measurement and parameterization of albedo variations at haut glacier d arolla switzerland spatial and temporal variations of surface albedo on haut glacier d arolla switzerland during the 1993 and 1994 ablation seasons are described correlation and regression analyses are used to explain the albedo variations in terms of independent meteorological and surface property variables parameterizations are developed which allow estimation of albedo variation in surface energy balance models snow albedo is best estimated from accumulated daily maximum temperatures since snowfall on deep snow 0 5 cm w e depth a logarithmic function is used while on shallow snow 0 5 cm w e depth an exponential function is used to enable the albedo to decay to the underlying ice or debris albedo the transition from deep to shallow snow is calculated as a function of decreasing snow depth combined r 2 0 65 this new parameterization performs better than earlier schemes because accumulated daily maximum temperatures since snowfall correlate strongly with snow grain size and impurity concentration the main physical controls on snow albedo ice albedo may be parameterized by its relationship to elevation r 2 0 28 but this approach results in only a small improvement over the assumption of a constant mean ice albedo

surface albedo measurements over snow and blue ice in thematic mapper bands 2 and 4 in dronning maud land antarctica ground based observations of broadband narrowband in landsat thematic mapper bands 2 0 52 0 60 m and 4 0 76 0 90 m and bidirectional reflectance are used to study the albedo of blue ice and snow the measured broadband albedos for blue ice and snow are 0 60 and 0 78 respectively the narrowband albedos in bands 2 and 4 for snow are 0 97 and 0 86 respectively and for blue ice are 0 87 and 0 51 respectively the measurements are point values and used to verify existing weighting functions between the broadband and narrowband albedos blue ice data do not comply with the existing functions furthermore a new function for blue ice is derived a simple two stream model is used to illustrate the behavior of the snow and ice albedo as a function of reflection and absorption the bidirectional reflectance measurements are used to derive bidirectional reflectance distribution functions brdfs for snow and blue ice the brdf of blue ice exhibits a maximum brightening in the forward limb around a zenith angle close to the solar zenith angle indicating specular reflectance of blue ice which is not visible for snow and glacier ice surfaces

remote sensing of the albedo and detection of the slush line on the greenland ice sheet advanced very high resolution radiometer images of a section of the greenland ice sheet western part between 64 5 and 70 5 n with a size of 667 n s by 700 w e km were processed in order to retrieve the surface albedo the images were for the summer seasons of 1990 1997 inclusive and results were compared to simultaneous mass balance measurements carried out along the transect 67 n the main findings are as follows first many images show a distinct transition from low spatial variability of the albedo at higher elevations to higher spatial variability of the albedo at lower elevations it is argued that these transitions most likely correspond to transitions at the surface slush line in short from the area that is uniformly covered by snow to a mosaic of snow patches slush and ice second 70 of the interannual variations in the mean specific mass balance can be explained by interannual variations in the maximum elevation of the slush line i e the slush limit however a higher percentage 82 can be explained by interannual variations in the sum of positive degree days third in 3 years with a relatively large amount of melt the inland migration of the slush line stopped or slowed considerably down at a fixed distance from the ice sheet margin we believe that this so called maximum slush line coincides with an abrupt change in the density profile the maximum slush line forms an important limitation for the use of satellite data to monitor interannual variations in the mass balance its position is a climate indicator and was determined for the entire section of the greenland ice sheet investigated

