glaciations of the west coast range tasmania geomorphic stratigraphic palynologic and 14c evidence indicates that the west coast range tasmania was glaciated at least three times during the late cenozoic the last or margaret glaciation commenced after 30 000 yr b p culminated about 19 000 yr b p and ended by 10 000 yr b p during this period a small ice cap ca 250 m thick and cirque and valley glaciers covered 108 km2 the glacial deposits show little chemical weathering or erosional dissection the snow line ranged from 690 to 1000 m with an average of 830 m for the ice cap mean temperature was 6 5 c below the present temperature during the preceding henty glaciation a 300 to 400 m thick ice cap and outlet glaciers exceeded 1000 km2 the glacial deposits are beyond 14c assay they are more weathered chemically and more dissected than margaret age deposits and the degree suggests a pre last interglaciation age 130 000 yr b p the snow line of the ice cap lay at 740 m and annual temperature was reduced by 7 c ice of the earliest linda glaciation slightly exceeded that of the henty glaciation but had a similar distribution the glacial deposits are intensely weathered have reversed magnetization and overlie a paleosol containing pollen of tertiary type an early pleistocene or tertiary age is indicated

sources sinks and storage of river sediment in the atlantic drainage of the united states the history of sediment and its movement in the atlantic drainage demonstrate some of the difficulties of modeling sediment on a river basin scale soil erosion was accelerated by a factor of at least 10 when european settlers cleared forests and planted crops although increasing soil conservation practice and decreasing crop farming have since reduced the rates of erosion large quantities of eroded material are still stored on hillslopes and in stream valleys where they continue to augment the sediment loads of the rivers the sediment from this episode of erosion that is largely past can be expected to emerge from storage for many decades and perhaps even several centuries to come the reservoirs that have been built on many of the major rivers trap significant portions of the moving sediment which in some places may be remobilized by large floods essentially all the river sediment that reaches the atlantic coastal zone is trapped in estuaries and coastal marshlands probably less than 5 is deposi

a snow transport model for complex terrain as part of the winter environment in middle and high latitude regions the interactions between wind vegetation topography and snowfall produce snow covers of non uniform depth and snow water equivalent distribution a physically based numerical snow transport model snowtran 3d is developed and used to simulate this three dimensional snow depth evolution over topographically variable terrain the mass transport model includes processes related to vegetation snow holding capacity topographic modification of wind speeds snow cover shear strength wind induced surface shear stress snow transport resulting from saltation and suspension snow accumulation and erosion and sublimation of the blowing and drifting snow the model simulates the cold season evolution of snow depth distribution when forced with inputs of vegetation type and topography and atmospheric foreings of air temperature humidity wind speed and direction and precipitation model outputs include the spatial and temporal evolution of snow depth resulting from variations in precipitation saltation and suspension transport and sublimation using 4 years of snow depth distribution observations from the foothills north of the brooks range in arctic alaska the model is found to simulate closely the observed snow depth distribution patterns and the interannual variability

bagnold s kink a physical feature of a wind velocity profile modified by blown sand bagnold 1941 made detailed measurements of the wind profile modified by blown sand he noted that each velocity profile appeared to be kinked and suggested that the position of the kink corresponded to the height at which an average or a characteristic trajectory extracted the bulk of its momentum from the wind however anderson and haff 1988 have shown that in aeolian sand transport the grain cloud is made up from a distribution of trajectory paths and that it was an over simplification to attempt to describe the complex behaviour of the grain cloud in terms of a single representative trajectory these recent developments leave the nature and even the existence of the kink observed by bagnold 1941 open to question this paper shows that a kink is indeed a physical feature of the modified wind velocity profile and that it is caused as bagnold 1941 suggested by a maximum occurring at some height above the surface in the momentum extracted by the grains from the wind further comments are made on both the form of the modified wind velocity profile and the fluid shear stress profile in the grain layer in particular these comments based upon a theoretical analysis suggest an experimental means to measure the mean surface fluid shear stress and to gain from accurately measured wind profiles a greater insight into the grain cloud which caused the modification

observations of cross ridge flows across steep terrain a field experiment gaudex has been conducted to address the need for quantitative measurements of turbulence in the vicinity of steep terrain a dense network of automatic weather stations and turbulence towers was deployed along cross ridge transects over gaudergrat a steep triangular cross section ridge in eastern switzerland a new feature whereby ridge normal cross ridge flows develop at the crest even when the flow in each valley is oriented parallel to the ridge axis is identified this occurs independently of whether the flow is thermally or synoptically driven pressure measurements across the ridge show that this flow is driven by a cross ridge pressure gradient two mechanisms for generating cross ridge flows have been identified from measurements of pressure wind and temperature in most cases the pressure gradient arises from a difference in flow speeds between the two sides of the ridge caused by different valley geometries less commonly the cross ridge flow is explained by linear speed up of the ridge normal flow copyright 2008 royal meteorological society

palaeoclimatological and chronological implications of the vostok core dust record the2 083 m vostok ice core recovered by the soviet antarctic expeditions has provided much information of climatic and environmental interest for a period covering a full glacial inter glacial cycle1 6 here we present and discuss the dust record obtained down to 2 202 m the final depth to which this core was extended in 1986 first we document the fact that major changes in aeolian deposits as recorded in the vostok core appear to be of global significance and confirm the existence of a link between high latitude aeolian deposits and the earth s orbital parameters7 8 second we propose atmospheric dust as a strati graphic marker to compare timing with other records of palaeocli mate and use the magnetic susceptibility profile measured along the rc11 120 indian ocean core9 for this purpose assuming that major dust events correspond to common aeolian inputs this approach indicates that the vostok and marine records were roughly in phase at the previous glacial interglacial transition

effect of channel bifurcation on residual estuarine circulation winyah bay south carolina the residual circulation pattern of winyah bay the fourth largest estuary on the eastern coast of the us is examined using stationary and shipborne current measurements during periods of low freshwater discharge the estuary has a complex morphology with a single channel and narrow banks at the river entrance and the bay mouth and a bifurcated channel system main and western channels respectively in the middle part that appears to affect the residual circulation overall the upper single channel morphology and middle dual channel morphology parts of the estuary exhibit a baroclinic residual circulation the presence of bifurcated channels in the middle part of the estuary modifies the typical gravitational circulation the near bed landward directed residual flow is stronger in the deeper main channel than the shallower western channel this is the result of the fact that the magnitude of residual flow scales with the water depth of the channel and it is also influenced by the opposing patterns of channel alignment in the northern and southern junctions analytical modeling confirms that the observed residual currents in the upper and middle estuary are density induced in the lower estuary residual flow is directed seaward throughout the water column of the channel while in the adjacent shoals the residual flow is directed landward suggesting that in contrast to the upper and middle estuary the residual flow near the mouth is barotropic controlled by the tides and the channelbank morphology 2005 published by elsevier ltd

