dendrochronology and lichenometry colonization growth rates and dating of geomorphological events on the east side of the north patagonian icefield chile this paper highlights the importance for dating accuracy of initial studies of delay before colonization for both trees and lichens and tree age below core height particularly in recently deglaciated terrain where colonization and growth rates may vary widely due to differences in micro environment it demonstrates for the first time how dendrochronology and lichenometry can be used together in an assessment of each other s colonization and growth rates and then cross correlated to provide a supportive dating framework the method described for estimating tree age below core height is also new the results show that on the east side of the north patagonian icefield in the arco and colonia valleys nothofagus age below a core height of 112 cm can vary from 5 to 41 years and delay before colonization may range from a maximum of 22 years near water to a minimum of 93 years on the exposed flanks of the arenales and colonia glaciers tree age plus colonization delay supplied a maximum growth rate of 4 7 mm year for the lichen placopsis perrugosa and lichen colonization is estimated to take from 2 5 to approximately 13 years a minimum lichenometric date of 1883 was estimated for an ice formed trimline at the junction of the arenales and colonia glaciers and a maximum dendrochronological date of 1881 for a water formed trimline in the arco valley tree and lichen ages around the valley suggest that a glacial outburst drained the 1881 high level lake releasing approximately 265 million cubic metres of water repeated flooding with a minimum of 38 high lake levels is suggested by horizontal sediment lines on the arco valley walls and moraine flanks dating confirmed diminishing flood levels with a last minor flood in 1963 the wider significance of the work is that it should produce more accurate dating of recent glacier fluctuations around the north patagonia icefield an area where dated reference surfaces are extremely scarce

a debris flow calendar derived from sediments of lake lago di braies n italy abstract in this study lake sediments were used for developing a high resolution calendar of past debris flow events debris flows frequently occur in the high alpine catchment of the lake lago di braies n italy while the coarse grained material accumulates on the debris flow cones the fine grained material is flushed into the lake this material forms characteristic layers in the lake sediments which are different from the typical annual lamination by analysing thin sections of sediment debris flow events of the last 2250 years were reconstructed with an annual resolution since debris flow frequency varies strongly periods with high and low frequencies can be distinguished however neither a debris flow magnitude frequency relationship nor a strong reaction of debris flow activity to past climate changes was identifiable in this study

soil endemism and its relation to soil formation theory abstract in this paper the concept of soil endemism is elucidated endemic soils are restricted to a particular geographic area based on a unique combination of soil forming factors that may operate from the landscape to the eco region scale to validate that soils are endemic soil bodies occurring on different continents but having a similar combination of soil forming factors were compared using national soil survey characterization data a key finding is that similar soil families occur within a given climate class koppen trewartha system and vegetation type bailey s eco region division reinforcing the former concept of zonal soils in a second test soil series were compared within a soil family from randomly selected benchmark soil series using the state soil geographic statsgo database and evaluated in terms of the soil forming factors contributing to endemism this analysis showed that soil endemism is locally influenced by parent material e g volcanic ash clay secondary silica and topography e g closed basins i e intrazonal soils soils lacking a well developed profile because of youth of parent material or peculiar conditions of parent material or relief azonal soils do not show endemism therefore zonal and intrazonal soils generally are endemic and azonal soils tend to be non endemic the concept of endemism is important for detecting rare unique or endangered soils

lichenometric dating using rhizocarpon subgenus rhizocarpon in the patagonian andes argentina abstract this study represents the first attempt to develop and apply lichenometric dating curves of rhizocarpon subgenus rhizocarpon for dating glacier fluctuations in the patagonian andes six glaciers were studied along the patagonian andes surfaces of known ages historical evidences and tree ring analyses were used as control sites to develop indirect lichenometric dating curves dating curves developed for the studied glaciers show the same general logarithmic form indicating that growth rate of subgenus rhizocarpon decreases over time the strong west east precipitation gradient across the andean cordillera introduces statistically significant differences in the growth curves with faster growth rates in the moist west sites than the drier eastern sites latitudinal difference among the studied glaciers does not appear to be a major factor regulating lichen growth rates therefore we developed two lichenometric curves for dating glacier fluctuations in wetter and drier sites in the patagonian andes during the past 450 yrs application of the developed curves to moraine dating allowed us to complement glacial chronologies previously obtained by tree ring analyses a first chronosequence for moraine formation in the torrecillas glacier 42 s is presented our findings confirm the utility of lichenometry to date deglaciated surfaces in the patagonian andes

soils with fragipans in the usa abstract fragipans are dense subsurface soil layers that severely restrict water flow and root penetration they are considered a pedogenic horizon but their exact genesis is not well understood in soil taxonomy 2010 a fragipan is defined as a layer that is at least 15 cm thick contains a coarse structure and is reversibly cemented we examined 362 pedons with fragipans in the natural resources conservation service nrcs ssurgo database and 36 case studies in the usa from the literature soils with fragipans are classified primarily at the great group but also at the subgroup level fragipans occur in four orders alfisols ultisols inceptisols spodosols 10 suborders 23 great groups and 57 subgroups from the nrcs database fragipan soils have silty or loamy particle size classes 95 of total soil series an udic or aquic soil moisture regime 98 a mesic soil temperature regime 60 and a mixed mineralogy class 75 of total soil series although they occur in 28 states in the usa the most extensive areas of soils with fragipans occur in the southern mississippi river valley and the central and southern appalachian mountains soils with fragipans are most common east of the 97 w meridian and in forested areas where precipitation exceeds evaporation these soils are derived from silt rich materials especially loess and low lime tills 61 of total soil series and occur primarily in lower moderately well drained topographic positions the genesis of fragipans involves wetting and drying possibly influenced by the presence of lithologic discontinuities which lead to hydro consolidation that causes close packing of grains and reduces porosity although silica may bind clays and fe oxides and bridge skeletal grains this property is not recognized in the definition of the fragipan in the conterminous usa soil mapping units containing soils with fragipans occupy 970 000 km 2 12 of the land area

topographic controls on glacier sediment landform associations around the temperate north patagonian icefield topographic controls on glacier sediment landform associations around the temperate north patagonian icefield