shortwave broadband black sky surface albedo estimation for arctic sea ice using passive microwave radiometer data 1 a new remote sensing method to estimate the optical broadband black sky surface albedo using passive microwave radiometer data has been developed in this research the advanced very high resolution radiometer avhrr based shortwave broadband black sky albedos processed using the algorithms of the new surface broadband albedo cm saf product sal and the advanced microwave scanning radiometer amsr e microwave data from the national snow and ice data center boulder colorado have been employed to analyze the correspondence between avhrr based optical albedo and microwave brightness temperature amsr e frequencies of 6 9 18 7 and 36 5 ghz have been tested by fitting a third degree polynomial curve to the sal albedo and the amsr e data points the best correlation occurs in 6 9 ghz vertical polarization brightness temperature r2 0 92 to illustrate and compare the spatial variabilities of the sal and amsr e albedos of the sea ice during the melting and refreezing period maps of 13 weeks have been prepared of both albedos from june to august 2007 the albedo time series from amsr e and avhrr data are calculated for the combined sea ice and open water cover for the northern hemisphere as a whole and for six specific sea ice regions the arctic ocean the kara and barents seas the greenland sea the labrador sea hudson bay and the canadian archipelago the standard errors between the optical and passive microwave estimates varied from about 0 001 greenland sea to 0 04 canadian archipelago being 0 013 on the average in absolute units the relative standard errors are then smaller than 5 in most of the regions

development and validation of a snow albedo algorithm for the modis instrument a prototype snow albedo algorithm has been developed for the moderate resolution imaging spectroradiometer modis it complements existing modis products by providing albedo measurements for areas mapped as snow on a global daily basis by modis cloud detection and atmospheric correction are accomplished using existing modis products models of the bidirectional reflectance of snow created using a discrete ordinate radiative transfer disort model are used to correct for anisotropic scattering effects over non forested surfaces initial algorithm validation is undertaken through comparisons with broadband albedo measurements made at the u s national oceanic and atmospheric administration noaa surface radiation budget network surfrad site in fort peck mt in situ surfrad albedo measurements are compared to daily modis snow albedo retrievals for the period 21 26 november 2000 created from five narrow to broadband albedo conversion schemes the prototype modis algorithm produces reasonable broadband albedo estimates maximum daily differences between the five modis broadband albedo retrievals and in situ albedo are 15 daily differences between the best modis broadband estimate and the measured surfrad albedo are 1 8 however no single conversion scheme consistently provides the closest albedo estimate further validation and algorithm development using data from north america and greenland is ongoing

investigation of the effect of surface heterogeneity and topography on the radiation environment of palmer station antarctica with a hybrid 3 d radiative transfer model we have developed and used a monte carlo radiative transfer code to investigate how surface topography and heterogeneous snow ice distributions affect the downwelling irradiance at palmer station antarctica 64 76 s 64 07 w the monte carlo calculations treat a three dimensional 3 d atmospheric volume which extends from the surface to 100 km altitude and has a 20 km 20 km footprint on the southwest coast of anvers island the radiative transfer calculations include the effects of molecular absorption rayleigh scattering and clouds the surface interaction is modeled explicitly the trajectories of reflected photons are computed from stochastic bidirectional directional reflectance functions and their paths are traced through multiple interactions with complex surface features computed results for a range of cloud optical depth solar zenith angle and surface albedo are presented comparisons of the 3 d model calculations to plane parallel model predictions show that the effective albedo which characterizes a given ice distribution is affected by regions surprisingly far from the point of interest under low clouds zcloud 1 km surface irradiance measurements over a snow surface are significantly affected by the dark ocean surface more than 7 km away for the opposite case of irradiance observations over ocean the effect of a distant snow surface is not significant at ranges greater than 2 or 3 km since the radius of influence depends on atmospheric transmission and surface albedo the effective albedo varies spectrally neglect of this nonlocal albedo effect may significantly degrade the accuracy of radiation diagnostics that depend on spectral intensity ratios

modelling albedo and specific balance of the greenland ice sheet calculations for the sondre stromfjord transect glacio meteorological data obtained during the greenland ice margin experiment gimex investigations in west greenland the sondre stromfjord transect have been used to test and calibrate four energy balance mass balance models for the ice snow surface the region is characterised by the development of a wide zone of low surface albedo in the course of the melting season this zone was simulated in one of the energy balance models by including the effect of surficial meltwater on albedo observed mass balance and albedo data were used to constrain the models although all the models are capable of predicting the transect balance reasonably well only the model with the meltwater albedo coupling is able to reproduce the observed albedo pattern and mass balance profile along the transect by including the feedback between surficial meltwater and albedo in the model the sensitivity of the specific balance to changes in air temperature is found to be greatest just below the equilibrium line in contrast to what is generally found for valley glaciers a 1 k warming of the air temperature would increase the mean ablation along the transect by 0 5 m w e year 1

