Geometry, mass balance and thinning at Eklutna Glacier, Alaska: an altitude-mass-balance feedback with implications for water resources

Sass, Louis C.; Loso, Michael G.; Geck, Jason; Thoms, Evan E.; McGrath, D.

doi:10.1017/jog.2016.146

Cited by 13 publications

(27 citation statements)

References 46 publications

(65 reference statements)

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“…The terminus area fed by the west branch (sites X, W, T) retreated more than 1 km since 1993 and is in the process of fragmenting and disconnecting from the main trunk of the glacier. In contrast, the main trunk (sites B, D, V), characterized by lower surface slopes and overdeepened ice, has thinned but retreated only ~650 m. We expect continued retreat from the disconnecting lobe, which will likely contrast the overdeepened trunk that is more susceptible to altitude-mass-balance feedbacks, as observed across other low-sloping Alaska glaciers (Sass and others, 2017). This divergent response to the same climate highlights the complex nature of linkages among mass balance, glacier geometry, response time and regional climate forcing.…”

Section: Discussionmentioning

confidence: 58%

“…The highest quality DEM in each time series is designated as the ‘reference,’ with which all other DEMs were aligned (Table 1). Once co-registered, DEMs were differenced from the reference DEM to yield elevation change across the glacier surface (Shean and others, 2016; Sass and others, 2017). Voids in the difference map exceeding 5% of the glacier surface were filled using a regression between the change in surface elevation and the reference surface elevation (Larsen and others, 2015).…”

Section: Discussionmentioning

confidence: 99%

“…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). Yet resolving regional patterns of mountain glacier mass loss remains challenging (e.g.…”

Section: Introductionmentioning

confidence: 99%

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Reanalysis of the US Geological Survey Benchmark Glaciers: long-term insight into climate forcing of glacier mass balance

et al. 2019

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Mountain 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.

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Section: Discussionmentioning

confidence: 58%

Section: Discussionmentioning

confidence: 99%

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Reanalysis of the US Geological Survey Benchmark Glaciers: long-term insight into climate forcing of glacier mass balance

et al. 2019

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“…Each co-registered DEM was bilinearly resampled to the coarsest resolution DEM, then differenced from the reference DEM (Table 1) to calculate the average surface elevation change (Shean and others, 2016; Sass and others, 2017) over the glacier larger area between each DEM pair. DEMs with unresolved glacier areas >5% (due to low snow contrast; Table 1) were interpolated using an empirical relationship between elevation change in respect to the reference DEM's elevation (Fig.…”

Section: Methodsmentioning

confidence: 99%

Explaining mass balance and retreat dichotomies at Taku and Lemon Creek Glaciers, Alaska

et al. 2020

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We 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.

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“…Interval photography documented phenology of red snow. The alpine Eklutna Glacier has undergone mass-balance study since 2008 42 . An AWS on the glacier surface near the mass-balance equilibrium-line elevation (1,391 m asl) sampled melt variables hourly (2 May-20 August 2014).…”

Section: Methodsmentioning

confidence: 99%

The role of microbes in snowmelt and radiative forcing on an Alaskan icefield

et al. 2017

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A lack of liquid water limits life on glaciers worldwide but specialized microbes still colonize these environments. These microbes reduce surface albedo, which, in turn, could lead to warming and enhanced glacier melt. Here we present results from a replicated, controlled field experiment to quantify the impact of microbes on snowmelt in red-snow communities. Addition of nitrogen-phosphorous-potassium fertilizer increased alga cell counts nearly fourfold, to levels similar to nitrogen-phosphorusenriched lakes; water alone increased counts by half. The manipulated alga abundance explained a third of the observed variability in snowmelt. Using a normalized-di erence spectral index we estimated alga abundance from satellite imagery and calculated microbial contribution to snowmelt on an icefield of 1,900 km 2 . The red-snow area extended over about 700 km 2 , and in this area we determined that microbial communities were responsible for 17% of the total snowmelt there. Our results support hypotheses that snow-dwelling microbes increase glacier melt directly in a bio-geophysical feedback by lowering albedo and indirectly by exposing low-albedo glacier ice. Radiative forcing due to perennial populations of microbes may match that of non-living particulates at high latitudes. Their contribution to climate warming is likely to grow with increased melt and nutrient input.G lacier ablation is sensitive to changes in albedo 1 , with atmospheric 2,3 , hydrological 4 and ecological 5,6 consequences. Fresh snow reflects >90% of visible radiation, but during melt its grain size and water content increase, reducing albedo and further increasing snowmelt 1 . Impurities, including black carbon 3 , dust 4 , and resident microbes [7][8][9][10][11][12][13][14][15][16][17][18][19] , also lower albedo; however, microbes differ from non-living particulates in several critical ways. Perennial populations of photosynthetic microbes actively resurface following overwinter burial by snow 20 , and depend on liquid water and nutrients for survival and reproduction 13,14,[20][21][22] . This requirement for liquid water in a frozen environment imposes a selective force favouring a physiology that increases melt proximal to cell walls. The generation of meltwater through microbes' albedoreducing properties motivates an hypothesis of bio-geophysical feedback on glacial landscapes 13,16 , such as the Greenland ice sheet. This feedback hypothesis, whereby microbes increase because they produce needed meltwater, is an active research area [13][14][15][16][17][18][19] , yet field experiments testing its assumptions are absent.Glacier microbiomes are water-limited 21,22 , because ice is generally not metabolically available, and oligotrophic, because their nutrient content equals that of precipitation plus deposition by airborne dust, pollen, and so on, with only limited N-fixation by local cyanobacteria 21,22 . Moreover, rapidly percolating water through large-grained snow may exacerbate both water-and nutrient limitation for algae in supraglacial...

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Geometry, mass balance and thinning at Eklutna Glacier, Alaska: an altitude-mass-balance feedback with implications for water resources

Cited by 13 publications

References 46 publications

Reanalysis of the US Geological Survey Benchmark Glaciers: long-term insight into climate forcing of glacier mass balance

Reanalysis of the US Geological Survey Benchmark Glaciers: long-term insight into climate forcing of glacier mass balance

Explaining mass balance and retreat dichotomies at Taku and Lemon Creek Glaciers, Alaska

The role of microbes in snowmelt and radiative forcing on an Alaskan icefield

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