remote sensing estimates of glacier mass balances in the himachal pradesh western himalaya india abstract although they correspond to an important fraction of the total area of mountain glaciers 33 000 km2 out of 546 000 km2 himalayan glaciers and their mass balance are poorly sampled for example between 1977 and 1999 the average area surveyed each year on the field was 6 8 km2 only no direct mass balance measurement is available after 1999 to contribute to fill this gap we use remote sensing data to monitor glacier elevation changes and mass balances in the spiti lahaul region 32 2 n 77 6 e himachal pradesh western himalaya india our measurements are obtained by comparing a 2004 digital elevation model dem to the 2000 srtm shuttle radar topographic mission topography the 2004 dem is derived from two spot5 satellite optical images without any ground control points this is achieved thanks to the good on board geolocation of spot5 scenes and using srtm elevations as a reference on the ice free zones before comparison on glaciers the two dems are analyzed on the stable areas surrounding the glaciers where no elevation change is expected two different biases are detected a long wavelength bias affects the spot5 dem and is correlated to an anomaly in the roll of the spot5 satellite a bias is also observed as a function of altitude and is attributed to the srtm dataset both biases are modeled and removed to permit unbiased comparison of the two dem on the 915 km2 ice covered area digitized from an aster image on most glaciers a clear thinning is measured at low elevations even on debris covered tongues between 1999 and 2004 we obtain an overall specific mass balance of 0 7 to 0 85 m a water equivalent depending on the density we use for the lost or gained material in the accumulation zone this rate of ice loss is twice higher than the long term 1977 to 1999 mass balance record for himalaya indicating an increase in the pace of glacier wastage to assess whether these ice losses are size dependant all glaciers were classified into three samples according to their areal extent all three samples show ice loss the loss being higher for glaciers larger than 30 km2 in the case of the benchmark chhota shigri glacier a good agreement is found between our satellite observations and the mass balances measured on the field during hydrological years 2002 2003 and 2003 2004 future studies using a similar methodology could determine whether similar ice losses have occurred in other parts of the himalaya and may allow evaluation of the contribution of this mountain range to ongoing sea level rise

a comparison of three methods of mass balance determination in the tuyuksu glacier region tien shan central asia a photogrammetric survey in 1998 formed the basis for compiling a map of the tuyuksu glacier region in the northern tien shan central asia comparison with a map from 1958 enables calculation of the change in glacier volume over 40 years the results are compared with direct annual measurements carried out continuously since 1956 central tuyuksu glacier shows a mass balance of 12 6 m w e for the geodetic method and 16 8 m for glaciological measurements in view of the high accuracy of the maps the discrepancy can be explained mainly by deficiencies in the glaciological measurements application of the precipitation runoff model hbv eth represents the hydrological method of mass balance determination and delivers specific mass balance losses almost twice those indicated by the geodetic observations this discrepancy is suspected to be caused by erroneous runoff measurements the volume balance derived by the geodetic method is used to calibrate both the glaciological and the hydrological method

comparison of geodetic and glaciological mass balance techniques gulkana glacier alaska u s a the net mass balance on gulkana glacier alaska u s a has been measured since 1966 by the glaciological method in which seasonal balances are measured at three index sites and extrapolated over large areas of the glacier systematic errors can accumulate linearly with time in this method therefore the geodetic balance in which errors are less time dependent was calculated for comparison with the glaciological method digital elevation models of the glacier in 1974 1993 and 1999 were prepared using aerial photographs and geodetic balances were computed giving 6 0 0 7 m w e from 1974 to 1993 and 11 8 0 7 m w e from 1974 to 1999 these balances are compared with the glaciological balances over the same intervals which were 5 8 0 9 and 11 2 1 0 m w e respectively both balances show that the thinning rate tripled in the 1990s these cumulative balances differ by 6 for this close agreement the glaciologically measured mass balance of gulkana glacier must be largely free of systematic errors and be based on a time variable area altitude distribution and the photography used in the geodetic method must have enough contrast to enable accurate photogrammetry

a multi proxy record of holocene climatic change in southwestern spain the laguna de medina cadiz palaeolimnological data diatoms ostracods foraminifera molluscs aquatic pollen and lithology from a radiocarbon dated sediment core from a saline lake the laguna de medina provide the first complete record of holocene lake level change for southwest spain for the last c 9000 cal years the lake has always been relatively shallow but has exhibited marked fluctuations in salinity and water depth especially in the earlier record when oscillations culminate in maximum lake levels from c 6960 6680 cal bp c 6070 5830 bp indicating enhanced early to mid holocene humidity and a mid holocene humidity maximum prolonged shallowing thereafter reflects in part increased aridity in the later holocene lake desiccation followed by a c 800 yr phase zone 2 of major limnological change commencing at c 8000 cal bp c 7200 bp and a number of other abrupt desiccation events are also noteworthy the mid holocene maximum is consistent with widespread evidence for high lake levels around 6000 bp but t

arid and humid phases in southern spain during the last 4000 years the zonar lake record cordoba a multiproxy study of sediment cores from zonar lake 37 29 00 n 4 41 22 w 300 m a s l supported by 11 14c ams dates provides the first high resolution centennial scale reconstruction of past h

holocene hydrological changes in south western mediterranean as recorded by lake level fluctuations at lago preola a coastal lake in southern sicily italy abstract this paper presents a high resolution lake level record for the holocene at lago preola sicily southern italy based on a specific sedimentological approach with a chronology derived from ams radiocarbon dates it gives evidence of three major successive palaeohydrological periods with 1 a pronounced dryness during the early holocene until ca 10300 cal bp 2 a highstand from ca 10300 to 4500 cal bp and 3 a marked lowstand from 4500 cal bp to present large amplitude lake level fluctuations characterise two transition phases at ca 10300 9000 and 6400 4500 cal bp period 2 was interrupted between 8300 and 7000 cal bp by a dry phase that was punctuated to ca 7300 cal bp by the deposition of a tephra from neighbouring pantelleria island comparisons of the preola record with other palaeohydrological records along north south and west east transects in the mediterranean show contrasting patterns of hydrological changes north south of around 40 n latitude the records highlight a mid holocene period characterised by lake level minima maxima humid mid holocene conditions over the mediterranean south of 40 n were probably linked to a strong weakening of the hadley cell circulation and of monsoon winds we suggest that the maximum of humidity in the mediterranean during the mid holocene was characterised by humid winters to the north of 40 n and humid summers to the south on a multi centennial scale the high resolution palaeohydrological reconstructions in the central mediterranean area reveal a strong climate reversal around 4500 4000 cal bp with contrasting changes in the hydrological cycle in addition to seasonal and inter hemispherical changes related to orbital forcing this major oscillation might be related to non linear responses of the climatic system to the gradual decrease in summer insolation at northern latitudes another major climate oscillation around 7500 7000 cal bp may have resulted from the combined effects of 1 a strong rate of change in insolation and 2 variations in solar activity finally comparisons of the preola lake level record with sicilian pollen records suggest a strong influence of moisture availability on vegetation development in sicily very dry early holocene conditions probably prevented the expansion of coastal evergreen forests while decreasing moisture availability since the onset of the late holocene may have exacerbated effects of intensive land use

climate change and cultural response around 4000 cal yr b p in the western part of chinese loess plateau new data suggest that dramatic environmental change in the western loess plateau of china corresponded with substantial changes in human demography ca 4000 cal yr b p these data demonstrate that a rapid climatic transition from wet to dry led to an ecologically devastated period between 4090 and 3600 cal yr b p the sudden reduction in the number of archaeological sites during this period namely a reduction in the total number of sites and a contraction of the areal distribution of sites points to declining agricultural productivity associated with widespread aridification beginning at 4000 cal yr b p 2005 published by university of washington

holocene climate variability and change a data based review the holocene thermal maximum with peak temperatures prior to 7 ka bp is mostly accentuated in the northern hemisphere still visible in the southern hemisphere and possibly did not exist in the tropics between this period and the modern warming a remarkable negative temperature trend occurred in the northern hemisphere which was probably the effect of a decreasing orbital induced insolation during the boreal summer on average the northern hemisphere humidity precipitation records do not show any significant trend a mechanistic explanation for the multi decadal to century scale holocene cold relapses which mainly occurred in the atlantic european regions exists for only the early holocene cooling events which are probably the result of a collapse of the meridional overturning circulation owing to freshwater outbursts from the laurentide ice sheet possibly the late holocene cold events after c 4 ka bp are influenced by the covarying influence of major tropical volcanic eruptions and grand solar minima

