Evaluation of pan-Arctic melt-freeze onset in CMIP5 climate models and reanalyses using surface observations     

Jonas Mortin  Rune G. Graversen  Gunilla Svensson 《Climate Dynamics》2014,42(7-8):2239-2257

The seasonal melt-freeze transitions are fundamental features of the Arctic climate system. The representation of the pan-Arctic melt and freeze onset (north of 60°N) is assessed in two reanalyses and eleven CMIP5 global circulation models (GCMs). The seasonal melt-freeze transitions are retrieved from surface air temperature (SAT) across the land and sea-ice domains and evaluated against surface observations. While monthly averages of SAT are reasonably well represented in models, large model-observation and model–model disparities of timing of melt and freeze onset are evident. The evaluation against surface observations reveals that the ERA-Interim reanalysis performs the best, closely followed by some of the climate models. GCMs and reanalyses capture the seasonal melt-freeze transitions better in the central Arctic than in the marginal seas and across the land areas. The GCMs project that during the 21st century, the summer length—the period between melt and freeze onset—will increase over land by about 1 month at all latitudes, and over sea ice by 1 and 3 months at low and high latitudes, respectively. This larger summer-length increase over sea ice at progressively higher latitudes is related to a retreat of summer sea ice during the 21st century, since open water freezes roughly 40 days later than ice-covered ocean. As a consequence, by the year 2100, the freeze onset is projected to be initiated within roughly 10 days across the whole Arctic Ocean, whereas this transition varies by about 80 days today.  相似文献   

The magnetic fabric of some dolerite intrusions,northeast Spitsbergen; implications for their mode of emplacement     

Erik Halvorsen 《Earth and Planetary Science Letters》1974,21(2):127-133

The titanomagnetite fabric of some dolerites from two areas of northeast Spitsbergen, Lomfjorden and the Bastian, and Rønnbeck islands have been studied by means of magnetic susceptibility anisotropy measurements. The shape and orientation of the susceptibility ellipsoids were determined with an a.c. bridge. Both areas showed a dominating magnetic foliation in the horizontal plane. A weakly developed preferred orientation of the maximum (K^I) and intermediate (K^II) susceptibility axis within the magnetic foliation plane was found, the K^I-axis striking predominantly E-W and the K^II-axis striking N-S. The magnetic fabric is interpreted as resulting from horizontal movement of magma. It is concluded that the Bastian and Rønnbeck islands are the relics of one or more larger sills.  相似文献   

Formation of tonalite in island arcs by seawater-induced anatexis of mafic rocks; evidence from the Lyngen Magmatic Complex, North Norwegian Caledonides     

Rune S Selbekk  Colin J BrayEdward T.C Spooner 《Chemical Geology》2002,182(1):69-84

The Lyngen Magmatic Complex (LMC) of North Norway, consists of a western suite of layered gabbros of normal-mid oceanic ridge basalt (N-MORB) affinity and an eastern suite of layered gabbronorites, quartz-bearing gabbros and diorites/quartz-diorites of IAT (island-arc tholeiitte) to boninitic affinity. The boundary between the suites is defined by a large-scale ductile shear zone, the Rypdalen shear zone (RSZ). In this shear zone anatectic tonalites were generated by partial melting of the gabbro in the presence of an H₂O bearing fluid phase.Quartz from the tonalites contains early secondary and secondary liquid-dominated inclusions (88-99 wt.% H₂O), with an average salinity of 18 wt.% (calculated as NaCl_eq). Combined gas and ion chromatography shows that the major ions in the fluid are Cl⁻, Ca²⁺, Na⁺ with smaller amounts of K⁺, Mg²⁺, Sr²⁺, Br⁻ and NO₃⁻. The dominant non-H₂O volatile species is N₂ (0.5-10%), and small amounts of CO₂, CH₄ and other hydrocarbons are also present.The cation concentrations in the fluid are variable, due to element exchange during interaction of the fluids with the tonalites, amphibolites and metagabbros of the RSZ. The fluid contributed Na⁺ and K⁺ to the melt and gained Ca²⁺ in exchange, explaining the variable Na⁺/Ca²⁺ ratio of the fluid. The Br⁻ and Cl⁻ contents of the fluid inclusions plot on the same line as evaporating sea water, which strongly suggests a seawater origin for the fluid phase, and a seawater source fits well with other geochemical signatures and the tectonic setting of the LMC.It is suggested that seawater escaped from a subducting slab and was channelled along the Rypdalen shear zone. This caused anatexis of the gabbro, generating tonalitic melts at 0.5-0.9 GPa and 680-800°C.  相似文献   

