| 1. |
- Hock, R, et al.
(författare)
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High Mountain Areas
- 2019
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Ingår i: IPCC Special Report on the Ocean and Cryosphere in a Changing Climate. - : IPCC - Intergovernmental Panel on Climate Change. ; , s. 131-202
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- The cryosphere (including, snow, glaciers, permafrost, lake and river ice) is an integral element of high- mountain regions, which are home to roughly 10% of the global population. Widespread cryosphere changes affect physical, biological and human systems in the mountains and surrounding lowlands, with impacts evident even in the ocean. Building on the IPCC’s Fifth Assessment Report (AR5), this chapter assesses new evidence on observed recent and projected changes in the mountain cryosphere as well as associated impacts, risks and adaptation measures related to natural and human systems. Impacts in response to climate changes independently of changes in the cryosphere are not assessed in this chapter. Polar mountains are included in Chapter 3, except those in Alaska and adjacent Yukon, Iceland, and Scandinavia, which are included in this chapter.
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| 2. |
- Kienholz, C., et al.
(författare)
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Geodeticmass balance of surge-type Black Rapids Glacier, Alaska, 1980-2001-2010, including role of rockslide deposition and earthquake displacement
- 2016
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Ingår i: Journal of Geophysical Research - Earth Surface. - 2169-9003 .- 2169-9011. ; 121:12, s. 2358-2380
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Tidskriftsartikel (refereegranskat)abstract
- We determine the geodetic mass balance of surge-type Black Rapids Glacier, Alaska, for the time periods 1980-2001 and 2001-2010 by combining modern interferometric synthetic aperture radar (InSAR)-derived digital elevation models (DEMs), DEMs derived from archival aerial imagery, laser altimetry data, and in situ surface elevation measurements. Our analysis accounts for both the large rockslides and terrain displacements caused by the 2002 M7.9 earthquake on the Denali fault, which runs through Black Rapids Glacier. To estimate uncertainties, we apply Monte Carlo simulations. For the earthquake-triggered rockslides we find a volume of 56.62 +/- 2.86 x 10(6) m(3), equivalent to an average debris thickness of 4.44 +/- 0.24 m across the 11.7 km(2) deposit area on the glacier. Terrain displacement due to the earthquake corresponds to an apparent glacier volume change of -53.1 x 106 m(3), which would cause an apparent specific mass balance of -0.19 meter water equivalent (mwe) if not taken into account. The geodetic mass balance of Black Rapids Glacier is -0.48 +/- 0.07 mwe a(-1) for the entire 30 year period, but more negative for the period 2001-2010 (-0.64 +/- 0.11 mwe a(-1)) than the period 1980-2001 (-0.42 +/- 0.11 mwe a(-1)), in agreement with trends indicated by in situ mass balance measurements. Elevation data indicate no net thickening of the surge reservoir between 1980 and 2010, in contrast to what is expected during the quiescent phase. A surge of Black Rapids Glacier in the near future is thus considered unlikely.
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| 3. |
- Kong, Wan-Yee, et al.
(författare)
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Validation of Serial Alberta Stroke Program Early CT Score as an Outcome Predictor in Thrombolyzed Stroke Patients.
- 2017
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Ingår i: Journal of Stroke & Cerebrovascular Diseases. - : Elsevier BV. - 1052-3057 .- 1532-8511. ; 26:10, s. 2264-2271
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: The Alberta Stroke Program Early CT Score (ASPECTS) on baseline imaging is an established predictor of functional outcome in anterior circulation acute ischemic stroke (AIS). We studied ASPECTS before intravenous thrombolysis (IVT) and at 24 hours to assess its prognostic value.METHODS: Data for consecutive anterior circulation AIS patients treated with IVT from 2006 to 2013 were extracted from a prospectively managed registry at our tertiary center. Pre-thrombolysis and 24-hour ASPECTS were evaluated by 2 independent neuroradiologists. Outcome measures included symptomatic intracranial hemorrhage (SICH), modified Rankin Scale (mRS) at 90 days, and mortality. Unfavorable functional outcome was defined by mRS >1. Dramatic ASPECTS progression (DAP) was defined as deterioration in ASPECTS by 6 points or more.RESULTS: Of 554 AIS patients thrombolyzed during the study period, 400 suffered from anterior circulation infarction. The median age was 65 years (interquartile range (IQR): 59-70) and the median National Institutes of Health Stroke Scale score was 18 points (IQR: 12-22). Compared with the pre-IVT ASPECTS (area under the curve [AUC] = .64, 95% confidence interval [CI]: .54-.65, P = .001), ASPECTS on the 24-hour CT scan (AUC = .78, 95% CI: .73-.82, P < .001), and change in ASPECTS (AUC = .69, 95% CI: .64-.74, P < .001) were better predictors of unfavorable functional outcome at 3 months. DAP, noted in 34 (14.4%) patients with good baseline ASPECTS (8-10 points), was significantly associated with unfavorable functional outcome (odds ratio [OR]: 9.91, 95% CI: 3.37-29.19, P ≤ .001), mortality (OR: 21.99, 95% CI: 7.98-60.58, P < .001), and SICH (OR: 8.57, 95% CI: 2.87-25.59, P < .001).CONCLUSION: Compared with the pre-thrombolysis score, ASPECTS measured at 24 hours as well as serial change in ASPECTS is a better predictor of 3-month functional outcome.
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| 4. |
- Young, Joanna C., et al.
(författare)
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The challenge of monitoring glaciers with extreme altitudinal range : mass-balance reconstruction for Kahiltna Glacier, Alaska
- 2018
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Ingår i: Journal of Glaciology. - : CAMBRIDGE UNIV PRESS. - 0022-1430 .- 1727-5652. ; 64:243, s. 75-88
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Tidskriftsartikel (refereegranskat)abstract
- Glaciers spanning large altitudinal ranges often experience different climatic regimes with elevation, creating challenges in acquiring mass-balance and climate observations that represent the entire glacier. We use mixed methods to reconstruct the 1991-2014 mass balance of the Kahiltna Glacier in Alaska, a large (503 km(2)) glacier with one of the greatest elevation ranges globally (264-6108m a. s.l.). We calibrate an enhanced temperature index model to glacier-wide mass balances from repeat laser altimetry and point observations, finding a mean net mass-balance rate of -0.74 mw.e. a(-1)(+/-sigma = 0.04, std dev. of the best-performing model simulations). Results are validated against mass changes from NASA's Gravity Recovery and Climate Experiment (GRACE) satellites, a novel approach at the individual glacier scale. Correlation is strong between the detrended model-and GRACE-derived mass change time series (R-2 = 0.58 and p << 0.001), and between summer (R-2 = 0.69 and p = 0.003) and annual (R-2 = 0.63 and p = 0.006) balances, lending greater confidence to our modeling results. We find poor correlation, however, between modeled glacier-wide balances and recent single-stake monitoring. Finally, we make recommendations for monitoring glaciers with extreme altitudinal ranges, including characterizing precipitation via snow radar profiling.
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