slight mass loss revealed by reanalyzing glacier mass balance observations on glaciar antisana 15α inner tropics during the 1995 2012 period in this paper we reanalyze the glacier mass balance on glaciar antisana 15 over the 1995 2012 period annual glacier mass balances were quantified on the basis of monthly glaciological measurements using an adaptation of lliboutry s statistical approach the geodetic mass balance was computed between 1997 and 2009 giving a cumulative balance of 1 39 1 97 m w e and a slightly negative adjusted annual glaciological mass balance 0 12 0 16 m w e a 1 despite a careful analysis of uncertainties we found a large discrepancy between the cumulative glaciological and the geo detic mass balances over the common period of 4 66 m w e this discrepancy can mainly be explained by underestimated net accumulation in the glacier upper reaches which could be due to the peculiar climate conditions of the equatorial zone with year round accumulation thereby preventing clear identification of annual layers an increase of 70 in measured rates of net accumulation would be needed to balance the glaciological and geodetic mass balances a hypothesis confirmed by estimated ice flux in the vicinity of the ela consequently the vertical gradient of precipitation may be higher than previously estimated and the accumulation processes including the role of frost deposition need to be carefully analyzed

persistent solar influence on north atlantic climate during the holocene surface winds and surface ocean hydrography in the subpolar north atlantic appear to have been influenced by variations in solar output through the entire holocene the evidence comes from a close correlation between inferred changes in production rates of the cosmogenic nuclides carbon 14 and beryllium 10 and centennial to millennial time scale changes in proxies of drift ice measured in deep sea sediment cores a solar forcing mechanism therefore may underlie at least the holocene segment of the north atlantic9s 1500 year cycle the surface hydrographic changes may have affected production of north atlantic deep water potentially providing an additional mechanism for amplifying the solar signals and transmitting them globally

high resolution fluvial record of late holocene geomorphic change in northern tunisia climatic or human impact abstract in northern tunisia the late holocene alluvial record of medjerda floodplain sediments indicates geomorphic changes due to fluctuations of past climate superimposed by the effects of human activity geomorphic activity occurred several times interrupting stable conditions enhanced fluvial dynamics occurred around 4 7 3 0 1 7 1 0 and 0 7 ka cal bp a peak of activity took place about 0 4 ka cal bp some periods of fluvial activity show event like phenomena in particular when an anthropogenic impact intensifies climatic aridification this has been the case around 1 7 1 0 0 7 and 0 4 ka cal bp with severe floods in the medjerda valley during antiquity as well as around 1 3 0 8 and 0 5 ka cal bp immature alluvial soils have developed the first one being the most distinct late holocene medjerda alluvial history shows that fluvial dynamics in northern tunisia were predominantly climate driven anthropogenic impact only intensified or weakened these processes

contrasting patterns of early twenty first century glacier mass change in the himalayas glaciers are among the best terrestrial climate indicators an important water resource in mountains1 2 and a major contributor to global sea level rise3 4 in the hindu kush karakoram himalaya region hkkh a paucity of appropriate glacier data has prevented a comprehensive assessment of current regional mass balance5 however there are indirect evidences of a complex pattern of glacial responses5 8 in reaction to heterogeneous climate change signals9 here we provide the first coherent data set of detailed glacier thickness changes over the hkkh during 2003 2009 by combining satellite laser altimetry and a global elevation model in the eastern central and south western parts of the hkkh glacier wastage is widespread with regional thinning rates up to 0 66 0 09 m a 1 in the jammu kashmir region conversely in the karakoram glaciers are close to balance with only a slight thinning of 0 07 0 04 m a 1 regionally averaged thinning rates under debris mantled ice are similar to those of clean ice despite insulation by debris covers the 2003 2008 specific mass balance for our hkkh study region is 0 21 0 05 m a 1 water equivalent we significantly less negative than the global average of 0 7 m a 1 we for glaciers and ice caps4 10 this difference is mainly an effect of the balanced glacier mass budget in the karakoram the corresponding hkkh sea level contribution is 0 035 0 009 mm a 1 amounting to 1 of the present day sea level rise11 our 2003 2008 mass budget of 12 8 3 5 gt a 1 is more negative than recent satellite gravimetry based estimates of 5 6 gt a 1 over 2003 2010 ref 12 for the mountain catchments of the indus and ganges basins13 the glacier imbalance contributes 3 5 and 2 0 respectively to the annual average river discharge13 and up to 10 for the upper indus basin14

spatial patterns of glaciers in response to spatial patterns in regional climate abstract glaciers are direct recorders of climate history and have come to be regarded as emblematic of climate change they respond to variations in both accumulation and ablation which can have separate atmospheric controls leading to some ambiguity in interpreting the causes of glacier changes both climate change and climate variability have characteristic spatial patterns and time scales the focus of this study is the regional scale response of glaciers to natural patterns of climate variability using the pacific northwest of north america as the setting the authors employ a simple linear glacier model to study how the combination of patterns of melt season temperature and patterns of annual accumulation produce patterns of glacier length variations regional scale spatial correlations in glacier length variations reflect three factors the spatial correlations in precipitation and melt season temperature the geometry of a glacier and how it determines the relative importance of temperature and

mid and late holocene fluvial chronology of tunisia abstract regarding fluvial response to recent climate change it is important to identify and understand previous changes of fluvial dynamics related to past climatic shifts in this paper periods of increased flood activity in central tunisian river systems are presented changes in holocene flood dynamics are reconstructed through a comprehensive analysis of 195 radiocarbon dates from alluvial archives holocene floodplain deposits in central tunisia normally consists of cohesive overbank fines which exhibit excellent preservation conditions against lateral erosion and therefore permit chronostratigraphic records of the entire holocene at most based on published radiocarbon dates two 14 c cumulative probability density plots are created for central tunisia the former represents activity dates indicating phases of increased fluvial dynamics the latter documents stability dates showing periods of soil formation and enhanced landscape stability within the floodplain and the catchment due to geomorphological considerations activity dates and stability dates should be mutually exclusive there is a good match for the mid holocene with increased periods of flooding from 6 2 to 6 0 4 8 to 4 5 4 1 to 3 7 and 3 3 to 3 0 ka these flood periods coincide with low soil formation signals on the other hand periods of increased alluvial soil formation from 6 8 to 6 6 5 9 to 4 8 4 5 to 4 1 3 7 to 3 3 3 0 to 2 8 and 1 8 to 1 6 ka coincide with periods of low flood plain aggradation the data reveal a coupling with north atlantic cooling short term periods of enhanced fluvial dynamics in central tunisia match well with north atlantic cooling the findings indicate a strong climatic link from 4 7 ka until today compared to the holocene floodplain dynamics in tunisian drylands the temperate mid latitudes show mid holocene switches in fluvial dynamics with opposite signs especially after 5 ka north atlantic driven flooding in the temperate central european river systems contrast sharply to flood dynamics in arid to semiarid mediterranean tunisia while under temperate climate conditions floodplain sedimentation decreases it increases under more arid conditions this may indicate that fluvial archives of dissimilar climatic zones reveal different threshold values and sedimentation patterns and therefore different responses to climatic shifts

mass balance observations and reconstruction for haxilegen glacier no 51 eastern tien shan from 1999 to 2015 haxilegen glacier no 51 43 731 n 84 391 e cn5y741c0051 is located in the kuytun river basin erenharbirga range eastern tien shan this study presents the annual mass balance of haxilegen glacier no 51 for 7 hydrological years and uses a temperature index and an accumulation model to reconstruct the annual mass balance from 1999 to 2015 the model is calibrated against annual altitudinal mass balance measurements and then applied to the period with no measurements we find an accumulated mass balance of 6 06 0 88 m w e a 1 over the period of 16 hydrological years with an average annual value of 0 32 0 22 m w e a 1 the mean glacier wide annual summer and winter balances for 1999 to 2015 are 0 37 0 54 and 0 16 0 22 m w e a 1 respectively with a high correlation coefficient r 0 95 p 0 001 between annual balance and summer balance the calculated mass balance sensitivity of the glacier to temperature is 0 51 m w e a 1 c 1 and to precipitation is 0 08 m w e a 1 for a 10 increase the sensitivity of seasonal mass balance indicates that temperature during the melt season may august and annual precipitation are the major contributors to mass balance fluctuation

