Collaborative Research: Paleo Records Of GLacier And Climate changes Inferred from Alaskan Lakes (PROGLACIAL)

Climate change poses a major challenge for society. More information is needed to put recent climate changes into a long-term context of natural climate variability. This information helps to foresee possible future climate trends, especially those that involve slow-moving features of the climate system, which will continue to change over hundreds to thousands of years to come.

A variety of geological evidence can be used to extend observations of temperature and other climate variables back in time. This project focuses on reconstructing glacier fluctuations in Alaska, the Arctic region of the United States, as evidence for past climate changes extending back for thousands of years. The research team will estimate past glacier size by studying sediment from glaciers that is carried by meltwater streams and deposited in glacier-fed lakes.

The sediment samples collected for this project will also be studied for signs of earthquakes and volcanic eruptions to determine how frequently these damaging events have occurred in the past and will likely occur in the future. The project will also help prepare undergraduate and graduate students for careers in the STEM workforce.

The extent of glacier cover is a prime indicator of climate. Sediments stored in glacier-fed (proglacial) lakes provide a uniquely continuous record of glacier-size fluctuations. This project will further develop the ability to reconstruct the extent of glacier cover within the catchment of proglacial lakes using basic sedimentary indicators of glacier rock-flour abundance (bulk density, organic matter, particle size, magnetic susceptibility, and accumulation rate).

By sampling proglacial lakes along an environmental gradient of heavily to sparsely glaciated catchments in Alaska, the research team will systematically acquire quantitative information about these well-known glacial indicators, which vary with glacier size and other environmental variables. This information will be used to develop a numerical model to estimate past glacier extent based on lake sediment properties measured in sediment cores taken from multiple lakes in south-central and northwest Alaska that extend back to around 15,000-years.

In addition to rock-flour indicators, the sediment will be analyzed for terrestrial and aquatic productivity indicators, including organic pigments and biogenic silica abundance, which are amenable to generating time series with decadal-scale resolution. These records will be used to address fundamental questions related to the timing and extent of climate changes in Alaska that occurred following the last major ice age.

The ages of the lake sediment will be determined using short-lived radioisotopes, volcanic ash layers, and radiocarbon dating. This project will also contribute to assessing geological hazards related to seismic and volcanic activity near the most populated area of Alaska, supporting and engaging STEM graduate and undergraduate students and early career researchers, and developing scientific resources, including the popular Alaska PaleoGlacier Atlas.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.