expansion of ice marginal lakes at the vatnajokull ice cap iceland from 1999 to 2009 abstract outlet glaciers from the vatnajokull ice cap in iceland europe s largest ice cap have been retreating since the end of the little ice age only interrupted by short intervals of advances the net mass balance has been negative since 1995 and ice marginal lakes in front of the outlets have been expanding since then the switch from land based glacier termini to lake terminating glaciers is an eye catching environmental change the heat capacity of the ice marginal lakes and the change into calving glacier fronts accelerates ice loss from vatnajokull landsat 7etm satellite imagery from 1999 to 2009 reveals high resolution snapshots of the lake development during the last decade ice marginal lakes are growing at many outlet glaciers draining the southern sector of vatnajokull this is most pronounced at the large brei amerkurjokull glacier where the jokulsarlon lake expanded from 15 km 2 in 2000 to more than 21 km 2 in 2009 the lakes act as traps for sediment that was earlier transported across outwash plains toward the atlantic coast hence the glacier retreat and sediment trapping enhance coastline retreat and river incision in the outwash plains similar changes although at a much larger scale occurred in many past glaciated regions during the last glacial termination thus the lakes in front of vatnajokull provide important modern analogues for processes that likely impacted global climate in the past

sub basin scale dust source geomorphology detected using modis 1 the spatial and temporal variability of dust emissions from different surfaces in the lake eyre basin australia is determined using modis data for 2003 6 the sources of 529 dust plumes were classified overall 37 of plumes originated in areas of aeolian deposits 30 from alluvial deposits and floodplains and 29 from ephemeral lakes or playas at this sub basin scale the relative importance of different dust source geomorphologies varied primarily in response to sediment supply and availability and was not related to aeolian transport capacity suggesting the lake eyre basin is a supply limited system

dependence of the energy balance of the greenland ice sheet on climate change influence of katabatic wind and tundra the summer time atmospheric circulation at the margin of a large ice sheet with an extended adjacent tundra is investigated with a two dimensional atmospheric model the assumed topography corresponds to the section through west greenland for which the greenland ice margin experiment gimex was performed with this model the local sensitivity of the ablation of the ice sheet to changes in the external parameters which pertain to climate is explored the main focus is the sensitivity which is related to atmospheric dynamics a comparison is made between the results with an exposed tundra and results with a snow covered tundra in the latter case the katabatic wind is strongly reduced close to the ice margin so that the downward sensible heat flux for the ablation zone is more than halved this shows that the influence of the exposed tundra on the energy balance of the ice sheet is important increasing the initial air temperatures leads to a stronger katabatic wind as a consequence the downward sensible heat flux at the ablation zone is strongly enhanced neglecting the change of the katabatic wind would lead to a much smaller growth of this flux which shows that the presence of an exposed tundra increases the sensitivity of the energy balance of the ice sheet to climate change for those runs the large scale wind is zero but in the presence of an inland directed large scale wind a strong surface wind parallel to the glacier front is found to develop above the ablation zone by which the sensible heat flux is increased the advection of heated air from the tundra to the ice sheet plays a lesser role

desert loess versus glacial loess quartz silt formation source areas and sediment pathways in the formation of loess deposits abstract pathways are presented which show the proposed sequence of events involved in the formation of loess deposits both hypothetical deposits and those of central china hungary nigeria and tunisia these pathways illustrate the potential role of and inter relationships between a variety of silt generating mechanisms in the formation of loess using these pathways the existence of desert loess is discussed and it is concluded that this depends on how the terms glacial loess and desert loess are applied if desert loess is taken either to signify nonglacial mechanisms of silt production or to characterise the environment from which aeolian entrainment took place then desert loess is a very real and widely distributed deposit however if the term glacial loess is used to refer to the global climatic regime under which the loess deposit has formed rather than the geomorphic mechanisms responsible for silt generation then desert loess would not be an appropriate term for the classification of loess deposits it is suggested that classifying loess deposits with reference to the global climatic regime under which they accumulated would facilitate a greater understanding of the role of environmental conditions at all stages in the formation of loess deposits

seasonal variability in the origin of recent atmospheric mineral dust at northgrip greenland abstract isotopic sr and nd and mineralogical analyses of dust extracted from snow deposits from the last decade at the northgrip greenland ice camp 75 1 n 042 3 w confirm the eastern asian source for greenland dust and extend it to the present day the 1998 and 1999 samples which represent a 2 4 month resolution of dust deposition show that there are at least two east asian sources for the greenland dust that vary seasonally the provenance of dust during the major spring summer deposition is the takla makan desert of northwest china

influence of patagonian glaciers on antarctic dust deposition during the last glacial period dust deposition over antarctica was much higher during the last glacial period but the causes of this flux remain unclear an analysis of the composition and age of glacial outwash sediments indicates that growth and decay of glaciers in patagonia may have influenced dust transport to antarctica at that time

will present day glacier retreat increase volcanic activity stress induced by recent glacier retreat and its effect on magmatism at the vatnajokull ice cap iceland an area of 8000 km 2 has been continuously retreating losing about 10 of its mass during last century present day uplift around the ice cap is as high as 25 mm yr we evaluate interactions between ongoing glacio isostasy and current changes to mantle melting and crustal stresses at volcanoes underneath vatnajokull the modeling indicates that a substantial volume of new magma 0 014 km 3 yr is produced under vatnajokull in response to current ice thinning ice retreat also induces significant stress changes in the elastic crust that may contribute to high seismicity unusual focal mechanisms and unusual magma movements in nw vatnajokull citation pagli c and f sigmundsson 2008 will present day glacier retreat increase volcanic activity stress induced by recent glacier retreat and its effect on magmatism at the vatnajokull ice cap iceland geophys res lett 35 l09304 doi 10 1029 2008gl033510

iron solubility driven by speciation in dust sources to the ocean particulate aerosols are thought to be the primary source of iron to the oceans but the factors determining their solubility and thus bioavailability are unclear x ray absorption analysis reveals that speciation controls the solubility of iron in three large sources of aerosol iron

dust raising in the dustiest place on earth the bodele in northern chad is the dustiest place on earth it is dusty because of the co location of strong near surface winds and a large exposure of low density friable diatomite data are reported from three kinds of observation on dust generation in the bodele a two automatic weather stations and pilot balloon tracking complemented with reanalysis data measuring and estimating wind velocities b sun photometers measuring atmospheric dust concentrations c a vacuum pump dust sampler and an array of mwac sediment samplers measuring in situ sediment transport with these data we develop four hypotheses about dust generation 1 the pulsing of dust output from the bodele depends primarily on the varying strength of a low level jet llj i e at this scale dust production is transport limited 2 the most prolific mechanism of dust production is the breakdown of saltating diatomite flakes as they collide with each other and with the surface 3 disturbance of flow around the large barchans particularly turbulence and convergence on their horns is a major contributor to dust production i e the dunes are dust mills 4 in consequence dust production is localised within the main exposure of diatomite to places where there are the most dunes as on the eastern and northern fringes of the exposure

