Local topography increasingly influences the mass balance of a retreating cirque glacier

Abstract

Abstract. Local topographically driven processes – such as wind drifting, avalanching, and shading – are known to alter the relationship between the mass balance of small cirque glaciers and regional climate. Yet partitioning such local effects from regional climate influence has proven difficult, creating uncertainty in the climate representativeness of some glaciers. We address this problem for Sperry Glacier in Glacier National Park, USA, using field-measured surface mass balance, geodetic constraints on mass balance, and regional climate data recorded at a network of meteorological and snow stations. Geodetically derived mass changes during 1950–1960, 1960–2005, and 2005–2014 document average mass change rates during each period at −0.22 ± 0.12, −0.18 ± 0.05, and −0.10 ± 0.03 m w.e. yr−1, respectively. A correlation of field-measured mass balance and regional climate variables closely (i.e., within 0.08 m w.e. yr−1) predicts the geodetically measured mass loss from 2005 to 2014. However, this correlation overestimates glacier mass balance for 1950–1960 by +1.20 ± 0.95 m w.e. yr−1. Our analysis suggests that local effects, not represented in regional climate variables, have become a more dominant driver of the net mass balance as the glacier lost 0.50 km2 and retreated further into its cirque.

ImpDAR: an open-source impulse radar processor

“…The equilibrium line is located at ~0.375 km, but surprisingly, the profile shows accumulation below this elevation and ablation above; previous summer surfaces ascend toward this point from the left, and the lack of discernable structure below this surface to the right is indicative of temperate ice. Similarly, non-elevation-dependent patterns of mass balance have been previously observed on South Cascade Glacier (Meier and Tangborn, 1965), where in low snow years, accumulation may be confined to the southwest margin due to topographic shielding from the surrounding mountains, and previous work has shown accumulation to be highly dependent on surrounding topography on another comparable alpine glacier (Brown and others, 2010; Florentine and others, 2018). In addition to summer surfaces, several crevasses and possible meltwater inclusions are visible in the temperate ice on the right side of the profile, and the steeply dipping bed, which is overlain in the field by a notable bergschrund, is visible at the far right.…”

Variations in surface area of six ice aprons in the Mont-Blanc massif since the Little Ice Age

“…Hoffman and others (2007) and DeBeer and Sharp (2009), among others, demonstrated the importance of accounting for local mass-balance drivers in variations of ice masses. Local topography is a documented factor contributing to the persistence of small glaciers lying under the regional ELA (Florentine and others, 2018). Here, we suggest that local topography mitigates ice apron persistence, especially for Lower Grandes Jorasses and Upper Tour Ronde.…”

Glacier mass and area changes on the Kenai Peninsula, Alaska, 1986–2016

“…Approximately 270 glaciers (all <0.5 km 2 ) disappeared during 1986–2016. Larger retreat rates of smaller glaciers can be attributed to a stronger impact of local topographic characteristics on the processes controlling the glacier mass balance (Florentine and others, 2018). For example, a moderate rise in the equilibrium line may turn the entire glacier to ablation zone (Kaser and Osmaston, 2002; Racoviteanu and others, 2008 b ).…”