gulf of mexico circulation within a high resolution numerical simulation of the north atlantic ocean 1 the gulf of mexico circulation is examined from the results of a high resolution 1 12 north atlantic simulation using the miami isopycnic coordinate ocean model the motivation for this paper is twofold first we validate the model s performance in the gulf of mexico by comparing the model fields to past and recent observations and second given the good agreement with the observed gulf of mexico surface circulation and loop current variability we expand the discussion and analysis of the model circulation to areas that have not been extensively observed analyzed such as the vertical structure of the loop current and associated eddies especially the deep circulation below 1500 m the interval between successive model eddy sheddings is 3 to 15 months the eddy diameters range between 140 and 500 km the life span is about 1 year and the translational speeds are 2 3 km d 1 in good agreement with observations areas of high cyclonic eddy occurrence in the model are southwest of florida the loop current boundary and the western campeche bay area the cyclonic eddy diameters range between 50 and 375 km the orbital speeds range between 1 and 55 cm s 1 the translational speeds range between 0 5 and 14 km d 1 and the eddy life spans range between 1 and 3 months the vertical structure of the temperature and salinity of each modeled eddy from the moment it is shed until it disintegrates in the western gulf of mexico is in agreement with the few available observations below 1500 m deep cyclonic eddies are associated with the surface loop current anticyclones the eddy variability is consistent with rossby waves propagating westward and there is bottom intensification of the flow close to steep topography overall we show that this very high horizontal resolution isopycnic coordinate ocean model which is able to produce a quite realistic surface circulation for the north and equatorial atlantic is also able to reproduce well the smaller scale basin wide intricate dynamics such as the gulf of mexico variability

spatial soil variability in the cajon pass chronosequence implications for the use of soils as a geochronological tool abstract spatial variation of soil properties on a single geomorphic surface has a significant influence on surface correlations and age determinations made on the basis of soil properties few chronosequence studies have been based on a sufficient number of soils to evaluate the influence of soil variability we described and evaluate 35 soils on four terrace surfaces which constitute part of a previously described well dated soil chronosequence in cajon pass in southern california soils were described on both bar and swale sites removed from the influence of deposition adjacent slopes the influence of eolian silt on the rate of pedogenesis in cajon pass indicates that this sequence of soils cannot be considered a chronosequence in the strict sense of the term furthermore the evidence for a pedogenic threshold in these soils indicates that the soils do not develop monotonically with time and that soil development cannot be defined by a continuous univariant chronofunction the discrete nature of the data from a chronosequence and the complex nature of soil development are better analyzed by multivariate statistical procedures systematic variation in soil properties between soils from bar sites and soils from swale sites is attributed to geomorphic processes which affect either the rate or duration of eolian dust accumulation soils from bar sites were less variable and generally less strongly developed that soils from swale sites from the same surface the degree of variation of soil properties determined for a given landscape position on a surface is sufficient to raise questions concerning the usefulness of chronofunctions for determining the nature of time dependent pedogenic changes and for providing numerical age determinations multivariate statistical methods were used to differentiate among soils developed on three surfaces which differ in age by only 1500 years

geomorphological evidence for variations of the north patagonian icefield during the holocene abstract elucidating the timing and extent of former glacier fluctuations is important because of the palaeoclimatic inferences that can be drawn from such studies here we present new geomorphological evidence of the patterns of glacier behaviour around the north patagonian icefield during the holocene mapping is based on visual interpretation of landsat 7 etm and terra aster satellite images including the contemporary glaciers areas of ice scoured bedrock trimlines glacial lineations terminal moraines sandur and fluvial sediments deltas and ice contact deposits and alluvial fans recession of the icefield is marked by three distinct moraine sets these moraine sets are interpreted as marking terminal positions related to the little ice age and two preceding but as yet undated phases of holocene glacier expansion large arcuate terminal moraines in front of three of the western glaciers are interpreted as composite features reflecting topographic limits to glacier expansion indicating that caution is required in the interpretation of previous 14c dates obtained from these moraines there are strong contrasts in the patterns of glacier behaviour between the east and west sides of the north patagonian icefield which cannot be attributed simply to an east west differential in the rates of change of atmospheric temperature and precipitation we argue here that glacier response to first order climate forcing is tempered by second order controls introduced by regional scale topographic effects notably glacier drainage basin extent and area topographic controls on glacier snout morphology and differences in terminal environment calving non calving during glacier recession

rates of soil development from four soil chronosequences in the southern great basin abstract four soil chronosequences in the southern great basin were examined in order to study and quantify soil development during the quaternary soils of all four areas are developed in gravelly alluvial fans in semiarid climates with 8 to 40 cm mean annual precipitation lithologies of alluvium are granite gneiss at silver lake granite and basalt at cima volcanic field limestone at kyle canyon and siliceous volcanic rocks at fortymile wash ages of the soils are approximated from several radiometric and experimental techniques and rates are assessed using a conservative mathematical approach average rates for holocene soils at silver lake are about 10 times higher than for pleistocene soils at kyle canyon and fortymile wash based on limited age control holocene soils in all four areas appear to develop at similar rates and pleistocene soils at kyle canyon and fortymile wash may differ by only a factor of 2 to 4 over time spans of several millennia a preferred model for the age curves is not linear but may be exponential or parabolic in which rates decrease with increasing age these preliminary results imply that the geographical variation in rates within the southern great basin mojave region may be much less significant than temporal variation in rates of soil development the reasons for temporal variation in rates and processes of soil development are complexly linked to climatic change and related changes in water and dust erosional history and internally driven chemical and physical processes

dynamics of agulhas retroflection and ring formation in a numerical model part ii energetics and ring formation abstract an energetics analysis of several numerical experiments on an idealized south atlantic indian ocean basin is presented the model used in the experiments is the quasi isopycnic coordinate model of bleck and boundra forced by wind and configured with two or three layers the region of focus is the most dynamically active one the agulhas current retroflection south of africa and the dynamical mechanisms associated with formation of agulhas rings are given special attention whether rings form in the model and their frequency depend on two primary factors the shape of africa and southward inertia baroclinicity in the overshooting agulhas the boundary condition on africa no slip free slip and horizontal resolution are also important experiments in which rings form exhibit considerably larger values of km to ke transfer than those in which no rings form in three of the experiments ring formation is studied in detail with the help of instantaneous top and bottom layer flow patterns and time se

distribution and classification of soils with clay enriched horizons in the usa article i nfo article history in soil taxonomy three diagnostic subsurface horizons reflect clay enrichment the argillic kandic and natric horizons clay illuviation is recognized in soil taxonomy at some level in 10 of the 12 orders including the order alfisols ultisols suborder aridisols great group aridisols gelisols mollisols oxisols vertisols and subgroup andisols aridisols inceptisols mollisols oxisols spodosols forty four percent of the soil series in the usa contain taxonomically defined clay enriched horizons however many other soils contain bt horizons that do not qualify as an argillic or related horizons several soil forming factors are important in their development including udic and ustic soil climates lithological discontinuities parent materials enriched in carbonate free clays and coarse fragments well drained conditions backslopes rather than eroding shoulders and a time interval of n2000 yr or more the genesis of argillic kandic and natric horizons is also dependent on electrolyte concentration the amount and distribution of precipitation clay charge and microfabric

