Coronal heating and solar wind acceleration; gyrotropic electron-proton solar wind

In coronal holes the electron (proton) density is low, and heating of the proton gas produces a rapidly increasing proton temperature in the inner corona. In models with a reasonable electron density in the upper transition region the proton gas becomes collisionless some 0.2 to 0.3 solar radii into the corona. In the collisionless region the proton heat flux is outwards, along the temperature gradient. The thermal coupling to electrons is weak in coronal holes, so the heat flux into the transition region is too small to supply the energy needed to heat the solar wind plasma to coronal temperatures. Our model studies indicate that in models with proton heating the inward heat conduction may be so inefficient that some of the energy flux must be deposited in the transition region to produce the proton fluxes that are observed in the solar wind. If we allow for coronal electron heating, the energy that is needed in the transition region to heat the solar wind to coronal temperatures, may be supplied by heat conduction from the corona.     

Erosional channel incision and the origin of large sediment waves in Trondheimsfjorden,central Norway

An erosional channel and upslope-climbing sediment waves have been observed in Ytre Orkdalsfjorden and the marine fjord branch Gaulosen off the mouth of Gaula River in Trondheimsfjorden, central Norway. The submarine channel (up to 100–150 m wide and 12 m deep) is interpreted as the pathway of hyperpycnal flows and turbidity currents. It can be traced for 20 km on the seafloor from the mouth of Gaula River down to 500 m of water depth. Based on swath bathymetry and seismic data, the sediment waves are shown to have an accumulated thickness of 50–60 m. They are up to 8 m high, have up to 1-km-long crests, and wavelengths of 100–900 m. The sediment waves are attributed to hyperpycnal flows and turbidity currents overflowing the banks of the channel. Many of the sediment waves were instigated by pre-existing topography created by mass movements since early Holocene times.     

Rotational dynamics of subsolar sublimating triaxial comets

A model with subsolar water sublimation on a triaxial, ellipsoidal comet nucleus is presented for the calculation of reactive torques. The resulting differential equations describing the comet's rotation are then Hamiltonian, and gravity-gradients are trivial to include. While effects derived from a weak perturbing function are neither able to change the rotational excitation nor the spin magnitude of the nucleus, it is shown how the spin orientation of comets can change significantly over an orbital run. However, of the four comets studied, 1P, 19P, 46P and the Rosetta target 67P, 19P and 46P were the only objects clearly exhibiting this feature, thereby confirming a technique used to derive the consequences of a more elaborate model of sublimation induced torques. In particular, the rotational parameters of 67P were seen to be very stable, indicating that a highly kinematical model of its rotation for the mapping of the comet's gravitational field during the Rosetta mission can be used. The model's hierarchy with 1P/Halley as the object with highest excitation probability, is consistent with observations.     

The Bam Earthquake of 26 December 2003

The devastating earthquake of 26 December 2003 claimed more than 26,000 lives in the city of Bam and surrounding towns and villages in Southeast Iran, and left the majority of the Bam population homeless. The reason for this tragedy was an unfortunate combination of geological, social and human circumstances. The causative fault practically traversed the city of Bam and the earthquake occurred at a shallow depth. The residential buildings were completely inappropriate for a seismic region, being extremely vulnerable to earthquake shaking, and the earthquake occurred early in the morning when most people were still sleeping. The damage pattern was nearly symmetric about a line 3 km to the west of the surface expression of the Bam fault, and the damage attenuated rapidly with distance from this line. The industrial facilities and the lifelines performed relatively well and experienced slight to moderate damage, but this might have been due to their distance from the earthquake epicentre. However, many of the qanat (traditional subterranean irrigation channels) chains that served the twin cities of Bam and Baravat collapsed. Emergency facilities (hospitals, police and fire stations), schools and the university were destroyed and/or heavily damaged during the earthquake. The geotechnical effects of the earthquake were not significant. There was little evidence that site response effects played a major role in the damage pattern in the city. There were no reports of liquefaction and only minor sliding activity took place during the event. A unique set of strong motion acceleration recordings were obtained at the Bam accelerograph station. The highest peak ground acceleration (nearly 1g) was recorded for the vertical component of the motion. However, the longitudinal component (fault-parallel motion in N–S direction) clearly had the largest energy flux, as well as the largest maximum velocity and displacement.     

