Seasonal Isotope Records in a Galapagos Coral: Indications of Large Shifts in Circulation and Climate During the Early 1800s

HR: 0800h
AN: GC51A-0152 [Abstracts]
TI: Seasonal Isotope Records in a Galapagos Coral: Indications of Large Shifts in Circulation and Climate During the Early 1800s
AU: * Druffel, E R
EM: edruffel@uci.edu
AF: Earth System Science, University of California Irvine, Irvine, CA 92697-3100, United States
AU: Griffin, S R
EM: sgriffin@uci.edu
AF: Earth System Science, University of California Irvine, Irvine, CA 92697-3100, United States
AU: Druffel-Rodriguez, K C
EM: kevindr03@yahoo.com
AF: Earth System Science, University of California Irvine, Irvine, CA 92697-3100, United States
AU: Dunbar, R B
EM: dunbar@stanford.edu
AF: Department of Geological and Environmental Sciences, Stanford University, Stanford, CA 94305, United States
AB: We present isotope measurements of monthly coral samples that grew in Urvina Bay, Galapagos Islands in the eastern tropical Pacific Ocean. The purpose of this study is to understand the changes in circulation and climate that have occurred in this region of intense upwelling. This study builds on previous results that revealed low annual Δ¹⁴C values during the early 1600s and early 1800s. Measurements of Δ¹⁴C in monthly samples of coral that grew during the first three decades of the 1800s reveal distinct seasonal variability that generally ranges from summertime highs of -55 to -60 per mil to wintertime low values of -65 to -80 per mil. The seasonal range of Δ¹⁴C varies markedly over this period, from ~ 7 - 25 per mil. Low Δ¹⁴C water that arrives in the eastern tropical Pacific during the wintertime originates from high- latitude water (Subantarctic Mode Water) that is entrained into the Equatorial Undercurrent. Possible mechanisms that could cause the observed variability of the seasonal isotope records, including shifts of the westerlies, will be presented.
DE: 1616 Climate variability (1635, 3305, 3309, 4215, 4513)
DE: 1635 Oceans (1616, 3305, 4215, 4513)
DE: 4231 Equatorial oceanography
DE: 4513 Decadal ocean variability (1616, 1635, 3305, 4215)
SC: Global Environmental Change [GC]
MN: 2007 Fall Meeting