measuring snow and glacier ice properties from satellite satellite remote sensing is a convenient tool for studying snow and glacier ice allowing us to conduct research over large and otherwise inaccessible areas this paper reviews various methods for measuring snow and glacier ice properties with satellite remote sensing these methods have been improving with the use of new satellite sensors like the synthetic aperture radar sar during the last decade leading to the development of new and powerful methods such as sar interferometry for glacier velocity digital elevation model generation of ice sheets or snow cover mapping some methods still try to overcome the limitations of present sensors but future satellites will have much increased capability for example the ability to measure the whole optical spectrum or sar sensors with multiple polarization or frequencies among the methods presented are the satellite derived determination of surface albedo snow extent snow volume snow grain size surface temperature glacier facies glacier velocities glacier extent and ice sheet topography in this review emphasis is put on the principles and theory of each satellite remote sensing method an extensive list of references with an emphasis on studies from the 1990s allows the reader to delve into specific topics

the ablation zone in northeast greenland ice types albedos and impurities ice types albedos and impurity content are characterized for the ablation zone of the greenland ice sheet in kronprinz christians land 80 n 24 w along this ice margin the width of the ablation zone is only about 8 km the emergence and melting of old ice in the ablation zone creates a surface layer of dust that was originally deposited with snowfall high on the ice sheet this debris cover is augmented by locally derived wind blown sediment subsequently the surface dust particles often aggregate together to form centimetre scale clumps that melt into the ice creating cryoconite holes the debris in the cryoconite holes becomes hidden from sunlight raising the area averaged albedo relative to surfaces with uniform debris cover spectral and broadband albedos were obtained for snow ice hummocks debris covered ice cryoconite studded ice and barren tundra surfaces broadband ice albedos varied from 0 2 for ice with heavy loading of uniform debris to 0 6 for ice hummocks with cryoconite holes the cryoconite material itself has albedo 0 1 when wet areal distribution of the major surface types was estimated visually from a transect video as a function of distance from the ice edge 330 m a s l ablation rates were measured along a transect from the ice margin to the slush zone 8 km from the margin 550 m a s l traversing both pleistocene and holocene ice ablation rates in early august averaged 2 cm d 1 impurity concentrations were typically 4 3 mg l 1 in the subsurface ice surface concentrations were about 16 g m 2 on surfaces with low impurity loading and heavily loaded surfaces had concentrations as high as 1 4 kg m 2 the mineralogical composition of the cryoconite material is comparable with that of the surrounding soils and with dust on a snowdrift in front of the ice margin implying that much of the material is derived from local sources a fine mode clay is present in the oldest ice but not in the nearby soil suggesting that its origin is from wind deposition during pleistocene glaciation

surface radiation balance in the ablation zone of the west greenland ice sheet 1 we present 4 years of radiation observations and derived cloud properties from the ablation zone of the west greenland ice sheet 67 n data were collected using three automatic weather stations located at 6 38 and 88 km from the ice sheet margin at elevations of 490 1020 and 1520 m asl this part of greenland is characterized by a 150 km wide tundra a 100 km wide ablation zone and an average equilibrium line altitude of 1500 m asl at the lowest station snow is redistributed by the wind in crevasses and gullies leading to very little measured winter accumulation as a result glacier ice albedo 0 55 is at the surface throughout the melting season at 1020 m asl the winter snow cover typically disappears in mid to end june at 1520 m asl superimposed ice briefly reaches the surface at the end of the ablation season the combined effect of decreasing surface albedo and increasing cloud optical thickness as summer progresses causes absorbed shortwave radiation to peak in june at low elevations but progressively later at higher elevations incoming longwave radiation peaks in august in response to increased cloud optical thickness and heating of the atmosphere over the snow and ice free surroundings the ice sheet margin experiences continuous melting in june july and august this limits the emission of longwave radiation causing net longwave radiation to peak in august further enhancing melt the sum of these effects is that summer net radiation increases sharply toward the ice sheet margin to resolve this correctly requires high resolution climate models in the order of 10 km or better