Assessment of climate change and associated impact on selected sectors in Poland

The present paper offers a brief assessment of climate change and associated impact in Poland, based on selected results of the Polish–Norwegian CHASE-PL project. Impacts are examined in selected sectors, such as water resources, natural hazard risk reduction, environment, agriculture and health. Results of change detection in long time series of observed climate and climate impact variables in Poland are presented. Also, projections of climate variability and change are provided for time horizons of 2021–2050 and 2071–2100 for two emission scenarios, RCP4.5 and RCP8.5 in comparison with control period, 1971–2000. Based on climate projections, examination of future impacts on sectors is also carried out. Selected uncertainty issues relevant to observations, understanding and projections are tackled as well.     

Lu-Hf and PbSL geochronology of apatites from Proterozoic terranes: A first look at Lu-Hf isotopic closure in metamorphic apatite

The mineral apatite is characterized by elevated and highly variable Lu/Hf ratios that, in some cases, allow for single-crystal dating by the Lu-Hf isotopic system. Apatites from the Adirondack Lowlands and Otter Lake area in the Grenville Province, and from the Black Hills, South Dakota, yield Lu-Hf ages that are consistently older than their respective Pb step leaching ages. Isotopic closure for the Lu-Hf system, therefore, occurs before U-Pb system closure in this mineral. In the Adirondack Lowlands, where H₂O activity was low, Lu-Hf systematics of cm-sized apatite crystals remained undisturbed during upper amphibolite facies metamorphism (∼700 to 675 °C) at 1170-1130 Ma. The relatively old Lu-Hf ages of 1270 and 1230 Ma observed for these apatites correlate with decreasing crystal size. In contrast, apatite from the fluid-rich Otter Lake area and Black Hills yields unrealistically low apparent Lu-Hf closure temperatures, implying that in these apatites, fluids facilitated late exchange. The Lu-Hf ages for the metamorphic apatites were thus controlled either by the prevailing temperature and grain size, or by fluid activity.     

Provenance ages and alteration histories of shales from the Middle Archean Buhwa greenstone belt, Zimbabwe: Nd and Pb isotopic evidence

Shales of the ca. 3.0 Ga Buhwa Greenstone Belt, Zimbabwe, were derived from a compositionally diverse provenance whose ages, determined by ion probe analyses of detrital zircons in interbedded sandstones, range from 3.8 to 3.1 Ga. Geochemical data for the shales were previously interpreted to indicate that sediments had been derived from an intensely weathered source. REE concentrations in the shales were interpreted to suggest that the provenance was compositionally mixed, with components of felsic (tonalite and alkalic granitoid) and mafic rocks. Sm/Nd and Nd isotopic compositions of these rocks can be used to model initial Nd isotopic ratios at the time of sedimentation (ε_Ndsed), as well as model crustal formation ages (T_DM). The former, at the age of sedimentation, range from +0.6 to −10.8, consistent with a range of provenance ages. The latter range from 4.46 Ga to 2.99 Ga. The oldest crustal formation ages, up to 0.7 Ga older than known detrital components, are interpreted here to indicate that the Sm-Nd system of the sediments experienced open system behavior. The implied alteration would have included an increase in Sm/Nd by about 20-25 percent, probably in the form of preferential loss of Nd with respect to Sm. The Pb isotopic compositions of whole rock samples are quite radiogenic, with a range of ²⁰⁶Pb/²⁰⁴Pb from 25.5 to 154. An array of ten samples lies scattered about a line with a ²⁰⁷Pb/²⁰⁴Pb -²⁰⁶Pb/²⁰⁴Pb slope age of about 2.73 Ga. Five individual samples were sequentially leached to further test the timing and characteristics of this U-Th-Pb alteration event. These arrays of a whole rock, three leach steps, and a residue also form linear Pb-Pb arrays (one is more scattered) with ages ranging from 2260 ± 360 Ma to 2824 ± 170 Ma, suggesting that all samples experienced a latest Archean to earliest Proterozoic enrichment in U/Pb. This age range also may be the approximate age of Sm/Nd enrichment for the shales. All samples, both whole rocks and leached samples, lie grouped on a ²⁰⁸Pb/²⁰⁴Pb - ²⁰⁶Pb/²⁰⁴Pb diagram around a line with ²³²Th/²³⁸U = 3.5 (2.9 to 3.9). Because of the lack of large differences in the Th/U of the samples through large ranges of U/Pb, we interpret this consistency in Th/U to mean that the shales of the Buhwa belt experienced Pb loss, rather than U and Th gain. Circumstances that may be responsible for Pb loss in a sedimentary basin include loss of saline fluids during basin dewatering. Such an event would likely have been related to folding associated with the thrusting and magmatic intrusion of the adjacent Limpopo Belt, suggesting that uplift, dewatering, and geochemical and isotopic alteration can be genetically related.     