rivers and loess the significance of long river transportation in the complex event sequence approach to loess deposit formation abstract rivers are essential for loess deposit formation river systems which relate directly to loess deposit formation include the danube and the rhine the mississippi and the missouri the thames and the medway the indus ganges and brahmaputra the dnepr don and volga the clutha mataura and rakaia new zealand rivers the yellow river rivers in south america siberian rivers flowing north the odra and the wisla between the mountains and the ice the syr darya and amu darya into the desert the contention is that rivers are not just important in major loess deposit formation they are mandatory necessary imperative obligatory essential indispensable requisite for a complete and satisfactory study of a loess deposit we need to know how the material is produced how it is transported and distributed across the landscape how intermediate deposits are formed how transportation provides the defining properties i e open structure collapsibility draping across the landscape and what may happen post deposition e g chernozemisation fragipan formation increased collapsibility etc if rivers are essential then it would appear that the british loess is probably alpine material delivered by the proto rhine and the polish loess is not derived from the ice sheet to the north but from the mountains to the south the lack of loess in canada is explained by the absence of suitable rivers the loess in russia and neighbouring countries can be classified as jefferson et al jefferson i f evstatiev d karastenev d mavlyanova n g smalley i j 2003b the engineering geology of loess and loess like deposits a commentary on the russian literature engineering geology 68 333 351 suggested on the basis of associated rivers a new deposit of glacial loess is recognised associated with the dnepr don and volga rivers the uswr loess the smalley leach smalley i j leach j a 1978 the origin and distribution of the loess in the danube basin and associated regions of east central europe a review sedimentary geology 21 1 26 available from www geo edu ro sgr mod downloads pdf smalley sedgeo 1978 pdf vision of the loess in the danube basin and east central europe is probably misconceived they assigned a great significance to glacial action and put loess in a northern band it appears that this proposed glacial influence is minimal and that the danube loess is essentially mountain loess derived from the alps the carpathians the sudeten mountains and other high regions the danube system is a classic example of a river controlling loess distribution

paleoecological studies of a holocene lacustrine record from the kangerlussuaq sondre stromfjord region of west greenland abstract a lacustrine sediment record from the kangerlussuaq region west greenland has resulted in a pollen macrofossil and sediment stratigraphy that encompasses the last 5000 14 c yr deglaciation of the area and subsequent development of a nearby floodplain occurred before 5000 yr b p since that time eolian sand and silt deposition appear to have been continuous with a significant increase ca 1000 14 c yr b p pollen analysis shows little change in the character of the vegetation throughout the record fluctuations in herb pollen taxa indicate changes in the extent and development of eolian sand sheets the oldest pollen zone records relatively little pollen accumulation and low taxa diversity this is followed by a zone of high pollen accumulation presumably a phase of highest vegetation density from 4400 to 3400 14 c yr b p thereafter declining pollen accumulation rates reveal a gradual environmental deterioration macrofossil analyses record significant limnological changes with an early eutrophic phase followed by a masotrophic phase and a reversal to more eutrophic conditions in the final phase the preserved record illustrates the interactions of deglaciation eolian activity regional vegetation and limnological change

glacial flour dust storms in the gulf of alaska hydrologic and meteorological controls and their importance as a source of bioavailable iron 1 iron is an essential micronutrient that limits primary productivity in much of the ocean including the gulf of alaska goa however the processes that transport iron to the ocean surface are poorly quantified we combine satellite and meteorological data to provide the first description of widespread dust transport from coastal alaska into the goa dust is frequently transported from glacially derived sediment at the mouths of several rivers the most prominent of which is the copper river these dust events occur most frequently in autumn when coastal river levels are low and riverbed sediments are exposed the dust plumes are transported several hundred kilometers beyond the continental shelf into iron limited waters we estimate the mass of dust transported from the copper river valley during one 2006 dust event to be between 25 80 ktons based on conservative estimates this equates to a soluble iron loading of 30 200 tons we suggest the soluble fe flux from dust originating in glaciofluvial sediment deposits from the entire goa coastline is two to three times larger and is comparable to the annual fe flux to goa surface waters from eddies of coastal origin given that glaciers are retreating in the coastal goa region and in other locations it is important to examine whether fluxes of dust are increasing from glacierized landscapes to the ocean and to assess the impact of associated fe on marine ecosystems

the forcing of antarctic katabatic winds abstract the temporal and spatial development of katabatic winds along an idealized slope representative of anmtarctic terrain is examined using a hydrostatic two dimensional primitive equation model with explicit longwave radiation parameterization a detailed diagnosis is made of a simulation in which katabatic flow develops from rest due to the strong radiational cooling of the underlying surface significant thermodynamic and dynamic differences are seen between the gravity driven flows over the gently sloping interior and over the steep ice slopes near the coast the strongest temperature inversions and largest static stabilities are found over the interior of the continent although the net cooling of the katabatic layer and magnitude of the downslope directed horizontal pressure gradient force are greatest at the coast the interior is characterized by low rossby number quasi geostrophic type flows while more intense near antitriptic winds occur at the coast model results are in reasonable agr

magmatic crystallization isobaric cooling and decompression of the garnet bearing assemblages of the jijal sequence kohistan terrane western himalayas the jijal ultramafic mafic sequence is the lowermost exposed part of the kohistan terrane petrography and geothermobarometry show that garnet bearing assemblages of the jijal sequence consist of a mosaic of magmatic and metamorphic equilibria garnet bearing magmatic assemblages started their crystallization at a depth 50 km either at the base of a thickened arc type crust or within rising magmatic batches in the upper mantle quasi isobaric cooling of magmatic assemblages occurred in the high p high t granulite field without reaching the eclogite field subsequently these assemblages were partly retrograded under amphibolite to greenschist facies conditions this succession of equilibria attests to a switch from a high p quasi isobaric cooling regime to a major decompression followed by final cooling at the upper crustal level this p t evolution is best explained by a yet unrecognized tectonic event that consists of partial exhumation of the base of the kohistan terrane during its accretion to the asian plate final cooling and unloading in turn could be related to extension following the obduction of the kohistan terrane onto the indian plate

experimental rock on rock frictional wear application to subglacial abrasion 1 rock on rock wear under known normal loads was measured experimentally using 62 mm diameter rotating discs machined from a range of silicic rock types one granite two metamorphic rocks and three sandstones of porosities varying between 7 and 28 wear debris was removed continuously from the contacting surfaces by water we obtained a wear law of the form dt dx a n m where is contact normal stress mpa dt dx is a dimensionless wear rate meter wear t per meter shear displacement x is porosity and a n and m are empirical constants 10 8 11 8 33 and 4 50 respectively low porosity rocks displayed surface polishing and abraded particle size was substantially smaller than the starting grain size whole grains were plucked from high porosity rocks without any surface polishing so that the wear product particle size remained the same as that of the starting material the empirical wear law describes abrasion beneath a hard bedded temperate glacier provided we can estimate both the in situ normal stress between entrained clasts and the bed and the horizontal velocity of the clasts in the flowing ice normal stress concentration is expected to develop at clast bed contacts from drag against ice flowing toward the bed where pressure melting occurs these experimental data are consistent with wear rates inferred from silt outflow in subglacial streams provided a tenfold stress concentration can occur relative to the ice overburden pressure the rate of production of fine grained wear products under subglacial conditions is substantially less than by tectonic faulting

sediment plume response to surface melting and supraglacial lake drainages on the greenland ice sheet increased mass losses from the greenland ice sheet and inferred contributions to sea level rise have heightened the need for hydrologic observations of meltwater exiting the ice sheet we explore whether temporal variations in ice sheet surface hydrology can be linked to the development of a downstream sediment plume in kangerlussuaq fjord by comparing 1 plume area and suspended sediment concentration from moderate resolution imaging spectroradiometer modis imagery and field data 2 ice sheet melt extent from special sensor microwave imager ssm i passive microwave data and 3 supraglacial lake drainage events from modis results confirm that the origin of the sediment plume is meltwater release from the ice sheet interannual variations in plume area reflect interannual variations in surface melting plumes appear almost immediately with seasonal surface melt onset provided the estuary is free of landfast sea ice a seasonal hysteresis between melt extent and plume area suggests late season exhaustion in sediment supply analysis of plume sensitivity to supraglacial events is less conclusive with 69 of melt pulses and 38 of lake drainage events triggering an increase in plume area we conclude that remote sensing of sediment plume behavior offers a novel tool for detecting the presence timing and interannual variability of meltwater release from the ice sheet

