WP1: Impacts of periodic climate forcing in the Tien Shan, Kyrgyzstan
Thermochronology samples and an initial set of river terrace sampleswere collected during field expeditions in August 2021 and July 2022. Despite delays in obtaining shipping permits, all of the samples have arrived in Germany, and sample processing has started. We anticipate that the first results from both sets of samples will be available in March or April 2023.
WP2: Impacts of periodic climate forcing in the Central Andes, NW Argentina
Due to international travel restrictions during the pandemic, one Masters project was redesigned to focus on calibration of our alluvial-channel model with modern data published from the Central Andes. This work represents the first attempt to perform a field calibration of the model, which is critical for application of the model to other sites where my team is collecting new data. The student then used the calibrated model together with information from fluvial terraces (past sediment flux and past channel slope) to infer paleo-water discharge values.
Post-doctoral researcher PD2 has submitted a manuscript on his approximate analytical solutions to our alluvial-channel model to Geophysical Research Letters. With his analytical approximations, he was able to make precise predictions of how forcing with frequencies over several orders of magnitude not only affect cut-and-fill cycles and sediment-discharge signals along channels, but also predict how the amplitudes of response vary downstream, and by how much of a time lag exists between the timing of forcing and the timing of the channel response. These predictions have already helped us to better define our field sampling sites to most effectively test the model predictions. If the predictions are supported by our field observations, they will have major implications for interpreting river terraces and sedimentary archives with regards to past climate forcing, as well as enabling predictions of how future climate change will affect river-channel geometry.
Samples from the Central Andes have been processed and analyzed; a manuscript on these results will be prepared within the coming year.
WP3: Impacts of periodic climate forcing in the Patagonian Andes
Thermochronology samples and a set of river terrace samples were collected on a field expedition in March 2022, associated with projects for one PhD student and one post-doctoral researcher. Approximately 20% of the samples have been processed, and we received results that are consistent with our hypothesis that river-channel incision started around 1 million years ago. We anticipate that the next large batch of results will arrive in March or April 2023.
WP4: Project coordination, management, synthesis and outreach
The PI published a manuscript in Geochronology with a new thermal model designed for interpreting regional thermochronology datasets. The model incorporates sample-specific information in a way that makes it a powerful approach to determining exhumation rates over wide regions. Moreover, it is the only thermal model that is designed to do so efficiently on regional scales. The model has been made freely available on Zenodo as both a Matlab script and a Python script, to ensure broad access to the model. This new model will play a key role in my team's efforts to use regional thermochronology datasets to assess how and where Quaternary climate change, and specifically the Mid-Pleistocene Transition, has impacted sites in the Kyrgyz Tien Shan and the Patagonian Andes.
