Open AccessRelationship between modern rainfall variability, cave dripwater, and stalagmite geochemistry in Guam, USA
Author(s) -
Partin Judson W.,
Jenson John W.,
Banner Jay L.,
Quinn Terrence M.,
Taylor Frederick W.,
Sinclair Daniel,
Hardt Benjamin,
Lander Mark A.,
Bell Tomoko,
Miklavič Blaž,
Jocson John M. U.,
Taboroši Danko
Publication year - 2012
Publication title -
geochemistry, geophysics, geosystems
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.928
H-Index - 136
ISSN - 1525-2027
DOI - 10.1029/2011gc003930
Subject(s) - stalagmite , cave , geology , precipitation , groundwater recharge , hydrology (agriculture) , δ18o , wet season , proxy (statistics) , groundwater , isotopes of oxygen , physical geography , geochemistry , climatology , stable isotope ratio , earth science , aquifer , archaeology , geography , physics , geotechnical engineering , cartography , quantum mechanics , machine learning , meteorology , computer science
Modern rainwater, cave dripwater and cave stalagmite geochemical time series from a cave in Guam (13°38′N, 144°53′E) are used to better understand how changes in cave stalagmite geochemistry relate to aboveground changes in rainfall at a tropical location. A scientific field team based in Guam collects ∼monthly samples from multiple sites for geochemical analyses at a cave and aboveground rainfall from a nearby location. We compute a transfer function between rainfall amount and oxygen isotopic composition ( δ 18 O) of a decrease (increase) of 0.94 ± 0.3 m/year for every 1‰ increase (decrease) in rainfall δ 18 O, based on data extracted from the International Atomic Energy Agency (IAEA) Global Networks of Isotopes in Precipitation (GNIP) database and from data generated in this study. Dripwater δ 18 O and Mg/Ca ratios show annual cyclicity at some, but not all sites, accentuating the complex nature of cave hydrology. A stalagmite δ 18 O record for the last ∼160 years indicates the existence of droughts of decadal length, when rainfall is estimated to be ∼0.65 ± 0.3 m/year less than average conditions. This estimate of rainfall reduction most likely refers to wet season months, as these months preferentially contribute to groundwater recharge. The proxy‐based climate record at Guam provides new evidence highlighting how a rainy site in the Western Pacific Warm Pool today can experience considerable changes in rainfall on decadal timescales.