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. 2017 Sep 11;7:11216. doi: 10.1038/s41598-017-11742-8

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© The Author(s) 2017

Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/.

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Itzamna δ¹⁸O (panel B) and δ¹⁸O-derived precipitation (panel C) records spanning the time interval between 26.4 and 23.2 ka BP from Rio Secreto, Playa del Carmen, Mexico. Precipitation percent change estimates are relative to the mean annual precipitation amount in Playa del Carmen today of 1465 mm (panel B). These records have a resolution during the time interval between 26.5 and 24.6 ka BP of 3.4 ± 1.3 years (1 SD) and between 24.6 and 23.2 ka BP of 16 ± 6.7 years (1 SD). Precipitation change estimates (blue shading) reflect reference values of calcite precipitated under isotopic equilibrium conditions with last glacial dripwater temperature (18–20 °C) and an amount effect (δP/ΔP) ranging from −0.0168‰ per mm to −0.0106‰ per mm, corresponding to the 80% confidence interval of the amount effect slope based on instrumental data (see Methods section for more details). Average precipitation change is indicated by the blue the line within blue shading. Reference equilibrium values were calculated using the paleotemperature equation by ref. 32. The potential bias in our precipitation estimates due to shifts in annual precipitation amount seasonality is ±8% in the range of 55 to 70% summer contribution to annual precipitation (see Methods section). Vertical box on the left of panel B; indicates precipitation variability observed today in the northeast of the YP (mean = 1390 mm per year; range 670 mm to 2664 mm per year), based on the longest continuous instrumental record of precipitation available for this region (i.e. Kantunilkil Station)²¹. The record covers Stadial 2 and Heinrich event 2 (H2). Vertical grey bars reflect the two peak IRD depositional phases associated with H2, centered at 25 ± 0.2 ka BP and 23.5 ± 0.2 ka BP¹³. The six significant positive δ¹⁸O shifts discussed in the manuscript are indicated with numbers. Top image (panel A), represents a wavelet spectral power analysis of the Itzamna δ¹⁸O record. The area outside the white lines indicates the cone of influence where the edge effects of the wavelet transform and uncertainties become important and the black contours reflect statistically significant power spectra (CI = 95%). Wavelet spectral power is based on methods by refs 73, 74, as implemented in the R package “biwavelet”⁷².