vegetation and climate change fire regime shifts and volcanic disturbance in chiloe continental 43 s during the last 10 000 years abstract disentangling the roles of paleofires and explosive volcanism from climatic drivers of past vegetation change is a subject insufficiently addressed in the paleoecological literature the coastal region of the chiloe continental sector of northwestern patagonia is ideal in this regard considering its proximity to active eruptive centers and the possibility of establishing comparisons with more distal upwind sites where volcanic influence is minimal here we present a fine resolution pollen and macroscopic charcoal record from lago teo with the aim of documenting the local vegetation and climate history and assessing the role of disturbance regimes as drivers of vegetation change during the last 10 000 years the lago teo record shows a conspicuous warm dry interval between 7500 and 10 000 cal yrs bp followed by a cooling trend and increase in precipitation that has persisted until the present in agreement with previous studies in the region and interpretations of past southern westerly wind activity at multi millennial scales the presence of 26 tephras throughout the record allows examination of the relationship between explosive volcanism and vegetation change under contrasting climatic states of the holocene we found consistent statistically significant increases in tepualia stipularis after tephra deposition over the last 10 000 years in eucryphia caldcluvia between 7500 and 10 000 cal yrs bp and in hydrangea over the last 7500 years our results indicate a primary role of climate change as driver of long term vegetation change and as a modulator of vegetation responses to volcanic disturbance at multidecadal and centennial timescales

the magnitude and rapidity of the climate change marking the end of the pleistocene in the mid latitudes of south america abstract the chi squared test of independence and cluster analysis of otsuka similarity coefficients of fossil beetle assemblages from the chilean lake region in the mid latitudes of south america support the following conclusions 1 the mean summer temperature of the glacial climate was 4 5 c lower than today s climate 2 the climatic change from glacial to interglacial mode was in a single step centered on about 14 000 yr b p 3 the climatic change was rapid and within 1500 years the biota of a moorland had been completely replaced by a biota of a rain forest 4 by 12 500 yr b p the low elevation beetle fauna of the chilean lake region was similar in composition to that of the present day and 5 no reversal in the postglacial warming trend equivalent in age to the younger dryas stade was detected

full glacial late glacial palaeoclimate of the southern andes evidence from pollen beetle and glacial records palaeoecological studies carried out in the chilean lake district and chilotan archipelago 41 43 s record full glacial and late glacial pollen assemblages beginning just after 21000 and beetle assemblages after 18000 both sets extending until 10000 14c yr bp pollen records indicate that subantarctic parkland the vegetation of the early millennia of record changed after about 14000 yr bp to become open woodland and later north patagonian evergreen forest assemblages of plants and beetles responding more or less in unison to a strong rise in temperature 6 c behaved in accord at around 14000 until 13000 12500 yr bp the beetle fauna displaying a marked increase in obligate forest types during full glacial conditions 17400 16100 and 15300 and 14400 yr bp and in the late glacial interval after about 13000 yr bp however climate evidently coerced populations dissimilarly the pollen sequence showing an increase in plant taxa indicative of colder climate whereas the beetle fauna underwent little or no variation contrasting climate modes implied by plants and beetles may be attributed to differential responses to apparent low order temperature changes 2 3 c

abrupt vegetation changes during the last glacial to holocene transition in mid latitude south america a pollen record from the huelmo site ca 41 30 s shows that vegetation and climate changed at millennial time scales during the last glacial to holocene transition in the mid latitude region of western south america the record shows that a nothofagus parkland dominated the landscape between 16 400 and 14 600 14c yr bp along with magellanic moorland and cupressaceous conifers evergreen north patagonian rainforest taxa expanded in pulses at 14 200 and 13 000 14c yr bp following a prominent rise in nothofagus at 14 600 14c yr bp highly diverse closed canopy rainforests dominated the lowlands between 13 000 and 12 500 14c yr bp followed by the expansion of cold resistant podocarps and nothofagus at ca 12 500 and 11 500 14c yr bp local disturbance by fire favoured the expansion of shade intolerant opportunistic taxa between 10 900 and 10 200 14c yr bp subsequent warming pulses at 10 200 and 9100 14c yr bp led to the expansion of thermophilous summer drought resistant valdivian rainforest trees until 6900 14c yr bp our results suggest that cold and hyperhumid conditions characterised the final phase of the last glacial maximum lgm between 16 400 and 14 600 14c yr bp the last ice age termination commenced with a prominent warming event that led to a rapid expansion of north patagonian trees and the abrupt withdrawal of andean ice lobes from their lgm positon at ca 147 000 14c yr bp hyperhumid conditions prevailed between 16 400 and 13 000 14c yr bp what we term the extreme glacial mode of westerly activity this condition was brought about by a northward shift and or intensification of the southern westerlies the warmest driest conditions of the last glacial interglacial transition occurred between 9100 and 6900 14c yr bp during this period the westerlies shifted to an extreme interglacial mode of activity via a poleward migration of stormtracks our results indicate that a highly variable climatic interval lasting 5500 14c years separate the opposite extremes of vegetation and climate during the last glacial interglacial cycle i e the end of the lgm and the onset of the early holocene warm and dry period copyright 2003 john wiley sons ltd

world wide delivery of river sediment to the oceans new data and new estimates from old data show that rivers with large sediment loads annual discharges greater than about 15 times 10 6 tons contribute about 7 times 10 9 tons of suspended sediment to the ocean yearly extrapolating available data for all drainage basins the total suspended sediment delivered by all rivers to the oceans is about 13 5 times 10 9 tons annually bedload and flood discharges may account for an additional 1 2 times 10 9 tons about 70 of this total is derived from southern asia and the larger islands in the pacific and indian oceans where sediment yields are much greater than for other drainage basins

