MULTI-PROXY ANALYSIS OF ALASKAN LOESS DEPOSITS THROUGH QUATERNARY INTERGLACIAL-GLACIAL CYCLES

The Arctic is currently warming at least twice as fast as the rest of Earth. This warming drives glacier retreat, while melting permafrost releases additional greenhouse gases, further amplifying warming. Climate records from past warm periods provide context for ongoing changes. Such records are rare in the north because ice sheets covered much of this region during glaciations, scouring the landscape and removing sediments. This has led to a critical gap in understanding how current changes relate to those in past warmer conditions.

Beringia, comprising Alaska, the Yukon Territory, and eastern Siberia, was not blanketed by ice sheets during glaciations. Throughout Beringia, loess (wind-blown dust) accumulated in thick sections that provide near-continuous climate archives spanning the past 3 million years. During a National Geographic-funded expedition in summer 2019, we collected loess and paleosol samples from Gold Hill and the Largent Mine near Fairbanks, Alaska. We will present stratigraphy and age control at these sites, which contain paleosols from at least three interglacial periods. We will also present multiple paleoclimate proxies measured in the paleosols and adjacent loess (deposited during glacial periods). These proxies include magnetic susceptibility, loss on ignition, leaf wax chain length distributions and hydrogen isotopes, and glycerol dialkyl glycerol tetraethers (GDGTs). Leaf wax distributions reflect plant community changes through time while leaf wax hydrogen isotopes reflect changes in the water cycle through time. Magnetic susceptibility and loss on ignition reflect soil maturity and primary production.

We will compare climate between these interglacial periods and assess this region’s response to forcing mechanisms during ancient interglacials, including insolation and CO2. Our results will elucidate how high-latitude climate responds to global warmth, while laying the groundwork for future detailed analyses of samples in this same area.