BACKGROUND

About CoNTESTA:

Climate change is the greatest challenge we face. Robust adaptation and mitigation measures depend upon a strong understanding of the Earth’s climate system and accurate projections of its future behaviour. Reconstructing the spatial and temporal pattern of past climate change is a proven tool for establishing how Earth’s climate system operates over time and under differing boundary conditions. These efforts requires a wide array of high-resolution climate proxies that are themselves well understood and easily interpretable.

Glaciers respond sensitively to changes in climate and leave a record of these changes on the landscape in the form of moraines. Given chronologic control, these records can be used to reconstruct past climate variability. Recent advances in a technique called cosmogenic nuclide surface-exposure dating now enable just this, placing past glacier fluctuations within greater climatic context and establishing these fluctuations as a key climate proxy.

In locations where glaciers have left a detailed record of past changes in extent, these geomorphic markers can be used to determine the timing and magnitude of past change throughout high-interest intervals, including periods of abrupt climate change during the last glacial period (30-11 kyr). However, to make full use of the glacial-geomorphic record for climate reconstruction we must overcome a fundamental methodological uncertainty in cosmogenic-nuclide surface-exposure dating: the uncertain rate of change of cosmogenic nuclide production over time. The primary uncertainty surrounding nuclide production rests in the potential impact of Earth's changing magnetic field on nuclide production over time. These uncertainties are greatest within the tropics, as Earth's magnetic field theoretically impacts the incoming cosmic ray flux most severely within the low latitudes.

CoNTESTA is using the landscape of southern Peru, and in particular its many lava flows, to establish multiple cosmogenic nuclide production rates of varying age from a single region of the tropics.

This project represents the first systematic, geologic evaluation of cosmogenic nuclide production through time, and the methodologies used to calculate surface-exposure ages for samples which fall beyond the direct scope of existing production rate calibrations. The results of this project will yield results that will improve our ability to assess the timing and magnitude of past landscape and climate change, thus improving our understanding of the climate system as a whole and the imapcts of climate change through time.