Evidence of an active ENSO and PDO during the mid-Holocene from a Costa Rican speleothem.

摘要

The El Nino/Southern Oscillation (ENSO) and the Pacific Decadal Oscillation (PDO) are the most important sources of interannual to multidecadal climate variability in the tropics. A high resolution ({dollar}3.8 years/sample) paleoclimate record of Central American rainfall variability has been reconstructed from a U/Th-dated stalagmite (7890 to 6490 yrs B.P.) from Costa Rica to constrain the onset and variability of ENSO throughout the Holocene, and to determine its role in generating regional climate anomalies. I suggest drier conditions, forced by El Nino and/or the PDO, are represented by higher delta 18O values, and are correlative with higher delta13C values, indicating that soil respiration rates are affected by regional climate variability, which are recorded in the speleothem stratigraphy grayscale values. This study provides new evidence, based on 3 different proxies, that throughout the middle Holocene, rainfall was varying at interdecadal timescales, which I attribute to low frequency variability in ENSO and the PDO.