@misc{HitzigerNaekePavelka, author = {Hitziger, Thomas and N{\"a}ke, Luisa and Pavelka, Karel}, title = {Ice Elevation Change Based on GNSS Measurements along the Korth-Traverse in Southern Greenland}, series = {Applied Sciences}, volume = {12}, journal = {Applied Sciences}, number = {23}, issn = {1454-5101}, doi = {10.3390/app122312066}, abstract = {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 Isbr{\ae}). 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.}, language = {en} } @misc{StoberHitzigerHeimetal., author = {Stober, Manfred and Hitziger, Thomas and Heim, Johanna and N{\"a}ke, Luisa and Hepperle, J{\"o}rg}, title = {Thirty years (1991 to 2021) ice elevation changes at Swiss Camp (West Greenland)}, series = {Polar Regions, Climate Change and Society, 28th International Polar Conference, Potsdam, 01 - 05 May 2022, German Society for Polar Research}, journal = {Polar Regions, Climate Change and Society, 28th International Polar Conference, Potsdam, 01 - 05 May 2022, German Society for Polar Research}, publisher = {Alfred-Wegener-Institut f{\"u}r Polar- und Meeresforschung}, address = {Bremerhaven}, issn = {1866-3192}, doi = {10.57738/BzPM_0762_2022}, pages = {S. 145}, abstract = {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.}, language = {en} } @misc{NaekeHitzigerHeim, author = {N{\"a}ke, Luisa and Hitziger, Thomas and Heim, Johanna}, title = {Ice elevation change based on GNSS measurements along the Greenland Korth Expedition}, series = {Polar- und Meeresforschung, Polar Regions, Climate Change and Society 28th International Polar Conference Potsdam, 01 - 05 May 2022 German Society for Polar Research}, journal = {Polar- und Meeresforschung, Polar Regions, Climate Change and Society 28th International Polar Conference Potsdam, 01 - 05 May 2022 German Society for Polar Research}, publisher = {Alfred-Wegener-Institut f{\"u}r Polar- und Meeresforschung}, address = {Bremerhaven}, issn = {1866-3192}, doi = {https://doi.org/10.57738/BzPM_0762_2022}, pages = {S. 107}, abstract = {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 Isbr{\ae} 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 Isbr{\ae} 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.}, language = {en} } @misc{HitzigerNaeke, author = {Hitziger, Thomas and N{\"a}ke, Luisa}, title = {Vergleich kinematischer GNSS-Daten des gr{\"o}nl{\"a}ndischen Eisschildes}, series = {21. Internationale Geod{\"a}tische Woche Obergurgl 2021}, journal = {21. Internationale Geod{\"a}tische Woche Obergurgl 2021}, editor = {Weinold, Thomas}, publisher = {Wichmann Verlag}, isbn = {978-3-87907-702-1}, pages = {201 -- 206}, abstract = {Gegenstand dieser Arbeit ist der Vergleich kinematischer GNSS-Daten. Dieser erfolgt teilautomatisiert mittels MATLAB Programmen. Um 2 Messreihen vergleichen zu k{\"o}nnen, wurde die Plattenkinematik ber{\"u}cksichtigt. Außerdem wurde durch Gl{\"a}ttung der Eingangsdaten mittels Gaußfilterung das Rauschen herausgefiltert. Es bieten sich aufgrund der speziellen Topographie des Messgebietes zwei M{\"o}glichkeiten des Vergleichs an. Betrachtet werden Punkte, die sich innerhalb eines vorgegebenen Abstandes befinden. Eine andere M{\"o}glichkeit besteht darin, Kreuzungspunkte zwischen den zu vergleichenden Profilen zu ermitteln. Beide Varianten wurden programmiert und sind gut anwendbar.