representation of subsurface storm flow and a more responsive water table in a topmodel based hydrology model 1 this study presents two new modeling strategies first a methodology for representing the physical process of subsurface storm flow within a topmodel framework is developed in using this approach discharge at quick flow timescales is simulated and a fuller depiction of hydrologic activity is brought about discharge of water from the vadose zone is permitted in a physically realistic manner without a priori assumption of the level within the soil column at which subsurface storm flow saturation can take place determination of the subsurface storm flow contribution to discharge is made using the equation for groundwater flow no new parameters are needed instead regions in excess of field capacity that develop during storm events producing vertical recharge are also allowed to contribute to soil zone discharge these subsurface storm flow contributions to river runoff as for groundwater flow contributions are a function of catchment topography and hydraulic conductivity at the depth at which such regions in excess of field capacity occur the second approach improves groundwater flow response through a reduction of porosity and field capacity with depth in the soil column large storm events are better captured and a more dynamic water table develops with application of this modified soil column profile mscp the mscp predominantly reflects soil depth differences in upland and lowland regions of a watershed combined these two approaches subsurface storm flow and the mscp provide a more accurate representation of the timescales at which discharge responds and a more complete depiction of hydrologic activity storm events large and small are better simulated and some of the biases previously evident in topmodel simulations are reduced

the holocene fluvial chronology of spain evidence from a newly compiled radiocarbon database abstract a critical analysis of 74 radiocarbon dates selected from a total of 102 published and unpublished dates from holocene fluvial environments in spain has identified a number of periods of increased fluvial activity in spain namely 11 170 10 230 9630 8785 7980 6860 5800 4800 3880 3085 2895 1820 1300 0 cal bp the latter period reflecting sustained fluvial response to increased human impact the radiocarbon samples were classified according to type of depositional environment a alluvial overbank b flood basin c alluvial channel gravels d fluvio torrential deposits and e slackwater flood deposits palaeofloods dates from slackwater flood deposits indicated at least five phases of increased frequency of large magnitude floods during the holocene 10 855 10 230 9530 8780 2880 2430 975 790 and 520 265 cal yr bp flood basin type deposition occurred from 7980 to 4830 cal yr bp the main clusters of dates from alluvial floodplain deposits occurred at 2750 2150 and 930 520 cal yr bp the record is discussed in relation to other palaeoenvironmental archives including pollen records of holocene vegetation change and palaeoclimatic proxies such as the north atlantic drift ice record comparison with the latter indicates that major holocene flooding coincided with cold climate phases during 9530 9280 2880 2430 and 520 265 cal yr bp a cooling phase at 10 855 10 230 and warming phases at 9030 8780 and 975 790 cal yr bp

dry or humid mid holocene humidity changes in arid and semi arid china abstract spatial changes of effective moisture during the mid holocene have been reconstructed based on the compilation of recently published paleoclimate records including ice core lake level pollen assemblage and loess paleosol records both geological data and the spatial pattern indicate that it was dry in deserts during the mid holocene but the timing of the beginning and end of dry intervals differs from place to place deserts having higher aridity index values remain dry longer dry intervals during the mid holocene are more possibly asynchronous than synchronous in arid and semi arid china in the xinjiang region except in sites located in deserts the climate is generally wet during 7000 5000 a bp in the northern qinghai tibetan plateau effective moisture in most sites began to decrease after 5000 a bp the climate became dry after 4000 a bp except in the deserts in the loess plateau and the inner mongolia plateau

millennial scale cycles of aridity as a driver of human occupancy in central spain human settlements around the fluvial wetland of las tablas de daimiel central spain have been related to the water availability in this area for nearly 5500 years however the relationship of the hydrology of the wetland to climate change remains uncertain whilst archaeological and pollen data provide contradictory arguments statistical empirical mode decomposition of geochemical data from core s 1 reveals arid periods ca 1 8 cal ka bp ca 3 3 cal ka bp and ca 5 5 cal ka bp between which periods both bronze age and iberian roman settlements developed these periods can be identified in other records of the iberian peninsula and around the western mediterranean comparison of these records points to a complex spatial pattern that evolved in time and despite a number of forcings volcanism solar activity atmosphere ocean interactions being invoked to explain such periods there is no clear mechanism to explain their spatial pattern and the changes that have taken place since 2 5 ka bp

a comparison of seismic and radar methods to establish the thickness and density of glacier snow cover we show that geophysical methods offer an effective means of quantifying snow thickness and density opportunistic efficient but non optimized seismic refraction and ground penetrating radar gpr

area and mass changes of siachen glacier east karakoram here we present a comprehensive assessment of siachen glacier east karakoram in terms of its area and elevation change velocity variations and mass budget utilizing different satellite datasets including landsat hexagon cartosat i shuttle radar topography mission envisat advanced synthetic aperture radar and japanese advanced land observing satellite phased array type l band sar the total areal extent of siachen glacier did not change significantly between 1980 and 2014 however the exposed ice area decreased during that period the terminus of the glacier has experienced substantial downwasting on average 30 m over the period of 1999 2007 followed by a retreat of the transition between exposed and debris covered ice by a distance of 1 3 km during the short span 2007 14 the spatial patterns of the elevation difference and velocity are heterogeneous over the large areal extent of siachen glacier the average velocity of the entire glacier as computed between 11 december 2008 and 26 january 2009 was 12 3 0 4 cm d 1 while those estimated separately for the accumulation and ablation regions were 9 7 0 4 cm d 1 and 20 4 0 4 cm d 1 respectively the mass budget of siachen glacier is estimated to be 0 03 0 21 m w e a 1 for the period of 1999 2007

the causes of waterlogging in shallow soils and their drainage in southwestern australia abstract sandy loam topsoils overlying sandy clay subsoils on hillslopes in southwestern australia are often waterlogged the relative importance of soil landform climatic and drainage factors on waterlogging intensity was assessed from 1984 to 1986 the sew 30 index was used to quantify waterlogging intensity as measured in 162 shallow wells in five subcatchments waterlogging is caused by the development of a perched watertable on the subsoil clay gravel within the soil profile reduces the porosity and thus the water storage capacity of the soil waterlogging intensity is low where topsoils are deeper than about 0 6 m where the soil profile has an a 2 horizon with high hydraulic conductivity up to 7 8 m day 1 and the site is sloping facilitating lateral flows the hydraulic conductivity of the b horizon can change by as much as two orders of magnitude over a 10 m lateral distance the sites most susceptible to waterlogging have subsoils with a hydraulic conductivity less than 0 003 m day 1 and topsoils which are less than 0 4 m thick susceptible soils became waterlogged in early winter after rainfall exceeded pan evaporation by just 50 mm whereas others remained well drained even in the wettest years q 0 2 5 10 3 m 2 day 1 per m cross section of the soil is a critical value of transmission capacity that induces severe waterlogging in these catchments

the mass balance of mccall glacier brooks range alaska u s a its regional relevance and implications for climate change in the arctic mccall glacier has the only long term mass balance record in arctic alaska average annual balances over the periods 1958 72 and 1972 93 were 15 and 33cm respectively recent annual balances 1993 96 are about 60 cm and the mass balance gradient has increased for an arctic glacier with its low mass exchange rate this marks a significant negative trend recently acquired elevation profiles of mccall glacier and ten other glaciers within a 30 km radius were compared with topographic maps made in 1956 or 1973 most of these glaciers had average annual mass balances between 25 and 33 cm while mccall glacier averaged 28 cm for 1956 93 indicating that it is representative of the region in contrast changes in terminus position for the different glaciers vary markedly thus mass balance trends in this region cannot be estimated from fractional length changes at time scales of a few decades we developed a simple degree day accumulation mass balance model for mccall glacier the model was tested using precipitation and radiosonde temperatures from weather stations at inuvik canada and barrow kaktovik and fairbanks alaska and was calibrated with the measured balances the inuvik data reproduce all measured mass balances of mccall glacier well and also reproduce the long term trend towards more negative balances data from the other stations do not produce satisfactory model results we speculate that the arctic front oriented east west in this region causes the differences in model results