evidence from the rio bayo valley on the extent of the north patagonian icefield during the late pleistocene holocene transition abstract this paper presents data on the extent of the north patagonian icefield during the late pleistocene holocene transition using cosmogenic nuclide exposure age and optically stimulated luminescence dating we describe geomorphological and geochronological evidence for glacier extent in one of the major valleys surrounding the north patagonian icefield the rio bayo valley geomorphological mapping provides evidence for the existence of two types of former ice masses in this area i a large outlet glacier of the north patagonian icefield which occupied the main rio bayo valley and ii a number of small glaciers that developed in cirques on the slopes of the mountains surrounding the valley cosmogenic nuclide exposure age dating of two erratic boulders on the floor of the rio bayo valley indicate that the outlet glacier of the icefield withdrew from the rio bayo valley after 10 900 1000 yr the mean of two boulders dated to 11 400 900 yr and 10 500 800 yr single grain optically stimulated luminescence osl dating of an ice contact landform constructed against this glacier indicates that this ice mass remained in the valley until at least 9700 700 yr the agreement between the two independent dating techniques osl and cosmogenic nuclide exposure age dating increases our confidence in these age estimates a date obtained from a boulder on a cirque moraine above the main valley indicates that glaciers advanced in cirques surrounding the icefield some time around 12 500 900 yr this evidence for an expanded north patagonian icefield between 10 900 1000 yr and 9700 700 yr implies cold climatic conditions dominated at this time

is there a continuous subtropical front south of africa a 14 3 year series of weekly absolute sea surface height ssh and associated geostrophic velocities is used for a study of the subtropical to subantarctic frontal system in the region south of africa detecting the fronts from surface velocity maxima confirms a two stepped transition in both the southeastern atlantic ocean the northern and southern subtropical fronts nstf sstf and southwestern indian ocean the agulhas front and sstf as proposed previously from hydrographic data an additional front associated with westward flow north of the nstf is indicative of a partial eastern closure of the south atlantic subtropical gyre between 11 e and 17 5 e the role of northwestward propagating agulhas rings in connecting the two fronts explains the varying location the sstf which marks the southern limit of subtropical waters is found continuous from the atlantic to the indian ocean in the time averaged ssh field in the weekly fields however the velocity maximum criterion defining the front is often met at the southern flanks of agulhas rings or agulhas eddies at 12 e 23 e indicating front disruptions such discontinuities suggest that no south atlantic central water is directly advected into the indian ocean instead the eastward limb of the indo atlantic super gyre encompassing the subtropical gyres of both oceans would rest at these longitudes on diffusive processes at the upper levels and possibly be enhanced at depth a schematic diagram of the fronts and their relations to agulhas rings and eddies is proposed

classic and new dating methods for assessing the temporal occurrence of mass movements abstract establishing landslide chronologies is essential both for understanding causes of mass movements as part of fundamental geomorphological research and for the assessment of landslide hazards as part of applied geomorphology we discuss the applicability of different methods for determining landslide chronologies frequencies and dynamics in relation to the type of material being dated sampling location and type of mass movement the emphasis is on the possibilities and limitations of the different dating methods established methods such as radiocarbon dating lichenometry and dendrochronology are briefly discussed the paper focuses however on 1 new analytical techniques like accelerator mass spectrometry ams thermally ionising mass spectrometry tims and laser fusion which have led to significant improvements of established dating methods and on 2 new dating methods like optically stimulated luminescence osl dating and alpha recoil track art dating

buoyancy driven lacustrine calving glaciar nef chilean patagonia glaciar nef a 164 km 2 eastern outlet of hielo patagonico norte the northern patagonia icefield terminates in a proglacial lake that has formed in conjunction with 20th century glacier retreat the terminus is inferred to be transiently afloat a hinge calving mechanism is proposed in which buoyant forces impose a torque on the glacier tongue resulting in the release of coherent sections of the glacier tongue as tabular icebergs a simple model shows how torque and tensile stress reach a maximum at the up glacier limit of the buoyant zone and that glacier thinning causes this point to migrate up glacier empirical evidence supporting this model includes elevated thermo erosional notches 6 5 m above lake level and the ubiquitous presence since 1975 of tabular icebergs with surface areas 0 3 km 2 flow speeds of 1 2 1 3 m d 1 were measured near the terminus in february 1998 extrapolations from these short term data yield a calving rate of 785 835 m a 1 and a calving flux of 232 10 6 m 3 a 1 or 0 2 km 3 a 1 the calculated mean water depth at the terminus is 190 m this calving rate is higher than at grounded temperate glaciers calving in fresh water but is nevertheless almost an order of magnitude less than calving rates at both grounded and floating tidewater glaciers

a glacial lake outburst flood associated with recent mountain glacier retreat patagonian andes harrison s glasser n f winchester v haresign e warren c jansson k 2006 a glacial lake outburst flood associated with recent mountain glacier retreat patagonian andes the holocene 16 4 pp 611 620 sponsorship nerc grant ner b s 2002 00282 carnegie trust for the universities of scotland

latest pleistocene and holocene glacial events in the colonia valley northern patagonia icefield southern chile the northern patagonia icefield npi is the primary glaciated terrain worldwide at its latitude 46 5 47 5 s and constraining its glacial history provides unique information for reconstructing southern hemisphere paleoclimate the colonia glacier is the largest outlet glacier draining the eastern npi ages were determined using dendrochronology lichenometry radiocarbon cosmogenic 10be and optically stimulated luminescence dated moraines in the colonia valley defined advances at 13 2 0 95 11 0 0 47 and 4 96 0 21 ka with the last being the first constraint on the onset of neoglaciation for the eastern npi from a directly dated landform dating in the tributary cachet valley which contains an ice dammed lake during periods of colonia glacier expansion defined an advance at ca 2 95 0 21 ka periods of advancement at 810 49 cal a bp and 245 13 cal a bp and retreat during the intervening periods recent colonia glacier thinning which began in the late 1800s opened a lower elevation outlet channel for lago cachet dos in ca 1960 our data provide the most comprehensive set of latest pleistocene and holocene ages for a single npi outlet glacier and expand previously developed npi glacial chronologies

agulhas ring formation as a barotropic instability of the retroflection 1 agulhas leakage is an important link in the global ocean circulation as it transfers a significant volume of relatively warm and salty water from the indian ocean to the atlantic ocean the main route of this transfer is through the shedding of large agulhas rings from the agulhas retroflection in this paper we study the dynamics of the ring formation process by analyzing the stability of the indian atlantic supergyre in a reduced gravity model we show that the ring shedding process results from a barotropic instability of the steady circulation in the agulhas retroflection region the destabilizing mode appears to be linked to a rossby basin mode of the combined south indian atlantic basin which is localized in the retroflection region by the background flow

