volcano sedimentary processes operating on a marginal continental arc the archean raquette lake formation slave province canada abstract the 200 m thick volcano sedimentary raquette lake formation located in the south central archean slave province represents a remnant arc segment floored by continental crust the formation overlies the gneissic sleepy dragon complex unconformably is laterally interstratified with subaqueous mafic basalts of the cameron river volcanic belt and is considered the proximal equivalent of the turbidite dominated burwash formation a continuum of events associated with volcanism and sedimentation and controlled by extensional tectonics is advocated a complex stratigraphy with three volcanic and three sedimentary lithofacies constitute the volcano sedimentary succession the volcanic lithofacies include 1 a mafic volcanic lithofacies composed of subaqueous pillow pillow breccia and subaerial massive to blocky flows 2 a felsic volcanic lithofacies representing felsic flows that were deposited in a subaerial environment and 3 a felsic volcanic sandstone lithofacies interpreted as shallow water wave and storm reworked pyroclastic debris derived from explosive eruptions the sedimentary lithofacies are represented by 1 a conglomerate sandstone lithofacies consistent with unconfined debris flow hyperconcentrated flood flow and talus scree deposits as well as minor high energy stream flow conglomerates that formed coalescing steep sloped coarse clastic fan deltas 2 a sandstone lithofacies interpreted as hyperconcentrated flood flow deposits that accumulated at the subaerial subaqueous interface and 3 a mudstone lithofacies consistent with suspension sedimentation in a small restricted lagoon type setting the raquette lake formation is interpreted as a fringing continental arc that displays both high energy clastic sedimentation and contemporaneous effusive and explosive mafic and felsic volcanism modern analogues that develop along active plate margins in which continental crust plays a significant role include japan and the baja california peninsula

global ice sheet system interlocked by sea level abstract denton and hughes 1983 quaternary research 20 125 144 postulated that sea level linked a global ice sheet system with both terrestrial and grounded marine components during late quaternary ice ages summer temperature changes near northern hemisphere melting margins initiated sea level fluctuations that controlled marine components in both polar hemispheres it was further proposed that variations of this ice sheet system amplified and transmitted milankovitch summer half year insolation changes between 45 and 75 n into global climatic changes new tests of this hypothesis implicate sea level as a major control of the areal extent of grounded portions of the antarctic ice sheet thus fitting the concept of a globally interlocked ice sheet system but recent atmospheric modeling results manabe and broccoli 1985 journal of geophysical research 90 2167 2190 suggest that factors other than areal changes of the grounded antarctic ice sheet strongly influenced southern hemisphere climate and terminated the last ice age simultaneously in both polar hemispheres atmospheric carbon dioxide linked to high latitude oceans is the most likely candidate shackleton and pisias 1985 atmospheric carbon dioxide orbital forcing and climate in the carbon cycle and atmospheric co2 natural variations archean to present e t sundquest and w s broecker eds pp 303 318 geophysical monograph 32 american geophysical union washington d c but another potential influence was high frequency climatic oscillations 2500 yr it is postulated that variations in atmospheric carbon dioxide acted through an antarctic ice shelf linked to the grounded ice sheet to produce and terminate southern hemisphere ice age climate it is further postulated that milankovitch summer insolation combined with a warm high frequency oscillation caused marked recession of northern hemisphere ice sheet melting margins and the north atlantic polar front about 14 000 14c yr b p this permitted renewed formation of north atlantic deep water which could well have controlled atmospheric carbon dioxide w s broecker d m peteet and d rind 1985 nature london 315 21 26 combined melting and consequent sea level rise from the three warming factors initiated irreversible collapse of the interlocked global ice sheet system which was at its largest but most vulnerable configuration

glacier variations in breheimen southern norway relative age dating of holocene moraine complexes at six high altitude glaciers lichenometric evidence and schmidt hammer r values are used to date holocene moraine sequences in front of six high altitude 1500 m glaciers in breheimen central southern norway at three glacier forelands with southerly aspects hogsetbreen vestre hoybre and ostre hoybre relatively small 4 m high discrete boulder moraine ridges are shown to date from the little ice age the remaining three glaciers ostre tundradalskyrkjabre nordre tundradalskyrkjabre and hestdalshogdibreen with northerly or easterly aspects and large multiridged rampart like moraine complexes 15 30m thought to be ice cored and of the push deformation type lie above the local altitudinal limit of permafrost negatively skewed r value distributions from these moraine complexes provide critical evidence for pre little ice age glacier expansion as they indicate the survival of long weathered boulders on moraine surfaces where late lying snow may reduce or prevent lichen growth formation of the moraine complexes ap

glacier variations in breheimen southern norway dating little ice age moraine sequences at seven low altitude glaciers moraine sequences in front of seven relatively low altitude glaciers in the breheimen region of central southern norway are described and dated using a multi proxy approach to moraine stratigraphy lichenometric dating based on the rhizocarpon subgenus is used to construct a composite moraine chronology which indicates eight phases of synchronous moraine formation ad 1793 1799 1807 1813 1845 1852 1859 1862 1879 1885 1897 1898 1906 1908 and 1931 1933 although the existence of a few cases of older moraines possibly dating from earlier in the eighteenth or late in the seventeenth centuries cannot be ruled out by lichenometry schmidt hammer r values from boulders on outermost moraine ridges suggest an absence of holocene moraines older than the little ice age twenty three radiocarbon dates from buried soils and peat associated with outermost moraines at three glaciers tverreggibreen storegrovbreen and greinbreen also indicate that the little ice age glacier maximum was the neoglacial maximum at most if not all glaciers several maximum age estimates for the little ice age glacier maximum range between the fifteenth and seventeenth centuries with the youngest from a buried soil being ad 1693 a pre little ice age maximum cannot be ruled out at greinbreen however where the age of buried peat suggests the outermost moraine dates from ad 981 1399 at variance with the lichenometric evidence glaciofluvial stratigraphy at tverreggibreen provides evidence for minor glacier advances about ad 655 963 and ad 1277 1396 respectively copyright 2003 john wiley sons ltd

milankovitch forcing of fluctuations in the level of tropical lakes from 18 to 0 kyr bp an atmospheric general circulation model has been used to simulate the climates of january and july at 3 000 yr intervals from 15 kyr bp onwards the model simulates a strengthened monsoon circulation and increased precipitation in the northern hemisphere tropics culminating at 9 6 kyr bp the computed hydrological budgets were used to estimate the area of closed lakes between 8 9 and 26 6 n giving with minor exceptions results in good agreement with geological evidence

on the estimation of radar polarization orientation shifts induced by terrain slopes in recent studies d l schuler et al 2000 applied polarimetric imaging radar derived orientation angles to measure topography and j s lee et al 2000 used orientation angles for polarimetric sar data compensation to ensure accurate estimation of geophysical parameters in rugged terrain areas to support these applications it is important to accurately estimate shifts in orientation angles induced by the azimuth slope variations however in many cases inconsistency in the estimation of orientation angle shifts was encountered in several areas introducing noisy and erroneous results the present authors develop a unified analysis of estimation algorithms based on the circular polarization covariance matrix the concept of reflection symmetry is used to explain the soundness of the circular polarization method and to show problems associated with other algorithms l band polarimetric synthetic aperture radar sar images of camp roberts ca are used to substantiate this theory

holocene glacier variability and neoglacial hydroclimate at alfotbreen western norway abstract glaciers and small ice caps respond rapidly to climate perturbations mainly winter precipitation and summer temperature and the mass balance of glaciers located in western norway is governed mainly by winter precipitation pw records of past pw can offer important insight into long term changes in atmospheric circulation but few proxies are able to accurately capture winter climate variations in scandinavia reconstructions of equilibrium line altitude ela variations from glaciers that are sensitive to changes in pw therefore provide a unique opportunity to quantify past winter climate in this region here we present a new holocene glacier activity reconstruction for the maritime ice cap alfotbreen in western norway based on investigations of distal glacier fed lake sediments and modern mass balance measurements 1963 2010 several lake sediment cores have been subject to a suite of laboratory analyses including measurements of physical parameters such as dry bulk density dbd and loss on ignition loi geochemistry xrf surface magnetic susceptibility ms and grain size distribution to identify glacial sedimentation in the lake both radiocarbon ams 14 c and 210 pb dating were applied to establish age depth relationships in the sediment cores a novel approach was used to calibrate the sedimentary record against a simple ela model which allowed reconstruction of continuous ela changes for alfotbreen during the neoglacial when alfotbreen was present i e the last 1400 years furthermore the resulting ela variations were combined with an independent summer temperature record to calculate neoglacial pw using the liestol equation the resulting pw record is of higher resolution than previous reconstructions from glaciers in norway and shows the potential of glacier records to provide high resolution data reflecting past variations in hydroclimate complete deglaciation of the alfotbreen occurred 9700 cal yr bp and the ice cap was subsequently absent or very small until a short lived glacier event is seen in the lake sediments 8200 cal yr bp the ice cap was most likely completely melted until a new glacier event occurred around 5300 cal yr bp coeval with the onset of the neoglacial at several other glaciers in southwestern norway alfotbreen was thereafter absent or very small until the onset of the neoglacial period 1400 cal yr bp the little ice age lia 650 50 cal yr bp was the largest glacier advance of alfotbreen since deglaciation with a maximum extent at 400 200 cal yr bp when the ela was lowered approximately 200 m relative to today the late onset of the neoglacial at alfotbreen is suggested to be a result of its low altitude relative to the regional ela a synthesis of neoglacial ela fluctuations along the coast of norway indicates a time transgressive trend in the maximum extent of the lia which apparently seems to have occurred progressively later as we move northwards we suggest that this trend is likely due to regional winter precipitation differences along the coast of norway

holocene glacier activity at the southwestern part of hardangerjokulen central southern norway evidence from lacustrine sediments lacustrine sediments from lake isdalsvatn downstream from the southwestern margin of the plateau glacier hardangerjokulen central southern norway show that the lake received glacial meltwater until 7890 95 bp a thin bluish grey minerogenic silt layer probably reflects a short glacial re advance between 7005 90 and 6835 150bp after the latter date inflow of glacial meltwater ceased indicating that small or more probably no glaciers existed on the southwestern hard angerjokulen plateau a drop in organic content and a slight increase in detrital content inferred from magnetic susceptibility at 120cm depth in the core may indicate some glacier activity in the catchment from about 3400 bp textural changes at 50cm depth indicate increased neoglacial activity in the upper catchment area from 2265 80 bp differences in glacier chronologies between the southern and northern sectors of hardangerjokulen may be explained partly by different glacier responses to the precipitation and wind distribu