classification of glacier zones in western greenland using albedo and surface roughness from the multi angle imaging spectroradiometer misr the greenland ice sheet has been the subject of mass balance and melt measurements over the past two decades and its margins have shown significant thinning in recent years surface characteristics of the ice sheet margins are strongly modified by the annual process of snow accumulation and melt in this work we explore spatial and temporal relationships between near infrared albedo and surface roughness from the multi angle imaging spectroradiometer misr aboard nasa s terra satellite our study area is a region in western greenland in the vicinity of jakobshavn glacier and its upland drainage basin we compute near infrared albedo from misr data using imagery over the april to september period for 2000 through 2005 near infrared albedo is inversely related to both snow age and melt intensity we map surface roughness using the normalized difference angular index ndai applied to misr atmospherically corrected surface hemispherical directional reflectance in previous work the ndai has been correlated with surface roughness on the scale of about 70 m we have further substantiated that relationship here the ndai and albedo images for each of the six years are used in an isodata unsupervised classification classification results for the individual years show year to year differences which appear to depend on the number and temporal distribution of images with minimal cloud cover as well as interannual differences in ice sheet surface properties the year 2003 which had the greatest number of images with minimal cloud cover shows good correspondence with previously mapped glacier zones however we do not have an isodata class that corresponds to the dry snow zone and we see greater differentiation between zones at lower elevations within each isodata class distinct relationships between near infrared albedo and surface roughness emerge and in all cases but one there is an inverse temporal relationship between albedo and roughness the one class that shows a direct relationship between albedo and surface roughness is hypothesized to be the superimposed ice zone while still somewhat preliminary these results suggest that concurrent measurements of near infrared albedo and surface roughness have significant potential for ice sheet surface characterization as well as for ongoing monitoring

how robust are in situ observations for validating satellite derived albedo over the dark zone of the greenland ice sheet abstract calibration and validation of satellite derived ice sheet albedo data require high quality in situ measurements commonly acquired by up and down facing pyranometers mounted on automated weather stations aws however direct comparison between ground and satellite derived albedo can only be justified when the measured surface is homogeneous at the length scale of both satellite pixel and in situ footprint here we use digital imagery acquired by an unmanned aerial vehicle to evaluate point to pixel albedo comparisons across the western ablating margin of the greenland ice sheet our results reveal that in situ measurements overestimate albedo by up to 0 10 at the end of the melt season because the ground footprints of aws mounted pyranometers are insufficient to capture the spatial heterogeneity of the ice surface as it progressively ablates and darkens statistical analysis of 21 aws across the entire greenland ice sheet reveals that almost half suffer from this bias including some aws located within the wet snow zone

comparison of avhrr derived and in situ surface albedo over the greenland ice sheet abstract this paper discusses a methodology for computing the clear sky surface albedo over the greenland ice sheet by using advanced very high resolution radiometer avhrr global area coverage visible and near infrared reflectances this approach is then used to map the monthly changes in albedo over the entire greenland ice sheet during the spring and summer months the methodology includes corrections for the intervening atmosphere by using the 6s radiative transfer model additional corrections for the anisotropic nature o f snow reflectance and the conversion from a marrow into a broadband albedo are made based on in site measurements from the swiss federal institute of technology university of colorado camp at 69 34 n 49 18 w comparison with surface albedo field ineasureinents indicates that before the onset of snoic melt agreement is good between the satellite derived and measured surface albedo after melt begins it is difficult to compare the satellite values with the field data owing to melt water ponding on the ice sheet surface with appropriate modifications the 6s radiative transfer model is suitable for atmospherically correcting avhrr visible and near infrared radiances atmospherically polar regions

