stacking paleointensity and oxygen isotope data for the last 1 5 myr piso 1500 coupled relative geomagnetic paleointensity rpi and oxygen isotope records are used to construct rpi and oxygen isotope stacks for the last 1 5 myr the coupled correlations are accomplished using the match algorithm lisiecki l e and lisiecki p a 2002 application of dynamic programming to the correlation of paleoclimate records paleoceanography 17 1049 doi 10 1029 2001pa000733 to simultaneously correlate isotope and rpi records the simultaneous match reduces the degree of freedom associated with correlations using rpi or oxygen isotope records alone the overall compatibility of rpi and oxygen isotopes indicates a dominant global but independent component in both signals the local wavelet power spectrum lwps for the rpi stack indicates little significant orbital power although the accompanying oxygen isotope stack has all the lwps characteristics expected of a high resolution oxygen isotope record containing orbital frequencies the piso 1500 stack represents a new stratigraphic template that can be used to correlate among marine sediment records and link them to polar ice cores via variations in cosmogenic nuclide production scaling the stack to values for virtual axial dipole moment vadm indicate maxima at 15 1022 am2 and minima that imply a threshold of 2 5 1022 am2 below which values are associated with either polarity reversals or magnetic excursions

why are geomagnetic excursions not always recorded in sediments constraints from post depositional remanent magnetization lock in modelling abstract many geomagnetic excursions have been documented during the brunhes chron however high resolution paleomagnetic studies of sediments often provide evidence of few if any excursions we have investigated the reasons for this observation by modelling the post depositional remanent magnetization pdrm lock in process a cubic lock in function produces more rapid lock in compared to linear and exponential functions proposed in the literature we therefore used a cubic function to model best case scenarios for the quality of the paleomagnetic record when a high frequency geomagnetic input signal is convolved with the sediment lock in function for a wide range of sedimentation rates even for a lock in depth of 10 cm where 95 of the pdrm is locked in 5 cm below the surface mixed layer an input signal containing abundant excursions with 1 kyr duration is smoothed so drastically at low sedimentation rates 1 3 cm kyr that no excursions are recorded excursions are further attenuated by increasing the lock in depth as well as by sampling at discrete stratigraphic intervals the pdrm process acts as a low pass filter for high frequency secular variation signals even at moderate sedimentation rates 10 cm kyr we have also modelled the effects of modulation of sedimentation rate by a climatic forcing function e g insolation even though the average sedimentation rate might be substantial pdrm recording becomes much less reliable in intervals where sedimentation rates are lowest in these cases some excursions are reliably recorded in detail while others may not be recorded at all our modelling suggests that in order to consistently detect the presence of geomagnetic excursions it is ideal to work with sediments that maintain minimum sedimentation rates above 10 cm kyr if the normal spectrum of geomagnetic field behaviour contains abundant excursions failure to document excursions in many apparently high resolution analyses probably results from pdrm lock in within relatively slowly deposited sediments or to unrecognized intervals of slow sedimentation in environments with higher average sedimentation rates

orbital modulation of the earth s magnetic field intensity more than 20 years ago on the basis of data from a pacific sediment core it was suggested that geomagnetic field intensity may vary with the earth s orbital obliquity centred on a period of 41 kyr as a result of the effect of obliquity on precessional forces in the earth s core1 it had also been proposed that precession plays an important role in the energy budget of the earth s geodynamo2 but subsequent analyses indicated that the energy available from precession is at least an order of magnitude less than that required to drive the geodynamo3 here however we report a spectral analysis of sedimentary records of relative geomagnetic palaeointensity from two north atlantic sites which shows significant power both at orbital eccentricity 100 kyr and obliquity 41 kyr the eccentricity power is also present in bulk magnetic properties such as susceptibility and is therefore attributable to lithological variations controlled by eccentricity driven climate change the obliquity power however is not apparent in bulk magnetic properties and seems to be a property of the geomagnetic field itself thus providing evidence for the orbital forcing of geomagnetic field intensity

post depositional remanent magnetization lock in for marine sediments deduced from 10 be and paleomagnetic records through the matuyama brunhes boundary abstract geomagnetic field intensity records from marine sediments have contributed to improved understanding of variations in the earth s magnetic field and have helped to establish age models for marine sediments however lock in of the geomagnetic signal below the sediment water interface in marine sediments through acquisition of a post depositional remanent magnetization pdrm adds uncertainty to synchronization of marine sedimentary records although quantitative models enable assessment of delays in remanence acquisition associated with pdrm processes the nature of the filter function and the pdrm lock in zone thickness remain topics of debate we performed both forward numerical simulations and inverse parameter estimation to assess the best fit filter function and pdrm lock in zone thickness in marine sediments based on a comparison of 10be flux and relative paleointensity records our simulations reveal that the rate of pdrm lock in increases in the middle of the lock in zone and that a gaussian function with a 17 cm lock in zone thickness provides a good approximation to the pdrm lock in within the studied core with this function pdrm lock in is delayed but with relatively little distortion of the geomagnetic signal our results also imply that a pdrm is not simply locked due to progressive marine sediment consolidation and dewatering and that the arbitrary functions linear cubic and exponential that are often used to model pdrm lock in starting from the base of the surface mixed layer cannot explain fully the observed paleomagnetic signal

a distributed temperature index ice and snowmelt model including potential direct solar radiation hourly melt and discharge of storglaciaren a small glacier in sweden were computed for two melt seasons applying temperature index methods to a 30 m resolution grid for the melt component the classical degree day method yielded a good simulation of the seasonal patient of discharge but the pronounced melt induced daily discharge cycles were not captured modelled degree day factors calculated for every hour and each gridcell from melt obtained from a distributed energy balance model varied substantially both diurnally and spatially a new distributed temperature index model is suggested attempting to capture both the pronounced diurnal melt cycles and the spatial variations in melt due to the effects of surrounding topography this is accomplished by including a radiation index in terms of potential clear sky direct solar radiation and thus without the need for other data besides air temperature this approach improved considerably the simulation of diurnal discharge fluctuations and yielded a more realistic spatial distribution of melt rates the incorporation of measured global radiation to account for the reduction in direct solar radiation due to cloudiness did not lead to additional improvement in model performance

geomagnetic field variations during the last 400 kyr in the western equatorial pacific paleointensity inclination correlation revisited 1 a paleomagnetic study was conducted on four piston cores newly obtained from the west caroline basin in the western equatorial pacific in order to investigate variations in paleointensity and inclination during the last 400 kyr an inclination intensity correlation was previously reported in this region using giant piston cores but the quality of the paleomagnetic data of the younger end the last ca 300 kyr was needed to be checked because the upper part of the giant piston cores could suffer from perturbation by oversampling age control is based on the oxygen isotope ratios for one core and inter core correlation using relative paleointensity for other cores stacked curves of paleointensity and inclination were constructed from the four cores it was confirmed that variations on the order of 104 to 105 years occur in inclination as well as paleointensity a cross correlation analysis showed that significant in phase correlation occurs between intensity and inclination for periods longer than about 25 kyr and power spectra of both paleointensity and inclination variations have peaks at 100 kyr periods the regional paleointensity stack with higher resolution than the sint 800 stack guyodo and valet 1999 should be useful for paleointensity assisted chronostratigraphy