palaeoclimates in central and south america since 18 000 bp based on pollen and lake level records abstract the last 18 ka of palaeoclimates are discussed at 3 ka intervals based on palaeoenvironmental changes shown in pollen and lake level records from central and south america a total of 61 pollen records fulfill the requirements of continuity and chronology to be used in this synthesis 8 records from tropical and subtropical lowlands in central and south america 7 records from the central american highlands 26 records from the high andes north and south of the equator 2 records from the southern subtropics and 18 from the southern andes and subantarctic islands palaeoclimatic interpretation of the pollen records is semiquantitative based on bioclimatic parameters such as e g elevational temperature gradients or latitudinal precipitation gradients that can be related to vegetation zonation additional palaeoclimatic information is obtained from lake level records derived either from dated shorelines or from the limnological history of lake sediment sections large scale palaeoclimatic comparison of the proxy data records indicates that full and late glacial climates throughout central and south america were cooler than today by about 4 to 5 c but that moisture patterns showed regional differentiation thus in both the southern subtropics and high latitudes in southern chile conditions were substantially moister than today during full and late glacial times whereas everywhere else conditions were far drier than today in terms of palaeocirculation this scenario can be interpreted as a poleward shift of the subtropical as well as the westerly circulation a scenario that has been suggested by palaeoclimatic simulations from general circulation models gcm another major palaeoclimatic aspect predicted by the gcm simulations is the suppressed early holocene summer monsoon in the southern subtropics although proxy records are few from this zone their palaeoenvironmental history during that time shows a period of aridity that would support the model one of the most controversial aspects of south american palaeoclimates concerns the existence of a younger dryas equivalent a cold period between 11 and 10 ka bp based on the existing data from south america that show a great diversity of palaeoclimatic trends the concept of an interval that is characterized by the same climatic signal as documented for the north atlantic seems too simplistic moreover at this point only very few records have been analysed in sufficient detail to yield unambiguous climatic information for the interval in question the principal outcome of this palaeoenvironmental and palaeoclimatic synthesis is the better understanding of the type and quality of data available at present and the realization of regions and periods where much more and concerted effort is needed to address problems of intra and interhemispheric palaeoclimatic correlations only then can questions concerning the mechanism of climatic change be tackled successfully

antiquity of aridity in the chilean atacama desert the atacama desert of northern chile and southern peru has one of the longest histories of arid conditions known although most studies have focused on the hyper aridity prevalent since the miocene all terrestrial sediments in the region from the late triassic onwards also record evaporitic and thus arid climates supergene mineralization in the region did not develop under a more humid climate conducive to deep weathering but under arid conditions these processes may have been facilitated by hydrological changes during miocene uplift and drainage incision but were operational prior to the uplift similarly global cooling and changes to oceanic circulation in the post miocene period only accentuated existing conditions a whole regolith perspective is vital to understanding the history of aridity in the atacama desert and its relevance to arid zone morphogenesis regolith formation and supergene mineralization in particular the long history of aridity raises the possibility that supergene mineralisation under the appropriate conditions form in arid environments instead of requiring humid conditions

pleistocene glaciation in the southern lake district of chile relative age criteria permit deposits of successive andean glacier advances in the southern lake district of chile to be divided into four mappable drift sheets the oldest two of which overlie tertiary bedrock along the eastern flank of the cordillera de la costa only the youngest drift llanquihue is datable by radiocarbon during the most extensive ice advance of the last glaciation the lago llanquihue glacier was about 95 km long and reached an estimated maximum thickness of between 1000 and 1300 m glacier equilibrium lines at that time lay about 1000 m below their present level and rose eastward with a gradient of about 5 m km successive ice advances in the lago llanquihue basin which resulted in construction of end moraines and associated outwash plains beyond the lake margin culminated sometime before about 20 000 yr ago and between 20 000 and 19 000 yr ago a later readvance inferred from the sedimentary record of lake level fluctuations in the basin had begun by about 15 000 yr ago and culminated shortly after 13 000 yr ago a comparable but less closely dated record of ice advances is found northwest of seno reloncavi and on isla chiloe deglaciation following the latest advance is likely to have been rapid for the major glacier lobes fronted on deep water bodies that would have promoted extensive calving

nature of environmental changes in south america at the last glacial maximum abstract a review is given of geomorphological evidence suggesting the nature of environmental changes in south america during the last glaciation maximum lgm the data are from glacial geocryogenic alluvial colluvial and aeolian systems and span 68 of latitude making the most complete land transect of major climatic systems in the southern hemisphere glaciers in the northern and central andes may have reached their maximal extent by 27 000 yr b p reduced precipitation at the lgm caused by lower temperatures and lower atmospheric humidity probably led to slight glacier recession in the tropical andes icefields in the southern andes were most expansive when global temperature and sea level were lowest because pacific westerlies supplied abundant moisture and western outlets advancing across the continental shelf were constrained by sea level low gradient river networks became incised by at least 100 m into narrow channels as global sea level fell by 120 m during the lgm draw down of water tables possibly impacted the forest cover enhancing the drying influence of reduced sea surface temperature and atmospheric humidity as forest and grass covers diminished in extent effecting greater atmospheric cooling because of reduced evapotranspiration and convective condensation colluvial and aeolian processes became more active and widespread almost 25 of the continent is covered with palaeo aeolian features presumed to have been active when airflow was stronger due to steeper atmospheric pressure and temperature gradients at the lgm substantial changes in precipitation totals and incidence and in ground water availability probably eliminated modern type tropical rainforest except in areas currently receiving ca 5000 mm of annual rainfall equivalent changes in vegetation cover spread across much of the guyana and brazilian highlands and throughout the southern temperate regions

palynology of the last interglacial glacial cycle in midlatitudes of southern chile abstract pollen and spores in stratigraphic sections located between 40 and 42 s range in age from the holocene through much of the llanquihue glaciation to the last interglaciation chronology of the stratigraphy derives from some 35 14c ages and the age relations of llanquihue drift and related deposits q mode rotated principal components analysis of four key pollen records covering the last interglacial glacial cycle resulted in four leading components nothofagus dombeyi type gramineae weinmannia fitzroya type and myrtaceae analysis emphasizes interaction between the first two components loadings of gramineae during the interglaciation are high unlike the holocene weinmannia fitzroya type loadings prominent in the holocene are negligible during the interglaciation n dombeyi type is the primary component during llanquihue glaciation it becomes modified by increases of gramineae sometime after 31 000 and before 14 000 yr b p and of myrtaceae later the myrtaceae with weinmannia fitzroya type also registers some activity around 42 000 yr b p fluctuations in the belt of westerly winds reflecting changing meteorological conditions in polar latitudes are suggested by these data with the belt located farther south than it is today interglacial climate was much drier and warmer than during the holocene more northerly displacement of the belt obtained when climate was colder during llanquihue glaciation evidence from comparable latitudes in the southern hemisphere points toward a synchrony of major climatic events indicating harmonious fluctuations in the position of the westerlies