sedimentology of cold climate aeolian sandsheet deposits in the askja region of northeast iceland active aeolian sandsheets cover an area of 270 km2 in the askja region of ne iceland the sandsheet is divided into i a deflationary upwind part that is characterised by deflation lags ventifacted boulder fields and restricted aeolian sand patches in the lee of obstacles ii an accumulating central part that is characterised by continuous aeolian sand cover up to 10 m thick where three scales of aeolian ripples are evident along with larger scale forms including longitudinal zibars and iii a downwind part that is currently subject to aeolian bypass with only localised accumulation occurring in topographic hollows between basaltic lava fields trains of aeolian granule megaripples are a characteristic landform of the downwind part of the sandsheet these sinuous crested oblique bedforms attain heights of 0 35 m and downwind spacings of 6 m they are composed principally of low density pebble grade pumice clasts and other reworked volcaniclastic detritus derived from the nearby askja volcanic centre the distribution of landforms across the sandsheet reflects a regional aeolian sediment budget that is controlled by dynamic interactions between glacial ice margin fluvial aeolian and volcaniclastic processes under the influence of a distinctive climatic regime sediment supply at the upwind sandsheet margin adjacent to the dyngjujokull glacier increases during summer periods when rates of glacial ablation are at a maximum longer term controls on sediment supply rate are determined by episodes of glacier surging and retreat and by periodic eruptions of volcaniclastic debris from the askja volcanic centre the availability of sediment for aeolian transport is controlled by the level of the groundwater table the depth and continuity of the permafrost layer in the proglacial area the degree of development of armoured pebble lags and freezing of the sandsheet surface during winter months the transport capacity of the wind varies on a seasonal basis with mean wind velocities and wind gustiness reaching a maximum during winter periods both winter and summer mean wind velocities have been steadily increasing since formal records began in 1969 the suite of aeolian landforms developed within the askja region as defined by sediment texture and composition and bedform scale morphology and spatial distribution reflects a special set of controlling circumstances which mean that the askja sandsheet deposits differ significantly from those described from elsewhere

observed runoff jokulhlaups and suspended sediment load from the greenland ice sheet at kangerlussuaq west greenland 2007 and 2008 this study fills the gap in hydrologic measurements of runoff exiting a part of the greenland ice sheet gris the kangerlussuaq drainage area west greenland the observations are of value for obtaining knowledge about the terrestrial freshwater and sediment output from part of the gris and the strip of land between the gris and the ocean in the context of varying ice sheet surface melt and influx entering the ocean high resolution stage discharge and suspended sediment load show a decrease in runoff of approx 25 and in sediment load of approx 40 from 2007 to 2008 in response to a decrease in the summer accumulated number of positive degree days during the 2007 and 2008 runoff season joekulhlaups are observed at kangerlussuaq drained from an ice dammed lake at the margin of the gris

characteristics of aeolian grain transport over a fluvio glacial lacustrine braid delta lake tekapo new zealand this paper presents results from one of the few scientific studies to examine the physical characteristics of aeolian sediment transport in an alpine area where topographically reinforced foehn winds initiate dust storm events the major objective of this study is to improve knowledge of aeolian processes in mid latitude alpine regions experiencing extreme wind speeds of particular interest is the role of surface characteristics in contributing to the unusually deep saltation layer which is seen to form over fluvio glacial deposits in the southern alps of new zealand sediment was collected at several heights 0 5 1 2 and 4 m and locations over a large alpine braided river delta and standard laboratory techniques used to examine grain size characteristics an image processing technique was also used to evaluate grain roundness grains filtered from the airstream at 0 5 m and 1 m above such surfaces were found to display a mean grain size of approximately 300 to 435 m resembling grain size characteristics of saltation clouds previously observed in high latitude cold climate locations in contrast to desert and prairie environments samples collected at 2 and 4 m above the surface were found to consist of 60 to 65 per cent sand sized material with some grains exceeding 1 1 5 mm in diameter grain shape analysis conducted on silt and clay sized grains filtered from the airstream above mixed sand and gravel surfaces showed such grains to display an increase in grain roundness with height this characteristic is thought to reflect the airstream s shape sorting ability and has important implications with respect to the often observed increase in grain roundness in aeolian deposits with increasing distance from source areas namely if more rounded grains are preferentially carried higher into the airstream and therefore into regions of higher wind speed they should theoretically be transported further from the entrainment zone before being deposited the high wind speeds observed often exceeding 30 m s 1 are seen to transport significantly larger sediment than reported in the literature for desert and prairie environments in addition the mixture of grain sizes and especially the pebble and cobble sized clasts that dominate the fluvio glacial deposits associated with the braided rivers in this mountain region also appear to increase significantly the trajectory height of saltating sand grains as a result of these two factors the depth of the saltation cloud often exceeds 1 m observations made in this study therefore highlight the need for field and laboratory aeolian process studies to be extended to examine grain transport over coarse grained beds during much higher wind velocities than typically reported in the literature such studies would provide a valuable insight into aeolian processes in high latitude altitude environments such as loess genesis 1997 by john wiley sons ltd

glacial interglacial co2 change the iron hypothesis several explanations for the 200 to 280 ppm glacial interglacial change in atmospheric co2 concentrations deal with variations in southern ocean phytoplankton productivity and the related use or nonuse of major plant nutrients an hypothesis is presented herein in which arguments are made that new productivity in today s southern ocean 7 4 1013g yr 1 is limited by iron deficiency and hence the phytoplankton are unable to take advantage of the excess surface nitrate phosphate that if used could result in total southern ocean new production of 2 3 1015 g c yr 1 as a consequence of fe limited new productivity holocene interglacial co2 levels preindustrial are as high as they were during the last interglacial 280 ppm in contrast atmospheric dust fe supplies were 50 times higher during the last glacial maximum lgm because of this fe enrichment phytoplankton growth may have been greatly enhanced larger amounts of upwelled nutrients may have been used and the resulting stimulation of new productivity may have contributed to the lgm drawdown of atmospheric co2 to levels of less than 200 ppm background information and arguments in support of this hypothesis are presented

a holocene record of atmospheric dust deposition on the penny ice cap baffin island canada a holocene record of atmospheric dust deposition on the penny ice cap baffin island canada

