glacier subsurface heat flux characterizations for energy balance modelling in the donjek range southwest yukon canada we apply a point scale energy balance model to a small polythermal glacier in the st elias mountains of canada in order to investigate the applicability and limitations of different treatments of the glacier surface temperature and subsurface heat flux these treatments range in complexity from a multilayer subsurface model that simulates snowpack evolution to the assumption of a constant glacier surface temperature equal to 0 c the most sophisticated model includes dry densification of the snowpack penetration of shortwave radiation into the subsurface internal melting refreezing of percolating meltwater and generation of slush layers measurements of subsurface temperature and surface lowering are used for model validation and highlight the importance of including subsurface penetration of shortwave radiation in the model using an iterative scheme to solve for the subsurface heat flux as the residual of the energy balance equation results in an overestimation of total ablation by 18 while the multilayer subsurface model underestimates ablation by 6 by comparison the 0 c surface assumption leads to an overestimation of ablation of 29 in this study where the mean annual air temperature is about 8 c

tree ring evidence of little ice age glacier advances in southern tibet the history of late holocene glacier fluctuations in eastern tibet was studied by determining the ages of trees growing on glacier deposits maximum tree ages yield minimum ages of ad 1760 and 1780 for moraine formation at the maximum extent of the little ice age glacier advances in two glacier forefields subsequent moraines could be dated to the beginning of the nineteenth and the beginning of the twentieth century larch trees from a third glacier forefield in southeastern tibet show evidence of glacier activity from 1580 to 1590 from the end of the eighteenth to the beginning of the nineteenth century and from 1860 to 1880 one glacier at mt gyalaperi recently advanced in both 1951 and 1987 periods of glacier advances can partly be correlated with periods of growth reductions in chronologies of total ring width and maximum latewood density derived from trees growing on slopes above the glacier valleys correlation functions with meteorological data suggest that maximum latewood density of subalpin

on the temperature distribution of glaciers in china les mesures de temperature des differents types de glaciers en chine sont presentees la temperature de la base de la couche active etant comparee a la temperature atmospherique moyenne

dynamics of a small surge type glacier using one dimensional geophysical inversion we investigate the dynamics of a small surge type valley glacier as part of a study to characterize glacier response to climate in the donjek range southwest yukon canada pole displacements were measured using kinematic gps techniques during three consecutive summer field seasons measured surface velocities range from 10m a 1 over the lower 1500 m of the 5 km long glacier to a maximum of 25 35 m a 1 over the upper 3500 m basal velocities along an approximate flowline are reconstructed from the measured surface velocities using inverse methods control tests are used to validate the inversion scheme and sensitivity tests are performed to evaluate the influence of the flow law coefficient shape factor and longitudinal averaging length inversion of the real data shows that basal motion accounts for 50 100 of the total surface motion along the flowline based on these results and several other lines of evidence we suggest this glacier may be undergoing a slow surge

a 2 326 year tree ring record of climate variability on the northeastern qinghai tibetan plateau 1 high resolution climate proxy records covering the last two millennia on the qinghai tibetan plateau are scarce yet essential to evaluation of the patterns synchroneity and spatial extent of past climatic changes including those in the medieval warm period mwp and the little ice age lia here we present a 2326 year tree ring chronology of sabina przewalskii kom for dulan area of northeastern qinghai tibetan plateau we find that the annual growth rings mainly reflect variations in regional spring precipitation the greatest change in spring precipitation during the last two millennia seems to occur in the second half of the 4th century the north atlantic mwp was accompanied by notable wet springs in the study region during a d 929 1031 with the peak occurring around a d 974 three intervals of dry springs occurred in the period of lia our tree ring data will facilitate intercontinental comparisons of large scale synoptic climate variability for the last two millennia

light rings in subarctic conifers as a dendrochronological tool abstract light rings are characterized by one or a very few latewood cell layers an indication of shortened growing seasons and are particularly frequent in black spruce picea mariana mill bsp at the treeline in quebec the construction of a light ring chronology spanning the period ad 1398 1982 showed that the highest frequency 25 of light rings among 160 trees and krummholz occurred in 1593 1620 1634 1784 1816 1817 1853 1969 and 1972 these diagnostic rings be a useful cross dating tool for dendroecologists working with living and dead krummholz with a low growth variability about two thirds of the 65 light ring years coincide with years or triads of major volcanic eruptions the climatic conditions low temperature occurring at the end of the growing season in part induced by the climatic effect of volcanism seem to initiate light rings

internal accumulation on storglaciaren sweden in a multi layer snow model coupled to a distributed energy and mass balance model to investigate the internal accumulation on storglaciaren sweden we couple a multilayer snow model to a distributed energy and mass balance model the snow model describes the temperature density and water content evolution of the snow ice pack and includes the processes of percolation and refreezing of water the model is run for the period 9 may 2 september 1999 and validated against weather station and mass balance observations on the glacier the model performs reasonably well with an average summer mass balance for the location of stake observations of 1 56 m w e compared to 1 59 m w e observed however the amount of melt is overestimated in the higher parts of the accumulation area and underestimated in the lower parts of the ablation area the modelled mass balance is most sensitive to the albedo parameterization the chosen momentum and scalar roughness lengths and all parameters related to snowfall the modelled internal accumulation is 0 25 m w e which amounts to about 20 of the winter accumulation and results in a positive net balance for 1999 of 0 23 m w e the modelled internal accumulation is most sensitive to the initial subsurface temperature profile and the irreducible water content

