TY - GEN A1 - Hitziger, Thomas A1 - Näke, Luisa A1 - Pavelka, Karel T1 - Ice Elevation Change Based on GNSS Measurements along the Korth-Traverse in Southern Greenland T2 - Applied Sciences N2 - In 1912, a Swiss expedition led by meteorologist Alfred de Quervain crossed the Greenland ice sheet on a route from Disko Bay to Tasiilaq. Based on that, in 2002, a series of geodetic expeditions carried out by W. Korth and later by T. Hitziger began along the same traverse as in 1912, with the last measurements taken in May 2021. The statically collected GPS/GNSS data provide very accurate elevation changes at 36 points along the almost 700 km long crossing over a period of 19 years. According to this, there is a maximum increase of 2.1 m in the central area and a decrease of up to 38.7 m towards the coasts (influence Ilulissat Isbræ). By using kinematic GNSS measurements, there is a very dense profile with a spacing of a few meters. The comparison of those measurements is performed using crossing points or minimum distances and gives equivalent results for both methods. It is shown that local ice topography is preserved, and thus gaps in data sets can be caught. Areas of accumulation and ablation on the ice sheet can be identified, showing the widespread influence of outlet glaciers up to 200 km. The data can be used for direct verification of altimetry data, such as IceSat. Both IceSat elevations and their changes can be compared. KW - Greenland ice sheet KW - monitoring KW - GNSS KW - expedition KW - Jakobshavn Isbræ KW - Helheim Glacier KW - IceSat KW - climate change KW - glacier profile Y1 - 2022 UR - https://www.mdpi.com/2076-3417/12/23/12066 U6 - https://doi.org/10.3390/app122312066 SN - 1454-5101 VL - 12 IS - 23 ER - TY - GEN A1 - Stober, Manfred A1 - Hitziger, Thomas A1 - Heim, Johanna A1 - Näke, Luisa A1 - Hepperle, Jörg T1 - Thirty years (1991 to 2021) ice elevation changes at Swiss Camp (West Greenland) T2 - Polar Regions, Climate Change and Society, 28th International Polar Conference, Potsdam, 01 – 05 May 2022, German Society for Polar Research N2 - Since 1991 a long-term project exists for investigation of ice elevation change, ice flow velocity and deformation.at Swiss Camp (West Greenland, inland ice, 80 km from Ilulissat). The site was measured by the author with precise geodetic GNSS measurements on ground since 1991 until 2014 by 12 campaigns, and studied in relation to climatic indicators. In spring 2012 an expedition of the HEIM group traversed the Greenlandic inland ice from East to West. They conducted GNSS measurements along their entire route in order to continue the former measurements of KORTH 2002 and later by HITZIGER. Motivated by the author the HEIM expedition could also re-measure completely the research area at Swiss Camp in end of May 2021. Here we report about the results in context of former campaigns. The 2021 GNSS measurements were performed by a Trimble R12 receiver mounted on a sledge which was transported over the snow surface to the old stake positions. Together with kinematical measurements of all path ways the current heights were used to determine the elevation changes by digital elevation models and 48 single point comparisons. Together with the old results from 1991 to 2014 by the author the current elevation changes now result in a unique long-term 30-year time series of elevation changes from precise geodetic ground measurements on the Greenlandic ice sheet. During the overall observation period from 1991 to 2021 the ice height decreased by 19.3 meter. The new results show that in the period from 2014 to 2015 until 2021 the ice height is still distinctly decreasing, but less than 2006 to 2014. The peak was reached in 2011-2014 with 1,4 m/year. Since 2014 to 2021 the decrease in height was 0.9 m/year on average. These results are discussed together with climatic indicators. Air temperature and pdd-values correlate well with these elevation changes and show lower melting rates in this period. This is agreeing with mass balance results from satellite observations (GRACE resp. GRACE-FO). So the locally derived height changes from geodetic ground measurements confirm the large-scale satellite results. KW - West Greenland KW - GNSS KW - measurements KW - HEIM expedition Y1 - 2022 U6 - https://doi.org/10.57738/BzPM_0762_2022 SN - 1866-3192 SP - S. 145 PB - Alfred-Wegener-Institut für Polar- und Meeresforschung CY - Bremerhaven ER - TY - GEN A1 - Näke, Luisa A1 - Hitziger, Thomas A1 - Heim, Johanna T1 - Ice elevation change based on GNSS measurements along the Greenland Korth Expedition T2 - Polar- und Meeresforschung, Polar Regions, Climate Change and Society 28th International Polar Conference Potsdam, 01 – 05 May 2022 German Society for Polar Research N2 - Since 2002, repetitive measurements have been taken on the southern Greenland ice sheet to study the change in ice elevation along a historical route defined by Alfred de Quervain. Until 2012, static GNSS measurements were carried out every 20 km under the responsibility of Wilfried Korth (Greenland Korth Expedition GKE). Since 2015, kinematic GNSS measurements have been recorded every second along the entire traverse from the East (near Tasiilaq) to the West (near Ilulissat). The kinematic repeat measurement took place in summer 2020, but it had to be ended prematurely and therefore the area of influence of Jakobshavn Isbræ could not be examined. Two comparison methods were used. On the one hand that of the crossing points and on the other hand that of the minimum distances. Both methods give similar results for the Greenland ice sheet. Another expedition took place in spring 2021, which kinematically measured the entire traverse. Based on this data, an estimate for the missing area from 2020 can be made and thus the comparability to the previous campaigns at the same season can be established. Likewise, the change in winter from the end of the thaw period to the beginning of it can be examined. Along the traverse, the influence of the two outlet glaciers Helheim in the East and Jakobshavn Isbræ in the West on the change in elevation is significant. In the accumulation area, a maximum gain of 2.1 m is recorded, whereas in the ablation area, a loss of up to 38.7 m occurs in the period from 2002 to 2021. KW - GNSS KW - Ice Sheet KW - Alfred de Quervain KW - measurement KW - Jakobshavn Isbræ KW - Wilfried Korth Y1 - 2022 U6 - https://doi.org/https://doi.org/10.57738/BzPM_0762_2022 SN - 1866-3192 SP - S. 107 PB - Alfred-Wegener-Institut für Polar- und Meeresforschung CY - Bremerhaven ER - TY - GEN A1 - Hitziger, Thomas A1 - Näke, Luisa ED - Weinold, Thomas T1 - Vergleich kinematischer GNSS-Daten des grönländischen Eisschildes T2 - 21. Internationale Geodätische Woche Obergurgl 2021 N2 - Gegenstand dieser Arbeit ist der Vergleich kinematischer GNSS-Daten. Dieser erfolgt teilautomatisiert mittels MATLAB Programmen. Um 2 Messreihen vergleichen zu können, wurde die Plattenkinematik berücksichtigt. Außerdem wurde durch Glättung der Eingangsdaten mittels Gaußfilterung das Rauschen herausgefiltert. Es bieten sich aufgrund der speziellen Topographie des Messgebietes zwei Möglichkeiten des Vergleichs an. Betrachtet werden Punkte, die sich innerhalb eines vorgegebenen Abstandes befinden. Eine andere Möglichkeit besteht darin, Kreuzungspunkte zwischen den zu vergleichenden Profilen zu ermitteln. Beide Varianten wurden programmiert und sind gut anwendbar. KW - MATLAB KW - GNSS KW - Plattenkinematik Y1 - 2021 SN - 978-3-87907-702-1 SP - 201 EP - 206 PB - Wichmann Verlag ER - TY - GEN A1 - Hitziger, Thomas A1 - Näke, Luisa ED - Weinold, Thomas T1 - GNSS-Messungen entlang der Grönland-Korth-Expeditionen - ein Langzeitprojekt in Südgrönland T2 - 22. Internationale Geodätische Woche Obergurgl 2023 N2 - Im Frühjahr 2021 durchquerte eine Expedition der HEIM-Gruppe das grönländische Inlandeis von Ost nach West. Sie führten GNSS-Messungen entlang ihrer gesamten Route durch, um die früheren Messungenvon Korth seit 2002 und später von Hitziger 2020 fortzusetzen. Entlang der Traverse der Grönland-Korth-Expeditionen (GKE) ist der EInfluss der beiden Auslassgletscher Helheim im Osten und Jakobshavn Isbræ im Westen auf die Höhenänderung signifikant. Im Akkumulationsgebiet wird ein maximaler Gewinn von 2,1m verzeichnet, wohingegen im Ablationsgebiet im Zeitraum 2002 bis 2021 ein Verlust von bis zu 38,7m auftritt. KW - GNSS KW - Korth KW - Südgrönland KW - GLONASS KW - GPS KW - TEQC KW - RINEX-Daten Y1 - 2023 SN - 978-3-87907-738-0 SP - 281 EP - 287 PB - Wichmann Verlag CY - Berlin ER - TY - GEN A1 - Stober, Manfred A1 - Hitziger, Thomas A1 - Näke, Luisa A1 - Heim, Johanna A1 - Hepperle, Jörg T1 - Dreißig Jahre Eishöhenänderungen