geomagnetic dipole strength and reversal rate over the past two million years independent records of relative magnetic palaeointensity from sediment cores in different areas of the world can be stacked together to extract the evolution of the geomagnetic dipole moment1 2 and thus provide information regarding the processes governing the geodynamo so far this procedure has been limited to the past 800 000 years 800 kyr ref 3 which does not include any geomagnetic reversals here we present a composite curve that shows the evolution of the dipole moment during the past two million years this reconstruction is in good agreement with the absolute dipole moments derived from volcanic lavas which were used for calibration we show that at least during this period the time averaged field was higher during periods without reversals but the amplitude of the short term oscillations remained the same as a consequence few intervals of very low intensity and thus fewer instabilities are expected during periods with a strong average dipole moment whereas more excursions and reversals are expected during periods of weak field intensity we also observe that the axial dipole begins to decay 60 80 kyr before reversals but rebuilds itself in the opposite direction in only a few thousand years

sedimentary records of relative paleointensity of the geomagnetic field theory and practice sediments have proved irresistible targets for attempts at determining the relative variations in the earth s magnetic field because of the possibility of long and continuous sequences that are well dated and have a reasonable global distribution the assumption underlying paleointensity studies using sedimentary sequences is that sediments retain a record reflecting the strength of the magnetic field when they were deposited early theoretical work suggested that because the time required for an assemblage of magnetic particles in water to come into equilibrium with the ambient magnetic field was quite short no dependence on magnetic field was expected nonetheless a number of experiments showed that sedimentary magnetizations varied in accordance with the field albeit not always in a simple linear fashion experiments in which the sediments were stirred in the presence of a field to simulate bioturbation showed a reasonably linear relationship with the applied field and these results spurred the hope that variations in the earth s magnetic field might indeed be recoverable from appropriate sedimentary sequences examination of existing paleointensity data sets allows a few general conclusions to be drawn it appears that sedimentary sequences can and do provide a great deal of information about the variations in relative paleointensity of the earth s magnetic field the dynamic range of sedimentary data sets is comparable to those acquired from thermal remanences moreover when compared directly with such independent measures of magnetic field variations as beryllium isotopic ratios and thermally blocked remanences there is considerable agreement among the various records when viewed over timescales of hundreds to thousands of years relative paleointensity data sets from more than a few thousand kilometers apart bear little resemblance to one another suggesting that they are dominated by nondipole field behavior when viewed over timescales of a few tens of thousands to hundreds of thousands of years however the records show coherence over large distances at least thousands of kilometers and may reflect changes in the dipole field on the basis of a sequence spanning the brunhes and matuyama chrons the magnetic field has oscillated with a period of about 40 ka for the last few hundred thousand years but these oscillations are not clear in the record prior to about 300 ka thus they are probably not an inherent feature in the geomagnetic field and the correspondence of the period of oscillation to that of obliquity is probably coincidence

reductive diagenesis magnetite dissolution greigite growth and paleomagnetic smoothing in marine sediments a new view abstract in many anoxic sedimentary environments the onset of sulfate reduction and pyritization of detrital iron bearing minerals leads to a precipitous decline in magnetic mineral concentration during early diagenesis the usefulness of the surviving paleomagnetic record in such environments is usually argued to depend on how much of the primary detrital magnetic assemblage survives diagenetic dissolution detailed rock magnetic and electron microscope analyses of rapidly deposited 7 cm kyr latest pleistocene holocene sediments from the continental margins of oman 22 22 4 n 60 08 0 e and northern california 38 24 8 n 123 58 2 w demonstrate that pyritization during early diagenesis also leads to the progressive down core growth of the ferrimagnetic iron sulfide greigite greigite growth begins with nucleation of large concentrations of superparamagnetic sp nanoparticles at the inferred position of the sulfate methane transition which can explain the apparently paradoxical suggestion that diagenetically reduced sediments contain enhanced concentrations of sp particles looping of hysteresis parameters on a day plot records the dissolution of single domain sd titano magnetite and the formation of sp greigite which then slowly and progressively grows through its sd blocking volume and acquires a stable paleomagnetic signal this looping trend is also evident in data from several published records oregon margin korea strait japan sea niger fan argentine margin and the ontong java plateau indicating that these processes may be widespread in reducing environments our observations have profound implications for paleomagnetic records from sulfate reducing environments the paleomagnetic signal recorded by greigite is offset from the age of the surrounding sediments by 10 s of kyr and ongoing growth of greigite at depth results in smoothing of the recorded signal over intervals of 10 s to 100 s of kyr we therefore expect the presence of greigite to compromise paleomagnetic records in a wide range of settings that have undergone reductive diagenesis

palaeomagnetic study of iodp sites u1331 and u1332 in the equatorial pacific extending relative geomagnetic palaeointensity observations through the oligocene and into the eocene

glacier mass balance of norway 1961 2010 calculated by a temperature index model glacier mass balance in norway is only observed over a small portion 1 between 2000 and 2010 after four decades of zero to slightly positive annual mass balances

building the hindu kush monazite records of terrane accretion plutonism and the evolution of the himalaya karakoram tibet orogen in situ u th pb la icp ms monazite ages from the hindu kush of nw pakistan provide new petrochronologic constraints on the tectonic evolution of the himalaya karakoram tibet orogen monazites from two adjacent garnet staurolite schist specimens yield multiple age populations that record the major mesozoic and cenozoic deformational magmatic and metamorphic events along the southern margin of eurasia these include the accretion of the hindu kush sw pamir to eurasia during the late triassic followed by the accretion of the karakoram terrane in the early jurassic younger jurassic and cretaceous ages record the development of an andean style volcanic arc along the southern eurasian margin which ended with the docking of the kohistan island arc and the emplacement of the kohistan ladakh batholith during the late cretaceous the initial eocene collision of india with eurasia was followed by widespread high temperature metamorphism and anatexis associated with crustal thickening within the himalaya system in the late oligocene and early miocene

relative paleointensity stack during the last 250 kyr in the northwest pacific 1 we have conducted a paleomagnetic study of 10 sediment cores recovered from the northwest pacific the purpose is to establish a regional paleointensity stack during the last 250 kyrs nopapis 250 for global coverage of paleointensity data as well as a regional reference for paleointensity assisted stratigraphy in the studied cores reductive dissolution of magnetite appears to have occurred mainly in glacial periods such horizons accompany large decreases in s ratio s 0 3t 1 irm 0 3t sirm 2 as low as 0 90 the sediments are also intercalated by frequent volcanic ash layers prerequisites for reliable relative paleointensity estimation are not satisfied at these horizons we rejected unsuitable data by quantitative criteria based on s ratio and saturation isothermal remanent magnetization sirm and constructed the nopapis 250 curve from the remaining data in the construction of the curve we chose irm as a normalizer because acquisitions of anhysteretic remanent magnetization arm are considered to be influenced by magnetic interactions among magnetic grains in the northwest pacific sediments relative intensity variation of the nopapis 250 gives a standard deviation that is 33 of the average if the normal distribution is assumed the nopapis 250 curve generally shows similar variation patterns compared with other high resolution records reported from other regions many paleointensity lows are recognized in common six out of the nine lows can be correlated with reported excursions in literature

