Interpreting Paleoclimate Trends from Reconstructed Glaciers In The Anaconda and Flint Ranges, SW Montana

Abstract

This project aims to interpret the paleoclimate conditions influencing former glaciers and small ice caps in the Anaconda and Flint Creek Ranges in Southwest Montana. While ice sheets encroached from Canada and significant ice caps formed on the Yellowstone Plateau and northern Rocky Mountains, the mountain ranges of western Montana were primarily occupied by valley glaciers and small ice caps. The lowering of the regional snowline 20,000 years ago during the Last Glacial Maximum (LGM) can be interpreted by reconstructing the extent, elevation, and equilibrium line altitude (ELA) of former glaciers. This project aims to interpret paleoclimate factors by comparing present day with LGM climate conditions.

This study covers two mountain ranges in Southwest Montana: the Flint Creek Range and the Anaconda Range. Eleven LGM glaciers were reconstructed across both mountain ranges by mapping trimlines, terminal and lateral moraines, and flowlines using high definition LiDAR scans. By mapping these features in ArcGIS and using a physical model of glacier profiles, the area and surface elevation of former glaciers was reconstructed. These modeled surface profiles were then used to reconstruct paleo-equilibrium line altitudes along both E-W and SW-NE trending mountain ranges in SW Montana. Reconstructed ELAs are often used to estimate shifts in paleo temperature or moisture regimes. By comparing the LGM ELAs with present day, we may see trends indicating different moisture sources present during the ice age. This study also provides paleo ELA estimates at a more refined local scale than current reconstructions covering the mountain west.