areal melt and discharge modelling of storglaciaren sweden a grid based glacier melt and discharge model was applied to storglaciaren a small valley glacier 3 km 2 in northern sweden for the melt seasons of 1993 and 1994 the energy available for melt was estimated from a surface energy balance model using meteorological data collected by automatic weather stations on the glacier net radiation and the turbulent heat fluxes were calculated hourly for every grid point of a 30 m resolution digital terrain model using the measurements of temperature humidity wind speed and radiative fluxes on the glacier two different bulk approaches were used to calculate the turbulent fluxes and compared with respect to their impact on discharge simulations discharge of storglaciaren was simulated from calculated meltwater production and precipitation by three parallel linear reservoirs corresponding to the different storage properties of firn snow and ice the performance of the model was validated by comparing simulated discharge to measured discharge at the glacier snout depending on which parameterization of the turbulent fluxes was used the timing and magnitude of simulated discharge was in good agreement with observed discharge or simulated discharge was considerably underestimated in one year

irreducible water saturation in snow experimental results in a cold laboratory the porosity of wet snow is often about 50 however liquid water gen erally fills less than 10 of this pore volume in order to relate the irreducible water con tent trapped in snow to its characteristics we have conducted experiments in a cold laboratory the results show that water content expressed as per cent of mass depends only on porosity experimental studies were restricted to homogeneous wet snow samples therefore we can only achieve a valid result in natural snowpacks when apply ing to an homogeneous layer of wet snow nevertheless the results may be incorpor ated into snow cover energy balance models to improve the retention and percolation predic tions the thickness of the water saturated layer observed at the base of the sample in our experiments was related to the ratio of the mean convex radius of curvature to dry den sity

parameter uncertainty refreezing and surface energy balance modelling at austfonna ice cap svalbard 2004 08 we apply a physically based coupled surface energy balance and snowpack model to a site close to the equilibrium line on austfonna ice cap svalbard over the 2004 08 melt seasons to explain contributions to the energy available for melting and to quantify the significance of refreezing the model is forced using in situ meteorological measurements and precipitation downscaled from erainterim reanalysis applying a monte carlo approach to determine the tunable parameters of the model we estimate the uncertainty related to the choice of parameter values multiple criteria are evaluated to identify well performing parameter combinations evaluating the model performance with respect to longwave outgoing radiation snow and ice temperatures and surface displacement on average over the investigated melt seasons 1 june to 15 september net radiation and sensible heat contributed 90 2 and 10 2 respectively to the mean energy available for melting snow and ice the energy consumed by subsurface heat exchange reduced runoff by 15 2 in 2004 and 49 3 in 2008 refreezing of meltwater and rain was estimated to be 0 37 0 04mw e a 1on average over the five seasons which represents a considerable reduction of mass loss during summer our findings suggest that refreezing potentially exerts a decisive control on glacier mass balance in persistently snow or firncovered areas

rhyolitic glass in ordovician k bentonites a new stratigraphic tool fresh volcanic glasses in the form of melt inclusions within quartz phenocrysts are commonly present in paleozoic k bentonites from new york state iowa kentucky pennsylvania newfoundland and quebec because these glasses are compositionally distinct from one layerto another their geochemistry can be used to define chronostratigraphic horizons in new york state the k bentonites occur within flat lying calcareous black shales of the middle ordovician utica formation this glass has survived 1 because it has been sealed within a host crystal that is stable under most diagenetic conditions and 2 because of the modest burial depths the ordovician strata in this region to demonstrate the potential of these volcanic glasses for stratigraphic correlations isochronous surfaces have been established among three localities separated by 35 km the immaculate preservation of these ordovician glasses bodes well for the general application of this approach to younger and perhaps even older strata where geologic conditions have favored the survival of glass inclusions

surface roughness and bulk heat transfer on a glacier comparison with eddy correlation more than 100 simultaneously measured profiles of wind speed and temperature were analyzed to determine the aerodynamic and thermal roughness lengths of glacier ice the results proved to be extremely sensitive to measurement height which is difficult to define precisely on the hummocky terrain of a glacier therefore aerodynamic roughness lengths were estimated from the microtopography of the surface yielding 2 46 mm for ice and 5 5 mm for snow despite the indeterminate nature of the profile analysis it did support the view that the thermal roughness length must decrease as the roughness reynolds number increases a relationship which has been modelled in the literature good agreement between bulk transfer estimates and eddy correlation measurements of fhe sensible heat flux density on melting ice and snow was obtained by combining the aerodynamic roughness length with a suitable model for thermal roughness length