changes in detrital input ventilation and productivity in the central okhotsk sea during the marine isotope stage 5e penultimate interglacial period abstract by presenting benthic foraminifera isotope profiles and bulk geochemical composition of core sediments we offer a mutiproxy reconstruction of the central okhotsk sea oceanography between 130 to and 115 kyr related to the marine isotopic stage 5e mis 5e sediments from the site mr0604 pc7a have been compared with paleo sea surface temperatures and other records this multiparameter approach allowed to recognize three periods for mis 5e evolution characterized by variations in marine productivity and bottom oxygenation these variations have been ultimately associated with the production of okhotsk sea intermediate water and the presence or absence of nutrient contribution from the pacific deep water into central okhotsk sea aeolian input reconstructed by th sc ratio indicates higher values during the mis 6 and mis 5d compared with the mis 5e eu values indicate an input of detrital material from kurile islands and east kamchatka during the late mis 5e absent during the early mis 5e and glacial periods

geomagnetic excursions knowns and unknowns geomagnetic excursions are short lived episodes when earth s magnetic field deviates into an intermediate polarity state understanding the origin frequency amplitude duration and field behavior associated with excursions is a forefront research area within solid earth geophysics recent advances in excursion research are summarized here and key further research is suggested to resolve major unanswered questions improving the global distribution of excursion records particularly from the southern hemisphere obtaining high resolution sedimentary excursion records with good age control from sites with sedimentation rates 10 cm kyr obtaining volcanic excursion records coupled with high precision geochronology and estimating excursion duration with high chronological precision will all facilitate hypothesis testing concerning the deep earth dynamics that generate geomagnetic excursions

global changes in intensity of the earth s magnetic field during the past 800kyr recent advances in palaeomagnetic and dating techniques have led to increasingly precise records of the relative intensity of the earth s past magnetic field at numerous field sites the compilation and analysis of these records can provide important constraints on changes in global magnetic field intensity and therefore on the earth s geodynamo itself a previous compilation for the past 200 kyr integrated 17 marine records into a composite curve1 with the geomagnetic origin of the signal supported by an independent analysis of 10be production made on different cores2 the persistence of long term features in the earth s magnetic intensity or the existence of long term periodic changes cannot however be resolved in this relatively short time span here we present the integration of 33 records of relative palaeointensity3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 into a composite curve spanning the past 800 kyr we find that the intensity of the earth s dipole field has experienced large amplitude variations over this time period with pronounced intensity minima coinciding with known excursions in field direction reflecting the emergence of non dipole components no stable periodicity was found in our composite record and therefore our data set does not support the hypothesis that the earth s orbital parameters have a direct and strong influence on the geodynamo

tectonic significance of 24 ma crustal melting in the eastern hindu kush pakistan northward directed subduction has continued beneath the hindu kush from the mesozoic when the region formed part of the southern margin of asia until today the kohistan arc was accreted at ca 100 ma followed by the indian plate at 54 50 ma after the india asia collision a regional crustal melting event occurred at ca 25 21 ma to the east of the hindu kush in the karakoram range producing the baltoro pluton in the eastern hindu kush range most of the granitoids appear to be subduction related plutons that predate the india asia collision however the gharam chasma pluton is a two mica garnet tourmaline leucogranite that has intruded into staurolite grade schists and sillimanite k feldspar grade migmatites u pb ages on monazite xenotime and uraninite from undeformed samples of the gharam chasma pluton and a leucogranite dike that crosscuts the migmatites indicate that crustal melting occurred at ca 24 ma synchronous with the baltoro melting event this age also provides an upper limit on the age of the regional staurolite grade metamorphism in the eastern hindu kush

influence of upper air conditions on glaciers in scandinavia a simple model using once daily us national centers for environmental prediction us national center for atmospheric research ncep ncar re analysis upper air values estimates winter balance summer balance and net balance at ten glaciers in norway and two in sweden with 0 37 r 2 0 90 the october may arctic oscillation ao an index of sea level pressure slp in the northern hemisphere correlates with winter balance and net balance with 0 09 r 2 0 82 lower than the model in all but 3 of the 24 cases the october may north atlantic oscillation nao an slp gradient in the north atlantic has lower correlations than the ao for all but 5 of the 24 cases at all ten glaciers with records beginning before 1987 net balance became more positive after 1988 owing mainly to increased winter balance with summer balance changing little although winter temperatures increased they were still well below freezing so the rain snow division of the precipitation was only slightly affected increase in winter balance was due to increased precipitation caused by a change in atmospheric circulation resulting in more frequent westerly flow concurrent with the warming at 850 hpa westerly flow is 2 5 c warmer than easterly flow westerly flow warmed by 0 3 c easterly by 0 7 c both the ao and nao with which winter balance is positively correlated at all 12 glaciers were more positive after 1988

cooling exhumation and deformation in the hindu kush nw pakistan new constraints from preliminary 40ar 39ar and fission track analyses abstract asian crust in the hindu kush region in northern pakistan records a protracted history of rifting subduction and collision not commonly preserved within the himalaya because of this it is key to understanding the development of the southern eurasian margin both prior to and after collision with india new mica 40ar 39ar and apatite fission track geochronologic data from this region provide constraints on the kinematics of the hindu kush 40ar 39ar muscovite and biotite ages from the late cambrian kafiristan pluton are 379 7 1 7 ma and 47 2 0 3 ma respectively the muscovite age may record cooling or partial resetting while the biotite age is interpreted to record a thermal disruption associated with the early stages of continental collision in the himalayan system a 111 0 0 6 ma muscovite age from the northern part of the tirich mir pluton 123 ma old u pb is interpreted to indicate a recrystallization event 12 myrs after its intrusion in addition a younger muscovite age of 47 5 0 2 ma was derived from the opposite side of the same pluton in the immediate hanging wall of the tirich mir fault this eocene age is interpreted to represent the time of recrystallization during fault re activation in the early stages of india asia continent continent collision 40ar 39ar biotite analysis from the buni zom pluton yields an age of 61 6 1 1 ma and is interpreted to reflect cooling at mid upper crustal levels subsequent to the pluton s emplacement in the middle cretaceous finally 17 1 21 3 ma 40ar 39ar ages from the garam chasma pluton and surrounding metapelites indicate cooling immediately following crystallization of the leucogranite body in the earliest miocene latest oligocene the younger cooling history is resolved by fission track dating of apatite aft in the vicinity of the bounding tirich mir fault the tirich mir pluton yields an aft age of 1 4 0 3 ma which is consistent with active exhumation associated with the surface uplift of the 7700 m tirich mir peak the garam chasma pluton has a young age of 3 5 0 2 ma which also records rapid rock uplift and exhumation in the area finally an aft age of 9 1 2 1 ma was extracted from a metapelite in the footwall of an east verging thrust fault separating it from the garam chasma pluton to the west the difference in ages pliocene vs late miocene reflect differential cooling exhumation paths across that structure

