Abstract
During the last ice age temperature in the North Atlantic oscillated in cycles known as Dansgaard-Oeschger (D-O) events. The magnitude of Caribbean hydroclimate change associated with D-O variability and particularly with stadial intervals, remains poorly constrained by paleoclimate records. We present a 3.3 thousand-year long stalagmite δ18O record from the Yucatan Peninsula (YP) that spans the interval between 26.5 and 23.2 thousand years before present. We estimate quantitative precipitation variability and the high resolution and dating accuracy of this record allow us to investigate how rainfall in the region responds to D-O events. Quantitative precipitation estimates are based on observed regional amount effect variability, last glacial paleotemperature records, and estimates of the last glacial oxygen isotopic composition of precipitation based on global circulation models (GCMs). The new precipitation record suggests significant low latitude hydrological responses to internal modes of climate variability and supports a role of Caribbean hydroclimate in helping Atlantic Meridional Overturning Circulation recovery during D-O events. Significant in-phase precipitation reduction across the equator in the tropical Americas associated with Heinrich event 2 is suggested by available speleothem oxygen isotope records.
Highlights
During the last ice age climate in the North Atlantic oscillated on millennial time scales from cold to warm episodes, often referred to as Dansgaard-Oeschger (D-O) events[1, 2]
We present a last glacial stalagmite δ18O record of Caribbean climate from the Yucatan Peninsula (YP), Mexico, and attempt to reconstruct quantitative precipitation variability to establish how rainfall in the region responds to D-O events and during stadial intervals
Our precipitation estimates are based on an assessment of last glacial tropical temperatures[31], shifts in the δ18O composition of precipitation suggested by global circulation models (GCMs), the observed regional amount effect[23], and the assumption that temperature dependence fractionation during calcite precipitation was according to the model by Tremaine et al.[32]
Summary
In 2012, we retrieved a 87-cm long stalagmite specimen, named Itzamna (after the Maya god of creation), from Río Secreto Natural Reserve, a spectacular semi-inundated cave system located in Playa del Carmen City, in the Caribbean coast of the YP (20°35.244′N; 87°8.042′W) (Supplementary Fig. S1). The Itzamna precipitation record suggests a significant long-term drying trend that began approximately 24.5 ka BP, following estimated precipitation mean maximum levels of + 150% and humid conditions in Central America[6, 55] This drying trend ended about 23.2 ky ago when mean precipitation declined by about 50% (based on the average of the three most recent data points) and the stalagmite Itzamna became ‘dormant’ for 20 thousand years. Hosing experiments based on atmosphere–ocean general circulation models suggest that freshening of the North Atlantic and the ensuing AMOC slowdown and atmospheric cooling would cause significant precipitation reduction in the American tropics, including the Caribbean and Amazon basin[16, 17]. Speleothems from tropical regions may represent our best chance to reconstruct low latitude precipitation variability and its sensitivity to shifts in climate boundary conditions (e.g. greenhouse gases) and processes internal to the climate system (e.g. AMOC)
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