shallow water eruption fed mafic pyroclastic deposits along a paleoproterozoic coastline kangerluluk volcano sedimentary sequence southeast greenland abstract the 200 300 m thick volcano sedimentary sequence at kangerluluk is part of the psammite zone one of four major zones which constitute the 1 8 ga ketilidian orogen in south greenland three lithofacies are emphasized in the study 1 the conglomerate sandstone 2 the volcanic and 3 the pyroclastic lithofacies the 2 40 m thick conglomerate sandstone lithofacies represents a subaerial to subaqueous fan delta deposit matrix and clast supported conglomerates are interpreted as debris flow and longitudinal gravel bar deposits erosive based conglomerate channel fills attest to stream incision trough crossbedded sandstone interpreted as lunate megaripples planar bedded sandstone indicative of upper flow regime bar top sands and small scale trough crossbeds reflecting ripples follow up section form collectively with the conglomerate 0 40 2 50 m thick fining upward sequences the sandstone dominated unit up section from the conglomerates and composed of planar and low angle crossbeds minor ripples and graded beds as well as mudstone is indicative of a lower shoreface deposit below normal wave base the clastic sedimentary rocks are suggestive of a fan delta setting the 100 200 m thick volcanic lithofacies composed of pillowed and pillow brecciated lava flows is consistent with shallow water deposition interstratification of lava flows with both conglomerate sandstone and pyroclastic lithofacies intrusion of dykes into volcaniclastic rocks and peperite formation accentuate contemporaneity between volcanism and sedimentation and is a common feature of island arcs the 1 50 m thick pyroclastic lithofacies with sharp depositional contacts to the overlying volcanic and underlying conglomerate sandstone lithofacies was emplaced in a subaqueous setting the lithofacies is divided into a planar to crossbedded tuff lapilli tuff and a bedded lapilli tuff breccia whereby both deposits are inferred to result from shallow water surtseyan type eruptions the 5 15 m thick bedded lapilli tuff breccia with abundant bomb sag structures and graded beds is considered a result of subaqueous eruptions strong enough to form an insulating steam cupola characterized by ballistically emplaced bombs that rapidly collapsed allowing for transport via mass flow processes the deposits are considered proximal to the vent the 2 50 cm thick planar to crossbedded tuff lapilli tuff featuring abundant euhedral and broken crystals of feldspar 2cm and minor pyroxene 1 cm are massive graded crossbedded and stratified the planar but laterally discontinuous beds characterized by abundant low angle scours are interpreted as low to high concentration sediment gravity flows produced directly from subaqueous tephra jets that collapsed due to massive water ingestion local breccia size pyroclasts disrupting beds are interpreted as bomb sags the mafic eruption fed surtseyan type deposits postulated to be a subaqueous counterpart of cold subaerial base surges originate from subaqueous tuff cones formed along a rugged volcanic dominated shoreline featuring high energy fan deltas

little ice age precipitation in jotunheimen southern norway recently published glaciological data from southern norway enable analysis of changes in glacier geometry since the little ice age lia and estimation of the magnitude of the lia precipitation anomaly glacier area extents in the jotunheimen region have been created for 2003 using glacier outlines derived from landsat and for the lia maximum about ad 1750 by using glacier outlines defined by moraines a 25 m digital terrain model from 1980 was used to derive inventory data for both times both inventories provide area and altitude range as well as length slope and aspect of the glaciers area altitude profiles a z for the lia maximum are calculated from the 1980 profiles by assuming that the area increase distribution a z was concentrated at low altitude and it integrates to the measured area difference between 1980 and the lia under this assumption the regionally averaged mean altitude change from 1980 to the lia z 68 m glacier mass balance measurements show that the mass balance gradie

loess paleosol stratigraphy of dukso area namyangju city korea south abstract as korea lies between china with a drier climate and the wetter japanese islands the korean loess paleosol stratigraphy constitutes an important record of variations in the east asian monsoon climate the loess paleosol sequence consists of three loess layers l1ll1 l1ll2 and l2 and three paleosols l1ss1 s1 and s2 in the study area l1ll1 accumulated near the surface and is only about 5 cm in outcrop because it was removed for farming l1ss1 is about 103 cm thick soil crack structures developed in the upper part of l1ss1 were formed by shrinkage or as seasonally frozen ground soil wedges during the early cold dry stage of glacial period l2 is 48 cm thick with osl ages of 167 000 and 186 000 yr magnetic susceptibilities of paleosols were higher than the loess layers fine quartz grains in the loess layers are characterized by rounded shape and pitted surfaces based on the presence of the at tephra osl ages soil color soil crack structure magnetic susceptibility and median diameter the loess paleosol sequence of the dukso section can be correlated with the chinese loess paleosol sequence between mis 2 and 7

mid devonian tectonics and sedimentation in the bristol channel area the hangman sandstone group eifelian of north devon contains two continental 9old red sandstone9 formations the trentishoe formation is some 1000 m thick and consists of lithic arenites which petrographically match closely with those in the higher parts of the lower old red sandstone in south wales this formation was derived mainly from erosion of the highest lower old red sandstone in early mid devonian times as a result of end caledonian uplift and erosion in s wales the rawns formation which follows contains 120 m of conglomerates and pebbly sandstones with angular clasts of porphyry tuff quartzite and lithic arenite which do not match with rocks in possible source areas in wales but could have been derived from the lower palaeozoic and precambrian rocks believed to lie at shallow depth to the north of the bristol channel fault zone fault movements along this zone are believed to have generated relatively short lived coarse clastic supply at various times and places around the bristol channel in lower to early mid devonian times in response to end caledonian movements the later production of late namurian to westphalian sands from the bristol channel area was unrelated to these devonian events and represents uplift in response to variscan events in sw england

synergistic measurements of ocean winds and waves from sar in this study we present a synergistic method to retrieve both ocean surface wave and wind fields from spaceborne quad polarization qp synthetic aperture radar sar imaging mode data this algorithm integrates qp sar wind vector retrieval model and the wave retrieval model with consideration to the nonlinear mapping relationship between ocean wave spectra and sar image spectra in order to synergistically retrieve wind fields and wave directional spectra the method does not require a priori information on the sea state it combines the observed vv polarized sar image spectra with the retrieved wind vectors from the vh polarized sar image to estimate the wind generated wave directional spectra the differences between the observed sar spectra and optimal sar image spectra associated with the wind waves are interpreted as the contributions from the swell waves the retrieved ocean wave spectra are used to estimate the integrated spectral wave parameters such as significant wave heights wavelengths wave directions and wave periods the wind and wave parameters retrieved by qp sar are validated against those measured by the national data buoy center ndbc directional wave buoys under different sea states the validation results show that the qp sar sar has potential to simultaneously measure the ocean surface waves and wind fields from space

scandinavian glacial and climatic fluctuations during the holocene abstract historical documents and lichenometric studies give a detailed picture of the little ice age in scandinavia there was a large advance in norway which has been dated at a few places to 1750 small readvances during the retreat occurred around a d 1780 1810 1840 1850 1850 1870 1890 1910 and 1930 in sweden most of these advances have been recognized and in addition extensive advances are dated by lichenometry to around a d 1600 1650 and 1700 1720 soils buried beneath moraines often yield radiocarbon dates that are much too old methods dependent on these must therefore be used with care evidence for pre little ice age advances are often considered equivocal the most reliable information is probably provided by studies of lacustrine sediments combining information from all sources the most significant pre little ice age glacier advances most likely occurred in 7 5 5 1 4 5 3 2 2 8 2 2 1 9 and 1 5 1 1 radiocarbon ka bp advances that were less extensive or for which there is less evidence occurred around 6300 5600 2500 940 600 560 and 380 bp

surface exposure dating of moraines in the kromer valley silvretta mountains austria evidence for glacial response to the 8 2 ka event in the eastern alps 10 be dating of a pronounced glacier advance kromer stadial in the western part of the silvretta mountains western austria yielded ages ranging from 8010 360 to 8690 410 years with a mean age for moraine stabilization of 8410 690 years hence the kromer stadial which was previously considered as early preboreal may represent the glacier response to the early phase of the 8 2 ka event as it is recorded in the greenland ice cores the glacier advanced to a position beyond its little ice age lia limit the end moraines are situated 750 1000 m downvalley from the glacier ends in 1850 the corresponding drop of the equilibrium line altitude relative to the lia datum was 75 m the glacier advance was followed by a period of glacier recession and rock glacier development in total the climatic fluctuation may have lasted for about 500 200 years the age and duration of the climatic fluctuation is in good accordance with the misox cold phase and ce 3 climatic fluctuation as recorded in switzerland climate during the kromer stadial was characterized by more humid conditions than today along the northern fringe of the alps and slightly negative to moderately positive changes in precipitation in the central part of the austrian alps summer temperatures changes were most likely in the order of i to 0k mean annual temperature was 1 5k to 2k lower than today at least during the second phase of the climatic fluctuation

improvement in the estimation of dominate wavenumber and direction from spaceborne sar image spectra when corrected for ocean surface movement because a synthetic aperture radar sar is a doppler device ocean surface movement can degrade a sar ocean image ocean surface movement causes the redistribution of apparent radar cross section in a sar image to neighboring image elements it is demonstrated in this paper that this aspect of sar imaging can be treated as a simple resolution loss in a linear system such an approach explains the falloff in response at high azimuth wavenumbers experienced in sar image spectra more importantly this approach allows for a straightforward method to alleviate the problem of ocean surface motion correction of sar image spectra using a linear systems approach results in sar image spectra in which the locations in wavenumber space of surface wave spectral peaks are more consistent with the estimated location of storm sources than are the locations of peaks from uncorrected spectra

