a review of postglacial emergence on svalbard franz josef land and novaya zemlya northern eurasia the pattern of postglacial emergence in the barents sea is pivotal to constraining the timing of deglaciation and extent and thickness of the last ice sheet in northern eurasia this review unites records of holocene relative sea level from svalbard franz josef land and novaya zemlya to better understand the geometries of past ice sheet loads emergence data from northern eurasia confine the maximum area of glacier loading to the northwestern barents sea where 100 m of emergence is measured on kongs ya deglacial unloading commenced on western and northern spitsbergen c 13 12 14 c ka ago and by c 10 5 14 ck a on eastern svalbard and more distal sites on franz josef land and novaya zemlya the marine limit phase c 13 12 14 c ka on western and northern spitsbergen is characterized by the construction of spits indicating a dominance of long shore drift over stormgenerated fetch reflecting extensive sea ice coverage of coastal areas at sites in proximity to the ice sheet margin on western and northern spitsbergen there is evidence for a transgressive regressive cycle c 6 4 14 c ka possibly reflecting back migration of displaced mantle material a modern transgression is inferred from the marine erosion of 17th century cultural features and 14 c ages of whalebone and terrestrial peat buried by modern storm gravels that place sea level at its present position by c 2 to 1 ka ago the greatest observed emergence on franz josef land occurs on bell island with a marine limit at 49 m aht formed c 10 14 c ka available emergence data since 9 ka show rising strandlines toward the southwest at b0 3 m km the northern limit of emergence on franz josef land is poorly constrained because relative sea level data is sparse north of 80 30 0 n in contrast to svalbard and franz josef land the marine limit on northern novaya zemlya is only 10 15 m above high tide and formed between 6 5 and 5 0 14 c ka when global sea level was stabilizing all sites show little apparent emergence during the past 2 ka with the youngest raised landforms at identical heights to storm beaches this minimal glacio isostatic signature on novaya zemlya and on vaygach island where deglaciation commenced 10 ka ago indicates ice sheet thicknesses of o1 5 km the spatial variation in emergence for the barents sea indicates that western and northern spitsbergen and novaya zemlya were near the reactive margin of the ice sheet and these areas sustained the briefest ice coverage 2 6 ka and were probably not in isostatic equilibrium in contrast central and eastern svalbard and southern franz josef land were beneath a substantial ice load and probably sustained this load for c 10 14 c ka and achieved isostatic equilibrium isostasy residual from an ice sheet model portrays well the general pattern of uplift and load response at the centre of ice sheets but deviates substantial at the ice sheet margin or areas covered by thin ice like novaya zemlya

on the potential for a bottom active layer below coastal permafrost the impact of seawater on permafrost degradation imaged by electrical resistivity tomography hornsund sw spitsbergen this paper presents the results of two dimensional electrical resistivity tomography ert of permafrost developed in coastal zone of hornsund sw spitsbergen the measurements were made using the wenner schlumberger electrode array with an electrode spacing 5 m for overview and 1 5 or 1 m spacing for detailed imaging using the ert inversion results we studied the sea influence on deeper parts of the frozen ground during the investigations we tested hypotheses that the operation of seawater on shoreface may cause changes in the shape of the coastal permafrost base and that the impact of seawater on more inland permafrost depends on the shape of the shoreline differently in the embayment and differently in a headland exposed to the open sea our study was inspired by previous ground temperature measurements conducted in several boreholes located in study area which captured the propagation of ground heat waves from the base of permafrost our resistivity models indicate a major differentiation in terms of resistivity of permafrost in the coastal zone the resistivity measures obtained in deeper layers of ground were so low 100 m that in the warm permafrost conditions they exclude a possibility of freezing the coastal sediments and bedrock from the side of the sea low values continue further inland going down under the surface layer of permafrost with higher resistivity we interpret this situation as an influence of seawater s temperature and salinity on deeper parts of permafrost based on the measurements conducted within two years we stated a change in the distribution of resistivity both in the active layer and in coastal front of permafrost in deeper parts of the ground as observed in the inverse models the geometric arrangement between the fields of extreme resistivity indicates the existence of a bottom active layer by the permafrost base depending on thermal and chemical characteristics of seawater the measurements conducted in the embayment as well as on the headland exposed to the operation of storm waves proved strong differences in the scale of the impact of seawater on permafrost

postglacial emergence of southernmost spitsbergen svalbard supplement to article by forman et al 2004 qsr 23 1391 1434