an advance of soler glacier north patagonian icefield at c ad 1222 1342 soler glacier is a temperate outlet glacier on the eastern side of the north patagonian icee eld in chile the glacier is currently receding from its little ice age maximum position attained sometime between ad 1600 and 1900 across the snout and foree eld of the glacier is an arcuate belt of well sorted granule gravel and coarse sand containing tree remains these sediments are interpreted as reworked glaciolacustrine material elevated to the glacier surface by thrusting and folding radiocarbon dating of samples of tree remains in these reworked glaciolacustrine sediments demonstrates that the glacier overrode this lake bed sometime between ad 904 and ad 1334 in situ tree remains plastered onto a large boulder in front of the glacier constrain this advance to the period between ad 1222 and ad 1342 this advance precedes by several hundred years the maximum little ice age extent of other north patagonian icee eld outlet glaciers suggesting either an early age for the onset of little ice age conditions or a previously unrecognized period of glacier advance prior to the advance at c ad 1222 to ad 1342 soler glacier was more recessed than at present cone rming the dynamic response of patagonian glaciers to holocene climatic e uctuations

soil forming processes and rates on uplifted marine terraces in southwestern oregon usa soil chronosequences were examined on flights of tectonically uplifted marine terraces near cape blanco and cape arago southwestern oregon all of the soils contain abundant organic c and are strongly acidic ph in h2o 30 of the exchange sites saturated with al the soils in the two areas show a progression in development from spodosols to spodosols with clay enriched horizons and eventually to ultisols although the spodic and argillic horizons appear to be forming concurrently in the soils evidence is presented to support the concept that the spodic horizon is eventually masked by clay accumulation because of weathering in situ neoformation of clays and clay translocation the primary age related trends include increases in 1 the relative abundance of silt and clay 2 the ratio of quartz to feldspars in the very fine sand 100 50 m fraction and 3 the amounts of dithionite extractable fe and al and crystalline forms of fe in the profile

limits to lichenometry abstract lichenometry is a straightforward and inexpensive method for dating holocene rock surfaces the rationale is that the diameter of the largest lichen scales with the age of the originally fresh rock surface that it colonised the success of the method depends on finding the largest lichen diameters a suitable lichen growth model and a robust calibration curve recent critique of the method motivates us to revisit the accuracy and uncertainties of lichenometry specifically we test how well lichenometry is capable of resolving the ages of different lobes of large active rock glaciers in the kyrgyz tien shan we use a bootstrapped quantile regression to calibrate local growth curves of xanthoria elegans aspicilia tianshanica and rhizocarpon geographicum and report a nonlinear decrease in dating accuracy with increasing lichen diameter a bayesian type of an analysis of variance demonstrates that our calibration allows discriminating credibly between rock glacier lobes of different ages despite the uncertainties tied to sample size and correctly identifying the largest lichen thalli our results also show that calibration error grows with lichen size so that the separability of rock glacier lobes of different ages decreases while the tendency to assign coeval ages increases the abundant young

a comparison of mineralogical techniques and potassium adsorption isotherm analysis for relative dating and correlation of late quaternary soil chronosequences abstract the utility of potassium adsorption isotherm analysis kia for relative dating and correlation of soil chronosequences was assessed by a comparison with some widely used mineralogical techniques the soils studied near detroit michigan are brown 10yr calcareous entisols developed in holocene 4 ka floodplain sediments and inceptisols and alfisols with redder 7 5yr 5yr cambic and argillic b horizons formed on late pleistocene 14 5 12 4 ka fluvial terraces fluvial paleochannels and paleoshorelines beach ridges of proglacial lakes the soils show a positive linear correlation between soil age and clay content depth of carbonate leaching and fe oxide accumulation in contrast the duration of soil formation is too short for variations in heavy mineral frequencies to discriminate soil age reliably scanning electron microscopy shows that chemical weathering stage is indicated by progressive etching and pitting of calcite apatite and amphibole with increasing soil age k isotherms are linear or slightly curvilinear indicating that ion exchange is dominant over specific adsorption a statistically significant linear correlation between k distribution constant and soil age attributed to progressive weathering of mica suggests that kia is useful for relative dating of genetically related soils once a well dated chronosequence is established kia produces results comparable to or better than mineralogical techniques however soil morphology and a clay redness index are more effective than mineralogical and chemical techniques for interchronosequence correlation

motion and evolution of oceanic rings in a numerical model and in observations observed properties of oceanic rings are compared to rings produced in a two gyre wind driven numerical ocean model and in a model of the south atlantic indian ocean their temporal evolution is discussed in terms of structure and translation rate they exhibit substantial similarity in terms of thermocline depth ring size swirl velocities and translations speeds in both observations and numerical model results the propagation speeds are 2 to 5 times faster than that of an equivalent isolated eddy which is of the order of the long rossby wave speed this is attributed to advection by the mean flows furthermore it is observed that the model rings have a coherent structure all the way to the bottom there is strong evidence that this is also the case in real oceanic rings one major difference between observed and modeled rings is in their decay rate the temporal decay of the rings in the models and observations is therefore discussed in relation to the decay mechanisms at work and the frictional parameterization of the model

classification and distribution of soils with albic horizons in the usa a preliminary analysis abstract the albic horizon a diagnostic subsurface horizon that is comprised of primary sand and silt particles that are light colored because they lack clay or iron oxide coatings is unique in that it is an eluvial horizon that is defined on the basis of a loss rather than a gain of weathering products over 3000 official soil descriptions were examined in the us natural resources conservation service databases to identify which taxa contain albic horizons albic horizons are present i e more than 8 soil series in seven orders 28 suborders 73 great groups and about 1600 soil series in soil taxonomy orders with albic horizons can be ranked on an area basis alfisols spodosols ultisols mollisols inceptisols entisols aridisols the mean thickness of the albic horizon is 19 cm with the greatest thickness in alorthods 90 cm and the least in xerolls 3 1 humods 4 0 and ustolls 5 6 cm albic horizons may occupy one or two of several positions in the soil profile including i the mineral soil surface ii below an a horizon iii as a buried horizon iv between a variety of diagnostic subsurface horizons in bisequal soils and v in some soils with alternating e and bt lamellae albic horizons separate or are underlain mainly by an argillic or a spodic horizon half 50 of the soils with albic horizons are excessively to well drained many albic horizons have been lost due to cultivation especially in aqualfs udalfs and udults

