a snow transport model for complex terrain as part of the winter environment in middle and high latitude regions the interactions between wind vegetation topography and snowfall produce snow covers of non uniform depth and snow water equivalent distribution a physically based numerical snow transport model snowtran 3d is developed and used to simulate this three dimensional snow depth evolution over topographically variable terrain the mass transport model includes processes related to vegetation snow holding capacity topographic modification of wind speeds snow cover shear strength wind induced surface shear stress snow transport resulting from saltation and suspension snow accumulation and erosion and sublimation of the blowing and drifting snow the model simulates the cold season evolution of snow depth distribution when forced with inputs of vegetation type and topography and atmospheric foreings of air temperature humidity wind speed and direction and precipitation model outputs include the spatial and temporal evolution of snow depth resulting from variations in precipitation saltation and suspension transport and sublimation using 4 years of snow depth distribution observations from the foothills north of the brooks range in arctic alaska the model is found to simulate closely the observed snow depth distribution patterns and the interannual variability

snow distribution and melt modelling for glaciers in zackenberg river drainage basin north eastern greenland a physically based snow evolution modelling system snowmodel that includes four sub models micromet enbal snowpack and snowtran 3d was used to simulate eight full year evolutions of snow accumulation distribution sublimation and surface melt from glaciers in the zackenberg river drainage basin in north east greenland meteorological observations from two meteorological stations were used as model inputs and spatial snow depth observations snow melt depletion curves from photographic time lapse and a satellite image were used for model testing of snow and melt simulations which differ from previous snowmodel tests methods used on greenland glaciers modelled test period average end of winter snow water equivalent swe depth for the depletion area differs by a maximum of 14 mm w eq or 6 more than the observed and modelled test period average snow cover extent differs by a maximum of 5 or 0 8 km2 less than the observed furthermore comparison with a satellite image indicated a 7 discrepancy between observed and modelled snow cover extent for the entire drainage basin about 18 31 mm w eq of the solid precipitation was returned to the atmosphere by sublimation modelled mean annual snow melt and glacier ice melt for the glaciers in the zackenberg river drainage basin from 1997 through 2005 september august averaged 207 mm w eq year 1 and 1198 mm w eq year 1 respectively yielding a total averaging 1405 mm w eq year 1 total modelled mean annual surface melt varied from 960 mm w eq year 1 to 1989 mm w eq year 1 the surface melt period started between mid may and the beginning of june and lasted until mid september annual calculated runoff averaged 1487 mm w eq year 1 150 106 m3 1997 2005 with variations from 1031 mm w eq year 1 to 2051 mm w eq year 1 the model simulated a total glacier recession averaging 1347 mm w eq year 1 136 106 m3 1997 2005 which was almost equal to previous basin average hydrological water balance storage studies 244 mm w eq year 1 125 106 m3 1997 2003 copyright 2007 john wiley sons ltd

the mass balance of circum arctic glaciers and recent climate change the sum of winter accumulation and summer losses of mass from glaciers and ice sheets net surface mass balance varies with changing climate in the arctic glaciers and ice caps excluding the greenland ice sheet cover about 275 000 km2of both the widely glacierized archipelagos of the canadian norwegian and russian high arctic and the area north of about 60 n in alaska iceland and scandinavia since the 1940s surface mass balance time series of varying length have been acquired from more than 40 arctic ice caps and glaciers most arctic glaciers have experienced predominantly negative net surface mass balance over the past few decades there is no uniform recent trend in mass balance for the entire arctic although some regional trends occur examples are the increasingly negative mass balances for northern alaska due to higher summer temperatures and increasingly positive mass balances for maritime scandinavia and iceland due to increased winter precipitation the negative mass balance of most arctic glaciers may be a response to a step like warming in the early twentieth century at the termination of the cold little ice age arctic ice masses outside greenland are at present contributing about 0 13 mm yr 1to global sea level rise

the late antiquity environmental crisis in emilia region po river plain northern italy geoarchaeological evidence and paleoclimatic considerations abstract for about four decades in italy local scientific literature has occasionally dealt with fluvial avulsions suggesting they should be considered as genetically linked to a peculiar climatic worsening that occurred in the late 6th century ad the so called paul the deacon deluge research performed by the soprintendenza per i beni archeologici dell emilia romagna over the last few years has allowed better definition of the timing of a more articulated alluvial history mainly concerning the roman imperial age and late antiquity 1st 6th century ad the main stratigraphic details of fourteen selected archaeological excavation sites eleven recently surveyed and three reviewed from the literature performed in the cities of modena bologna and related surroundings have been summarized eleven 14 c dates ranging between the years 130 ad and 810 ad allowed us to chronologically delimit a first framework for the riverbed network behaviour during ancient times in the central part of the region the alluvial process appeared to be continuous throughout the time span examined the fan trench was the most sensitive reach of the river system it started to aggrade during the 4th century ad during the 5th century ad and probably after the end of the 6th century ad a number of avulsions occurred this indicates that the fluvial system was in a metastable equilibrium whose behavioural threshold was finally overcome hence the importance of the supposed year 589 ad crisis the deluge appears to be less than previously supposed the riverbed aggradation became evident immediately after the roman empire s economic and demographic crisis of the 3rd century ad and it was probably due to the loss of the land preservation systems in the mountain catchment areas the long duration of the aggradation phase suggests that more than one human settlement phase in the minor catchment areas and or a minor climatic worsening pulse probably occurred during the 5th century ad the starting of the aggradation also coincided with the end of the petit maclu 1 high level phase of the european lakes notwithstanding this the climate s role as a forcing co factor can still be hard to evaluate positively due to the lack of local proxy data