late quaternary vegetation of southern isla grande de chiloe chile late glacial holocene forest history of southern isla chiloe latitude 43 10 s was reconstructed on the basis of pollen analysis in three profiles laguna soledad laguna chaiguata puerto carmen prior to 12 500 yr b p pollen records are dominated by plant taxa characteristic of open habitats zone i from 12 500 yr b p to the present tree species predominate in the pollen records zones ii v between 12 500 and 9500 yr b p ombrophyllous taxa nothofagus podocarpus nubigena myrtaceae fitzroya pilgerodendron and drimys are frequent in all pollen diagrams suggesting a wetter and colder climate than the present between 9000 and 5500 yr b p valdivian forest elements such as nothofagus dombeyi type weinmannia and eucryphia caldcluvia dominate indicating a period of drier and warmer climate from 5500 yr b p onward the expansion of mixed north patagonian subantarctic forest elements and the increased frequence of tepualia suggest increased rainfall and temperatures oscillating around the modern values the change from open to forest vegetation ca 12 500 yr b p probably represents the most pronounced climatic change in the record and can be interpreted as the glacial postglacial transition in the study area

quaternary glaciations of the southern andes abstract the southern andes comprise the southernmost portion of the andean cordillera beginning at the edge of the puna altiplano lat 27 s and ending at isla de los estados lat 55 s the late cainozoic glacial record of these mountains spans the interval from the late miocene to the present and is one of the most complete to be found anywhere in the world this has arisen for several reasons i the conterminous mountain ice cap extended to the piedmont zone on both flanks of the range where the sedimentary and morphological record has been well preserved ii periodic volcanism mainly from monogenetic fissure eruptions of basalt east of the range and from central tephra producing cones along the mountain crest has provided opportunity for the preservation and radiometric dating of interbedded glacial deposits iii a tectonically induced interval of stream incision in the mid pleistocene and simultaneous uplift has preserved glacial sediments on interfluves iv in the chilean lakes region west of the mountains late quaternary glaciers terminated in a well vegetated landscape thus creating scope for radiocarbon dating of interbedded and incorporated organic materials consequently the last glaciation in the llanquihue area of chile is one of the best dated sequences in south america thus the llanquihue glaciation is proposed as the south american equivalent of the wisconsin and weichsel glaciations of north america and north west europe respectively

continental shelf landscapes of the southeastern united states since the last interglacial abstract the wide sediment starved continental shelf and modern coastal areas of the southeastern united states retain well preserved but scattered remnants of a submerged paleolandscape this paper presents a conceptual model of stratigraphic deposition and landscape formation since the last interglacial on the continental shelf of south carolina with portions of north carolina georgia and florida usa data for this study include multibeam bathymetry surveys sidescan sonar mosaics high resolution subbottom profiles and ground truth surveys from 250 m to the modern tidewater region four bathymetric zones are recognized with eleven landforms and landform indicators the described zones range in depths from the modern shoreline across the shelf and over the shelf edge to 250 m msl relative sea level curves are presented for the area and discussed in conjunction with cultural and climatic events the potential for preservation of paleoamerican sites is high at the shelf edge between 130 m and 45 m with archaic and later occupations likely in depths of less than 25 m prominent vantage points for paleoamericans 11 kya would have existed at the shelf edge and tidewater resources would have been available nearby for a period of almost 6 ka rapid transgression rates 60 km ka after the sea level rose over the shelf edge make preservation of tidewater sites less likely on the outer and middle shelf searches for the earliest paleoamericans should focus on promontories at the edge of the shelf and along future discoveries of paleoincisions on the shelf mapping and delineating this paleolandscape and associated unconsolidated sedimentary deposits interspersed with rocky plains and ledges will continue to be a priority to marine archeologists coastal managers fishery scientists and marine spatial planners over the next several decades

measurements and one dimensional model calculations of snow transport over a mountain ridge wind transport of snow can cause an additional snow load on leeward slopes which often has a considerable influence on avalanche danger for a quantitative assessment of this process a model is proposed which calculates the snow transport over a two dimensional mountain ridge based on input measurements of wind speed and precipitation since the topography is idealized the model is focused on the snow mass that is transported over the ridge and no statements are made about the exact snow distribution over the slopes three transport modes are distinguished snow transport in saltation snow transport in suspension and preferential deposition of precipitation suspension is modelled with a one dimensional diffusion equation and for the saltation layer a newly developed model based on the microscale physical processes is implemented the effect of speed up of the wind over the ridge is included by assuming an analytical wind profile with a maximum wind speed at a few meters above the ridge advective effects are taken into account in a parameterization of the turbulent shear stress profile the model is compared with measurements taken at the experimental snowdrift site gaudergrat in the parsenn area switzerland and good agreement is obtained between calculated and measured results

fossil beetle evidence for climatic change 18 000 10 000 years b p in south central chile abstract cold adapted beetles colonized the lowlands of the lake region of south central chile following the retreat of glaciers from their maximum extent at about 19 500 yr b p the beetle fauna from 18 000 to 14 000 yr b p was characterized by species of moorland habitats this fauna was species poor compared to later faunas of the postglacial interval by 14 000 yr b p arboreal species were replacing species of open habitats reflecting a change toward a warmer climate by about 12 500 yr b p fossil beetle assemblages consisted entirely of rain forest species the fauna of the postglacial interval was about five times as species rich as that of the glacial interval the change in species composition and greater diversity of the beetle fauna was produced by an increase in mean annual temperature estimated to be about 4 5 c this was the last major climatic change to affect profoundly the biota of the middle latitudes of south america the fossil beetle assemblages do not imply a reversal to a colder climate at the time of the european younger dryas interval between 11 000 and 10 000 yr b p