historical fluctuations of the gualas and reicher glaciers north patagonian icefield chile dendrochronology was used to date historical fluctuations of the little visited gualas and reicher glaciers on the north patagonian icefield in southern chile vegetation trimlines dating to ad 1876 1909 and 1954 show that glacier downwasting and retreat mirrored the patterns found at the neighbouring san rafael and san quintin glaciers intermediate stages of recession of the gualas and reicher glaciers dating to the early 1920s mid 1930s and 1960s are also reflected by similar stages in the san rafael and san quintin glaciers we propose that the common responses shown by these four glaciers argue for climatic control of their movements and that glacier dynamics in this region are principally controlled by changes in precipitation rather than temperature since annual mean temperatures at cabo raper the nearest meteorological station have shown no trend since the early 1940s whereas precipitation peaking in the winter months has varied widely since the 1920s

diversity of diagnostic horizons in soils of the contiguous usa a case study abstract many previous studies of pedodiversity have emphasized the lateral variability of soils in this study the vertical distribution of diagnostic horizons is examined at the soil series level unlike genetic horizons diagnostic soil horizons are based on quantitatively defined morphological and analytical properties and they form the basis of modern soil classification systems an examination of 1600 soil series in 63 representative out of 226 major land resource areas mlras in contiguous usa revealed that they contain from one to seven diagnostic soil horizons with an average of 2 6 1 2 about 20 of the soil series contain 4 or more diagnostic horizons 80 of these soil series are in seven great groups the glossudalfs haplorthods fragiorthods endoaquods epiaquods fraglossudalfs and glossaqualfs the laurentide great lakes region contains a discordant number 57 of soils with 4 or more diagnostic horizons the most common being ochric 100 albic 91 argillic 85 glossic 69 spodic 51 and a fragipan 19 several factors appear to contribute to the diversity of diagnostic horizons including proximity to the great lakes where abundant snowfall precludes soil freezing and enables water to percolate rapidly through the soil in a short interval during the spring the prevalence of stratified glacial deposits often containing a lithologic discontinuity and a fluctuating water table all of which enable specific weathering products to accumulate at different depths

lichen dating of earthquake generated regional rockfall events southern alps new zealand synchronous regional rockfall events triggered by large earthquakes in the southern alps of new zealand were used to evaluate and improve the lichenometry method for surface exposure dating digital calipers were used to measure the maximum diameter of the largest lichen on many rockfall blocks using a fixed area largest lichen fall sampling strategy regional significance of fall peaks can be tested by confirming the occurrence of a coeval peak at multiple sites and by showing an increase in peak size toward the earthquake epicenter significance of fall peaks at a local site can be described in terms of peak size relative to a uniform density of fall sizes measurements of 34 000 fall sizes on fully exposed rockfall blocks and outcrop joint faces at 90 sites allow precise dating of geomorphic events of the past 300 to 500 yr uncertainties at the 95 confidence interval can be reduced to a level better than 10 yr for ages within the calibrated time range represented by the lichen growth equation recognition of prehistorical regional rockfall events in 1833 1836 and 1840 demonstrates the excellent resolution of this dating method precise dates result from exceptionally low measurement errors of lichen sizes relative to their growth rate tightly clustered fall sizes for earthquake induced rockfall events and substrate exposure times for calibration sites that are known to the year or day fall peaks for synchronous rockfall events are the same for 20 sites with diverse climate altitude and substrate lithology a regionally consistent lichen growth rate allows use of a single growth rate equation for most species of rhizocarpon subgenus rhizocarpon on the south island of new zealand a nonlinear growth equation suggests that the first colonization on average occurs in the 5th yr after formation of new rock surfaces 0 5 m 2 unit areas and is followed by rapid exponentially declining growth for about 20 yr greatgrowth phase that is largely completed by the 24th yr then linear growth persists at about 15 mm per century uniform growth phase

lichenometric dating of slope movements nant ffrancon north wales abstract over the last 50 years frequent debris flows on the oversteepened slopes crossed by the main a5 road in nant ffrancon north wales have presented a significant traffic hazard this study uses two approaches to lichenometry to date earlier debris flows the first approach provides dating estimates based on size age correlations of the lichen rhizocarpon geographicum subspecies prospectans growing in two local churchyards the correlations supplied a growth rate of 1 47 mm year 1 for the species over a 140 year period with a delay before colonization of 18 years remeasurement of the same lichens after a 4 25 year interval confirmed the growth and colonization rates in the churchyards the second lichenometric approach based on population size frequency distributions with size increments dated using the churchyard growth rate provided controls for the nant ffrancon study site with peaks in rhizocarpon population size frequency distributions correlating with debris flow dates recorded by gwynedd council highways department circumstantial evidence supporting adoption of the growth rate on the nant ffrancon slopes was also supplied by data from archival and meteorological sources the lichenometric dating estimates suggest that these slopes have a history of periodic debris flows covering at least the last 110 years with major flows occurring in the 1890s followed by further flows in the early decades of the twentieth century

a quantitative comparison of soil development in four climatic regimes abstract a new quantitative soil development index based on field data has been applied to chronosequences formed under different climatic regimes the four soil chronosequences developed primarily on sandy deposits have some numeric age control and are located in xeric inland merced calif xeric coastal ventura calif aridic las cruces n mex and udic susquehanna valley pa soil moisture regimes to quantify field properties points are assigned for developmental increases in soil properties in comparison to the parent material currently ten soil field properties are quantified and normalized for each horizon in a given chronosequence including two new properties for carbonate rich soils in addition to the eight properties previously defined when individual properties or the combined indexes are plotted as a function of numeric age rates of soil development can be compared in different climates the results demonstrate that 1 the soil development index can be applied to very different soil types 2 many field properties develop systematically in different climatic regimes 3 certain properties appear to have similar rates of development in different climates and 4 the profile index that combines different field properties increases significantly with age and appears to develop at similar rates in different climates the soil development index can serve as a preliminary guide to soil age where other age control is lacking and can be used to correlate deposits of different geographical and climatic regions