mass balance changes of the debris covered glaciers in the langtang himal nepal from 1974 to 1999 thick debris cover on glaciers can significantly reduce ice melt however several studies have suggested that debris covered glaciers in the himalaya might have lost mass at a rate similar to debris free glaciers we reconstruct elevation and mass changes for the debris covered glaciers of the upper langtang valley nepalese himalaya using a digital elevation model dem from 1974 stereo hexagon satellite data and the 2000 srtm shuttle radar topography mission dem uncertainties are high in the accumulation areas due to data gaps in the srtm and difficulties with delineation of the glacier borders even with these uncertainties we obtain thinning rates comparable to those of several other studies in the himalaya in particular we obtain a total mass balance for the investigated debris covered glaciers of the basin of 0 32 0 18 m w e a 1 however there are major spatial differences both between glaciers and within any single glacier exhibiting a very distinct nonlinear mass balance profile with elevation through analysis of surface velocities derived from landsat etm imagery we show that thinning occurs in areas of low velocity and low slope these areas are prone to a general dynamic decay of surface features and to the development of supraglacial lakes and ice cliffs which may be responsible for a considerable increase in overall glacier ablation

spatial organization of soil depths using a landform evolution model 1 the evolution of soil depths is investigated by modeling the interaction between soil production and surface erosion within a landform evolution model an enhanced version of the landform evolution model siberia that incorporates a soil evolution module is used to simulate evolving landforms and soils depths over geologic timescales the spatial and temporal evolution of soil depths are examined at the hillslope scale though it is widely accepted among the geomorphology community that soil water enhances chemical physical and biological weathering processes its effect has not been explicitly included in published models of soil production the main scientific questions that we address are 1 what are the implications of incorporating soil moisture dependency in the soil production function and 2 what type of soil production dynamics is needed to generate a bedrock topography that has a different spatial pattern from that of the ground surface a range of physics for the soil production model is explored the effect of soil moisture is included using the wetness index obtained from drainage analysis of either surface elevations or the bedrock topography the results show that the various soil production functions that incorporate either a wetness index or subsurface flow depth based on the bedrock topography give rise to soils that self organize with well defined spatial patterns and bedrock elevations with spatial organization significantly different from that of the surface the model that incorporates the influence of subsurface water on soil production is able to naturally generate a soil production rate with a maximum value for a nonzero soil depth and overcomes an inconsistency of previously published humped soil production models

structure morphology and water flux of a subglacial drainage system midtdalsbreen norway digital elevation models of the surface and bed of midtdalsbreen norway are used to calculate subglacial hydraulic potential and infer drainage system structure for a series of subglacial water pressure assumptions ranging from atmospheric to ice overburden a distributed degree day model is used to calculate the spatial distribution of melt on the glacier surface throughout a typical summer which is accumulated along the various drainage system structures to calculate water fluxes beneath the glacier and exiting the portals for the different water pressure assumptions in addition 78 dye tracing tests were performed from 33 injection sites and numerous measurements of water discharge were made on the main proglacial streams over several summer melt seasons comparison of the calculated drainage system structures and water fluxes with dye tracing results and measured proglacial stream discharges suggests that the temporally and spatially averaged steady state water pressures beneath the glacier are 70 of ice overburden analysis of the dye return curves together with the calculated subglacial water fluxes shows that the main drainage network on the eastern half of the glacier consists of a hydraulically efficient system of broad low channels average width height ratio 75 the smaller drainage network on the west consists of a hydraulically inefficient distributed system dominated by channels that are exceptionally broad and very low average width height ratio 350 the even smaller central drainage network also consists of a hydraulically inefficient distributed system dominated by channels that are very broad and exceptionally low average width height ratio 450 the channels beneath the western and central glacier must be so broad and low that they can essentially be thought of as a linked cavity system

size specific steady state accumulation area ratio an improvement for equilibrium line estimation of small palaeoglaciers abstract characteristic distribution of the steady state accumulation area ratio aar0 of valley and corrie glaciers was investigated in a global dataset comprised of 46 glaciers there is a positive relationship between aar0 and glacier area with smaller glaciers having lower values of aar0 compared with larger glaciers the relationship between glacier area s and steady state aar of studied glaciers can be optimally described by a logarithmic regression equation this relationship is thought to be a globally valid approximation if the size of the glacier is not smaller than 10 1 km2 in the case of palaeoglaciers an aar0 value of 0 44 0 07 is best applied on glaciers with areas in the range 0 1 1 km2 0 54 0 07 for glaciers covering areas between 1 and 4 km2 and 0 64 0 04 for glaciers larger than 4 km2 this assumes insignificant debris cover for the investigated palaeoglaciers the proposed size specific aar0 values take into account the geometric hypsometric properties of palaeo glaciers the results have major importance for palaeoglaciological reconstructions in many regions of former marginal niche glaciation characterized by small former glaciers

variability of the north atlantic oscillation over the past 5 200 years the north atlantic oscillation influences climate in the arctic region and northern europe reconstructions of circulation patterns associated with the north atlantic oscillation from a 5 200 year long lake sediment record suggest that the atmospheric circulation responded to significant transitions in northern hemisphere climate

influence of antecedent soil moisture on hydraulic conductivity in a series of texture contrast soils antecedent soil moisture significantly influenced the hydraulic conductivity of the a1 a2e and b21 horizons in a series of strong texture contrast soils tension infiltration at six supply potentials demonstrated that in the a1 horizon hydraulic conductivity was significantly lower in the wet treatment than in the dry treatment however in the a2e horizon micropore and mesopore hydraulic conductivity was lower in the dry treatment than the wet treatment which was attributed to the precipitation of soluble amorphous silica in the b21 horizon desiccation of vertic clays resulted in the formation of shrinkage cracks which significantly increased near saturated hydraulic conductivity and prevented the development of subsurface lateral flow in the dry treatment in the wet treatment the difference between the hydraulic conductivity of the a1 and b21 horizons was reduced however lateral flow still occurred in the a1 horizon due to difficulty displacing existing soil water further down the soil profile results demonstrate the need to account for temporal variation in soil porosity and hydraulic conductivity in soilwater model conceptualisation and parameterisation

high resolution monitoring of himalayan glacier dynamics using unmanned aerial vehicles himalayan glacier tongues are commonly debris covered and they are an important source of melt water however they remain relatively unstudied because of the inaccessibility of the terrain and the difficulties in field work caused by the thick debris mantles observations of debris covered glaciers are therefore scarce and airborne remote sensing may bridge the gap between scarce field observations and coarse resolution space borne remote sensing in this study we deploy an unmanned aerial vehicle uav before and after the melt and monsoon season may and october 2013 over the debris covered tongue of the lirung glacier in nepal based on stereo imaging and the structure for motion algorithm we derive highly detailed ortho mosaics and digital elevation models dems which we geometrically correct using differential gps observations collected in the field based on dem differencing and manual feature tracking we derive the mass loss and the surface velocity of the glacier at a high spatial accuracy on average mass loss is limited and the surface velocity is very small however the spatial variability of melt rates is very high and ice cliffs and supra glacial ponds show mass losses that can be an order of magnitude higher than the average we suggest that future research should focus on the interaction between supra glacial ponds ice cliffs and englacial hydrology to further understand the dynamics of debris covered glaciers finally we conclude that uav deployment has large potential in glaciology and it may revolutionize methods currently applied in studying glacier surface features

