Orbital scale paleohydrological changes in the subtropical Mexico since MIS 5 and possible forcings

Abstract:

In Mexico, there are only two proxy records that provide information about the last interglacial. Lack of longer registers is a hindrance in understanding the effect of modern era global warming on the arid ecosystem of northern Mexico. We present a new orbital-scale record of hydrological changes occurred since the MIS 5 from the southern part of subtropical Mexico. This record is obtained from geochemistry of a 10 m long sediment core collected from central part of the Santiaguillo Basin. The age model is created with radiocarbon dates of sediments deposited over the last 27 cal ka and it incorporates a uniform sedimentation rate (calculated for the last 27 cal ka) for lower part of the core. Variation of runoff is reconstructed from Ti concentration and salinity of the water column is inferred from the abundance authigenic carbonates. Over the last 27 cal ka, this new record shows similar variations as that of our previous work done in sediment profiles collected from the littoral parts of the basin. We observe a first order positive correlation between the proxy records of runoff and lake water salinity with insolation values for the interpolated as well as the extrapolated parts of age model. The runoff record has orbital-scale similarities with autumn (September) insolation and variations in lake water salinity are comparable to summer (June) insolation. Santiaguillo Basin received more runoff (i.e. precipitation) during the intervals of higher autumn insolation and more carbonate deposition occurred (i.e. drought) during the intervals of higher summer insolation. During MIS 5, the hydrological variations were controlled by the insolation values. In general, MIS 4 and MIS 2 were intervals of more runoff and more carbonate deposition occurred during MIS 3. Comparison with other regional records suggests different geographic influences of NAM and Tropical Cyclones in orbital-scales.