estimating the full scale flexural and compressive strength of first year sea ice sea ice salinity density and temperature data were used to develop new methods for determining the bulk brine volume and porosity of sea ice floes methods for estimating full thickness ice sheet strength based on large scale field tests are presented the relationships among bulk sea ice properties strain rate and strength are illustrated a new constitutive equation was developed for predicting the full thickness horizontal compressive strength c of first year sea ice as a function of the applied strain rate and bulk porosity in the form c b2e 1 n bm where parameters b2 n and m are about 2 7 103 3 and 1 respectively and e and b are the ice strain rate and ice floe bulk porosity of sea ice respectively an example of the first year sea ice indentation force against a 90 m wide structure is given estimating sea ice strength based on remote ice conductivity measurements is also discussed conceptually

climate and vegetation in southeastern australia respond to southern hemisphere insolation forcing in the late pliocene early pleistocene terrestrial climate responses to orbital forcing during the late pliocene early pleistocene are poorly understood particularly in the southern hemisphere but are important for determination of the timing of regional climate evolution early in the history of the glaciated quaternary world we present a pollen record from southeastern australia that shows marked cyclic change over some 280 000 yr straddling the pliocene pleistocene boundary rainforest communities responded to climate forcing primarily within the precession and eccentricity bands suggesting that major vegetation changes were driven directly by summer insolation rather than by obliquity dominated glacial cycles

direct and indirect evaluation of denudation rates in central italy abstract this paper presents the main results of a series of geomorphological studies aimed to the quantitative direct and indirect evaluation of denudation processes in central italy these studies which started in some sample areas since long ago were further deepened and extended to a wider number of drainage basins representative of a variety of morphostructural conditions the complex cause effect relationships among factors influencing both the morphogenesis and the plano altimetric configurations of drainage basins resulted in a large variability in the values of the denudation index tu which ranged from 200 to 2500 t km2 year very high values tu 10 000 t km2 year were obtained for small catchments belonging to the wider basins of ombrone river and tevere river where fast morphological modifications occur due to the action of surface running waters and gravity in the drainage basins affected by the most powerful denudation processes direct measurements of denudation were performed several monitoring stations were equipped with iron stakes and disks to record the local modifications of the topographic surface with time whereas some of these stations have been working continuously since 1993 some others have been running only periodically direct measurements pertinent to periods longer than a decade indicated that mean annual values of denudation range between 1 and 2 5 cm year for slopes affected by sharp edged and or rounded edged badlands higher denudation rates 3 4 cm year were obtained for shorter observation periods still higher rates were recorded for short periods at the gully bottom or in coincidence with mass movements before bench marks were turned up or damaged denudation processes are likely to occur discontinuously they show a step like trend with time and are triggered by rainfall events distributed over a number of consecutive days though not greatly intense particularly their amount should overcome the threshold of 60 mm per 5 consecutive days below this threshold the surface runoff does not seem to reach the power necessary to induce significant modifications of the topographic surface in the study area

long term behaviour of australian stable continental region scr faults abstract australia boasts arguably the richest late neogene to quaternary faulting record in stable continental region scr crust anywhere in the world variation in fault scarp length vertical displacement proximity to other faults and relationship to topography permits division of the continent according to fault character six onshore neotectonic domains are recognised with an additional offshore domain proposed by analogy with the eastern united states each domain relates to a distinct underlying crustal type and architecture broadly considered to represent cratonic non cratonic and extended environments in general greater topographic expression associated with faults occurring in extended crust relative to non extended crust suggests a higher rate of seismic activity in the former setting consistent with observations worldwide using the same reasoning non cratonic crust might be expected to have a higher rate of seismic activity than cratonic crust this distinction together with the variation in fault character between domains should be recognised in attempts to identify analogous systems worldwide a common characteristic of morphogenic earthquake occurrence in australia appears to be temporal clustering periods of earthquake activity comprising a finite number of large events are separated by much longer periods of seismic quiescence at the scale of a single fault and of proximal faults in several instances there is evidence for deformation at scales of several hundred kilometres switching on and off over the last several million years what is not clear from the limited palaeoseismological data available is whether successive active periods are comparable in terms of slip number of events magnitude of events etc regardless this apparent bimodal recurrence behaviour poses challenges for probabilistic seismic hazard assessment psha these rely on the simplifying assumption that large earthquake recurrence for long return periods is not random i e poissonian presently our ability to incorporate such time dependent models is limited by available data