tree ring reconstruction of late summer temperatures in northern sikkim eastern himalayas abstract the sikkim region of the himalayas is among one of the most highly sensitive hotspots to climate change due to its fragile mountainous environment and rapidly growing population which exert significant impacts on regional ecosystem factors including biodiversity and hydrology limited observational data coverage in space and time for the high altitude mountainous region impedes our understanding of climate change and its impact on the environment in this paper we develop a 437 year tree ring width index chronology of tsuga dumosa d don eichler in northern sikkim as a climate proxy the substantial dendroclimatic potential of this proxy is evidenced in various statistics computed from the tree ring chronology an analysis of the tree ring chronology indicates a strong negative relationship between late summer mean temperatures july august september jas and tree growth this relationship enables us to reconstruct the jas mean temperature over northern sikkim since 1705 c e the 304 year 1705 2008 c e reconstructed temperature series shows similar warm and cool epochs which have been observed in many other temperature reconstructions in the region and other proxy records of glacial fluctuations an overall steady decreasing trend in the regional surface temperature is observed since 1705 c e while an increasing trend with intermittent short and cool epochs are noticed from 1850 c e to the present prior to the observational period before 1901 c e cold conditions x 1 prevailed during 1816 1819 1831 1837 1856 1859 and 1884 1887 c e with extremely cold conditions x 2 occurring in 1816 1817 1832 1833 1857 1877 1884 and 1885 c e warm conditions x 1 prevailed during 1713 1735 and 1823 1827 c e with extremely warm x 2 conditions occurring in 1724 1823 1824 and 1825 c e global teleconnections of the reconstructed temperature variations indicate the important roles of the pacific decadal oscillation pdo el nino southern oscillation enso and volcanic eruptions as drivers of temperature variations in the sikkim region of the himalayas

variations of ablation albedo and energy balance at the margin of the greenland ice sheet kronprins christian land eastern north greenland a meteorological and glaciological experiment was carried out in july 1993 at the margin of the greenland ice sheet in kronprins christian land eastern north greenland within a small area about 100 m 2 daily measurements were made on ten ablation stakes fixed in light and dark ice and were compared to each other simultaneously the components of the energy balance including net radiation sensible heat flux latent heat flux and conductive heat flux in the ice were determined global radiation longwave incoming radiation and albedo were measured and longwave outgoing radiation was calculated by assuming that the glacier surface was melting sensible and latent heat fluxes were calculated from air temperature humidity and wind speed conductive heat flux in the ice was estimated by temperature profile measurements in the uppermost ice layer net radiation is the major source of ablation energy and turbulent fluxes are smaller energy sources by about three times while heat flux into the ice is a substantial heat sink reducing energy available for ice melt albedo varies from 0 42 to 0 56 within the experimental site and causes relatively large differences in ablation at stakes close to each other small scale albedo variations should therefore be carefully sampled for large scale energy balance calculations

reconnaissance study of glacier energy balance in north greenland 1993 94 reconnaissance energy balance studies were made for the first time at two sites in north greenland to compare with conditions in west greenland the field expe e planned to save weight because it is expensive operate in north greenland the larger energy components incoming radiation and ablation were measured for 55 days altogether and the smaller components were evaluated by indirect methods c g turbulent fluxes are calculated from air temperature humidity and w ind speed to save the weight of inst ruments the energy balance model is tuned by choosing surface roughness and albedo to reduce the mean error between measured ablation and modelled daily melting the error standard deviation for ablation is only 5 kg m 2 d 1 which is much lower than found in west greenland due to better instruments and modelling in the presen study net radiation is the main energy source for melting in north greenland but ablation is is relatively low because sublimation and conductive heat fluxes use energy that would otherwise be available for melting there is a strong diurnal variation in ablation mainly forced by variations in shortwave radiation and reinforced by nocturnal cooling of the ice surface by outgoing longwave radiation and sublimation the model frequently predicts a frozen glacier surface at night even when air temperatures are positive

low sea level rise projections from mountain glaciers and icecaps under global warming the mean sea level has been projected to rise in the 21st century as a result of global warming such projections of sea level change depend on estimated future greenhouse emissions and on differing models but model average results from a mid range scenario a1b suggests a 0 387 m rise by 2100 refs 1 2 the largest contributions to sea level rise are estimated to come from thermal expansion 0 288 m and the melting of mountain glaciers and icecaps 0 106 m with smaller inputs from greenland 0 024 m and antarctica 0 074 m here we apply a melt model and a geometric volume model to our lower estimate of ice volume and assess the contribution of glaciers to sea level rise excluding those in greenland and antarctica we provide the first separate assessment of melt contributions from mountain glaciers and icecaps as well as an improved treatment of volume shrinkage we find that icecaps melt more slowly than mountain glaciers whose area declines rapidly in the 21st century making glaciers a limiting source for ice melt using two climate models we project sea level rise due to melting of mountain glaciers and icecaps to be 0 046 and 0 051 m by 2100 about half that of previous projections

cool north european summers and possible links to explosive volcanic eruptions 1 exactly dated tree ring measurements such as ring width trw and maximum latewood density mxd which are sensitive to summer temperatures can provide possible routes to investigate the occurrence of hemispheric wide cool summers that might be linked to explosive tropical volcanic eruptions these measurements can provide much longer records than the instrumental period enabling much longer periods to be assessed and offers the potential to look at much larger eruptions than recorded over the last 200 years this paper looks at trw evidence from northern fennoscandia extending over the last 7500 years using two independently produced chronologies from northern sweden and northern finland trw is less responsive than mxd to cool summer temperatures but mxd is only available for the last 2000 years additionally looking at a relatively small location compared to the northern hemisphere average adds considerable noise progress in this area is likely to be made by developing more millennial long trw series across northern high latitudes or being able to develop mxd series from the sub fossil material which comprises most of the samples prior to the last 1000 years the three most extreme negative values for the region for the last 2000 years are 1601 542 and 1837 although the latter is not extreme in a long instrumental record for the region the most extreme year of all occurred in 330bc of the 20 most extreme negative years nine occurred during the ad years with the remaining 11 occurring during the prior 5500 years