a soil chronosequence on quaternary marine terraces san clemente island california a soil chronosequence on marine terraces was examined on san clemente island california in an arid mediterranean climate in order to see which soil properties differ most systematically with time ages of the geomorphic surfaces were determined by radiocarbon uranium series and amino acid racemization techniques and range from 1 000 000 yrs soils on surfaces 200 000 yrs old are vertisols or alfisols with vertic properties such as slickensides and cracks and they exhibit both prismatic and angular blocky sphenoidal or only angular blocky structure solum thickness increases linearly with age of geomorphic surface clay soluble salts ald smectite mica ratios in the clay fraction and quartz plagioclase ratios in the silt fraction when expressed as profile summations show increases with age of geomorphic surface the best fit regression equations are linear with the exception of ald which is best expressed as a power function important soilforming processes appear to be alteration of mica to smectite accumulation at depth of soluble salts derived from marine aerosols possibly additions of eolian materials clay illuviation in the younger soils and pedoturbation in the older soils the observations reported here allow the following conclusions to be drawn about soils in this environment 1 certain soil properties which show distinct trends with time can be used for relative age dating in geomorphic and stratigraphic studies 2 soils have not reached a steady state condition with respect to many of their properties and 3 alfisols and mollisols with natric b horizons may be precursors to vertisols

a development of the lichenometric method applied to the dating of glacially influenced debris flows in southern chile lichenometry is a dating technique that has problems relating to questionable assumptions the development of a size frequency approach previously used in attempts to resolve some of the problems is described and applied to the dating of four debris flows marginal to the san rafael glacier in southern chile this study provides examples of the development s application its problems and directions for further work the size frequency approach based on new assumptions uses parameters derived from population size frequency distributions of the lichen species placopsis patagonica to provide relative and absolute dating for rock surfaces changes in the shapes of distributions suggest the relative age of populations absolute dating is based on a curve spanning a 24 year time period derived from mean diameter size age correlations a stratified random sampling design permits the use of inferential statistics standard deviations and confidence intervals show error margins the degree of relatedness between neighbouring populations and populations that are anomalous one way analysis of variance is used to indicate where populations may safely be grouped the size frequency approach appears to be particularly suitable for use on unstable debris flows where secondary movements are common the approach also demonstrates that lichen growth and colonization are sensitive to aspect differences and other variations in microhabitat

little ice age glacier fluctuations gran campo nevado southernmost chile moraine systems of glaciar lengua unofficial name and neighbouring glaciers of gran campo nevado 53 s in the southernmost andes were mapped and dated by dendrochronological means they were formed around ad 1628 1872 1875 1886 1902 1912 and 1941 with the advance in the 1870s being calendar dated recessional moraines within each moraine system correspond to brief standstills or minor readvances a significantly older moraine could not be directly dated by dendrochronological methods as the forest on it was assumed to be second generation or older from soil formation rates it is assumed that this moraine was formed at some time between ad 1280 and 1460 a time in which many other glaciers in patagonia formed moraines overall fluctuations of glaciar lengua show a strong synchronicity to other glaciers in the patagonian andes between 41 s and 55 s this study suggests that glaciar lengua and possibly all glaciers of gran campo nevado reached their holocene maximum during the little ice age

three dimensional gis cartography applied to the study of the spatial variation of soil horizons in a swiss floodplain abstract in this study we propose to establish a framework for the study of the spatial variability of the soils found in the floodplain of the sarine river and for the visualisation of soil distribution patterns in two and three dimensions 2 d 3 d this environment is characterised by a large lateral and vertical spatial variability of soils that corresponds to the temporal and spatial variations of the fluvial dynamics of the sarine the study was carried out using existing geographical information system gis functions combined with applications specific to soil cartography this particular gis cartography is based on the notion of the soil horizon instead of that of the soil diagnostic profile a global positioning system gps survey was carried out in order to construct a local digital elevation model dem and to ascertain the spatial coordinates for each of the 181 soil obsevation locations all data were stored in a gis database and both landform modeling and soil cartography was undertaken gis arc info and vertical mapper for mapinfo were adequate for our linear triangulation interpolation for contour processing and for the creation of cross sections as well as the corresponding vertical profiles these vertical profiles served to illustrate the superposition of soil horizons along any line across the sampled area a 3 d representation of soil was obtained using the quadratic finite element method which is generally employed in geological studies and which we adapted especially for the representation of soil horizons 3 d cartography of this type allows the spatial pattern of a given horizon including the variation of its thickness the superimposition of the different soil horizons the total soil depth and the number of horizons at any given location to be followed through space our approach furthermore facilitates the perception of soil horizons and their juxtarelationships as 3 d objects and permits the visualisation of the relationships that exist between any given horizon or sequence of horizons and the surface topography in thus enabling the realistic representation and easy visualisation of the spatial distribution and variability of soils in the landscape our methodological approach provides a powerful instrument for soil scientists and a useful decision support tool for ecosystem management

rings in the ocean certain robust long lived eddy features in t he world s ocean have come to be k nown as rings the nomenclature stems from fuglister 1 1972 who c oined t he name based on the c ircle or ring of gulf stream waters t hat surrounded a class of eddies formed from t he g ulf stream through the pinch off of meanders here it s uffices to define rings as intense eddies or vortices that represent a wrapped up piece of a major ocean c urrent they t ranslate over space scales of hundreds to thousands of k ilometers and exist for periods lasting from months to years rings move t hrough the ocean carrying anomalies s imilar to the contrasts in physical biological and chemical properties observed across the major ocean c urrents while the term ring is t ied to fuglister t he existence ofthese features was evident at least as early as t he 1930s when iselin 2 1936 1940 encountered strong cold anomalies in the region south of the gulf stream that we would identify as c old corc cyclonic rings today iselin fully rec ognized these features as part of the highly time dependent eddy motion in the ocean later iselin fuglister 1948 were the first to survey what is now k nown as a warm core anticyc lonic ring there are tw o types of rings cold core rings are made up of w aters from the poleward s ide of c urrents like the gulf stream that are introduced to

resolving the integral connection between pedogenesis and landscape evolution abstract soil is central in the terrestrial ecosystem linking and providing feedback responses to the other components i e water atmosphere and vegetation however the role of soil in landscape evolution is usually not well acknowledged in modeling landscape evolution soil is only treated as a residue of weathering that is transported and redistributed along the hillslope weathering is considered as a process that produces clays and generates unconsolidated materials available for erosion while pedology has been debating the form of qualitative factorial models for 75 years models for soil water heat solute gas and chemical reactions in a profile have matured as soils are distributed continuously in three dimensions across landscapes the profile models need to consider lateral fluxes this review outlines the role of soil in landscape modeling first we review the role of soil in the current landscape evolution models we then review data and models on soil weathering rates and transport processes we discuss soil profile models that simulate soil formation processes and combined soil landscape evolution models finally we discuss how the models can be tested and validated in the real world and suggest how both soil scientists and landscape modelers can work together to address the grand challenges in modeling earth surface processes