sea ice ridging in the ross sea antarctica as compared with sites in the arctic at the end of the 1980 austral winter surface roughness measurements were made by laser profilometer during a series of flights over the ross sea pack ice the total track length was 2696 km and 4365 ridges were counted the frequency distribution of individual ridge heights was found to be well described by a negative exponential distribution no clear cut regional variation was noted in ridge heights the distribution of ridge frequencies per kilometer showed a strong positive skew with a modal value of 1 88 the most frequent ridging occurred off the east coast of victoria land comparisons with similar data sets from the arctic indicate that large ridges are significantly more likely in the arctic ocean than in the ross sea utilizing a reasonable model for the geometry of ridges estimates are made of the average thickness of a hypothetical continuous layer composed only of the deformed ice from ridges the noncoastal ross sea value of 0 09 m is less than half of the lowest comparable value from the arctic 0 20 m central beaufort sea where values in excess of 1 0 m have been observed in the shear zones north of greenland

geometric analysis of fold development in overthrust terranes abstract fault bend folding fault propagation folding and detachment or decollement folding are three distinct scenarios for fold thrust interaction in overthrust terranes simple kink hinge models are used to determine the geometric associations implicit in each scenario bedding maintains constant thickness in the models except in the forelimb of the fold the forelimb is allowed to thicken or thin without limit the models address individual folds and the calculated fold geometries are balanced structures each mode of fold thrust interaction has a distinct set of geometric relationships final fold geometry is adequate in itself to discern many fault bend folds this is not the case for fault propagation and detachment folds these two fold forms have very similar geometric relationships some knowledge of the nature of the underlying thrust or decollement zone is usually needed to distinguish between them the geometry of a fold is altered in a predictable fashion by transport through an upper ramp hinge and by fault parallel shearing of the structure the shearing results in a tighter fold whereas transport through the ramp hinge produces a broader fold the viability of the geometric analysis technique is demonstrated through its application to a pair of detachment folds from the canadian cordillera the geometric analysis is also used to evaluate cross sections through subsurface structures in an example from the turner valley oil field the analysis indicates how the interpretation should be altered so as to balance the cross section the analysis reveals hidden assumptions and specific inconsistencies in structural interpretations

style and intensity of late cenozoic deformation in the nagoorin basin eastern queensland australia and implications for the pattern of strain in an intraplate setting eastern australia was affected by late cenozoic intraplate deformation in response to far field stress transmitted from the plate boundaries but little is known about the intensity and pattern of this deformation we used recently surveyed two dimensional seismic reflection lines and aeromagnetic data and data from the recently released australian stress map to investigate the structure of the nagoorin basin in eastern queensland the western margin of the nagoorin beds was displaced by the boynedale fault which is a nnw striking sw dipping oblique strike slip reverse fault with a vertical throw of c 900 m and c 16 km sinistral displacement a significant part of this large sinistral displacement is interpreted to have occurred prior to late cenozoic time several low angle 30 thin skinned thrusts with a flat ramp geometry also displaced the nagoorin beds which are interpreted to have developed along detachment surfaces in oil shales and claystone the boynedale fault is a segment within longer nnw striking faults that include the north pine and west ipswich fault systems in eastern queensland these nnw striking faults are potentially active and may accommodate neotectonic thrust movement in response to the present day ne sw orientation of s results of this study in conjunction with previous information on sedimentary basins in eastern australia indicate that cenozoic contractional deformation is stronger at the continental margins possibly due to the presence of pre existing rift related structures

the sea ice thickness distribution in the northwestern weddell sea we present new data on distribution of snow and sea ice thicknesses in the northwestern weddell sea the data were obtained through direct measurements along 19 profiles each approximately 100 m long on 17 different floes located between 54 46 w and 59 64 s the overall probability density functions pdfs for ice thicknesses reflect the complex mixture of first second and multi year ice to be expected in the outflowing branch of the weddell gyre further differentiation of the data reveals four distinct thickness classes which reflect differences in the formation and subsequent histories of the ice encountered these classes i iv represent strongly deformed first year ice less deformed first and second year ice and deformed second or multi year ice respectively each of the classes is characterized by a specific set of quantities related to ice texture and surface snow characteristics and by distinct pdfs for snow and ice thicknesses in addition geometric surface and bottom roughness characteristics differ significantly for each of the floe classes