meltwater runoff in a changing climate 1951 2099 at chhota shigri glacier western himalaya northern india meltwater runoff in the catchment area containing chhota shigri glacier western himalaya is simulated for the period 1951 2099 the applied mass balance model is forced by downscaled products from four regional climate models with different horizontal resolution for the future climate scenarios we use high resolution time series of 5 km grid spacing generated using the newly developed intermediate complexity atmospheric research model the meteorological input is downscaled to 300 m horizontal resolution the use of an ice flow model provides annually updated glacier area for the mass balance calculations the mass balance model calculates daily snow accumulation melt runoff as well as the individual runoff components glacial melt snowmelt and rain the resulting glacier area decreases by 35 representative concentration pathway rcp 4 5 scenario to 70 rcp 8 5 scenario by 2099 relative to 2000 the average annual mass balance over the whole model period 1951 2099 was 0 4 0 3 m w e a 1 average annual runoff does not differ substantially between the two climate scenarios however for the years after 2040 our results show a shift towards earlier snowmelt onset that increases runoff in may and june and reduced glacier melt that decreases runoff in august and september this shift is much stronger pronounced in the rcp 8 5 scenario

geodetic mass balance of the western svartisen ice cap norway in the periods 1968 1985 and 1985 2002 the geodetic mass balance of the western svartisen ice cap in northern norway is determined in this work from photogrammetry on vertical aerial photographs taken in 1968 1985 and 2002 the existing 1968 digital terrain model dtm was generated using analogue photogrammetry and the 1985 and 2002 dtms are newly generated using digital photogrammetry the geodetic mass balance for 1968 85 is 2 6 0 8 m w e and for 1985 2002 it is 2 0 1 6 m w e the area of western svartisen decreased from 190 km 2 in 1968 to 187 km 2 in 1985 and to 184 km 2 in 2002 the outlet glacier flatisen in the southeast retreated 1700 m over the two periods the geodetic mass balance is also determined for engabreen drainage basin as 2 1 0 9 m w e for the first period and 0 3 2 4 m w e for the second the results for engabreen are compared to traditional mass balances and the large deviations cannot be explained from uncertainties determined for the geodetic method the assessed errors contributing to the uncertainty in the geodetic mass balance are elevation errors uncertainties from the applied melt correction and the use of sorge s law assuming constant snow thickness and density

static mass balance sensitivity of arctic glaciers and ice caps using a degree day approach the purpose of this study is to enhance our understanding of the response of glaciers to climate change global sea level is affected by changes in glacier ice volume and melt water from glaciers is a principal water source in many regions this study applies glacier mass balance modelling with varying complexity and spatial resolution ranging from individual glaciers to regional and global assessments of glacier mass losses glaciers located in maritime environments generally show considerably higher mass balance sensitivities than those in continental settings on average an assumed increase in annual precipitation of 10 tends to offset the effect of an annual temperature change of 1 k by roughly 20 two case studies at storglaciaren sweden and hofsjokull iceland involve model results of future mass balance change and glacier melt induced changes in runoff applying a temperature and precipitation scenario for iceland in 2050 results in increased total runoff from hofsjokull by roughly one third and results emphasize the role of the firn layer in delaying water flow through glaciers yielding a redistribution of discharge within the year based on a global gridded data set of glacierized area the sea level equivalent from all mountain glaciers and ice caps outside the ice sheets in greenland and antarctica during 1961 2004 caused by changes in temperature and precipitation is estimated to be 0 58 0 34 mm a 1 the mountain glaciers and ice caps around antarctica alone contribute almost 40 of the global estimate and hence their contribution is considerably larger than previously assumed

exploring the potential of acquisition curves of the anhysteretic remanent magnetization as a tool to detect subtle magnetic alteration induced by heating recently many new methods and improved protocols to determine the absolute paleointensity of lavas reliably have been proposed here we study eight recent flows from three different volcanic edifices mt etna la palma and hawaii with the so called multispecimen parallel differential ptrm msp method including the recently proposed domain state correction msp dsc fabian and leonhardt 2010 surprisingly apart from approximately correct paleointensity values we observe major underestimates of the paleofield these deviations are possibly related to alteration that is not revealed by rock magnetic analysis we explore the potential of high resolution acquisition curves of the anhysteretic remanent magnetization arm to detect subtle alteration in the samples it appears that assessing changes in the arm acquisition properties before and after heating to the desired msp temperature discriminates between underestimates and approximately correct estimations of the paleofield in the outcomes of the msp dsc protocol by combining observations from the domain state corrected msp protocol and arm acquisition experiments before and after heating an extended msp protocol is suggested which makes it possible to assess the best set temperature for the msp dsc protocol and to label msp results as being approximately correct or an underestimate of the paleofield

the relationship between track shortening and fission track age reduction in apatite combined influences of inherent instability annealing anisotropy length bias and system calibration abstract the relationship between reduced track density 0 and reduced mean confined track length l l 0 during annealing has been studied for both spontaneous and induced tracks in four apatite samples with different chemical composition compositional range and origin and with spontaneous tracks giving mean confined track lengths varying from 14 5 m down to 12 3 m in all four apatites induced tracks show a relationship between l l 0 and 0 composed of two regions at higher values the two appear to be equal while at lower values l l 0 is greater than 0 this can be understood qualitatively in terms of the anisotropy of annealing and the bias against revelation of short tracks data from three apatites of uniform composition show near identical relationships in a sample showing a range of apatite compositions the point of divergence from the 1 1 relationship is somewhat higher than in the uniform composition apatites because individual grains anneal at different rates and the presence of highly annealed grains affects the track density more strongly than the mean track length spontaneous tracks show similar relationships to those observed for induced tracks in each sample when the data are renormalised to allow for the natural annealing present in the spontaneous tracks previous studies which led to the idea of length reduction without density reduction for spontaneous tracks did not renormalise density data as well as length data thereby distorting the apparent relationship data for the multi compositional apatite sample where annealing has taken place in geological conditions also agrees with the laboratory annealing data for both spontaneous and induced tracks this consistency suggests that a single process is responsible in all three cases implying that a laboratory based description of annealing can be applied to geological conditions with confidence recognition that spontaneous tracks in apatite are commonly annealed suggests that in general the fission track age should be interpreted as a reflection of both the time over which tracks have been retained and the distribution of etchable track lengths since the latter is a manifestation of the thermal history the fission track age should be interpreted in similar terms