snow accumulation distribution inferred from time lapse photography and simple modelling the spatial and temporal distribution of snow accumulation is complex and significantly influences the hydrological characteristics of mountain catchments many snow redistribution processes such as avalanching slushflow or wind drift are controlled by topography but their modelling remains challenging in situ measurements of snow accumulation are laborious and generally have a coarse spatial or temporal resolution in this respect time lapse photography shows itself as a powerful tool for collecting information at relatively low cost and without the need for direct field access in this paper the snow accumulation distribution of an alpine catchment is inferred by adjusting a simple snow accumulation model combined with a temperature index melt model to match the modelled melt out pattern evolution to the pattern monitored during an ablation season through terrestrial oblique photography the comparison of the resulting end of winter snow water equivalent distribution with direct measurements shows that the achieved accuracy is comparable with that obtained with an inverse distance interpolation of the point measurements on average over the ablation season the observed melt out pattern can be reproduced correctly in 93 of the area visible from the fixed camera the relations between inferred snow accumulation distribution and topographic variables indicate large scatter however a significant correlation with local slope is found and terrain curvature is detected as a factor limiting the maximal snow accumulation copyright 2010 john wiley sons ltd

polar perspective of late quaternary climates in the southern hemisphere abstract late quaternary paleoecological and glacial evidence from the higher latitudes of the southern hemisphere implies overall uniformity of large scale glacial and interglacial climatic fluctuations for the past 40 000 yr climate of the last glacial maximum variously dated between 30 000 and 11 000 yr b p was relatively cold and dry compared with the warmer more humid climate of the holocene and the interstade preceding the last glacial maximum conditions were apparently coldest during millennia centered around 20 000 yr b p and warmest in the early holocene recorded small scale fluctuations frequently variable for any given time interval are less consistent a cold late glacial episode estimated as occurring between ca 13 000 and 11 000 yr b p in antarctica possibly was coeval with the younger dryas stade in northwestern europe and may be correlative with a climatic episode in southern south america and perhaps in new zealand and south georgia however there is no evidence for the event in tasmania general atmospheric circulation models for the polar latitudes at the time of the last glacial maximum show an intensification of the southern westerlies apparently a result of the expansion of ice cover in antarctica and of sea ice in the southern ocean

migration of the pee dee river system inferred from ancestral paleochannels underlying the south carolina grand strand and long bay inner shelf several generations of the ancestral pee dee river system have been mapped beneath the south carolina grand strand coastline and adjacent long bay inner shelf deep boreholes onshore and high resolution seismic reflection data offshore allow for reconstruction of these paleochannels which formed during glacial lowstands when the pee dee river system incised subaerially exposed coastal plain and continental shelf strata paleochannel groups representing different generations of the system decrease in age to the southwest where the modern pee dee river merges with several coastal plain tributaries at winyah bay the southern terminus of long bay positions of the successive generational groups record a regional southwestward migration of the river system that may have initiated during the late pliocene the migration was primarily driven by barrier island deposition resulting from the interaction of fluvial and shoreline processes during eustatic highstands structurally driven subsurface paleotopography associated with the mid carolina platform high has also indirectly assisted in forcing this migration these results provide a better understanding of the evolution of the region and help explain the lack of mobile sediment on the long bay inner shelf migration of the river system caused a profound change in sediment supply during the late pleistocene the abundant fluvial source that once fed sand rich barrier islands was cut off and replaced with a limited source supplied by erosion and reworking of former coastal deposits exposed at the shore and on the inner shelf

late quaternary glacial chronology on nevado illimani bolivia and the implications for paleoclimatic reconstructions across the andes 10be terrestrial cosmogenic nuclide surface exposure ages from moraines on nevado illimani cordillera real bolivia suggest that glaciers retreated from moraines during the periods 15 5 13 0 ka 10 0 8 5 ka and 3 5 2 0 ka late glacial moraines at illimani are associated with an ela depression of 400 600 m which is consistent with other local reconstructions of late glacial elas in the eastern cordillera of the central andes a comparison of late glacial elas between the eastern cordillera and western cordillera indicates a marked change toward flattening of the east to west regional ela gradient this flattening is consistent with increased precipitation from the pacific during the late glacial period

palynology of cushion bogs of the cordillera pelada province of valdivia chile abstract fossil pollen identified in the earliest sediments of three cushion bogs in the cordillera pelada 40 10 s 73 30 w dated 10 425 14 c yr b p includes the subantarctic species dacrydium fonckii tetroncium magellanicum astelia pumila gaimardia australis donatia fascicularis and drosera uniflora all grow today in the cordillera pelada and range poleward to the southernmost province of magallanes one species drapetes muscosa included with the pollen of these plants in the earliest record is no longer a constituent of the flora but is limited only to subantarctic chile available evidence indicates that plants survived the last glaciation north of the glacial border with the course of postglacial migration southward following the wastage of the glacier complex holocene climatic and vegetational changes in the cordillera pelada are interpreted in the context of regional reconstructions which show maximum warmth about 9000 yr ago with a pronounced dry period lasting from 9000 to 6500 yr b p maximum precipitation was later reached around 4000 yr ago but has decreased overall since then the regional decline of the endemic gymnosperm fitzroya cupressoides which today is extensively destroyed in the cordillera pelada follows this decrease in precipitation these climatic data suggest a net south ward shift in the zone of westerly winds that bring rainfall to the region over the past 4000 yr

inhomogeneous precipitation distribution and snow transport in steep terrain 1 the inhomogeneous snow distribution found in alpine terrain is the result of wind and precipitation interacting with the snow surface over topography we introduce and explain preferential deposition of precipitation as the deposition process without erosion of previously deposited snow and thus in absence of saltation a numerical model is developed describing the relevant processes of saltation suspension and preferential deposition the model uses high resolution wind fields calculated with a meteorological model arps the model is used to simulate a 120 h snow storm period over a steep alpine ridge for which snow distribution measurements are available the comparison to measurements shows that the model captures the larger scale snow distribution patterns and predicts the total additional lee slope loading well however the spatial resolution of 25 m is still insufficient to capture the smaller scale deposition features observed the model suggests that the snow distribution on the ridge scale is primarily caused by preferential deposition and that this result is not sensitive to model parameters such as turbulent diffusivity drift threshold or concentration in the saltation layer

