Satellite-derived volume loss rates and glacier speeds for the Cordillera Darwin Icefield, Chile

Melkonian, A. K.; Willis, M. J.; Pritchard, M. E.; Rivera, Andrés; Bown, Francisca; Bernstein, Stefan

doi:10.5194/tc-7-823-2013

Cited by 49 publications

(76 citation statements)

References 56 publications

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“…The methods used are fully described by Melkonian et al (2013Melkonian et al ( , 2016 and Willis et al (2012a), and are briefly described here. The SRTM DEM was used as a base image because it is a C-band radar product and is therefore not affected by cloud and snow coverage that can yield spurious elevations in the optical ASTER and WorldView DEMs.…”

Section: Ice Elevation Change Ratesmentioning

confidence: 99%

Dynamic Changes at Yahtse Glacier, the Most Rapidly Advancing Tidewater Glacier in Alaska

et al. 2017

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Since 1990, Yahtse Glacier in southern Alaska has advanced at an average rate of ∼100 m year −1 despite a negative mass balance, widespread thinning in its accumulation area, and a low accumulation-area ratio. To better understand the interannual and seasonal changes at Yahtse and the processes driving these changes, we construct velocity and ice surface elevation time series spanning the years 1985-2016 and 2000-2014, respectively, using satellite optical and synthetic aperture radar (SAR) observations. We find contrasting seasonal dynamics above and below a steep (up to 35% slope) icefall located approximately 6 km from the terminus. Above the icefall, velocities peak in May and reach their minima in October synchronous with the development of a small embayment at the calving terminus. The up-glacier minimum speeds, embayment, and plume of turbid water that emerges from the embayment are consistent with an efficient, channelized subglacial drainage system that lowers basal water pressures and leads to focused submarine melt in the calving embayment. However, velocities near the terminus are fastest in the winter, following terminus retreat, possibly off of a terminal moraine that results in decreased backstress. Between 1996 and 2016 the terminus decelerated by ∼40% at an average rate of ∼0.4 m day −1 year −1 , transitioned from tensile to compressive longitudinal strain rates, and dynamically thickened at rates of 1-6 m year −1 , which we hypothesize is in response to the development and advance of a terminal moraine. The described interannual changes decay significantly upstream of the icefall, indicating that the icefall may inhibit the upstream transmission of stress perturbations. We suggest that diminished stress transmission across the icefall could allow moraine-enabled terminus advance despite mass loss in Yahtse's upper basin. Our work highlights the importance of glacier geometry in controlling tidewater glacier re-advance, particularly in a climate favoring increasing equilibrium line altitudes.

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Section: Ice Elevation Change Ratesmentioning

confidence: 99%

Dynamic Changes at Yahtse Glacier, the Most Rapidly Advancing Tidewater Glacier in Alaska

et al. 2017

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“…For example, centerlines are important for determining glacier length changes over time (Leclercq et al, 2012;Nuth et al, 2013), analyzing velocity fields (Heid and Kääb, 2012;Melkonian et al, 2013), estimating glacier volumes (Li et al, 2012;Linsbauer et al, 2012), and one-dimensional modeling of glaciers (Oerlemans, 1997a;Sugiyama et al, 2007). Also, glacier length, derived from centerlines, is an important parameter for glacier inventories (Paul et al, 2009).…”

Section: Introductionmentioning

confidence: 99%

A new method for deriving glacier centerlines applied to glaciers in Alaska and northwest Canada

et al. 2014

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Abstract. This study presents a new method to derive centerlines for the main branches and major tributaries of a set of glaciers, requiring glacier outlines and a digital elevation model (DEM) as input. The method relies on a "cost grid-least-cost route approach" that comprises three main steps. First, termini and heads are identified for every glacier. Second, centerlines are derived by calculating the least-cost route on a previously established cost grid. Third, the centerlines are split into branches and a branch order is allocated. Application to 21 720 glaciers in Alaska and northwest Canada (Yukon, British Columbia) yields 41 860 centerlines. The algorithm performs robustly, requiring no manual adjustments for 87.8 % of the glaciers. Manual adjustments are required primarily to correct the locations of glacier heads (7.0 % corrected) and termini (3.5 % corrected). With corrected heads and termini, only 1.4 % of the derived centerlines need edits. A comparison of the lengths from a hydrological approach to the lengths from our longest centerlines reveals considerable variation. Although the average length ratio is close to unity, only ∼ 50 % of the 21 720 glaciers have the two lengths within 10 % of each other. A second comparison shows that our centerline lengths between lowest and highest glacier elevations compare well to our longest centerline lengths. For > 70 % of the 4350 glaciers with two or more branches, the two lengths are within 5 % of each other. Our final product can be used for calculating glacier length, conducting length change analyses, topological analyses, or flowline modeling.

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“…The Land Processes Distributed Active Archive Center (LP DAAC) uses this stereo-imagery to produce an on-demand DEM for each ASTER acquisition requested (e.g., Fujisada et al, 2005). Full details of the methodology for the feature tracking and dh dt processing are given in Willis et al (2012a), Melkonian et al (2013), and Melkonian et al (2014), as well as in the Supplementary Material.…”

Section: Introductionmentioning

confidence: 99%

Stikine Icefield Mass Loss between 2000 and 2013/2014

Melkonian¹,

Willis

Pritchard

2016

Front. Earth Sci.

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We calculate thinning rates ( dh ) at the 5800 km 2 Stikine Icefield of southeast dt Alaska from stacked digital elevation models (DEMs) acquired between 2000 and 2013/2014, and glacier velocities between 1985 and 2014 from feature tracking on optical image pairs. We find a mass change rate of −3.3 ± 1.1 Gt yr −1 between 2000 and 2014, equivalent to an area-averaged elevation change rate of −0.57 ± 0.18 m w.e. yr −1 . In 2014, land-terminating glaciers are 50% of the Stikine Icefield's glaciated area and contribute −0.9 ± 0.4 Gt yr −1 of mass change (27% of the total), while marine-terminating glaciers are only 30% of the total glaciated area, but contribute 1.5−1 − ± 0.3 Gt yr (or 45% of total mass change, with the remaining mass loss from lacustrine-terminating glaciers). We estimate the frontal ablation flux between 2000 and 2014 at the four largest marine-terminating glaciers on the Stikine Icefield (covering 90-95% of the marine-terminating glaciated area) using our glacier velocities and maps of fjord bathymetry to estimate terminus cross sections and glacier thicknesses. The combined 2014 frontal ablation flux of these four glaciers is 1.18 ± 0.14 Gt yr −1 , which may account for the difference in average mass loss between marine-and land-terminating glaciers on the Stikine Icefield. The Stikine and adjacent Juneau Icefields have very different mass loss contributions from marine-terminating glaciers (45% vs. effectively 0%), but both have area-averaged elevation change rates that are less negative than Alaska-wide estimates, which is surprising for these southernmost icefields in Alaska.

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Satellite-derived volume loss rates and glacier speeds for the Cordillera Darwin Icefield, Chile

Cited by 49 publications

References 56 publications

Dynamic Changes at Yahtse Glacier, the Most Rapidly Advancing Tidewater Glacier in Alaska

Dynamic Changes at Yahtse Glacier, the Most Rapidly Advancing Tidewater Glacier in Alaska

A new method for deriving glacier centerlines applied to glaciers in Alaska and northwest Canada

Stikine Icefield Mass Loss between 2000 and 2013/2014

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