seasat altimeter observations of dynamic topography in the gulf stream region individual seasat altimeter profiles in the western north atlantic have been differenced with the best available geoid model to remove the gravitational component the resulting sea surface height profiles compare remarkably well with independent oceanographic observations the gulf stream is clearly apparent in each profile as a 1 to 2 m step and known positions of cyclonic and anticyclonic rings correspond with depressions and elevations respectively with amplitudes as large as 95 cm some of the most important altimeter data for analyzing the dynamic ocean signal were gathered during the last month of the mission when the same ground track was repeated every 3 days these data allow detailed examination of time varying ocean phenomena since the gravitational component is time invariant one set of collinear passes clearly shows a cyclonic ring as it moves out from underneath the spacecraft s track an event which was simultaneously observed with the aid of a satellite tracked surface buoy another striking feature seen in the altimeter data set is the apparent variability exhibited by the gulf stream on time scales of a few days surface transport indicated by the sea surface height difference across the stream varied by nearly 30 and over the entire 3 month period much larger fluctuations were observed suggesting significant changes in total mass transport altimetry may provide an effective means of determining the time and space scales associated with these variations

pattern and forcing of northern hemisphere glacier variations during the last millennium time series depicting mountain glacier fluctuations in the alps display generally similar patterns over the last two centuries as do chronologies of glacier variations for the same interval from elsewhere in the northern hemisphere episodes of glacier advance consistently are associated with intervals of high average volcanic aerosol production as inferred from acidity variations in a greenland ice core advances occur whenever acidity levels rise sharply from background values to reach concentrations 1 2 equiv h kg above background a phase lag of about 10 15 yr equivalent to reported response lags of alpine glacier termini separates the beginning of acidity increases from the beginning of subsequent ice advances a similar relationship but based on limited and less reliable historical data and on lichenometric ages is found for the preceding 2 centuries calibrated radiocarbon dates related to advances of non calving and non surging glaciers during the earlier part of the little ice age display a comparable consistent pattern an interval of reduced acidity values between about 1090 and 1230 a d correlates with a time of inferred glacier contraction during the medieval optimum the observed close relation between noothern hemisphere glacier fluctuations and variations in greenland ice core acidity suggests that sulfur rich aerosols generated by volcanic eruptions are a primary forcing mechanism of glacier fluctuations and therefore of climate on a decadal scale the amount of surface cooling attributable to individual large eruptions or to episodes of eruptions is simlar to the probable average temperature reduction during culminations of little ice age alacier advances ca 0 5 1 2 c as inferred from depression of equilibrium line altitudes

mapping sea surface oil slicks using radarsat 2 quad polarization sar image 1 polarimetric sar decomposition parameters average alpha angle and entropy h are estimated for oil slick contaminated sea surfaces and slick free conditions using a radarsat 2 quad polarization sar image the values of h and within oil slick areas are significantly higher than those of the ambient sea surface indicating the dominance of bragg scattering for the slick free ocean and non bragg scattering for the oil slick area in land classification the conformity coefficient is often used to discriminate surface scattering with double bounce or volume scattering based on this rationale we also develop a method using as a logical scalar descriptor to map oil slicks under low to moderate wind conditions the proposed method is assessed using a radarsat 2 quad polarization sar image of oil slicks in the gulf of mexico analysis shows that when is positive the sea surface is slick free whereas is negative for oil slick areas this method provides a simple and effective mapping technique for oil slick detection

were abrupt lateglacial and early holocene climatic changes in northwest europe linked to freshwater outbursts to the north atlantic and arctic oceans during the lateglacial and early holocene abrupt millennial scale climatic variations are recorded in a wide range of high resolution proxy records from marine and terrestrial archives in nw europe our review of the evidence for these rapid climate events do not show an apparent link to possible forcing factors such as long term orbitally induced variations in solar radiation short term variations in solar activity as inferred from 14 c atmospheric carbon dioxide concentration or volcanic sulphate as recorded in the gisp2 ice core record there is however a remarkable degree of similarity with the number duration and timing of episodes of increased e ux of fresh water to the north atlantic and arctic oceans from the laurentide ice sheet and from the baltic ice lake in sw sweden these freshwater outburst events occurred when continental runoff from the laurentide ice sheet was rerouted from the mississippi river to the hudson river st lawrence river hudson strait and along the mackenzie river to the atlantic and arctic oceans and when the baltic ice lake in sw sweden drained to skagerrak periods of increased freshwater e ow to the north atlantic and arctic oceans may thus provide a mechanism to explain the abrupt and signie cant lateglacial and early holocene climate events in nw europe the idea that freshwater outbursts might drive abrupt climate events is not new but previous work may have underestimated the extent of support from proxy data and overestimated the ine uence of the laurentide ice sheet

holocene climatic change in the northern midwest pollen derived estimates mapping of holocene pollen data in the midwestern united states has revealed several broadscale vegetational changes that can be interpreted in climatic terms these changes include 1 the early holocene northward movement of the spruce dominated forest and its later southward movement after 3000 yr b p and 2 the eastward movement of the prairie forest border into southwestern wisconsin by 8000 yr b p and its subsequent westward retreat after 6000 yr b p when certain basic assumptions are met multiple regression models can be derived from modern pollen and climate data and used to transform the pollen record of these vegetational changes into quantitative estimates of temperature or precipitation to maximize the reliability of the regression equations we followed a sequence of procedures that minimize violations of the assumptions that underlie regression analysis reconstructions of precipitation during the holocene indicated that from 9000 to 6000 yr b p precipitation decreased by 10 to 25 over much of the midwest while mean july temperature increased by 0 5 to 2 0 c at 6000 yr b p precipitation was less than 80 of its modern values over parts of wisconsin and minnesota after 6000 yr b p precipitation generally increased while mean july temperature decreased in the north and increased in the south the time of the maximum temperature varies within the midwest and is earlier in the north and later in the south

glacier fluctuations equilibrium line altitudes and palaeoclimate in lyngen northern norway during the lateglacial and holocene based on lacustrine and morpho stratigraphical evidence from lyngen in troms northern norway 13 marginal moraines have been mapped in front of lenangsbreene in strupskardet moraines m1 m13 are inferred to represent glacier halts or advance readvance taking place during the lateglacial and holocene the presence of collapse depressions suggests that some of them were ice cored m1 m3 a chronological framework taking into account a combination of former shorelines and related glacier meltwater channels lichenometry and ams radiocarbon dated lacustrine sediments spanning the last 20 000 cal yr bp has been established the distal glacier fed lake aspvatnet was isolated from the sea c 10 300 cal yr bp and the lacustrine sediments have been investigated by use of loss on ignition loi magnetic susceptibility water content wet and dry bulk density dbd and the magnetic parameters anhysteretic remanent magnetization arm and saturation remanent magnetization sirm there is in general good agr

spatial variations of ocean wave directional spectra from the seasat synthetic aperture radar seasat synthetic aperture radar ocean wave spectra for a 900 km pass are analyzed and interpreted in the context of both their probable generation sources and their surface current and bathymetric modifiers systematic vector wavenumber variations of several times the standard error of determination 1 5 in magnitude and 0 9 in direction occur along the entire 900 km pass the large scale spatial variation of a 200 m swell system can be accurately accounted for as a result of dispersion from a distant storm the more local variations are qualitatively well correlated in position with known currents and bathymetry but show systematic biases that appear partly due to an environmentally dependent instrument transfer function in the regions of high current and highest sea state there is also substantial evidence that a large angular deviation in the center of the pass is the result of a mesoscale eddy just to the east

the greenland 8200 cal yr bp event detected in loss on ignition profiles in norwegian lacustrine sediment sequences high resolution loss on ignition analyses of lacustrine sediment cores from both proglacial and non glacial lakes in southern norway have revealed a specific pattern characterised by a significant two peaked reduction of the loss on ignition values in the basal half of the cores in non glacier fed lakes the loss on ignition variations are interpreted to reflect mainly lake productivity and hence variability in surface summer air temperature sediments deposited in proglacial lakes however reflect mainly the glacier activity in the lake catchment bulk ams radiocarbon dates from the core sequences and the loss on ignition curve pattern suggest that this event correlates with the 8200 cal yr bp event recorded in the grip and gisp2 greenland ice cores termed the finse event in southern norway copyright 2001 john wiley sons ltd

14c dating and palaeoenvironment of the historic little ice age glacier advance of nigardsbreen southwest norway moss and grass remains associated with a well developed in situ palaeosol buried beneath a moraine ridge in front of nigardsbreen jostedalsbreen ice cap southern norway have been 14c dated pollen preserved with the plant remains suggests the existence of an agricultural landscape prior to the deposition of the moraine the calibrated dates and the pollen spectra are in close accord with historically documented evidence for the timing and palaeoenvironment of the little ice age advance of the glacier considerable potential is indicated for estimating the maximum ages of moraine ridges and for palaeoenvironmental reconstruction where such documentary evidence does not exist

wind and wave measurements using complex ers 2 sar wave mode data a global dataset of complex synthetic aperture sar images is processed from wave mode raw data acquired by the ers 2 satellite using these data different algorithms for wind and wave measurements recently developed in view of future envisat asar data are analyzed on a statistical basis different aspects of complex sar wave mode processing with the dlr processor bsar are discussed and global statistics of processing parameters are presented single look complex slc imagettes give the opportunity to apply multilook techniques in range as well as in azimuth such methods are used to reduce speckle noise or to analyze the time evolution of the ocean surface cross section during sar integration time a global analysis of different new algorithms for wind and ocean wave measurements taking advantage of slc data is given wind speed is estimated with the azimuthal cross correlation algorithm cca as a modification of the existing cca range multilooking is used to deal with the speckle bias homogeneity of the imagettes is considered wind speed is derived from mean sar image intensities taking into account wind direction cmod algorithm comparison with collocated ers 2 scatterometer data shows reasonable agreement with the cca and good agreement for the cmod approach using imagettes instead of image power spectra allows the authors to study ocean surface features caused by natural slicks sea ice or atmospheric processes the impact of these phenomena on scat measurements is considered cross spectral methods are used to derive the ocean wave propagation direction from complex imagettes on a global basis comparison with model data provided by the european center for medium range weather forecast ecmwf shows good agreement