the dynamic effects of moisture on the entrainment and transport of sand by wind abstract there is an increasing awareness of the influence of surface moisture on aeolian entrainment and transport of sediment existing wind tunnel studies have shown the impact of a limited range of moisture contents on entrainment thresholds but similar investigations are lacking in the field the research reported here investigated the influence of changes in surface moisture content on sand entrainment and transport on a meso tidal beach in anglesey north wales high frequency 1 hz wind velocities measured with hot wire anemometers were combined with grain impact data from a sensit monitor and mass flux measurements from a standard sand trap surface and near surface moisture contents were assessed gravimetrically from surface sand scrapes and also directly by using a thetaprobe critical threshold values for entrainment were specified using a modified form of the time fraction equivalence method stout j e zobeck t m 1996a establishing the threshold condition for soil movement in wind eroding fields proceedings of the international conference on air pollution from agricultural operations mwps c 3 kansas city 7 9 february 1996 pp 65 71 results indicate a time dependent change in dominant control of the sand transport system from moisture to wind speed dependent upon the moisture content of the surface sediment this interchange between controlling parameters on both entrainment and transport was very sensitive to prevailing moisture conditions and took place over a period of minutes to hours under conditions experienced in the experiments presented here the critical moisture threshold for sediment entrainment was determined to be between 4 and 6 higher than the 1 4 specified in previous wind tunnel experiments furthermore a moisture content of nearly 2 where moisture was adhered to transported sediment appeared to have little or no impact on the rate of sand flux

iron and other transition metals in patagonian riverborne and windborne materials geochemical control and transport to the southern south atlantic ocean abstract the bulk of particulate transition metals transported by patagonian rivers shows an upper crustal composition riverine particulate 0 5 n hcl leachable trace metal concentrations are mainly controlled by fe oxides complexation of fe by dissolved organic carbon doc appears to be an important determinant of the phases transporting trace metals in patagonian rivers in contrast aeolian trace elements have a combined crustal and anthropogenic origin aeolian materials have fe mn and al contents similar to that found in regional topsoils however seasonal concentrations of some metals e g co pb cu and zn are much higher than expected from normal crustal weathering and are likely pollutant derived we estimate that patagonian sediments are supplied to the south atlantic shelf in approximately equivalent amounts from the atmosphere 30 10 6 t yr 1 and coastal erosion 40 10 6 t yr 1 with much less coming from the rivers 2 0 10 6 t yr 1 low trace metal riverine fluxes are linked to the low suspended particulate load of patagonian rivers inasmuch most of it is retained in pro glacial lakes as well as in downstream reservoirs based on our estimation of aeolian dust fluxes at the patagonian coastline the high nutrient low chlorophyll sub antarctic south atlantic could receive 1 0 to 4 0 mg m 2 yr 1 of leachable 0 5 n hcl fe past and present volcanic activity in the southern andes through the ejection of tephra must be highlighted as another important source of fe to the south atlantic ocean based on the 1991 hudson volcano eruption it appears that volcanic events can contribute several thousand fold the mass of leachable fe to the ocean as is introduced by annual patagonian dust fallout

aeolian processes and the biosphere ravi s d odorico p breshears d d field j p goudie a s huxman t e li j okin g s swap r j thomas a d pelt s v whicker j j zobeck t m 2011 aeolian processes and the biosphere reviews of geophysics 49 3

the ablation zone in northeast greenland ice types albedos and impurities ice types albedos and impurity content are characterized for the ablation zone of the greenland ice sheet in kronprinz christians land 80 n 24 w along this ice margin the width of the ablation zone is only about 8 km the emergence and melting of old ice in the ablation zone creates a surface layer of dust that was originally deposited with snowfall high on the ice sheet this debris cover is augmented by locally derived wind blown sediment subsequently the surface dust particles often aggregate together to form centimetre scale clumps that melt into the ice creating cryoconite holes the debris in the cryoconite holes becomes hidden from sunlight raising the area averaged albedo relative to surfaces with uniform debris cover spectral and broadband albedos were obtained for snow ice hummocks debris covered ice cryoconite studded ice and barren tundra surfaces broadband ice albedos varied from 0 2 for ice with heavy loading of uniform debris to 0 6 for ice hummocks with cryoconite holes the cryoconite material itself has albedo 0 1 when wet areal distribution of the major surface types was estimated visually from a transect video as a function of distance from the ice edge 330 m a s l ablation rates were measured along a transect from the ice margin to the slush zone 8 km from the margin 550 m a s l traversing both pleistocene and holocene ice ablation rates in early august averaged 2 cm d 1 impurity concentrations were typically 4 3 mg l 1 in the subsurface ice surface concentrations were about 16 g m 2 on surfaces with low impurity loading and heavily loaded surfaces had concentrations as high as 1 4 kg m 2 the mineralogical composition of the cryoconite material is comparable with that of the surrounding soils and with dust on a snowdrift in front of the ice margin implying that much of the material is derived from local sources a fine mode clay is present in the oldest ice but not in the nearby soil suggesting that its origin is from wind deposition during pleistocene glaciation

loess is not just the accumulation of dust most regrettably there is much misuse of terminology in connection with the concept of loess and the interpretation of its origin people often speak and write incorrectly about loess accumulation even loess specialists who are aware of the fact that loess as a concept has to satisfy at least 10 criteria loess is not simply dust carried and deposited by wind dust only becomes loess after the passage of a certain amount of time in a given geographical zone i e only through diagenesis in certain ecological environments to state that loess is of aeolian origin is an oversimplification and an incorrect definition because an aeolian origin applies only to the dust from which the loess has been formed we are aware of the fact that airborne dust cannot be transformed into loess in every geographical environment but only under those conditions typical of semi arid grassland or steppe or forested steppe the process primarily occurs where the rate of dust accumulation exceeds sheet wash or weathering soil formation rates if the rate of dust accumulation is less than that of surface erosion or of soil biogenetic processes the dust then develops into soil or through intensive weathering and increased precipitation into loam or clay only part of the aeolian dust transported and deposited in a zone suitable for loess formation remains there permanently and is transformed in situ into loess dust not affected by diagenesis is usually further transported by snowmelt or rainwash and is only transformed into loess after it has been redeposited the loess itself however is easily erodible and its minerals are readily reworked and reaccumulated and given the appropriate conditions it readily undergoes diagenesis again we do not always have sufficient evidence to determine whether a given loess body is of primary or secondary origin traditionally the minerals making up primary loess have been regarded as originating in dust accumulated by aeolian processes secondary loess by contrast is different from typical loess in many ways and it is not unusual to find various loess series in which superimposed dust fractions have been transformed into loess by different processes recently we have observed that the origin of various types of loess is governed by differences in litho ecological conditions rather than by the way in which the mineral material from which the loess is derived dust has been primarily accumulated loessification is therefore determined by environmental conditions

quantitative estimates of the effect of climate change on dust storm activity in australia during the last glacial maximum quantitative estimates are made of the effect of climate change upon dust activity during the last glacial maximum lgm which peaked 18 000 years ago using present day measurements of the occurrence of dust storms recalculated in the light of information on lgm climatic change dust activity was increased by 57 in northeast australia and by 52 in the southeast in relation to present day dust storm seasons were lengthened and dust paths were modified estimates based upon climate alone without considering the increased supplies of sediment to dust source areas during the lgm however probably underestimate lgm dust activity

aeolian modification of moraine soils whiskey basin wyoming usa soils along catenas of pinedale 15 20 ka and bull lake 100 130 ka age moraines at whiskey basin in the wind river range wyoming usa were sampled to assess the effects of aeolian processes on soil development here aeolian processes appear to have in uenced soils by both depositing sediments and eroding topsoils pedogenic silt often used as an indicator of wind deposition accumulated in the bull lake soils moderately correlate with pedogenic clay accumulated suggesting that ne sediments may have been deposited and incorporated into soil formation here following removal of previous topsoil by wind during pinedale glaciation bull lake b horizons have developed into contemporary a horizons these data further link aeolian processes to soil development on piedmont moraines throughout the wind river range copyright 2004 john wiley sons ltd