making use of the world reference base diagnostic horizons for the systematic description of the soil continuum application to the tropical mountain soil landscape of southern ecuador abstract the world reference base for soil resources wrb fao iuss working group wrb 2007 at present does not acknowledge the spatial soil continuum but provides a sound basis to do so using methods from statistical learning theory to develop digital soil maps is much more efficient and precise while regionalising soil diagnostic properties instead of complex entities such as the soil units assigned by the wrb particularly in providing spatial soil information displayed in digital soil maps any aggregation of this spatial soil information to soil units means a loss of information the soil landscape can be systematically described in its spatial continuum simply by the vertical order and extent of the wrb diagnostic horizons the diagnostic horizons are related in their thickness to a standard depth and listed from top to bottom in order of appearance typical diagnostic horizon thickness and occurrence probability were predicted from terrain parameters by classification and regression trees cart throughout the research area in southern ecuador the two disadvantages of cart abrupt prediction class boundaries and dependence on the dataset were addressed by hundredfold model runs on different data subsets leading to a range of possible predictions prediction uncertainty was included in the digital soil maps by calculating these predictions means and standard deviations as well as by horizon occurrence probability prediction model performance was evaluated by means of hundredfold external cross validation terrain parameters were found to have a strong influence on diagnostic topsoil properties however no influence on the vertical profile differentiation was observed hence predicting horizon thickness and subsoil diagnostic properties was difficult the systematic description of the soil continuum of this particular soil landscape resulted in histic and stagnic soil parts dominating the first 100 cm of the soil column for most of the area

glacier fluctuations during the past 2000 years abstract a global compilation of glacier advances and retreats for the past two millennia grouped by 17 regions excluding antarctica highlights the nature of glacier fluctuations during the late holocene the dataset includes 275 time series of glacier fluctuations based on historical tree ring lake sediment radiocarbon and terrestrial cosmogenic nuclide data the most detailed and reliable series for individual glaciers and regional compilations are compared with summer temperature and when available winter precipitation reconstructions the most important parameters for glacier mass balance in many cases major glacier advances correlate with multi decadal periods of decreased summer temperature in a few cases such as in arctic alaska and western canada some glacier advances occurred during relatively warm wet times the timing and scale of glacier fluctuations over the past two millennia varies greatly from region to region however the number of glacier advances shows a clear pattern for the high mid and low latitudes and hence points to common forcing factors acting at the global scale globally during the first millennium ce glaciers were smaller than between the advances in 13th to early 20th centuries ce the precise extent of glacier retreat in the first millennium is not well defined however the most conservative estimates indicate that during the 1st and 2nd centuries in some regions glaciers were smaller than at the end of 20th early 21st centuries other periods of glacier retreat are identified regionally during the 5th and 8th centuries in the european alps in the 3rd 6th and 9th centuries in norway during the 10th 13th centuries in southern alaska and in the 18th century in spitsbergen however no single period of common global glacier retreat of centennial duration except for the past century has yet been identified in contrast the view that the little ice age was a period of global glacier expansion beginning in the 13th century or earlier and reaching a maximum in 17th 19th centuries is supported by our data the pattern of glacier variations in the past two millennia corresponds with cooling in reconstructed temperature records at the continental and hemispheric scales the number of glacier advances also broadly matches periods showing high volcanic activity and low solar irradiance over the past two millennia although the resolution of most glacier chronologies is not enough for robust statistical correlations glacier retreat in the past 100 150 years corresponds to the anthropogenic global temperature increase many questions concerning the relative strength of forcing factors that drove glacier variations in the past 2 ka still remain

observations of mesoscale eddies in the south atlantic cape basin baroclinic and deep barotropic eddy variability 1 anticyclones and cyclones in the eastern south atlantic are characterized based on data collected during january 2003 to march 2005 along a jason 1 satellite altimeter ground track as part of the agulhas south atlantic thermohaline transport experiment large and small cyclones and anticyclones were ubiquitous in the deep ocean of the eastern south atlantic as well as in the upper ocean eddy structures jointly corotating in the upper and deep water column were common most of the time 94 these were not axially aligned as they copropagated the agulhas rings and cyclones that populate the region generally carry both a steric component baroclinic and a mass loading component deep barotropic structure average translation speeds were 7 5 cm s 1 for baroclinic eddies and twice as fast for barotropic eddies irrespective of polarity translation speeds were higher than advection by the mean background flow field in addition large mixed baroclinic barotropic rings crashed into the agulhas ridge and nearby seamounts and split into two or more parts some ring parts were also observed to fuse together deep cyclones as well as interactions with topography were observed to play a role in the fission process of agulhas rings these processes can increase the population of agulhas rings and their remnant eddies which took three pathways from the agulhas and into the cape basin 1 a deep pathway between the continental slope and erica seamount 2 a shallower pathway over or near the agulhas ridge and schmitt otto seamount and 3 a deep seaward pathway around the agulhas ridge

on sverdrup discontinuities and vortices in the southwest indian ocean abstract the southwest indian ocean is distinguished by discontinuities in the wind driven sverdrup circulation these connect the northern and southern tips of madagascar with africa and the southern tip of africa with south america in an analytical barotropic model with a flat bottom the discontinuities produce intense westward jets those off the northern tip of madagascar and the southern tip of africa are always present while the strength of that off southern madagascar depends on the position of the zero curl line in the indian ocean the jet is strong if the line intersects madagascar but weak if the line is north of the island all three jets are barotropically unstable by the rayleigh kuo criterion the authors studied the development of the instability using a primitive equation model with a flat bottom and realistic coastlines the model produced westward jets at the three sites and these became unstable after several weeks generating 200 300 km scale eddies the eddies generated west of

ice loss rates at the northern patagonian icefield derived using a decade of satellite remote sensing abstract we use a satellite based survey of glacier surface elevation changes speeds and surface melt conditions between 2000 and 2011 to quantify mass loss from the northern patagonian icefield npi chile a history of ice elevation change is found by differencing aster digital elevation models dems relative to a void filled version of the dem collected by the shuttle radar topography mission srtm in february 2000 thinning rates have accelerated at lower elevations while above the equilibrium line altitude ela recent thinning rates are not significantly different from those observed in previous studies a volumetric change of 4 06 0 11 km 3 yr is found by summing surface elevation changes over all glaciers in the npi this is regarded as a lower bound because volume loss due to frontal retreat and sub aqueous melting is not included this volume change is converted to a mass loss of 3 40 0 07 gt yr taking into account density differences above and below the equilibrium line we find that the npi is providing at least 0 009 0 0002 mm yr to ongoing sea level change in agreement with previous estimates sub pixel offset tracking of aster image pairs is used to produce glacier displacements over intervals typically ranging from 6 days to 18 months the first whole icefield composite velocity map is presented the terminus of the san rafael glacier on the western side of the npi sustained a peak calving front speed of 19 7 1 2 m day for 7 days in the austral fall of 2007 passive microwave observations indicate that the surface of the accumulation basin of the glacier was wet during this period of rapid motion suggesting that the fast speed may be a consequence of a rise in sub glacial water pressure sourced from melt or rainwater making its way to the glacier bed and reducing basal friction several other outlet glaciers including the benito and hpn1 glaciers on the isolated western side of the icefield accelerated while thinning between 2007 and 2011 marked acceleration also occurred after 2007 at the front of the san quintin glacier the largest outlet glacier of the npi the paucity of thickness measurements at the outlet glaciers means it is impossible to accurately gauge the mass flux of the icefield and thus give a full estimate of the mass balance

