Juneau Icefield Mass Balance Program 1946–2011

Pelto, Mauri; Kavanaugh, Jeffrey L.; McNeil, Christopher J.

doi:10.5194/essd-5-319-2013

Cited by 34 publications

(58 citation statements)

References 19 publications

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“…2a), exhibiting supraglacial channels that draw water from a layer of weathered, partially melted surface ice (e.g., Müller and Keeler, 1969). In the time frame of our study (4-7 August 2010), we observed the transient snow line (TSL) at elevations ∼ 75-100 m higher than our study site, implying ∼ 3 weeks of bare ice exposure prior to our study if TSL migration rates measured at other glaciers on the Juneau Icefield (∼ 4-5 m day −1 in August 2010, Pelto, 2011;Pelto et al, 2013) are also assumed for our site. Fractures and crevasses in this ice-marginal area are rare, with spacing much larger than typical stream spacing.…”

Section: Site Summary and Methodsmentioning

confidence: 50%

Near-surface permeability in a supraglacial drainage basin on the Llewellyn Glacier, Juneau Icefield, British Columbia

2014

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Abstract. Supraglacial channel networks link time varying melt production and meltwater routing on temperate glaciers. Such channel networks often include components of both surface transport in streams and subsurface porous flow through near-surface ice, firn or snowpack. Although subsurface transport if present will likely control network transport efficacy, it is the most poorly characterized component of the system. We present measurements of supraglacial channel spacing and network properties on the Juneau Icefield, subsurface water table height, and time variation of hydraulic characteristics including diurnal variability in water temperature. We combine these data with modeling of porous flow in weathered ice to infer near-surface permeability. Estimates are based on an observed phase lag between diurnal water temperature variations and discharge, and independently on measurement of water table surface elevation away from a stream. Both methods predict ice permeability on a 1-10 m scale in the range of 10 −10 -10 −11 m 2 . These estimates are considerably smaller than common parameterizations of surface water flow on bare ice in the literature, as well as smaller than most estimates of snowpack permeability. For supraglacial environments in which porosity/permeability creation in the subsurface is balanced by porous flow of meltwater, our methods provide an estimate of microscale hydraulic properties from observations of supraglacial channel spacing.

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Section: Site Summary and Methodsmentioning

confidence: 50%

Near-surface permeability in a supraglacial drainage basin on the Llewellyn Glacier, Juneau Icefield, British Columbia

2014

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“…6 in Berthier et al, 2016), we sampled an hypothetic seasonal cycle in surface elevation changes at the time of acquisition of all ASTER DEMs over the JIF and fitted a linear regression to the elevation change time series. Assuming a seasonal amplitude as large as 10 m (a value in agreement with field measurements of the Juneau Icefield Mass Balance Program; Pelto et al, 2013), the slope of the regression line is very close to 0 (−0.007 m a −1 ), suggesting no seasonal bias in the dates of the ASTER DEMs.…”

Section: Discussionmentioning

confidence: 65%

“…a −1 between 1953 and 1985 to −0.60 m w.e. a −1 between 1986 and 2011 (Pelto et al, 2013). The trend toward enhanced mass loss is also observed on Taku Glacier, for which the mass balance was posi- (Pelto et al, 2008).…”

Section: Introductionmentioning

confidence: 58%

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Brief communication: Unabated wastage of the Juneau and Stikine icefields (southeast Alaska) in the early 21st century

et al. 2018

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Abstract. The large Juneau and Stikine icefields (Alaska) lost mass rapidly in the second part of the 20th century. Laser altimetry, gravimetry and field measurements suggest continuing mass loss in the early 21st century. However, two recent studies based on time series of Shuttle Radar Topographic Mission (SRTM) and Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) digital elevation models (DEMs) indicate a slowdown in mass loss after 2000. Here, the ASTER-based geodetic mass balances are recalculated carefully avoiding the use of the SRTM DEM because of the unknown penetration depth of the C-band radar signal. We find strongly negative mass balances from 2000 to 2016 (−0.68 ± 0.15 m w.e. a −1 for the Juneau Icefield and −0.83 ± 0.12 m w.e. a −1 for the Stikine Icefield), in agreement with laser altimetry, confirming that mass losses are continuing at unabated rates for both icefields. The SRTM DEM should be avoided or used very cautiously to estimate glacier volume change, especially in the North Hemisphere and over timescales of less than ∼ 20 years.

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“…of precipitation per year (Pelto et al, 2013) and a significantly drier eastern portion. The icefield is in the direct path of southwesterly storms that cross the Gulf of Alaska, transporting warm, moist air to southeast Alaska from the Pacific (Fleming et al, 2000;Simpson et al, 2002).…”

Section: Study Sitementioning

confidence: 99%

Modeling Winter Precipitation Over the Juneau Icefield, Alaska, Using a Linear Model of Orographic Precipitation

et al. 2018

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Assessing and modeling precipitation in mountainous areas remains a major challenge in glacier mass balance modeling. Observations are typically scarce and reanalysis data and similar climate products are too coarse to accurately capture orographic effects. Here we use the linear theory of orographic precipitation model (LT model) to downscale winter precipitation from the Weather Research and Forecasting Model (WRF) over the Juneau Icefield, one of the largest ice masses in North America (>4,000 km 2 ), for the period 1979-2013. The LT model is physically-based yet computationally efficient, combining airflow dynamics and simple cloud microphysics. The resulting 1 km resolution precipitation fields show substantially reduced precipitation on the northeastern portion of the icefield compared to the southwestern side, a pattern that is not well captured in the coarse resolution (20 km) WRF data. Net snow accumulation derived from the LT model precipitation agrees well with point observations across the icefield. To investigate the robustness of the LT model results, we perform a series of sensitivity experiments varying hydrometeor fall speeds, the horizontal resolution of the underlying grid, and the source of the meteorological forcing data. The resulting normalized spatial precipitation pattern is similar for all sensitivity experiments, but local precipitation amounts vary strongly, with greatest sensitivity to variations in snow fall speed. Results indicate that the LT model has great potential to provide improved spatial patterns of winter precipitation for glacier mass balance modeling purposes in complex terrain, but ground observations are necessary to constrain model parameters to match total amounts.

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Juneau Icefield Mass Balance Program 1946–2011

Cited by 34 publications

References 19 publications

Near-surface permeability in a supraglacial drainage basin on the Llewellyn Glacier, Juneau Icefield, British Columbia

Near-surface permeability in a supraglacial drainage basin on the Llewellyn Glacier, Juneau Icefield, British Columbia

Brief communication: Unabated wastage of the Juneau and Stikine icefields (southeast Alaska) in the early 21st century

Modeling Winter Precipitation Over the Juneau Icefield, Alaska, Using a Linear Model of Orographic Precipitation

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