A regional view of fluctuations in glacier length in southern South America

López, P.; Chevallier, Pierre; Favier, Vincent; Pouyaud, Bernard; Ordenes, Fernando; Oerlemans, J.

doi:10.1016/j.gloplacha.2009.12.009

Cited by 102 publications

(103 citation statements)

References 49 publications

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“…In 1986 the area of the glacier was 73.68 km 2 . Generally, most glaciers within this area are retreating [41], and the Oriental is no exception [42], though minor in a regional perspective [40]. Together with the ancillary retreat, an elevation loss is observed over large parts of the icefield since 2000 [43].…”

Section: Oriental Patagoniamentioning

confidence: 96%

Elevation Change and Improved Velocity Retrieval Using Orthorectified Optical Satellite Data from Different Orbits

Altena

Kääb

2017

Remote Sensing

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Abstract:Optical satellite products are available at different processing levels. Of these products, terrain corrected (i.e., orthorectified) products are the ones mostly used for glacier displacement estimation. For terrain correction, a digital elevation model (DEM) is used that typically stems from various data sources with variable qualities, from dispersed time instances, or with different spatial resolutions. Consequently, terrain representation used for orthorectifying satellite images is often in disagreement with reality at image acquisition. Normally, the lateral orthoprojection offsets resulting from vertical DEM errors are taken into account in the geolocation error budget of the corrected images, or may even be neglected. The largest offsets of this type are often found over glaciers, as these may show strong elevation changes over time and thus large elevation errors in the reference DEM with respect to image acquisition. The detection and correction of such orthorectification offsets is further complicated by ice flow which adds a second offset component to the displacement vectors between orthorectified data. Vice versa, measurement of glacier flow is complicated by the inherent superposition of ice movement vectors and orthorectification offset vectors. In this study, we try to estimate these orthorectification offsets in the presence of terrain movement and translate them to elevation biases in the reference surface. We demonstrate our method using three different sites which include very dynamic glaciers. For the Oriental Glacier, an outlet of the Southern Patagonian icefield, Landsat 7 and 8 data from different orbits enabled the identification of trends related to elevation change. For the Aletsch Glacier, Swiss Alps, we assess the terrain offsets of both Landsat 8 and Sentinel-2A: a superior DEM appears to be used for Landsat in comparison to Sentinel-2, however a systematic bias is observed in the snow covered areas. Lastly, we demonstrate our methodology in a pipeline structure; displacement estimates for the Helheim-glacier, in Greenland, are mapped and corrected for orthorectification offsets between data from different orbits, which enables a twice as dense a temporal resolution of velocity data, as compared to the standard method of measuring velocities from repeat-orbit data only. In addition, we introduce and implement a novel matching method which uses image triplets. By formulating the three image displacements as a convolution, a geometric constraint can be exploited. Such a constraint enhances the reliability of the displacement estimations. Furthermore the implementation is simple and computationally swift.

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Section: Oriental Patagoniamentioning

confidence: 96%

Elevation Change and Improved Velocity Retrieval Using Orthorectified Optical Satellite Data from Different Orbits

Altena

Kääb

2017

Remote Sensing

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“…Of 69 major outlet glaciers in the region, 49 flow into lakes and the rest flow into the ocean (Warren and Aniya, 1999). Most of the calving glaciers have been retreating over the last several decades (Aniya et al, 1997;Rignot et al, 2003;Masiokas et al, 2009;Lopez et al, 2010) as a result of warming climate (e.g., Lopez et al, 2010;Schaefer et al, 2015). For example, Glaciar Upsala, a freshwater calving glacier in the Southern Patagonia Icefield (SPI), has been retreating and thinning since 2008, at rates significantly greater than those of other glaciers in Patagonia (Muto and Furuya, 2013;Sakakibara et al, 2013;Sakakibara and Sugiyama, 2014), and mass loss from this glacier accounted for about 15% of the total mass loss from the SPI between 2000 and 2012 (Willis et al, 2012).…”