a parameterization of the ice ocean drag coefficient 1 a parameterization of the ice ocean drag coefficient cw was developed through partitioning the oceanic drag force into three components 1 form drag on the floe edge 2 form drag on the ridge keel and 3 skin friction on the ice bottom through these quantities cw was expressed as a function of observable sea ice geometric parameters sensitivity studies were carried out to investigate the influence of varying sea ice conditions on cw the results revealed that cw increases first and then decreases with increasing ice concentration a similar to the observations of the air ice drag coefficient and which is mainly attributed to the nonmonotonic variation of the form drag on the floe edge with ice concentration moreover the form drag on the floe edge is always the dominant component having a proportion of more than 60 in sea ice with a large aspect ratio draft length 1 100 indicating the necessity of including this term in sea ice dynamic models particularly for the marginal ice zone miz the form drag on the ridge keel becomes dominant only when the ridging intensity is extremely high depth spacing 1 20 additionally a large value of cw cannot be caused only by the inclusion of form drag terms but also by large skin friction over rough ice bottoms finally for typical situations in the miz with moderate ridging intensity the parameterization will underestimate cw by approximately 30 for a rough ice bottom and by over 80 for a smooth ice bottom if no form drags are considered

snow thickness profiling on antarctic sea ice with gpr rapid and accurate measurements with the potential to upscale needles to a haystack snow thickness on sea ice is a largely under sampled parameter yet of importance for the sea ice mass balance and for satellite based sea ice thickness estimates and thus our general understanding of global ice volume change traditional direct thickness measurements with meter sticks can provide accurate but only spot information referred to as needles due to their pinpoint focus and information while airborne and satellite remote sensing snow products referred to as the haystack have large uncertainties due to their scale we demonstrate the remarkable accuracy and applicability of ground penetrating radar gpr snow thickness measurements by comparing them with in situ meter stick data from two field campaigns to antarctica in late winter early spring the efficiency and millimeter to centimeter accuracy of gpr enables practitioners to acquire extensive semi regional data with the potential to upscale needles to the haystack and to potentially calibrate satellite remote sensing products that we confirm to derive roughly 30 of the in situ thickness we find the radar wave propagation velocity in snow to be rather constant 6 encouraging regional snow thickness surveys snow thinner than 10 cm is under the detection limit with the off the shelf gpr setup utilized in our study

sea ice and snow thickness and physical properties of an ice floe in the western weddell sea and their changes during spring warming helicopter borne and ground based electromagnetic em ice thickness and ruler stick snow thickness measurements as well as ice core analyses of ice temperature salinity and texture were performed over a 5 week observation period between november 27 2004 and january 2 2005 on an ice floe in the western weddell sea at approximately 67 s 55 w the study was part of the ice station polarstern ispol expedition of german research icebreaker r v polarstern investigating changes of physical biological and biogeochemical properties during the spring warming as a function of atmospheric and oceanic boundary conditions the ice floe was composed of fragments of thin and thick first year ice and thick second year ice with modal total thicknesses of 1 2 1 3 2 1 and 2 4 2 9 m respectively this included modal snow thicknesses of 0 2 0 5 m on first year ice and 0 75 m on second year ice during the observation period snow thickness decreased by less than 0 2 m there was hardly any ice thinning warming of snow and ice between 0 1 and 1 9 c resulted in decreased ice salinity and increased brine volume direct current dc geoelectric and electromagnetic em induction depth sounding were performed to study changes of electrical ice conductivity as a result of the observed ice warming bulk ice conductivity increased from to 37 to 97 ms m analysis of conductivity anisotropy showed that the horizontal ice conductivity changed from 9 to 70 ms m these conductivity changes have only negligible effects on the thickness retrieval from em measurements

the fire human and climate nexus in the sydney basin eastern australia it is widely believed that australian aborigines utilized fire to manage many landscapes however to what extent this use of fire impacted on australia s ecosystems remains uncertain the late pleistocene holocene fire history from three sites within the sydney basin gooches swamp lake baraba and kings waterhole were compared with archaeological and palaeoclimatic data the gooches swamp record appeared to be most influenced by climate and there was an abrupt increase in fire activity from the mid holocene perhaps associated with the onset of modern el nino dominated conditions the kings waterhole site also displayed an abrupt increase at this time however there was a marked decrease in charcoal from 3 ka similarly lake baraba displayed low levels of charcoal in the late holocene at both kings waterhole and lake baraba archaeological evidence suggests intensified human activity in the late holocene during this period of lower and less variable charcoal it is hence possible that aboriginal people strongly influenced fire activity in some areas of the sydney basin during the late holocene perhaps in response to the increased risk of large intense fires as an enso dominated climate became more prevalent the fire his tory within the sydney basin varies both temporally and spatially and therefore it is inappropriate to apply a single fire regime to the entire region for landscape management this work also has implications for future fire incidence associated with climatic variability under an enhanced greenhouse effect

