| 1. |
- Charalampidis, Charalampos, 1983-, et al.
(author)
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Thermal tracing of retained meltwater in the lower accumulation area of the Southwestern Greenland ice sheet
- 2016
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In: Annals of Glaciology. - : International Glaciological Society. - 0260-3055 .- 1727-5644. ; 57:72, s. 1-10
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Journal article (peer-reviewed)abstract
- We present in situ firn temperatures from the extreme 2012 melt season in the southwestern lower accumulation area of the Greenland ice sheet. The upper 2.5 m of snow and firn was temperate during the melt season, when vertical meltwater percolation was inefficient due to a c. 5.5 m thick ice layer underlying the temperate firn. Meltwater percolation and refreezing beneath 2.5 m depth only occurred after the melt season. Deviations from temperatures predicted by pure conductivity suggest that meltwater refroze in discrete bands at depths of 2.0–2.5, 5.0–6.0 and 8.0–9.0 m. While we find no indication of meltwater percolation below 9 m depth or complete filling of pore volume above, firn at 10 and 15 m depth was respectively 4.2–4.5 degrees C and 1.7 degrees C higher than in a conductivity-only simulation. Even though meltwater percolation in 2012 was inefficient, firn between 2 and 15 m depth the following winter was on average 4.7 degrees C warmer due to meltwater refreezing. Our observations also suggest that the 2012 firn conditions were preconditioned by two warm summers and ice layer formation in 2010 and 2011. Overall, firn temperatures during the years 2009–13 increased by 0.6 degrees C.
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| 2. |
- Åström, Jan, et al.
(author)
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Fragmentation theory reveals processes controlling iceberg size distributions
- 2021
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In: Journal of Glaciology. - : Cambridge University Press (CUP). - 0022-1430 .- 1727-5652. ; 67, s. 603-612
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Journal article (peer-reviewed)abstract
- Iceberg calving strongly controls glacier mass loss, but the fracture processes leading to iceberg formation are poorly understood due to the stochastic nature of calving. The size distributions of icebergs produced during the calving process can yield information on the processes driving calving and also affect the timing, magnitude, and spatial distribution of ocean fresh water fluxes near glaciers and ice sheets. In this study, we apply fragmentation theory to describe key calving behaviours, based on observational and modelling data from Greenland and Antarctica. In both regions, iceberg calving is dominated by elastic-brittle fracture processes, where distributions contain both exponential and power law components describing large-scale uncorrelated fracture and correlated branching fracture, respectively. Other size distributions can also be observed. For Antarctic icebergs, distributions change from elastic-brittle type during 'stable' calving to one dominated by grinding or crushing during ice shelf disintegration events. In Greenland, we find that iceberg fragment size distributions evolve from an initial elastic-brittle type distribution near the calving front, into a steeper grinding/crushing-type power law along-fjord. These results provide an entirely new framework for understanding controls on iceberg calving and how calving may react to climate forcing.
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| 4. |
- Seoane Martinez, Fernando, 1976, et al.
(author)
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The effect of the scalp and the skull bone in the total impedivity of the neonatal head and its implications in the detection of brain cellular edema
- 2005
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In: The 3rd European Medical and Biological Engineering Conference EMBEC´05. IFBME European Conference on BME. - Prague : IFMBE. - 1727-1983. ; 11:1
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Conference paper (peer-reviewed)abstract
- Hypoxic-ischemic encephalopathy (HIE) affects severely and frequently on newborns and yet not an efficient detection method has been implemented to assist the early initiation of a saving therapy. Invasive measurements of electrical bioimpedance can be used to detect the changes in the electrical properties of brain tissue as a consequence of the hypoxic cellular edema. In the case of non-invasive measurement the skull and the scalp will modified the measurements in a certain way. In this work, using numerical calculations on a four-concentric spheres model, we study the contribution of the scalp and the skull bone to the total equivalent impedivity, complex resistivity, of the neonatal head and its effect on the non-invasive detection of brain cellular edema. The results confirm the importance of the reactive part of the impedivity on the electrical bioimpedance monitoring of hypoxic brain damage.
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