Andreas Alexander

• Alexander, Andreas (2021). The thermal impact of tourism on a Svalbard glacier cave. Czech Polar Reports. ISSN 1805-0689. 11(1), s. 14–160. doi: 10.5817/CPR2021-1-11
• Tuhtan, J.A.; Alexander, Andreas; Kruusma, Maarja & Fuentes-Pérez, J.F. (2020). Multiscale change detection in a supraglacial stream using surface drifters, River Flow 2020 Proceedings of the 10th International Conference on Fluvial Hydraulics (Delft, Netherlands, 7-10 July 2020). CRC Press. ISSN 978-0-367-62773-7. doi: https%3A/doi.org/10.1201/b22619 Fulltekst i vitenarkiv
• Alexander, Andreas; Kruusmaa, Maarja; Tuhtan, Jeffrey; Hodson, Andrew; Schuler, Thomas & Kääb, Andreas (2020). Pressure and inertia sensing drifters for glacial hydrology flow path measurements. The Cryosphere. ISSN 1994-0416. 14(3), s. 1009–1023. doi: 10.5194/tc-14-1009-2020 Fulltekst i vitenarkiv Vis sammendrag

  Glacial hydrology plays an important role in the control of glacier dynamics, of sediment transport, and of fjord and proglacial ecosystems. Surface meltwater drains through glaciers via supraglacial, englacial and subglacial systems. Due to challenging field conditions, the processes driving surface processes in glacial hydrology remain sparsely studied. Recently, sensing drifters have shown promise in river, coastal and oceanographic studies. However, practical experience with drifters in glacial hydrology remains limited. Before drifters can be used as general tools in glacial studies, it is necessary to quantify the variability of their measurements. To address this, we conducted repeated field experiments in a 450 m long supraglacial channel with small cylindrical drifters equipped with pressure, magnetometer, acceleration and rotation rate sensors and compared the results. The experiments (n=55) in the supraglacial channel show that the pressure sensors consistently yielded the most accurate data, where values remained within ±0.11 % of the total pressure time-averaged mean (95 % confidence interval). Magnetometer readings also exhibited low variability across deployments, maintaining readings within ±2.45 % of the time-averaged mean of the magnetometer magnitudes. Linear acceleration measurements were found to have a substantially higher variability of ±34.4 % of the time-averaged mean magnitude, and the calculated speeds remained within ±24.5 % of the time-averaged mean along the flow path. Furthermore, our results indicate that prominent shapes in the sensor records are likely to be linked to variations in channel morphology and the associated flow field. Our results show that multimodal drifters can be a useful tool for field measurements inside supraglacial channels. Future deployments of drifters into englacial and subglacial channels promise new opportunities for determining hydraulic and morphologic conditions from repeated measurements of such inaccessible environments.

• Alexander, Andreas; Obu, Jaroslav; Schuler, Thomas; Kääb, Andreas & Christiansen, Hanne H (2020). Subglacial permafrost dynamics and erosion inside subglacial channels driven by surface events in Svalbard. The Cryosphere. ISSN 1994-0416. 14( 11), s. 4217–4231. doi: 10.5194/tc-14-4217-2020 Fulltekst i vitenarkiv
• Alexander, Andreas; Obu, Jaroslav; Schuler, Thomas; Kääb, Andreas & Christiansen, Hanne H (2020). Subglacial permafrost dynamics and erosion inside subglacial channels driven by surface events in Svalbard. The Cryosphere Discussions. ISSN 1994-0432. doi: 10.5194/tc-2020-124

Se alle arbeider i Cristin

• Alexander, Andreas (2021). InnovateGLOF: Interdisciplinary observations of the Setevatnet Glacier Lake Outburst Flood.
• Alexander, Andreas (2021). InnovateGLOF: Interdisciplinary observations of the Setevatnet Glacier Lake Outburst Flood.
• Alexander, Andreas (2020). Sensing drifters as tool for glacial hydrology flow path measurements.
• Alexander, Andreas (2020). Go with the flow - Glacier investigations with drifters.
• Alexander, Andreas (2020). Subglacial permafrost dynamics and erosion inside subglacial channels driven by surface events.
• Tuhtan, J.A.; Alexander, Andreas; Kruusma, Maarja & Fuentes-Pérez, J.F. (2020). Multiscale change detection in a supraglacial stream using surface drifters.
• Alexander, Andreas (2020). New insights into glacial hydrology.
• Alexander, Andreas; Piho, Laura & Kruusma, Maarja (2020). Topology and pressure distribution reconstruction of an englacial channel.
• Alexander, Andreas; Obu, Jaroslav; Schuler, Thomas; Kääb, Andreas & Christiansen, Hanne H (2020). Subglacial permafrost dynamics and erosion inside subglacial channels driven by surface events in Svalbard.
• Alexander, Andreas (2019). Winter rain induced soft-bed warming - A potential acceleration mechanism.
• Alexander, Andreas; Kruusma, Maarja; Tuhtan, Jeffrey; Hodson, Andrew; Schuler, Thomas & Kääb, Andreas (2019). Sensing drifters as tool for glacial hydrology measurements.
• Alexander, Andreas; Kruusma, Maarja; Tuhtan, Jeffrey; Hodson, Andrew; Schuler, Thomas & Kääb, Andreas (2019). Sensing drifters as tool for glacial hydrology measurements.
• Alexander, Andreas (2021). Measuring glacial channel hydrology. Institutt for Geofag. ISSN 1501-7710. Vis sammendrag

  Glacier hydrology describes water movement around, on, in and under glaciers. It plays an important role for glacier flow and thus ice transport into the sea and the associated sea level rise. It is further relevant for nutrient transport and release into ecosystems, for hydropower, and for drinking water supply in glaciated regions. Glacier related flood events are additionally a frequent geohazard, emphasizing the importance of accurate knowledge of glacier hydrology. This knowledge is, however, very limited due to general inaccessibility of glacial subsurface flows and thus lack of direct observations and technologies that could provide them. The present thesis therefore develops novel technologies, allowing to observe and study water flow inside glacial channels in detail, and applies them on Svalbard glaciers. For this, sensing drifters are proposed and their statistical repeatability tested. The instruments are then used to study water flow over glacier surfaces. Further, a method to reconstruct flow paths from drifter data is proposed and showcased with the example of a channel within a glacier. Additional speleological investigations provide permafrost temperatures under Svalbard glaciers and highlight the importance of meteorological glacier surface conditions for temperature and erosion of the glacier bed.

Se alle arbeider i Cristin