from mountain top to the deep sea deglaciation in 4d of the northwestern barents sea ice sheet abstract the timing of the deglaciation of the northern barents sea ice sheet bsis documented in terrestrial and offshore records from the svalbard archipelago is reviewed we present new cosmogenic nuclide cn ages from formerly unexplored inland areas of northern svalbard to investigate the timing of thinning of past local ice domes cn data are compared with radiocarbon ages from marine and terrestrial deposits 10be isotope cn dates on erratic boulders from interior svalbard suggest that glacier surfaces in northern and western svalbard thinned 950 650 m from 26 4 ka and continued over an extended period until 16 ka initial ice retreat from the western outer to the inner shelf began at 20 5 ka and in storfjordrenna southwest of svalbard around 19 18 ka retreat of grounded ice from the northern outer to the inner shelf did not begin before 15 9 ka we therefore suggest increasing summer insolation and aridification due to atmospheric circulation changes and perennial sea ice cover as the main mechanisms for the ice thinning and grounded ice retreat from the outer shelves before and during the heinrich 1 event the frontal position of the grounded ice sheet however did not change during several millennia despite further thinning in interior northern svalbard the inner shelf areas rapidly deglaciated towards the fjord mouths along the western coasts between 15 and 14 ka and became ice free before and during meltwater pulse 1a mwp 1a the collapse of the ice shelves from the inner shelf towards the fjord mouths and inner fjords occurred on a decadal to centennial time scale based on overlapping radiocarbon ages from marine sediment cores in addition to cn data from erratic boulders in lowlands we suggest that additional mechanisms must have caused this rapid collapse together with reduced moisture supply in the accumulation areas we assume that subsurface warm atlantic water masses that reached the western shelf after 17 5 ka may have accelerated debuttressing of the ice shelves in addition to the bolling warming that kicked in around 15 1 ka due to increased insolation and the global sea level rise called mwp 1a conservative calculations estimate the contribution of only the northwestern part of the bsis to sea level rise with 0 0004 cm yr 1 between 26 and 16 ka and 0 02 cm yr 1 in assumed 300 years between 15 and 14 ka

geoelectric observations of the degradation of nearshore submarine permafrost at barrow alaskan beaufort sea 1 submarine permafrost degradation rates may be determined by a number of interacting processes including rates of sea level rise and coastal erosion sea bottom temperature and salinity regimes geothermal heat flux and heat and mass diffusion within the sediment column observations of ice bearing permafrost in shelf sediments are necessary in order to determine its spatial distribution and to quantify its degradation rate we tested the use of direct current electrical resistivity to ice bearing permafrost in elson lagoon northeast of barrow alaska beaufort sea a sharp increase in electrical resistivity was observed in profiles collected perpendicular to and along the coastline and is interpreted to be the boundary between ice free sediment and underlying ice bearing submarine permafrost the depth to the interpreted ice bearing permafrost increases from 2 m below sea level to over 12 m below sea level with increasing distance from the coastline the dependence of the saline sediment electrical resistivity on temperature and freezing was measured in the laboratory to provide validation for the field measurements electrical resistivity was shown to be effective for detection of shallow ice bearing permafrost in the coastal zone historical coastal retreat rates were combined with the inclination of the top of the ice bearing permafrost to calculate mean vertical permafrost degradation rates of 1 to 4 cm yr 1

three dimensional nonlinear analyses of a metro tunnel in sao paulo porous clay brazil tropical residual clays with a highly porous structure react to the stress changes induced by tunneling in such a way that surface settlements can be larger than crown level settlements along a tunnel axis this behavior which is not readily simulated by most numerical analyses was also observed in the paraiso tunnel built for the sao paulo metro brazil this is a shallow tunnel driven through porous clayey soils by the sequential method detailed results of field monitoring are presented and discussed 3d finite element analyses that allowed a detailed simulation of the construction sequence have been carried out considering two distinct constitutive models for the soil a simple elastic perfectly plastic mohr coulomb model and the elastoplastic model developed by lade the results of these analyses are compared with the observed behavior as well as with the results from a plane strain finite element analysis it is shown that only the 3d finite element analysis coupled with the more sophisticated soil constitutive model provides a full reproduction of field performance with particular relevance for the deformations in the soil mass over the tunnel

