Uncertainties and Reanalysing of Glacier Mass Balance Measurement

Uncertainties and re‐analysis of glacier mass balance measurement: Examples of glaciers in the Austrian Alps Goldbergkees and Kleinfleißkees 1998‐2009 Wurtenkees 1998‐2006 Bernhard Hynek Zentralanstalt für Meteorologie und Geodynamik, Wien SITE AND MONITORING MASS BALANCE TIME SERIES DEMS: 1931 1953 1969 1979 1991/92 1998 2006/09 WURTENKEES 1909 GOLDBERGKEES KLEINFLEISKEES DEM 1998 –10MRESOLUTION–AIRBORNE PHOTOGRAMMETRY DEM 2006/2009 –1M RESOLUTION –AIRBORNE LASER SCAN DEM 2006/2009 –1M RESOLUTION –AIRBORNE LASER SCAN One month time lag between Scans Homogenisation of DEM to one date GEODETIC MASS BALANCE‐ ADJUSTMENT TO ONE DATE ELEVATION CHANGE 27.7. ‐19.8.2009 ~‐1.35m ~‐1151.15m ELEVATION CHANGES BIAS STD RMSE ERRORS ON STABLE TERRAIN: 0280.28 2222.22 2242.24 DIRECT MASS BALANCES REANALYSIS OF MASS BALANCE CALCULATION FROM POINT VALUES TO GRID Input: • Point values of mass balance using all additional sources (Fotos, Automatic Kameras etc.) • Homogenized glacier areas • Same extrapolation‐schemes, gridding algorithms or model settings COMPARISON OF MASS BALANCES AND QUANTIFICATION OF RELATED UNCERTAINTIES Geodetic Mass Balance: Glaciological Mass Balance: TOTAL FLK GOK up GOK lp WUK lp WUK up TOTAL FLK GOK up GOK lp WUK lp WUK up Period 98‐09 98‐09 98‐09 98‐06 98‐06 Period 98‐09 98‐09 98‐09 98‐06 98‐06 Years 11 11 11 8 8 Years 11 11 11 8 8 mb.geod [m] ‐8.28 ‐5.46 ‐12.43 ‐13.01 ‐6.20 mb.direct [m] ‐7.7 ‐6.0 ‐10.8 ‐12.3 ‐5.1 Ϭ.sys.point [m] Ϭ.sys.snow.09/06 [m] ‐1.16 ‐0.92 0.00 ‐0.30 ‐0.52 Ϭ.sys.interpol [m] Ϭ.sys.stat.mod [m] 0.28 0.28 0.28 0.28 0.28 Ϭ.sys. ref. area [m] Ϭ.sys.DEM.res [m] 0.01 0.01 0.04 0.01 0.01 Ϭ.sys.date.corr [m] 0.35 0.30 0.52 1.19 0.85 Ϭ.sys.total [m] ‐0.86 ‐0.62 0.32 0.00 ‐0.22 Ϭ.sys.total [m] 0.35 0.30 0.52 1.19 0.85 Ϭ.stoc.density [m] 0.41 0.27 0.31 0.33 0.31 Ϭ.stoc.point [m] 0.43 0.33 0.33 0.28 0.28 Ϭ.stoc.stat.mod [m] 0.16 0.35 0.15 0.24 0.22 Ϭ.stoc.interpol [m] 0.50 0.66 0.50 0.57 0.85 Ϭ.stoc.ref.area [m] 0.20 0.46 0.20 0.23 0.47 Ϭ.stoc.ref.area [m] 0.33 0.23 0.23 0.54 0.23 Ϭ.stoc.snowcorr [m] 0.20 0.20 0 0.30 0.30 Ϭ.stoc.date.corr [m] 0.35 0.35 0.35 0.40 0.40 Ϭ.stoc.total [m] 0.53 0.67 0.40 0.55 0.67 Ϭ.stoc.total [m] 0.82 0.85 0.73 0.92 1.01 FLK GOK up GOK lp WUK lp WUK up 0.00 ‐2.00 ‐4.00 ‐6.00 Geodetic ‐8.00 Direct ‐10.00 ‐12.00 ‐14.00 Geodetic and direct mass balance ‐16.00 do not match within their error bars! Why? TO IDENTIFY REASONS FOR MISMATCH: DIFFERENTIATE MASS BALANCE GRIDS Elevation Changes Surface Mass Balance Elevation Changes –Surface Mass Balance • Ice Dynamics ( Submergence in Accumulation Area) • Basal melt or • Underestimation of Surface MB • Ice Dynamics (Emergence in the Ablation Area) • Overestimation of Surface MB • Errors in the DEMs Questions? Struc ture from motion ‐ photogrammetry for everybody Bernhard Hynek Zentralanstalt für Meteorologie und Geodynamik, Wien Structure from motion ‐ photogrammetry • Application of SfM photogrammetry and computer vision software – Cheap method to create 3d models, DEM´s and