ocean wave extraction from radarsat synthetic aperture radar inter look image cross spectra this study is concerned with the extraction of directional ocean wave spectra from synthetic aperture radar sar image spectra the statistical estimation problem underlying the wave sar inverse problem is examined in detail in order to properly quantify the wave information content of sar as a concrete focus a data set is considered comprising six radarsat sar images co located with a directional wave buoy off the east coast of canada these sar data are transformed into inter look image cross spectra based on two looks at the same ocean scene separated by 0 4 s the general problem of wave extraction from sar is cast in terms of a statistical estimation problem that includes the observed sar spectra the wave sar transform and prior spectral wave information the central role of the weighting functions inverse of the error covariances is demonstrated as well as the consequence of approximate based on the quasilinear wave sar transform versus exact linearizations on the convergence properties of the algorithm error estimates are derived and discussed this statistical framework is applied to the extraction of spectral wave information from observed radarsat sar image cross spectra a modified wave sar transform is used to account for case specific geophysical and imaging effects analysis of the residual error of simulated and observed sar spectra motivates a canonical form for the sar observation error covariance wave estimates are then extracted from the sar spectra including wavenumber dependent error estimates and explicit identification of spectral null spaces where the sar contains no wave information band limited sar wave information is also combined with prior buoy spectral wave estimates through parameterization of the wave spectral shape and use of regularization

the duparquet formation sedimentation in a late archean successor basin abitibi greenstone belt quebec canada in the south central part of the abitibi greenstone belt a succession of archean epiclastic sediments at least 2 km thick was deposited in the duparquet basin the destor porcupine fault and a secondary fault that splays off the major fault define the margins of this basin which is at least 15 km long and up to 2 5 km wide sedimentary evidence of tectonic influence includes i rapid vertical and lateral facies changes over tens of metres ii cyclic repetition of facies associations iii mixed fining upward coarsening upward fining upward sequences in conglomerate units iv local derivation of most clasts and v asymmetric distribution of fan deltas and braid deltas along the strike of the fault bounded basin three basic facies associations are recognized i conglomerate sandstone facies association csfa ii sandstone argillite facies association safa and iii argillite sandstone facies association asfa the csfa which predominates at the faulted basin margins constitutes 60

volcanism and related slope to shallow marine volcaniclastic sedimentation an archean example near chibougamau quebec canada abstract volcaniclastic sedimentary rocks and k rich lava flows of the archean hauy formation are discontinuously exposed in a 850 m thick sequence in the waconichi synclinorium northwest of chibougamau quebec the interstratified sedimentary rocks comprise two major sedimentary facies associations the graded bedded facies association wbfa indicative of deposition by sediment gravity flows and the wavy bedded facies association wbfa defined by wave induced structures the gbfa is near the base of the stratigraphic section and is interstratified up section with the wbfa in the gbfa the abundance of synsedimentary folding truncated slump folds load casts and low angle erosional surfaces as well as sediments deposited by turbidity currents and debris flows support designation as a volcanic slope deposit in the wbfa trough crossbeds wavy bedded gravels and plane bedded volcaniclastic sandstones are indicative of a nearshore setting the abundance of angular to subangular lithic volcanic fragments and broken and euhedral pyroxene crystals in the sediments is suggestive of a pyroclastic origin some beds may represent primary pyroclastic material but unequivocal petrographic recognition of pumice or glass shards is not possible because of metamorphic overprint composition suggests an initial magmatic or phreatomagmatic eruption subsequently reworked along the shoreline and transported downslope lava flows comprising massive to lobate andesites and massive to blocky basalts constitute most of the stratigraphic sequence pillowed flows are strikingly absent from the section both compositional types have an increase in vesicularity and change in flow form up section from massive to lobate or blocky suggesting progressively shallower water depths the composite character represented by hauy lava flows and associated volcaniclastic sediments in characteristic of stratovolcanoes the studied section is an integral part of an evolved arc with an adjacent backarc basin the volcano sedimentary facies indicate the development of a volcanic island in one of these basins

large and small scale spatial evolution of digitally processed ocean wave spectra from seasat synthetic aperture radar precision digitally processed and corrected synthetic aperture radar sar image spectra along a large portion of seasat orbit 1339 september 28 1978 have revealed a number of unique potentials but also some substantial limitations of spaceborne sar for global ocean wave monitoring sar appears to be capable of monitoring the spatially evolving ocean wave number spectrum with high statistical reliability the large scale few hundred kilometer spatial evolution of the spectrum is generally consistent with the location in time and space of wave generating sources even when multiple wave systems are present on a more local scale of just a few tens of kilometers the nearshore wave number spectrum responds to local depth changes but is too noisy to respond reliably to local current changes the seasat sar was severely restricted in its ability to sense azimuthtraveling along track waves in high sea states azimuth waves corresponding to ocean wavelengths shorter than about 200 m were either undetected or severely attenuated in the higher sea states hs 2 m azimuth waves shorter than 100 m are not detectable in even the lowest sea states moreover there is a tendency for attenuated wave systems to be shifted toward the range direction this effect will significantly impede studies of spatial evolution of seasat sar spectra without some additional correction strategy

sandy high energy flood sedimentation some criteria for recognition with an example from the devonian of s w england abstract many modern sand deposits resulting from episodic floods in semi arid zones are dominated by parallel laminations but parallel laminated sands are not a major feature in perennial streams single flood events may deposit over 1 5 m of parallel laminated sand hence ancient parallel laminated sand dominated alluvial deposits may be the product of ephemeral flows the trentishoe formation hangman sandstone group middle devonian of north devon consists in part of laterally extensive beds of parallel laminated fine grained red sandstones that build multistorey sand bodies individual beds are little more than 1 m thick but may extend laterally for hundreds of metres a vertical sequence of erosion surface sparse silt clasts parallel laminations silt drape is often found suggesting high flow stage deposition of plane bedded sand followed by a very rapid waning of flow with silt fallout in the final stages of the flood this sequence bears marked similarity to certain modern ephemeral flow sands

latest pleistocene and holocene alpine glacier fluctuations in scandinavia abstract during the early holocene abrupt decadal to centennial scale climate variations caused significant glacier variations in norway increased freshwater inflow to the north atlantic and arctic oceans has been suggested as one of the most likely mechanisms to explain the abrupt and significant lateglacial and early holocene climatic events in nw europe the largest early holocene glacier readvances occurred 11 200 10 500 10 100 9700 9200 and 8400 8000 cal yr bp the studied norwegian glaciers apparently melted away at least once during the early mid holocene the period with the most contracted glaciers in scandinavia was between 6600 and 6000 cal yr bp subsequent to 6000 cal yr bp the glaciers started to advance and the most extensive glaciers existed at about 5600 4400 3300 2300 1600 cal yr bp and during the little ice age times with overall less glacier activity were apparently around 5000 4000 3000 2000 and 1200 cal yr bp it has been proposed that several glacier advances occurred in scandinavia including northern sweden at 8500 7900 7400 7200 6300 6100 5900 5800 5600 5300 5100 4800 4600 4200 3400 3200 3000 2800 2700 2000 1900 1600 1200 1000 and 700 200 cal yr bp glaciers in northern sweden probably reached their greatest little ice age extent between the 17th and the beginning of the 18th centuries evidence for early holocene glacier advances in northern scandinavia however has been questioned by more recent multi disciplinary studies the early to mid holocene glacier episodes in northern sweden may therefore be questioned most norwegian glaciers attained their maximum little ice age extent during the mid 18th century cumulative glacier length variations in southern norway based on marginal moraines dated by lichenometry and historic evidence show an overall retreat from the mid 18th century until the 1930s 40s subsequently most norwegian glaciers retreated significantly maritime outlet glaciers with short frontal time lags 15 20 years continued their retreat to the 1970s and 1980s however maritime glaciers started to advance as a response to higher winter accumulation during the first part of the 1990s after 2000 several of the observed glaciers have retreated remarkably fast annual frontal retreat 100 m mainly due to high summer temperatures the general glacier retreat during the early holocene and the neoglacial advances after 6000 cal yr bp are in line with orbital forcing due to the decrease of northern hemisphere summer solar insolation and the increase in winter insolation in addition regional weather modes such as the north atlantic oscillation nao and the arctic oscillation ao play a significant role with respect to decadal and multi decadal climate variability

on solar forcing of holocene climate evidence from scandinavia the focus of this study is the possible correlation between changes in the climate of scandinavian and changes in solar irradiation reliable information about holocene climatic change in sweden and norway is currently available from two main sources the 14c dating of pine wood retrieved from above the present pine tree limit and studies of glacier variations based on proglacial lacustrine sediments and on moraines the reconstructed alpine tree limit reveals that summer temperature in general was warmer during the early holo cene than it was during the late holocene superimposed on this general trend are several fluctuations of a few hundred years duration relatively cold periods with a duration of the order of 300 600 years occurred frequently during the holocene in this paper dates of the major climatic events are compared with an index of solar activity the so called 14c anomalies for most of the last 9000 years a good correspondence is demonstrated between the timing of cold events in scandi

cosmogenic 10be and 26al ages of holocene moraines in southern norway i testing the method and confirmation of the date of the erdalen event c 10 ka at its type site abstract cosmogenic nuclide dating 10be and 26al is applied to boulders on two moraine ridges at the type site of the early holocene erdalen event southern norway dated previously using radiocarbon quartz rich rock samples yielded 10be age estimates between 9 8 1 2 and 10 1 1 1 ka external uncertainties 1 with an average of 9 95 ka these age estimates are statistically indistinguishable from the independent radiocarbon age estimate 26al age estimates which ranged from 9 4 1 1 to 11 2 1 3 ka and averaged 10 1 ka provided useful corroboration of the 10be results although current levels of precision and accuracy are insufficient to distinguish between the ages of younger inner and older outer moraines the results demonstrate the potential of the method at suitable sites where radiocarbon dating is not possible several environmental factors including effective glacial erosion stability of moraine slopes snow cover of sufficiently shallow depth and short duration and the absence

