Abstract
AbstractMountain glaciers integrate climate processes to provide an unmatched signal of regional climate forcing. However, extracting the climate signal via intercomparison of regional glacier mass-balance records can be problematic when methods for extrapolating and calibrating direct glaciological measurements are mixed or inconsistent. To address this problem, we reanalyzed and compared long-term mass-balance records from the US Geological Survey Benchmark Glaciers. These five glaciers span maritime and continental climate regimes of the western United States and Alaska. Each glacier exhibits cumulative mass loss since the mid-20th century, with average rates ranging from −0.58 to −0.30 m w.e. a−1. We produced a set of solutions using different extrapolation and calibration methods to inform uncertainty estimates, which range from 0.22 to 0.44 m w.e. a−1. Mass losses are primarily driven by increasing summer warming. Continentality exerts a stronger control on mass loss than latitude. Similar to elevation, topographic shading, snow redistribution and glacier surface features often exert important mass-balance controls. The reanalysis underscores the value of geodetic calibration to resolve mass-balance magnitude, as well as the irreplaceable value of direct measurements in contributing to the process-based understanding of glacier mass balance.
Highlights
Implications of glacier mass loss span global (Gardner and others, 2013; Marzeion and others, 2017; Zemp and others, 2019) to local scales (e.g. Moore, 1992; O’Neel and others, 2015; Sass and others, 2017; Schoen and others, 2017)
We selected a preferred solution in a floating-date ‘stratigraphic’ time system designed to quantify the duration of the accumulation and ablation seasons and to keep mass changes from any given season within a single mass-balance year
Average mass loss rates range from −0.28 to −0.58 m w.e. a−1, with uncertainty ranging between ±0.22 and 0.42 m w.e. a−1 (Table 2)
Summary
Implications of glacier mass loss span global (Gardner and others, 2013; Marzeion and others, 2017; Zemp and others, 2019) to local scales (e.g. Moore, 1992; O’Neel and others, 2015; Sass and others, 2017; Schoen and others, 2017). USGS initiated a mass-balance program at Washington’s South Cascade Glacier as part of the IGY (Meier, 1958), which was the first step towards a long-term programmatic effort to document and understand glacier-climate linkages. We include mass-balance data from southeast Alaska’s Lemon Creek Glacier, traditionally maintained by the Juneau Icefield Research Program (JIRP). This glacier fills the geographic gap between the glaciers of the contiguous USA and mainland Alaska, prompting USGS to initiate seasonal mass-balance observations that augment the ongoing JIRP’s summer-season efforts (Pelto and others, 2013). The study glaciers span the primary North American climate regimes that support glaciers: midlatitude maritime, midlatitude continental, high-latitude maritime and high-latitude continental (Fig. 1a)
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