seasonal variations in greenland ice sheet motion inland extent and behaviour at higher elevations abstract we present global positioning system observations that capture the full inland extent of ice motion variations in 2009 along a transect in the west greenland ice sheet margin in situ measurements of air temperature and surface ablation and satellite monitoring of ice surface albedo and supraglacial lake drainage are used to investigate hydrological controls on ice velocity changes we find a strong positive correlation between rates of annual ablation and changes in annual ice motion along the transect with sites nearest the ice sheet margin experiencing greater annual variations in ice motion 15 18 than those above 1000 m elevation 3 8 patterns in the timing and rate of meltwater delivery to the ice bed interface provide key controls on the magnitude of hydrologically forced velocity variations at each site in the lower ablation zone the overall contribution of variations in ice motion to annual flow rates is limited by evolution in the structure of the subglacial drainage system at sites in the upper ablation zone a shorter period of summer melting and delayed establishment of a hydraulic connection between the ice sheet surface and its bed limit the timeframe for velocity variations to occur our data suggest that land terminating sections of the greenland ice sheet will experience increased dynamic mass loss in a warmer climate as the behaviour that we observe in the lower ablation zone propagates further inland findings from this study provide a conceptual framework to understand the impact of hydrologically forced velocity variations on the future mass balance of land terminating sections of the greenland ice sheet

a simple derivation of the effective stress coefficient for seismic velocities in porous rocks the effect of confining stress and pore pressure on seismic velocities is important for such geophysical applications as overpressure prediction from seismic data eaton 1975 dutta 2002 huffman 2002 sayers et al 2002 and more recently for hydrocarbon production monitoring using time lapse seismic measurements tura and lumley 1999 landr 2001 the dependence of seismic velocity on pressure has been confirmed for a variety of rocks by laboratory measurements of elastic wave velocities in samples with varying pressure in pore fluids see e g wyllie et al 1958 todd and simmons 1972 eberhart phillips et al 1989 prasad and manghnani 1997 in general for a rock subjected to a given confining stress c higher pore pressures p correspond to lower compressional and shear velocities confining stress has a similar effect but with opposite sign on seismic velocities

neglecting ice atmosphere interactions underestimates ice sheet melt in millennial scale deglaciation simulations dynamic and thermodynamic interactions between the atmosphere and underlying ice sheets are generally not represented in the traditional one way boundary condition forcing used to drive ice sheet models this shortcoming is investigated through a series of idealized millennial scale deglaciation simulations designed to isolate the mechanisms regulating the deglaciation timescale of the laurentide ice sheet sensitivity experiments indicate that the conventional use of one way non interactive atmospheric forcing fields leads to an unrealistically insensitive melt response in the ice sheet model even when atmospheric carbon dioxide is set to modern preindustrial levels and earth s angle of obliquity is set to its early holocene value a more realistic deglaciation timescale is obtained only through the application of a new two way interactive asynchronous ice atmosphere coupling scheme and a seasonal ice albedo parameterization that accounts for the observed darkening of ice in the moist summertime ablation zone

