Glacier dynamic ice loss quantified through seismic eyes (CalvingSEIS) (avsluttet)

• Giacalone, Giovanni; Barra, Marco; Bonanno, Angelo; Basilone, Gualtiero; Fontana, Ignazio & Calabrò, Monica [Vis alle 15 forfattere av denne artikkelen] (2022). A pattern recognition approach to identify biological clusters acquired by acoustic multi-beam in Kongsfjorden. Environmental Modelling & Software. ISSN 1364-8152. 152. doi: 10.1016/j.envsoft.2022.105401. Fulltekst i vitenarkiv Vis sammendrag

  Svalbard is one of the most intensively studied marine regions in the Artic; here the composition and distribution of marine assemblages are changing under the effect of global change, and marine communities are monitored in order to understand the long-term effects on marine biodiversity. In the present work, acoustic data collected in the Kongsfjorden using multi-beam technology was analyzed to develop a methodology for identifying and classifying 3D acoustic patterns related to fish aggregations. In particular, morphological, energetic and depth features were taken into account to develop a multi-variate classification procedure allowing to discriminate fish species. The results obtained from clustering suggest that from a mathematical point of view three distinct groups could be identified. The proposed approach, that allows to discriminate the acoustic patterns identified in the water column, seems promising for improving the monitoring programs of the marine resources, also in view of the ongoing climate changes.

• Nuth, Christopher; Gilbert, Adrien; Köhler, Andreas; McNabb, Robert Whitfield; Schellenberger, Thomas & Sevestre, Heidi [Vis alle 10 forfattere av denne artikkelen] (2019). Dynamic vulnerability revealed in the collapse of an Arctic tidewater glacier. Scientific Reports. 9. doi: 10.1038/s41598-019-41117-0. Fulltekst i vitenarkiv Vis sammendrag

  Glacier flow instabilities can rapidly increase sea level through enhanced ice discharge. Surge-type glacier accelerations often occur with a decadal to centennial cyclicity suggesting internal mechanisms responsible. Recently, many surging tidewater glaciers around the Arctic Barents Sea region question whether external forces such as climate can trigger dynamic instabilities. Here, we identify a mechanism in which climate change can instigate surges of Arctic tidewater glaciers. Using satellite and seismic remote sensing observations combined with three-dimensional thermo-mechanical modeling of the January 2009 collapse of the Nathorst Glacier System (NGS) in Svalbard, we show that an underlying condition for instability was basal freezing and associated friction increase under the glacier tongue. In contrast, continued basal sliding further upstream increased driving stresses until eventual and sudden till failure under the tongue. The instability propagated rapidly up-glacier, mobilizing the entire 450 km2 glacier basin over a few days as the till entered an unstable friction regime. Enhanced mass loss during and after the collapse (5–7 fold compared to pre-collapse mass losses) combined with regionally rising equilibrium line altitudes strongly limit mass replenishment of the glacier, suggesting irreversible consequences. Climate plays a paradoxical role as cold glacier thinning and retreat promote basal freezing which increases friction at the tongue by stabilizing an efficient basal drainage system. However, with some of the most intense atmospheric warming on Earth occurring in the Arctic, increased melt water can reduce till strength under tidewater glacier tongues to orchestrate a temporal clustering of surges at decadal timescales, such as those observed in Svalbard at the end of the Little Ice Age. Consequently, basal terminus freezing promotes a dynamic vulnerability to climate change that may be present in many Arctic tidewater glaciers.

• Sundfjord, Arild; Albretsen, Jon; Kasajima, Yoshie; Skogseth, Ragnheid; Kohler, Jack & Nuth, Christopher [Vis alle 12 forfattere av denne artikkelen] (2017). Effects of glacier runoff and wind on surface layer dynamics and Atlantic Water exchange in Kongsfjorden, Svalbard; a model study. Estuarine, Coastal and Shelf Science. ISSN 0272-7714. 187, s. 260–272. doi: 10.1016/j.ecss.2017.01.015. Fulltekst i vitenarkiv
• Köhler, Andreas; Nuth, Christopher; Kohler, Jack; Berthier, Etienne; Weidle, Christian & Schweitzer, Johannes (2016). A 15 year record of frontal glacier ablation rates estimated from seismic data. Geophysical Research Letters. ISSN 0094-8276. 43(23), s. 12,155–12,164. doi: 10.1002/2016GL070589. Fulltekst i vitenarkiv Vis sammendrag

