NSFGEO-NERC: Collaborative Research: MexiDrill: Developing a 350,000 year record of climate and environmental change in tropical North America

The primary scientific objective of this joint NSF-GEO/NERC proposal is to obtain a continuous, high-resolution record of past changes in climate and volcanism in the Mexico City region over the last 350,000 years. We will analyse a recently recovered ~350 metre-long core from the Lake Chalco basin on the southern outskirts of Mexico City. This sediment sequence will be among the longest archives of climate, environment, and biota from a region presently lacking such records. Information obtained from these cores will help understand the mechanisms that caused past climate shifts, which is critical for evaluating impacts of ongoing and future climate change. Mexico is projected to become drier in the coming decades-centuries in response to ongoing climate change, and these anthropogenic changes will be superimposed on natural variability in climate systems that are not fully understood. This project will extract information on the temperature and precipitation over the last 350,000 years to evaluate the drivers of the climate. The Chalco sedimentary sequence also provides a unique record of the explosive volcanism in the Mexico City region, with ash from more than 150 volcanic eruptions preserved. These volcanic ash layers are likely to be from the major stratovolcanoes that surround Mexico City and the extensive monogenetic field situated in the southern part of the city. We will use these eruption deposits to obtain a chronology for the core and establish the magnitude and frequency of past eruptions. This information on the long-term history of these volcanoes will be invaluable for hazard and risk assessments for this densely populated region.

Sediments from Lake Chalco hold geologic, paleoenvironmental, and palaeobiological information of value to the global scientific community, and directly relevant to the >20 million people living in the Basin of Mexico. Results of this project will contribute to an improved understanding of climate and hydrological balance in one of the most densely populated urban centers on Earth. Hydrological balance impacts agriculture and drinking water as well as affecting vulnerability to disease. We will feed this information back to the authorities through our colleagues at the National Autonomous University of Mexico (UNAM) in Mexico City.

Our work will provide an improved fundamental understanding of the rates of past volcanism, and impacts of past eruptions of the volcanoes in and around Mexico City. We will work with our colleagues at UNAM to inform revised assessments of volcanic hazard and risk. These assessments will be used by National Civil Protection System (SINAPROC) to develop evacuation plans, for future eruption scenarios; and are used to inform long term urban and infrastructure planning.

Residents of Mexico City, including visitors to the region, tour guides and tourist agencies; and people generally interested in climate and volcanoes will all benefit from the additional knowledge of the past climate and the eruption histories of the volcanoes surrounding Mexico City. For public outreach, our team will: 1) incorporate field guides from Mexico into the 'Flyover Country' mobile app, which will be available in English and Spanish, and 2) develop a half hour documentary for broadcast on the USA Pubic Broadcasting Service (PBS) network and dissemination through various educational channels.