contribution of alaskan glaciers to sea level rise derived from satellite imagery over the last 50 years retreating glaciers and ice caps gic contributed 0 5 mm yr to sea level rises slr and one third is believed to originate from ice masses bordering the gulf of alaska however these estimates of ice wastage in alaska are based on methods that measure a limited number of glaciers and extrapolate the results to estimate ice loss for the many thousands of others how these methods capture the complex pattern of decadal elevation changes at the scale of individual glacier and mountain range is unclear here combining a comprehensive glacier inventory with elevation changes derived from sequential digital elevation models dems we found that between 1962 and 2006 alaskan glaciers lost 41 9 8 6 km 3 yr water equivalent w e and contributed 0 12 0 02 mm yr to slr our ice loss is 34 lower than previous estimates reasons for our lower values include the higher spatial resolution of our glacier inventory and the reduction of ice thinning under debris and at the glacier margins which were not resolved in earlier work estimates of mass loss from gic in other mountain regions could be subject to similar revisions

on the role of subsurface heat conduction in glacier energy balance modelling we discuss the inclusion of the subsurface heat conduction flux into the calculation of the energy balance and ablation at the glacier atmosphere interface data from automatic weather stations are used to force an energy balance model at several locations on alpine glaciers and at one site in the dry andes of central chile the heat conduction flux is computed using a two layer scheme assuming that 36 of the net shortwave radiation is absorbed by the surface layer and that the rest penetrates into the snowpack we compare simulations conducted with and without subsurface heat flux results show that assuming a surface temperature of zero degrees leads to a larger overestimation of melt at the sites in the accumulation area 10 4 13 3 than in the ablation area 0 5 2 8 due to lower air temperatures and the presence of snow the difference between simulations with and without heat conduction is also high at the beginning and end of the ablation season up to 29 for the first 15 days of the season when air temperatures are lower and snow covers the glacier surface while they are of little importance during periods of sustained melt at all the locations investigated

may september precipitation in the bhutan himalaya since 1743 as reconstructed from tree ring cellulose δ18o 1 we developed a 50 year tree ring 18o chronology for each of three tree species juniperus indica larix griffithii and picea spinulosa using a total of 12 trees four trees per species from the bhutan himalaya despite originating from different species sampled at two different altitudes the 18o chronologies are highly correlated with one another r 0 76 0 89 response analyses reveal that tree ring 18o values are controlled mainly by summer precipitation irrespective of species based on these results a robust 269 year 18o chronology was established to reconstruct the amount of may september precipitation based on data from four larch trees our tree ring 18o data show significant correlations with those from other regions of the himalaya and the tibetan plateau indicating that common signals related to monsoon activity are recorded in the data however at centennial timescales our data from bhutan show normal conditions during the 20th century whereas records from sites in western nepal and the southern eastern tibetan plateau show weakening trends in monsoon intensity during the last 100 200 years the weakening trends may be the result of a reduction in the meridional sea surface temperature gradient in the indian ocean during this time at continental scales the tree ring records show that areas more from ocean basins are particularly sensitive to reduced monsoon circulation correlation analyses suggest that the el nino southern oscillation enso plays an important role in modulating summer precipitation however the teleconnected relationship disappears during the period 1951 1970 coinciding with a negative phase of the pacific decadal oscillation pdo implying interdecadal modulation of the pdo on the influence of the enso on precipitation in bhutan

model study of the spatial distribution of the energy and mass balance of morteratschgletscher switzerland to investigate the spatial distribution of the energy and mass balance fluxes of a glacier a two dimensional mass balance model was developed and applied to morteratschgletscher switzerland the model is driven by meteorological input from four synoptic weather stations located in the vicinity of morteratschgletscher the model results were compared to observations made on the glacier the calculated mean specific mass balance is 0 47 m w e for 1999 and 0 23 m w e for 2000 net shortwave radiation shows a minimum at around 3350 m a s l due to the effects of shading slope aspect reflection from the slopes and obstruction of the sky ignoring these effects results in a 37 increase in the annual incoming shortwave radiation on the glacier causing 0 34 m w e more ablation a 1 c change in the air temperature results in a shift of 0 67 m w e in the mean specific mass balance while altering the precipitation by 10 causes a change of 0 17 m w e