relationship between sea ice freeboard and draft in the arctic basin and implications for ice thickness monitoring we have confirmed our earlier finding that the probability density function pdf of ice freeboard in the arctic ocean can be converted to a pdf of ice draft by applying a simple coordinate transformation based on the measured mean draft and mean elevation this applies in each of six 50 km sections north of greenland of joint airborne laser and submarine sonar profile obtained along nearly coincident tracks from the arctic basin north of greenland and tested for this study detailed differences in the shape of the pdf can be explained on the basis of snow load and can in principle be compensated by the use of a more sophisticated freeboard dependent transformation the measured density ratio r actually mean draft mean elevation ratio for each section was found to be consistent over all sections tested despite differences in the ice regime indicating that a single value of r might be used for measurements done in this season of the year the mean value r from all six sections is 7 89 on the assumption that all six values are drawn from the same population the standard deviation is 0 55 for a single 50 km section and thus 0 22 for 300 km of track in attempting to infer ice draft from laser measured freeboard we would therefore expect an accuracy of about 28 cm in 50 km of track if mean draft is about 4 m and about 11 cm in 300 km of track these accuracies are compatible with the resolution of predictions from numerical models a simple model for the variability of r with season and with mean ice thickness gives results in reasonable agreement with observations they show that although there is a large seasonal variability due to snow load there is a stable period from november to april when the variability is chiefly dependent on the mean ice thickness alone thus in principle r can be mapped over the arctic ocean as a basis for interpreting survey data better field data are needed on the seasonal and spatial variability of three key quantities area averaged snow load mean density of first year and multiyear ice including the effect of ridging with these two ice regimes and density of near surface water

sediment yield and erosion rate estimation in the mountain catchments of the camastra artificial reservoir southern italy a comparison between different empirical methods abstract the sedimentary budget assessment is an important topic for the scientific and social community because it is crucial to understand the dynamics of orogenic belts and cope with a number of practical problems such as soil conservation and sediment accumulation in reservoir sediment yield or denudation rate estimates in southern central italy are generally obtained either by applying simple empirical relationships based on the statistical regression between the geomorphic parameters of the drainage network and the suspended sediment yield measured at the drainage basins outlets or by using qualitative quantitative sediment delivery ratio or erosion models in this work we carry out a study of catchment dynamics and a sedimentary yield computation of several mountain catchments of the central western sector of the basilicata region southern italy which are located upstream of an artificial reservoir the sediment yield and erosion rate have been computed through both an indirect assessment of the suspended sediment yield based on the tu index mean annual suspension sediment yield and the application of the rusle and usped empirical methods the results obtained have been compared with the historical data of sediment accumulation measured in the artificial reservoir of the camastra dam where a detailed evaluation of the volumes of historical i e about 40 years sediment storage was collected the collected dataset represents a basic tool both for the investigation of the morpho dynamics of a typical mountain catchment of the mediterranean area and the evaluation of sediment budget related to fluvial and hillslope processes the 38 year long record of the sediment storage in the camastra artificial reservoir located at the outlet of the studied mountain catchments permits the validation of empirical relationships based on the geomorphic and climatic parameters of the drainage basin among the three different methods of sediment yield evaluation tu index rusle and usped the tu index showed the best prediction ability although usped erosion model also furnished a good estimation as also confirmed by other works the indirect estimation of sediment yield based on ciccacci s empirical relationships can represent a good proxy of short term denudation rates in the mediterranean areas with geological and geomorphological features similar to the study area but the use of empirical models with increasing complexity such as the usped erosion model can help to explore the spatial distribution of the sediment yield sectors of the drainage basin the erosion hot spots and the role of landslides in sediment mobilization and hillslope channel connectivity processes

observations of sea ice thickness surface roughness and ice motion in amundsen gulf 1 ice thickness and surface roughness measurements of first year fy sea ice were collected with a fix mounted helicopter borne electromagnetic hem laser system in amundsen gulf in april to may 2004 the modal ice thickness values are in good qualitative agreement with different ice types identified in synthetic aperture radar sar imagery and shown on ice charts produced by the canadian ice service modal ice thickness values which generally represent level ice thicknesses were about 2 0 m over landfast ice a large range of modal ice thicknesses was observed in the mobile ice region with values of about 0 2 m young ice in leads where there was high radar backscatter 0 6 m thin fy ice in the polynya where there was medium to high backscatter and about 1 1 1 9 m thick fy ice elsewhere high surface roughnesses are strongly associated with high radar backscatter in sar imagery and are observed in areas of large shear the ratio of the standard deviations of ice draft and averaged roughness in an area of landfast ice is in good agreement with the ratio of the standard deviations of ice draft and ice equivalent roughness expected from isostasy with constant level ice and snow thickness however the standard deviation of ice equivalent roughness may be significantly underestimated due to differences in snow thickness between level and deformed ice and limitations of the laser processing method modal ice plus snow thicknesses measured with the hem system are within the range of historical values measured at cape parry