a preliminary sediment budget for the winyah bay estuary south carolina usa abstract winyah bay a 65 km2 coastal plain estuary in south carolina has an average freshwater input of 557 m3 s 1 and presently receives 0 43 106 t yr 1 of suspended sediments from its watershed corresponding to a yield of 12 7 t km 2 yr 1 however 20 dams have been constructed on the upper rivers primarily on the yadkin and pee dee rivers which serve to capture an additional 0 40 106 t yr 1 of sediment implying a gross sediment yield of 24 5 t km2 yr 1 for the watershed although almost 50 never reaches the coast continuous dredging in the estuarine channels removes 0 107 106 t yr 1 of silt and clay from the estuary sediment coring and 210 pb analysis indicate that the sedimentation rate in mud bay a high accretion area in the lower estuary is 5 5 mm yr 1 which together with previous estimates of marsh sedimentation rates of 2 7 mm yr 1 in the tidal marshes surrounding the estuary leads to a total estuarine mud sedimentation estimate of 0 24 106 t yr 1 thus 80 of the fine grained sediment reaching winyah bay is either accumulating in adjacent marshes or on estuarine mud flats or is being dredged and deposited offshore although these budget calculations need further confirmation by direct measurements and additional coring winyah bay apparently delivers only a minimal amount of suspended fine grained sediments to the coastal ocean

asynchronous maximum advances of mountain and continental glaciers the last maximum glacier advance in many mountain ranges appears to have predated the last maximum advance of the wisconsinan continental ice sheets 20 000 years b p published evidence from widely spaced localities in north and south america europe asia and hawai i suggests that some mountain glaciers extended farther during one or more stades early in the last glaciation roughly 115 000 30 000 years b p than at its end when low global temperature and high precipitation presumably were most favorable for the growth of glaciers variations in the timing of glacier advances in different mountain ranges suggest that alpine glaciers are dependent on regional climate as well as global conditions their study might provide sensitive tests for theories of global climate change glacial deposits are often used as time markers in neotectonic and geomorphic studies and their ages sometimes are inferred from distant measurements or from proxy histories of global climate change undated geomorphic features such as moraines sharply incised streams and river terraces which commonly have been associated with the last maximum glacier advance 20 000 years b p or last deglaciation 13 000 years b p may actually be older by a factor of 2 to 4 or more conversely deposits assigned to the maximum advances of the penultimate global glaciation 130 000 years b p may actually date from early in the most recent glacial cycle and be younger by a comparable factor rates of faulting or folding estimated from displacements or deformation and the assumed ages of such geomorphic features might be too great or too small by corresponding factors

temperature and precipitation record in southern chile extended to 43 000 yr ago southern chile 41 56 s in the belt of westerly winds receives mostly heavy precipitation reaching 8 500 mm yr 1 near 50 s and decreasing northwards and southwards from this latitude to 1 500 mm mean january summer temperatures near sea level along the latitudinal gradient are 8 16 c refs 1 2 dense rain forest covers much of the region to 48 s south to cape horn magellanic moorland prevails and rain forest becomes limited modern pollen measured in surface samples reflects the distribution of plant species in the vegetation we have now applied regression equations relating present day pollen to temperature and precipitation to fossil pollen data at taiquemo to assess climatic conditions during the quaternary the results extend our previous record of the past 16 000 yr at alerce3 beyond the lateglacial to 43 000 yr bp for the 27 000 yr interval they show mean january temperatures of 10 12 c and mean annual precipitation centred around 1 000 mm except during the time span of 31 000 43 000 yr bp when amounts increased to 4 000 mm in general fluctuations correspond to the isotopic climatic reconstruction in antarctica4 and to changes inferred from pollen data at comparable latitudes in tasmania5 8 and new zealand9 10

bajada de rahue province of neuquen argentina an interstadial deposit in northern patagonia abstract pollen and diatom analyses of a radiocarbon dated lacustrine section in the temperate andean region of argentina rahue province neuquen suggest interglacial type climatic conditions between 27 000 and 33 000 yr b p with environments that resemble the modern conditions at the locality this finding correlates with a woodland record from central chile interpreted as reflecting conditions substantially warmer and drier prior to 27 000 yr b p than during the following full glacial period it also appears to relate to the global paleoclimatic scheme derived from deep sea records suggesting interhemispheric synchroneity of such broad scale palaeoclimatic phases

deglacial and postglacial climate history in east central isla grande de chiloe southern chile 43 s abstract palynologic and stratigraphic data from laguna tahui 42 50 s 73 30 w indicate cool temperate and humid conditions there between 14 000 and 10 000 14c yr b p followed by warmer and drier than present conditions between 10 000 and 7000 14c yr b p and subsequent cooling and rise in precipitation over the last 5800 14c yr the thermophilous valdivian trees eucryphia cordifolia and caldcluvia paniculata reached their maximum abundance during the early holocene warm dry phase 10 000 7000 14c yr b p followed by a rise in lake levels and reexpansion of north patagonian conifers starting at 7000 and 5800 14c yr b p respectively variations in the stratigraphic and geographic distribution of temperate rainforests in southern chile suggest multimillennial trends in temperature and westerly activity which are spatially and temporally coherent with paleoclimate records from neighboring regions climate variability at millennial and submillennial time scales may account for the establishment and persistence of fine scale mosaics of valdivian and north patagonian rainforest species in low to mid elevation communities since 5800 14c yr b p

suspended sediment variability on seasonal and tidal time scales in the winyah bay estuary south carolina usa a transient estuarine turbidity maximum etm was observed in winyah bay during field sampling in 1996 the core of this turbidity maximum migrated 8 km seaward of its traditional location at the saltefreshwater interface in response to very high river discharge events in 1996 in response to the semidiurnal tidal cycle there was a well defined variation in the suspended sediment concentration within the turbidity maximum zone between ebb and flood tides as a result of differences in tidal velocities the suspended sediment inventory in the water column during the flood tide was greater than suspended sediment inventory during the ebb tide during slack water the water column was characterized by 0 03 kg m 3 sediment concentrations whereas at times of maximum boundary shear stress near the bottom the water column was highly turbid indicating that bottom sediments were resuspended by the strong tidal currents typical of the bay throughout a tidal cycle the vertical extension of high suspended sediment concentration in the water column within the etm was well developed during the flood tide and inhibited during the ebb tide internal tidal asymmetry with well mixed conditions during the flood tide near the bottom and with stratification in the water column during the ebb tide was probably the process responsible for the enhancement of turbulence during the flood tide and inhibition of turbulence during the ebb tide with implications for the etm 2003 elsevier ltd all rights reserved

