NOAA/WDS Paleoclimatology - Reuter et al. 2009 Cascayunga Cave, Peru 1000 Year d18O Data

An absolute dated speleothem oxygen isotope (d18O) record
from northeastern Peru documents monsoon precipitation
variability over northern South America during the past
that 1000 years and indicates the annual precipitation
in the 15th through the 18th centuries, the so-called
Little Ice Age (LIA), was on average ~10% higher than
during the 20th century. Over the 20th century recurrent
modes of seasonal rainfall variability across northern
South America were associated with discrete sea surface
temperature anomaly patterns within the Atlantic and
Pacific Oceans. Calling upon these SST-rainfall
teleconnectivity patterns, and paleo-SST reconstructions
that span the past 8 centuries, higher annual rainfall
across northern South America during the LIA is attributed
to cooler boreal spring SSTs in the tropical North Atlantic.
Weaker co-variance between north Atlantic SSTs and the
South American Monsoon System (SAMS) rainfall during
the 20th century suggests that ENSO has become a more
dominant influence than it was during the LIA.