space time variability of denudation rates at the catchment and hillslope scales on the tyrrhenian side of central italy studies on denudation rates can provide insight into the influence of climate change tectonics and human activities on landscape evolution research performed in central italy has shown considerable spatial variability of denudation rates in the major river basins these studies have focused mainly on the tyrrhenian side of the italian peninsula where plio pleistocene marine deposits filling nw se elongated sedimentary basins have been uplifted during the quaternary up to several hundreds of meters above present sea level small sub catchments developed on clays are affected by sharp and or rounded edged badlands i e calanchi and biancane representing denudation hot spots in the present day morphoclimatic framework in this paper we analyze the relationships between indirectly estimated denudation rates at the catchment scale and field monitoring data at the hillslope scale we attempt to better understand and quantify all hillslope processes that contribute to seasonal variability of denudation to help with predicting the net input from hot spots to the overall estimated sediment yield at the basin outlets at the hillslope scale we discuss in particular the variability of denudation rates at calanchi and biancane badlands as a function of their different morphoevolution

sea ice ridging in the eastern weddell sea in august 1986 sea ice ridge heights and spatial frequency in the eastern weddell sea were measured using a ship based acoustical sounder using a minimum ridge sail height of 0 75 m a total of 933 ridges were measured along a track length of 415 km the ridge frequency varied from 0 4 to 10 5 ridges km 1 the mean height of the ridges was found to be about 1 1 m regardless of the ridge frequency these results are compared to other ridging statistics from the ross sea and found to be similar comparison with arctic data however indicates that the height and frequency of the ridges are considerably less in the weddell sea than in the arctic whereas in the arctic the mean ridge height tends to increase with the ridge frequency we found that this was not the case in the weddell sea where the mean ridge height remained constant irrespective of the ridge frequency estimates of the contribution of deformed ice to the total ice thickness are generally low except for a single 53 km section where the ridge frequency increased by an order of magnitude this resulted in an increase in the equivalent mean ice thickness due to ridging from 0 04 m in the less deformed areas to 0 45 m in the highly deformed section these values were found to be consistent with values obtained from drilled profile lines during the same cruise

thickness and density of snow covered sea ice and hydrostatic equilibrium assumption from in situ measurements in fram strait the barents sea and the svalbard coast modern satellite measurements of sea ice thickness are based on altimeter measurements of the difference in elevation between the snow or ice surface and the local sea surface for retrieval of sea ice thickness it is assumed that the ice is in hydrostatic equilibrium and that the snow load on the ice and the density of the sea ice and sea water are known this study presents data from in situ sea ice thickness drillings and snow and ice density measurements from fram strait the barents sea and the svalbard coast in the european arctic the error in the altimetry ice thickness products is assessed based on the spatial variability of snow and ice density and snow thickness data ice thickness uncertainty related to snow depth was found to be 40 cm radar altimeter and 90 cm laser altimeter while uncertainty related to ice density is 25 cm for both techniques the assumption of hydrostatic equilibrium at the scales of the measurements 10 100 m was found to hold better in the case of level landfast ice near svalbard than for fram strait drift ice which consists of mixed ice types where the deviation between the calculated and measured ice thicknesses was on average 0 5 m

modeling soil erosion and river sediment yield for an intermountain drainage basin of the central apennines italy abstract the overall aim of this research was to investigate the spatial patterns of the soil erosion risk we focused on accelerated soil erosion processes in an italian central apennine intermountain watershed using modeling techniques implemented in a gis environment our thorough literature review revealed a gap in research on soil erosion processes in such forested intermountain watersheds to gain a better understanding of the soil erosion processes in such landscapes we proposed an integrated modeling approach applying a rusle model and a turbidity unit index the model outcomes were validated through measurements of lake sediment deposition our findings indicate a potential high soil erosion risk with 1 33 m t 1 yr 1 of annual sediment yield corresponding to an area specific sediment yield of 32 35 t ha 1 yr 1 the turano drainage basin belongs to the italian basins with the highest sediment discharge the outcomes of the rusle model showed that despite the diverse forms of forests that cover about 62 of the drainage basin area sizable plots of the investigated area are prone to soil erosion the validation of the model outcomes revealed that the tu index model performed significantly better than the rusle model with regard to sediment yield prediction accordingly we found that even though rill and interrill processes reach very alarming values rusle they are not the dominant sediment source within the turano watershed other geomorphological processes contributing to the watershed sediment yield for instance megarill gully bank and channel erosion and re entrainment of landslide sediments were very active in the study area if both models are used in a combined approach the amount of river load tu index as well as the relative spatial distribution of rill and interrill erosion processes rusle can be described with sufficient precision

