Controls on Indo-Pacific Warm Pool Temperature

We produced the first terrestrial temperature reconstruction covering the past 60,000 years in the Indo-Pacific, a region highly susceptible to climate change and influential on global climate. The temperature reconstruction is based on the abundances of branched glycerol dialkyl glycerol tetraethers (brGDGTs), membrane-spanning lipids preserved in a sediment core from Lake Towuti, Indonesia. A comprehensive analysis of this new terrestrial temperature record, alongside all existing sea surface temperature records in the region, suggests that rising atmospheric carbon dioxide concentrations from the Last Glacial Maximum to the Holocene was likely the primary driver of warming during the last deglaciation.

Link to paper: https://doi.org/10.1029/2022PA004501

Link to data: https://doi.pangaea.de/10.1594/PANGAEA.948194​

​

Untangling precipitation proxy records in the Indo-Pacific

It has proven difficult to reconcile precipitation isotope records from the Maritime Continent in the Indo-Pacific Warm Pool with records indicating widespread drying at the Last Glacial Maximum. To investigate the signals preserved in precipitation isotope records, we compiled hydroclimate data from the Maritime Continent spanning the last deglaciation and leveraged transient climate model simulations to examine the drivers of precipitation change. During the last deglaciation, precipitation isotope, marine runoff, and salinity records show that precipitation began to increase significantly around ~12.3 ka, at the end of the Younger Dryas. Climate model simulations suggest that this increase in precipitation was associated with rising sea levels, which inundated the shallow continental shelves in the Maritime Continent and strengthened Walker Circulation over the Indian Ocean.

Link to paper: https://doi.org/10.1016/j.quascirev.2024.108755

Links to data: https://doi.org/10.1594/PANGAEA.969324, https://doi.org/10.1594/PANGAEA.969323, https://doi.org/10.1594/PANGAEA.969321, https://doi.org/10.1594/PANGAEA.969302

​

1-Myr paleoclimate records from the Maritime Continent

​In addition to the deglacial studies above, I produced 1.1-million-year temperature and precipitation records from Lake Towuti to investigate climate forcings during key transitions in glacial-interglacial cycles, including the Mid-Pleistocene Transition (~950 ka) and the Mid-Brunhes Event (~430 ka). The brGDGT-based temperature reconstruction closely tracks glacial-interglacial cycles, highlighting strong links between terrestrial and global climate throughout the late Quaternary. Meanwhile, the leaf-wax hydrogen isotope record reveals oscillations between local and global climate controls. Together, these records represent the longest continuous terrestrial climate dataset from the IPWP, offering new insights into the region’s role in global climate dynamics. This work is currently in preparation for submission to Nature Communications.

​​

Precipitation Variability in the Rocky Mountains During the Holocene

High-elevation watersheds in the Rocky Mountains are critical for maintaining year-round water supply in the western United States due to their role in snow accumulation and storage. To better understand the natural variability of precipitation in these watersheds during the Holocene, I analyzed stratigraphic records to reconstruct precipitation patterns. Using fossil pollen from lake sediment cores collected in and around the Mount Zirkel Wilderness in Colorado, I developed precipitation records spanning the past 2,500 years. Fossil pollen serves as a robust paleoclimate proxy, enabling quantitative precipitation reconstructions that can be directly compared with climate model simulations. These records revealed a significant increase in winter precipitation from the first millennium of the Common Era to the most recent millennium. If future winter precipitation decreases to levels similar to those reconstructed for the first millennium, the natural water storage capacity provided by snowpack could be substantially diminished.

Link to paper: https://doi.org/10.1017/qua.2019.85

Link to data: https://www.ncdc.noaa.gov/paleo/study/32732​

​

In addition to the pollen-based reconstructions, I produced a 7,600-year lake-level record for Silver Lake, Montana, using grain size measurements from a transect of shallow sediment cores and wave-base elevation modeling. This record revealed multi-century hydrologic fluctuations influenced by California Margin sea surface temperatures and atmospheric river events during the mid-Holocene.

Link to paper: https://doi.org/10.1017/qua.2022.17

Link to data: https://www.ncei.noaa.gov/access/paleo-search/study/36593