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Cosmogenic isotopes of helium and neon are produced at the Earth’s surface and exhibit a wide range of thermal sensitivities in common minerals. We can take advantage of this range of thermal sensitivities to reconstruct past near surface thermal conditions using cosmogenic noble gas observations. For example, cosmogenic noble gases have been used to study past ambient temperatures, changes in snow cover duration, and wildfire histories. Interpreting cosmogenic noble gas observations requires a model of both production and diffusion that predicts cosmogenic noble gas concentrations for different thermal histories. Additionally, models that characterize the diffusion kinetics of helium or neon in a particular mineral sample are often needed, as laboratory-based diffusion experiments demonstrate that helium and neon diffusion kinetics are sample specific and often complex. At present, various codes are available that can carry out pieces of the modeling, but they are generally not interoperable and are often highly specific to a particular past application, limiting the codes’ use for future applications. Here we present progress on creating a general forward modeling framework for inferring thermal histories using cosmogenic noble gas observations, structured around the concept of proxy system modeling. We will describe the architecture of this model framework as well as provide examples of applying it to new and existing cosmogenic noble gas datasets. 

The McMurdo Dry Valleys are an ice-free region along the coast of the Transantarctic Mountains that display well-preserved polar desert morphologic features, particularly at high elevations. The extent of these well-preserved features suggests that cold-desert conditions have been present for millions of years. This is thought to be because average summer air temperatures in much of the McMurdo Dry Valleys remain below -3ºC, preventing significant amounts of liquid water from forming and in turn keeping erosion rates low. Recent climate simulations suggest that these freezing temperatures persist during summer months at high elevations in the McMurdo Dry Valleys, even during past warm periods characterized by significant ice sheet recession. Surfaces at lower elevations in the McMurdo Dry Valleys, subject to warmer temperatures during warm periods and interglacials, are thought to experience overall faster erosion rates compared to high elevation outcrops. Here, we examine the relationships between elevation, temperature, and apparent surface exposure age for outcrops of the Beacon Sandstone in the McMurdo Dry Valleys. We use a compilation of cosmogenic nuclide measurements available in the ICE-D database to evaluate the correlation between apparent surface exposure age and elevation for outcrops of the Beacon Sandstone across the McMurdo Dry Valleys. At or near a number of the cosmogenic nuclide sites, local summertime ground and air surface temperature data are available from weather stations. We use these weather station data to document how ground temperatures, which ultimately control the availability of liquid water and therefore rates of surface processes, correspond with the apparent exposure ages and site elevations of Beacon Sandstone outcrops. In addition, we investigate whether field observations indicating a relationship between the coloration and surface appearance of Beacon Sandstone outcrops and the surface weathering/erosion rate can be quantified using satellite remote sensing data and the spectral properties of the outcrops. Tying all of these results together, we assess the role of temperature and other physical parameters on the rates of surface processes in the McMurdo Dry Valleys during the last few million ice-free years.