analysis of meteorological data and the surface energy balance of mccall glacier alaska usa we report on analysis of meteorological data for the period 27 may 20 august 2004 from two automatic weather stations on mccall glacier alaska usa aimed at studying the relationship between climate and ablation one station is located on a mountain ridge and the other in the ablation area where we also analyzed the energy balance the weather station on the glacier measured an average temperature of 5 38c at 2m height above surface and wind speed of 3 1ms 1 at 3m height a sonic height ranger and ablation stakes indicate a specific mass balance of 1 94 0 09mw e between 15 june and 20 august the specific mass balance calculated from the surface energy balance 2 06 0 18mw e is in close correspondence to this the latter is the sum of 0 12mw e of snowfall 0 003mw e of deposition and 2 18mw e of melt net radiation contributes 74 of the melt energy compared to ablation measurements in the early 1970s summer ablation was large this increase is explained by a combination of a relatively higher net radiation a lower albedo and larger turbulent heat fluxes that led to more energy being available for melting no single meteorological variable can be isolated as being the principal reason for the high ablation however the lower ice albedo 0 19 is possibly due to ash deposits from forest fires

tree ring recorded may august temperature variations since a d 1585 in the gaoligong mountains southeastern tibetan plateau abstract high resolution proxy data are still scarce in the southeastern tibetan plateau which limit our understanding of climatic variability before instrumental records in this study we developed 595 year tree ring width chronology from larix speciosa near the timberlines of the gaoligong mountains southeastern tibetan plateau ring width site chronologies and a well replicated regional chronology rc showed significant positive correlations with warm season temperatures from may to august using rc as predictor we reconstructed mean may august temperature for the study region that extends back to a d 1585 cold conditions prevailed during the periods 1600s 1620 30 1640 50s 1700s 1730 40s 1760s 1810 20s 1850s 1900 10s and 1955 70 warm episodes occurred during 1610s 1660 1680s 1710 20s 1750s 1780 90s 1820 40 1920 50 and 1980 present spatial correlations with gridded land surface temperatures revealed that our reconstruction represents regional temperature signal for the southern tibetan plateau comparison with other tree ring based temperature reconstructions from surrounding areas implies a high degree of confidence for our reconstruction

a distributed surface energy balance model for a small valley glacier i development and testing for haut glacier d arolla valais switzerland this paper describes the development and testing of a distributed surface energy balance model used to calculate rates of surface melting at haut glacier d arolla valais switzerland the model uses a digital elevation model dem of the glacier surface and surrounding topography together with meteorological data collected at a site in front of the glacier to determine hourly or daily totals of the energy balance components and hence of melting over the entire surface of the glacier with a spatial resolutio of 20 m the model can also be used to determine temporal and spatial variations in snow depth snow line position and glacier surface albedo calculations from the model are compared with observations made along the glacier centre line in 1990 and in general the model performs very well the correlation coefficients between calculated and measured snow line elevation albedo and ablation are 0 99 0 85 and 0 81 respectively the main source of error between modelled and measured values of these variables is probably inadequacies in the parameterization of albedo used in the model

ice core evidence for an explosive tropical volcanic eruption 6 years preceding tambora high resolution analyses of ice cores from antarctica and greenland reveal an explosive volcanic eruption in the tropics in a d 1809 which is not reflected in the historical record a comparison in the same ice cores of the sulfate flux from the a d 1809 eruption to that from the tambora eruption a d 1815 indicates a near equatorial location and a magnitude roughly half that of tambora thus this event should be considered comparable to other eruptions producing large volumes ofsulfur rich gases such as coseguina krakatau agung and el chichtn the increase in the atmospheric concentration of sulfuric acid may have contributed to the northern hemisphere cooling observed in the early nineteenth century and may account partially for the decline in surface temperatures which preceded the eruption of tamborn in a d 1815

summer cooling driven by large volcanic eruptions over the tibetan plateau abstractlarge volcanic eruptions may cause abrupt summer cooling over large parts of the globe however no comparable imprint has been found on the tibetan plateau tp here we introduce a 400 y

three centuries of winter temperature change on the southeastern tibetan plateau and its relationship with the atlantic multidecadal oscillation long term high resolution proxy records containing cold season temperature signals are scarce on the southeastern tibetan plateau tp limiting our understanding of regional climate and the potential driving forces in this study we present a nearly three centuries long reconstruction of winter december february mean temperature for the central hengduan mountains southeastern tp the reconstruction is derived from a composite tree ring width chronology of pinus yunnanensis franch from two high elevation sites 3000 m above sea level our reconstruction passes all standard calibration verification schemes and explains nearly 73 of the variance of the original instrumental data however we were constrained to calibrate our full period 1718 2013 reconstruction of december february mean temperature on the calibration period from 1959 to 1992 only due to a decrease in temperature sensitivity of tree ring index exhibited after 1992 spatial correlation analysis shows that our reconstruction represents large scale temperature variations in southwest china and the eastern tp our reconstructed december february mean temperature shows a close association with the atlantic multidecadal oscillation amo over the past three centuries with warm cold periods coinciding with the positive negative phases of the amo this persistent relationship suggests that the amo may have been a key driver of multidecadal winter temperature variations on the southeastern tp

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

early palaeozoic brachiopods and associated shelly faunas from western gondwana their bearing on the geodynamic history of the pre andean margin