paleoclimatic inferences from glacial fluctuations on svalbard during the last 20 000 years the climate history of western spitsbergen svalbard is deduced from variations of glaciers during the last 20 000 years a major depression of the regional equilibrium line altitude ela occurred during the late weichselian glacial maximum 18000 13000y ago when low summer temperatures may have caused year round snow accumulation on the ground this rapid expansion of the glaciers also indicates nearby moisture sources suggesting partly open conditions in the norwegian sea during the summers a rapid glacial retreat around 13 000 12 500 y bp was caused by a sudden warming during the younger dryas the ela along the extreme western coast of spitsbergen was not significantly lower than at present in contrast to fennoscandia the british isles and the alps there is no evidence for readvance of local glaciers during younger dryas on western spitsbergen this difference is attributed to a much dryer climate on spitsbergen and probably only slight changes in sea surface temperatures in addition summer melting in this high arctic area is more sensitive to orbitally increased insolation around 10 000 y bp another rapid warming occurred and during early and mid holocene the summer temperatures were significantly higher than at present a temperature decline during the late holocene caused regrowth of the glaciers which reached their maximum holocene position during the last century

observed long term differential settlement of metro structures built on soft deposits in the yangtze river delta region of china in this study the measured differential settlements of five metro lines built on soft deposits were analyzed the different structural combinations at various characteristic locations in the metro

middepth circulation of the eastern tropical south pacific and its link to the oxygen minimum zone there is an incomplete description of the mid depth circulation and its link to the oxygen minimum zone omz in the eastern tropical south pacific subsurface currents of the omz in the eastern tropical south pacific are investigated with a focus at 400 m depth close to the core of the omz using several acoustic doppler current profiler sections recorded in january and february 2009 five profiling floats with oxygen sensors were deployed along 85 50 w in february 2009 with a drift depth at 400 m their spreading paths are compared with the model flow field from a 1 10 tropical pacific model tropac01 and the simple ocean data assimilation soda model overall the mean currents in the eastern tropical south pacific are weak so that eddy variability influences the flow and ultimately feed oxygen poor water to the omz the center of the omz is a stagnant area so that floats stay much longer in this region and can even reverse direction in one case of one float deployed at 8 s returned to the same location after 15 month on the northern side of the omz in the equatorial current system floats move rapidly to the west most current bands reported for the near surface layer exist also in the depth range of the omz a schematic circulation flow field for the omz core depth is derived which shows the northern part of the south pacific subtropical gyre south of the omz and the complicated zonal equatorial flow field north of the omz

application of field geophysics in geomorphology advances and limitations exemplified by case studies abstract during the last decade the use of geophysical techniques has become popular in many geomorphological studies however the correct handling of geophysical instruments and the subsequent processing of the data they yield are difficult tasks furthermore the description and interpretation of geomorphological settings to which they apply can significantly influence the data gathering and subsequent modelling procedure e g achieving a maximum depth of 30 m requires a certain profile length and geophone spacing or a particular frequency of antenna for more than three decades geophysical techniques have been successfully applied for example in permafrost studies however in many cases complex or more heterogeneous subsurface structures could not be adequately interpreted due to limited computer facilities and time consuming calculations as a result of recent technical improvements geophysical techniques have been applied to a wider spectrum of geomorphological and geological settings this paper aims to present some examples of geomorphological studies that demonstrate the powerful integration of geophysical techniques and highlight some of the limitations of these techniques a focus has been given to the three most frequently used techniques in geomorphology to date namely ground penetrating radar seismic refraction and dc resistivity promising applications are reported for a broad range of landforms and environments such as talus slopes block fields landslides complex valley fill deposits karst and loess covered landforms a qualitative assessment highlights suitable landforms and environments the techniques can help to answer yet unsolved questions in geomorphological research regarding for example sediment thickness and internal structures however based on case studies it can be shown that the use of a single geophysical technique or a single interpretation tool is not recommended for many geomorphological surface and subsurface conditions as this may lead to significant errors in interpretation because of changing physical properties of the subsurface material e g sediment water content in many cases only a combination of two or sometimes even three geophysical methods gives sufficient insight to avoid serious misinterpretation a good practice guide has been framed that provides recommendations to enable the successful application of three important geophysical methods in geomorphology and to help users avoid making serious mistakes

