Topographic controls on ice flow and recession for Juneau Icefield (Alaska/British Columbia)

Globally, mountain glaciers and ice caps are losing dramatic volumes of ice. The resultant sea‐level rise is dominated by contributions from Alaska. Plateau icefields may be especially sensitive to climate change due to the non‐linear controls their topography imparts on their response to climate change. However, Alaskan plateau icefields have been subject to little structural glaciological or regional geomorphological assessment, which makes the controls on their present and former mass balance difficult to ascertain. We inventoried 1050 glaciers and 368 lakes in the Juneau Icefield region for the year 2019. We found that 63 glaciers had disappeared since the 2005 inventory, with a reduction in glacier area of 422 km2 (10.0%). We also present the first structural glaciological and geomorphological map for an entire icefield in Alaska. Glaciological mapping of >20 800 features included crevasses, debris cover, foliation, ogives, medial moraines and, importantly, areas of glacier fragmentation, where glaciers either separated from tributaries via lateral recession (n = 59), or disconnected within areas of former icefalls (n = 281). Geomorphological mapping of >10 200 landforms included glacial moraines, glacial lakes, trimlines, flutes and cirques. These landforms were generated by a temperate icefield during the Little Ice Age (LIA) neoglaciation. These data demonstrate that the present‐day outlet glaciers, which have a similar thermal and ice‐flow regime, have undergone largely continuous recession since the LIA. Importantly, disconnections occurring within glaciers can separate accumulation and ablation zones, increasing rates of glacier mass loss. We show that glacier disconnections are widespread across the icefield and should be critically taken into consideration when icefield vulnerability to climate change is considered. We provide a detailed glaciological and geomorphological map that outlines the neoglacial geomorphology and contemporary glaciology (in 2019 AD) of Juneau Icefield, USA/Canada. The contiguous area of the icefield, which included 218 outlet, valley glacier and mountain glaciers, was 3251.3 km2 in 2019. Together with the Icefield's surrounding peripheral glaciers, the study area included 1050 glaciers, covering 3816.4 km2. This plateau icefield is susceptible to non‐linear and threshold behaviour that will accelerate its response to climate change, including ‘disconnections’ between glacier accumulation and ablation areas as ice thin