analysis of fluvial suspended sediment load contribution through anthropocene history to the south atlantic bight coastal zone u s a abstract discerning the effects of anthropogenic activities i e reservoir construction land use change as opposed to those of natural processes i e climate variability on suspended sediment flux has become an increasingly difficult challenge this contribution presents water and suspended sediment flux from five major watersheds that discharge into the southeastern u s atlantic a region that is currently considered sediment starved three periods of anthropocene time were defined and evaluated 1 pre european conditions 1680 1700 2 pre dam conditions 1905 1925 and 3 post dam conditions 1985 2005 physical and hydrologic watershed data were used to run a climate driven hydrological transport numerical model hydrotrend to estimate suspended sediment flux for each period results indicate that the suspended sediment contribution to the south atlantic bight coastal zone increased by up to 145 as a result of accelerated soil erosion conditions caused by the arrival of europe

detecting the intertidal morphologic change using satellite data abstract the objectives of this study were a to generate an intertidal digital elevation model dem using waterlines extracted from landsat tm and in situ ground levelling data b to quantitatively estimate morphologic change from the generated dems for the years 1991 and 2000 and c to evaluate the chenier migration in the tidal flats of gomso bay korea on extracting the waterlines we considered the tidal flat environments such as tidal conditions remnant surface water suspended sediment and exposure time ground levelling was carried out along one line in 1991 and two lines in 2000 from the extracted waterlines and ground levelling data we succeeded in generating intertidal dems with an accuracy of 10 9 cm r m s overall and 7 3 cm r m s in the lower tidal flats the morphologic changes estimated by subtracting the two dems showed an erosion rate of 9 0 cm over 9 yr that corresponds to an annual mean morphologic change budget of 309 865 m 3 yr overall the gomso tidal flats can be defined as an erosion dominant environment the changes with respect to the sedimentary facies were also evaluated as a the sandy silt flat had a sedimentation rate of 3 4 cm over 9 yr that corresponds to an annual mean budget of 52 552 m 3 yr b the silty sand flat had a sedimentation rate of 14 3 cm over 9 yr that corresponds to a mean erosion of 197 927 m 3 yr and c the sand flat had a sedimentation rate of 11 8 cm over 9 yr that corresponds to a mean change of 58 808 m 3 yr the results comply with the general rules of sedimentology we also investigated the chenier migration which is the most dynamic geomorphologic change in the tidal flats chenier is usually composed by sand and shell as a result of coastal progradation in sand and it is dominantly fed by sediments transported by long shore currents the chenier was found to have migrated about 148 m landward over 6 yr the results demonstrate that satellite remote sensing is an efficient and effective tool for a long term morphologic change estimation in tidal flats

shoreline erosion and decadal sediment accumulation in the tar pamlico estuary north carolina usa a source to sink analysis abstract estuaries contain vital habitats and it is important to understand how these areas respond to human activities and natural processes such as sea level rise and wave attack as estuarine shorelines erode or become modified with hard structures there is potential for significantly altering the availability of sediment and the filling of coastal systems this study used a source to sink approach and quantified rates of shoreline erosion in the tar pamlico sub estuary a tributary of the larger albemarle pamlico estuarine system apes the average shoreline change rate scr determined using an end point method was 0 5 0 9 m yr 1 for the tar pamlico incorporating bulk density estimates this contributes 0 6 105 tons of fine sediment to the system annually or after accounting for fluvial input about 40 of the total sediment supply to the sub estuary the role of the tar pamlico as a sink for these sediments was addressed using the radionuclide tracers 210pb and 137cs radionuclide activities and sediment accumulation rates identified several depositional regions in particular in the middle of the estuary linear sediment accumulation rates ranged from 0 10 0 02 to 0 38 0 02 g cm 2 yr 1 and total storage of fine sediment in the system was 1 6 105 t yr 1 it was not possible to confidently discern a change in the rate of shoreline erosion or seabed accumulation a preliminary budget for fine sediments grain size

snow avalanche formation 1 snow avalanches are a major natural hazard endangering human life and infrastructure in mountainous areas throughout the world in many countries with seasonally snow covered mountains avalanche forecasting services reliably warn the public by issuing occurrence probabilities for a certain region however at present a single avalanche event cannot be predicted in time and space much about the release process remains unknown mainly because of the highly variable layered character of the snowpack a highly porous material that exists close to its melting point the complex interaction between terrain snowpack and meteorological conditions leading to avalanche release is commonly described as avalanche formation it is relevant to hazard mapping and essential to short term forecasting which involves weighting many contributory factors alternatively the release process can be studied and modeled this approach relies heavily on snow mechanics and snow properties including texture while the effect of meteorological conditions or changes on the deformational behavior of snow is known in qualitative or semiquantitative manner the knowledge of the quantitative relation between snow texture and mechanical properties is limited but promising developments are under way fracture mechanical models have been applied to explain the fracture propagation and micromechanical models including the two competing processes damage and sintering have been applied to explain snow failure there are knowledge gaps between the sequence of processes that lead to the release of the snow slab snow deformation and failure damage accumulation fracture initiation and fracture propagation simultaneously the spatial variability that affects damage fracture initiation and fracture propagation has to be considered this review focuses on dry snow slab avalanches and shows that dealing with a highly porous media close to its melting point and processes covering several orders of scale from the size of a bond between snow grains to the size of a mountain slope will continue to be very challenging

seabed dynamics of the inner amazon continental shelf temporal and spatial variability of surficial strata the continental shelf southeast and northwest of the amazon river mouth is overlain by a sediment layer of about a meter in thickness characterized by 210pb profiles consisting of one or more segments with nearly uniform excess activity uniform 210pb activity profiles in shelf environments commonly are a result of intense biological reworking of sediments however biological activity is minimal in this area hence this surficial layer sl is a result either of physical reworking of the sediments or of rapid possibly episodic deposition of sediment factors controlling the formation of the sl were examined during the amasseds project between august 1989 and october 1991 primarily using 210pb t1 2 22 3 yr activity profiles and x radiography the thickness and character of the sl were assessed at four locations reoccupied during four seasonal periods corresponding to various riverine and oceanographic conditions e g discharge stage wind stress one of these stations was reoccupied during semidiurnal and fortnightly periods additionally replicate sediment cores were obtained at stations in order to assess small scale spatial variability of geochemical and sedimentological characteristics in the seabed the sl thicknesses in replicate sediment cores obtained at each site were found to vary within 5 cm normalized thickness of the sl decreased by an average of 17 cm between august 1989 and february 1990 a period of increasing wind stress during falling to rising river discharge the sl thickness subsequently increased slightly 8 cm from february to may 1990 and increased again 27 cm between may 1990 and october 1991 the maximum sl thicknesses were observed in october a period of low wind stress and minimal river input suggesting that the observed seasonal changes are dictated by oceanographic conditions as well as by sediment discharge variations in sl thickness are reflected by changes in suspended sediment mostly as fluid muds as the highest suspended sediment inventories and most extensive fluid muds are observed during the period when sl thickness is at a minimum although a significant sl was present during all of the sampling periods changes in the character of 210pb profiles at two of the stations suggest that substantial perhaps complete removal and redeposition of the sl occurred some time between february and may preserved strata i e below the sl is characterized by greater evidence of bioturbation and increased sand content but otherwise is similar to that of the sl long term preservation of strata is thought to occur through episodic suspension and redeposition of the sl with net accumulation of decimeter thick hiatus bounded layers