stratigraphic evidence for an early collision between northwest india and asia the collision of india with asia1 had a profound influence on late cretaceous and cenozoic oceanography2 climate3 fauna extinctions4 and the motion of at least some of the earth s litho spheric plates5 as the collision ended a period of rapid indo asian convergence6 a precise knowledge of its timing when the crust of the neo tethys ocean was completely subducted7 at some point along the plate boundary is important for understanding its wider consequences but current estimates of the collision age range from 65 to 38 myr before present6 8 11 here we report the results of extensive biostratigraphic analyses from waziristan and kurram in northwest pakistan which show that accretionary prism and trench strata were first thrust onto the northwest indian passive margin after 66 myr but before 55 5 myr after this time volcanic arc fragments the accretionary prism trench material and imbricates of the north indian slope were raised to shallow water depths and overlapped by upper palaeocene shallow water carbonates and shales12 14 indicative of post collision thrusting in this region finally both the suture and the indian craton were overlapped by continuous unconformable upper lower eocene shallow marine strata demonstrating that suturing was complete by 49 myr

distributed mass balance and climate sensitivity modelling of engabreen norway department of geosciences university of oslo po box 1047 blindern no 0316 oslo norwayabstract assessing the impact of possible climate change on the water resources of glacierized areasrequires a reliable model of the climate glacier mass balance relationship in this study we simulate themass balance evolution of engabreen norway using a simple mass balance model based on dailytemperature and precipitation data from a nearby climate station ablation is calculated using adistributed temperature index method including potential direct solar radiation while accumulation isdistributed linearly with elevation the model was run for the period 1974 75 2001 02 for whichannual mass balance measurements and meteorological data are available parameter values weredetermined by a multi criteria validation including point measurements of mass balance mass balancegradients and specific mass balance the modelled results fit the observed mass balance well simplesensitivity experiments indicate a high sensitivity of the mass balance to temperature changes asexpected for maritime glaciers the results suggest further that the mass balance of engabreen is moresensitive to warming during summer than during winter while precipitation changes affect almostexclusively the winter balance

sensitivity of net mass balance estimates to near surface temperature lapse rates when employing the degree day method to estimate glacier melt glacier mass balance models that employ the degree day method of melt modeling are most commonly driven by surface air temperatures that have been downscaled over the area of interest using digital elevation models and assuming a constant free air lapse rate that is often taken to be the moist adiabatic lapse rate malr 6 58 ck m 1 air temperature lapse rates measured over melting glacier surface are however consistently less steep than free air values and have been shown to vary systematically with lower tropospheric temperatures in this study the implications of including a variable near surface lapse rate in a 26 year 1980 2006 degree day model simulation of the surface mass balance of devon ice cap nunavut canada are examined and compared with estimates derived from surface air temperatures downscaled using a constant near surface lapse rate equal to the measured summer mean 4 98 ck m 1 and the malr our results show that degree day models are highly sensitive to the choice of lapse rate when compared with 23 years of surface mass balance measurements from the northwest sector of the ice cap model estimates are significantly better when surface air temperatures are downscaled using a modeled daily lapse rate rather than a constant lapse equal to either the summer mean or the malr

a geomagnetic paleointensity stack between 0 8 and 3 0 ma from equatorial pacific sediment cores 1 we have conducted a paleomagnetic study of six sediment cores taken from the equatorial pacific three from the west caroline basin and three from the manihiki plateau in order to make a relative paleointensity stack during the matuyama and late gauss chrons the age of the bottom of the cores ranges from 1 2 to 3 0 ma the sediments show little downcore changes in the proxies of magnetic grain size and mineralogy and are hence suitable for estimating relative paleointensity the age of the cores is controlled by correlating variations in magnetic concentration magnetic susceptibility and or anhysteretic remanent magnetization arm to target oxygen isotope 18o curves all cores from the manihiki plateau show an upward decrease of the natural remanent magnetization nrm intensity normalized by arm and isothermal remanent magnetization irm with a decrease in sedimentation rate such a trend was removed before being converted to relative paleointensity this observation implies that a sedimentation rate change can affect relative paleointensity estimation relative paleointensity records from the six cores coincide well with each other within uncertainty of age we constructed a stacked curve between 0 8 and 3 0 ma the equatorial pacific paleointensity stack epapis 3ma after adjusting age the number of cores stacked is three to four throughout the record quasiperiodic paleointensity lows occur in the epapis 3ma and corresponding paleointensity lows can be found in previously published records with some shifts in age at least parts of the paleointensity minima seem to be accompanied by geomagnetic excursions the asymmetric sawtooth pattern of paleointensity variations is not observed at the matuyama gauss boundary and thereafter in our record a spectral analysis shows that 100 kyr orbital eccentricity frequency may exist in paleointensity variations during the matuyama and late gauss chrons

quantifying the effects of climate and surface change on glacier mass balance when a mass balance is computed using an outdated map that computation does not reveal the actual mass change but older maps often must be used for practical reasons we present a method by which with a few additional measurements each year a mass balance computed with an outdated map can be transformed into an actual mass change this is done by taking into account the influence of changes in areal extent and changes in the surface elevation of the glacier since the map was made this method is applied to south cascade glacier washington u s a as an example the computed cumulative mass balance from 1970 to 1997 would have been 16 too negative if the 1970 map had not been updated while the actual volume change of a glacier is relevant to hydrological studies the change that would have occurred on a constant or static surface is more relevant to certain glacier dynamics problems and most climate problems we term this the reference surface balance and propose that such a balance which deliberately omits the influence of changes in area and surface elevation is better correlated to climatic variations than the conventional one which incorporates those influences

low temperature magnetic behavior of titanomagnetites titanium substitution has a significant effect on the temperature dependence 5 300 k of low temperature saturation remanence and of initial susceptibility in synthetic and natural titanomagnetite fe3 xtixo4 0 x 0 4 and electronic and lattice relaxation phenomena over the entire titanomagnetite compositional range these features produce diagnostic magnetic behavior useful for titanomagnetite identification in natural samples moreover the apparent similarities between the thermal decay of low temperature remanence of titanomagnetite with pyrrhotite pure magnetite and superparamagnetic phases can lead to complications in interpreting low temperature remanence data when titanomagnetite is present

cooling history of the nw himalaya pakistan fission track and 40ar 39ar cooling ages indicate that the late tertiary cooling history of the himalayan ranges of northern pakistan is largely a function of uplift and erosion interpretation of cooling ages which range from under 0 5 ma to over 80 ma suggests that during the late tertiary long term uplift rates at least doubled from under 0 2 mm yr to in some cases well over 0 5 mm yr uplift rates show strong and systematic regional variations as well which reflect the greater uplift of eastern and northern regions the association of very rapid uplift and erosion with the nanga parbat haramosh massif can be explained by a locally vigorous collision of india with eurasia near a promontory of indian crust the resultant rapid uplift of the nanga parbat haramosh massif reactivated the main mantle thrust melange zone with a reversed sense of motion discontinuities in the coolingage distribution along the main mantle thrust in the southern swat hazara region may be the result of the thermal effects of overthrusting