am Swiss Camp (Grönland) T2 - Polarforschung N2 - Seit 1991 betreibt der Erstautor ein Projekt zur Untersuchung der Eishöhenänderung, Fließgeschwindigkeit und Deformation mittels GNSS Bodenmessungen am Swiss Camp in der Nähe der Gleichgewichtslinie im westlichen Randbereich des Grönländischen Inlandeises. Die bisherigen Daten stammen aus 12 Kampagnen im Zeitraum 1991 bis 2014, also im Durchschnitt alle zwei Jahre. Neuerdings haben im Rahmen des Projektes „Spurensuche“ verschiedene Gruppen mit Schlitten das Grönländische Inlandeis von Ost nach West überquert und dabei auch die Oberflächenhöhen bestimmt. In den Jahren 2015 und 2021 konnte auch das Gebiet Swiss Camp mit GNSS vermessen werden. Mit deren Ergebnissen konnten nun die Höhenänderungen auf nunmehr 30 Jahre ausgedehnt werden und stellen somit ein einmaliges Langzeitprojekt dar Vor 2014 ergab sich eine stark beschleunigte Höhenabnahme. Auch die Höhenänderungen seit 2014 bis 2021 zeigen weiterhin eine deutliche Höhenabnahme, jedoch weniger schnell als in den Jahren zuvor. Diese zeitlichen Variationen der Höhenabnahmeraten stehen im Zusammenhang mit der Lufttemperatur im Sommer, die bis etwa 2012 einem ansteigenden Trend folgte, um in den anschließenden Jahren auf etwas niedrigerem Niveau zu bleiben. Ebenso war die Albedo in den Sommermonaten nach 2012 etwas höher als zuvor, so dass beide Effekte für geringere Schmelzenergie gesorgt haben. Diese lokalen Höhenänderungen stimmen überein mit großräumigen Befunden in ganz Grönland, die mit Schwerefelddaten der satellitengestützten Mission GRACE abgeleitet wurden. Insgesamt hat in den 30 Jahren die Eisoberfläche am Swiss Camp um etwa 20 m abgenommen, das sind ca. 1.7 % der dortigen Eismächtigkeit. Y1 - 2023 UR - https://polf.copernicus.org/articles/91/95/2023/polf-91-95-2023.html U6 - https://doi.org/10.5194/polf-91-95-2023 SN - 2190-1090 VL - 91 SP - 95 EP - 104 ER - TY - GEN A1 - Näke, Luisa A1 - Miesner, Frederieke A1 - Ingeman-Nielsen, Thomas A1 - Boike, Julia A1 - Ghoreishian Amiri, Seyed Ali ED - Fernández-Fernández, José M. T1 - Numerical modeling to estimate the impact of built infrastructure on permafrost degradation – Case study from Ilulissat, Greenland T2 - Book of abstracts, EUCOP6 N2 - Infrastructure in permafrost landscapes affects the ground thermal regime and may enhance permafrost degradation. Stability and usability of the infrastructure depend likewise on the thermal conditions of the subsurface. Permafrost in the study area in Ilulissat (West Greenland) is typically warm and often ice-rich, so infrastructure is likely to accelerate thawing of the ground. Numerical models can be used to estimate the influence of infrastructure on permafrost development, subsidence, and ponding near roads. In this study, we investigated the influence of roads in Ilulissat using the one-dimensional, laterally coupled heat-transfer model CryoGrid. We used ERA5 reanalysis data (1980-2020) and projections according to the SSP5-8.5 scenario (2020-2100) as climate forcing and validated them with site data from the local weather station (1991-2021). Borehole data from Ilulissat and the north-eastern surroundings provide information on soil stratigraphy properties to first built the model for the natural, undisturbed tundra. In the second model set up, we added the elevated gravel embankment as linear infrastructure to the model with several tiles for the roadway and the shoulder. In a third model run, we quantified the effect of snow by changing the snow distribution near the road to imitate plowing. We utilized measured data from the weather station and iButtons for validation of the model runs. Our simulation show that the construction of a road had a direct influence on the thermal regime by warming the soil. A general deepening of the active layer is projected within the current century, which is supported by borehole observations. Likewise, the associated measures of maintenance such as accumulation of cleared snow affect the response of the soil, as an insulator of the embankment, preventing stored heat from escaping. As the current state permafrost is vulnerable to climate change, it is important to rely on models to provide realistic projections. Y1 - 2023 UR - https://eucop2023.com/wp-content/uploads/2023/06/EUCOP2023-ABSTRACTS.pdf U6 - https://doi.org/10.52381/EUCOP6.abstracts.1 SP - 166 ER -