structure and origin of holocene cold events abstract the present interglacial the holocene spans the period of the last 11 700 years it has sustained the growth and development of modern society the millennial scale decreasing solar insolation in the northern hemisphere summer lead to northern hemisphere cooling a southern shift of the intertropical convergence zone itcz and a weakening of the northern hemisphere summer monsoon systems on the multidecadal to multicentury scale periods of more stable and warmer climate were interrupted by several cold relapses at least in the northern hemisphere extra tropical area based on carefully selected 10 000 year long time series of temperature and humidity precipitation as well as reconstructions of glacier advances the spatiotemporal pattern of six cold relapses during the last 10 000 years was analysed and presented in form of a holocene climate atlas hoclat see http www oeschger unibe ch research projects holocene atlas a clear cyclicity was not found and the spatiotemporal variability of temperature and humidity precipitation during the six specific cold events 8200 6300 4700 2700 1550 and 550 years bp was very high different dynamical processes such as meltwater flux into the north atlantic low solar activity explosive volcanic eruptions and fluctuations of the thermohaline circulation likely played a major role in addition internal dynamics in the north atlantic and pacific area including their complex interaction were likely involved

glacier change in norway since the 1960s an overview of mass balance area length and surface elevation changes in this paper we give an overview of changes in area length surface elevation and mass balance of glaciers in mainland norway since the 1960s frontal advances have been recorded in all regions except the northernmost glaciers in troms and finnmark storsteinsfjellbreen lyngen and langfjordjokelen more than half of the observed glaciers 27 of 49 had marked advances in the 1990s the glaciological mass balance values for the period 1962 2018 where 43 glaciers have been measured show great inter annual variability the results reveal accelerated deficit since 2000 the most negative decade being 2001 2010 some years with a positive mass balance or less negative after 2010s can be attributed to variations in large scale atmospheric circulation a surface elevation change and geodetic mass balance were calculated for a sample of 131 glaciers covering 817 km 2 in the 1960s and 734 km 2 in the 2010s giving an area reduction of 84 km 2 or 10 the sample covers many of the largest glaciers in norway and they had an overall change in surface elevation of 15 5 m for the 50 year period converted to a geodetic mass balance this gives a mean mass balance of 0 27 0 05 m w e a 1

mass balance reconstruction for glacier no 354 tien shan from 2003 to 2014 this study presents a reconstruction of the seasonal mass balance of glacier no 354 located in the akshiirak range kyrgyzstan from 2003 to 2014 we use a distributed accumulation and temperature index melt model driven by daily air temperature and precipitation from a nearby meteorological station the model is calibrated with in situ measurements of the annual mass balance collected from 2011 to 2014 the snow cover depletion pattern observed using satellite imagery provides additional information on the dynamics of mass change throughout the melting season two digital elevation models derived from high resolution satellite stereo images acquired in 2003 and 2012 are used to calculate glacier volume change for the corresponding period the geodetic mass change thus derived is used to validate the modelled cumulative glacier wide balance for the period 2003 12 we find a cumulative mass balance of 0 40 10mw e a 1 this result agrees well with the geodetic balance of 0 48 0 07mw e a 1 over the same period

changes in area and geodetic mass balance of small glaciers polar urals russia 1950 2008 changes in area of 30 small glaciers mostly 1 km2 in the northern polar urals 67 5 68 25 n between 1953 and 2000 were assessed using historic aerial photography from 1953 and 1960 aster and panchromatic landsat etm imagery from 2000 and data from 1981 and 2008 terrestrial surveys changes in volume and geodetic mass balance of igan and obruchev glaciers were calculated using data from terrestrial surveys in 1963 and 2008 in total glacier area declined by 22 3 3 9 in the 1953 60 2000 period the areas of individual glaciers decreased by 4 46 surfaces of obruchev and igan glaciers lowered by 22 5 1 7 m and 14 9 2 1 m over 45 years geodetic mass balances of obruchev and igan glaciers were 20 66 2 91 and 13 54 2 57 m w e respectively glacier shrinkage in the polar urals is related to a summer warming of 1 c between 1953 81 and 1981 2008 and its rates are consistent with other regions of northern asia but are higher than in scandinavia while glacier shrinkage intensified in the 1981 2000 period relative to 1953 81 increasing winter precipitation and shading effects slowed glacier wastage in 2000 08

mid holocene climate variations revealed by high resolution speleothem records from soreq cave israel and their correlation with cultural changes mid holocene 7000 4000 yr bp paleoclimate conditions were reconstructed for the eastern mediterranean region through a high resolution 3 20 yr oxygen and carbon isotopic record in a speleothem

holocene climate variability although the dramatic climate disruptions of the last glacial period have received considerable attention relatively little has been directed toward climate variability in the holocene 11 500 cal yr b p to the present examination of similar to50 globally distributed paleoclimate records reveals as many as six periods of significant rapid climate change during the time periods 9000 8000 6000 5000 4200 3800 3500 2500 1200 1000 and 600 150 cal yr b p most of the climate change events in these globally distributed records are characterized by polar cooling tropical aridity and major atmospheric circulation changes although in the most recent interval 600 150 cal yr b p polar cooling was accompanied by increased moisture in some parts of the tropics several intervals coincide with major disruptions of civilization illustrating the human significance of holocene climate variability c 2004 university of washington all rights reserved

runoff and soil loss characteristics on loess slopes covered with aeolian sand layers of different thicknesses under simulated rainfall abstract in the wind water erosion crisscross region of the northern loess plateau parts of loess slopes have been covered by layers of aeolian sand of different thicknesses knowledge of soil erosion processes and magnitudes on these slopes is essential to understanding the coupled water wind erosion processes and to address the resulting downstream coarse sediment problems in the yellow river simulated rainfall intensity 90 mm h 1 was performed to explore the effects of sand layer thickness on runoff and soil loss from loess slopes covered with different sand layer thicknesses 0 0 5 2 5 10 15 20 and 25 cm initial runoff time increased with increasing sand layer thickness with greater changes occurring for the increases in the thinner 0 5 cm than for the thicker layers 5 25 cm total runoff yield from the sand covered loess slopes was 18 55 lower than from the uncovered loess slope and decreased with increasing sand layer thickness in contrast total sediment yield was up to 14 times greater from the sand covered loess slopes than from the uncovered loess slope and rapidly increased with increasing sand layer thickness during the rainstorm runoff and soil loss rates exhibited unimodal distributions and they were related by a positive linear function both before and after the maximum soil loss rate that had a high determination coefficient r2 0 8 p

climate at the equilibrium line of glaciers the relationships between temperature precipitation and radiation on glacier equilibrium lines are investigated using 70 glaciers for which the mass balance and meteorological observations have been carried out for sufficiently long periods it is found that the characteristic climate at glacier equilibrium lines can be described using the summer 3 months temperature in a free atmosphere annual total precipitation and the sum of global and long wave net radiation all of these are measured at or very near the equilibrium line altitudes then it is shown how the shift of the equilibriumline will occur as a result of a climatic change finally the effect of the shift of the equilibrium line on the annualmean specific mass balance is analytically derived and compared with observations the present results make it possible to identify the altitudes in climate models where glacierization should begin and to evaluate the mass balance changes as a result of possible future changes in the climate

centennial scale late pleistocene to mid holocene synthetic profile of the medjerda valley northern tunisia during the late pleistocene to mid holocene the medjerda river system in mediterranean tunisia shows events of increased flooding and aggradation of relatively coarse overbank deposits geomorphic activity in river systems within this region correlate with aridification of the climate but not with temperature the late pleistocene to mid holocene synthetic profile of the ghardimaou floodplain mid medjerda river indicates fluvial activity from 12 4 to 11 8 6 6 to 6 0 and after 4 8 ka cal bp external correlations imply global and regional causes of the late pleistocene to mid holocene climatic development such as north atlantic deep water formation fluctuations in saharan humidity and impacts of local mediterranean weather phenomena palaeomagnetic records offer additional opportunities to interpret fluvial activity in river systems especially for detecting chronological hiatuses in apparently homogeneous sediment sequences

elevation volume and terminus changes of nine glaciers in north america nine glaciers in alaska and washington u s a originally mapped as part of the international geophysical year igy in 1957 58 were re mapped between 1993 and 1996 eight using airborne surface elevation profiling and the ninth using ground based kinematic global positioning system methods elevation volume and terminus changes were determined for the approximately 38 year period between the igy mapping and the profiling all nine glaciers showed substantial thinning at lower elevations seven of the nine thickened at higher elevations none of the glaciers had a significant net volume increase two had close to zero change and the others had a decrease for the eight glaciers for which we could obtain quantitative information the mean thickness change was 10 m with a large scatter 8 m standard deviation the volume and terminus changes had no clear geographic pattern and no simple relationship between volume change and terminus advance or retreat was identified the largest error in the estimated volume changes is due to map errors

