HR: 0800h
AN: PP11A-0214    [Abstracts]
TI: Calibration of meteorological conditions with tree ring chemistry: high-resolution stable isotope evidence from robotically micromilled cellulose
AU: * Brasseur, J M
EM: jmb248@mail.usask.ca
AF: Saskatchewan Isotope Laboratory, Department of Geological Sciences, University of Saskatchewan, 114 Science Place, Saskatoon, SK S7N 5E2, Canada
AU: Patterson, W P
EM: bill.patterson@usask.ca
AF: Saskatchewan Isotope Laboratory, Department of Geological Sciences, University of Saskatchewan, 114 Science Place, Saskatoon, SK S7N 5E2, Canada
AU: Eglington, B M
EM: bruce.eglington@usask.ca
AF: Saskatchewan Isotope Laboratory, Department of Geological Sciences, University of Saskatchewan, 114 Science Place, Saskatoon, SK S7N 5E2, Canada
AB: Stable isotope values of tree ring cellulose record variation in humidity, soil moisture and stable isotope values of precipitation. We refine and constrain this hypothesis by examining tree ring cellulose from the northeastern United States. Cottonwood trees ( Populus deltoides) from Green Lake State Park (GLSP) in central New York State were robotically micromilled to recover discrete high resolution aliquots of cellulose that represent as little as two weeks growth. Cellulose δ¹³C, δ¹⁸O and δD values were compared to instrumental meteorological records, including temperature, precipitation (amount and isotope value), and humidity to evaluate the integrity with which tree cellulose records atmospheric conditions. Trees from GLSP were selected because they are adjacent to our precipitation collection site and our long carbonate-based climate record recovered from Green Lake sediment that has been calibrated with a century of meteorological data. A detailed cellulose-based record can extend our calibration of lake sediment back beyond the century long meteorological record. Thus, by fine-tuning the carbonate record using tree data an accurate climate record dating back millennia can be generated. Correlations between meteorological, carbonate sediment and tree ring records provides a more robust model for interpretation of climate variability using tree ring and carbonate isotope values. Aliquots of cellulose were recovered using a computer-controlled robotic micromilling device at a spatial resolution of ~0.5mm. Ring widths of our cottonwood trees were up to 7mm, permitting high-resolution sampling. δ¹³C, δ¹⁸O and δD values were obtained from each of the 410 collected samples resulting in a continuous record from 1944-2006. Substantial inter- and intra-seasonal variability is apparent in δ¹³C values that vary by up to 2 permil seasonally and 5 permil over our 62-year tree record. Time-series wavelet analysis of isotope and meteorological data demonstrate a strong solar-climate influence, with δ¹³C lagging behind solar activity by 5-6 years. Lake sediment carbonate δ¹³C values lag behind tree cellulose δ¹³C value, interpreted to represent the time required for decay of cellulose and incorporation into the lake's dissolved inorganic carbon reservoir. A significant decrease in δ¹³C beginning in the early-mid 1980's is attributed to lower SO² concentrations in the atmosphere (known to interfere with leaf stomata) related to declining steel production. Oxygen values conflate a number of variables, including water sources, temperature and moisture stress resulting in considerable intra-seasonal variability. δ¹⁸O values vary by 6 permil over the life of the tree. A record of δD values will likewise be presented.
DE: 0429 Climate dynamics (1620)
DE: 0473 Paleoclimatology and paleoceanography (3344, 4900)
DE: 1041 Stable isotope geochemistry (0454, 4870)
DE: 1616 Climate variability (1635, 3305, 3309, 4215, 4513)
DE: 1694 Instruments and techniques
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting