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

characteristics of recessional moraines at a temperate glacier in se iceland insights into patterns rates and drivers of glacier retreat icelandic glaciers are sensitive to climate variability on short term timescales owing to their north atlantic maritime setting and have been undergoing ice marginal retreat since the mid 1990s recent patterns rates and drivers of ice frontal retreat at skalafellsjokull se iceland are examined using small scale recessional moraines as a geomorphological proxy these small scale recessional moraines exhibit distinctive sawtooth planform geometries and are constructed by a range of genetic processes associated with minor ice margin re advance including i combined push squeeze mechanisms ii bulldozing of pre existing proglacial material and iii submarginal freeze on remote sensing investigations and lichenometric dating highlight sequences of annually formed recessional moraines on the northern and central parts of the foreland conversely moraines are forming on a sub annual timescale at the southeastern skalafellsjokull margin using annual moraine spacing as a proxy for annual ice margin retreat rates imrrs we demonstrate that prominent periods of glacier retreat at skalafellsjokull are coincident with those at other icelandic outlet glaciers as well as those identified at greenlandic outlet glaciers analysis of imrrs and climate data suggests summer air temperature sea surface temperature and the north atlantic oscillation have an influence on imrrs at skalafellsjokull with the glacier appearing to be most sensitive to summer air temperature on the basis of further climate data analyses we hypothesise that sea surface temperature may drive air temperature changes in the north atlantic region which in turn forces imrrs the increase in sea surface temperature over recent decades may link to atmospheric driven variations in north atlantic subpolar gyre dynamics

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

relating glacier mass balance to meteorological data using a seasonal sensitivity characteristic we propose to quantify the climate sensitivity of the mean specific balance b of a glacier by a seasonal sensitivity characteristic ssc the ssc gives the dependence of b on monthly anomalies in temperature and precipitation it is calculated from a mass balance model we show and discuss examples for franz josef glacier new zealand nigardsbreen norway hintereisferner austria peyto glacier canadian rockies abramov glacier kirghizstan and white glacier canadian arctic with regard to the climate sensitivity of b the sscs clearly show that summer temperature is the most important factor for glaciers in a dry climate for glaciers in a wetter climate spring and fall temperatures also make a significant contribution to the overall sensitivity the ssc is a 2 12 matrix multiplying it with monthly perturbations of temperature and precipitation for a particular year yields an estimate of the balance for that year we show that with this technique mass balance series can be re constructed from long meteorological records or from output of atmospheric models

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

climate sensitivity of storglaciaren sweden an intercomparison of mass balance models using era 40 re analysis and regional climate model data estimates of glacier contributions to future sea level rise are often computed from mass balance sensitivities derived for a set of representative glaciers our purpose is to investigate how mass b

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

a reinterpretation of the data from the nasa stratosphere troposphere exchange project data obtained during the nasa stratosphere troposphere exchange project step mid latitude field experiment displayed laminae of ozone water and condensation nuclei in the stratosphere in association with a mid latitude stratosphere troposphere folding event danielsen et al 1991 constructed cross sections of these observations and interpreted these quasi horizontal laminae as evidence of ultra low frequency gravity waves we use a new technique to show that these laminae could have resulted from differential advection rather than transport by ultra low frequency gravity waves this new technique uses reverse domain filling back trajectories on multiple isentropic surfaces in conjunction with modified potential vorticity to reveal the qualitative details of the constituent laminae

ground motions induced by a producing hydrocarbon reservoir that is overlain by a viscoelastic rocksalt layer a numerical model hydrocarbon reservoir pressure depletion leads to stress changes inside the reservoir and ground deformation which is registered at the surface as subsidence as reservoirs are often overlain by layers of rocksalt or other evaporites which are materials that flow so as to relax stresses inside them there is the potential for time varying surface subsidence this work focuses on understanding the macroscopic mechanisms that lead to rocksalt flow induced ground displacements a finite element model is used for this purpose in which the rocksalt layer is represented by a viscoelastic maxwell material two distinct mechanisms that lead to displacement are observed these are active during different stages of the deformation and have different timescales associated with them an important observation is that the timescale for deformation that is measured at the ground surface is not equal to the timescale for deformation of a viscoelastic material element but can be many times larger than that the sensitivity of the response to the thickness and location of the rocksalt layer is also presented conclusions are drawn which allow for the relative importance of the presence of the rocksalt layer to be assessed and for a framework for understanding time dependent subsidence above producing hydrocarbon reservoirs to be developed finally the changes in stress distribution around a producing reservoir are also briefly discussed

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

spatial and temporal variability of air temperature on a melting glacier atmospheric controls extrapolation methods and their effect on melt modeling juncal norte glacier chile 1 temperature data from three automatic weather stations and twelve temperature loggers are used to investigate the spatiotemporal variability of temperature over a glacier its main atmospheric controls the suitability of extrapolation techniques and their effect on melt modeling we use data collected on juncal norte glacier central chile during one ablation season we examine temporal and spatial variability in lapse rates lrs together with alternative statistical interpolation methods the main control over the glacier thermal regime is the development of a katabatic boundary layer kbl katabatic wind occurs at night and in the morning and is eroded in the afternoon lrs reveal strong diurnal variability with steeper lrs during the day when the katabatic wind weakens and shallower lrs during the night and morning we suggest that temporally variable lrs should be used to account for the observed change they tend to be steeper than equivalent constant lrs and therefore result in a reduction in simulated melt compared to use of constant lrs when extrapolating from lower to higher elevations in addition to the temporal variability the temperature elevation relationship varies also in space differences are evident between local lrs and including such variability in melt modeling affects melt simulations extrapolation methods based on the spatial variability of the observations after removal of the elevation trend such as inverse distance weighting or kriging do not seem necessary for simulations of gridded temperature data over a glacier

langfjordjokelen a rapidly shrinking glacier in northern norway in this paper we document changes of langfjordjokelen a small ice cap in northern norway surface mass balance measurements have been carried out on an east facing part 3 2 km 2 o f the ice cap since 1989 measurements reveal a strong thinning the balance year 2008 09 was the 13th successive year with significant negative annual balance 0 30 m w e the average annual deficit was 0 9 m w e over 1989 2009 the recent thinning of langfjordjokelen is stronger than observed for any other glacier in mainland norway maps from 1966 1994 and 2008 show that the whole ice cap is shrinking the total volume loss over 1966 2008 was 0 264 km 3 the east facing part has been greatly reduced in volume 46 area 38 and length 20 for this part over 1994 2008 the cumulative direct mass balance 14 5 m w e is less negative than the geodetic mass balance 17 7 m w e a surface mass balance model using upper air meteorological data was used to reconstruct annual balances back to 1948 and to reconstruct unmeasured years 1994 and 1995 sensitivity of annual balance to 18c warming is 0 76 m w e and to 10 increase in precipitation is 0 20 m w e

sporteggbreen western norway in the past present and future simulations with a two dimensional dynamical glacier model a two dimensional shallow ice flow model yielding the glacier geometry at selected time intervals is used to simulate the development of sporteggbreen 1 from 8000 cal yr bp to the present 2 from ad 2011 to 2050 and 3 extending forward in time to ad 2100 and 2200 glacier surface geometry subglacial topography mass balance data internal deformation and subglacial sliding are used as input data for the model runs to force the model from 8000 cal yr bp to the present a mass balance series based on the equilibrium line altitude ela variations on jostedalsbreen to the west of sporteggbreen is applied a 50 reduction of the ela amplitude at jostedalsbreen is used to construct a new mass balance series and it was found that this gives a reasonably good coherence between the modelled and the real glacier the modelled time series for ela and length changes indicate that the glacier melted away c 7300 cal yr bp and was absent for c 1700 years it reformed c 5400 cal yr bp because of a mo

persistence of full glacial conditions in the central pacific until 15 000 years ago the magnitude of atmospheric cooling during the last glacial maximum and the timing of the transition into the current interglacial period remain poorly constrained in tropical regions partly because of a lack of suitable climate records glacial moraines provide a method of reconstructing past temperatures but they are relatively rare in the tropics here we present a reconstruction of atmospheric temperatures in the central pacific during the last deglaciation on the basis of cosmogenic 3he ages of moraines and numerical modelling of the ice cap on mauna kea volcano hawaii the only highland in the central pacific on which moraines that formed during the last glacial period are preserved our reconstruction indicates that the last glacial maximum occurred between 19 000 and 16 000 years ago in this region and that temperatures at high elevations were about 7 c lower than today during this interval glacial retreat began about 16 000 years ago but temperatures were still about 6 5 c lower than today until 15 000 years ago when combined with estimates of sea surface temperatures in the central pacific ocean our reconstruction indicates that the lapse rate during the last glacial maximum was higher than at present which is consistent with the proposal that the atmosphere was drier at that time furthermore the persistence of full glacial conditions until 15 000 years ago is consistent with the relatively late and abrupt transition to warmer temperatures in greenland5 indicating that there may have been an atmospheric teleconnection between the central pacific and north atlantic regions during the last deglaciation

comparison of mass balances for vernagtferner oetzal alps as obtained from direct measurements and distributed modeling the direct comparison of modeled glacier mass balance distribution with field measure ments could be problematic as the methodology of determination and the processes considered at the point or catchment scale could differ strongly moreover direct measurements cover only small parts of a glacier and model performance is thus difficult to assess outside these regions remaining opportunities for model validation include comparison of snowlines as derived from remote sensing data and maps of the mass balance distribution as interpreted by observers with local knowledge this study compares such hand drawn maps of the vernagtferner oetzal alps mass balance with the modeled pattern as obtained from a distributed energy mass balance model of intermediate complexity the model is driven by measured daily values of temperature global radiation and precipitation from a nearby climate station and grids of mean daily potential global radiation and climatologic annual precipitation sums compared with the direct measurements the calculated mean mass balance and equilibrium line altitude agreed very well in both balance years although the spatial pattern of the mass balance distribution displayed larger deviations in regions influenced by snowdrift or local topographic undulations however compared with the remaining snow as visible on a satellite image from 1999 the modeled snowline pattern for a larger sample of glaciers is in very good agreement

the influence of drainage boundaries on specific mass balance results a case study of engabreen norway mass balance measurements were initiated on engabreen an outlet glacier from the svartisen ice cap norway in 1970 the glacier boundary was defined based on where meltwater drained as the interest in engabreen was mainly hydrological however the apparent discrepancy between the calculated cumulative glacier mass balance since 1970 and changes in glacier geometry prompted a re examination of the glacier boundary the glaciological drainage boundary is defined by studying whether ice flow physically contributes to engabreen tongue and corresponds to a glacier with an area of 27 2 km 2 significantly smaller than that defined by the hydrological drainage boundary at 39 6 km 2 this glaciological drainage boundary is here named the ice flow perimeter the area difference between this and the hydrological drainage boundary is largest for the altitudinal range 1300 1400 m a s l generally the glaciological glacier is lower in mean altitude than the hydrological glacier and this affects the calculated specific mass balance using the glaciological boundary leads to reductions in mean annual winter and summer balance when spatial differences are ignored of 0 12 m w e from 2 92 to 2 80 m w e and 0 15 m w e from 2 32 to 2 47 m w e respectively the reduction in mean net balance for the period 1970 2006 is 0 27 m w e from 0 59 to 0 32 m w e which is about 50 of the calculated mass surplus in this period this illustrates that the choice of glacier outline can significantly influence the long term cumulative mass balance and that results from outlet glaciers must be interpreted with care when used for regional estimates of glacier change

filamentation and layering of an idealized tracer by observed winds in the lower stratosphere the isentropic transport of a passive tracer on synoptic time scales in the winter lower stratosphere is modelled with the use of a high resolution transport model which is forced by winds derived from global meteorological analyses the study has focused on a meteorological situation which occured in late january 1992 repeated poleward intrusions of mid latitude air are shown to lead to the filamentation of a tracer distribution which was initially compact and located inside the polar vortex the effect of wind resolution on the filamentation process is examined by performing isentropic advection on many closely spaced independent levels the vertical structure of these filaments can be studied

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

calibrating a surface mass balance model for austfonna ice cap svalbard austfonna 8120 km 2 is by far the largest ice mass in the svalbard archipelago there is considerable uncertainty about its current state of balance and its possible response to climate change over the 2004 05 period we collected continuous meteorological data series from the ice cap performed mass balance measurements using a network of stakes distributed across the ice cap and mapped the distribution of snow accumulation using ground penetrating radar along several profile lines these data are used to drive and test a model of the surface mass balance the spatial accumulation pattern was derived from the snow depth profiles using regression techniques and ablation was calculated using a temperature index approach model parameters were calibrated using the available field data parameter calibration was complicated by the fact that different parameter combinations yield equally acceptable matches to the stake data while the resulting calculated net mass balance differs considerably testing model results against multiple criteria is an efficient method to cope with non uniqueness in doing so a range of different data and observations was compared to several different aspects of the model results we find a systematic underestimation of net balance for parameter combinations that predict observed ice ablation which suggests that refreezing processes play an important role to represent these effects in the model a simple pmax approach was included in its formulation used as a diagnostic tool the model suggests that the surface mass balance for the period 29 april 2004 to 23 april 2005 was negative 318 mm w e

effects of digital elevation model spatial resolution on distributed calculations of solar radiation loading on a high arctic glacier high resolution airborne lidar data are used to produce digital elevation models dems of an arctic valley glacier midre lovenbreen svalbard at resolutions of 2 5 2000 m using three different interpolation schemes these data are used in a distributed model of solar radiation loading for glaciers when the mean of all lidar measurements within a dem cell is used to calculate cell height the differences between the finest 2 5 m and coarsest resolution 2000 m dems for the calculated annual whole glacier spatial means of total potential direct beam solar radiation potential duration of direct beam solar radiation and intensity of potential direct beam solar radiation are 20 56 and 23 of the 2 5 m dem values respectively a resolution change from 2 5 m to 200 m affects the whole glacier spatial mean summer net solar radiative flux by an average of 5 and the summer melt production from the glacier by an average of 3 compared with the 2 5 m dem values for the years 2001 03 these changes are largely driven by underestimation of shading by surrounding topography at coarser dem resolutions this dependency is reduced in the second and third interpolation schemes especially at resolutions finer than 50 m which use the maximum lidar height measurement in some or all dem cells these results suggest that resolutions of 50 m are the coarsest that should be adopted in high resolution glacier surface energy balance models for glaciers of similar size and in similar topographic situations to midre lovenbreen and that the impact of dem resolution on calculated solar radiation receipts can be reduced by an appropriate choice of dem interpolation scheme

lamination frequencies as a diagnostic for horizontal mixing in a 3d transport model ozone simulations are performed in an attempt to simulate laminar events with the frequency observed in balloon ozone sondes the winds are taken from the goddard earth observing system data assimilation system geos das the importance of horizontal and vertical resolution to production of lamina are investigated a simulation with a high horizontal reolution grid spacing 18 latitude by 1 258 longitude and high vertical resolution 300 m grid spacing isentropic model produces lamination frequencies close to the balloon sonde climatology near the polar vortex edge but exhibits too much lamination in the subtropics this indicates that the geos das winds contain the information to produce laminar events although such small scale features are not manifest in the more commonly used 28 latitude by 2 58 longitude transport model which uses the hybrid sigma pressure vertical coordinate the zonal average ozone tendencies due to horizontal mixing in the lamina producing models are similar to the tendencies in coarser resolution models that show no lamination suggesting that it is not necessary to resolve laminar events to maintain a realistic ozone budget the comparison of the modeled lamination frequency with the balloon sonde climatology indicates that the model horizontal mixing at the vortex edge is accurate but in the subtropics the mixing is excessive

measurements of polar vortex air in the midlatitudes the stratospheric photochemistry aerosols and dynamics expedition spade was conducted in the spring of 1993 from moffett field california nasa ames research center utilizing the nasa high altitude er 2 aircraft these northern midlatitude aircraft flights showed laminae containing high ozone concentrations traceable to the april 1993 polar vortex breakup and corroborated by laminae of other trace gases such as cfcs ch4 n2o and co2 these laminae are clearly traceable as polar vortex breakup fragments using rossby ertel s potential vorticity and isentropic trajectory calculations laminae in stratospheric ozone profiles are commonly observed in the northern hemisphere from fall to spring and are hypothesized to originate from very low frequency transverse waves and or via rossby wave breaking on the basis of these results the ozone laminae observed during spade were a result of rossby wave breaking during the breakdown of the polar vortex in addition it is shown that conventional once per day meteorological analyses were adequate for representing the transport of this material into the lower stratosphere midlatitudes over the course of the spring vortex breakup

impact of two conceptual precipitation downscaling schemes on mass balance modeling of gran campo nevado ice cap patagonia precipitation downscaling in mountainous regions with sparse station data is challenging but needed to link global climate datasets with high resolution glacier models in this study we apply a linear orographic precipitation model opm to generate orographic precipitation fields for mass balance studies at gran campo nevado gcn southern patagonia the opm is driven by large scale atmospheric input variables taken from the reanalysis data of the us national centers for environmental prediction and the us national center for atmospheric research the orographic precipitation fields are compared to precipitation fields assessed by a linear precipitation gradient widely used in earlier mass balance studies of gcn and elsewhere both downscaling methods are implemented into a degree day model to analyze the sensitivity of mass balance modeling to different precipitation inputs significant spatio temporal differences are found particularly in the summit region the mass balance modeling shows high sensitivity to the different precipitation distribution methods leading to differences in the mass balance gradients on the east side of gcn

tracer lamination in the stratosphere a global climatology vertical soundings of stratospheric ozone often exhibit laminated tracer structures characterized by strong vertical tracer gradients the change in time of these gradients is used to define a tracer lamination rate it is shown that this quantity can be calculated by the cross product of the horizontal temperature and horizontal tracer gradients a climatology based on uars satellite borne ozone data and on ozone like pseudotracer data is presented three stratospheric regions with high lamination rates were found the part of the stratospheric overworld which is influenced by the polar vortex the part of the lowermost stratosphere which is influenced by the tropopause and a third region in the subtropical lower stratosphere mainly characterized with strong vertical shear high lamination rates in the stratospheric overworld were absent during summer whereas in the lowermost stratosphere high lamination rates were found year round this is consistent with the occurrence and seasonal variation of the horizontal tracer gradient and vertical shear necessary for tilting the tracer surfaces during winter high lamination rates associated with the stratospheric polar vortex are present down to 100 hpa several features of the derived climatology are roughly consistent with earlier balloonborne studies the patterns in the southern and northern hemisphere are comparable but details differ as anticipated from a less disturbed and more symmetric southern polar vortex

rapid wastage of alaska glaciers and their contribution to rising sea level we have used airborne laser altimetry to estimate volume changes of 67 glaciers in alaska from the mid 1950s to the mid 1990s the average rate of thickness change of these glaciers was 0 52 m year extrapolation to all glaciers in alaska yields an estimated total annual volume change of 52 15 km 3 year water equivalent equivalent to a rise in sea level sle of 0 14 0 04 mm year repeat measurements of 28 glaciers from the mid 1990s to 2000 2001 suggest an increased average rate of thinning 1 8 m year this leads to an extrapolated annual volume loss from alaska glaciers equal to 96 35 km 3 year or 0 27 0 10 mm year sle during the past decade these recent losses are nearly double the estimated annual loss from the entire greenland ice sheet during the same time period and are much higher than previously published loss estimates for alaska glaciers they form the largest glaciological contribution to rising sea level yet measured

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

seasonal variation of isentropic transport out of the tropical stratosphere the seasonal variation of the isentropic transport out of the tropical stratosphere is examined using contour advection calculations with winds from meteorological analyses for the period july 1991 to june 1994 calculations using winds from three different meteorological analyses are compared there is good qualitative agreement between the different calculations for extratropical structures but not for structures in the tropics there is also reasonable agreement between area diagnostics for transport out of the tropics derived from these calculations transport out of the tropics occurs in rossby wave breaking events in which filaments of tropical air are drawn into middle latitudes in all years these wave breaking events occur during the fall to spring period when there are westerlies throughout middle latitudes late september to early may in the northern hemisphere this includes periods before the formation of and after the breakup of the polar vortex in the northern hemisphere the rate of transport out of the tropics during fall to spring fluctuates around a constant value whereas in the southern hemisphere there is a relatively quiet midwinter period with maxima in the transport in early and late winter