Section: Introductionmentioning

confidence: 99%

Seasonal Variations in Ice-Front Position Controlled by Frontal Ablation at Glaciar Perito Moreno, the Southern Patagonia Icefield

et al. 2017

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The front position of calving glaciers is controlled by ice speed and frontal ablation which consists of the two processes of calving and subaqueous melting. However, the relative importance of these processes in frontal variation is difficult to assess and poorly understood, particularly for freshwater calving glaciers. To better understand the mechanism of seasonal variations involved in the ice front variations of freshwater calving glaciers, we measured front position, ice surface speed, air temperature, and proglacial lakewater temperature of Glaciar Perito Moreno in Patagonia. No substantial fluctuations in front position and ice speed occurred during the 15-year period studied (1999)(2000)(2001)(2002)(2003)(2004)(2005)(2006)(2007)(2008)(2009)(2010)(2011)(2012)(2013), despite a warming trend in air temperature (0.059 • C a −1 ). Seasonal variations were observed both in the ice-front position (±50 m) and ice speed (±15%). The frontal ablation rate, computed from the frontal displacement rate and the ice speed, varied in a seasonal manner with an amplitude approximately five times greater than that in the ice speed. The frontal ablation correlated well with seasonal lakewater temperature variations (r = 0.96) rather than with air temperature (r = 0.86). Our findings indicate that the seasonal ice front variations of Glaciar Perito Moreno are primarily due to frontal ablation, which is controlled through subaqueous melting by the thermal conditions of the lake.

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“…This is an important calving glacier in the region covering an area of 945 km 2 (Aniya et al, 1996). The glacier was selected for this study due to the availability of several studies on the surface changes, carried out over the last 30 years (Skvarca et al, 1995, Aniya et al, 1996Lopez et al, 2010;Rivero et al, 2013). To support the field image acquisition, an integrated data acquisition system was built around the CANON EOS Mark II DSLR camera; pixel size: 7.2 μ, objective focal length: 50 mm, and FOV: 46°.…”

Section: Test and Data Acquisitionmentioning

confidence: 99%

Optical Flow Applied to Time-Lapse Image Series to Estimate Glacier Motion in the Southern Patagonia Ice Field

Lannutti

Lenzano

Toth

et al. 2016

Int. Arch. Photogramm. Remote Sens. Spatial Inf. Sci.

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ABSTRACT:In this work, we assessed the feasibility of using optical flow to obtain the motion estimation of a glacier. In general, former investigations used to detect glacier changes involve solutions that require repeated observations which are many times based on extensive field work. Taking into account glaciers are usually located in geographically complex and hard to access areas, deploying time-lapse imaging sensors, optical flow may provide an efficient solution at good spatial and temporal resolution to describe mass motion. Several studies in computer vision and image processing community have used this method to detect large displacements. Therefore, we carried out a test of the proposed Large Displacement Optical Flow method at the Viedma Glacier, located at South Patagonia Icefield, Argentina. We collected monoscopic terrestrial time-lapse imagery, acquired by a calibrated camera at every 24 hour from April 2014 until April 2015. A filter based on temporal correlation and RGB color discretization between the images was applied to minimize errors related to changes in lighting, shadows, clouds and snow. This selection allowed discarding images that do not follow a sequence of similarity. Our results show a flow field in the direction of the glacier movement with acceleration in the terminus. We analyzed the errors between image pairs, and the matching generally appears to be adequate, although some areas show random gross errors related to the presence of changes in lighting. The proposed technique allowed the determination of glacier motion during one year, providing accurate and reliable motion data for subsequent analysis.

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A regional view of fluctuations in glacier length in southern South America

Cited by 102 publications

References 49 publications

Elevation Change and Improved Velocity Retrieval Using Orthorectified Optical Satellite Data from Different Orbits

Elevation Change and Improved Velocity Retrieval Using Orthorectified Optical Satellite Data from Different Orbits

Seasonal Variations in Ice-Front Position Controlled by Frontal Ablation at Glaciar Perito Moreno, the Southern Patagonia Icefield

Optical Flow Applied to Time-Lapse Image Series to Estimate Glacier Motion in the Southern Patagonia Ice Field

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