multiple sources supply eolian mineral dust to the atlantic sector of coastal antarctica evidence from recent snow layers at the top of berkner island ice sheet the sr and nd isotopic composition of dust extracted from recent snow layers at the top of berkner island ice sheet located within the filchner ronne ice shelf at the southern end of the weddell sea enables us for the first time to document dust provenance in antarctica outside the east antarctic plateau eap where all previous studies based on isotopic fingerprinting were carried out berkner dust displays an overall crust like isotopic signature characterized by more radiogenic 87sr 86sr and much less radiogenic 143nd 144nd compared to dust deposited on the eap during glacial periods differences with eap interglacial dust are not as marked but still significant indicating that present day berkner dust provenance is distinct at least to some extent from that of the dust reaching the eap the fourteen snow pit sub seasonal samples that were obtained span a two year period 2002 2003 and their dust sr and nd isotopic composition reveals that multiple sources are at play over a yearly time period southern south america patagonia in particular likely accounts for part of the observed spring summer dust deposition maxima when isotopic composition is shifted towards younger isotopic signatures in the spring possible additional inputs from australian sources would also be supported by the data most of the year however the measured isotopic signatures would be best explained by a sustained background supply from putative local sources in east antarctica which carry old crust like isotopic fingerprints whether the restricted east antarctic ice free areas produce sufficient eolian material has yet to be substantiated however the fact that large 5 mu m particles represent a significant fraction of the samples throughout the entire time series supports scenarios that involve contributions from proximal sources either in patagonia and or antarctica possibly including snow free areas in the antarctic peninsula and other areas as well this also indicates that additional dust transport which does not reach the eap must occur at low tropospheric levels to this coastal sector of antarctica

recent expansions of glacial lakes in the bhutan himalayas current conditions and secular changes in ice contact lakes in the bhutan china border region were investigated using satellite imagery more than 50 moraine dammed ice contact or ice proximal lakes were identified of which 14 were evidently growing in debris covered areas of valley glaciers lake growth is characterised by the initial appearance of supraglacial lakes and subsequent upstream expansion by a coalesced lake in small debris free or partially debris covered glaciers lake growth begins from a single lake lake growth has continued over a period ranging from 20 to 70 years with a growth rate of 70 m year in length and 0 04 km2 year in area these values observed at the northern side of the main himalayan range are smaller than those observed at the southern side the initial appearance year estimated from the expansion rate of most of the lakes in the southern and northern sides ranges from the 1950s to the 1970s and before the 1950s respectively

meteorological controls on wind erosion during foehn wind events in the eastern southern alps new zealand foehn winds in the lee of mountain barriers create highly favourable meteorological conditions for wind erosion in alpine areas and over adjacent lowlands this paper presents meteorological observations made during winter and summer foehn wind erosion events as part of a 3 year investigation into the physical nature and incidence of eolian processes in the eastern southern alps new zealand foehn winds were observed to initiate eolian activity including dust storm genesis when mean near surface wind speeds exceeded 7 8 m s 1 over a 20 min period in the absence of precipitation wind speeds of 25 30 m s 1 were frequently recorded during typical foehn events and wind speed maxima of 40 50 m s 1 were monitored during severe foehn windstorms saltation clouds sampled at 0 5 and 1 m above glaciofluvial deposits during foehn wind erosion events were found to display a mean grain size of between 300 and 435 m the entrainment of fine grained surface sediments by the airstream appeared to be enhanced in late autumn may and early spring september by freeze thaw cycles that were observed to result in needle ice growth in exposed glaciofluvial and lacustrine deposits the needle ice fragmented such deposits producing surfaces that were aerodynamically rough and highly susceptible to deflation by the airstream following a thaw observations made by this study are thought to be similar to foehn wind erosion events reported in the lee of other substantial mountain ranges such as the rocky mountains andes hindu kush and karakoram

suspended sediment from the gangotri glacier quantification variability and associations with discharge and air temperature abstract to understand the sediment delivery variation for a himalayan glacier gangotri glacier garhwal himalayas and to determine its relationship with discharge and air temperature suspended sediment samples and discharge data were collected near the glacier snout 4000 m for four melt seasons during the period 2000 2003 these data were used to estimate suspended sediment concentration ssc suspended sediment load ssl sediment yield and erosion rate in the glacier melt stream bhagirathi the monthly distribution of suspended sediment and its variability from year to year have been examined mean monthly ssc for may june july august september and october were found to be 1942 2063 3658 2551 734 and 136 mg l 1 respectively maximum ssc in meltwater was observed in july followed by august it was found that the cumulative percentage delivery of ssc precedes discharge throughout the melt season mean monthly total ssl for may june july august september and october during the study period was found to be 149 423 1220 746 143 and 5 10 3 ton respectively the strong variability is found in ssl c v 1 1 than ssc c v 0 8 because computation of ssl includes both discharge c v 0 6 and ssc delivery response of ssl in terms of percentage of total load is less in the early part of the melt season than in the later stage in comparison to that of discharge this may be due to the fact that in the beginning of the melt season low melt rate conditions prevails and thus the low discharge velocity could not flush out stored glacial sediment it has been observed that 59 64 of the sediment passed through the channel by the time 50 of the total discharge passed the average suspended sediment yield for the whole melt season from the study area was estimated to be about 4834 ton km 2 and corresponding erosion rate was 1 8 mm the relationship between mean monthly ssc and discharge r 2 0 99 is much better than the daily ssc and discharge r 2 0 40 because variability of both parameters is averaged out on monthly scale mean monthly ssc and mean monthly ssl provide a good exponential relationship with mean monthly air temperature these results are relevant for planning and management of water resources in the high altitude areas and for designing hydropower projects

the signature of river and wind borne materials exported from patagonia to the southern latitudes a view from rees and implications for paleoclimatic interpretations abstract riverine and wind borne materials transferred from patagonia to the sw atlantic exhibit a homogeneous rare earth element ree signature they match well with the ree composition of recent tephra from the hudson volcano and hence this implies a dominance of material supplied by this source and other similar andean volcanoes due to the trapping effect of proglacial and reservoir lakes the larger patagonian rivers deliver to the ocean a suspended load with a slightly modified andean signature that shows a ree composition depleted in heavy rees in this paper we redefine patagonia as a source of sediments which is in contrast with other sources located in southern south america quaternary sediments deposited in the northern and to a lesser extent in the southern scotia sea and most of the dust in ice cores of east antarctica have ree compositions very similar to the loess from buenos aires province and to patagonian eolian dust however we rule out buenos aires province as a holocene major source of sediments similarly to buenos aires loess a proximal facies it is likely that the ree compositions of most sediment cores of the scotia sea and antarctica reflect a distal transport of dust with an admixed composition from two main sources a major contribution from patagonia and a minor proportion from source areas containing sediments with a clear upper crustal signature e g western argentina or from bolivia s altiplano evidence indicates that only during the last glacial maximum patagonian materials were the predominant sediment source to the southern latitudes