glacier recession and water resources in peru s cordillera blanca the tropical glaciers of the cordillera blanca peru are rapidly retreating resulting in complex impacts on the hydrology of the upper rio santa watershed the effect of this retreat on water resources is evaluated by analyzing historical and recent time series of daily discharge at nine measurement points using the mann kendall nonparametric statistical test the significance of trends in three hydrograph parameters was studied results are interpreted using synthetic time series generated from a hydrologic model that calculates hydrographs based on glacier retreat sequences the results suggest that seven of the nine study watersheds have probably crossed a critical transition point and now exhibit decreasing dry season discharge our results suggest also that once the glaciers completely melt annual discharge will be lower than present by 2 30 depending on the watershed the retreat influence on discharge will be more pronounced during the dry season than at other periods of the year at la balsa which measures discharge from the upper rio santa the glacier retreat could lead to a decrease in dry season average discharge of 30

surface mass balance of the greenland ice sheet from climate analysis data and accumulation runoff models we used surface climate fields from high resolution 0 56 0 56 european centre for medium range weather forecasts ecmwf operational analyses 1992 98 together with meteorological and glaciological models of snow accumulation and surface meltwater runoff retention to produce novel maps of greenland ice sheet gis net accumulation net runoff and surface mass balance smb we compared our runoff maps with similar scaled runoff melt minus refreezing maps based on passive microwave satellite data our gross spatial temporal patterns of runoff compared well with those from the satellite data although amounts of modelled runoff are likely too low mean accumulation was 0 287 0 307 m a 1 and mean runoff was 0 128 0 151 m a 1 averaged across the w abdalati t l mote gis mask corresponding mean smb was 0 159 0 156 m a 1 with considerable interannual variability standard deviation 0 11 m a 1 primarily due to variations in runoff considering best estimates of current iceberg calving overall the gis is probably currently losing mass our study shows great promise for meaningfully modelling smb based on forthcoming second generation ecmwf re analysis era 40 data and comparing the results with ongoing laser radar measurements of surface elevation this should help elucidate to what extent surface elevation changes are caused by short term smb variations or other factors e g ice dynamics

the alban hills and monti sabatini volcanic products used in ancient roman masonry italy an integrated stratigraphic archaeological environmental and geochemical approach abstract the rocks of alban hills and monti sabatini volcanoes central italy and their associated epiclastic deposits have been extensively used as building material in ancient rome from about viiith century bce to ivth century ce however the identification of the source areas of these rocks is difficult due to the lack of an integrated stratigraphic and geochemical analysis of the relationships between the two volcanic districts and to the alteration affecting the primary products as consequence of weathering and pedogenetic processes here a comprehensive upgraded stratigraphic and geochronological review of the two volcanic districts corroborated by new geochronological data for several eruptive units and altered deposits is presented coupled to a complete geochemical background achieved by means of newly determined major and trace element analyses for all the main eruptive units a study of the alteration processes of the primary products is also presented and the age of the main weathering and pedogenetic phases associated to quaternary climatic changes are also investigated the results are integrated with those from literature in order to construct discriminant diagrams based on selected trace elements and allow us to characterize the primary and altered volcanic deposits in the rome area distinguish products of different volcanic districts discuss the effects of different weathering processes on the mobility of some elements and provide a reference frame for the provenance of the volcanic materials employed in ancient roman masonry the interdisciplinary data set and results presented here provide groundwork for volcanological climate pedological and archaeological provenance studies

mobilization and redistribution of rees and thorium in a syenitic lateritic profile a mass balance study abstract ree th geochemistry and mineralogy have been studied in a lateritic profile derived from a syenite at akongo in sw cameroon ree and th mass balance calculations for the host rock minerals show that at least 70 of the lree s and 50 of the hrees are contained in allanite apatite titanite and epidote and at least 50 of the th is controlled by the same accessory minerals which represent about 2 wt of the unaltered syenite these accessory phases are destroyed during the first stages of weathering causing most of the rees and th to be rapidly released into the soil comparison of the variation in the zr ti and th content as a function of the apparent density of the different zones of the saprolite shows that th is the least mobile element the presence of secondary thorianite tho2 the etched surface on zircon grains and the presence of ti in secondary cerianite support this geochemical interpretation the concentration of thorium was therefore chosen as invariant relative to the concentration of the other elements especially the rees in mass balance calculations most of the rees are leached in the iron rich upper horizons loose nodular horizon iron crust and top of mottled clay horizon where the groundwater table moves saprolite and bottom of the mottled clay horizon the rees are fractionated and redistributed there is a juxtaposition of leached and accumulation zones with precipitation of lree aluminous hydrated phosphates this study supports the existence of two different cycles for the redistribution of elements in the soil 1 1 as dissolved ions in the saprolite horizon and 2 2 as individual particles in the upper part of the profile

estimate of the magnetic anisotropy effect on the archaeomagnetic inclination of ancient bricks abstract the magnetic fabric of 59 bricks coming from 5 ancient kilns has been studied by measuring the anisotropy of magnetic susceptibility ams and the anisotropy of isothermal airm anhysteretic aarm and thermal atrm remanent magnetization the bricks are characterized by a well developed magnetic fabric that matches their flat shape the shape of the anisotropy ellipsoids is in almost all cases oblate with the maximum and intermediate axes lying parallel to the large face of the brick and the minimum axis perpendicular to it the directions of the principal axes are almost the same irrespectively of the type of anisotropy measured whereas the degree of anisotropy of the airm aarm and atrm is much higher than the ams as the bricks lie horizontally within the kiln the planar magnetic fabric results in an inclination shallowing of the archaeomagnetic direction with respect to that of the earth s magnetic field at the time of their last cooling estimation of this effect on the grounds of atrm measurements yields a shallowing that varies from 4 to 10 for individual samples such inclination difference may significantly bias archeomagnetic dating for the case of the canosa late roman kiln it leads to a dating error of more than two centuries

below surface ice melt on the coastal antarctic ice sheet in the jutulgryta area of dronning maud land antarctica subsurface melting of the ice sheet has been observed the melting takes place during the summer months in blue ice areas under conditions of below freezing air and surface temperatures adjacent snow covered regions having the same meteorological and climatic conditions experience little or no subsurface melting to help explain and understand the observed melt rate differences in the blue ice and snow covered areas a physically based numerical model of the coupled atmosphere radiation snow and blue ice system has been developed the model comprises a heat transfer equation which includes a spectrally dependent solar radiation source term the penetration of radiation into the snow and blue ice depends on the solar radiation spectrum the surface albedo and the snow and blue ice grain sizes and densities in addition the model uses a complete surface energy balance to define the surface boundary conditions it is run over the full annual cycle simulating temperature profiles and melting and freezing quantities throughout the summer and winter seasons the model is driven and validated using field observations collected during the norwegian antarctic research expedition nare 1996 97 the simulations suggest that the observed differences between subsurface snow and blue ice melting can be explained largely by radiative and heat transfer interactions resulting from differences in albedo grain size and density between the two mediums

an anthropic soil transformation fingerprinted by rey patterns abstract this focus article deals intentionally with modern soil disturbance in situ this is of interest to archaeologists as after disturbances both short and long term pedogenesis re starts obliterating previous signs soil modifications induced by human activity may be linked to pedogenetic evidence for disturbance with archaeological evidence for the cultural activities we contrasted two 750 m 3 soil pedons an anthrosol and a kastanozem from which the anthrosol is derived using 77 descriptors of soil properties which have been utilized in archaeological studies pedo morphological routine laboratory biochemical metals and rare earth elements plus yttrium rey with the aim of identifying a group of descriptors able to sort the occurrence of human interventions but which one is more promising our findings indicate that by the use of rare earth spatial patterns it is possible to classify the occurrence of human interventions in the case of emplacement of new parent material in respect to bulk soil disturbance in situ

southern hemisphere origins of the 1976 climate shift 1 observations from the tropical pacific ocean identify an abrupt climate shift in 1976 with surface temperatures changing from cooler than normal to warmer than normal in the span of about 1 year model results show that this climate shift originates with subsurface temperature anomalies in the south tropical pacific ocean which propagate first to the western boundary then northward to the equator and finally eastward along the equator to 140 w where they rise to the surface the results suggest that changes in the north pacific respond to changes in the tropical pacific

implications of increased greenland surface melt under global warming scenarios ice sheet simulations abstract the greenland ice sheet is likely to make a faster contribution to sea level rise in a warming world than previously believed based on numerical modelling using a parameterization of recent results showing surface meltwater lubrication of ice flow zwally et al science 297 557 2002 218 documented correlation between increased ice velocity and increased surface melt as parameterized by positive degree days they argued that surface water is piped directly to the bed with little delay causing increased basal water pressures and basal sliding velocities an effect not included in recent greenland ice sheet models known to the authors using the pennsylvania state university university of chicago thermomechanical flowline model numerous simulations were conducted to test a wide range of parameter space linking surface melt with a new sliding law based on the zwally et al data under three different global warming scenarios 2 co2 4 co2 and 8 co2 comparisons to reconstructions generated with a traditional sliding parameterization illustrate an enhanced sensitivity of the ice sheet to surface warming resulting in higher ablation rates additional thinning and retreat of the margin and a reduction in ice volume leading to an increased contribution to global sea level rise

glacier change in western north america influences on hydrology geomorphic hazards and water quality the glaciers of western canada and the conterminous united states have dominantly retreated since the end of the little ice age lia in the nineteenth century although average rates of retreat varied from strong in the first half of the twentieth century with glaciers stabilizing or even advancing until 1980 and then resuming consistent recession this retreat has been accompanied by statistically detectable declines in late summer streamflow from glacier fed catchments over much of the study area although there is some geographical variation over recent decades glaciers in northwest bc and southwest yukon have lost mass dominantly by thinning with relatively low rates of terminal retreat and glacier fed streams in that region have experienced increasing flows in many valleys glacier retreat has produced geomorphic hazards including outburst floods from moraine dammed lakes mass failures from oversteepened valley walls and debris flows generated on moraines in addition to these hydrologic and geomorphic changes evidence is presented that glacier retreat will result in higher stream temperatures possibly transient increases in suspended sediment fluxes and concentrations and changes in water chemistry with climate projected to continue warming over the twenty first century current trends in hydrology geomorphology and water quality should continue with a range of implications for water resources availability and management and hydroecology particularly for cool and cold water species such as salmonids copyright 2008 john wiley sons ltd

material sources of the roman brick making industry in the i and ii century a d from regio ix regio xi and alpes cottiae abstract bricks fine pottery ceramic gears and tiles are among the human made objects routinely recovered in archaeological documentation sites associated with early civilizations can provide thousands of samples from a single excavation they come in endless varieties according to economic and social circumstances and as debris can last almost forever provide important clues about the past behaviours in human societies any information about the provenance of ceramics is highly valuable in archaeological analysis in the case of roman brick making the provenance and manufacture of clayey materials are usually interpreted only by studying stamps imprinted on the artefacts when available in this paper the making of bricks tiles and other ceramics for building purposes is investigated in relation to the possible sources of raw materials used for the industry the major questions to be solved relate to the sites from where the romans collected the raw materials the technologies they applied to make bricks and other clayey building materials and how far have they transported raw resources and final products i e mainly bricks and tiles after furnace treatments considering that a crucial point was the nearby availability of timber water and sandy soils without stones some achievements to classify artefacts with identical provenance have been obtained using the structural transformations induced in the material by thermal treatments of pottery comparisons have been made of the trace elements chemical composition in icp ms and some physical properties including magnetic vsm hysteresis loops and mineralogical features with xrd and ir analysis have been identified as proxies to elucidate the possible provenance of rough materials and appreciate the technologies used by the roman brick making industry

surface melt induced acceleration of greenland ice sheet flow ice flow at a location in the equilibrium zone of the west central greenland ice sheet accelerates above the midwinter average rate during periods of summer melting the near coincidence of the ice acceleration with the duration of surface melting followed by deceleration after the melting ceases indicates that glacial sliding is enhanced by rapid migration of surface meltwater to the ice bedrock interface interannual variations in the ice acceleration are correlated with variations in the intensity of the surface melting with larger increases accompanying higher amounts of summer melting the indicated coupling between surface melting and ice sheet flow provides a mechanism for rapid large scale dynamic responses of ice sheets to climate warming

climate science himalayan glaciers in the balance a measurement by satellite altimetry shows the himalayan glaciers to be losing mass at only moderate rates but raises broader questions about other methods for estimating mass balance see letter p 495

an energy balance model of lake ice evolution a physically based mathematical model of the coupled lake lake ice snow and atmosphere system is developed for studying terrestrial atmospheric interactions in high elevation and high latitude regions the ability to model lake ice freeze up break up total ice thickness and ice type offers the potential to describe the effects of climate change in these regions model output is validated against lake ice observations made during the winter of 1992 93 in glacier national park montana u s a the model is driven with observed daily atmospheric forcing of precipitation wind speed and air temperature in addition to simulating complete energy balance components over the annual cycle model output includes ice freeze up and break up dates and the end of season clear ice snow ice and total ice depths for two nearby lakes in glacier national park each in a different topographic setting modeled ice features are found to agree closely with the lake ice observations model simulations illustrate the key role that the wind component of the local climatic regime plays on the growth and decay of lake ice the wind speed affects both the surface temperature and the accumulation of snow on the lake ice surface higher snow accumulations on the lake ice depress the ice surface below the water line causing the snow to become saturated and leading to the formation of snow ice deposits in regions having higher wind speeds significantly less snow accumulates on the lake ice surface thus limiting snow ice formation the ice produced by these two different mechanisms has distinctly different optical and radiative properties and affects the monitoring of frozen lakes using remote sensing techniques

a new high resolution digital elevation model of greenland fully validated with airborne laser altimeter data a new digital elevation model of the greenland ice sheet and surrounding rock outcrops has been produced at 1 km postings from a comprehensive suite of satellite remote sensing and cartographic data sets height data over the ice sheet were mainly from ers 1 and geosat radar altimetry these data were corrected for a slope dependent bias that had been identified in a previous study the radar altimetry was supplemented with stereophotogrammetric data sets synthetic aperture radar interferometry and digitized cartographic maps over regions of bare rock and where gaps in the satellite altimeter coverage existed the data were interpolated onto a regular grid with a spacing of 1 km the accuracy of the resultant digital elevation model over the ice sheet was assessed using independent and spatially extensive measurements from an airborne laser altimeter that had an accuracy of between 10 and 12 cm in a comparison with the laser altimetry the digital elevation model was found to have a slope dependent accuracy ranging from 1 04 1 98 m to 0 06 14 33 m over the ice sheet for a slope range of 0 0 1 0 the mean accuracy over the whole ice sheet was 0 33 6 97 m over the bare rock areas the accuracy ranged from 20 to 200 m dependent on the data source available the new digital elevation model was used as an input data set for a positive degree day model of ablation the new elevation model was found to reduce ablation by only 2 compared with using an older 2 5 km resolution model which suggests that resolution induced errors in estimating ablation are no longer important

greenland ice sheet high elevation balance and peripheral thinning aircraft laser altimeter surveys over northern greenland in 1994 and 1999 have been coupled with previously reported data from southern greenland to analyze the recent mass balance of the greenland ice sheet above 2000 meters elevation the ice sheet is in balance on average but has some regions of local thickening or thinning thinning predominates at lower elevations with rates exceeding 1 meter per year close to the coast interpolation of our results between flight lines indicates a net loss of about 51 cubic kilometers of ice per year from the entire ice sheet sufficient to raise sea level by 0 13 millimeter per year approximately 7 of the observed rise

tropical glacier meltwater contribution to stream discharge a case study in the cordillera blanca peru original abstract discharge measurements climate observations and hydrochemical samples gathered monthly 1998 99 in the yanamarey and uruashraju glacier fed catchments of the cordillera blanca peru permit an analysis of the glacier meltwater contribution to stream flow these glacier catchments feed the rio santa which discharges into the pacific ocean based on a water balance computation glacier melt contributes an estimated 35 of the average discharge from the catchments for comparison a volumetric end member mixing model of oxygen isotopes shows glacier melt contributes 30 45 to the total annual discharge based on stream geochemistry discharge from the yanamarey glacier catchment provides 30 of the annual volume discharged from the querococha watershed which is 10 glacierized by analogy the larger rio santa watershed also 10 glacierized receives at least 12 of its annual discharge from melting glacier ice tributary watersheds to the rio santa with larger fractions of glacier cover have less variable runoff and enhanced discharge demonstrating that the glaciers effectively buffer stream discharge seasonally with continued glacier melting stream flow will likely become more variable and there will be less dry season runoff

numerical simulation of holocene depositional wedge in the southern po plain northern adriatic sea italy abstract in the last 10 kyr bp a coastal depositional wedge formed along the southern po plain margin shoreline regression accelerated abruptly in the iron age and especially in the last 2 kyr due to the increased woodland removal on the apennines the deposition of the holocene sedimentary wedge is simulated here along four coast tranversal transects using a finite element two dimension mathematical model the model was constrained using the present topographic surface the maximum flooding line of the holocene transgression architecture and texture of depositional wedge the location of coastlines aeolian dunes and ancient offshore delta sand the sediment volume required to calibrate the simulations along the sections ranges from about 165 000 870 000 m3 m 1 the maximum tectonic subsidence varies from 0 1 to 0 7 mm yr 1 the minimum sand amount required by the model to stop the accelerated erosion of the cervia beach is about five times the one employed in recent april 2002 recovery works

recent ice sheet growth in the interior of greenland a continuous data set of greenland ice sheet altimeter height from european remote sensing satellites ers 1 and ers 2 1992 to 2003 has been analyzed an increase of 6 4 0 2 centimeters per year cm year is found in the vast interior areas above 1500 meters in contrast to previous reports of high elevation balance below 1500 meters the elevation change rate is 2 0 0 9 cm year in qualitative agreement with reported thinning in the ice sheet margins averaged over the study area the increase is 5 4 0 2 cm year or 60 cm over 11 years or 54 cm when corrected for isostatic uplift winter elevation changes are shown to be linked to the north atlantic oscillation

greenland ice sheet increased coastal thinning repeated laser altimeter surveys and modelled snowfall summer melt show average ice loss from greenland between 1997 and 2003 was 80 12 km3 yr 1 compared to about 60 km3 yr 1 for 1993 4 1998 9 half of the increase was from higher summer melting with the rest caused by velocities of some glaciers exceeding those needed to balance upstream snow accumulation velocities of one large glacier almost doubled between 1997 and 2003 resulting in net loss from its drainage basin by about 20 km3 of ice between 2002 and 2003 copyright 2004 by the american geophysical union

