Publikasjoner
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Dar, Shaakir; Silantyeva, Olga; Ala-aho, Pertti; Walter, Benjamin; Hulth, John & Hyöky, Valtteri
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(2026).
Snow Structure Modulates the Isotopic Imprint of Sublimation.
EGUsphere.
doi:
10.5194/egusphere-2026-2589.
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Abstract. Sublimation modifies the stable isotopic composition of snow. The physical controls governing this imprint, particularly the interplay between isotopic fractionation, snow structure, and airflow, remain poorly constrained. Current surface-exchange models commonly treat sublimation fractionation as a function of atmospheric forcing and boundary-layer exchange, with limited explicit representation of snow structural state. Here, we present controlled wind-tunnel experiments examining sublimation-driven isotopic changes (δ¹⁸O, δ²H, and d-excess) in three contrasting snow types (laboratory snow, fresh natural snow, and old natural snow) under varied airflow regimes, ambient humidity, and basal-to-air temperature contrasts. We show that airflow is the dominant experimental control on sublimation mass loss, but bulk isotopic change does not scale directly with mass loss, revealing a partial decoupling between sublimation magnitude and isotopic modification. High airflow produced the smallest isotopic change per unit mass loss, consistent with strong turbulent exchange reducing the isotopic imprint of sublimation. However, absolute isotopic change varied systematically with snow structural state, scaling strongly with bulk porosity in natural snow. This structural dependence weakened after mass normalization for δ¹⁸O and δ²H, but persisted for d-excess, suggesting that properties associated with porosity influence effective kinetic fractionation in addition to cumulative isotopic change. Laboratory snow deviated from this behavior: despite overlapping the porosity range of natural snow, it showed no porosity-isotopic change relationship. This suggests that bulk porosity alone is insufficient to capture the structural controls on isotopic response to sublimation. Within a relative snow-type comparison, the Craig–Gordon model systematically overpredicted δ¹⁸O and δ²H enrichment and underpredicted the range of d-excess change. The systematic nature of these discrepancies suggests that parameter uncertainty alone is unlikely to explain the mismatch and points to missing representation of internal vapor transport through the snow pore network. Our study shows that sublimation rate alone is insufficient to predict isotopic modification; snow structural state must be considered alongside atmospheric forcing in models of sublimation-driven isotopic evolution. Snow structural state can therefore impose a systematic overprint on isotopic signals in snow archives and meltwater that structure-independent models are likely to misrepresent.
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Nanni, Ugo; Bouchayer, Coline Lili Mathy; Åkesson, Henning; Lefeuvre, Pierre-Marie; Mannerfelt, Erik Schytt & Köhler, Andreas
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(2025).
Observed positive feedback between surface ablation and crevasse formation drives glacier acceleration and potential surge.
Nature Communications.
16(1).
doi:
10.1038/s41467-025-66349-9.
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Sudden glacier acceleration and instability, e.g. surges, strongly influence glacier ice loss. However, lack of in-situ observations of the involved processes hampers our ability to understand, quantify and model such a role. We present an analysis of the initiation of a surge (Kongsvegen glacier, Svalbard), focusing on the interplay between climatic and glacier-specific drivers. We integrate two decades of in-situ observations (GNSS, borehole and surface seismometers) with runoff simulations, and remotely sensed surface-elevation changes. We show that initial glacier thinning led to localized acceleration and crevassing. Then, we show that stronger surface melt enabled meltwater to reach the glacier bed. This input promotes high basal water pressure and glacier sliding, and in turn further surface crevassing. Our observations suggest that this positive feedback leads to the expansion of the initially localized instability. Our findings highlight mechanisms that could trigger glacier instabilities under a warming atmosphere beyond the High Arctic.
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Hove, Alouette van; Aalstad, Kristoffer; Lind, Vibeke; Arndt, Claudia; Odongo, Vincent & Ceriani, Rodolfo
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(2025).
Inferring methane emissions from African livestock by fusing drone, tower, and satellite data.
Biogeosciences.
ISSN 1726-4170.
22(16),
s. 4163–4186.
doi:
10.5194/bg-22-4163-2025.
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Considerable uncertainties and unknowns remain in the regional mapping of methane sources, especially in the extensive agricultural areas of Africa. To address this issue, we developed an observing system that estimates methane emission rates by assimilating drone and flux tower observations into an atmospheric dispersion model. We used our novel Bayesian inference approach to estimate emissions from various ruminant livestock species in Kenya, including diverse herds of cattle, goats, and sheep, as well as camels, for which methane emission estimates are particularly sparse. Our Bayesian estimates aligned with Tier 2 emission values of the Intergovernmental Panel on Climate Change. In addition, we observed the hypothesized increase in methane emissions after feeding. Our findings suggest that the Bayesian inference method is more robust under non-stationary wind conditions compared to a conventional mass balance approach using drone observations. Furthermore, the Bayesian inference method performed better in quantifying emissions from weaker sources, estimating methane emission rates as low as 100 g h−1. We found a ± 50 % uncertainty in emission rate estimates for these weaker sources, such as sheep and goat herds, which reduced to ± 12 % for stronger sources, like cattle herds emitting 1000–1500 g h−1. Finally, we showed that radiance anomalies identified in hyperspectral satellite data can inform the planning of flight paths for targeted drone missions in areas where source locations are unknown, as these anomalies may serve as indicators of potential methane sources. These promising results demonstrate the efficacy of the Bayesian inference method for source term estimation. Future applications of drone-based Bayesian inference could extend to estimating methane emissions in Africa and other regions from various sources with complex spatiotemporal emission patterns, such as wetlands, landfills, and wastewater disposal sites. The Bayesian observing system could thereby contribute to the improvement of emission inventories and verification of other emission estimation methods.
