Aaron Coutino | Applied Math, University of Waterloo
Stability of the Yucatan aquifer and modeling variability in sediment paleo-records
The availability of freshwater is a basic prerequisite for civilization. Classical civilizations, such as the Maya, had to face the problem of ensuring sufficient water for their people. This is particularly important in karst landscapes, such as that of the Yucatan peninsula, Mexico, since there is a general absence of large rivers and lakes (Bauer-Gottwein et al., 2011). Indeed, due to the porous nature of the local geology, freshwater is contained either in small lakes or within the subterranean aquifer which can only be accessed via openings that lead into cave networks. Climate variability (specifically heavy rainfalls and droughts) on the decadal and sub-decadal time-scales has been posited to have been a major driving force behind the decline of the Mayan city-states during the Terminal Classical period (Kennett et al., 2012).
The aquifer in this region is comprised of a freshwater lens near the surface that overlays a layer of seawater that intrudes from the coast (Bauer-Gottwein et al., 2011). In my masters’ thesis work (Coutino et al., 2017) we showed through sensor measurements of salinity and temperature from 2011-2013 that hurricanes passing through the region resulted in the marine water mixing with the freshwater lens. For my doctoral work we propose to build off our novel result and use it to inform results from sediment core records. Trace element analysis on the sediment cores returns a time series record that requires a careful balance between mathematical methods that efficiently provide information for episodic events (e.g. wavelet analysis and wavelet coherence) and an understanding of the underlying scientific questions to which we are uniquely suited. Based on the results from the sensor measurements, increases in hurricane activity appear to correspond with an increase in salinity of the upper freshwater lens. The converse would then appear to indicate that during periods of low rainfall the freshwater lens will settle and result in a decrease in salinity. This would be a major result that would impact the current discussion on the decline of the Mayan civilization. Current results from sediment records within this upper lens appear to agree with this assessment, however research is ongoing.
As a result of the recent discoveries of human remains within the cave networks of the Yucatan aquifer there is a flurry of interest in understanding the Yucatan aquifer and modeling past climate in the region.