the surface albedo of the greenland ice sheet satellite derived and in situ measurements in the sondre stromfjord area during the 1991 melt season the temporal and spatial variation in the surface albedo of the greenland ice sheet during the ablation season of 1991 is investigated the study focuses on an area east of sondre stromfjord measuring 200 km by 200 km and centred at 67 5 n 48 13 w the analysis is based on satellite radiance measurements carried out by the advanced very high resolution radiometer avhrr the broad band albedo is estimated from the albedos in channel 1 visible and channel 2 near infrared the results are calibrated with the surface albedo of sea and dry snow satellite derived albedos are compared with gimex ground measurements at three stations there is a high degree of consistency in temporal variation at two of the three stations large systematic differences are attributed to albedo variations on subpixel scale in the course of the ablation season four zones appear each parallel to the ice edge it is proposed that these are in order of increasing altitude i clean and dry ice ii ice with surface water iii superimposed ice and iv snow an extensive description of these zones is given on the basis of the situation on 25 july 1991 zones i iii and iv reveal fairly constant albedos 0 46 0 65 and 0 75 on average whereas zone ii is characterised by an albedo minimum 0 34 survey of the western margin of the greenland ice sheet up to 71 n shows that the zonation occurs between 66 and 70 n

assessment of greenland albedo variability from the advanced very high resolution radiometer polar pathfinder data set the advanced very high resolution radiometer polar pathfinder app data set is used to examine the variability of the surface albedo over greenland analysis of the app albedo record from 1981 to 1998 show anomalously low albedo during 1995 and 1998 over most of the ice sheet as compared with the other years the low albedo encountered during these years suggests that the ice sheet experienced considerable melt in 1995 and 1998 particularly near the western margin of the ice sheet conversely anomalously high albedos were found in 1992 as a result of colder temperatures and hence less melt following the eruption of mount pinatubo the relationship between the annual north atlantic oscillation nao index and the mean summer albedo from all the stations reveals a positive correlation of 0 44 and a positive correlation of 0 55 for the southern part of the ice sheet therefore variations in the mean summer albedo over greenland can in part be explained by variations in the nao such that during periods of intensification of the normal mode of the nao the mean summer albedo is above normal trend analysis reveals an overall downward trend in surface albedo from 1981 to 1998 which agrees with recent trends in melt and precipitation however the trend was found not to be statistically significant but rather influenced by the low albedo in recent years

validation of avhrr and modis derived albedos of snow and ice surfaces by means of helicopter measurements we describe the validation of surface albedos of snow and glacier ice as derived from advanced very high resolution radiometer avhrr and moderate resolution imaging spectrometer modis satellite data for this purpose we measured surface albedos from a helicopter over vatnajokull iceland and the kangerlussuaq transect western part of the greenland ice sheet in thematic mapper tm bands 2 and 4 and avhrr bands 1 and 2 and converted these values to measured albedos in three modis bands relative to other validation methods our helicopter measurements have the advantages of larger spatial coverage and of almost direct measurements in satellite sensor spectral bands we found the smallest differences between the satellite derived and helicopter albedos for the kangerlussuaq transect for avhrr data a mean difference of 0 01 in both bands with the satellite in near nadir position and for two modis images a mean difference of 0 00 0 02 for bands 2 and 4 and 0 03 for band 1 for two avhrr images of vatnajokull we found mean differences of up to 0 06 differences are primarily due to errors in the satellite derived albedos which in turn are mainly caused by errors in the calibration coefficients of the satellite sensors and insufficient knowledge of the angular distribution of the radiation reflected by snow and ice satellite data obtained from view zenith angles larger than 50 55 appeared to be unsuitable

physical properties of shale at temperature and pressure deformational properties p wave and s wave velocities and electrical resistivity were measured for three north sea malm shales in the laboratory under pressures to 800 bars and temperatures to 100 c these data were used to evaluate how factors such as mineralogy microstructure compaction and pore fluid conductivity affect a shale s seismic and electrical responses deformation in the shales is dominated by inelastic processes which cause time dependent changes in velocity resistivity and pore pressure overall shales are less sensitive to pressure changes as compared to sandstones of similar porosity however changes in temperature result in large changes in physical properties as compared to sandstones or shaly sands p wave and s wave velocities may decrease by as much as 10 percent over the temperature range studied and calculated activation energies for surface conduction are nearly twice those observed in shaly sands these comparisons emphasize fundamental differences in fabric among the