late orogenic basins in the archaean superior province canada characteristics and inferences abstract the late orogenic archaean duparquet kirkland and stormy basins of the canadian superior province are characterized by bounding crustal scale faults and abundant porphyry stock emplacement lava flows and pyroclastic deposits are restricted to the kirkland and stormy basins and coarse clastic detritus characterizes the duparquet basin seven distinct lithofacies are identified 1 mafic volcanic 2 felsic volcanic 3 pyroclastic 4 volcaniclastic 5 conglomerate sandstone 6 sandstone argillite conglomerate and 7 argillite sandstone tuffaceous sandstone the mafic and felsic volcanic lithofacies represent effusive lava flows the pyroclastic lithofacies is formed of subaerial surge and airfall deposits and the volcaniclastic lithofacies is composed of reworked volcanic debris the conglomerate sandstone lithofacies is interpreted as alluvial fan fan delta or proximal braided stream deposits whereas the sandstone argillite lithofacies is consistent with sandy dominated flood or braidplain deposits a dominantly shallow water lacustrine setting is inferred for the argillite sandstone lithofacies these different lithofacies record the basin history and can be used to identify basin forming processes lithofacies stacking and rapid lateral changes of lithological units in conjunction with interformational unconformities and basin margin faults suggest tectonically induced sedimentation volcanism can also influence basin evolution and the delicate balance between erosion sedimentation and prevalent transport processes is affected by volcanic input catastrophic influx of pyroclastic material facilitated mass wasting processes and formation of non confined hyperconcentrated flood flow deposits account for local congestion of alluvial or fluvial dispersal patterns confined stream flow processes govern sedimentation during intravolcanic phases or prominent tectonic uplift in addition climate which controls the weathering processes and vegetation which stabilizes unconsolidated material affects the transport and depositional process a co 2 rich aggressive weathering humid archaean atmosphere favours traction current deposits and an absence of vegetation promotes rapid denudation although tectonism is the prevalent long term controlling factor in restricted basins the effects of volcanism climate and lack of vegetation can also be detected

radiocarbon dated evidence of worldwide early holocene climate change radiocarbon dated glacial deposits from several different areas of the world indicate that alpine glaciers and ice caps in parts of both the northern and southern hemispheres expanded in response to climate change in early holocene time these data suggest that a worldwide episode of cooler climate similar in scope to the more recent neoglaciation occurred ca 8 500 7 500 yr b p

transgressive facies in the south munster basin ireland this paper describes the sedimentation style associated with the basal carboniferous transgression in southern ireland and the influence which this event had on the palaeogeography of the region the transgression as marked by the base of the carboniferous succession is shown to represent one of several genetically related transgressive pulses which commenced during the late devonian at this time an east west trending graben the south munster basin developed in southern ireland this was initially a non marine depositional site in which sediment was derived from the north and west subsidence and eustatic sea level rise resulted in a marine transgression which proceeded in a rhythmic style resulting in a number of transgressive stillstand pulses the first transgressive pulse t1 advanced in a westerly direction along the basin axis resulting in the development of an epicontinental like sea the shoreline remained essentially static along the northern basin margin initially until a second transgressive pulse t2 resulted in expansion of the marine area the latter proceeded by gradual northward erosive advance of a barred coastal area as far as the northern basin margin where the stability of the bounding platform halted its progress erosion of the barrier shoreface was insufficient to destroy all the backbarrier lagoonal deposits which are preserved as a thin transgressive diachronous unit which grades northwards to a coastal alluvial plain immediately preceding the basal carboniferous transgression t3 a shallow wave dominated storm influenced shelf sea occupied the basinal area two sublittoral sand bar complexes developed on the shelf under the influence of shore parallel current regimes apparently derived from source areas located on either side of the epicontinental sea the basal carboniferous transgression took place in two pulses the first t3a resulted in a rapid reduction in sand supply to the shelf and deposition of clay the barrier shoreline responded by erosively retreating across the lagoon leaving a transgressive lag in its wake its northwards advance was however limited due to the relative stability of the northern platform sand supply to the shelf was completely terminated in the second pulse t3b and the barrier rapidly migrated erosively across the northern platform for a considerable distance such that the coastal plain is overlain by a thin transgressive lag this transgressive phase was immediately followed by shoreline stillstand and progressive shallowing of the shelf an open sandy shelf developed on which offshore sand bars accumulated under a storm and wave dominated regime clay deposition continued in the deeper part of the basinal area but was eventually terminated as the shelf sands prograded centripetally into the basin the main factor that controlled the style of the overall transgression was an interplay between eustatic sea level rise and basin subsidence the rate of relative sea level rise together with the effect of differential subsidence and fluvial input from the north appear to have diminished with time the rate at which successive transgressive pulses advanced northwards shows an overall progressive increase

a comparison of evidence for late holocene summer temperature variations in the northern hemisphere data on glacier tree line tree ring pollen and ice core variations in north america greenland and europe during the last 2000 yr up to a d 1800 are compared in detail on the century time scale only data that may be indicative of summer temperature changes are included since these comprise most of the available paleoclimatic information although some variations especially of glaciers may have been in response to precipitation changes instead radiocarbon dates and 14c dated records are converted to calendar dendrochronological years using the calibration of m stuiver 1982 radiocarbon 24 1 26 despite the basic uncertainties in dating interpretation response times and noise level of proxy climatic data there is at times good agreement among different kinds of evidence from within a region to suggest an episode of generally warmer or cooler summers three previously identified episodes find expression in records from all of the regions considered the little ice age of the last few centuries a medieval warm period around the 12th century a d and an earlier cold period some time between the 8th and 10th centuries however the timing of minima and maxima within these episodes seems to have varied from region to region although the evidence is consistent within regions in the 15th century summers were warm in the eastern canadian arctic and southern greenland while there was a cold episode in europe and western north america

holocene glacier variation chronology of the smorstabbtindan massif jotunheimen southern norway and the recognition of century to millennial scale european neoglacial events new stratigraphic evidence for the holocene history of three glaciers in central jotunheimen southern norway is presented and the implications for century to millennial scale glacier and climatic variability are considered minerogenic layers in seven stream bank mires flooded episodically by glaciofluvial meltwater are dated by 79 new radiocarbon age estimates a revised chronology for glacier variations in smorstabbtindan suggests a three phase holocene 1 an early holocene deglaciation phase 11500 9500 cal bp characterized by readvances of ice sheet remnants 2 a mid holocene phase with relatively small or absent glaciers 9500 5000 cal bp and 3 a late holocene phase of enlarged and fluctuating glaciers the last 5000 years seven millennial scale neoglacial events smorstabbtindan i vii during which glaciers were larger than at present for most of the time are dated to 10 400 9600 erdalen event 8400 7650 finse event 4800 3900 3200 2550 2350 1700 1400 750 and 500 0 cal

the observation of ocean surface phenomena using imagery from the seasat synthetic aperture radar an assessment over the period july 4 to october 10 1978 the seasat synthetic aperture radar sar gathered 23 cm wavelength radar images of some 108 km2 of the earth s surface mainly of ocean areas at 25 40 m resolution our assessment is in terms of oceanographic and ocean monitoring objectives and is directed toward discovering the proper role of sar imagery in these areas of interest in general sar appears to have two major and somewhat overlapping roles first quantitative measurement of ocean phenomena like long gravity waves and wind fields as well as measurement of ships second exploratory observations of large scale ocean phenomena such as the gulf stream and its eddies internal waves and ocean fronts these roles are greatly enhanced by the ability of 23 cm sar to operate day or night and through clouds to begin we review some basics of synthetic aperture radar and its implementation on the seasat spacecraft seasat sar imagery of the ocean is fundamentally a map of the radar scattering characteristics of 30 cm wavelength ocean waves distorted in some cases by ocean surface motion we discuss how wind stress surface currents long gravity waves and surface films modulate the scattering properties of these resonant waves with particular emphasis on the mechanisms that could produce images of long gravity waves doppler effects by ocean motion are also briefly described measurements of long wavelength 100 m gravity waves using seasat sar imagery are compared with surface measurements during several experiments combining these results we find that dominant wavelength and direction are measured by seasat sar within 12 and 15 respectively however we note that ocean waves are not always visible in sar images and discuss detection criteria in terms of wave height length and direction sar estimates of omnidirectional wave height spectra made by assuming that sar image intensity is proportional to surface height fluctuations are more similar to corresponding surface measurements of wave height spectra than to wave slope spectra because seasat sar images show the radar cross section of 30 cm waves neglecting doppler effects and because these waves are raised by wind stress on the ocean surface wind measurements are possible comparison between wind speeds estimated from seasat sar imagery and from the seasat satellite scatterometer sass agreed to within 0 7 m s over a 350 km comparison track and for wind speeds from 2 to 15 m s the great potential of sar wind measurements lies in studying the spatial structure of the wind field over a range of spatial scales of from 1 km to 100 km at present the spatial and temporal structure of ocean wind fields is largely unknown because sar responds to short waves whose energy density is a function of wind stress at the surface rather than wind speed at some distance above the surface variations in image intensity may also reflect changes in air sea temperature difference thus complicating wind measurements by sar because sar images show the effects of surface current shear air sea temperature difference and surface films through their modulation of the 30 cm waves seasat images can be used to locate and study the gulf stream and related warm water rings tidal flows at inlets internal waves and slicks resulting from surface films in many of these applications sar provides a remote sensing capability that is complementary to infrared imagery because the two techniques sense largely different properties namely surface roughness and temperature both stationary ships and moving ships with their attendant wakes are often seen in sar images ship images can be used to estimate ship size heading and speed however ships known to be in areas imaged by sar are not always detectable clearly a variety of factors such as image resolution ship size sea state and winds could affect ship detection overall the role of sar imagery in oceanography is definitely evolving at this time but its ultimate role is unclear we have assessed the ability of seasat sar to measure a variety of ocean phenomena and have commented briefly on applications in the end oceanographers and others will have to judge from these capabilities the proper place for sar in oceanography and remote sensing of the ocean

polarimetric sar data compensation for terrain azimuth slope variation this paper addresses the problem of polarimetric sar polsar data correction for changes in radar cross sections which are caused by azimuth slopes most radiometric slope corrections remove slope effects to account for the effective scattering pixel area however few studies address the slope effect on the radar cross section as a function of polarization states the authors propose two approaches to compensate for this azimuth slope effect for polsar data in the first approach the digital elevation model dem obtained from interferometric sar or from other means is used to estimate orientation angles and in the second approach orientation angles are derived directly from the polsar data they have developed three new methods to implement this second approach one is based on the right right and left left circular polarizations and the other two are based on cloude s and huynelt s decompositions the results are compared with the original polarization signature method using the dem generated orientation angles as the reference polsar data is then compensated using the derived orientation angles significant changes were observed in many elements of the coherency matrix the compensated polsar data should improve the accuracy of geophysical parameter estimation techniques nasa jpl airsar data for an area in central california is used for illustration

