NOAA/WDS Paleoclimatology - Rasmussen et al. 2006 Carlsbad Caverns/Hidden Cave Stalagmite Band Thickness Data

The mechanisms driving late Holocene drought cycles in the western
United States are not well known due to the general scarcity of long-
term, high-resolution, absolutely dateable proxies for precipitation
in continental interiors. Here we show that late Holocene precipitation
variability in the southwestern United States has been caused by
changes in the Pacific Ocean. We present a stalagmite-based, annually
resolved moisture record that indicates large shifts from pluvial to
drought conditions alternating with periods of dampened, near-average
precipitation over the last 3000 years. Significant spectral peaks
at decadal-scale (~20-50, 70-80 year) frequencies likely correspond
to modern frequencies of the Pacific Decadal Oscillation or a low-
frequency component of the El Niño-Southern Oscillation, and are
dominant during episodes of large precipitation shifts.
Overall pluvial conditions punctuated by severe droughts may have
challenged the adaptive capacities of emerging agrarian communities
of ancestral Americans.