dust sources and deposition during the last glacial maximum and current climate a comparison of model results with paleodata from ice cores and marine sediments mineral dust aerosols in the atmosphere have the potential to affect the global climate by influencing the radiative balance of the atmosphere and the supply of micronutrients to the ocean ice and marine sediment cores indicate that dust deposition from the atmosphere was at some locations 2 20 times greater during glacial periods raising the possibility that mineral aerosols might have contributed to climate change on glacial interglacial time scales to address this question we have used linked terrestrial biosphere dust source and atmospheric transport models to simulate the dust cycle in the atmosphere for current and last glacial maximum lgm climates we obtain a 2 5 fold higher dust loading in the entire atmosphere and a twenty fold higher loading in high latitudes in lgm relative to present comparisons to a compilation of atmospheric dust deposition flux estimates for lgm and present in marine sediment and ice cores show that the simulated flux ratios are broadly in agreement with observations differences suggest where further improvements in the simple dust model could be made the simulated increase in high latitude dustiness depends on the expansion of unvegetated areas especially in the high latitudes and in central asia caused by a combination of increased aridity and low atmospheric co2 the existence of these dust source areas at the lgm is supported by pollen data and loess distribution in the northern continents these results point to a role for vegetation feedbacks including climate effects and physiological effects of low co2 in modulating the atmospheric distribution of dust

rapid deglaciation as an initiator of volcanic activity an hypothesis volcanic activity on sub antarctic marion island is found to have occurred only during the interglacials the present volcano distribution is associated with a radial and peripheral fault system the location of which appears to be related to the former glacier distribution an hypothesis is presented suggesting that the faulting is a result of deglaciation and that the specific location of the faults is due to the differential stresses occurring between ice covered and ice free areas during isostatic uplift the faulting initiates volcanism due to the location of the island within a volcanic region

proglacial sediment trapping in recently formed silt lake upper lillooet valley coast mountains british columbia the sedimentology of proglacial silt lake was assessed by lake sediment coring and monitoring of lacustrine processes during a late summer period of high glacier melt to characterize sediment delivery from the heavily glacierized catchment and investigate the sediment trapping dynamics of this upland lake a complete varve chronology was established for a distal basin of the lake which was exposed by lillooet glacier retreat between 1947 and 1962 the varve record showed decreasing sedimentation rates in the basin while the glacier retreated and as the lake became free of ice contact in the early 1970s although recession has continued over recent decades and glacier proximity to the lake has therefore continued decreasing lacustrine sedimentation rates are now accelerating due to changing basin morphometry caused by delta progradation over shorter time scales lake sedimentation patterns respond to changing runoff conditions including late summer glacier melt intensity intra annual flooding events diumal runoff fluctuations and within lake turbidity currents turbidity currents included quasi regular flows during high diurnal discharges and an episodic flushing of temporarily stored sediment from the sandur or delta at a time of low stage suspended sediment yield to silt lake is estimated to exceed 103 mg km 2 a 1 a magnitude that surpasses previous local and regional yield estimates for the glacierized headwaters of the lillooet river valley since silt lake currently traps a significant prooportion of that upland sediment supply and the trapping efficiency of the basin has been variable at decadal time scales the formation and continued development of lilt lake has likely had a significant influence on downstream sediment delivery lacustrine sediment based proxies of long term hydroclimatic variability being developed in glacially distal settings should include provisions for dynamic sediment trapping effects in upstream water bodies that often form in the active proglacial environment copyright 2008 john wiley sons ltd

the nature origin and accumulation of loess abstract loess can be defined simply as a terrestrial clastic sediment composed predominantly of silt size particles which is formed essentially by the accumulation of wind blown dust there are three fundamental requirements for its formation 1 a sustained source of dust 2 adequate wind energy to transport the dust and 3 a suitable accumulation site most loess has been modified to some degree by local reworking bioturbation and syn depositional weathering but a process of loessification is not necessary for a dust deposit to qualify as loess the terms primary loess and secondary loess have previously been used to described wind deposited loess and redeposited loess respectively but it is more accurate to describe material reworked and redeposited by non aeolian processes as loess derived colluvium or loess derived alluvium during the quaternary loess formed in three main situations 1 mid continental shield areas beyond the limits of ice sheets periglacial loess 2 on the margins of high mountain ranges perimontane loess and 3 on the semi arid margins of some lowland deserts peridesert loess peridesert loess is relatively poorly developed partly due to the limited efficiency of silt generating mechanisms in low land deserts compared with glaciation but also important is the tendency in arid areas for dust to be dispersed over a wide area and to be rapidly reworked after deposition particularly in areas which experience frequent climatic changes the remarkably thick loess of china and central asia results from an unusual combination of conditions which has persisted for much of the last 2 3 million years namely rapid uplift of the tibetan plateau and surrounding mountain ranges high rates of sediment production and supply to adjacent basins a strong northwesterly and westerly wind regime and the existence of effective dust traps downwind of the source regions

soil development along primary succession sequences on moraines of hailuogou glacier gongga mountain sichuan china abstract soil properties related to soil development were measured in six profiles over approximately 180 years of soil development on recessional moraines of the hailuogou glacier sichuan of southwestern china it is hypothesized that soil development is strictly time dependent field and laboratory work indicate that as soil develops from initially coarse gravel outwash the properties undergo a progressive physical and chemical change such that there is a considerable profile differentiation between the youngest and the oldest soils the ph is also highly stratified it decreases with time from 8 5 to 4 2 in the upper mineral soil and increases with depth in all profiles accumulation of soil organic c and n increases with time but the rates of accumulation become slower with time within the investigated timespan soil c and n accumulated to a considerable level of 3 5 and 0 6 kg m2 respectively with mean annual rates of 28 g m2 for carbon and 3 5 g m2 for nitrogen the rapid accumulation of organic c and n accelerates the processes of soil formation but the content of organic c and n did not reach a steady state during the observed timespan the accumulation of soil organic matter results in increased acid production and in the chemical weathering of minerals that promote formation and translocation of the clay fraction and leaching of carbonate it is also directly responsible for development of soil properties such as cation exchange capacity cec and bulk density

influences of eolian and pedogenic processes on the origin and evolution of desert pavements well developed desert pavements are present above eolian deposits that mantle flows of the cima volcanic field located in the mojave desert california soil stratigraphic data and geochemical data demonstrate that eolian and pedogenic processes play major roles in the evolution of these pavements eolian dust 1 accelerates mechanical fragmentation of flow rock providing the source material for pavements and 2 accumulates slowly below basaltic colluvium in flow depressions eventually promoting development of cumulate soils below the evolving stone pavement an increase in dust flux during the holocene has raised ancient pleistocene pavements as much as 20 cm above the former land surface the results of our studies demonstrate for the first time that most desert pavements do not form by deflation by overland flow or by upward migration of stones through a slowly formed clayey argillic horizon desert pavements are born and maintained at the surface

prolonged seismically induced erosion and the mass balance of a large earthquake large earthquakes deform the earth s surface and drive topographic growth in the frontal zones of mountain belts they also induce widespread mass wasting reducing relief the sum of these two opposing effects is unknown using a time series of landslide maps and suspended sediment transport data we show that the mw7 6 chi chi earthquake in taiwan was followed by a period of enhanced mass wasting and fluvial sediment evacuation peaking at more than five times the background rate and returning progressively to pre earthquake levels in about six years therefore it is now possible to calculate the mass balance and topographic effect of the earthquake the choshui river has removed sediment representing more than 30 of the added rock mass from the epicentral area this has resulted in a reduction of surface uplift by up to 0 25 m or 35 of local elevation change and a reduction of the area where the chi chi earthquake has built topography for other large earthquakes erosion may evolve in similar predictable ways reducing the efficiency of mountain building in fold and thrust belts and the topographic expression of seismogenic faults prolonging the risk of triggered processes and impeding economic regeneration of epicentral areas

