/Copernicus Sentinel / Using the Sentinels to map the state and changes of Norwegian glaciers Liss Marie Andreassen, Solveig H. Winsvold, Andreas Kääb, Alexandra Messerli, Geir Moholdt, Suruchi Engelhardt, Ferdinand Klingenberg, Nils Kristian Orthe.
Glaciers are changing Photo: Olav Liestøl 1949 1908 Photo: Liss M. Andreassen 2016
Why are glaciers important? Sensitive climate indicators Sea level rise Water and energy resource Tourism Hazards: outburst floods & ice falls
Why are glaciers important? Sensitive climate indicators Sea level rise Water and energy resource Tourism Hazards: outburst floods & ice falls Photo: Jostein Aasen
Photo: Hans Martin Hjemaas
Photo: Ole Magnus Tønsberg
Develope a national service for glaciers in mainland Norway & Svalbard Glacier lakes Outline Area Glacier products 1. Glacier outline, area & calving front 2. Glacier surface type & snow line 3. Ice velocity 4. Glacier crevasses & surge 5. Glacier lakes Crevasses Velocity /Copernicus Sentinel data 2016/ Ice Firn Snow Snowline Equilibrium line Skyer Sentinel 2 (B11-8-4) 2016-09-18
Glacier outline, area & calving front /Copernicus Sentinel data 2018/ Updated glacier mask of Svalbard and mainland Norway Present state & change detection Imagery without seasonal snow or clouds Combine several scenes to get optimal mapping conditions
Sentinel-2 20. July 2017 /Copernicus Sentinel data 2017/
Sentinel-2 20. July 2018 /Copernicus Sentinel data 2018/
Sentinel vs Landsat /Copernicus Sentinel data 2018/ /Landsat 2014/ S2: 2018-07-03 L8: 2014-09-15
/Copernicus Sentinel data 2018/ Spectral bands used for glacier mapping S2: B4 Red S2: B8 NIR S2: B11 SWIR
/Copernicus Sentinel data 2018/ Band ratio and thresholding Band4/Band11 Threshold >
Calving fronts Svalbard /Copernicus Sentinel data 24 July 2017/ Austfonna Storisstraumen Bråsvellbreen Calving fronts from Landsat-8 and Sentinel-2 Storisstraumen Nathorstbreen Advance and retreat between 2000s and 2015 (Landsat-8). Generell retreat except two major advances (surge) - Nathorstbreen (2009->) - Storisstraumen, Austfonna (2012->)
Ice velocity: Sentinel-1 Glacier surface speeds can be detected using radar offset tracking Svalbard: Repeat Sentinel-1 radar images of January 2018. The color-code from blue to red is saturated at 5 m/day. MODIS
Ice velocity: Sentinel-2 Glacier surface speeds derived using optical image matching. Standardised normalised crosscorrelation. Using band 8 (NIR) Sentinel-2 image-matching programme CIAS. Jostedalsbreen, Norway: image matching of Sentinel-2 for 22 August - 16 September 2017.
Ice velocity: Sentinel 2 Work on larger glaciers Need to see crevasses Checked potential for Norway
Glacier surges Surge-> increase in flow velocity Shifts in flow regimes can be detected using Sentinel Negribreen, Svalbard: A 10-m resolution velocity map of surge in spring 2017 from a Sentinel-2 pair.
Crevasses Crevasses can be detected automatically on S-2/L-8 using Radon transform Can also be mapped manually Austfonna Basin 3, Svalbard: Crevasse fields display particularly dominant directional greyscale variations. Figure: Bas Altena, UiO
Glacier lakes Jøkulhlaup: Glacier lake outburst floods (GLOFs) Sentinel-2 imagery used to survey previously registered GLOFs detect new possible GLOF sites Method to map lakes: Normalized Difference Water Index (NDWI) Manual digitization NDWI = Green NIR Green + NIR
/Copernicus Sentinel data 2018/ Jøkulhlaup from Blåmannsisen Glacier-dammed lake Blåmannsisen Sentinel-2 26 August 2018
14 August 2018 1 September 2018
Jøkulhlaup from Blåmannsisen Sentinel-1: GLOF had started early morning 25 August 05:37 Glacier-dammed lake Blåmannsisen
Jøkulhlaup from Blåmannsisen Lowering: 32.5 m Volume: ~22 mill. m 3 Glacier-dammed lake Blåmannsisen
/Copernicus Sentinel data 2018/ Example Marabreen 26 July 1 Sep
Kronebreen Setevatnet Kongsvegen Uversbreen Setevatnet ~5km Area ~1 km 2
Setevatnet Lake Drainage Tile 33XVH Different relative orbits. 23/07/2017-26/07/2017 First image shows the lake at its maximum extent. Drainage was initiated about 12 hours after S-2 acquisition 23/07/2017.
Orthorectification & use of DTM Sentinel-2 needs to be processed with good elevation model SK DEM good for glacier mapping S2A available with Norwegian DEM for 2018, but not S2B. (fewer imagery available) Need S-2 with Norwegian DEM back to 2015. Sentinel-2 with National SK DEM displacements 2017-09-04 2017-09-07
Conclusions Sentinels suitable glacier mapping & surveying hazards mainland Norway & Svalbard For deriving glacier products: accurate DEM for orthorectification For utilizing full potential: need Sentinel 2B (ASAP)