Kanner, L. C., Burns, S. J., Cheng, H., Edwards, R. L. and Vuille, M.: High-resolution variability of the South American summer monsoon over the last seven millennia: insights from a speleothem record from the central Peruvian Andes, Quaternary Science Reviews, 75, 1–10, doi:10.1016/j.quascirev.2013.05.008, 2013.

The stalagmite ?18O values for the Mexican samples replicate very well over the common time intervals (Fig. S2), suggesting the values have not been significantly affected by kinetic effects, a conclusion that is further supported by an observation of apparent equilibrium isotopic relationships between drip-water samples and modern aragonite precipitating in the cave.

d18O analyses conducted at the Las Vegas Isotope Science Laboratory at the University of Nevada, Las Vegas (LVIS: samples JX-2, -6, and -10) were performed with a Kiel IV automated carbonate preparation device  d18O and d13C analyses conducted at Universidad Aut�noma de Mexico (CBD-2) (?) ?18O values were corrected with an internal standard (USC-1) whose value was determined by comparison with the international standards NBS-18 and NBS-19.

The study area receives moisture from Caribbean easterly waves guided by the trade winds, tropical cyclones from the eastern Pacific and Gulf of Mexico, and Caribbean moisture that traverses the isthmus of Tehuantepec to reach southwestern Mexico via recurved trade winds over the eastern tropical Pacific. The NAM extends from southern Mexico into the southwestern United States, and is an important contributor to annual rainfall  totals due to abundant summertime convection. Our study area is dominated by a summer moisture source (supplying ?97% of annual rainfall) from the surrounding tropical oceans.

paleorainfall record of the Mesoamerican monsoon

The stalagmite ?18O values also contain a temperature imprint: a decrease in LST of ?3?4 i¿½C is responsible for making the stalagmite ?18O values higher by ?0.6?0.8% due to the water?carbonate precipitation temperature