change in atmospheric mineral aerosols in response to climate last glacial period preindustrial modern and doubled carbon dioxide climates desert dust simulations generated by the national center for atmospheric research s community climate system model for the current climate are shown to be consistent with present day satellite and deposition data the response of the dust cycle to last glacial maximum preindustrial modern and doubled carbon dioxide climates is analyzed only natural non land use related dust sources are included in this simulation similar to some previous studies dust production mainly responds to changes in the source areas from vegetation changes not from winds or soil moisture changes alone this model simulates a 92 33 and 60 change in dust loading for the last glacial maximum preindustrial and doubled carbon dioxide climate respectively when impacts of carbon dioxide fertilization on vegetation are included in the model terrestrial sediment records from the last glacial maximum compiled here indicate a large underestimate of deposition in continental regions probably due to the lack of simulation of glaciogenic dust sources in order to include the glaciogenic dust sources as a first approximation we designate the location of these sources and infer the size of the sources using an inversion method that best matches the available data the inclusion of these inferred glaciogenic dust sources increases our dust flux in the last glacial maximum from 2 1 to 3 3 times current deposition

influence of the orographic roughness of glacier valleys across the transantarctic mountains in an atmospheric regional model glacier valleys across the transantarctic mountains are not properly taken into account in climate models because of their coarse resolution nonetheless glacier valleys control katabatic winds in this region and the latter are thought to affect the climate of the ross sea sector frsater formation to snow mass balance the purpose of this paper is to investigate the role of the production of turbulent kinetic energy by the subgrid scale orography in the transantarctic mountains using a 20 km atmospheric regional model a classical orographic roughness length parametrization is modified to produce either smooth or rough valleys a one year simulation shows that katabatic winds in the transantarctic mountains are strongly improved using smooth valleys rather than rough valleys pressure and temperature fields are affected by the representation of the orographic roughness specifically in the transantarctic mountains and over the ross ice shelf a smooth representation of escarpment regions shows better agreement with automatic weather station observations than a rough representation this work stresses the need to improve the representation of subgrid scale orography to simulate realistic katabatic flows this paper also provides a way of improving surface winds in an atmospheric model without increasing its resolution

palaeoclimate patagonian dust machine most of the dust in antarctic ice cores originates in the glacial outwash of patagonia sedimentary evidence suggests that during the last glacial period pro glacial lakes provided an on off switch for the dust flux to antarctica

loess is almost totally formed by the accumulation of dust in 1990 marton pecsi published a paper entitled loess is not just the accumulation of dust this 1990 paper presented the case for considering aspects of loess formation other than the aeolian deposition of silty material pecsi argued that there is more to loess formation than simply the fact of aeolian deposition while not disputing the validity of much of pecsi s arguments a case can be made for considering that aeolian deposition is at the very heart of loess formation that the factor of aeolian deposition is so critical that other aspects are relatively unimportant pecsi appeared to suggest that aeolian deposition is just one of many factors relating to the formation of loess deposits this is not so aeolian deposition and the consequent formation of metastable structures is absolutely central but it is probably useful to consider the aeolian deposition is absolutely critical approach and the aeolian deposition is one of the factors approach in some more detail and in relation to each other some insights may accrue interesting things do happen after the deposition of the dust and this needs to be acknowledged

simulation of atmospheric circulation during the gimex 91 experiment using a meso γ primitive equations model a meso gamma scale atmospheric model has been used to simulate atmospheric circulations observed during the greenland ice margin experiment gimex the simulations shown here are two dimensional and cover the 12 13 july 1991 period a typical summer situation in this area the synoptic scale wind forcing is included the tundra topography is assumed to be either flat or averaged over a 50 km wide cross section centered on the gimex transect simulated wind temperature humidity and turbulent fluxes compare reasonably well with available observations the simulated heat used to melt snow or ice is also shown the sensitivity of the model results to the synoptic scale wind forcing is significant the impact of a tundra much warmer than the ocean on the ice sheet melting is discussed it is found that weak easterly synoptic scale winds are able to overwhelm this impact especially when the tundra is assumed to be flat

dust transportation and deposition in a superhumid environment west coast south island new zealand contemporary rates of dust deposition monitored along a 300 km section of the superhumid west coast of new zealand s south island are presented in this setting dust is entrained primarily from the dry channels of braided glaciofluvial rivers that drain the western slopes of the southern alps measured dust deposition ranged between 0 21 and 118 9 kg 1 ha 1 month 1 which is similar to dust deposition rates monitored in arid and semiarid environments however these are not considered to be sufficient for present day loess genesis dust deposition was highest in summer because of the greater frequency of favourable dust transporting winds and the effect of rainfall was secondary dust transportation occurred mainly during the passage of nonprecipitating cold fronts or postfrontal southwesterlies transportation also occurred during prefrontal conditions and in winter fohn southeasterlies were the predominant dust transporting winds to affect the west coast

mechanisms of loess sized quartz silt production and their relative effectiveness laboratory simulations the production of loess sized quartz silt is frequently ascribed to glacial grinding mechanisms in this study a series of laboratory simulations was set up the purpose of which was to demonstrate that a range of geomorphic mechanisms are capable of producing silt under laboratory conditions the geomorphic mechanisms investigated were aeolian abrasion fluvial comminution glacial grinding salt weathering and frost weathering the results confirmed that under laboratory conditions all of these mechanisms were capable of producing silt the relative effectiveness of these mechanisms at producing silt under laboratory conditions was then calculated in order to provide a starting point for a consideration of their potential effectiveness within the natural environment these results indicate that fluvial and aeolian activity are highly effective at producing quartz silt over short time periods in a dust storm of four days duration 287 g of silt could potentially be produced from every kilogram of sand entrained while fluvial comminution in a turbulent fluvial environment could potentially produce 900 g of silt from every kilogram of sand entrained within 32 h over longer periods of time the glacial grinding and weathering mechanisms represent more continuous and hence more effective silt producing mechanisms although it is realised that the relative importance of each silt producing mechanism will differ spatially and temporally due to differences in climate relief geology and geomorphic history the findings from this work do have implications for the genesis of loess deposits they demonstrate that glacial and cold weathering processes are not solely responsible for fine particle formation and that efficient silt producing mechanisms can operate within a variety of environments under suitable conditions weathering together with episodic contributions from aeolian and fluvial mechanisms could be responsible for a considerable proportion of global quartz silt production

contemporary glacigenic inputs to the dust cycle the importance of glacigenic dust in the earth s system during glacial periods is widely acknowledged under contemporary conditions the world s largest dust sources are in low lying hot arid regions and this is where most aeolian research is focused however the processes of dust production and emissions are still operating in cold climate regions particularly in proglacial areas this paper assesses current understanding of the relationship between glacierised landscapes and dust emissions and inputs to the global dust cycle it focuses on how elements in the glacial and aeolian geomorphic sub systems interact to determine the magnitude frequency and timing of aeolian dust emissions and on feedback mechanisms between the systems where they have been measured dust emission intensity and deposition rates in glacierised catchments are very high in some cases far exceeding those in lower latitudes however few studies span long time scales the impact of future glacier retreat on the balance between sediment supply availability and aeolian transport capacity and implications for glacigenic dust emissions is also considered this balance depends on relative spatial and temporal changes in meltwater suspended sediment concentration and wind strengths which promote dust emissions and patterns and rates of soil development and vegetation succession on recently deglaciated terrain which protect sediments from deflation retreat of the antarctic ice sheet could mean that in future glacigenic contributions to the dust cycle exceed those of non glacigenic sources in the southern hemisphere copyright 2012 john wiley sons ltd

