Utdrattur ur skýrslunni : Effect of climate change on hydrology and hydro-resources in Iceland. Ath. sama skýrslunumer baeði a islenskri og enskri utgafu.
This book is the first comprehensive overview and evaluation of the origins, history and current size and condition of all of Iceland's major glaciers (including Vatnajökull, the largest in Europe) at
Research Article| October 01, 1998 Eight centuries of periodic volcanism at the center of the Iceland hotspot revealed by glacier tephrostratigraphy Gudrún Larsen; Gudrún Larsen 1Science Institute, University of Iceland, Dunhagi 3, IS-107 Reykjavík, Iceland Search for other works by this author on: GSW Google Scholar Magnús T. Gudmundsson; Magnús T. Gudmundsson 1Science Institute, University of Iceland, Dunhagi 3, IS-107 Reykjavík, Iceland Search for other works by this author on: GSW Google Scholar Helgi Björnsson Helgi Björnsson 1Science Institute, University of Iceland, Dunhagi 3, IS-107 Reykjavík, Iceland Search for other works by this author on: GSW Google Scholar Author and Article Information Gudrún Larsen 1Science Institute, University of Iceland, Dunhagi 3, IS-107 Reykjavík, Iceland Magnús T. Gudmundsson 1Science Institute, University of Iceland, Dunhagi 3, IS-107 Reykjavík, Iceland Helgi Björnsson 1Science Institute, University of Iceland, Dunhagi 3, IS-107 Reykjavík, Iceland Publisher: Geological Society of America First Online: 02 Jun 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (1998) 26 (10): 943–946. https://doi.org/10.1130/0091-7613(1998)026<0943:ECOPVA>2.3.CO;2 Article history First Online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation Gudrún Larsen, Magnús T. Gudmundsson, Helgi Björnsson; Eight centuries of periodic volcanism at the center of the Iceland hotspot revealed by glacier tephrostratigraphy. Geology 1998;; 26 (10): 943–946. doi: https://doi.org/10.1130/0091-7613(1998)026<0943:ECOPVA>2.3.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract A record of volcanic activity within the Vatnajökull ice cap has been obtained by combining data from three sources: tephrostratigraphic studies of two outlet glaciers, a 415-m-long ice core from northwestern Vatnajökull, and written records. The record extends back to a.d. 1200 and shows that the volcanic activity has a 130–140 yr period. Intervals of frequent eruptions with recurrence times of three to seven years alternate with intervals of similar duration having much lower eruption frequency. In comparison with other parts of the plate boundary in Iceland, eruption frequency is greater, episodes of unrest are longer, and intervals of low activity are shorter. The high eruption frequency may be the result of a more sustained supply of magma, owing to the area's location above the center of the Iceland mantle plume. When combined with historical data on eruptions and earthquakes, our data indicate that rifting-related activity in Iceland as a whole is periodic and broadly in phase with the volcanic activity within Vatnajökull. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.
Abstract. Area and volume changes and the average geodetic mass balance of the non-surging outlet glaciers of southeast Vatnajökull ice cap, Iceland, during different time periods between ~1890 and 2010, are derived from a multi-temporal glacier inventory. A series of digital elevation models (DEMs) (∼1890, 1904, 1936, 1945, 1989, 2002, 2010) have been compiled from glacial geomorphological features, historical photographs, maps, aerial images, DGPS measurements and a LiDAR survey. Given the mapped bedrock topography we estimate relative volume changes since the end of the Little Ice Age (LIA) ~1890. The variable dynamic response of the outlets, assumed to have experienced similar climate forcing, is related to their different hypsometry, bedrock topography, and the presence of proglacial lakes. In the post-LIA period the glacierized area decreased by 164 km2 and the glaciers had lost 10–30% of their ~1890 area by 2010. The glacier surface lowered by 150–270 m near the terminus and the outlet glaciers collectively lost 60 ± 8 km3 of ice, which is equivalent to 0.154 ± 0.02 mm of sea level rise. The relative volume loss of individual glaciers was in the range of 15–50%, corresponding to a geodetic mass balance between −0.70 and −0.32 m w.e. a−1. The rate of mass loss was most negative in the period 2002–2010, on average −1.34 ± 0.12 m w.e. a−1, which lists among the most negative mass balance values recorded worldwide in the early 21st century. From the data set of volume and area of the outlets, spanning the 120 years post-LIA period, we evaluate the parameters of a volume-area power law scaling relationship.
This paper presents an analysis of the solutions for a steady state latent heat polynya generatedby an applied wind stress acting over a semi-enclosed channel using: (a) a dynamic–thermodynamicsea ice model, and (b) a steady state flux model. We examine what processes in the seaice model are responsible for the maintenance of the polynya and how sensitive the results areto the choice of rheological parameters. We find that when the ice is driven onshore by anapplied wind stress, a consolidated ice pack forms downwind of a zone of strong convergencein the ice velocities. The build-up of internal stresses within the consolidated ice pack becomesa crucial factor in the formation of this zone and results in a distinct polynya edge. Furthermore, within the ice pack the across-channel ice velocity varies with the across-channel distance. It isdemonstrated that provided this velocity is well represented, the steady state polynya flux modelsolutions are in close agreement with those of the sea ice model. Experiments with the sea icemodel also show that the polynya shape and area are insensitive to (a) the sea ice rheology;(b) the imposition of either free-slip or no-slip boundary conditions. These findings are usedin the development of a simplified model of the consolidated ice pack dynamics, the output ofwhich is then compared with the sea ice model results. Finally, we discuss the relevance of thisstudy for the modelling of the North Water Polynya in northern Baffin Bay.
Albedo is a key variable in the response of glaciers to climate. In Iceland, large albedo variations in the ice caps may be caused by the deposition of volcanic ash (tephra). Sparse in situ field measurements are insufficient to characterize the spatial variation of albedo over the ice caps. Here we evaluate the latest MCD43 MODIS albedo product (collection 6) to monitor albedo over the Icelandic ice caps using albedo from ten automatic weather stations in Vatnajökull and Langjökull as ground truth. We examine the influence of the albedo variability within MODIS pixels by comparing the results with a collection of Landsat scenes. The results indicate a good ability of the MODIS product to characterize the seasonal and interannual albedo changes with correlation coefficients ranging from 0.47 to 0.90 (median 0.84) and a small bias ranging from -0.07 to 0.09. The root-mean square errors (RMSE) ranging from 0.08 and 0.21, is larger than that from previous studies, but we did not discard the retrievals flagged as bad quality to maximize the amount of observations given the frequent cloud obstruction in Iceland. We find a positive but non-significant relationship between the RMSE and the subpixel variability as indicated by the standard deviation of the Landsat albedo within the MODIS pixel (R=0.48). The summer albedo maps and time series computed from the MODIS product show that the albedo decreased significantly after the Eyjafjallajökull and Grímsvötn eruptions in 2010 and 2011 in all the main ice caps (except the northernmost Drangajökull), with albedo reduction up to 0.6 over large regions of the accumulation areas. Following this validation, these data will be assimilated in an energy and mass balance model of to better understand the relative influence of the volcanic and climate forcing to the ongoing mass losses of Icelandic ice caps.
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