hydrologic response of the greenland ice sheet the role of oceanographic warming the response of the greenland ice sheet to ongoing climate change remains an area of great uncertainty with most previous studies having concentrated on the contribution of the atmosphere to the ice mass balance signature here we systematically assess for the first time the influence of oceanographic changes on the ice sheet the first part of this assessment involves a statistical analysis and interpretation of the relative changes and variations in sea surface temperatures ssts and air temperatures around greenland for the period 1870 2007 this analysis is based on hadisst1 and reynolds oi v2 sst analyses in situ sst and deeper ocean temperature series surface air temperature records for key points located around the greenland coast and examination of atmospheric pressure and geopotential height from ncep ncar reanalysis second we carried out a novel sensitivity experiment in which ssts were perturbed as input to a regional climate model and document the resulting effects on simulated greenland climate and surface mass balance we conclude that sea surface ocean temperature forcing is not sufficient to strongly influence precipitation snow accumulation and melt runoff of the ice sheet additional evidence from meteorological reanalysis suggests that high greenland melt anomalies of summer 2007 are likely to have been primarily forced by anomalous advection of warm air masses over the ice sheet and to have therefore had a more remote atmospheric origin however there is a striking correspondence between ocean warming and dramatic accelerations and retreats of key greenland outlet glaciers in both southeast and southwest greenland during the late 1990s and early 2000s copyright 2008 john wiley sons ltd

meltwater flux and runoff modeling in the ablation area of jakobshavn isbrae west greenland the temporal variability in surface snow and glacier melt flux and runoff were investigated for the ablation area of lakobshavn isbrae west greenland high resolution meteorological observations both on and outside the greenland ice sheet gris were used as model input realistic descriptions of snow accumulation snow and glacier ice melt and runoff are essential to understand trends in ice sheet surface properties and processes snowmodel a physically based spatially distributed meteorological and snow evolution modeling system was used to simulate the temporal variability of lakobshavn isbrre accumulation and ablation processes for 2000 01 2006 07 winter snow depth observations and modis satellite derived summer melt observations were used for model validation of accumulation and ablation simulations agreed well with observed values simulated annual surface melt varied from as low as 3 83 x 10 sup 9 m sup 3 2001 02 to as high as 8 64 x 10 sup 9 m sup 3 2004 05 modeled surface melt occurred at elevations reaching 1 870 m a s l for 2004 05 while the equilibrium line altitude ela fluctuated from 990 to 1 210 m a s l during the simulation period the snowmodel meltwater retention and refreezing routines considerably reduce the amount of meltwater available as ice sheet runoff without these routines the lakobshavn surface runoff would be overestimated by anmore average of 80 from september october through may june no runoff events were simulated the modeled interannual runoff variability varied from 1 81 x 10 sup 9 m sup 3 2001 02 to 5 21 x 10 sup 9 m sup 3 2004 05 yielding a cumulative runoff at the jakobshavn glacier terminus of approx 2 25 m w eq to approx 4 5 m w eq respectively the average modeled lakobshavn runoff of approx 3 4 km sup 3 y sup 1 was merged with previous estimates of jakobshavn ice discharge to quantify the freshwater flux to illulissat icefiord for both runoff and ice discharge the average trends are similar indicating increasing insignificant influx of freshwater to the illulissat icefiord for the period 2000 01 2006 07 this study suggests that surface runoff forms a minor part of the overall jakobshavn freshwater flux to the fiord around 7 approx 3 4 km sup 3 y sup 1 of the average annual freshwater flux of approx 51 0 km sup 3 y sup 1 originates from the surface runoff less

mass loss on himalayan glacier endangers water resources 1 ice cores drilled from glaciers around the world generally contain horizons with elevated levels of beta radioactivity including 36 cl and 3 h associated with atmospheric thermonuclear bomb testing in the 1950s and 1960s ice cores collected in 2006 from naimona nyi glacier in the himalaya tibet lack these distinctive marker horizons suggesting no net accumulation of mass ice since at least 1950 naimona nyi is the highest glacier 6050 masl documented to be losing mass annually suggesting the possibility of similar mass loss on other high elevation glaciers in low and mid latitudes under a warmer earth scenario if climatic conditions dominating the mass balance of naimona nyi extend to other glaciers in the region the implications for water resources could be serious as these glaciers feed the headwaters of the indus ganges and brahmaputra rivers that sustain one of the world s most populous regions

measuring glacier surface temperatures with ground based thermal infrared imaging spatially distributed surface temperature is an important yet difficult to observe variable for physical glacier melt models we utilize ground based thermal infrared imagery to obtain spatially distributed surface temperature data for alpine glaciers the infrared images are used to investigate thermal microscale processes at the glacier surface such as the effect of surface cover type and the temperature gradient at the glacier margins on the glacier s temperature dynamics infrared images were collected at cuchillacocha glacier cordillera blanca peru on 23 25 june 2014 the infrared images were corrected based on ground truth points and local meteorological data for the control points the pearson s correlation coefficient between infrared and station temperatures was 0 95 the ground based infrared camera has the potential for greatly improving glacier energy budget studies and our research shows that it is critical to properly correct the thermal images to produce robust quantifiable data