glacier mass balance determination by remote sensing and high resolution modelling an indirect methodology for determining the distribution of mass balance at high spatial resolution using remote sensing and ice flow modelling is presented the method based on the mass continuity equation requires two datasets collected over the desired monitoring interval i the spatial pattern of glacier surface elevation change and ii the mass flux divergence field at haut glacier d arolla valais switzerland the mass balance distribution between september 1992 and september 1993 is calculated at 20 m resolution from the difference between the pattern of surface elevation change derived from analytical photogrammetry and the mass flux divergence field determined from three dimensional numerical flow modelling constrained by surface velocity measurements the resultant pattern of mass balance is almost totally negative showing a strong dependence on elevation but with large localized departures the computed distribution of mass balance compares well r 2 0 91 with mass balance measurements made at stakes installed along the glacier centre line over the same period despite the highly optimized nature of the flow modelling effort employed in this study the good agreement indicates the potential this method has as a strategy for deriving high spatial and temporal resolution estimates of mass balance

mid holocene emergence of a low frequency millennial oscillation in western mediterranean climate implications for past dynamics of the north atlantic atmospheric westerlies the nature and tempo of holocene climate variability is examined in the record of forest vegetation from western mediterranean marine core md95 2043 episodes of forest decline occurred at 10 1 9 2 8 3 7 4 5 4 4 5 and 3 7 2 9 cal ka bp and between 1 9 cal ka bp and the top of the record 1 3 cal ka bp wavelet analysis confirms a 900 yr periodicity prior to and during the early holocene and the dominance of a 1750 yr periodicity after 6 cal ka bp the 900 yr periodicity has counterparts in numerous north atlantic and northern hemisphere palaeoclimate records and in solar irradiance proxies 14c and 10be and may relate to a sun climate connection during the early holocene comparisons between the md95 2043 forest record and strategically located records from morocco iceland norway and israel suggest that the 1750 yr mid to late holocene oscillation reflects shifts between a prevailing strong and weak state of the zonal flow with impacts similar to the positive and negative modes of th

global sea level contribution from the patagonian icefields since the little ice age maximum the melting of mountain glaciers and ice caps is expected to contribute significantly to sea level rise in the twenty first century 1 3 although the magnitude of this contribution is not fully constrained glaciers in the patagonian icefields of south america are thought to have contributed about 10 of the total sea level rise attributable to mountain glaciers in the past 50 years 3 however it is unclear whether recent rates of glacier recession in patagonia are unusual relative to the past few centuries here we reconstruct the recession of these glaciers using remote sensing and field determinations of trimline and terminal moraine location we estimate that the north patagonian icefield has lost 103 20 7 km 3 of ice since its late holocene peak extent in ad 1870 and that the south patagonian icefield has lost 503 101 1 km 3 since its peak in ad 1650 this equates to a sea level contribution of 0 0018 0 0004 mm yr 1 since 1870 from the north and 0 0034 0 0007 mm yr 1 since 1650 from the south the centennial rates of sea level contribution we derive are one order of magnitude lower than estimates of melting over the past 50 years 3 even when we account for possible thinning above the trimline we conclude that the melt rate and sea level contribution of the patagonian icefields increased markedly in the twentieth century

holocene palaeohydrology and climate variability in northeastern spain the sedimentary record of lake estanya pre pyrenean range abstract this multi proxy study of sediment cores from karstic lake estanya pre pyrenean range ne spain provides the first complete continuous record of the hydrological evolution in the northeastern iberian peninsula over the last 9500 yr six sedimentary facies and four main sedimentary units have been defined after integration of sedimentological mineralogical and geochemical analyses the use of total sulphur content and sedimentary facies as paleohydrological proxies allows reconstruction of relative changes in lake level the estanya record shows a large increase in water availability after 9 2 ka fluctuating lake levels and salinity during the period 9 2 4 2 ka and generally higher lake levels after 1 7 ka periods of increased run off and sediment delivery and less saline conditions occurred at 8 5 8 2 6 7 5 9 and 4 9 4 2 ka dominant lower lake levels and concentrated waters during the period 4 2 0 8 ka were punctuated by a higher lake level higher clastic input episode ca 1 7 1 ka fluctuating but higher lake levels occurred during the last 800 years the main hydrological phases in lake estanya are coherent with western mediterranean and north atlantic holocene reconstructions but they also show similarities with northern african records

mid to late holocene climate change an overview the last 6000 years are of particular interest to the understanding of the earth system because the boundary conditions of the climate system did not change dramatically in comparison to larger glacial interglacial changes and because abundant detailed regional palaeoclimatic proxy records cover this period we use selected proxy based reconstructions of different climate variables together with state of the art time series of natural forcings orbital variations solar activity variations large tropical volcanic eruptions land cover and greenhouse gases underpinned by results from general circulation models gcms and earth system models of intermediate complexity emics to establish a comprehensive explanatory framework for climate changes from the mid holocene mh to pre industrial time the redistribution of solar energy due to orbital forcing on a millennial timescale was the cause of a progressive southward shift of the northern hemisphere nh summer position of the intertropical convergence zone itcz this was accompanied by a pronounced weakening of the monsoon systems in africa and asia and increasing dryness and desertification on both continents the associated summertime cooling of the nh combined with changing temperature gradients in the world oceans likely led to an increasing amplitude of the el nin o southern oscillation enso and possibly increasingly negative north atlantic oscillation nao indices up to the beginning of the last millennium on decadal to multi century timescales a worldwide coincidence between solar irradiance minima tropical volcanic eruptions and decadal to multi century scale cooling events was not found however reconstructions show that widespread decadal to multi century scale cooling events accompanied by advances of mountain glaciers occurred in the nh e g in scandinavia and the european alps this occurred namely during the little ice age lia between ad w1350 and 1850 when the lower summer insolation in the nh due to orbital forcing coincided with solar activity minima and several strong tropical volcanic eruptions the role of orbital forcing in the nh cooling the southward itcz shift and the desertifi cation of the sahara are supported by numerous model simulations other simulations have suggested that the fingerprint of solar activity variations should be strongest in the tropics but there is also evidence that changes in the ocean heat transport took place during the lia at high northern latitudes with possible additional implications for climates of the southern hemisphere sh

late second early first millennium bc abrupt climate changes in coastal syria and their possible significance for the history of the eastern mediterranean the alluvial deposits near gibala tell tweini provide a unique record of environmental history and food availability estimates covering the late bronze age and the early iron age the refined pollen derived climatic proxy suggests that drier climatic conditions occurred in the mediterranean belt of syria from the late 13th early 12th centuries bc to the 9th century bc this period corresponds with the time frame of the late bronze age collapse and the subsequent dark age the abrupt climate change at the end of the late bronze age caused region wide crop failures leading towards socio economic crises and unsustainability forcing regional habitat tracking archaeological data show that the first conflagration of gibala occurred simultaneously with the destruction of the capital city ugarit currently dated between 1194 and 1175 bc gibala redeveloped shortly after this destruction with large scale urbanization visible in two main architectural phases during the early iron age i the later iron age i city was destroyed during a second conflagration which is radiocarbon dated at circa 2950 cal yr bp the data from gibala tell tweini provide evidence in support of the drought hypothesis as a triggering factor behind the late bronze age collapse in the eastern mediterranean

climate change at the 4 2 ka bp termination of the indus valley civilization and holocene south asian monsoon variability 1 planktonic oxygen isotope ratios off the indus delta reveal climate changes with a multi centennial pacing during the last 6 ka with the most prominent change recorded at 4 2 ka bp opposing isotopic trends across the northern arabian sea surface at that time indicate a reduction in indus river discharge and suggest that later cycles also reflect variations in total annual rainfall over south asia the 4 2 ka event is coherent with the termination of urban harappan civilization in the indus valley thus drought may have initiated southeastward habitat tracking within the harappan cultural domain the late holocene drought cycles following the 4 2 ka bp event vary between 200 and 800 years and are coherent with the evolution of cosmogenic 14c production rates this suggests that solar variability is one fundamental cause behind holocene rainfall changes over south asia

