NOAA/WDS Paleoclimatology - Rasbury and Aharon 2006 Avaiki Cave, Niue Island Stalagmite Layer Thickness Data

Niue Island is located in close proximity to the epicenter of the South Pacific Convergence Zone (SPCZ), and its rainfall variability is controlled by changes in the phase of the El Niño–Southern Oscillation (ENSO) phenomenon. Four actively growing stalagmites displaying couplets of light and dark calcite layers were sampled from a flank-margin cave on Niue Island in order to determine the dominant climate factor controlling lamina thickness and establish the usefulness of the stalagmites as archives of ENSO variability records. Couplets counting, AMS radiocarbon assays, and growth rates analysis (mean growth rate: 0.34 ± 0.04 mm/yr for n = 604) support the premise that these couplets are annually deposited and their stalagmites contain records of up to two centuries long. Comparison of band thickness records with instrumental records of air temperature and rainfall kept on the island since 1930 and 1906, respectively, suggests that rainfall variability is the dominant controlling factor. Coherency between the spectral power of the annual layers unraveling periodicities at 2.4 and 5.4 years and that of annual and monsoon rainfall at 2.4–2.7 and 5.2 years corroborates the rainfall control on the band thickness variability of the Niuean stalagmites. Phase lags and amplitude discrepancies between rainfall and stalagmite records are attributed to the impact of torrential rains accompanying cyclones that occasionally struck the island. The excellent agreement between the periodicities prominent in the Niuean stalagmites and those typical of the ENSO phenomenon (2.4 and 4.3–6.0 years) suggests the latter exerts a dominant control on the stalagmite growth rates via rainfall variability. Interdecadal periodicities at 10, 14, and 30 years contained in the Niuean stalagmites spectral power are tentatively attributed to ENSO phase changes driven by the Inter-Decadal Pacific Oscillation (IPO). The Niuean stalagmites, exhibiting relative fast growth rates and prominent layered sequences, hold promise to provide continuous century to millennium-long high-resolution atmospheric records of ENSO history that will complement and expand the sea surface temperature records archived in tropical Pacific corals.