evidence for enhanced debris flow activity in the northern calcareous alps since the 1980s plansee austria abstract debris flows are among the most important natural hazards the northern calcareous alps with their susceptible lithology are especially affected by a double digit number of major hazard events per year it is hypothesised that debris flow intensity has increased significantly in the last decades in the northern calcareous alps coincident to increased rainstorm frequencies but yet there is only limited evidence the plansee catchment exposes extreme debris flow activity due to the intensely jointed upper triassic hauptdolomit lithology being responsible for most of the debris flow activity in the northern calcareous alps the debris flows feed into a closed sediment system the plansee lake where holocene lateglacial sedimentation rates rates since the late 1940s and recent rates can be inferred accurately using aerial photos and field mapping the temporal and spatial development of eight active debris flow fans is reconstructed in six time intervals from 1947 1952 1971 1979 1987 2000 and 2010 and mean annual debris flow volumes are calculated these are compared with mean holocene lateglacial debris flow volumes derived from the most prominent cone whose contact with the underlying till is revealed by electrical resistivity tomography ert debris flow activity there increased by a factor of 10 from 1947 1952 0 23 0 07 103 m3 yr to 1987 2000 2 41 0 66 103 m3 yr mean post 1980 rates from all eight fans exceed pre 1980 rates by a factor of more than three coinciding with enhanced rainstorm activity recorded at meteorological stations in the northern calcareous alps the frequency of rain storms def 35 mm d has increased in the study area on average by 10 per decade and has nearly doubled since 1921 recent debris flow activity is also 2 3 times higher than mean holocene lateglacial rates the strong correlation between the non vegetated catchment area and the annual debris flow volume might indicate a decadal positive feedback between enhanced rainstorm activity and debris flows here we investigate the temporal and spatial development of debris flow fans to better understand the sensitivity of alpine catchments to heavy rainfall events in the context of climate change

gualas glacier sedimentary record of climate and environmental change golfo elefantes western patagonia 46 5 s gualas glacier is an outlet glacier of the northern patagonian icefield one of the largest temperate ice bodies on earth golfo elefantes the depositional basin of gualas glacier has a sedimentary record that spans with some hiatuses at least the last 11 3 3 0 ka during this period the gulf remained free of ice as suggested by the absence of proximal glacimarine sediment and till in the sedimentary section this implies that the arcuate terminal moraines that occur along the edges of golfo elefantes were formed during the waning stages of the local glacial maxima late pleistocene or the early holocene between 11 3 3 0 ka and 4 2 0 3 1 4 ka the basin received low sediment input consisting of fine grained sediments in the form of low concentration density currents that filled bathymetric lows sediment discharge increased several times in the late holocene 1 4 ka and started with the accumulation of 0 5 km3 of sandy sediments in a relatively short time span 670 yr this high discharge

interannual eddy kinetic energy modulations in the agulhas return current interannual variability in the mesoscale eddy field in the agulhas return current arc of 32 42 degrees s and 15 35 degrees e is investigated based on satellite altimeter observations and state estimate from the estimating the circulation and climate of the ocean phase ii from 1993 to 2016 it is found that the interannual modulation of eddy kinetic energy in the arc region is externally mediated by the wind stress forcing that generates the westward propagating sea surface height anomalies across the south indian ocean subtropical gyre the wind forced sea surface height anomalies influence the upstream agulhas current volume transports by modulating the intensity of barotropic instability of the arc mean flow centered around the retroflection region the agulhas current inflow variability leads to the downstream interannual eddy kinetic energy fluctuations in the arc region

glacier fluctuations in extratropical south america during the past 1000 years article i nfo this paper presents an updated extensive review of glacier fluctuations during the past 1000 years in the extratropical andes of south america between ca 17 and 55 s given the variety of environmental conditions and evidence available for glacier fluctuations across this wide latitudinal range regional accounts are given for the desert andes 17 31 s the andes of central chile and argentina 31 36 s and the north 36 45 s and south 45 55 s patagonian andes the techniques dating limitations and interpretations of the glacier records along this transect are also discussed information on glacier fluctuations in the desert andes is limited to the 20th century documentation on past glacier variations is more abundant in the central chilean argentinean andes but the number of chronologies dealing with glacier fluctuations prior to the 1900s is also limited most records indicate that glaciers were generally more extensive prior to the 20th century with dates of maximum expansion ranging from the 16th to the 19th centuries the number and extent of glaciers increase significantly in the patagonian region where the evidence available for dating glacier variations during the past centuries is more abundant and the dating control for glacier events is generally better than in the northern parts of the study area for some patagonian glaciers maximum little ice age lia or post lia advances have been precisely dated by dendro geomorphological determinations or in situ measurements however for most sites the evidence available is still preliminary and there is considerable variability in the extent and timing of events related to the maximum lia expansion identified in most areas between the 16th and 19th centuries evidence is starting to appear at a growing number of sites for glacier advances during the first half of the past millennium these events were generally less extensive than the lia maximum pulses despite the occurrence of several post lia readvances over the past 100 110 years most areas in the andes of extratropical south america have experienced a general pattern of glacier recession and significant ice mass losses the differences in the glacier histories observed at local and regional scales probably reflect the inherent limitations associated with the glacier records and or the dating techniques used in each case together with the varying dominance of precipitation temperature and other climatic and non climatic factors on glacier mass balance and glacier dynamics these differences indicate that the late holocene glacier history of southern south america is more complex than commonly assumed the evidence discussed in this study highlights not only the immense potential for glaciological studies of this region but also a significant need for an increased number of detailed well dated records of glacier fluctuations

glaciar leon chilean patagonia late holocene chronology and geomorphology harrison s glasser n f winchester v haresign e warren c duller g a t bailey r ivy ochs s jansson k kubik p 2008 glaciar leon chilean patagonia late holocene chronology and geomorphology the holocene 18 4 pp 643 652 sponsorship nerc university of st andrews american alpine club british geomorphological research group dudley stamp memorial trust royal scottish geographical society quaternary research association carnegie trust for the universities of scotland