narrowband to broadband albedo conversion for glacier ice and snow based on aircraft and near surface measurements this article presents albedo measurements of snow and glacier ice at vatnajokull iceland and the kangerlussuaq transect greenland radiative fluxes were measured in the broadband and in four narrowbands namely thematic mapper tm bands 2 and 4 and advanced very high resolution radiometer avhrr bands 1 and 2 the incoming fluxes were measured near the ground and the outgoing fluxes from a helicopter extracts of the data collected over snow ice supraglacial moraines supraglacial lakes and tundra are discussed using the data sets from iceland and greenland and data sets with entirely ground based albedo measurements from the morteratschgletscher switzerland and scharffenbergbotnen antarctica new equations for narrowband to broadband ntb conversion were developed they have a residual standard deviation of 0 011 for tm and 0 008 for avhrr and can be applied without having to classify the surface the helicopter data are also used to develop criteria for distinguishing different types of surfaces which are needed for the application of bidirectional reflectance distribution functions brdfs snow can be distinguished from ice by defining a threshold for a single narrowband albedo the ratio of the albedos in tm4 and tm2 and to a lesser extent the ratio of the albedos in avhrr2 and avhrr1 may serve as a proxy for the surface characteristics of glacier ice in terms of concentrations of water debris and dust

temporal and spatial variation of the surface albedo of the morteratschgletscher switzerland as derived from 12 landsat images this investigation uses landsat images from 12 days in 1999 and 2000 to study the spatial and temporal variation in surface albedo of a glacier with a rugged topography morteratschgletscher switzerland our retrieval method considers all processes that substantially influence the relationship between the satellite signal and the surface albedo the correction for the anisotropy of the reflected radiation field of ice and snow ranges up to 0 10 depending on wavelength band solar zenith angle and surface type we analyzed the uncertainties in the retrieval method and mainly expect errors in satellite derived albedos for areas with large variation in topography and high albedos the latter is due to application of bidirectional reflectance distribution function brdf parameterizations for the anisotropic correction to albedos outside the parameterizations validity on average satellite derived albedos exceed the measured surface albedo by 0 03 the glacier tongue is characterized by bands of low and high albedo relating to ice with higher and lower concentrations of debris the ice albedo shows no dependence on altitude except at 2000 2200 m a s l it increases during summer which is likely associated with rainfall as concluded from a comparison between summer rainfall and measured albedos

spring temperature variability relative to the north atlantic oscillation and sunspots a correlation analysis with a monte carlo implementation abstract a reconstruction of past spring temperatures was analysed and compared to long term records of the north atlantic oscillation nao and sunspots this palaeoclimate reconstruction built previously using multiple proxy evidence of historical and natural sources from southwest finland explained approx 70 of the instrumental temperature variance over a spring season february june and covered the time period from 1750 to the present correlations between the nao and sunspots appear markedly high and based on monte carlo tests statistically significant p

carbonaceous particles reveal that late holocene dust causes the dark region in the western ablation zone of the greenland ice sheet a dark region in the western ablation zone of the greenland ice sheet is caused by outcropping ice layers that contain more dust than the surrounding brighter ice these higher amounts of dust were deposited in the accumulation zone of the ice sheet and travelled with the ice to the ablation zone to deduce the period and the causes of this higher dust deposition carbonaceous particles in ice samples from the dark region and from brighter reference ice were analysed and used for dating samples including ice from directly below the surface contain high amounts of modern organic carbon probably from microorganisms on the ice surface deeper samples reveal low amounts of carbonaceous particles which are originally deposited in the accumulation zone the amount of outcropping carbonaceous particles in the dark region seems significantly higher than in the reference ice one of the samples that contained material initially deposited in the accumulation zone was dated and revealed late holocene ages coinciding with a period of enhanced eolian activity in the nearby tundra therefore variable eolian activity during the holocene effected dust fluxes towards the ice and hence leads to albedo variations in the present ablation zone of the ice sheet