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Climatologic and hydrologic influences on the oxygen isotopic composition of tree-ring cellulose in southern California over the 20th century
Presented by Dr. Lisa KANNER on 15 May 2013 from 18:00 to 21:00
Type: Poster Presentation
Session: Poster Session + Reception
Board #: 2
Quercus douglasii (blue Oak) tree-ring cellulose δ18O in southern California contains a memory of the interannual variability in precipitation δ18O via soil water δ18O. Combined, soil water δ18O and cellulose δ18O provide insights into regional hydrologic variability that may be caused by distinct atmospheric dynamics. In the late 20th century, years with uniquely low cellulose δ18O are associated with known El Niño events, high relative humidity, and high precipitation in the region. High relative humidity decreases evaporative enrichment in the soil and leaf water, driving cellulose δ18O to lower values. Dynamically, during these isotopically low years, Reanalysis-derived atmospheric wind patterns suggest anomalously high upper level divergence, which favors condensation higher in the atmosphere, also lowering precipitation δ18O. At the transition into the 20th century, Q. douglasii cellulose δ18O exhibits a mean-state shift of about -2‰. This shift potentially implies a change in relative humidity, temperature, or moisture source region.