climate fire and vegetation between about 13 000 and 9200 14c yr b p in the chilean lake district abstract a pollen record from lago condorito 41 45 s 73 07 w shows that north patagonian rain forest taxa predominated between about 13 000 and 12 200 14c yr b p in the lowlands of southern chile near the city of puerto montt this was followed by the expansion and persistence of the conifer podocarpus nubigena between 12 200 and 9900 14c yr b p trees favored by disturbance expanded between 11 200 and 9900 14c yr b p concurrent with sharp and sustained increases of microscopic charcoal particles taxa of low elevation rain forests expanded and became more diverse in pulses centered at 9900 and 9000 14c yr b p following the disappearance of p nubigena these data suggest conditions approaching modern climate between about 13 000 and 12 200 14c yr b p the climate cooled between 12 200 and 9900 14c yr b p then quickly warmed to interglacial conditions stand replacing fires occurred near lago condorito between 11 200 and 9900 14c yr b p under cool temperate humid conditions the proximity and reported antiquity of the monte verde archeological site raise the possibility that these fires were set by human activities

expansion of magellanic moorland during the late pleistocene palynological evidence from northern isla de chiloe chile the late quaternary vegetation of northern isla de chiloe is inferred from palynological analysis of a section in the rio negro drainage 42 03 s 73 50 w at ca 30 500 yr b p maxima of astelia and donatia occurred suggesting wetland development from that time until ca 27 000 yr b p steppe indicators such as compositae gramineae dominated suggesting drier conditions after 27 000 yr b p the moorland shrub dacrydium gradually increased reaching a maximum by 18 000 yr b p at this time astelia increased again suggesting development of cushion bog during cold and wet conditions the glacial postglacial transition is characterized by a marked change from peaty sediments to clays a decrease in the cushion bog flora and the prevalence of gramineae compositae and swamp taxa this vegetation prevailed until ca 7000 yr b p when forest taxa became dominant the floristic pattern inferred from the pollen spectra of the rio negro section suggests that the late pleistocene vegetation of chiloe resembled modern magellanic moorland vegetation 52 56 lat s based on climatic conditions presently associated with magellanic moorland its occurrence in chiloe at low elevations during the late pleistocene implies a decrease in average temperature of at least 4 c and an increase in annual precipitation of at least 1500 mm

snow particle characteristics in the saltation layer shadowgraphy was employed to study snow saltation in boundary layer wind tunnel experiments with fresh naturally deposited snow the shadowgraphy method allowed for a temporally and spatially high resolution investigation of snow particle characteristics within a measurement area of up to 50 mm x 50 mm snow particle size and number characteristics and their variation with height in the saltation layer were analysed the following observations and findings were made for the saltation layer 1 the particle number decreases exponentially with height 2 the mean particle diameter is fairly constant with a very slight tendency to decrease with height 3 the maximum particle diameter decreases linearly with height and 4 the snow particle size distribution can be adequately described by gamma probability density functions the shape and scale parameters of the gamma distribution were found to vary systematically though only slightly with height over ground and between experiments with different snowpack characteristics

sources and distribution of organic matter in a river dominated estuary winyah bay sc usa abstract the sources and distribution of organic matter om in surface waters and sediments from winyah bay south carolina usa were investigated using a variety of analytical techniques including elemental stable isotope and organic biomarker analyses several locations along the estuary salinity gradient were sampled during four different periods of contrasting river discharge and tidal range the dissolved organic carbon doc concentrations of surface waters ranged from 7 mg l 1 in the lower bay stations closest to the ocean to 20 mg l 1 in the river and upper bay samples there was a general linear relationship between doc concentrations and salinity in three of the four sampling periods in contrast particulate organic carbon poc concentrations were significantly lower 0 1 3 mg l 1 and showed no relationship with salinity the high molecular weight dissolved om hmw dom isolated from selected water samples collected along the bay displayed atomic carbon nitrogen ratios c n a and stable carbon isotopic compositions of organic carbon 13coc that ranged from 10 to 30 and from 28 to 25 respectively combined such compositions indicate that in most hmw dom samples the majority of the om originates from terrigenous sources with smaller contributions from riverine and estuarine phytoplankton in contrast the c n a ratios of particulate om pom samples varied significantly among the collection periods ranging from low values of 5 to high values of 20 overall the trends in c n a ratios indicated that algal sources of pom were most important during the early and late summer whereas terrigenous sources dominated in the winter and early spring in winyah bay bottom sediments the concentrations of the mineral associated om were positively correlated with sediment surface area the c n a ratios and 13coc compositions of the bulk sedimentary om ranged from 5 to 45 and from 28 to 23 respectively these compositions were consistent with predominant contributions of terrigenous sources and lesser but significant inputs of freshwater estuarine and marine phytoplankton the highest terrigenous contents were found in sediments from the river and upper bay sites with smaller contributions to the lower parts of the estuary the yields of lignin derived cuo oxidation products from winyah bay sediments indicated that the terrigenous om in these samples was composed of variable mixtures of relatively fresh vascular plant detritus and moderately altered soil om based on the lignin phenol compositions most of this material appeared to be derived from angiosperm and gymnosperm vascular plant sources similar to those found in the upland coastal forests in this region a few samples displayed lignin compositions that suggested a more significant contribution from marsh c3 grasses however there was no evidence of inputs of spartina alterniflora a c4 grass remains from the salt marshes that surround the lower sections of winyah bay