evolution of the norwegian plateau icefield hardangerjokulen since the little ice age the maximum little ice age lia glacier extent provides a significant baseline to assess long term glacier change and to place currently observed rates of glacier recession in a broader temporal

holocene glacier fluctuations in the american cordillera abstract in many areas of the american rocky mountains colorado wyoming utah idaho montana cascade range washington oregon and the sierra nevada california radiocarbon ages suggest that ice receded to near present limits before 10 ka bp a pre altithermal readvance or stillstand left moraines ca 1 3 km beyond and ca 50 300 m below present glacier margins at one locality on glacier peak in washington these deposits are perhaps dated to the early holocene but in general these deposits are probably at least 10 ka old glacial advances during the altithermal ca 8 to 5 ka bp elsewhere are rare radiocarbon evidence for altithermal glacial advances in the colorado front range is questionable the earliest radiocarbon dated neoglacial advances occurred about 5 ka bp in the washington cascades moraines and related deposits believed to be of early neoglacial age i e 5 to 3 ka bp elsewhere are poorly dated for example moraines believed to date to the early neoglacial in colorado triple lakes and wyoming temple lake are actually late pleistocene age based on radiocarbon ages derived from lake sediments at the type localities although relative age data i e lichens rock weathering soils from many areas suggest a three fold neoglacial sequence little supporting radiocarbon evidence is available however tephrochronology distinguishes three neoglacial advances near mount rainier in washington in most mountain ranges of the western united states fresh unweathered sharp crested moraines usually adjacent to present ice margins or near headwalls in empty cirques date to the little ice age of the last several centuries however detailed photographic or other historical records of glacial fluctuations during the last century are rare and detailed mass balance studies rarer still whether or not pre little ice age glacial fluctuations in the american cordillera are synchronous must await better radiometric dating of local moraine sequences

modern glacier characteristics as a basis for inferring former climates with particular reference to the loch lomond stadial abstract studies of the mass balance of modern glaciers have indicated that the equilibrium line altitude ela is the most critical parameter in the link between glaciers and climate average accumulation on a glacier includes components derived from direct precipitation on the glacier surface as well as wind drifting and avalanching of snow and approximates closely to accumulation at the equilibrium line ablation is most usefully predicted by mean summer temperature and there is a close non linear relationship between accumulation and mean summer temperature at the equilibrium line following discussion of methods of reconstructing former glaciers and calculating their equilibrium line altitudes the application of the above relationships to the loch lomond readvance glaciers of highland britain is considered and an outline of the precipitation pattern and the mean summer temperature of the loch lomond stadial is given

real time observations of southern ocean wave fields from the shuttle imaging radar during the april and october 1994 flights of the space shuttle endeavour c band synthetic aperture radar sar signal was acquired and processed in real time into ocean wave images and two dimensional image spectra by an on board processor the image spectra were transmitted to the ground as they were acquired during 20 days of observations spanning the two missions over 100000 spectra were collected these data provide the first truly synoptic directional measurements of the southern ocean wave field with additional processing estimates of ocean wavelength and propagation direction were extracted from the spectra during the october mission daily comparisons of these estimates with wave model predictions were made available at a world wide web site the authors describe the computations performed by the processor and the real time data flow and ground processing in addition they summarize and interpret some gross characteristics of the processor observed real time wave field from the april and october missions

measurement of topography using polarimetric sar images a processing technique for polarimetric synthetic aperture radar sar data has been developed which produces profiles of terrain slopes and elevations in the azimuthal or along track direction this technique estimates the average shift in orientation angle of copolarization backscatter caused by azimuthal tilts of the scattering plane using p band data tests of this technique have been made for an area in the black forest near villingen schwenningen in baden wurttemberg germany the radar measured slope and derived elevation profiles have low rms errors and high correlation values when compared with a stereo photograph digital elevation map dem for the area this algorithm is capable of adaptively making transitions from the forested areas to nearby regions with open terrain subsequent tests of the algorithm have been conducted using polarimetric sar l band data for a mountainous nonforested region in the mojave desert ft irwin ca where an accurate dem also was available complete elevation and slope mapping of the terrain in two dimensions using this technique is possible when azimuthal elevation profiles are produced throughout the range extent of the sar image

late pleistocene glacial equilibrium line altitudes in the colorado front range a comparison of methods abstract six methods for approximating late pleistocene pinedale equilibrium line altitudes elas are compared for rapidity of data collection and error rmse from first order trend surfaces using the colorado front range trend surfaces computed from rapidly applied techniques such as glaciation threshold median altitude of small reconstructed glaciers and altitude of lowest cirque floors have relatively high rmses 97 186 m because they are subjectively derived and are based on small glaciers sensitive to microclimatic variability surfaces computed for accumulation area ratios aars and toe to headwall altitude ratios thars of large reconstructed glaciers show that an aar of 0 65 and a thar of 0 40 have the lowest rmses about 80 m and provide the same mean ela estimate about 3160 m as that of the more subjectively derived maximum altitudes of pinedale lateral moraines rmse 149 m second order trend surfaces demonstrate low elas in the latitudinal center of the front range perhaps due to higher winter accumulation there the mountains do not presently reach the ela for large glaciers and small front range cirque glaciers are not comparable to small glaciers existing during pinedale time therefore pleistocene ela depression and consequent temperature depression cannot reliably be ascertained from the calculated ela surfaces

a new approach to calculating holocene winter precipitation by combining glacier equilibrium line altitudes and pine tree limits a case stud from hardangerjokulen central southern norway at hardangerjokulen central southern norway detailed knowledge of the number age and magnitude of holocene glacier fluctuations is used to reconstruct variations in equilibrium line altitude ela for the last 10 000 years present and past elas are based on an accumulation area ratio aar of 0 7 and are adjusted for land uplift a synchronous relationship between advanced glacier positions and the highest pine tree limits pinus sylvestris l is demonstrated for the early to mid holocene in southern scandinavia which indicates that warm summers were compensated for by high winter precipitation based on pine tree limit fluctuations as a measure of mean ablation season temperature holocene variations in winter precipitation at hardangerjokulen have been calculated by substitution in the close exponential relationship between mean ablation season temperature and winter precipitation at the ela of norwegian glaciers setting the winter precipitation during the period ad 1961 1990 at 100 mean values

a terrestrial shallow marine transition in the archean opemisca group east of chapais quebec abstract the stella and hauy formations of the archean opemisca group in the eastern chapais syncline feature numerous fluvial to shallow marine transitions throughout the stratigraphic sequence during the first depositional phase stella formation relatively high gradient alluvial fans prograde into a shallow marine environment the coarse clastic sediments reflect a scott type depositional environment the initial depositional environment is envisaged to be a high energy wave and storm flood dominated coastline bordered by coastal alluvial fans shallow marine deposits consist of coarse to very coarse grained sandstones and intraclast and pebble to cobble conglomerates the prevalent shallow marine sediments are related to storm and or flood deposition terrigenous sediments of the donjek type depositional environment prevail during the second depositional phase hauy formation the shallow marine sediments although still wave and storm flood dominated are finergrained and when correlated with the terrigenous sediments imply a lower gradient and a maturing of the coastline furthermore contemporaneous volcanism of andesitic shoshonitic to basaltic composition occurs during this evolutionary stage the sedimentary basin gradually evolved during the two depositional phases the repetition of terrigenous and shallow marine sediments throughout the stratigraphic sequence coarsening and fining sequences in the conglomerates and the alluvial fan setting strongly suggest a fault bounded basin margin tectonic uplift of the hinterland initiates alluvial fan progradation onto the shelf whereas quiescent periods are documented by marine transgression the clast composition of the conglomerates and the alluvial fan environment suggest local derivation of clasts the synvolcanic chibougamau pluton and the lake dore complex acted as a stable basement during deposition of the opemisca group the small landmass served as a stable platform for shallow marine deposition even when tectonically influenced a late phase intraplutonic cratonic development of an initial backarc basin system internal zone of the abitibi greenstone belt is proposed as the overall depositional setting of the chapais basin

on polarimetric characteristics in sar images of mesoscale cellular convection in the marine atmospheric boundary layer 1 convection is an important phenomenon in the marine atmospheric boundary layer mabl previous spaceborne radar studies of such have been limited to single polarization data and therefore their focus was on the variation in intensity of the radar return which was constrained by the existence of a single polarization image pattern representing different atmospheric and oceanic phenomena in this paper we study the polarimetric characteristics of mesoscale cellular convection mcc in the mabl using high resolution data from fully polarimetric hh vv hv and vh radarsat 2 rs 2 synthetic aperture radar sar images in conjunction with closely collocated mesoscale atmospheric model simulations to identify the mcc signatures to compare the polarimetric characteristics of mcc with those of the ocean surface our analysis also includes 641 open ocean surface quad polarization rs 2 sar images collocated with 52 national data buoy center buoys the open ocean surface sar images exhibit different polarimetric characteristics from those of mcc thus we differentiate mcc from other open ocean phenomena based on identifiable polarimetric sar characteristics

theory of synthetic aperture radar ocean imaging a marsen view this paper reviews basic synthetic aperture radar sar theory of ocean wave imaging mechanisms using both known work and recent experimental and theoretical results from the marine remote sensing marsen experiment several viewpoints that have contributed to the field are drawn together in a general analysis of the backscatter statistics of a moving sea surface a common focus for different scattering models is provided by the mean image impulse response function which is shown to be identical to the spatially varying frequency variance spectrum of the local complex reflectivity coefficient from the analysis has emerged a more complete view of the sar imaging phenomenon than has been previously available a new generalized imaging model is proposed

late holocene glacier fluctuations in bevringsdalen jostedalsbreen region western norway ca 3200 1400 bp lithostratigraphy and radiocarbon dates from a 1 3 m deep gully section in bevringsdalen sw of jostedalsbreen in western norway with alternating minerogenic glacial and peat non glacial layers demonstrate that glaciers upvalley from the site were present during the following intervals 2595 85 bp 840 700 cal bc to 2360 80 bp 525 385 cal bc between 2250 65 bp 395 225 cal bc and 2150 80 bp 360 105 cal bc between 1740 75 bp cal ad 205 385 and 1730 75 bp cal ad 210 395 and subsequent to 1430 45 bp cal ad 595 645 detailed altitudinal fluctuations of the glaciation threshold equilibrium line relative to the present have been reconstructed for the time interval between 1430 45 bp cal ad 595 645 and 3180 90 bp 1540 1395 cal bc