The Bayesian bridge between simple and universal kriging   总被引：1，自引：0，他引：1  

Henning Omre  Kjetil B. Halvorsen 《Mathematical Geology》1989,21(7):767-786

Kriging techniques are suited well for evaluation of continuous, spatial phenomena. Bayesian statistics are characterized by using prior qualified guesses on the model parameters. By merging kriging techniques and Bayesian theory, prior guesses may be used in a spatial setting. Partial knowledge of model parameters defines a continuum of models between what is named simple and universal kriging in geostatistical terminology. The Bayesian approach to kriging is developed and discussed, and a case study concerning depth conversion of seismic reflection times is presented.  相似文献   

An objective test of earthquake migrations in Turkey     

Rune Olsson 《Tectonophysics》1985,116(3-4)

An objective method for the examination of supposed migration of earthquake epicenters is discussed and tested for the Turkey region.  相似文献   

Absolute dating of the youngest sediments of the Swiss Molasse basin by apatite fission track analysis     

Meinert K. Rahn  Rune Selbekk 《Swiss Journal of Geoscience》2007,100(3):371-381

A set of ash layer samples within the uppermost Upper Freshwater Molasse (OSM) sediments (N and E of Frauenfeld, Switzerland) was dated by apatite fission track (FT) means. The ages indicate an early Tortonian (perhaps latest Serravallian) eruption and sedimentation age of 11.5 ± 0.3 Ma. The age is in agreement with time constraints by Mammalian relicts which point to MN7-8. Due to the position of the ash layers close to the erosional gap and overlying Quaternary cover, the age represents a maximum age for the cessation of OSM sedimentation in the Swiss Molasse Basin. However, the end of Molasse sedimentation in this region had not stopped before the cover of OSM sediments by volcanic ash layers at the Höwenegg volcano (southern Germany), an event further constrained by an apatite FT age of 9.8 (?0.7/+0.8) Ma from a hornblende-bearing ash layer at Höwenegg. An isolated bentonitic ash layer occurring 25 km to the WSW of the main set of dated ashes (near Humlikon) has an age component identical to the OSM ash layers near Frauenfeld. The age suggests a source for this material within the Hegau, but is too young to be related to the volcanic activity at the Kaiserstuhl.The apatites from the ash layer samples show two distinct compositional populations, one very close to a Cl end member and one with apatites of equal proportions of Cl and OH end member. These populations are interpreted to have possibly originated from at least two distinct igneous sources for the ashes, separated by their eruption site or eruption time or both. The distinct compositional data on the volcanic apatites may provide a basis to clarify their origin in future work.  相似文献   

Behaviour of mackerel schools during summer feeding migration in the Norwegian Sea, as observed from fishing vessel sonars   总被引：1，自引：0，他引：1  

Godo  Olav Rune; Hjellvik  Vidar; Iversen  Svein A.; Slotte  Aril; Tenningen  Eirik; Torkelsen  Terje 《ICES Journal of Marine Science》2004,61(7):1093-1099

  相似文献   

Report on Kukk?m?ki's method for computing the levelling effect of atmospheric refraction     

G. A. Rune 《Journal of Geodesy》1950,24(4):432-433

  相似文献   

Low-frequency variability of surface air temperature over the Barents Sea: causes and mechanisms     

Eveline C. van der Linden  Richard Bintanja  Wilco Hazeleger  Rune G. Graversen 《Climate Dynamics》2016,47(3-4):1247-1262

  相似文献   

Large slope deformations detection and monitoring along shores of the Potrerillos dam reservoir,Argentina, based on a small-baseline InSAR approach   总被引：1，自引：0，他引：1  

Clément Michoud  Valérie Baumann  Tom Rune Lauknes  Ivanna Penna  Marc-Henri Derron  Michel Jaboyedoff 《Landslides》2016,13(3):451-465

The Argentina National Road 7 that crosses the Andes Cordillera within the Mendoza province to connect Santiago de Chile and Buenos Aires is particularly affected by natural hazards requiring risk management. Integrated in a research plan that intends to produce landslide susceptibility maps, we aimed in this study to detect large slope movements by applying a satellite radar interferometric analysis using Envisat data, acquired between 2005 and 2010. We were finally able to identify two large slope deformations in sandstone and clay deposits along gentle shores of the Potrerillos dam reservoir, with cumulated displacements higher than 25 mm in 5 years and towards the reservoir. There is also a body of evidences that these large slope deformations are actually influenced by the seasonal reservoir level variations. This study shows that very detailed information, such as surface displacements and above all water level variation, can be extracted from spaceborne remote sensing techniques; nevertheless, the limitations of InSAR for the present dataset are discussed here. Such analysis can then lead to further field investigations to understand more precisely the destabilising processes acting on these slope deformations.  相似文献