environmental change in the sea of okhotsk during the last 1 1 million years on the basis of two sedimentary records from the central sea of okhotsk we reconstruct the closely coupled glacial interglacial changes in terrigenous flux marine productivity and sea ice coverage over the past 1 1 myr the correspondance of our sedimentary records to the china loess grain size record china loess particle timescale chiloparts suggests that environmental changes in both the sea of okhotsk area and in se asia were closely related via the siberian atmospheric high pressure cell during full glacial times our records point to a strong siberian high causing northerly wind directions the extension of the sea ice cover and a reduced amur river discharge deglacial maxima of terrigenous flux were succeeded by or synchronous to high productivity events marine productivity was strengthened during glacial terminations because of an effective nutrient utilization at times of enhanced water column stratification and high nutrient supply from fluvial runoff and sea ice thawing during interglacials se monsoonal winds prevailed analogous to today s summer situation of a pronounced mongolian heat low and a strong hawaiian high strong freshwater discharge induced by high precipitation rates in the amur drainage area and a seasonally reduced and mobile sea ice cover favored marine productivity although being considerably lower than during the terminations and a lowered flux of ice rafted detritus

alteration of magnetic mineralogy at the sulfate methane transition analysis of sediments from the argentine continental slope on the argentine continental slope off the rio de la plata estuary the sulfate methane transition smt has been encountered at shallow depths of a few meters below the seafloor at around this horizon where sulfate diffusing downward from the bottom water is met and reduced by methane rising from deeper in the sediment column intense alteration affects the detrital magnetic mineral assemblage less than 10 of the dominant primary low coercivity ferrimagnetic titano magnetite remains after alteration in the upper part of the suboxic environment underlying the iron redox boundary which is located at a depth of 0 1 m approximately 60 of the finer grained detrital fraction is already dissolved while the high coercivity minerals are relatively unaffected in the suboxic environment large portions 40 are diagenetically dissolved in the sulfidic smt zone nevertheless the characteristics of the magnetic residue are entirely controlled by a high coercivity mineral assemblage unlike common observations that diagenetic alteration produces coarser magnetic grain sizes in suboxic milieus a distinct overall fining is found in the sulfidic zone different factors should contribute to this effect scanning electron microscope analysis combined with x ray microanalysis identified fine grained titano magnetite preserved as inclusions in silicates and between high ti titanohematite lamellae and possibly of prime importance a comprehensive fragmentation of larger grains in the course of maghemitization the only secondary iron sulfide mineral detected is pyrite which is present as clusters of euhedral crystals or directly replaces titano magnetite the thermomagnetic measurements did not provide evidence for the presence of ferrimagnetic sulfides such as greigite different from other studies reporting a marked magnetic enhancement at around the smt due to the precipitation and preservation of such metastable ferrimagnetic sulfides a complete pyritization process will cause a distinct magnetic depletion like in the present case 2005 elsevier b v all rights reserved

mass balance of glaciers and ice caps consensus estimates for 1961 2004 1 working with comprehensive collections of directly measured data on the annual mass balance of glaciers other than the two ice sheets we combine independent analyses to show that there is broad agreement on the evolution of global mass balance since 1960 mass balance was slightly below zero around 1970 and has been growing more negative since then excluding peripheral ice bodies in greenland and antarctica global average specific balance for 1961 1990 was 219 112 kg m 2 a 1 representing 0 33 0 17 mm sle sea level equivalent a 1 for 2001 2004 the figures are 510 101 kg m 2 a 1 and 0 77 0 15 mm sle a 1 including the smaller greenland and antarctic glaciers global total balance becomes 0 38 0 19 mm sle a 1 for 1961 1990 and 0 98 0 19 mm sle a 1 for 2001 2004 for 1991 2004 the glacier contribution 0 77 0 26 mm sle a 1 is 20 30 of a recent estimate of 3 2 0 4 mm a 1 of total sea level rise for 1993 2005 while our error estimates are not rigorous we believe them to be liberal as far as they go but we also discuss several unquantified biases of which any may prove to be significant

geomagnetic paleointensity and environmental record from labrador sea core md95 2024 global marine sediment and ice core chronostratigraphy for the last 110 kyr piston core md95 2024 from the labrador rise provides a continuous record of rapidly deposited detrital layers denoting laurentide ice sheet lis instability the core also provides a high resolution record of geomagnetic paleointensity that is consistent with but at higher temporal resolution than previous labrador sea records correlation to the greenland summit ice cores grip gisp2 is achieved by assuming that labrador sea detrital layers correspond to cold stadials in the ice cores this allows a gisp2 official chronology to be placed on md95 2024 which is consistent with the inverse correlation between paleointensity and the flux of cosmogenic isotopes 10 be and 36 cl in greenland ice cores synchronous millennial scale variability observed from the md95 2024 paleointensity

a rapid method for magnetic granulometry with applications to environmental studies we have developed a rapid method of characterizing the fine scale variation sub micron to hundreds of microns m in the grain size of magnetite in long sediment cores this method is a new rock magnetic tool and can be readily applied to the following disciplines 1 environmental studies 2 hydrology 3 petrology and 4 geomagnetism the method consists of a comparative plot of the depth variation of two magnetic parameters the first parameter low field less than 0 1 millitesla mt or 1 oe susceptibility in a steady field is plotted on the abscissa the second parameter anhysteretic remanent magnetization arm imparted by a smoothly decreasing af of peak value 100 mt 1 000 oe in the presence of a weak steady field 0 01 0 1 mt or 0 1 1 oe is plotted on the ordinate for a sediment column in which the magnetic mineral is magnetite a plot of the two magnetic parameters shows transitions in the average magnetic grain size with depth as clearly discernible changes in the slope of a regression line fit to the individual points arm

modelling seasonal and spatial variations in the surface energy balance of haut glacier d arolla switzerland the impact of spatial and temporal variations in the surface albedo and aerodynamic roughness length on the surface energy balance of haut glacier d arolla switzerland was examined using a semi distributed surface energy balance model arnold and others 1996 the model was updated to incorporate the glacier wide effects of albedo and aerodynamic roughness length variations using parameterizations following brock 1997 after the model s performance was validated the glacier wide patterns of the net shortwave turbulent and melt energy fluxes were examined on four days representative of surface conditions in late may june july and august in the model meteorological conditions were held constant on each day in order that the impact of albedo and aerodynamic roughness length variations could be assessed independently a late summer snowfall event was also simulated albedo and aerodynamic roughness length variations particularly those associated with the migration of the transient snowline and the decay of the winter snowpack were found to exert a strong influence on the magnitude of the surface energy fluxes the importance of meteorological conditions in suppressing the surface energy fluxes and melt rate following a fresh snowfall was highlighted

