The ortophotomap of Hornsund Fiord with changes to the front positions of tidewater glaciers. The front positions are based on different cartographical maps and satellite data. The base map is Sentinel 2 satellite image acquired on 6 July 2018. Citation: Kolondra L., 2018. Hornsund Fiord - Changes to the front positions of tidewater glaciers. University of Silesia, Faculty of Earth Sciences.

Englacial water pressure was recorded by placing HOBO 250-Foot Depth Water Level Data Loggers in the center of Crystal Cave (N77°02' E15°34', 174 m) channel system (Hansbreen glacier). Data loggers were set to record values every 30 minutes, resampled to daily in post-processing, and have a resolution of 2.55 kPa for a typical error of 3.8 cm water level. Water pressure was converted in water level. Sensor was placed in the cave by drilling anchor points into the ice above a vertical shaft, then hanging cables down in the center of conduit. Stabilization cables were used to keep sensors from attaching to and freezing into ice walls by manually rappelling down to the sensor and attaching it to three horizontal cables, anchored into the ice walls at about 120 degrees apart. Senor was installed in Crystal Cave at about 100 m total distance from the cave entrance, in ice about 74 m thick. The sensor was installed 28 m above the glacier bed and 46 m below the ice surface.

Results of supervised classification of six Landsat 8 images acquired on: 25 May, 3 June, 22 June, 15 July, 4 August and 20 August 2014, covering glaciers in Hornsund fiord. Method of classification: Maximum Likelihood. The results show variability of snow cover areas in melting period of 2014 for glaciers located in Hornsund fiord and larger than 9 km2 (Körberbreen, Samarinbreen, Chomjakovbreen, Mendelejevbreen, Svalisbreen, Hornbreen, Storbreen, Kvalfangarbreen, Mühlbacherbreen, Paierlbreen and Hansbreen). For more information, please check: https://doi.org/10.3390/w9100804 Overview: Results of Maximum Likelihood classification of Landsat 8 images for analysed glaciers. Red - snow cover, yellow - glacier ice, black - debirs, grey - cloud cover.

Glacier velocities are derived from the displacements of four stakes (Z, R, T, U) installed close to the front of three glaciers in Hornsund. Measurements of stakes position were conducted in 2013-2015, with precise dGPS receiver (Leica 1230, accuracy ±5cm) and single-frequency GPS receiver (Garmin, accuracy ±5m). Detailed description of the source data and accuracy can be found in: Błaszczyk M., Ignatiuk D., Uszczyk A., Cielecka-Nowak K., Grabiec M., Jania J., Moskalik M., Walczowski W., 2019. Freshwater input to the Arctic fjord Hornsund (Svalbard). Polar Research, 38. https://doi.org/10.33265/polar.v38.3506

Glaciers facies extents of Vestfonna delivered from unsupervised classifications of SAR data (fully-polarimetric ALOS PALSAR, single polarimetric ERS-2 SAR) for 2009 year. Date of SAR images acquisitions: 4, 7, 20, 23, 26 May 2009 (VV Single Look Complex ERS-2 SAR), 22 May 2009 (ALOS PALSAR Single Look Complex 1.1, quad polarimetry). Method of classification: K-means classification, H-a Wishart Classification. Results validated with Ground Penetrating Radar data. For more information, please check: https://doi.org/10.1016/j.rse.2018.11.020 Overwiew of results of different classification methods with comparison to GPR data. Top panel: Pauli decomposition, middle panel: H-a Wishart classification, bottom panel: k-means classification. For more information, please check: https://doi.org/10.1016/j.rse.2018.11.020 (Figure 7).

• Discharge measurements were conducted from May/June/July to September/October in the years 2007–2012. Direct observation periods were 62, 51, 61, 40, 121, and 35 days in the consecutive years. The data set was obtained from CTD-DIVER DI 261 or Mini-Diver (Van Essen Instruments, Delft, The Netherlands) logger with barometric compensation by BaroDiver (Schlumberger, Houston, TX, USA) with 10-min intervals and flow velocities were measured with a SEBA F1 current meter (SEBA Hydrometrie GmbH, Kaufbeuren, Germany). Mean daily discharge and total runoff in the hydrologically active season was calculated on the basis of the 24h running average of the water level and a rating curve (Appendix 1). More details have been reported by Majchrowska E., Ignatiuk D., Jania J., Marszałek H., Wąsik M., 2015: Seasonal and interannual variability in runoff from the Werenskioldbreen catchment, Spitsbergen. Polish Polar Research vol. 36, no. 3, pp. 197–224. doi: 10.1515/popore−2015−0014 • Hydrological data for Werenskioldbreen - archive of the University of Silesia. The base contain mean daily discharge in the years: 1972, 1973, 1974, 1979, 1980, 1983, 1985, 1986, 1988, 1998, 2007, 2008, 2009, 2010, 2011, 2012, 2013, 2017 (18 hydrologically active seasons) – Appendix 2

Ice front position of the tidewater glaciers in Hornsund was examined during the following periods: 1899–1936–1960/1961–1976–1990–2001–2005–2010. For the period 1899–1990, several archival maps of varying accuracy were used, sometimes difficult to assess. For the period 1976–2010 multispectral and radar satellite images were used. Detailed description of the source data and accuracy can be found in: Błaszczyk M., Jania J.A., Kolondra L., 2013: Fluctuations of tidewater glaciers in Hornsund Fiord (Southern Svalbard) since the beginning of the 20th century. Polish Polar Research, 34(4): 327-352.

Firn extents of Hansbreen and Werenskoildbreen delivered from unsupervised classifications of single, dual and fully-polarimetric SAR data (ALOS-2 PALSAR, RADARSAT-2, Sentinel-1, ERS-2 SAR) between 2011 and 2017. Methods of classification: unsupervised ISO classification, H-a Wishart Classification. Results validated with terrestrial measurements (shallow ice cores drilling, Ground Penetrating Radar measurements). Research supported by the European Space Agency, Third Party Missions grant and Svalbard Science Forum, Arctic Field Grant 2018. For more details, please e-mail to this adress: bbarzycka@us.edu.pl.

Air temperature measurements from AWS located on the Werenskioldbreen. The sensors are installed on a mast that is mounted in the glacier ice. During the season, the distance between the glacier's surface and the sensors increases. The instruments are serviced at least once a year between March and April.

The dataset includes point winter and summer mass balance measurements on ablation stakes in 2009-2020 and the calculated point annual mass balance. The dataset includes part of the results from the project “Hindcasting and projections of hydro-climatic conditions of Southern 350 Spitsbergen” (grant no. 2017/27/B/ST10/01269) financed by the Polish National Science Centre, “Arctic climate system study of ocean, sea ice, and glaciers interactions in Svalbard area”—AWAKE2 (Pol-Nor/198675/ 17/2013), supported by the National Centre for Research and Development within the Polish–Norwegian Research Cooperation Programme and the SvalGlac—Sensitivity of Svalbard glaciers to climate change, the ESF Project, the project Integrated Arctic 355 Observing System (INTAROS)- Horizon 2020, the ice2sea 7th FP projects. The studies were carried out as part of the scientific activity of the Centre for Polar Studies (University of Silesia in Katowice) with the use of research and logistic equipment of the Polar Laboratory of the University of Silesia in Katowice.