the last glacial maximum of svalbard and the barents sea area ice sheet extent and configuration abstract the timing extent and configuration of the late weichselian barents ice sheet has been debated for several decades this debate has arisen largely because of the limited or conflicting field evidence on which most models have been based in particular reconstruction of the marine parts of the former barents ice sheet has been controversial this paper aims to review the geological observations and interpretations regarding the size and timing of the late weichselian ice sheet combined with numerical modelling of its formation in order to produce a reconstruction of ice sheet extent and behaviour sub glacial till with overlying glacimarine deposits dated to the late weichselian is found over most of the barents sea floor and the continental shelf west of svalbard glacially induced debris flow deposits on the large bjonoya and isfjorden trough mouth fans strongly support the idea of ice sheet extension to the shelf edge during maximum glaciation isobase maps show a centre of post glacial uplift in the north central barents sea and glaciological and isostatic modelling suggest that the ice sheet was 2000 3000 m thick in this area the ice sheet was confluent with ice over the kara sea but the interaction between the barents and kara ice sheets is not yet fully understood the deglaciation of the barents ice sheet started ca 15 ka probably by calving within the deeper troughs by 12 ka most of the central barents sea was ice free and ice remained over the svalbard franz josef land and novaja zemlya archipelagos and adjacent shallow shelf areas the coasts and fjords of these islands were ice free by 10 ka

tunneling in squeezing rock the bolu tunnel anatolian motorway turkey abstract the bolu tunnel is subject to considerable deformation due to stress related failure in the rock mass in thrust zones and strike slip faults that transect the tunnel these deformations resulted in some serious geotechnical problems which were overcome either by flexible or extremely heavy support systems the heavy system was used to prevent or bring under control the large deformations that would take place during excavation whereas the flexible method allows the deformations to develop without restraint the heavy support system was used in thrust fault zones and in flysch zones in the bolu tunnel and produced more successful results in comparison to the flexible support system a brief explanation of the tunnel collapse in the duzce earthquake is also provided

anisotropy and crystalline fabric of whillans ice stream west antarctica inferred from multicomponent seismic data crystal orientation fabric cof describes the intrinsic anisotropic nature of ice and is an important parameter for modeling glacier flow we present the results of three component active source seismic observations from the whillans ice stream wis a fast flowing ice stream in west antarctica surface wave dispersion analysis ray tracing and traveltime inversion of compressional p and shear s waves reveal the presence of transversely isotropic ice with a vertical axis of symmetry vti beneath approximately 65 m of isotropic firn the ice stream is characterized by weak anisotropy involving an average ice thickness of approximately 780 m the analysis indicates that about 95 of the ice mass is anisotropic and the crystalline c axes span within an average broad cone angle of 73 10 with respect to the vertical axis moreover the mean temperature t below the firn estimated from seismic data is 15 5 c these data do not show evidence of englacial seismic reflectivity which indicates the lack of abrupt changes in the cof the presence of azimuthal anisotropy due to transversely compressive flow or fractures aligned along a preferential direction is also excluded we suggest that the observed vti ice structure is typical of large ice streams in regions where basal sliding and bed deformation dominate over internal glacial deformation

full wavefield inversion of surface waves for mapping embedded low velocity zones in permafrost abstractsurface waves are advantageous for mapping seismic structures of permafrost in which irregular velocity gradients are common and thus the effectiveness of refraction methods are limited nevertheless the complex velocity structures that are common in permafrost environments often yield unusual dispersion spectra in which higher order and leaky modes are dominant such unusual dispersion spectra were prevalent in the multichannel surface wave data acquired from our permafrost study site at barrow alaska owing to the difficulties in picking and identifying dispersion curves from these dispersion spectra conventional surface wave inversion methods become problematic to apply to overcome these difficulties we adopted a full wavefield method to invert for velocity models that can best fit the dispersion spectra instead of the dispersion curves the inferred velocity models were consistent with collocated electric resistivity results and with subsequent confirmation cores which indicated the re

estimating depth of investigation in dc resistivity and ip surveys in this paper the term depth of investigation refers generically to the depth below which surface data are insensitive to the value of the physical property of the earth estimates of this depth for dc resistivity and induced polarization ip surveys are essential when interpreting models obtained from any inversion because structure beneath that depth should not be interpreted geologically we advocate carrying out a limited exploration of model space to generate a few models that have minimum structure and that differ substantially from the final model used for interpretation visual assessment of these models often provides answers about existence of deeper structures differences between the models can be quantified into a depth of investigation doi index that can be displayed with the model used for interpretation an explicit algorithm for evaluating the doi is presented the doi curves are somewhat dependent upon the parameters used to generate the different models but the results are robust