an optimized method to calculate the geodetic mass balance of mountain glaciers understanding the effects of climate on glaciers requires precise estimates of ice volume change over several decades this is achieved by the geodetic mass balance computed by two means 1 the digital elevation model dem comparison seqdem allows measurements over the entire glacier however the low contrast over glacierized areas is an issue for the dem generation through the photogrammetric techniques and 2 the profiling method sepm is a faster alternative but fails to capture the spatial variability of elevation changes we present a new framework ssd that relies upon the spatial variability of the elevation change to densify a sampling network to optimize the surface elevation change quantification our method was tested in two small glaciers over different periods we conclude that the sepm overestimates the elevation change by 20 with a mean difference of 1 00 m root mean square error rmse 3 00 m compared with results from the seqdem method a variogram analysis of the elevation changes showed a mean difference of

effect of antecedent soil moisture on preferential flow in a texture contrast soil summary the effect of soil moisture status on preferential flow in a texture contrast soil was investigated by applying 25 mm brilliant blue dye tracer to soil profiles at high and low antecedent soil moisture differences in soil morphology and chemistry between soil profiles had little effect on the depth of dye infiltration and dye distribution down the profile antecedent soil moisture strongly influenced the type depth and rate of dye tracer movement in the wet treatment the dye tracer infiltrated to depths between 0 24 and 0 40 m at an average rate of 120 mm h 1 whilst in the dry treatment the same volume of dye tracer infiltrated to between 0 85 and 1 19 m depth at an average rate of 1160 mm h 1 in dry antecedent conditions finger flow developed in the a1 horizon as a result of water repellency in the wet treatment the wetting front developed permutations but did not break into fingers despite similar particle size distributions flow in the a2 e was slower than the a1 horizon due to the absence of macropores in the dry treatment the dye tracer ponded on the upper surface of the b21 horizon which then spilled down the sides of the large clay columns as rivulets at rates of between 2000 and 3000 mm h 1 the dye tracer accumulated at the base of the columns resulting in backfilling of the inter column shrinkage cracks at an estimated rate of 750 mm h 1 in the subsoil water movement occurred via shrinkage cracks which resulted in flow by passing 99 of the soil matrix in the b21 horizon and 94 of the soil matrix in the b22 horizon evidence of rapid and deep infiltration in dry texture contrast soils has implications for water and solute management this knowledge could be used to i improve irrigation and fertilizer efficiency ii explain variations in crop yield iii reduce salinity through improved leaching practices iv reduce the risk of agrochemicals contaminating shallow groundwater

holocene climatic and environmental evolution on the southwestern iberian peninsula a high resolution multi proxy study from lake medina cadiz sw spain abstract the climatic and environmental history of the sw iberian peninsula is explored to fill in the gap of continental palaeoclimate data by a high resolution study of lake medina sediments from core co1313 a multi proxy approach comprising sedimentary facies analysis elemental geochemistry mineralogy palynology and micropaleontology was employed to reconstruct the complex limnological response to climate change and catchment dynamics since the early holocene the further definition of abrupt climate change events was supported by a robust age model and rapid sediment accumulation rate at the study site proxies indicate arid and warm climate conditions during the early holocene from around 9 5 to 7 8 cal ka bp with a desiccation event at 8 8 cal ka bp as well as tentative evidence for the regional expression of a cold and abrupt arid climate event centering on ca 8 2 cal ka bp the holocene climate optimum from around 7 8 to 5 5 cal ka bp is characterized by a humid climate and maximum lake level anoxic bottom water conditions are indicated by the preservation of sediment laminae and the occurrences of sulfur mottles which were observed for the first time within holocene sediments of saline lakes mid to late holocene times are governed by the 4 2 cal ka bp dry event as well as progressive aridification accompanied by the development of typical mediterranean low land vegetation during recent times further progressive loss in precipitation as well as fluctuating but overall increasing anthropogenic influence on lake medina sediments is observed

effect of subsoil conductivity and thickness on interflow pathways rates and source areas for chemicals in a sloping layered soil with seepage face abstract the effects of relative hydraulic conductivities and thicknesses of topsoil and subsoil layers and leakage rate of a compact base material on the saturated steady water flow through a sloping soil to an outflow face interflow were investigated theoretically the water was assumed to be supplied from the surface at a rate adequate to keep the entire soil saturated simplified descriptions of the interflow characteristics were sought wherever possible a gram schmidt orthonormalization procedure of w l powers d kirkham and g snowden provided a potential theory solution of the problem even though the outflow seepage face existed over two soil layers as reported earlier by the present authors for a nonlayered soil two regions of water entry and flow could be distinguished when the base material was not leaky 1 flow in the main body of soil region 1 and 2 additional infiltration and flow near the seepage face region 2 for a slope length soil depth ratio of 20 or greater the flow in region 1 could be approximated as a one dimensional flow downslope in each soil layer the length of slope that contributed to flow in region 2 was linearly related to the ratio of the hydraulic conductivity of the subsoil to that of the topsoil a subsoil of higher conductivity than that of the topsoil increased several fold the rate of infiltration and interflow and the soil both topsoil and subsoil volume that was traversed by interflow near the seepage face it also increased the area and rates of water entry and flow through the topsoil near the upper end of the slope a significant finding of this analysis is that the transport of topsoil chemicals to field runoff will be speeded up from certain now predictable portions of the slope length when the underlying base material was leaky some water entering the soil surface seeped into the base material and the soil volume traversed by the interflow was greatly reduced amounts of chemicals carried to the outflow face would also be reduced there were several situations of base leakage rates soil conductivities and thicknesses considered for leakage rates of practical interest the source areas and the soil volume traversed by the interflow could be predicted adequately by a simple procedure the total rates of water interflow in both the nonleaky and leaky base cases could be predicted adequately from known reference values of a nonlayered soil by using a weighted average hydraulic conductivity of the layered profile however for prediction of chemicals transported with interflow knowledge of the flow directions and rate variation along the slope length will be required

palynological evidence for environmental and climatic change in the lower guadiana valley portugal during the last 13 000 years pollen analysis of a 48 m ams radiocarbon dated sediment sequence from the guadiana estu ary provides the first record of lateglacial and holocene vegetation history in the algarve province of portugal this paper focuses on the record of terrestrial pollen taxa which document a series of forest expansions and declines during the period 13 000 cal bp to 1600 cal bp and provide insights into climate evolution in southwestern iberia the main vegetation phases identified in the guadiana valley are 1 lateglacial interstadial allerod forest with quercus and pinus under a temperate moist continental cli mate 2 a younger dryas forest decline quercus and expansion of pinewoods xeric scrub and open ground habitats with juniperus artemisia ephedra distachya type centaurea scabiosa type under arid and cold conditions 3 an early holocene forest scrub open ground vegetation mosaic developing under a warm dry and continental climate 4 a maximum of quercus forest and thermomediterranean ever green taxa olea phillyrea pistacia reflecting a warm moist oceanic climate between c 9000 cal bp and c 5000 cal bp and 5 the expansion of shrublands with cistaceae and ericaceae under a drier climatic regime and increasing anthropogenic activity since c 5000 cal bp holocene episodes of maximum cli matic aridity are identified in the record of xerophytic taxa juniperus artemisia ephedra distachya type centred around 10 200 cal bp 7800 cal bp 4800 cal bp 3100 cal bp and 1700 cal bp regional com parisons suggest a correlation of arid phases across southern iberia and northwest africa which can be related to abrupt north atlantic coolings bond events

ocean atmosphere climate shift during the mid to late holocene transition article history climate records of the mid to late holocene transition between 3 4 thousand years before present ka often exhibit a rapid change in response to the gradual change in orbital insolation here we investigate north atlantic central water circulation as a possible mechanism regulating the latitudinal temperature gradient ltg which in turn amplifies climate sensitivity to small changes in solar irradiance through this mechanism sharp climate events and transitions are the result of a positive feedback process that propagates and amplifies climate events in the north atlantic region we explore these linkages using an intermediate water temperature record reconstructed from mg ca measurements of benthic foraminifera hyalinea balthica f rom as ediment core off nw africa 889 md epth between 0t o 5 5 ka our results show that eastern north atlantic central waters enacw cooled by 1 0 7 ca nd densities decreased by 0 4 0 2b etween 3 3 and 2 6 ka this shift in enacw hydrography illustrates at ransition towards enhanced mid latitude atmospheric circulation after 2 7 ka in particular during cold events of the late holocene the presented records demonstrate the important role of enacw circulation in propagating the climate signatures of the ltg by reducing the meridional heat transfer from high to low latitudes during the transition from the holocene thermal maximum to the late holocene in addition the dynamic response of enacw circulation to the gradual climate forcing of ltgs provides a prime example of an amplifying climate feedback mechanism published by elsevier b v