variations in sediment yield over the advance and retreat of a calving glacier laguna san rafael north patagonian icefield abstract bathymetric and sub bottom acoustic data were collected in laguna san rafael chile to determine sediment yields during the little ice age advance and subsequent retreat of san rafael glacier the sediment volumes and subaqueous landforms imaged are used to interpret the proglacial dynamics and estimate erosion rates from a temperate tidewater glacier over a complete advance retreat cycle sediment yields from san rafael glacier averaged 2 7 107 m3 a since the end of the little ice age circa ad 1898 corresponding to average basin wide erosion rates of 23 9 mm a the highest erosion rates 68 23 mm a occurred at the start of the retreat phase and have since been steadily decreasing erosion rates were much lower during glacial advance averaging at most 7 mm a than during retreat such large glacial sediment yields over two centuries of advance and retreat suggest that the contribution of sediments stored subglacially cannot account for much of the sediment being delivered to the terminus today the detailed sub bottom information of a proglacial lagoon yields important clues as to the timing of erosion deposition and transfer of glacigenic sediments from orogens to the continental shelves and the influence of glacier dynamics on this process

aeolian transport of sediment on a beach during and after rainfall wildwood nj usa abstract a field investigation was conducted 9 march 1994 on a dissipative beach to compare wind characteristics and aeolian transport during and after a light rain winds blew alongshore during the monitoring period moisture content of surface sediment on the backbeach was above 7 during rain and 4 four hours after rainfall ceased trapping rates measured using a cylindrical vertical trap were 14 1 kg m 1 h 1 during rainfall and 140 2 kg m 1 h 1 for a period beginning 3 h 33 min after rainfall ceased results indicate that light rain resulting in bulk surface moisture values over 7 is not sufficient to eliminate transport but the rate of transport is lower than can occur on the beach three to four hours following rain the amount of sand trapped at wildwood during rainfall is relatively high when compared to many previous studies on beaches in the absence of rain the great length of the beach as a source area combined with parallel or oblique winds are significant in increasing rates of sediment transport

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

late glacial and holocene small mammals of the timan ridge komi republic russia abstract small mammal remains from five karst type localities situated in the southern and middle timan region are presented three different faunal assemblages from three succeeding phases are recognized a cryohydrophilous faunal assemblage with desman desmana moschata and predominantly siberian lemming lemmus sibiricus existed during the bolling allerod interstadials during the end of younger dryas the fauna changed to cryoxerophilous communities with a predominance of collared lemming dicrostonyx sp and narrow skulled vole microtus gregalis the forest fauna is typical for the late holocene until the early holocene the middle timan region was a refugium of dicrostonyx populations characterized by archaic molar morphology

reconstructing hydro climatic events and glacier fluctuations over the past millennium from annually laminated sediments of cheakamus lake southern coast mountains british columbia canada abstract we recovered sediment cores from cheakamus lake in the southern coast mountains southwest british columbia to reconstruct late holocene environmental conditions in the watershed the cored sediments are inorganic rhythmically laminated clayey silt radiocarbon ages and correlation of lamina thickness with the magnitude of the annual flood recorded at a nearby gauging station indicate that the laminae are varves we discriminate seven types of varves on the basis of couplet thickness and internal structure and compare them to annual hydrographs over the period of record the seven varve types record summer snowmelt floods autumn floods mid season floods years with two major floods years with three major floods years with more than three major floods and periods of sustained glacier runoff varves attributed to autumn storms and glacier runoff are dominant exhibit serial dependence and are most common during six periods ad 1300 1320 1380 1410 1470 1500 1710 1730 1880 1906 and 1916 1945 in contrast varves attributed to summer snowmelt floods are randomly distributed through time thickest varves occur during the decades ad 1090 1110 1120 1170 1210 1250 1310 1330 1390 1450 1720 1780 1860 1900 and 1920 1945 the relation between little ice age glacier activity and lake sedimentation is complex but the thickest varves coincide with times of rapid glacier retreat and periods when air temperatures were warmer than average the results confirm the importance of sediment transfers during the summer and autumn runoff season in the british columbia coast mountains

scale variation of post glacial sediment yield in chilliwack valley british columbia the holocene volumetric sediment budget is estimated for coarse textured sediments sand and gravel in a large formerly glaciated valley in southwest british columbia erosion is estimated by compiling volumetric loss estimated in digital elevation models dems of gullied topography and by applying a non linear diffusion model on planar undissected hillslopes estimates of steepland yield are based on estimates of post glacial deposition volumes in fans cones and deltas at the outlets of low order tributary catchments erosion of post glacial fans and tributary valley fills is estimated by reconstructing formerly continuous surfaces results are classed by catchment order and compared across scales of contributing area revealing declining specific sediment yield in m3 km 2 a 1 with catchment area for the smaller tributaries 10 km2 and increasing specific sediment yield for larger tributaries and chilliwack valley itself approximately 60 of mobilized sediment is redeposited in first to third order catchments with lesser proportions stored at the outlets of higher order catchments a simple network routing model emphasizes the significant sediment flux contributions from colluvium drift blankets and gullies in steeper terrain as this material is deposited at junctions within the lower drainage network an increasing proportion of material is derived from remnant valley fills and para glacial fans in the major valleys yield from lower order steepland catchments tends to remain in storage indefinitely sequestered on footslopes these observations have implications for modelling the post glacial sediment balance amongst catchments of varying size after 104 years the system remains in disequilibrium the critical linkage lies between low order hillslope catchments fourth order and the larger valleys with more complex fluvial systems copyright 2010 john wiley sons ltd

the role of aeolian dust in ecosystems abstract the recent upsurge in research attention to aeolian dust has shown that dust transport systems operate on very large spatial and temporal scales and involve much larger quantities of sediment than was previously realized an inevitable consequence of this is that researchers from a range of neighbouring disciplines including ecology are beginning to realize that this new knowledge has important implications for their study areas in the present paper we examine the ecological implications real and potential of this expanding knowledge of dust transport systems with a particular emphasis upon the australian dust transport system we track these ecological effects from source to sink at source wind erosion soil vegetation relationships are often dominated by temporal changes in rainfall nine years of measurements in the channel country of the lake eyre basin australia show that vegetation and soils in dune fields can recover from drought whereas on inter fluve grasslands uni directional and negative successional vegetation changes can result from wind erosion during drought on floodplains both wind erosion and vegetation responses are complicated by flood frequency up to 1999 flooding of saline claypans did not increase vegetation but did increase wind erosion through the supply of alluvial fines however after three floods within as many months vegetation became established and wind erosion rates were dramatically reduced wind erosion research attention is now gradually turning from the physical to the organic content of eroded dusts in australia organic matter content can reach 65 by mass but this cannot be explained by removal of soil organic matter alone biological soil crusts not only stabilize soils against wind erosion but contribute to some of the organic dusts the role of dust as a vector for pathogens is an area which deserves greater research attention in the future downwind from source we show that dust contributions to soils are more widespread and more variable in time and space than earlier work on dust derived loess soils has suggested recent studies also show positive dust impacts upon nutrient budgets within distant forest ecosystems and significant contributions to river nutrient loads especially in the arid sectors of internally draining river basins the number of studies of dust impacts upon marine ecosystems is increasing dramatically studies of dust within antarctic ice cores combined with dust modelling provide compelling evidence that increased soluble iron rich dust inputs to the southern ocean have stimulated phytoplankton populations modern process studies are however yet to clearly demonstrate these relationships finally we examine the potential for major dust impacts upon global climates using its positive and negative effects upon solar radiation and precipitation as examples of the complexity and importance of this new research area