surface wave analysis for identifying unfrozen zones in subglacial sediments abstractto reveal the extent of freezing in subglacial sediments we estimated s wave velocity along a glacier using surface wave analysis because the s wave velocity varies significantly with the degree of freezing of the pore fluid in the sediments this information is useful for identifying unfrozen zones within subglacial sediments which again is important for glacier dynamics we used active source multichannel seismic data originally acquired for reflection analysis along a glacier at spitsbergen in the norwegian arctic and proposed an effective approach of multichannel analysis of surface waves masw in a glacier environment common midpoint crosscorrelation gathers were used for the masw to improve lateral resolution because the glacier bed has a rough topology we used multimode analysis with a genetic algorithm inversion to estimate the s wave velocity due to the potential existence of a low velocity layer beneath the glacier ice and the observation of higher modes in the dispersion curves i

temperature and precipitation history of the arctic as the planet cooled from peak warmth in the early cenozoic extensive northern hemisphere ice sheets developed by 2 6 ma ago leading to changes in the circulation of both the atmosphere and oceans from not vert similar2 6 to not vert similar1 0 ma ago ice sheets came and went about every 41 ka in pace with cycles in the tilt of earth s axis but for the past 700 ka glacial cycles have been longer lasting not vert similar100 ka separated by brief warm interglaciations when sea level and ice volumes were close to present the cause of the shift from 41 ka to 100 ka glacial cycles is still debated during the penultimate interglaciation not vert similar130 to not vert similar120 ka ago solar energy in summer in the arctic was greater than at any time subsequently as a consequence arctic summers were not vert similar5 c warmer than at present and almost all glaciers melted completely except for the greenland ice sheet and even it was reduced in size substantially from its present extent with the loss of land ice sea level was about 5 m higher than present with the extra melt coming from both greenland and antarctica as well as small glaciers the last glacial maximum lgm peaked not vert similar21 ka ago when mean annual temperatures over parts of the arctic were as much as 20 c lower than at present ice recession was well underway 16 ka ago and most of the northern hemisphere ice sheets had melted by 6 ka ago solar energy reached a summer maximum 9 higher than at present not vert similar11 ka ago and has been decreasing since then primarily in response to the precession of the equinoxes the extra energy elevated early holocene summer temperatures throughout the arctic 1 3 c above 20th century averages enough to completely melt many small glaciers throughout the arctic although the greenland ice sheet was only slightly smaller than at present early holocene summer sea ice limits were substantially smaller than their 20th century average and the flow of atlantic water into the arctic ocean was substantially greater as summer solar energy decreased in the second half of the holocene glaciers re established or advanced sea ice expanded and the flow of warm atlantic water into the arctic ocean diminished late holocene cooling reached its nadir during the little ice age about 1250 1850 ad when sun blocking volcanic eruptions and perhaps other causes added to the orbital cooling allowing most arctic glaciers to reach their maximum holocene extent during the warming of the past century glaciers have receded throughout the arctic terrestrial ecosystems have advanced northward and perennial arctic ocean sea ice has diminished here we review the proxies that allow reconstruction of quaternary climates and the feedbacks that amplify climate change across the arctic we provide an overview of the evolution of climate from the hot house of the early cenozoic through its transition to the ice house of the quaternary with special emphasis on the anomalous warmth of the middle pliocene early quaternary warm times the mid pleistocene transition warm interglaciations of marine isotope stages 11 5e and 1 the stage 3 interstadial and the peak cold of the last glacial maximum

spatial distribution and controls of permafrost development in non glacial arctic catchment over the holocene fuglebekken sw spitsbergen abstract this article presents the distribution and properties of the permafrost based on electrical resistivity tomography ert and multichannel analysis of surface waves masw data collected at the fuglebekken coastal catchment area in sw spitsbergen this work summarizes the development of permafrost in this area during the holocene from the mountain environment through to the system of elevated marine terraces found around the coast the ert models were analysed taking into consideration the non unique nature of the data inversion process and the physical limitations of this method comparing the ert and the masw results allows a zonal characterization of the occurring ice bearing permafrost and its correlation with the evolution history of the catchment area maritime transgression as well as intensive watercourses during past degradation episodes have altered the permafrost presence and ice accumulating abilities of different sediment zones permafrost development depends greatly on the presence of surface watercourses in talus slopes the youngest elevated uplifted marine terrace did not develop an ice rich permafrost but the presence of permafrost in a cryotic form is possible the significant range of the fjord water infiltration found within the sedimentary cover have influenced the development of the coastal permafrost the current structure of ice bearing permafrost found in the research area seems to be very sensitive to the climatic changes based on these results we propose a model for the formation of the current permafrost in the studied area