sea ice conditions in the okhotsk sea during the last 550 kyr deduced from environmental magnetism 1 reconstructing past sea ice conditions in the okhotsk sea is important because sea ice conditions vary in response to global climate changes which in turn may affect global ocean circulation through intermediate water mass formation we conducted an environmental magnetic study of six cores from three stations in the central okhotsk sea to better understand temporal and spatial sea ice variations intercore correlations and age estimations are based mainly on geomagnetic paleointensity an oxygen isotope stratigraphy is available for one station magnetic susceptibility ms minima are accompanied by maxima in color b the ratio of the anhysteretic remanent magnetization susceptibility to saturation isothermal remanent magnetization karm sirm and the s ratio which indicates a higher proportion of biogenic to terrigenous magnetic components this reflects enhanced ocean productivity first order reversal curve diagrams and irm component analyses support the dominance of biogenic magnetite at ms minima in contrast color b karm sirm and s ratio values are low when ms is high which indicates an increased proportion of the terrigenous component that was probably transported as ice rafted debris ird for the southern two stations ird accumulation increased in glacial and deglacial periods which implies mobile sea ice conditions even in full glacials this was succeeded by extremely enhanced ocean productivity in early interglacials which suggests nearly ice free conditions for the northernmost station on the other hand ird accumulation was low in glacials and increased in early interglacials which indicates perennial sea ice coverage with little mobility in glacials succeeding ocean productivity enhancement was delayed compared to the southern stations

the geodetic mass balance of eyjafjallajokull ice cap for 1945 2014 processing guidelines and relation to climate mass balance measurements of icelandic glaciers are sparse through the 20th century however the large archive of stereo images available allows estimates of glacier wide mass balance dot b in decadal time steps since 1945 combined with climate records they provide further insight into glacier climate relationship this study presents a workflow to process aerial photographs 1945 1995 spy satellite imagery 1977 1980 and modern satellite stereo images since 2000 using photogrammetric techniques and robust statistics in a highly automated open source pipeline to retrieve seasonally corrected decadal glacier wide geodetic mass balances in our test area eyjafjallajokull s iceland 70 km 2 we obtain a mass balance of cdata dot curr b curr 1945 curr 2014 curr 0 27 pm 0 03 rm curr m w rm curr e rm rm curr a rm ndash curr 1 with a maximum and minimum of dot curr b curr 1984 curr 1989 curr 0 77 curr pm 0 19 rm curr m curr w rm curr e rm curr rm curr a rm curr ndash 1 and dot curr b curr 1994 curr 1998 curr 1 94 curr pm 0 34 rm curr m w rm curr e rm curr rm curr a rm curr ndash 1 respectively attributed to climatic forcing and dot curr b curr 2009 curr 2010 curr 3 39 rm curr pm rm curr 0 43 rm curr m w rm curr e rm curr rm curr a rm curr ndash 1 mostly caused by the april 2010 eruption the reference surface mass balances correlate with summer temperature and winter precipitation and linear regression accounts for 80 of the mass balance variability yielding a static sensitivity of mass balance to summer temperature and winter precipitation of 2 1 0 4 m w e a 1 k 1 and 0 5 0 3 m w e a 1 10 1 respectively this study serves as a template that can be used to estimate the mass balance changes and glaciers response to climate

annealing kinetics of fission tracks in zircon an experimental study a series of laboratory annealing experiments on zircon fission tracks has been carried out under heating conditions of 350 750 c for 10 1 103 hr i e 4 5 min 40 days variation in the confined lengths of spontaneous fission tracks was determined using zircon grains from nisatai dacite the fading contours of normalized mean track length r on the arrhenius diagram showed as sets of straight lines we performed a series of model fittings called the parallel and fanning models in order to describe the decrease in r with increasing temperature or heating time the lowest temperature limit of the zircon partial annealing zone zpaz was defined as r 0 95 and the highest as r 0 4 which approximately corresponded to the total fading of surface tracks extrapolation of the results of the laboratory experiments to the geological timescale gives for a heating duration of 106 yr estimated values of the zpaz of 210 320 c 60 c 2 with the parallel model 190 350 c 50 c 2 with the fanning model critical temperature t0 and 170 390 c 50 c 2 with the fanning model t0 the temperatures of the zpaz decrease by 20 c for an annealing duration that is an order of magnitude longer because the estimated closure temperature of zircon fission track analysis approximately corresponds to the middle of the zpaz these results support the previously estimated closure temperature of 240 c by varying the etching time it was revealed that significant removal of radiation damage occurs at r 0 93

rock magnetism of late neogene and pleistocene deep sea sediments relationship to sediment source diagenetic processes and sediment lithology we use bivariate scatter plots to illustrate variations in selected rock magnetic properties low field susceptibility anhysteretic and isothermal remanence of late neogene and pleistocene deep sea sediments from 16 sites in the arctic ocean north atlantic equatorial atlantic and north pacific ocean and the arabian sea our intention is to examine the ability of the rock magnetic properties to differentiate the sediments according to factors such as lithology geographical area and the dominant mode of terrigenous sedimentation which at these sites is via ice rafting via bottom currents or via eolian processes overall correlations between sediment magnetic properties and gross lithology is poor and factors such as the source and transport path of terrigenous sediment and detrital magnetic minerals together with the action of reductive diagenetic processes are the major controls on the magnetic properties on the bivariate scatter plots sites with major ice rafted contributions tend to have high sedimentary ferrimagnetic mineral concentrations relatively coarse ferrimagnetic grain sizes and scattered sample point distributions in contrast sites where we infer significant bottom current supply of terrigenous material have tightly grouped sample point distributions carbonate sediments in which the terrigenous component is supplied by eolian processes tend to have a broad range of magnetic mineral concentration caused by glacial interglacial fluctuations in carbonate accumulation and eolian activity sediments containing significant volcanogenic material have high concentrations of relatively coarse grained ferrimagnetic material reductive diagenesis is a significant determinant of sediment magnetic properties in high productivity areas and has the effect of preferentially removing the fine grained ferrimagnetic fraction causing a coarsening of the ferrimagnetic grain size distribution and a rise in the antiferromagnetic ferrimagnetic ratio

modelling 60 years of glacier mass balance and runoff for chhota shigri glacier western himalaya northern india glacier mass balance and runoff are simulated from 1955 to 2014 for the catchment 46 glacier cover containing chhota shigri glacier western himalaya using gridded data from three regional climate models 1 the rossby centre regional atmospheric climate model v 4 rca4 2 the regional atmosphere model remo and 3 the weather research and forecasting model wrf the input data are downscaled to the simulation grid 300 m and calibrated with point measurements of temperature and precipitation additional input is daily potential global radiation calculated using a dem at a resolution of 30 m the mass balance model calculates daily snow accumulation melt and runoff the model parameters are calibrated with available mass balance measurements and results are validated with geodetic measurements other mass balance model results and run off measurements simulated annual mass balances slightly decreased from 0 3 m w e a 1 1955 99 to 0 6 m w e a 1 for 2000 14 for the same periods mean runoff increased from 2 0 m 3 s 1 1955 99 to 2 4 m 3 s 1 2000 14 with glacier melt contributing about one third to the runoff monthly runoff increases are greatest in july due to both increased snow and glacier melt whereas slightly decreased snowmelt in august and september was more than compensated by increased glacier melt