instruments and methods simulating complex snow distributions in windy environments using snowtran 3d we present a generalized version of snowtran 3d version 2 0 that simulates wind related snow distributions over the range of topographic and climatic environments found globally this version includes three primary enhancements to the original liston and sturm 1998 model 1 an improved wind sub model 2 a two layer sub model describing the spatial and temporal evolution of friction velocity that must be exceeded to transport snow the threshold friction velocity and 3 implementation of a three dimensional equilibrium drift profile sub model that forces snowtran 3d snow accumulations to duplicate observed drift profiles these three sub models allow snowtran 3d to simulate snow transport processes in variable topography and different snow climates in addition snowtran 3d has been coupled to a high resolution spatially distributed meteorological model micromet to provide more realistic atmospheric forcing data micromet distributes data precipi tation wind speed and direction air temperature and relative humidity obtained from meteorological stations and or atmospheric models located within or near the simulation domain snowtran 3d has also been coupled to a spatially distributed energy and mass balance snow evolution modeling system snowmodel designed for application in any landscape and climate where snow is found snowtran 3d is typically run using temporal increments ranging from 1 hour to 1 day horizontal grid increments ranging from 1 to 100 m and time spans ranging from individual storms to entire snow seasons

acceleration of jakobshavn isbrae triggered by warm subsurface ocean waters observations over past decades show a sudden switch of jakobshavn isbrae a large outlet glacier feeding a deep ocean fjord on greenland s west coast from slow thickening to rapid thinning in 1997 this switch is associated with a doubling in glacier velocity hydrographic data show a concurrent sudden increase in subsurface ocean temperatures along the entire west coast of greenland suggesting that the changes in jakobshavn isbrae were triggered by the arrival of relatively warm water originating from the irminger sea observations over the past decades show a rapid acceleration of several outlet glaciers in greenland and antarctica1 one of the largest changes is a sudden switch of jakobshavn isbrae a large outlet glacier feeding a deep ocean fjord on greenland s west coast from slow thickening to rapid thinning2 in 1997 associated with a doubling in glacier velocity3 suggested explanations for the speed up of jakobshavn isbrae include increased lubrication of the ice bedrock interface as more meltwater has drained to the glacier bed during recent warmer summers4 and weakening and break up of the floating ice tongue that buttressed the glacier5 here we present hydrographic data that show a sudden increase in subsurface ocean temperature in 1997 along the entire west coast of greenland suggesting that the changes in jakobshavn isbrae were instead triggered by the arrival of relatively warm water originating from the irminger sea near iceland we trace these oceanic changes back to changes in the atmospheric circulation in the north atlantic region we conclude that the prediction of future rapid dynamic responses of other outlet glaciers to climate change will require an improved understanding of the effect of changes in regional ocean and atmosphere circulation on the delivery of warm subsurface waters to the periphery of the ice sheets

climatic warming glacier recession and runoff from alpine basins after the little ice age maximum records of discharge of rivers draining alpine basins with between 0 and 70 ice cover in the upper aare and rhone catchments switzerland for the period 1894 2006 have been examined together with climatic data for 1866 2006 with a view to assessing the effects on runoff from glacierized basins of climatic warming coupled with glacier recession following the little ice age maximum annual runoff from ice free basins reflects precipitation variations rising from minima between 1880 and 1910 to maxima between the late 1960s and early 1980s the more highly glacierized the basin the more runoff mimicked mean may september air temperature during two periods of warming runoff increased gradually from the 1900s rapidly in the 1940s before decreasing to the late 1970s rising runoff levels during the second warming period failed to exceed those attained during the first despite higher summer temperatures although temperatures continued to rise discharge from glacierized basins declined after reaching maxima in the late 1980s to early 1990s in the first warming period rising specific melt rates augmented by increasing precipitation opposed the impact of declining glacier area on runoff although melt continued to increase in the second period enhanced melting even in the exceptionally warm summer of 2003 appears to have been insufficient to offset reducing glacier surface area exposed to melt low or reducing levels of precipitation and increasing evaporation thus runoff from glacierized basins peaked in the late 1940s to early 1950s

remote sensing of greenland ice sheet using multispectral near infrared and visible radiances 1 we present the physical basis of and validate a new remote sensing algorithm that utilizes reflected visible and near infrared radiation to discriminate between dry and wet snow when applied to the moderate resolution imaging spectroradiometer modis satellite data our discrimination algorithm has the potential to retrieve melting regions of the ice sheet at a spatial resolution of 0 25 km 2 over three orders of magnitude higher than the resolution of current microwave methods the method should be useful for long term monitoring of the melt area of the greenland ice sheet especially regions close to ice sheet margins and of the outflow glaciers our analysis of modis retrievals of the western portion of the greenland ice sheet over the period 2000 to 2006 indicates significant interannual variability with a maximum melt extent in 2005 collocated in situ meteorological data reveal a high correlation 0 80 between the modis melt day area and the average summer temperature our analysis suggests that it is the magnitude of the summer temperature that dominates the melting not the variability of the length of the melting season furthermore we find that the melt day area increases by about 3 8 for each 0 1 k increase in the average surface air summer temperature we combine this empirical relationship with historic temperature data to infer that the melt day area of the western part of the ice sheet doubled between the mid 1990s and mid 2000s and that the largest ice sheet surface melting probably occurred between 1920s and 1930s concurrent with the warming in that period

