peru. The basic thesis of the first part of the paper is that, although modern instrumental records suffice for deducing climate variability at decadal and shorter time scales, these records cannot adequately characterize the nature and forcing of lower-frequency climate variation. Understanding the nature of multi-decadal to millennial-scale climate variation and the mechanisms of large abrupt climate change is best derived from paleoclimatic time series. Tropical Atlantic sea-surface temperature variation is a significant control on tropical South American paleoclimate at these longer time scales. In the second part of the paper, an original method is presented for quantitatively reconstructing precipitation. This method utilizes the well-known relationship between the stable isotopic composition of precipitation and the amount of precipitation, a relationship that is highly significant in many tropical locales. Due to many simplifying assumptions, the reconstruction should be considered to be tentative. A ~12% increase in precipitation (~570 to 650 mm a –1) at 4750 cal year BP is consistent with the 6% increase in summer insolation at this latitude over the same period. However, the increase in precipitation was neither unidirectional nor gradual. Instead, every 240 years on average, precipitation increased or decreased by at least ~8% for periods lasting on average 100 years. The largest of these events had ~15% positive or negative departures from the long-term mean precipitation. These southern tropical wet events apparently coincided with periods of low sea-surface temperatures in the high-latitude North Atlantic, supporting a hypothesis of a tropical North Atlantic sea-surface temperature control on tropical South American precipitation at decadal to millennial scales. STUDY NOTES: diatom species data have been submitted to Neotoma. Precipitation is calculated from an isotope model; see paper for details. 14C dates were calibrated using Calib 5.0.2 (Stuiver and Reimer 1993) using the Southern Hemisphere calibration (McCormac et al. 2004). Provided Keywords: South America, tropics, Andes, SA monsoon, oxygen isotopes, carbonates, diatoms NCDC-Paleoclimatology https://www.ncdc.noaa.gov/data-access/paleoclimatology-data - Bauer Bruce Investigator : Baker, P.A. Investigator : Fritz, S.C. 2015-08-26 ONLINE Files online, ASCII https://www.ncdc.noaa.gov/paleo/study/19160 https://www1.ncdc.noaa.gov/pub/data/paleo/paleolimnology/southamerica/peru/baker2009/baker2009-lagoumayo.txt https://www1.ncdc.noaa.gov/pub/data/paleo/paleolimnology/southamerica/peru/baker2009/baker2009-lagoumayo.txt English https://www.ncdc.noaa.gov/paleo/study/19160 https://www1.ncdc.noaa.gov/pub/data/paleo/paleolimnology/southamerica/peru/baker2009/baker2009-lagoumayo.txt Baker, P.A., S.C Fritz, S.J Burns, E. Ekdahl, C.A. Rigsby2009The nature and origin of decadal to millennial scale climate variability in the southern tropics of South AmericaDevelopments in Paleoenvironmental Research301-32210.1007/978-90-481-2672-9_13 Ekdahl, E., S.C. Fritz, P.A. Baker, C.A. Rigsby, K. Coley2008Holocene multi-decadal to millennial scale hydrologic variability on the South American AltiplanoThe Holocene18867-87610.1177/0959683608093524 START YEAR: 6656 cal yr BP * END YEAR: 127 cal yr BP -70.1 -15.44 -70.1 -15.44