late miocene to early pliocene tectonometamorphism and cooling in south central karakorum and indus tsangpo suture chogo lungma area ne pakistan abstract the chogo lungma glacier is located at the northeastern edge of the nanga parbat haramosh spur where the ladakh kohistan arc formations are laminated between the karakorum and high himalaya units in the karakorum metamorphic complex metamorphism of a pelitic and granitic protolith took place in two tectonometamorphic phases isoclinal folds 700 c 1 gpa were followed by doming 630 700 c 400 750 mpa in a compressional climax lemennicier et al 1996 one hornblende and two biotites associated to syntectonic magmatism with mantle affinities contemporaneous of doming give cooling ages between 3 0 and 7 7 ma a muscovite from an orthogneiss in the karakorum gives an age of 5 ma fast cooling 70 110 k ma has prevailed ever since two muscovites from a foliated intrusion emplaced on the thrust of the ladakh kohistan arc over the high himalaya crystallines have ages of 8 2 and 9 ma despite being collected in the same locality dating the thrust at just before 9 ma all this points to a coeval tectonometamorphism and thrusting in that area during the tortonian

geomagnetic relative paleointensity chronostratigraphy of sediment cores from the okhotsk sea abstract we conducted a paleomagnetic study of three piston cores from the central okhotsk sea to enable inter core correlation and age estimation using relative paleointensity of the geomagnetic field which can provide the basis for paleoceanographic studies in this area the cores are composed of diatom bearing dark olive gray silty clay magnetic overprints were generally removed by alternating field demagnetization of up to 10 mt magnetic properties reveal no evidence of reductive diagenesis or magnetite dissolution the anhysteretic remanent magnetization arm was used as a normalizer for relative paleointensity estimations because there is a smaller coherence between normalized intensity and the arm than with saturation isothermal remanent magnetization sirm depths of the three cores were converted to ages by correlating relative paleointensity variations with those from ocean drilling program site 983 which was selected as a target curve because of its higher resolution than the widely used sint 800 paleointensity stack the age at the bottom of the cores is estimated to be between 360 and 540 ka inter core correlation using relative paleointensity variations reveals that changes in magnetic properties such as magnetic susceptibility and magnetic mineral grain size are not synchronous between the northernmost site and the southern two sites despite their close proximity which indicates regional differences in paleoenvironmental variations associated with glacial interglacial changes nevertheless relative paleointensity variations among the three cores are mutually consistent and agree with other published paleointensity curves which indicates that our paleointensity records are not influenced significantly by lithological changes

influence of north atlantic climate variability on glacier mass balance in norway sweden and svalbard climate variability can complicate efforts to interpret any long term glacier mass balance trends due to anthropogenic warming here we examine the impact of climate variability on the seasonal mass balance records of 14 glaciers throughout norway sweden and svalbard using dynamical adjustment a statistical method that removes orthogonal patterns of variability shared between each mass balance record and sea level pressure or sea surface temperature predictor fields for each glacier the two leading predictor patterns explain 27 81 of the winter mass balance variability and 24 69 of the summer mass balance variability the spatial and temporal structure of these patterns indicates that accumulation variability for all of the glaciers is strongly related to the north atlantic oscillation nao with the atlantic multidecadal oscillation amo also modulating accumulation variability for the northernmost glaciers given this result predicting glacier change in the region may depend on nao and amo predictability in the raw mass balance records the glaciers throughout southern norway have significantly negative summer trends whereas the glaciers located closer to the arctic have negative winter trends removing the effects of climate variability suggests it can bias trends in mass balance records that span a few decades but its effects on most of the longer term mass balance trends are minimal

the impact of climate change on future frontal variations of briksdalsbreen western norway a flowline model coupled with a surface mass balance model forced by climate data from bergen was used to simulate future frontal changes of briksdalsbreen a western outlet glacier from jostedalsbreen western norway under various future climate scenarios the model was used to calculate the time lag of frontal response to a sudden and short change in the mass balance according to the model the front has a time lag for maximum advance rate of 4 5 years in close agreement with previous studies the response time for briksdalsbreen was calculated by running the model for 200 years with different mass balance perturbations for mass balance perturbations of 0 3 and 0 6 m w e the model yields response times of 52 and 60 years respectively we ran the model from 1963 to 2007 with measured mass balance data and from 2007 to 2085 using calculated mass balances from 12 different climate scenarios the model predicts retreat up the steep valley from the lake inlet with a total frontal retreat of 2 5 5 0 km by 2085 a spectacular icefall one of the main tourist attractions in western norway may thus disappear and the glacier may become a plateau glacier that will gradually melt down

sensitivities of glacier mass balance and runoff to climate perturbations in norway this study evaluates sensitivities of glacier mass balance and runoff to both annual and monthly perturbations in air temperature and precipitation at four highly glacierized catchments engabreen in northern norway and alfotbreen nigardsbreen and storbreen which are aligned along a west east profile in southern norway the glacier mass balance sensitivities to changes in annual air temperature range from 1 74mw e k 1 for alfotbreen to 0 55mw e k 1 for storbreen the most maritime and the most continental glaciers in this study respectively the runoff sensitivities of all catchments are 20 25 per degree temperature change and 6 18 for a 30 precipitation change a seasonality of the sensitivities becomes apparent with increasing continentality the sensitivity of mass balance and runoff to temperature perturbations during summer increases and the sensitivity of annual runoff to both temperature and precipitation perturbations is constricted towards changes during the ablation period comparing sensitivities in northern and southern norway as well as the variability across southern norway reveals that continentality influences sensitivities more than latitude does

effect of summer snowfall on glaciermass balance it has been postulated that heavy summer snowfalls have a large impact on the mass balance of mid latitude glaciers because they simultaneously add mass to the glacier and reduce the amount of absorbed solar radiation an automatic weather station aws on the snout of morteratschgletscher switzerland registered a large summer snowfall event on 10 11 july 2000 sonic rangers recorded about 20 cm of new snow on the snout and about 50 cm near the equilibrium line we have used data fromthe aws to study the impact on themelt process the data show that in the ablation zone of the glacier the snow has melted and the effect on the albedo has disappeared after about 5 days the suppression of themelt by the high albedo of the fresh snow is an important effect for the ablation zone we find a feedback factor of about four that is the total effect of the snowfall event on the annual specific balance is about four times the amount of mass added during the event we have also used a mass balance model with 25m spatial resolution to assess the impact of the snowfall on the net balance of the entire glacier we find the strongest effects just below the equilibrium line averaged over the glacier the amount of snow deposited was 224mmw e the calculated effect on the total mass balance of the glacier is 354mmw e