climatic and tectonic influences on fan deltas and wave to tide controlled shoreface deposits evidence from the archaean keskarrah formation slave province canada the 2 6 ga keskarrah formation located in the central slave province northwest territories canada is a late orogenic tectonically controlled sedimentary sequence that developed under unusual climatic and depositional conditions the formation is adjacent to the crustal scale north trending beniah lake fault and overlies the 3 15 ga augustus granite the 2 69 2 7 ga mafic volcanic peltier formation and the turbiditic contwoyto formation unconformably principal lithofacies in the keskarrah formation include conglomerate sandstone and siltstone sandstone the conglomerate lithofacies represents coalescing gravelly streamflow dominated fan deltas adjacent to topographic highs up section quartz rich arenites and quartz arenites of the sandstone lithofacies are interpreted to be shallow water shoreface deposits influenced by wave action and tides the overlying feldspathic litharenites of the siltstone sandstone lithofacies are consistent with a lower shoreface to proximal offshore environment dominated by wave and tide interaction tidal influence in both sandstone dominated lithofacies is inferred from the presence of mudstone laminae between bedforms and on foresets of cross beds as well as from abundant reactivation surfaces with local mudstone drapes intense chemical weathering during the archaean resulting from elevated atmospheric co2 levels higher temperatures and moist climatic conditions played an important role in the development of quartz rich arenites that appear to be first cycle deposits few lithic fragments and feldspar grains are preserved due to in situ host rock weathering chemical weathering during transport and wave and tide action hydraulic sorting and abrasion in the shoreface environment contributed to the continued breakdown and transport of labile minerals increased proportions of lithic fragments in sandstone beds of the conglomerate lithofacies are the result of shorter transport distances from source areas to the depositional environment abundant conglomerate with up to 4 m large granitic boulders derived from the adjacent augustus granite and mafic clasts from the peltier formation indicate high relief and fault related uplift and subsidence the intimate association of fan deltas and wave and tide influenced shallow marine deposits in association with quartz rich sandstones forming in a high relief area make the keskarrah formation remarkable in the rock record

a late younger dryas early holocene tephrostratigraphy for fosen central norway a number of rapid climate oscillations occur during the lateglacial early holocene 15 8 ka bp period and a well developed tephrostratigraphy in association with these oscillations increases the po

evidence from north west canada for an early holocene milankovitch thermal maximum according to the milankovitch theory of global climatic change maximum summer solar radiation at high latitudes of the northern hemisphere occurred at 10 000 yr bp refs 1 2 in particular it predicts summer solstice radiation greater by 9 10 preliminary climate simulation experiments with these increased values of radiation confirm that high latitude land surfaces received maximal insolation at 10 000 yr refs 3 4 paradoxically however the large volume of fossil pollen and other evidence from north america indicates a maximum of holocene warmth at 7 000 6 000 yr ref 5 and a recent review of the evidence from new england suggests that the warming began at 9 000 and ended at 5 000 yr but also stresses the difficulties of interpretation in terms of climate change6 we summarize here data from sites in the north west corner of mainland canada fig 1 that directly support the milankovitch hypothesis

equilibrium line altitudes and paleoenvironment in the merchants bay area baffin island n w t canada the fiordlands south of merchants bay contain an extensive well preserved moraine record of a late foxe advance of local valley glaciers this has allowed accurate reconstruction of former glacier margins and computation of former equilibrium line altitudes elas by a variety of methods statistical comparison of three methods maximum lateral moraine elevation median elevation and accumulation area ratio aar shows that different techniques can give different results for the same glaciers lateral moraines gave estimates that were too low probably due to post glacial erosion or to non deposition median elevations and the aar method produced statistically similar results but only for glaciers of simple geometry the median elevation method fails to take into account variations in valley morphology and glaciological parameters and so is not reliable in all situations the aar method is supported by empirical evidence and is the best of the three methods for estimating former elas analysis of trend surfaces of present and late foxe elas shows changes in elevation and orientation through time due to changing environmental factors present elas are strongly influenced by local factors southerly storm tracks and warm maritime conditions paleo elas do not show this influence suggesting that davis strait may have been ice covered during the late foxe stade and that storm tracks were from the north

directional wave spectra measured with the surface contour radar abstract the surface contour radar is a 36 ghz computer controlled airborne radar which generates a false color coded elevation map of the sea surface below the aircraft in real time and can routinely produce ocean directional wave spectra with post flight data processing which has much higher angular resolution than pitch and roll buoys when compared with waveriders and the xerb and edeco pitch and roll buoys there is good agreement among the nondirectional spectra there is also good agreement among the angles associated with a1 b1 and a2 b2 fourier coefficients of the spreading function for xerb endeco and the surface contour radar there are indications that the pitch and roll buoys in this study may have calibration problems with the magnitudes of the fourier coefficients of the spreading function and that the radar system determines the fourier coefficients with significantly less noise and bias the high spatial resolution and rapid mapping capability over extensive areas make the surface

holocene glacier history of bjornbreen and climatic reconstruction in central jotunheimen norway based on proximal glaciofluvial stream bank mires abstract holocene variations of bjornbreen smorstabbtinden massif west central jotunheimen are reconstructed from the lithostratigraphy of two alpine stream bank mires flooded episodically by meltwater the approach uses multiple sedimentological indicators weight loss on ignition mean grain size grain size fractions bulk density moisture content and magnetic susceptibility an a priori model of overbank deposition of suspended glaciofluvial sediments a detailed chronology based on 56 radiocarbon dates and a little ice age sedimentological analogue rapid late preboreal deglaciation was indicated by immigration of betula pubescens by 9700 cal bp an interval of at least 3000 years in the early holocene when glaciers were absent was interrupted by two abrupt episodes of glacier expansion around the time of the finse event the first at ca 8270 7900 cal bp bjornbreen i event and the second at ca 7770 7540 cal bp bjornbreen ii event neoglaciation began shortly before ca 5730 cal bp with gradual build up to the maximum of the bjornbreen iii event at ca 4420 cal bp later maxima occurred at ca 2750 cal bp bjornbreen iv event and at 1300 1260 1060 and 790 cal bp all within the bjornbreen v event glaciers were smaller than today and possibly melted away on several occasions in the late holocene ca 3950 1410 and 750 cal bp minor maxima also occurred at ca 660 and 540 cal bp within the late mediaeval warm period and the early little ice age respectively the little ice age maximum was dated to 213 25 bp ca 205 cal bp the relative magnitudes of the main glacier maxima were determined erdalen event little ice age event bjornbreen vi bjornbreen i finse event bjornbreen ii bjornbreen v bjornbreen iv bjornbreen iii these episodic events of varying magnitude and abruptness were used in conjunction with an independent summer temperature proxy to reconstruct variations in equilibrium line altitude ela and a holocene record of winter precipitation since the preboreal ela varied within a range of about 390 m and winter precipitation ranged between 40 and 160 of modern values winter precipitation variations appear to have been the main cause of these century to millennial scale holocene glacier variations

holocene moraine chronology spitsbergen svalbard lichenometric evidence for multiple neoglacial advances in the arctic late holocene neoglacial moraines occurring within 1 or 2 km of present glacier margins are prominent features in the forefields of spitsbergen glaciers little ice age moraines are typically the most extensive and best preserved moraines of older holocene advances are much less common where observed older moraines occur as moraine remnants and provide irrefutable evidence of earlier neoglacial advances the fragmentary moraine record indicates two little ice age advances and two older neoglacial advances lichenometry provides calibrated ages for periods of moraine stabilization the oldest moraines stabilized by ca 1500 years ago and a second group of moraines stabilized by ca 1000 years ago little ice age moraines were deposited during two periods an early group of moraines stabilized ca 650 years ago and a later group during the last several centuries the proposed moraine chronology compares well with other proxy climate records on spitsbergen and with moraine records from areas borde

the middle devonian shoreline in north devon england the hollowbrook formation is an early middle devonian regressive succession of sandstones and heterolithic facies marking a passage from shallow marine shelf muds through a sandy shoreface to continental ephemeral stream sheet sands ten facies are recognized arranged in two sequence types the shelf sequence consists of alternations of bioturbated muddy sandstone fair weather sediment and shelly concentrates or parallel laminated fine sandstone storm deposits the nearshore and foreshore sequences coarsen upwards and pass from bioturbated muddy sandstone shelf to lenticular beds inner shelf then either wavy and flaser beds fair weather lower shoreface or hummocky beds and multistorey parallel laminated sands with bioturbated tops lower shoreface storm shoals upper shoreface wave ripple cross laminated sandstones follow then parallel and planar cross laminated sandstones foreshore and parallel laminated lithic sandstone continental sheet flood the lower parts of the shoreface sequence and inner shelf are burrowed by skolithos arenicolites and chondrites the sequence differs from the high energy 9oregon coast9 shore in the absence of a megarippled facies and presence of much bioturbation but closely matches the sequence found in modern low energy wave influenced sandy shores such as sapelo island georgia