orthofotos – Volume change calculations, geodetic mass balance, glacier area or snowline mapping • Advantages – Photogrammetry for everybody: cheap and very easy to learn – You only need a digital camera with fixed zoom lense and a dGPS – Survey can be carried out during mass balance fieldwork (no date homogenization!) – Very high resolution and accuracy possible (rel. accuracy below 1/1000) – Highly automatized processing with computervision software (e.g. photoscan) – You can use UAF‘s or helium‐filled kites to minimize the survey time • Disadvantages – You need good visibility and surface texture – Surface texture may change during survey (snowfall!) – Terrestrial survey is restricted to smaller valley glaciers – Very RAM‐demanding processing software (Minimum: 16GB RAM) General Workflow to create a DEM out of photographs In the field: • Take images of the area of interest • Measure coordinates of some points In the office: • Align images • Control and edit point cloud • Calculate a 3d model in low resolution • Set the coordinates of markers on the picture • Calculate a 3d model in high resolution • Optimize the calculation by editing the sparse point cloud • GtGenerate TtTexture • Export 3d model, point cloud, DEM, Orthofoto etc. Example Freya Glacier Zackenberg Research Station Wollaston Foreland A.P. Olsen Icecap Freya Glacier GIS Payer Land Clavering Island Young Sound Skille Glacier Map, location and foto Freya glacier(Vintergata Gl.) Daneborg Station Fig. 1: Map of Mass Balance and Fig. 2: Satellite Image of the Greenlandic East Fig. 3: Satellite Image of the Zackenberg Area with north Energy Balance Measurements in Cost in the ZackenbergFreya Area Glacier with Clavering IslandSkillepart Glacier of Clavering Island. Freya Glacier is about 15 km far Greenland until 1995 (Weidick, (Source: Google Earth). from the Zackenberg Station. In summer, Tyroler Fjord can 1995) be crossed by Zodiac. (Source: Google Earth). Eiger Ridge (800m) Tyroler Fjord Fig. 5: Aerial Image of Freya Glacier (Source: Fig. 6: Aerial Image from 1932 (Ahlmann, 1941a). The GEUS, 1980ies). Freya Glacier is a 6 km long largest valley glacier on Clavering Island is Skille Glacier 18 19 20 Surface Mass Balance Timeseries – update 2013 2008 2009 2010 2011 2012 2013 0 ‐250 ‐500 ‐750 ‐1000 ‐1250 ‐1500 2013/2013 14.8.12 – 18.8.13 ‐510 mm ‐466 mm ‐806 mm ‐934 mm ‐182 mm ‐1364 mm Automatic Camera: April 2013 ‐ August 2013 Photogrammetric survey August 2013 The image cannot be displayed. Your computer may not have enough memory to open the image, or the image may have been corrupted. Restart your computer, and then open the file again. If the red x still appears, you may have to delete the image and then insert it again. 364 18.8. 154 12.8. 288 11.8 . 310 Upper part of the glacier Lower part of the glacier goto Freya Glacier in photoscan Survey in August 2013 photopoints dGPS points Imagery goto Goldbergkees in photoscan Orthofoto DEM‐Validation: Elevation Changes 2009/8 – 2012/8 Questions? Survey in August 2012.

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