time scale for adjustment of glaciers to changes in mass balance the length of time tm over which a glacier responds to a prior change in climate is investigated with reference to the linearized theory of kinematic waves and to results from numerical models we show the following tm may in general be estimated by a volume time scale describing the time required for a step change in mass balance to supply the volume difference between the initial and final steady states the factor f in the classical estimate of m l u where i is glacier length and u is terminus velocity has a simple geometrical interpretation ft is the ratio of thickness change averaged over the full length i to the change at the terminus although both u and f relate to dynamic processes local to the terminus zone the ratio f u and therefore tm are insensitive to details of the terminus dynamics in contrast to conclusions derived from some simplified kinematic wave models a more robust estimate of tm independent of terminus dynamics is given by tm h b where h is a thickness scale for the glacier and b is the mass balance rate negative at the terminus we suggest that tm for mountain glaciers can be substantially less than the 1o2 103 years commonly considered to be theoretically expected

climate change and the collapse of the akkadian empire evidence from the deep sea the akkadian empire ruled mesopotamia from the headwaters of the tigris euphrates rivers to the persian gulf during the late third millennium b c archeological evidence has shown that this highly developed civilization collapsed abruptly near 4170 150 calendar yr b p perhaps related to a shift to more arid conditions detailed paleoclimate records to test this assertion from mesopotamia are rare but changes in regional aridity are preserved in adjacent ocean basins we document holocene changes in regional aridity using mineralogic and geochemical analyses of a marine sediment core from the gulf of oman which is directly downwind of mesopotamian dust source areas and archeological sites our results document a very abrupt increase in eolian dust and mesopotamian aridity accelerator mass spectrometer radiocarbon dated to 4025 125 calendar yr b p which persisted for 300 yr radiogenic nd and sr isotope analyses confirm that the observed increase in mineral dust was derived from mesopotamian source areas geochemical correlation of volcanic ash shards between the archeological site and marine sediment record establishes a direct temporal link between mesopotamian aridification and social collapse implicating a sudden shift to more arid conditions as a key factor contributing to the collapse of the akkadian empire

ice volume changes of selected glaciers in the swiss alps since the end of the 19th century the evolution of surface topography of glaciers in the swiss alps is well documented with high resolution aerial photographs repeatedly recorded since the 1960s and further back in time with topographic maps including elevation contour lines first surveyed in the mid 19th century in order to quantify and interpret glacier changes in the swiss alps time series of volume changes over the last 100 150 years have been collected the available datasets provide a detailed spatial resolution for the retreat period since the end of the little ice age the spatial distribution as well as temporal variations of the thickness change were analyzed a significant ice loss since the end of the 19th century was observed in the ablation area while the changes in the accumulation area were small we found moderate negative secular rates until the 1960s followed by steady to positive rates for about two decades and strong ice loss starting in the 1980s which has lasted until the present an evaluation of 19 glaciers revealed a total ice volume loss of about 13 km 3 since the 1870s of which 8 7 km 3 occurred since the 1920s and 3 5 km 3 since 1980 decadal mean net balance rates for the periods 1920 60 1960 80 and 1980 present are 0 29 0 03 and 0 53 m a 1 w e respectively

paleoenvironmental implications of the insoluble microparticle record in the gisp2 greenland ice core during the rapidly changing climate of the pleistocene holocene transition oscillations in the time series of insoluble microparticle characteristics between 0 7 and 11 0 m in the greenland ice sheet project 2 gisp2 ice core reflect changes in environmental conditions in the northern hemisphere from 10 500 to 14 000 yr ago elevated values in microparticle number and mass especially during the younger dryas are related to northern hemisphere aridity and the subsequent increase in dust available for long range transport to greenland this scenario occurs with the colder climatic conditions that result from a more expanded spatially and temporally polar vortex peaks in mean grain size based on number mean number diameter are a proxy for increased strength in zonal winds westerlies highs in mean number diameter in the earlier part of the record often coincide with number and mass peaks reflecting the increased temperature and pressure gradients with an expanded polar vortex highs in mean grain size based on mass mean mass diameter reflect greater deposition of the coarser size fraction and thus are a proxy for increased storminess associated with better developed synoptic scale pressure systems in the northernmost atlantic region peaks in mean mass diameter often lead these other parameters by 100 200 yr suggesting an increase in storminess with the initial southward migration of the mean position of the polar front prior to full development of a more expanded polar vortex the general decline in number and mass trends decreased aridity with a contracting polar vortex together with increasing mean number diameter trends strengthening zonal winds following the maxima in the early younger dryas suggest an expansion of mid latitude circulation systems subtropical highs thereby maintaining latitudinal temperature and pressure gradients increased variability in mean mass diameter during the warm preboreal compared to the colder younger dryas may be a function of the greater seasonality during warmer climatic periods and thus more frequent storms associated with higher frequency oscillations in the position of the polar front with changing seasons and increased interannual variability in climate

climate variation and the rise and fall of an andean civilization paleolimnological and archaeological records that span 3500 years from lake titicaca and the surrounding bolivian peruvian altiplano demonstrate that the emergence of agriculture ca 1500 b c and the collapse of the tiwanaku civilization ca a d 1100 coincided with periods of abrupt profound climate change the timing and magnitude of climate changes are inferred from stratigraphic evidence of lake level variation recorded in14c dated lake sediment cores paleo lake levels provide estimates of drainage basin water balance archaeological evidence establishes spatial and temporal patterns of agricultural field use and abandonment prior to 1500 b c aridity in the altiplano precluded intensive agriculture during a wetter period from 1500 b c to a d 1100 the tiwanaku civilization and its immediate predecessors developed specialized agricultural methods that stimulated population growth and sustained large human settlements a prolonged drier period ca a d 1100 1400 caused declining agricultural production field abandonment and cultural collapse

effects of forest clearing on groundwater abstract groundwater systems were studied in five catchments 0 8 3 5 km2 over ten years at the end of the third year forest vegetation was totally or partially cleared in three catchments the cleared areas were sown to pasture or crop in accord with conventional agricultural practice for the region permanent aquifers were encountered within a deeply 30 m weathered regolith derived from igneous basement rocks in the higher rainfall catchment pair aquifer boundaries corresponded reasonably well with the surface divide but permanent aquifers were encountered mainly in lower parts of the three catchments in the medium rainfall areas slug test measurements of hydraulic conductivity k varied by more than a factor 100 within a catchment but there was no significant difference between the geometric mean of k in each catchment which varied between 1 4 and 7 6 mm d 1 in the higher rainfall catchments the potentiometric surface under forest normally responded by 1 4 m after each winter wet season this indicates significant seasonal recharge on the basis of the number of piezometers exhibiting this behaviour seasonal recharge was widespread in this area by contrast the seasonal response of the potentiometric surface was rarely more than 1 m under forest in the medium rainfall catchments and at many sites there was no apparent recharge in several years of this study in areas fully cleared for agriculture the potentiometric surface moved upward at more than 2 6 m yr 1 averaged over several years this was equivalent to increased recharge estimated as 6 12 of rainfall depending on the specific yield used for the aquifer the potentiometric surface was observed to rise less rapidly 0 9 m yr 1 in areas subjected to partial clearing groundwater chloride concentrations exhibit no obvious spatial pattern in the catchments probability density functions of the chloride data have similar shapes in the higher and medium rainfall catchment areas with median values of 460 and 1000 mg 1 1 respectively chloride concentrations were essentially constant with time in some piezometers while in others concentrations varied with or without trend recorded changes in time and space are not consistent with the transport equation for solute in an aquifer leading to the conclusion that local variability of solution velocity may be important this is in accord with the observed variability of hydraulic conductivity in these aquifers