estimating small scale snow depth and ice thickness from total freeboard for east antarctic sea ice abstract deriving the snow depth on antarctic sea ice is a key factor in estimating sea ice thickness distributions from space or airborne altimeters using a linear regression to model snow depth from observed total freeboard or the snow ice surface elevation relative to sea level is an efficient and promising method for the estimation of snow depth for instruments which only detect the uppermost surface of the sea ice conglomerate e g laser altimetry however the antarctic pack ice zone is subject to substantial variability due to synoptic scale weather forcing ice formation motion and melt undergo large spatio temporal variability throughout the year in this paper we estimate snow depth from total freeboard for the arise 2003 sipex 2007 and sipex ii 2012 research voyages to the east antarctic pack ice zone using in situ data we investigate variability in snow depth and show that for east antarctica relationships between snow depth and total freeboard vary between each voyage at a resolution of metres to tens of metres we show how regression based snow depth models track total freeboard and generally over estimate snow depth especially on highly deformed sea ice and at sites where ice freeboard makes a substantial contribution to total freeboard for a set of 3192 records we obtain an in situ mean snow depth of 0 21 m 0 19 m using a regression model derived from all in situ points we obtain the same mean with a slightly lower variability 0 16 m using voyage specific subsets of the data to derive regression models and estimate snow depth mean snow depths ranged from 0 19 m model derived from sipex observations to 0 25 m model derived from sipex ii observations while small these discrepancies impact ice thickness estimation using the assumption of hydrostatic equilibrium mean in situ ice thickness for all samples is 1 44 m 1 19 m using empirical models for snow depth ice thickness varies from 1 0 to 1 8 m with the best match to the in situ mean given when snow depth is derived using a snow depth model from all observations 1 53 m 1 55 m however mean values only tell part of the story when investigating the sea ice thickness distribution here we explicitly show how modelling snow depth and ice thickness based on a total freeboard signal compares with in situ observations this provides insight into the confidence we place in ice thickness distributions derived using a total freeboard signal and empirically derived models for snow depth

observations of sea ice ridging in the weddell sea sea ice surface topography data were obtained by helicopter borne laser profiling during the first finnish antarctic expedition finnarp 89 the measurements were made near the ice margin at about 73 s 27 w in the eastern weddell sea on december 31 1989 and january 1 1990 five transects ranging in length from 127 to 163 km and covering a total length of 724 km are analyzed with a lower cutoff of 0 91 m the overall ridge frequency was 8 4 ridges km and the average ridge height was 1 32 m the spatial variations in ridging were large for 36 individual 20 km segments the frequencies were 2 16 ridges km and the mean heights were 1 16 1 56 m the frequencies and mean heights were weakly correlated the distributions of the ridge heights followed the exponential distribution the spacings did not pass tests for either the exponential or the lognormal distribution but the latter was much closer in the 20 km segments the areally averaged thickness of ridged ice was 0 51 0 28 m ranging from 0 10 to 1 15 m the observed ridge size and frequency are greater than those known for the ross sea compared with the central arctic the weddell sea ridging frequencies are similar but the ridge heights are smaller possibly as a result of differences in snow accumulation

southeast australian late mesozoic and cenozoic denudation rates a test for late tertiary increases in continental denudation throughout the tertiary average rates of erosion of southeast australia have been uniformly low about 10 3 mm yr of surface lowering indicating that this part of the australian continent did not contribute to a rapid increase in ocean basin sedimentation over the past 15 or 20 m y somewhat higher mesozoic rates may be the result of minor tectonism but explanation for the generally low cenozoic and mesozoic erosion rates may be sought in the forest cover and general tectonic stability of southeast australia over this time period australia9s gradually increasing aridity climatic seasonally over the past 20 m y has apparently not resulted in higher average rates of erosion of the continent except perhaps in the very latest tertiary and quaternary

extensional basins in the tectonically bimodal central apennines fold thrust belt italy response to corner flow above a subducting slab in retrograde motion the apennines fold thrust belt has developed over the past 20 m y in response to southeastward retrograde migration of the adriatic trench in a region of ongoing subduction but little plate convergence the orogenic belt is characterized by a gently sloping southwestern flank in a state of regional extensional collapse and a steeply sloping northeastern flank in regional contraction in any given area in the central apennines the chronologies of thrusting and subsequent extension provide an estimate of the time required for attainment of high elevation 2 5 3 0 km the time between initial extension and eruption of local ultramafic lavas provides an estimate of the time required to collapse by regional crustal thinning these estimates suggest that the northeastern contractional flank of the range is rising at least twice as fast as the southwestern flank is collapsing we propose that the bimodal state of stress in the apennines is maintained by corner flow in the mantle wedge beneath the crest of the range

