Chilibrillo Cave, Panama Speleothem Stable Isotope Data

The effect of the El Niño/Southern Oscillation (ENSO) on tropical rainfall variations of the past two millennia is largely unknown. High-resolution monsoon records are sparse, despite the role of ENSO in generating global hydrologic anomalies in modern climate. To investigate the relationship between ENSO and the Central American Monsoon, we generated a high-resolution (~2.9 yr/sample) oxygen-isotope monsoon rainfall record from a U/Th-dated stalagmite (180 B.C. to 1310 A.D.) from the Isthmus of Panama. We present evidence for a weakened monsoon during the "High Medieval" (1100 - 1200 A.D.) and the Classic Maya Collapse (750 - 950 A.D.). Rainfall decreased and was more variable after 550 A.D., and the period 900 - 1310 A.D. was drier than the preceding millennium. A weaker monsoon corresponds with increased El Niño variability, and our data display statistical variance in the ENSO band. We conclude that ENSO variation has forced isthmian rainfall and may have contributed to hemispheric climatic anomalies at this time.

A 1500-year El Niño/Southern Oscillation and rainfall history for the Isthmus of Panama from speleothem calcite

In tropical regions where rainfall is dominated by strong vertical convection, rainfall d18O values are inversely correlated with rainfall amount via the amount effect

rainfall d18O values are inversely correlated with rainfall amount via the amount effect

Fritz, Sherilyn C.; Engstrom, Daniel R.; Grimm, Eric

<jats:title>Abstract</jats:title>
            <jats:p>Reconstructions of lake-water salinity at decadal resolution for the last 2000 yr are compared among three lakes in North Dakota to infer regional patterns of drought. The intersite comparisons are used to distinguish local variation in climate or hydrology from regional patterns of change. At one lake, diatom-inferred salinity and lake-water Mg/Ca inferred from ostracode shell chemistry are coherent, both in terms of direction and magnitude of change, indicating that each is a robust technique for reconstructing lake-water chemistry. The data show that the last 2000 yr have been characterized by frequent shifts between high and low salinity, suggesting shifts between dry and moist periods. Long intervals of high salinity suggest periods of multiple decades when droughts were intense and frequent, thus indicating times when drought was more persistent than in the 20th century. Both the Medieval Period and Little Ice Age were hydrologically complex, and there is no clear evidence to suggest that either interval was coherent or unusual in effective moisture relative to long-term patterns. Differences among the three sites may be attributed to variation in local hydrology, and these differences emphasize the need for multiple sites in deriving regional climate interpretations from paleoecological data.</jats:p>