Abstract
AbstractWe reanalyzed mass balance records at Taku and Lemon Creek Glaciers to better understand the relative roles of hypsometry, local climate and dynamics as mass balance drivers. Over the 1946–2018 period, the cumulative mass balances diverged. Tidewater Taku Glacier advanced and gained mass at an average rate of +0.25 ± 0.28 m w.e. a–1, contrasting with retreat and mass loss of −0.60 ± 0.15 m w.e. a−1 at land-terminating Lemon Creek Glacier. The uniform influence of regional climate is demonstrated by strong correlations among annual mass balance and climate data. Regional warming trends forced similar statistically significant decreases in surface mass balance after 1989: −0.83 m w.e. a–1 at Taku Glacier and −0.81 m w.e. a–1 at Lemon Creek Glacier. Divergence in cumulative mass balance arises from differences in glacier hypsometry and local climate. Since 2013 negative mass balance and glacier-wide thinning prevailed at Taku Glacier. These changes initiated terminus retreat, which could increase dramatically if calving begins. The future mass balance trajectory of Taku Glacier hinges on dynamics, likely ending the historic dichotomy between these glaciers.
Highlights
Mountain glacier mass loss rates in the Alaska region are among the highest on Earth (Gardner and others, 2013; Zemp and others, 2019)
We show that our results generally agree with previous studies at both glaciers (e.g. Larsen and others, 2007; Criscitiello and others, 2010; Pelto and others, 2013; Berthier and others, 2018), but have reduced and constrained uncertainty
This study revealed significantly different annual mass balances, with a mean of +0.25 ± 0.28 m w.e. a−1 at tidewater Taku Glacier and −0.60 ± 0.15 m w.e. a−1 at land-terminating Lemon Creek Glacier during the 1953–2018 period
Summary
Mountain glacier mass loss rates in the Alaska region are among the highest on Earth (Gardner and others, 2013; Zemp and others, 2019). Glaciological records form the only annual observations of glacier mass change prior to the satellite era, yet comparisons among these records, and to remote sensing or model outputs, are limited by methodological inconsistencies (Zemp and others, 2013). This motivates the consistent, repeatable approach for basin-scale annual glacier surface mass balance that we developed and used to interpret the divergent histories of Taku and Lemon Creek Glaciers. Reanalysis identifies and corrects bias identified by comparison of glaciological and geodetic measurements, often incorporates previously unavailable data or methods, and presents a thorough error analysis (Cogley and others, 2011). Such synthesis allows long-term trends to be constrained by geodetic analyses while interannual variations are determined from glaciological observations (Cox and March, 2004)
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