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

tree ring density inferred late summer temperature variability over the past three centuries in the gaoligong mountains southeastern tibetan plateau long and high resolution proxy records are still sparse in the southeastern tibetan plateau tp hampering our understanding of past climatic variability from a long term perspective in this study we developed a regional maximum latewood density mxd chronology of larix speciosa stretching up to 523 years based on 72 tree ring cores 44 trees collected from three sites close to the tree line in the gaoligong mountains southeastern tp this chronology responded well to temperatures during august through september and was thus used to reconstruct late summer august september temperature over the period a d 1690 2008 the reconstruction explains 40 9 of the total temperature variance during the calibration phase cold conditions prevailed during the periods 1695 1702 1806 1821 the 1850s 1882 1889 the 1900s and the 1960s warm phases occurred in 1734 1745 the 1770s 1824 1840 the 1890s 1927 1936 the 1940s 1950s and 2002 2008 spatial correlation with the gridded temperature data set showed that our reconstruction captures large scale regional temperature variations for the southeastern and southern tp comparison with other tree ring inferred temperature time series in the surrounding areas glacier fluctuations and historical documental records imply a high degree of confidence for our reconstruction c 2015 elsevier b v all rights reserved

the thermal conductivity of seasonal snow twenty seven studies on the thermal conductivity of snow k eff have been published since 1886 combined they comprise 354 values of k eff and have been used to derive over 13 regression equation and predicting k eff vs density due to large and largely undocumented differences in measurement methods and accuracy sample temperature and snow type it is not possible to know what part of the variability in this data set is the result of snow microstructure we present a new data set containing 488 measurements for which the temperature type and measurement accuracy are known a quadratic equation where is in g cm 3 and k eff is in w m 1 k 1 can be fit to the new data r 2 0 79 a logarithmic expression can also be used the first regression is better when estimating values beyond the limits of the data the second when estimating values for low density snow within the data set snow types resulting from kinetic growth show density independent behavior rounded grain and wind blown snow show strong density dependence the new data set has a higher mean value of density but a lower mean value of thermal conductivity than the old set this shift is attributed to differences in snow types and sample temperatures in the sets using both data sets we show that there are well defined limits to the geometric configurations that natural seasonal snow can take

comparison of thermal structure and evolution between neighboring subarctic glaciers 1 the distribution of cold and temperate ice within glaciers and ice sheets affects processes relevant to englacial and basal hydrology sliding and material rheology thermal regimes in turn are shaped by glacier and ice sheet dynamics as well as environmental setting we investigate the thermal structures of two small 7 km2 neighboring glaciers in the st elias mountains of southwestern yukon canada using ice penetrating radar and borehole temperature measurements our data reveal polythermal regimes in both glaciers that are strongly influenced by accumulation zone meltwater entrapment suggesting a climatic control on thermal structure differences in hypsometry and glacier dynamics nevertheless result in observed variations in the distribution of temperate ice between the two sites experiments with a thermomechanically coupled flow band model corroborate the strong control of meltwater entrapment on thermal structure and suggest a generally minimal role for strain heating an exception to this occurs where localized basal sliding produces lateral shearing and thus enhanced heat generation time dependent model simulations suggest that the future thermal evolution of the two glaciers may differ and therefore simple parameterizations of thermal response based on regional climate may not capture realistic variability between individual glaciers despite these differences both glaciers are ultimately expected to become fully cold prior to disappearing under negative mass balance conditions

an energy and mass model of snow cover suitable for operational avalanche forecasting a numerical model has been developed to simulate energy and mass evolution of snow cover at a given location as a function of meteorological conditions precipitation air temperature humidity wind velocity and incoming short wave and long wave radiation this model named crocus was first tested on a well instrumented field during a whole winter showing its ability to simulate the important phenomena affecting the evolution of the snow layers high temperature gradients wetting compaction and melting freezing cycles a second test was conducted at two locations in the french network used for operational avalanche forecasting though the weather observations are made there only twice daily the snow profiles calculated by the model were very close to those obtained once a week by a pit observation crocus proved itself sufficient to be considered now as a useful objective tool for operational avalanche forecasting

tree ring density based warm season temperature reconstruction since a d 1610 in the eastern tibetan plateau tree ring samples from purple cone spruce picea purpurea were collected at four sites on the eastern tibetan plateau maximum latewood density mxd was measured by x ray densitometry and a regional standard chronology was established from the four mxd chronologies using the regional curve standardization rcs method based on significant correlation between the regional rcs chronology and mean april september temperature warm season april september temperature variability was reconstructed back to 1610 for the eastern tibetan plateau the reconstruction explained 58 5 of the variance in the instrumental period 1961 to 2009 in the past 400 years there were five cold periods with lower than average and four warm periods with higher than average the temperature reconstruction captured the unprecedented warming in the 20th century where the last ten years were the warmest decade in the last 400 years the ensemble empirical mode decomposition eemd was used to extract the multi scale fluctuation of the temperature reconstruction four quasi oscillations with periodicities of 2 2 2 7 years 5 1 7 9 years 11 9 15 4 years and 21 8 26 2 years indicated major fluctuations of original temperature agreement with other temperature proxies implied a high degree of confidence for our reconstruction and its large scale spatial representation the temperature reconstruction showed a warming trend on a longer time scale in the eastern tibetan plateau c 2015 elsevier b v all rights reserved