mass balance of the greenland ice sheet from 1958 to 2007 we combine estimates of the surface mass balance smb of the greenland ice sheet for years 1958 to 2007 with measurements of the temporal variability in ice discharge d to deduce the total ice sheet mass balance during that time period we find a robust correlation r2 0 83 between anomalies in smb and in d which we use to reconstruct a continuous series of total ice sheet mass balance we find that the ice sheet was losing 110 70 gt yr in the 1960s 30 50 gt yr or near balance in the 1970s 1980s and 97 47 gt yr in 1996 increasing rapidly to 267 38 gt yr in 2007 multi year variations in ice discharge themselves related to variations in smb cause 60 20 more variation in total mass balance smb and therefore dominate the ice sheet mass budget copyright 2008 by the american geophysical union

continued evolution of jakobshavn isbrae following its rapid speedup 1 several new data sets reveal that thinning and speedup of jakobshavn isbrae continue following its recent rapid increase in speed as its floating ice tongue disintegrated the present speedup rate of 5 a 1 over much of the fast moving region appears to be a diffusive response to the initial much larger speedup near the front there is strong seasonality in speed over much of the fast flowing main trunk that shows a good inverse correlation with the seasonally varying length of a short typically 6 km floating ice tongue this modulation of speed with ice front position supports the hypothesis that the major speedup was caused by loss of the larger floating ice tongue from 1998 to 2003 analysis of image time series suggests that the transient winter ice tongue is formed when sea ice bonds glacier ice in the fjord to produce a nearly rigid mass that almost entirely suppresses calving major calving only resumes in late winter when much of this ice clears from the fjord the collapse of the ice tongue in the late 1990s followed almost immediately after a sharp decline in winter sea ice concentration in disko bay this decline may have extended the length of the calving season for several consecutive years leading to the ice tongue s collapse

seasonal variation in velocity before retreat of jakobshavn isbrae greenland 1 using repeat pass satellite feature tracking the dynamic behaviour of jakobshavn isbrae which drains around 7 of the greenland ice sheet is investigated in improved detail through its recent period of thinning acceleration and retreat the departure in 1995 from the normal seasonal invariance in velocity near the grounding line suggests a possible change in dynamics well before the subsequent thinning phase the initiation of the acceleration and retreat is pinpointed to spring 1998 and may have been prompted by the same mechanism that gave rise to the spring 1995 flow increase

detection of changes in glacial run off in alpine basins examples from north america the alps central asia and the andes atmospheric warming and enhanced melting of glaciers is already resulting in changes in the glacial contribution to run off in mountain basins around the world the enhanced melting of glaciers leads at first to increased run off and discharge peaks and an increased melt season while in the longer time frame glacier wasting can be so severe that it results in decreased run off glacier basins with a decreasing run off trend have been observed in south central british columbia at low elevations in the swiss alps and in the central andes of chile which is probably a combined effect of reduced melt from seasonal snow cover as the snow line rises and relevant glacier area losses in contrast significant run off increases are reported in alberta north western british columbia and yukon in canada in highly glacierized basins in the swiss and austrian alps the tianshan mountains and tibet in central asia and in the tropical andes of peru the run off increase within these basins is closely related to observed temperature rise indicating that there is an unequivocal signal of enhanced glacier melting under the present warming trends in future warming scenarios glacier run off should start to decrease even in high altitude basins affecting water availability copyright 2008 john wiley sons ltd

toward hydro social modeling merging human variables and the social sciences with climate glacier runoff models santa river peru summary glacier shrinkage caused by climate change is likely to trigger diminished and less consistent stream flow in glacier fed watersheds worldwide to understand model and adapt to these climate glacier water changes it is vital to integrate the analysis of both water availability the domain of hydrologists and water use the focus for social scientists drawn from a case study of the santa river watershed below peru s glaciated cordillera blanca mountain range this paper provides a holistic hydro social framework that identifies five major human variables critical to hydrological modeling because these forces have profoundly influenced water use over the last 60 years 1 political agendas and economic development 2 governance laws and institutions 3 technology and engineering 4 land and resource use and 5 societal responses notable shifts in santa river water use including major expansions in hydroelectricity generation large scale irrigation projects and other land and resource use practices did not necessarily stem from changing glacier runoff or hydrologic shifts but rather from these human variables ultimately then water usage is not predictable based on water availability alone glacier runoff conforms to certain expected trends predicted by models of progressively reduced glacier storage however societal forces establish the legal economic political cultural and social drivers that actually shape water usage patterns via human modification of watershed dynamics this hydro social framework has widespread implications for hydrological modeling in glaciated watersheds from the andes and alps to the himalaya and tien shan as well as for the development of climate change adaptation plans