Varied Spatial Response of the SPCZ on Multi-decadal Timescales over the past 500 Years

Monday, 15 December 2014
Judson Wiley Partin1, Terrence M Quinn2, Julien Emile-Geay3, Kaustubh Thirumalai4 and Yuko Okumura1, (1)University of Texas at Austin, Austin, TX, United States, (2)University of Texas at Austin, Institute for Geophysics, Jackson School of Geosciences, Austin, TX, United States, (3)University of Southern California, Los Angeles, CA, United States, (4)University of Texas, Institute for Geophysics, Austin, TX, United States
Over the instrumental period, the position of the South Pacific Convergence Zone (SPCZ) changes on annual, interannual and multi-decadal timescales. One such change in position on multi-decadal timescales occurred during the climate regime shift in 1976/1977. We investigate the spatial and temporal response of the SPCZ using stalagmite-based rainfall reconstructions from Vanuatu and the Solomon Islands that cover the last 500 years. The two stalagmite reconstructions contain significant multi-decadal variability centered near 50 years. We explore the source of the multi-decadal variability by evaluating the influence of karst processes, solar forcing, volcanic forcing and internal climate variability. We conclude that internal climate variability is the most likely source of the multi-decadal rainfall variability in the reconstructions. The two stalagmite rainfall reconstructions suggest a spatial heterogeneity to the past multi-decadal swings in the SPCZ that is more complex than that is observed during the instrumental period. We investigate this complex spatial response of the SPCZ by examining output from long runs (last 1000 years) in the PMIP3 dataset.