vapor transport grain growth and depth hoar development in the subarctic snow measurements from the subarctic snowpack are used to explore the relationship between grain growth and vapor flow the fundamental processes of dry snow metamorphism due to extreme temperature gradients the subarctic pack undergoes extensive depth hoar metamorphism by the end of the winter a five layered structure with a pronounced weak layer near the base of the snow evolves grain size increases by a factor of 2 3 while the number of grains per unit mass decreases by a factor of 10 observed growth rates require significant net inter particle vapor fluxes stable isotope ratios show that there are also significant net layer to layer vapor fluxes soil moisture enters the base of the pack and mixes with the bottom 10 cm of snow while isotopically light water vapor fractionates from the basal layer and is deposited up to 50 cm higher in the pack end of winter density profiles for snow on the ground compared with snow on tables indicate the net layer to layer vapor flux averages 6 x 10 7 kg m 2 s 1 though detailed measurements show the net flux is episodic and varies with time and height in the pack with peak net fluxes ten times higher than average a model driven by observed temperature profiles reproduces the layer to layer flux pattern and predicts the observed weak layer at the base of the snow calculated layer to layer vapor fluxes are ten times higher than inter particle fluxes which implies that depth hoar grain growth is limited by factors other than the vapor supply this finding suggests that gain and loss of water molecules due to sublimation from grains takes place at a rate many times higher than the rate at which grains grow and it explains why grains can metamorphose into different forms so readily

spatial and temporal transferability of a distributed energy balance glacier melt model abstract modeling melt from glaciers is crucial to assessing regional hydrology and eustatic sea level rise the transferability of such models in space and time has been widely assumed but rarely tested to investigate melt model transferability a distributed energy balance melt model debm is applied to two small glaciers of opposing aspects that are 10 km apart in the donjek range of the st elias mountains yukon territory canada an analysis is conducted in four stages to assess the transferability of the debm in space and time 1 locally derived model parameter values and meteorological forcing variables are used to assess model skill 2 model parameter values are transferred between glacier sites and between years of study 3 measured meteorological forcing variables are transferred between glaciers using locally derived parameter values 4 both model parameter values and measured meteorological forcing variables are transferred from one glacier site to the other treating the second glacier

supraglacial weathering crust dynamics inferred from cryoconite hole hydrology water levels in cryoconite holes were monitored at high resolution over a 3 week period on austre broggerbreen svalbard these data were combined with melt and energy balance modelling providing insights into the evolution of the glacier s near surface hydrology and confirming that the hydrology of the near surface porous ice known as the weathering crust is dynamic and analogous to a shallow perched aquifer a positive correlation between radiative forcing of melt and drainage efficiency was found within the weathering crust this likely resulted from diurnal contraction and dilation of interstitial pore spaces driven by variations in radiative and turbulent fluxes in the surface energy balance occasionally causing sudden drainage events a linear decrease in water levels in cryoconite holes was also observed and attributed to cumulative increases in near surface ice porosity over the measurement period the transport of particulate matter and microbes between cryoconite holes through the porous weathering crust is shown to be dependent upon weathering crust hydraulics and particle size cryoconite holes therefore yield an indication of the hydrological dynamics of the weathering crust and provide long term storage loci for cryoconite at the glacier surface this study highlights the importance of the weathering crust as a crucial component of the hydrology ecology and biogeochemistry of the glacier ecosystem and glacierized regions and demonstrates the utility of cryoconite holes as natural piezometers on glacier surfaces

changes of climate glaciers and runoff in china s monsoonal temperate glacier region during the last several decades changes of climate glaciers and runoff during the last several decades in china s monsoonal temperate glacier region have been studied temperature has increased in a fluctuating manner during the last several decades and temperature rise has accelerated since the 1980s net accumulation of dasuopu ice core has consistently declined and the precipitation decrease was also obvious from the end of 1970s through the middle 1980s and particularly after the 1990s in china s monsoonal temperate glacier region as a response to climate change eight monsoonal temperate glaciers were stationary or advancing between the 1900s 1930s and the 1960s 1980s and were in retreat from the 1930s to the 1960s and from the 1980s to the present ablation is heavy in the glacier tongue areas and the mean ablation water equivalent in hailuogou glacier during 1990 91 1997 98 was 876 mm more than that in 1982 83 ablation depth on the exposed ice area increased by 1 4 m a 1 over the period 1983 84 1990 91 mass balance records also show that glaciers suffered a constant mass loss of snow and ice and the accumulated mass balance in hailuogou basin and baishui glacier no 1 was 10 83 m water equivalent in the past 45 years and 11 38 m in the past 52 years as glaciers become shorter narrower and thinner under the background of climate warming changes of internal and upper surface morphology also occurred providing evidence of the response to climatic warming in recent years local hydrological and climatic data demonstrated that in yanggong basin during 1979 2003 and hailuogou basin during 1988 2004 runoff from the glacier areas has been increasing both seasonally and annually overall it is clear that china s monsoonal temperate glaciers are losing mass and are retreating under the background of climate warming c 2009 elsevier ltd and inqua all rights reserved

a distributed surface energy balance model for complex topography and its application to storglaciaren sweden a grid based surface energy balance mass balance model has been developed to simulate snow and ice melt in mountainous regions with an hourly resolution the model is applied to storglaciaren a valley glacier in sweden using a 30 m resolution digital elevation model emphasis is directed towards computing the radiation components these are modelled individually considering the effects of slope angle aspect and effective horizon a new parameterization for snow albedo is suggested modifying the albedo of the preceding hour as a function of time after snowfall air temperature and cloudiness the model is used to provide the meltwater input for discharge modelling and to assess the influence of the individual components on melt results are validated by means of observed melt rates patterns of snow line retreat and proglacial discharge in general simulations are in good agreement with observations in particular the diurnal and seasonal fluctuations of discharge are simulated remarkably well