roughness variability of sea ice and snow cover thickness profiles in the ross amundsen and bellingshausen seas investigation of top and bottom surface roughness was carried out on snow and ice thickness profiles sampled on 57 floes in the ross amundsen and bellingshausen seas between may and september 1995 an objective classification scheme was used to group the studied sea ice floes according to the degree of deformation they had undergone different roughness criteria and methods were applied to the classified floes roughness variances and other properties such as fractal dimensions derived from fourier spectra depend critically on the deformational history of the floes under consideration the wavelet transform is presented as a new two dimensional method to find dominant structure lengths and at the same time localize them in the studied profiles finally air water and ice surface drag coefficients are calculated from the surface roughness characteristics air drag coefficients ranged between 1 1 and 1 7 103 and increased with increasingly deformed ice

contemporary versus long term denudation along a passive plate margin the role of extreme events short term contemporary and long term denudation rates were determined for the blue mountains plateau in the western sydney basin australia to explore the role of extreme events wildfires and catastrophic floods in landscape denudation along a passive plate margin contemporary denudation rates were reconstructed using 40 years of river sediment load data from the nattai catchment in the south west of the basin combined with an analysis of hillslope erosion following recent wildfires long term denudation rates 10 kyr 10 myr were determined from terrestrial cosmogenic nuclides apatite fission track thermochronology and post basalt flow valley incision contemporary denudation rates average several times lower than the long term average 5 5 4 mm kyr 1 versus 21 5 7 mm kyr 1 erosion of sediment following wildfires accounts for only a small proportion 5 of the contemporary rate most post fire sediment is stored on the lower slopes and valley floor with the amount transported to the river network dependent on rainfall run off conditions within the first few years following the fire historical catastrophic floods account for a much larger proportion 35 of the contemporary erosion rate and highlight the importance of these events in reworking stored material evidence for palaeofloods much larger than those experienced over the past 200 years suggests even greater sediment export potential mass movement on hillslopes along valleys incised into softer lithology appears to be a dominant erosion process that supplies substantial volumes of material to the valley floor it is possible that a combination of infrequent mass movement events and high fluvial discharge could account for a significant proportion of the discrepancy between the contemporary and long term denudation rates copyright 2006 john wiley sons ltd

the relation between arctic sea ice surface elevation and draft a case study using coincident auv sonar and airborne scanning laser 1 data are presented from a survey by airborne scanning laser profilometer and an auv mounted upward looking swath sonar in the spring beaufort sea the air snow surface elevation and water ice draft surfaces were mapped at 1 1 m resolution over a 300 300 m area data were separated into level and deformed ice fractions using the surface roughness of the sonar data the relation r d f between draft d and surface elevation f was then examined correlation between top and bottom surfaces was essentially zero at full resolution requiring averaging over patches of at least 11 m diameter to constrain the relation largely because of the significant error 15 cm of the laser instrument level ice points were concentrated in two core regions corresponding to level fy ice and refrozen leads with variations in r attributed primarily to positive snow thickness variability deformed ice displayed a more diffuse cloud with draft having a more important role in determining r because of wider deformed features underwater averaging over footprints similar to satellite altimeters showed the mean surface elevation typical of icesat to be stable with averaging scale with r 3 4 level and r 4 2 deformed the minimum elevation within a footprint characteristic reported for cryosat was less stable significantly overestimating r for level ice r 5 and deformed ice r 6 the mean draft difference between measurements and isostasy suggests 70 m as an isostatic length scale for level ice the isostatic scale for deformed ice appears to be longer than accessible with these data 300 m

pleistocene coastal stratigraphy sea level highstands and neotectonism of the southern australian passive continental margin a review located in a tectonically stable intraplate setting and in the far field of former ice sheets the southern australian passive continental margin represents a globally important region for quantifying sea level during pleistocene highstands the stratigraphical record of the southern australian margin is dominated by geographically extensive coastal barrier estuarine and peritidal landforms of bioclastic temperate carbonate affinity a function of regional aridity siliciclastic successions dominate the eastern australian coastline despite the generally high level of tectonic stability regional contrasts are evident in the elevation of pleistocene shoreline deposits that largely relate to pre quaternary geotectonic setting the most complete record of pleistocene highstand deposits occurs in the murray basin coorong coastal plain region and indicates that interglacial sea level highstands for at least the past 11 interglacials did not deviate by more than 6 m from present sea level the pleistocene marginal marine record of southern australia is dominantly represented by coastal successions deposited during marine oxygen isotope stages 5e and 7 equating with relative sea level maxima of 2 6 m and greater than 1 m above present sea level apsl respectively intertidal facies of late pleistocene interstadial successions rarely occur above present sea level the most reliable record of glacio eustatic ice equivalent sea level is registered on coastlines developed on stable precambrian cratons such as the gawler craton eyre peninsula where a consistent elevation of 2 m apsl is registered for over 500 km for the last interglacial shoreline 125 ka copyright 2002 john wiley sons ltd

