| 1. |
- Pfeffer, W. Tad, et al.
(författare)
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The Randolph Glacier Inventory : a globally complete inventory of glaciers
- 2014
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Ingår i: Journal of Glaciology. - 0022-1430 .- 1727-5652. ; 60:221, s. 537-552
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Tidskriftsartikel (refereegranskat)abstract
- The Randolph Glacier Inventory (RGI) is a globally complete collection of digital outlines of glaciers, excluding the ice sheets, developed to meet the needs of the Fifth Assessment of the Intergovernmental Panel on Climate Change for estimates of past and future mass balance. The RGI was created with limited resources in a short period. Priority was given to completeness of coverage, but a limited, uniform set of attributes is attached to each of the similar to 198 000 glaciers in its latest version, 3.2. Satellite imagery from 1999-2010 provided most of the outlines. Their total extent is estimated as 726 800 +/- 34 000 km(2). The uncertainty, about +/- 5%, is derived from careful single-glacier and basin-scale uncertainty estimates and comparisons with inventories that were not sources for the RGI. The main contributors to uncertainty are probably misinterpretation of seasonal snow cover and debris cover. These errors appear not to be normally distributed, and quantifying them reliably is an unsolved problem. Combined with digital elevation models, the RGI glacier outlines yield hypsometries that can be combined with atmospheric data or model outputs for analysis of the impacts of climatic change on glaciers. The RGI has already proved its value in the generation of significantly improved aggregate estimates of glacier mass changes and total volume, and thus actual and potential contributions to sea-level rise.
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| 2. |
- Arendt, Anthony A., et al.
(författare)
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Glacier changes in Alaska : can mass-balance models explain GRACE mascon trends?
- 2009
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Ingår i: Annals of Glaciology. - 0260-3055 .- 1727-5644. ; 50:50, s. 148-154
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Tidskriftsartikel (refereegranskat)abstract
- Temperature and precipitation data from three weather stations in the St Elias Mountains of Alaska and northwestern Canada were used to drive one-dimensional (1-D) (elevation-dependent) and 0-D degree-day mass-balance models. Model outputs were optimized against a 10 day resolution time series of mass variability during 2003-07 obtained from Gravity Recovery and Climate Experiment (GRACE) mass concentration (mascon) solutions. The models explained 52-60% of the variance in the GRACE time series. Modelled mass variations matched the phase of the GRACE observations, and all optimized model parameters were within the range of values determined from conventional mass-balance and meteorological observations. We describe a framework for selecting appropriate weather stations and mass-balance models to represent glacier variations of large regions. There is potential for extending these calibrated mass-balance models forwards or backwards in time to construct mass-balance time series outside of the GRACE measurement window.
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| 3. |
- Gardner, Alex S., et al.
(författare)
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A Reconciled Estimate of Glacier Contributions to Sea Level Rise : 2003 to 2009
- 2013
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 340:6134, s. 852-857
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Tidskriftsartikel (refereegranskat)abstract
- Glaciers distinct from the Greenland and Antarctic Ice Sheets are losing large amounts of water to the world's oceans. However, estimates of their contribution to sea level rise disagree. We provide a consensus estimate by standardizing existing, and creating new, mass-budget estimates from satellite gravimetry and altimetry and from local glaciological records. In many regions, local measurements are more negative than satellite-based estimates. All regions lost mass during 2003-2009, with the largest losses from Arctic Canada, Alaska, coastal Greenland, the southern Andes, and high-mountain Asia, but there was little loss from glaciers in Antarctica. Over this period, the global mass budget was -259 +/- 28 gigatons per year, equivalent to the combined loss from both ice sheets and accounting for 29 +/- 13% of the observed sea level rise.
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| 4. |
- Kienholz, Christian, et al.
(författare)
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A new semi-automatic approach for dividing glacier complexes into individual glaciers
- 2013
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Ingår i: Journal of Glaciology. - 0022-1430 .- 1727-5652. ; 59:217, s. 925-937
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Tidskriftsartikel (refereegranskat)abstract
- Many glaciological and hydrological studies require outlines of individual glaciers rather than total ice cover. Here we develop a new semi-automatic algorithm that uses a digital elevation model (DEM) and outlines of glacier complexes to calculate the extents of individual glaciers. The algorithm first applies hydrological modeling tools to a modified DEM to calculate flowsheds. It then merges flowsheds that belong to individual glaciers using a distance-based approach, whose required empirical parameters are derived from the Juneau Icefield area in Alaska. In this region, 2% of similar to 1300 glaciers were misclassified. The algorithm was validated on >25 000 km(2) of ice in other regions in Alaska and on >40 000 km(2) of ice in Arctic Canada, resulting in similar to 2% and similar to 3% misclassified glaciers, respectively. Results indicate that the algorithm is robust provided the DEM and the outlines are of good quality.
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| 5. |
- Kienholz, Christian, et al.
(författare)
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Derivation and analysis of a complete modern-date glacier inventory for Alaska and northwest Canada
- 2015
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Ingår i: Journal of Glaciology. - 0022-1430 .- 1727-5652. ; 61:227, s. 403-420
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Tidskriftsartikel (refereegranskat)abstract
- We present a detailed, complete glacier inventory for Alaska and neighboring Canada using multi-sensor satellite data from 2000 to 2011. For each glacier, we derive outlines and 51 variables, including center-line lengths, outline types and debris cover. We find 86 723 km(2) of glacier area (27 109 glaciers >0.025 km(2)), similar to 12% of the global glacierized area outside ice sheets. Of this area 12.0% is drained by 39 marine-terminating glaciers (74 km of tidewater margin), and 19.3% by 148 lake- and river-terminating glaciers (420 km of lake-/river margin). The overall debris cover is 11%, with considerable differences among regions, ranging from 1.4% in the Kenai Mountains to 28% in the Central Alaska Range. Comparison of outlines from different sources on >2500 km(2) of glacierized area yields a total area difference of similar to 10%, emphasizing the difficulties in accurately delineating debris-covered glaciers. Assuming fully correlated (systematic) errors, uncertainties in area reach 6% for all Alaska glaciers, but further analysis is needed to explore adequate error correlation scales. Preliminary analysis of the glacier database yields a new set of well-constrained area/length scaling parameters and shows good agreement between our area altitude distributions and previously established synthetic hypsometries. The new glacier database will be valuable to further explore relations between glacier variables and glacier behavior.
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