  We present a unique time series of continuous glacier frontal ablation rates with weekly resolution over 15 years estimated from seismic calving observations at Kronebreen, Svalbard. Using linear statistical models, we calibrate the seismic record with 7 years of satellite‐derived frontal ablation measurements. The two basic input parameters required for our models are the cumulative duration of individual seismic calving events and the incompleteness of the seismic record to correct for the effect of seismic background noise. Frontal ablation follows the seasonal glacier speedup, peaking 1–2 months after the melt season maximum. Short‐lived peaks are associated with melt and rain events. Cumulative frontal ablation of Kronebreen between 2001 and 2015 is about 4.0 km3 (3.7 Gt), with the greatest annual loss (0.45 km3) between 2013 and 2014 at the onset of the recent accelerated retreat of the glacier. Our approach provides a potential method for monitoring tidewater glaciers worldwide that have sufficiently close seismic instrumentation. This article was originally published in Geophysical Research Letters. © 2016 American Geophysical Union

• Köhler, Andreas; Nuth, Christopher; Schweitzer, Johannes; Weidle, Christian & Gibbons, Steven John (2015). Regional passive seismic monitoring reveals dynamic glacier activity on Spitsbergen, Svalbard. Polar Research. ISSN 0800-0395. 34. doi: 10.3402/polar.v34.26178. Fulltekst i vitenarkiv Vis sammendrag

  Dynamic glacier activity is increasingly observed through passive seismic monitoring. We analysed near-regional-scale seismicity on the Arctic archipelago of Svalbard to identify seismic icequake signals and to study their spatial–temporal distribution within the 14-year period from 2000 until 2013. This is the first study that uses seismic data recorded on permanent broadband stations to detect and locate icequakes in different regions of Spitsbergen, the main island of the archipelago. A temporary local seismic network and direct observations of glacier calving and surging were used to identify icequake sources. We observed a high number of icequakes with clear spectral peaks between 1 and 8 Hz in different parts of Spitsbergen. Spatial clusters of icequakes could be associated with individual grounded tidewater glaciers and exhibited clear seasonal variability each year with more signals observed during the melt season. Locations at the termini of glaciers, and correlation with visual calving observations in situ at Kronebreen, a glacier in the Kongsfjorden region, show that these icequakes were caused dominantly by calving. Indirect evidence for glacier surging through increased calving seismicity was found in 2003 at Tunabreen, a glacier in central Spitsbergen. Another type of icequake was observed in the area of the Nathorstbreen glacier system. Seismic events occurred upstream of the glacier within a short time period between January and May 2009 during the initial phase of a major glacier surge. This study is the first step towards the generation and implementation of an operational seismic monitoring strategy for glacier dynamics in Svalbard.

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• Schweitzer, Johannes; Köhler, Andreas & Weidle, Christian (2018). Regional Seismicity observed with two temporary seismic arrays in Kongsfjorden, Svalbard. Fulltekst i vitenarkiv
• Schweitzer, Johannes; Köhler, Andreas & Weidle, Christian (2018). Two temporary seismic arrays in the high Arctic. Fulltekst i vitenarkiv
• Köhler, Andreas; Buscaino, Giuseppa; Lefeuvre, Pierre-Marie; Maupin, Valerie; Nuth, Christopher & Petlicki, Michal [Vis alle 7 forfattere av denne artikkelen] (2018). Seismic monitoring of glaciers and permafrost: What micro-seismicity and ambient noise can tell us about cryospheric processes in Svalbard. Fulltekst i vitenarkiv
• Köhler, Andreas; Lefeuvre, Pierre-Marie; Nuth, Christopher; Schweitzer, Johannes; Buscaino, Giuseppa & Weidle, Christian [Vis alle 9 forfattere av denne artikkelen] (2018). Monitoring and quantification of frontal ablation at Kronebreen, Svalbard, using records of seismic calving signals. Geophysical Research Abstracts. ISSN 1029-7006. Fulltekst i vitenarkiv
• Köhler, Andreas; Buscaino, Giuseppa; Lefeuvre, Pierre-Marie; Maupin, Valerie; Nuth, Christopher & Petlicki, Michal [Vis alle 8 forfattere av denne artikkelen] (2018). Studying and quantifying glacier dynamics in Svalbard using cryoseismology. Fulltekst i vitenarkiv

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