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Bouchayer, Coline Lili Mathy; Nanni, Ugo; Lefeuvre, Pierre-Marie; Hulth, John; Schmidt, Louise Steffensen & Kohler, Jack
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(2024).
Multi-scale variations of hydro-mechanical conditions at the base of the surge-type glacier Kongsvegen, Svalbard.
The Cryosphere.
ISSN 1994-0416.
18(6),
s. 2939–2968.
doi:
10.5194/tc-18-2939-2024.
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The flow of glaciers is largely controlled by changes at the ice–bed interface, where basal slip and sediment deformation drive basal glacier motion. Determining subglacial conditions and their responses to hydraulic forcing remains challenging due to the difficulty of accessing the glacier bed. Here, we monitor the interplay between surface runoff and hydro-mechanical conditions at the base of the Kongsvegen glacier in Svalbard. From July 2021 to August 2022, we measured both subglacial water pressure and till strength. Additionally, we derived median values of subglacial hydraulic gradient and radius of channelized subglacial drainage system from seismic power, recorded at the glacier surface. To characterize the variations in the subglacial conditions caused by changes in surface runoff, we investigate the variations of the following hydro-mechanical properties: measured water pressure, measured sediment ploughing forces, and derived hydraulic gradient and radius, over seasonal, multi-day, and diurnal time
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Filhol, Simon; Lefeuvre, Pierre-Marie; Ibañez, Juan David; Hulth, John; Hudson, Stephen & Gallet, Jean-Charles
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(2023).
A new approach to meteorological observations on remote polar glaciers using open-source internet of things technologies.
Frontiers in Environmental Science.
11.
doi:
10.3389/fenvs.2023.1085708.
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Key regions of the world lack sufficient infrastructure to collect geophysical observations, often due to logistical challenges such as difficult accessibility and cost. With the advent of Internet-of-Things (IoT) technologies and low-cost electronics, it is possible today to build monitoring systems collecting spatially distributed, in-situ data with real-time connectivity to online servers for immediate and long-term usage at costs comparable to those of a single autonomous weather station. We present here a custom-built, modular system that collects quality data, and, that is, robust to adverse meteorological conditions and lack of energy. It integrates commercial and custom-built sensors connected to a node (main device) that manages power, data and radio communication. Data is sent to gateways and then to a server that parses, stores and quality controls the data. We deployed two networks in the vicinity of Ny-Ålesund in Svalbard, and operated from May 2021 to April 2022 to measure meteorological and glaciological variables. Our system collected reliable data and had sufficient power resources to survive 4–5 months of darkness during the polar night. Here, we present the design considerations and performance metrics, report our lessons learned from this challenging deployment, and suggest pathways for future improvements.
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Hulth, John; Denby, Cecilie Rolstad & Hock, Regine
(2013).
Estimating glacier snow accumulation from backward calculation of melt and snowline tracking.
Annals of Glaciology.
ISSN 0260-3055.
54(62),
s. 1–7.
doi:
10.3189/172756413807342965.
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Hulth, John
(2010).
Instruments and Methods: Using a draw-wire sensor to continuously monitor glacier melt.
Journal of Glaciology.
ISSN 0022-1430.
56(199),
s. 922–924.
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ABSTRACT. A draw-wire sensor has successfully been used to measure surface lowering due to net ablation of a glacier. A thin steel wire attached to a weight is inserted and frozen into a borehole in the ice. The draw-wire sensor, installed on a tetrahedron on the surface, retracts the wire as the snow or ice melts. Relative surface lowering of the melting surface is recorded in a data logger and may be converted to mass loss. The instrument continuously logs net ablation over several melt seasons and has the potential to be used extensively in future studies of glacier melt, whenever high temporal resolution and precision are required.
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Hulth, John; Denby, Cecilie Rolstad; Trondsen, Karoline & Rødby, Ragnhild Wedøe
(2010).
Surface mass and energy balance of Sørbreen, Jan Mayen, 2008.
Annals of Glaciology.
ISSN 0260-3055.
51(55),
s. 110–119.
