A MULTI-PROXY STALAGMITE INVESTIGATION OF EL NIÑO/SOUTHERN OSCILLATION VARIABILITY DURING THE HOLOCENE FROM THE EASTERN COLOMBIAN ANDES

El Niño/Southern Oscillation (ENSO) constitutes one of the most important driving mechanisms of interannual climate variability on the planet. However, despite its importance, consensus regarding its temporal and spatial evolution, including frequency and magnitude, is lacking. Additionally, the limited instrumental data used to model and forecast ENSO behavior is not adequate. In response to these issues, paleo-proxies that overlap with instrumental data and extend into the Holocene have emerged as important options to better constrain ENSO dynamics through time. Existing studies using paleo-proxies to study ENSO variability include mollusk shells, corals, sediment records, and foraminifers among others. In general, all proxies show a strengthening of ENSO activity during the late Holocene and a weakening during the early and the middle Holocene, with a marked minimum activity during mid-Holocene. (Carré et al., 2014; Clement et al., 2000; Cobb et al.,2013; Koutavas et al., 2006; Koutavas and Joanides, 2012). However, even with some agreement among studies more information from regions sensitive to ENSO variability is needed to further support or challenge current paradigms.

The purpose of this study is to reconstruct the ENSO variability during the Holocene from the eastern Colombian Andes using stable oxygen and carbon isotopes, laminae thickness, and trace element geochemistry in actively-growing stalagmites. The caves are nearby El Peñon and Las Cruces municipalities, in the Santander Province, in the Colombian Andes. They are part of the Velez karstic system and are made up of limestone from the Rosa Blanca formation. The hydroclimatic conditions in the area are bimodal with marked rainy seasons from April to May and from September to November mainly in response to Intertropical Convergence Zone movements. In terms of interannual precipitation variability, the region shows coherence between negative rain anomalies, decreases in river discharge, and the 3.4 El Niño Index (Poveda et al., 2011). This coherence coupled with the characteristics of the caves and the samples, provide the possibility to explore the relationship between the hydroclimatic variability in this region and ENSO activity during the Holocene.