LIA Geomorphology of the Brooks Range, USA

Global and regional estimates of glacier mass and area change are poorly constrained prior to 2000 due to a lack of data, particularly in high latitude areas. This impedes our ability to comprehend and contextualise observed glacier mass loss, particularly when investigating changing rates of mass loss. This can be resolved by extending the glacial record back in time, to improve understanding of how glaciers have changed in this region under a longer-term time series of climatic change. The geomorphological reconstruction presented here will form part of a larger project, incorporating geomorphology, photogrammetry and modelling techniques to accurately constrain and project Brooks Range glacial change.
This study aims to investigate the glacial geomorphology of the Brooks Range, Alaska, and to reconstruct glacier behaviour since the “Little Ice Age” (LIA), by reconstructing the LIA glacial maximum and comparing it to various temporal points between then and 2022 AD. We use mapped glacial features to infer LIA glacier outlines and calculate their approximate area. In some areas, glacier outlines digitised from topographic maps are available and were used as timestamps to correlate glacial features with their approximate age, as well as to evaluate changing rates of glacier wastage between LIA inferred outlines and 2022 AD outlines. We derive 2022 AD glacier outlines from Sentinel-2 imagery, using a band ratio method to automatically identify glaciers followed by vectorisation and manual editing to produce a Brooks Range glacier database. Generation of these outlines enables quantification of glacier area change from the LIA to 2022 AD, as well as higher accuracy in the modelling phase of the larger project.
Our new geomorphic maps will allow us to derive glacier area change across the Brooks Range, and constrain rates of change to analyse how Brooks Range glaciers are responding to changing climatic forcings in the region. This will enable insights into the style and manner of the neoglaciation and deglaciation in the Brooks Range. Further, the results of this investigation will be used to inform the methods used as part of the larger project.