Past and future climate variations in the Norwegian Arctic: overview and novel analyses

Sparse stations and serious measuring problems hamper analyses of climatic conditions in the Arctic. This paper presents a discussion of measuring problems in the Arctic and gives an overview of observed past and projected future climate variations in Svalbard and Jan Mayen. Novel analyses of temperature conditions during precipitation and trends in fractions of solid/liquid precipitation at the Arctic weather stations are also outlined. Analyses based on combined and homogenized series from the regular weather stations in the region indicate that the measured annual precipitation has increased by more than 2.5% per decade since the measurements started in the beginning of the 20th century. The annual temperature has increased in Svalbard and Jan Mayen during the latest decades, but the present level is still lower than in the 1930s. Downscaled scenarios for Svalbard Airport indicate a further increase in temperature and precipitation. Analyses based on observations of precipitation types at the regular weather stations demonstrate that the annual fraction of solid precipitation has decreased at all stations during the latest decades. The reduced fraction of solid precipitation implies that the undercatch of the precipitation gauges is reduced. Consequently, part of the observed increase in the annual precipitation is fictitious and is due to a larger part of the "true" precipitation being caught by the gauges. With continued warming in the region, this virtual increase will be measured in addition to an eventual real increase.     

Seawater intrusion and fresh groundwater hydraulics in fjord delta aquifers inferred from ground penetrating radar and resistivity profiles—Sunndalsøra and Esebotn, western Norway

Geophysical surveys have been carried out in two fjord delta aquifers in western Norway. Geophysical methods comprised ground penetrating radar (GPR), shallow reflection seismic and resistivity measurements. The purpose of the investigations was to evaluate hydrogeological properties of the fjord delta aquifers with emphasis on the possibilities of abstracting saline groundwater for use in fish farming. At Sunndalsøra, reflection seismic was helpful in the mapping of the base of the aquifer. Resistivity profiles revealed both the spatial and seasonal variability of seawater intrusion. Penetration depths of ground penetrating radar (GPR-D) revealed the spatial variation of the boundary of the transition zone between saline and fresh groundwater. Maps of GPR-D can be used to indicate direction and magnitude of mean hydraulic gradients and thus to locate optimal sites for both fresh and saline groundwater abstraction.In fjord delta aquifers, both rivers and abandoned river channels constitute important groundwater divides. Optimal locations for saline groundwater abstraction wells are in areas separated from the rivers by abandoned river channels. In areas between the rivers and the abandoned river channels, groundwater abstraction will result in decreasing salinity of the water.     

Seismic refraction and reflection measurements in the southern Barents Sea

Seismic refraction and continuous reflection measurements were made in the southern Barents Sea. On the basis of these investigations and earlier data from the area, the total thickness of sediments and thickness of the semiconsolidated section have been mapped. The main part of the investigated area consists of Mesozoic and Paleozoic sediments, while the areas near the shelf edge show a westward increasing wedge of Cenozoic deposits above the same sediments found to the east. Along the Norwegian coast and in the areas southwest of Bjørnøya a rapid increase of sediments is noted, while a much more gentle westward growth is found in the main part of the Barents shelf. The data suggest the southern flank of Bjørnøyrenna is an area of structural deformation. Structures that can be associated with salt diapirs are recorded in a limited area on Tromsøflaket.