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ABSTRACT. Mass-balance measurements were initiated in 2007/08 on Sørbreen, Jan Mayen, including operation of automatic weather stations in the ablation zone. Mean daily melt rate is 3.6cmw.e. d?1 for the investigated snow-free period of 115 days in June?September 2008. During this period, the net radiation is the largest contributor to melt. However, the relative contribution is highest in June (81%) and less in September (21%). The net longwave radiation is negative, acting as a heat sink. The climate on JanMayen is polar maritime with generally high humidity and overcast conditions. This leads to a positive latent heat flux, which represents condensation to the glacier surface. Persistent temperature inversions on the island lead to non-linear lapse rates and an ablation profile where melt does not necessarily decrease with increased elevation. A comparison of air temperatures on the glacier and twice-daily radiosonde ascents from the meteorological station, 20 km away from the glacier, shows that air temperatures at corresponding elevations are highly correlated (R2 = 0.94?0.96). This indicates that radiosonde temperature profiles can be valuable for determining lapse rates for melt modeling of the glacier.
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Hove, Alouette van; Aalstad, Kristoffer; Lind, Vibeke; Arndt, Claudia; Odongo, Vincent & Ceriani, Rodolfo
[Vis alle 9 forfattere av denne artikkelen]
(2025).
Inferring methane emissions from African livestock by fusing drone, tower, and satellite data.
9th International Greenhouse Gas and Animal Agriculture (GGAA2025) conference.
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Schuler, Thomas; Nanni, Ugo; Bouchayer, Coline Lili Mathy; Åkesson, Henning; Lefeuvre, Pierre-Marie & Mannerfelt, Erik Schytt
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(2024).
Observed weakening of glacier ice-bed interface caused by climatic and hydro-mechanical feedbacks: towards glacier-wide acceleration?
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Stronger and more widespread surface melt may alter the flow of glaciers and ice sheets and trigger instability. However, observational deficiencies hamper our ability to better understand and thus predict such responses. We deployed surface and borehole seismometers along the centerline of a High Arctic glacier in Svalbard. The records span over six years and are analyzed in relation to the measured increase of surface velocity. We complement our seismic analysis (icequakes and seismic noise) with long-term measurements of glacier-surface velocity, surface-elevation changes, and runoff modeling. Since 2000, we observe glacier thinning and steepening, coinciding with acceleration of up to 1000%. In response, new crevasses have opened and provide access pathways for surface melt water to the base of the glacier, affecting the ice-bed coupling. This mechanism represents a positive hydro-mechanical feedback that fuels further acceleration and crevassing. This feedback may have wider implications for triggering of glacier-wide instabilities, increasing short-term sea-level rise and local hazards. Beyond the Arctic, we suggest that, under a warming atmosphere, glaciers may transition from stable to unstable flow through such a mechanism.
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Filhol, Simon; Schuler, Thomas; Burkhart, John; Hulth, John & Decker, Sven
(2017).
A network of instrumentation to keep track of snow distribution at Finse, Norway.
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Filhol, Simon; Burkhart, John; Schuler, Thomas & Hulth, John
(2016).
A distributed and real-time wireless network of weather stations for wind-blown snow at Finse, Norway.
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Filhol, Simon; Burkhart, John; Schuler, Thomas & Hulth, John
(2016).
Weather stations for wind-blown snow at Finse, Norway: A distributed and real-time wireless network of.
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Filhol, Simon; Burkhart, John; Schuler, Thomas & Hulth, John
(2016).
Capturing snow depth distribution with a low cost and wireless weather station network.
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Burkhart, John; Schuler, Thomas; Tallaksen, Lena M.; Filhol, Simon; Hulth, John & Decker, Sven
(2016).
Snow model validation in Norway at the Land
Atmosphere Interaction in Cold Environments
(LATICE) Finse site.
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Denby, Cecilie Rolstad & Hulth, John
(2012).
Estimating glacier snow accumulation from backward calculation of melt and snowline tracking.
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Denby, Cecilie Rolstad; Malnes, Eirik; Burud, Ingunn; Hulth, John & Hock, Regine
(2012).
Envisat ASAR and meteorological measurments for determination of the spatial extent of glacier snow melt on Jan Mayen, 2009.
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Denby, Cecilie, Rolstad & Hulth, John
(2011).
Assessment of differentiated surface elevation data from 1949, 1975 and 2008 for estimates of ice-volume changes at Jan Mayen.
Journal of Glaciology.
ISSN 0022-1430.
57(205),
s. 976–980.
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Hulth, John; Rolstad, Cecilie & Hock, Regine
(2009).
Radiosonde data for temperature lapse rates and radiation transmissivity indexs in a distributed temperature-index melt model of Sørbreen, Jan Mayen.
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Rolstad, Cecilie & Hulth, John
(2009).
The direct glaciological mass- and energy balance of Sørbreen, Jan Mayen, for the ablation season 2008.
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Hock, Regine & Hulth, John
(2008).
Mass balance of Storglaciären, Sweden: Re-evaluation and error assessment.
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Hock, Regine & Hulth, John
(2008).
Mass Balance of Storglaciären, Sweden: Assessment of uncertainties.
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Hulth, John & Hock, Regine
(2008).
Statistical analysis of the spatial and temporal variability of winter mass balance of Storglaciären.
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Publisert
14. des. 2015 16:02
- Sist endret
7. sep. 2023 13:30