august temperature variability in the southeastern tibetan plateau since ad 1385 inferred from tree rings long term high resolution climate proxies are essential for understanding climate variability on the tibetan plateau tp where few long term climate records are available in this paper we describe a summer august temperature reconstruction over the period 1385 2002 based on a tree ring width chronology of balfour spruce picea likiangensis var balfouriana on the southeastern tp created using the regional curve standardization method the reconstruction explains 44 7 of the variance in the instrumental temperature records during the calibration period 1962 2002 and captures temperature variability over a broad region of the tp warmer than average augusts were found during the periods 1446 1494 1509 1522 1553 1567 1797 1812 1845 1905 and 1918 2002 cooler than average augusts occurred from 1385 1416 1426 1445 1495 1508 1523 1552 1568 1686 1695 1718 1725 1796 1813 1844 and 1906 1917 a warming trend in the 20th century was unprecedented during the past six centuries the reconstruction closely matched other tree ring summer temperature reconstructions from neighboring regions as well as patterns from ice core delta 18 o data and fluctuated in synchrony with northern hemisphere temperature reconstructions c 2011 elsevier b v all rights reserved

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 argentine precordillera its odyssey from the laurentian ouachita margin towards the sierras pampeanas of gondwana

enso signal in continental temperature and precipitation records warm events in the tropical pacific ocean associated with one extreme of the southern oscillation generally known as el nino southern oscillation or enso events are now known to be of global significance in perturbing the general circulation of the atmosphere1 8 it is also apparent that episodes of enhanced cold water upwelling cold events have an impact on large scale atmospheric circulation patterns9 11 here we examine the effect of warm and cold events on short term fluctuations of continental surface air temperature and precipitation throughout the northern hemisphere using a newly compiled set of high quality temperature and precipitation data12 13 the data were in the form of gridded anomalies from a 1951 70 reference mean for temperature and a 1921 60 reference mean for precipitation13 14

on the weakening relationship between the indian monsoon and enso analysis of the 140 year historical record suggests that the inverse relationship between the el nino southern oscillation enso and the indian summer monsoon weak monsoon arising from warm enso event has broken down in recent decades two possible reasons emerge from the analyses a southeastward shift in the walker circulation anomalies associated with enso events may lead to a reduced subsidence over the indian region thus favoring normal monsoon conditions additionally increased surface temperatures over eurasia in winter and spring which are a part of the midlatitude continental warming trend may favor the enhanced land ocean thermal gradient conducive to a strong monsoon these observations raise the possibility that the eurasian warming in recent decades helps to sustain the monsoon rainfall at a normal level despite strong enso events

seasonal and interannual variations of firn densification and ice sheet surface elevation at the greenland summit seasonal and interannual variations in surface elevation at the greenland summit are modeled using a new temperature dependent formulation of firn densification and are compared with elevations from european remote sensing satellite ers 1 2 radar altimetry the rate constant and activation energy usually set as constants in the arrhenius type relation are strongly temperature dependent based on measurements of crystal growth rates a multiplicative factor in the densification rate accounts for differences between densification and grain growth rates and is chosen to match the modeled and measured density profiles from 0 to 40 m the stronger temperature dependence produces a significant seasonal cycle in the densification rate in the upper firn much of the densification and consequent surface lowering occur within 3 months in late spring early summer followed by a build up from accumulation modeled elevation changes using automatic weather station measurements of temperature and accumulation and modeled precipitation agree well with observations the respective seasonal amplitudes are 18 and 25 cm peak to peak with minima in mid summer the minimum elevation in 1995 is driven mainly by a temporary accumulation decrease and secondarily by warmer temperatures increased compaction driven by a summer warming trend decreases the modeled elevation 1992 99 by 20 cm but accumulation increases in latter years dominate the overall 4 2 cm a 1 trend

analysis of a 3 year meteorological record from the ablation zone of morteratschgletscher switzerland energy and mass balance since 1 october 1995 an automatic weather station has been operated on the tongue of morteratschgletscher switzerland the station stands freely on the ice and sinks with the melting glacier surface it is located at 2100 m a s l and measures air temperature wind speed and direction incoming and reflected solar radiation pressure and snow temperature a sonic ranger mounted to stakes drilled into the ice measures surface height from which melt rates and snow accumulation can be derived in this paper the data for the period 1 october 1995 to 30 september 1998 are used to evaluate the surface energy balance the turbulent energy fluxes are calculated with the bulk method the turbulent exchange coefficient c h is used as a control parameter with c h 0 00127 the calculated melt equals the observed melt which is 17 70 m w e over the 3 years when averaged over the time when melting occurs i e 35 of the time the mean surface heat flux equals 191 w m 2 net shortwave radiation contributes 177 w m 2 net longwave radiation 25 w m 2 the sensible heat flux 31 w m 2 and the latent heat flux 8 w m 2