}, language = {de} } @misc{HitzigerNaeke, author = {Hitziger, Thomas and N{\"a}ke, Luisa}, title = {GNSS-Messungen entlang der Gr{\"o}nland-Korth-Expeditionen - ein Langzeitprojekt in S{\"u}dgr{\"o}nland}, series = {22. Internationale Geod{\"a}tische Woche Obergurgl 2023}, journal = {22. Internationale Geod{\"a}tische Woche Obergurgl 2023}, editor = {Weinold, Thomas}, publisher = {Wichmann Verlag}, address = {Berlin}, isbn = {978-3-87907-738-0}, pages = {281 -- 287}, abstract = {Im Fr{\"u}hjahr 2021 durchquerte eine Expedition der HEIM-Gruppe das gr{\"o}nl{\"a}ndische Inlandeis von Ost nach West. Sie f{\"u}hrten GNSS-Messungen entlang ihrer gesamten Route durch, um die fr{\"u}heren Messungenvon Korth seit 2002 und sp{\"a}ter von Hitziger 2020 fortzusetzen. Entlang der Traverse der Gr{\"o}nland-Korth-Expeditionen (GKE) ist der EInfluss der beiden Auslassgletscher Helheim im Osten und Jakobshavn Isbr{\ae} im Westen auf die H{\"o}hen{\"a}nderung 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.}, language = {de} } @misc{StoberHitzigerNaekeetal., author = {Stober, Manfred and Hitziger, Thomas and N{\"a}ke, Luisa and Heim, Johanna and Hepperle, J{\"o}rg}, title = {Dreißig Jahre Eish{\"o}hen{\"a}nderungen am Swiss Camp (Gr{\"o}nland)}, series = {Polarforschung}, volume = {91}, journal = {Polarforschung}, issn = {2190-1090}, doi = {10.5194/polf-91-95-2023}, pages = {95 -- 104}, abstract = {Seit 1991 betreibt der Erstautor ein Projekt zur Untersuchung der Eish{\"o}hen{\"a}nderung, Fließgeschwindigkeit und Deformation mittels GNSS Bodenmessungen am Swiss Camp in der N{\"a}he der Gleichgewichtslinie im westlichen Randbereich des Gr{\"o}nl{\"a}ndischen 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 Gr{\"o}nl{\"a}ndische Inlandeis von Ost nach West {\"u}berquert und dabei auch die Oberfl{\"a}chenh{\"o}hen bestimmt. In den Jahren 2015 und 2021 konnte auch das Gebiet Swiss Camp mit GNSS vermessen werden. Mit deren Ergebnissen konnten nun die H{\"o}hen{\"a}nderungen auf nunmehr 30 Jahre ausgedehnt werden und stellen somit ein einmaliges Langzeitprojekt dar Vor 2014 ergab sich eine stark beschleunigte H{\"o}henabnahme. Auch die H{\"o}hen{\"a}nderungen seit 2014 bis 2021 zeigen weiterhin eine deutliche H{\"o}henabnahme, jedoch weniger schnell als in den Jahren zuvor. Diese zeitlichen Variationen der H{\"o}henabnahmeraten 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 h{\"o}her als zuvor, so dass beide Effekte f{\"u}r geringere Schmelzenergie gesorgt haben. Diese lokalen H{\"o}hen{\"a}nderungen stimmen {\"u}berein mit großr{\"a}umigen Befunden in ganz Gr{\"o}nland, die mit Schwerefelddaten der satellitengest{\"u}tzten Mission GRACE abgeleitet wurden. Insgesamt hat in den 30 Jahren die Eisoberfl{\"a}che am Swiss Camp um etwa 20 m abgenommen, das sind ca. 1.7 \% der dortigen Eism{\"a}chtigkeit.}, language = {de} } @misc{NaekeMiesnerIngemanNielsenetal., author = {N{\"a}ke, Luisa and Miesner, Frederieke and Ingeman-Nielsen, Thomas and Boike, Julia and Ghoreishian Amiri, Seyed Ali}, title = {Numerical modeling to estimate the impact of built infrastructure on permafrost degradation - Case study from Ilulissat, Greenland}, series = {Book of abstracts, EUCOP6}, journal = {Book of abstracts, EUCOP6}, editor = {Fern{\´a}ndez-Fern{\´a}ndez, Jos{\´e} M.}, doi = {10.52381/EUCOP6.abstracts.1}, pages = {166}, abstract = {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.}, language = {en} }