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

holocene fluctuations of a polythermal glacier in high alpine eastern jotunheimen central southern norway abstract bukkehammarbreen is a polythermal cirque glacier lying in the permafrost zone of eastern jotunheimen central southern norway in the proglacial lake bukkehammartjorna sediment analyses of loss on ignition loi magnetic susceptibility and analyses of grain size distribution have been used to reconstruct holocene variations in glacier activity and other catchment processes the glacier has low sediment production hence a low signal to noise ratio of minerogenic sediment flux is found grain size analyses are used to enhance the glacigenic signal and to detect glacier variations and other changes in sediment input the sedimentological record from bukkehammartjorn is compared with three other lake records from the same region in order to separate the glacial signal from variations in organic production and episodes of enhanced non glacial minerogenic sedimentation subsequent to the deglaciation after the younger dryas a preboreal glacial advance culminated before 10 100 cal bp this was followed by a prolonged period with no glaciers in the catchment until 7500 cal bp after which there is evidence of limited glacier activity lasting until 6800 cal bp between 6700 and 6000 cal bp the catchment was deglaciated after 6000 cal bp bukkehammarbreen reformed increasing in size towards 3800 cal bp with evidence for reduced glacier activity around 5200 cal bp a glacier with approximately similar size as at present has existed after 3800 cal bp the investigation has demonstrated the usefulness of multi site and multi parameter lacustrine investigations in reconstructing glacier fluctuations and for testing and validating the results the investigations have shown that grain size variations in sediment cores located at increasing distance from the meltwater inlet of a lake may provide an indicator of paraglacial activity in the catchment during the holocene the results also suggest that the lower altitudinal limit of permafrost in eastern jotunheimen remained below about 1800 m during the holocene

late pleistocene climate inferred from the reconstruction of the taylor river glacier complex southern sawatch range colorado abstract ice surface topography of a late pleistocene glacier complex herein named the taylor river glacier complex trgc was reconstructed on the basis of detailed mapping of glacial landforms combined with analyses of aerial photos and topographic maps during the last glacial maximum lgm the trgc covered an area of 215 km 2 and consisted of five valley or outlet glaciers that were nourished by accumulation in cirques basins and or upland ice fields equilibrium line altitudes elas for the glaciers of the trgc were estimated using the accumulation area ratio method assuming that ratio to be 0 65 0 05 elas thus derived ranged from about 3275 to 3400 m with a mean of 3340 60 m a degree day model ddm was used to infer the climatic significance of the lgm ela with no appreciable differences in precipitation with respect to modern climate the ela implies that mean summer temperatures during the lgm were 7 6 c cooler than today the ddm was also used to determine the temperatures required to maintain steady state mass balances for each of the reconstructed glaciers the required reductions in summer temperature vary little about a mean of 7 1 c the sensitivity of these results to slight 25 changes assumed for lgm precipitation are less than 0 5 c even under an lgm climate in which precipitation is assumed to be substantially different 50 than the present mean summer temperatures must be on the order of 7 0 to 8 5 c lower to depress equilibrium lines to lgm altitudes the greater sensitivity of the ela to changes in temperature suggests that glaciation in the region was driven more by decreases in summer temperature rather than increases in precipitation

glacier contraction during the middle holocene in the western italian alps evidence and implications radiocarbon dates of peat from the top and base of a bog exposed by recent retreat of rutor glacier show that the glacier front terminated upvalley from the bog from 8400 until at least 6000 b p the evidence is consistent with botanical data that point to a high tree line during the interval and to reconstructed mean july temperatures at least 4 c warmer than present temperatures if the mass balance history of the glacier is typical of other glaciers in this region it is likely that average equilibrium line altitudes during the interval of contraction remained above those of the present and well above those of subsequent neoglacial ice advances

timing equilibrium line altitudes and climatic implications of two early holocene glacier readvances during the erdalen event at jostedalsbreen western norway following the younger dryas the e rst evidence of glacial activity in southern norway in response to climatic change occurred during the early holocene when terminal moraines from the erdalen event formed beyond the position of later little ice age moraines in front of present outlet glaciers on both sides of the jostedalsbreen ice cap sets of pre little ice age marginal moraines have been morphostratigraphicallycorre lated with the erdalen event the lithostratigraphyin a peat bog at hellemyrane in jostedalen western norway provides e rm evidence for a two phase erdalen event associated with two glacier readvances of nigardsbreen at the preboreal boreal transition radiocarbon dates from the peat bog give age estimates for the two phases the e rst erdalen event readvance took place between 10 100 and 10 050 cal bp while the second occurred close to 9700 cal bp the lowering of the equilibrium linealtitude ela during these readvances is estimated using the little ice age ratio lr approach to be about 230 m and 215 m respectively the e rst readvance is attributed to an increase in winter precipitation while the second readvance may have been primarily caused by a marked drop in summer temperature which reactivated already existing ice masses

reconstruction of holocene glacier history from distal sources glaciofluvial stream bank mires and a glaciolacustrine sediment core near sota saeter breheimen southern norway this study attempts to reconstruct the holocene glacier history of breheimen southern norway from four stream bank mire sites and a downstream lake sediment core near sota saeter based on lithostr

measurement of ocean surface slopes and wave spectra using polarimetric sar image data abstract methods have been investigated which use fully polarimetric synthetic aperture radar sar image data to measure ocean slopes and wave spectra independent techniques have been developed to measure wave slopes in the sar azimuth and range directions the azimuth slope technique in particular is a more direct measurement than conventional intensity based backscatter cross section measurements in the azimuth direction wave induced perturbations of the polarimetric orientation angle are used to sense the wave slopes in the range direction a new technique involving the alpha parameter from the cloude pottier h a entropy anisotropy and averaged alpha polarimetric scattering decomposition theorem is used to measure slopes both measurement types are sensitive to ocean wave slopes and are directional taken together they form a means of using polarimetric sar polsar image data to make complete measurements of either ocean wave slopes or directional wave spectra these measurements must still contend with fundamental nonlinearities in the sar image processing i e azimuth direction velocity bunching that are due to wave velocity and acceleration effects nasa jpl airsar l and p band data from california coastal waters were used in the studies wave parameters measured using the new methods are compared with those developed using both conventional sar intensity based methods and with in situ noaa national data center buoy measurement products

topographic control of equilibrium line altitude depression on reconstructed little ice age glaciers grovabreen western norway little ice age marginal moraines in the grovabreen area inner sunnfjord are mapped and described the modem and little ice age mid eighteenth century equilibrium line altitude ela of the plateau glacier grovabreen is calculated by the use of an accumulation area ratio aar of 0 6 giving a little ice age ela depression of 125 m aar ela depression of the little ice age glaciers is also calculated for northern and southern outlet glaciers different estimates are considered to be the result of topographic differences other methods such as the mean elevation of glaciers meg and the toe to headwall altitude ratio thar gave ela depressions of 260 m and 315 m respectively these differences due to topographic conditions indicate that only glaciers with a uniform slope should be used to calculate the regional ela of former glaciers

reassessment of supposed early little ice age and older neoglacial moraines in the sandane area of western norway neoglacial moraines that are substantially older than the conventional little ice age glacier maximum of the mid eighteenth century have been recognized recently in the sandane area of western norway this is important in the context of scandinavian holocene glacier variations because in southern scandinavia at least it is widely accepted that glaciers were larger in the mid eighteenth century than at any time since the preboreal in this report we question and test the age of supposed early little ice age and older neoglacial moraines in two valleys in the sandane area observations and data relating to moraine morphology licheno metry and vegetation cover are reassessed and new lines of evidence based on boulder weathering schmidt hammer soil development and glaciofluvial activity are introduced critical appraisal of the evidence leads to the conclusion that the existence of pre or early little ice age moraines dating from the thirteenth to seventeenth centuries or indeed older neoglac

paleozoic lake faunas establishing aquatic life on land abstract lakes are important archives for continental records of paleoenvironmental as well as paleoclimatic change they also record a unique macroevolutionary pattern that occurred when faunas invaded the continental realm in order to document that pattern we compiled a database of over one hundred and six lake basins from the neoproterozoic to permian looking at this critical time in lacustrine evolution several patterns emerge for the neoproterozoic through silurian time there is a paucity of documented lake deposits and lake faunal records however the records that are available indicate that lakes were oligotrophic and their nutrient cycling regimes primitive it is not until the establishment of land plants in the silurian that lakes began to respond with higher diversities and more complex physical and chemical conditions during the devonian carboniferous periods diversity was on the rise as trophic structure became more complex most lakes of the devonian and carboniferous formed along continental margins or in tectonic basins with occasional connection to the marine realm the faunas from these types of lakes were commonly comprised of mixed marine and freshwater elements and were far more diverse than other more inland lakes this estuary effect created a gateway or filter through which faunas invaded the continental realm the early history of lake faunas is one of opportunity and amelioration the feedback loops created by the establishment of vascular plants altered the nutrient cycle on land and in lakes all trophic levels were established early but became increasingly complex throughout the paleozoic as roles changed and faunal elements became established groups invading the continents via the estuary effect did so numerous times before establishing themselves permanently this was linked with the episodic re establishment in marine freshwater connections along these continental margins

holocene glacier fluctuations of flatebreen and winter precipitation changes in the jostedalsbreen region western norvay based on glaciolacustrine sediment records the history of holocene glacier variations of flatebreen an independent glacier close to the sw part of the jostedalsbreen ice cap has been reconstructed from lacustrine sediments in the proglacial lake jarbuvatnet the sedimentary succession shows evidence of three maini episodes of holocene glacier expansion the first is recorded in the basal part of the core up to 370 cm according to the age depth relationship in the sediment core based on 12 ams radiocarbon dates this glacier expansion episode terminated about 10200 cal yr bp the second major glacier phase lasted from 8400 to 8100 cal yr bp while the third was initiated around 4000 cal yr bp and has continued up to the present at 43 cm in the core the medium silt content increases significantly accompanied by a minor increase in the sand content this textural change is interpreted as the first time that the tenninus of flatebreen extended inlto an upstream lake at 1083 m a s l the age model suggests that this event took place around

holocene glacier variations of blaisen hardangerjokulen central southern norway abstract a 1 m deep gully section 460 m beyond the maximum little ice age marginal moraines of blaisen hardangerjokulen central southern norway revealed alternations of minerogenic and organic sediments the geographical geological settings of the dated section provides a unique on off signal of holocene glacier fluctuations of blaisen lithostratigraphy sediment characteristics and radiocarbon dates from the study section indicate one period of glacier re advance between the late preboreal deglaciation of the inland ice sheet and 8660 100 yr b p a grey sand layer 56 57 cm below the surface is interpreted to be of fluvial colluvial origin and is radiocarbon dated to about 7700 yr b p at 48 cm below the surface a bluish grey sand silt layer is radiocarbon dated to 7590 12 yr b p 6560 6240 b c and interpreted to be glaciofluvial origin a minor glacier oscillation postdates 1130 70 yr b p 810 990 a d the medieval little ice age glacier advance of blaisen beyond its modern extent occurred after 1040 60 yr b p 960 1030 a d calculations of the modern and little ice age equilibrium line altitudes elas on hardangerjokulen suggest an ela depression of ca 130 m during the little ice age maximum