controls on post mid cretaceous landscape evolution in the southeastern highlands of australia insights from numerical surface process models the tectonic and geomorphic evolution of the southeastern australian highlands has been a subject of controversy among geophysicists geologists and geomorphologists for several decades we employ a numerical surface process model that includes long range fluvial transport hillslope diffusion and landsliding in order to quantitatively assess the tectonic lithological and structural controls on the landscape evolution and denudation history of se australia we constrain fluvial erosion parameters for our model by fitting river profiles rockfall and landsliding are the most important processes controlling the concentration of erosion in river valleys we therefore model hillslope evolution using a very low diffusion coefficient and a threshold slope for landsliding the initial prebreakup topography of the highlands provides a fundamental control on their subsequent evolution together with the style and rate of fluvial incision secondary controls are exerted by lateral variations in lithology and local tectonic uplift along faults our modeling results indicate that 1 the observed highlands morphology requires that the drainage divide was established at its present location prior to opening of the tasman sea whether the divide is inherited from paleozoic orogeny or resulted from mesozoic syn rift uplift cannot be established however 2 in contrast to traditional interpretations escarpment retreat does not appear to be the fundamental process eroding the highlands and 3 the observed barbed river drainage may be imprinted as a result of lithological variation it does not necessarily evolve through capture the driving mechanism that is most consistent with the inferred uplift pattern of the southeastern highlands appears to be magmatic underplating

flexural uplift of rift flanks due to mechanical unloading of the lithosphere during extension we suggest that the uplift of rift flanks results from mechanical unloading of the lithosphere during extension and consequent isostatic rebound this mechanism is presented as an alternative to explanations for rift flank uplift involving thermal or dynamic processes and magmatic thickening of the crust our hypothesis is based on two critical concepts first the lithosphere retains finite mechanical strength or flexural rigidity during extension second isostatic rebound uplift of the lithosphere follows when the kinematics of extension produces a surface topographic depression that is deeper than the level to which the surface of the extended lithosphere would subside assuming local isostatic compensation we develop and analyze two kinematic models for instantaneous extension of the lithosphere to show that flexural rebound is a viable explanation for the uplift of rift flanks we first investigate the isostatic consequences of finite simple slip on an initially planar dipping normal fault cutting the entire lithosphere when the lithosphere retains flexural rigidity during extension the topography resulting from this model resembles a half graben and the footwall rift flank is flexurally uplifted this simple normal faulting model explains free air gravity anomalies and topography observed at rift flanks in oceanic lithosphere such as broken ridge in the eastern indian ocean the caroline ridges sorol trough in the western equatorial pacific and the coriolis trough behind the new hebrides island arc we then investigate a general kinematic model for lithospheric extension where simple slip on a surface of arbitrary shape is accompanied by pure shear extension in the upper and lower plates when the simple slip component is not zero or the distribution of pure shear in the upper and lower plates is not identical the surface of slip can be regarded as a detachment by simplification our general model accounts for pure shear extension of the lithosphere that is uniform with depth in this case detachments have no meaning in the geologic sense however the kinematics of depth independent pure shear may nevertheless be described in terms of a surface which we term a kinematic reference surface at some depth in the lithosphere we speculate that the depth of this surface may be rheologically controlled the magnitude of rift flank uplift by flexure depends critically on the depth of this reference surface in contrast if local isostasy is assumed when the lithosphere undergoes a given amount of depth independent pure shear the resulting topography will be the same regardless of how the kinematics of that extension are formulated the basin and rift flank topography and free air gravity anomaly over young continental rifts such as the rhine graben can be satisfied using our general extensional model with a small amount 5 km of extension along a listric shaped detachment soling into the crust mantle boundary because the flexural rebound mechanism explains the observed topography and gravity anomaly over both oceanic and continental extensional domains we suggest that rheological differences between the two lithospheric types may not be important in their overall response to extension

top bottom multisensor remote sensing of arctic sea ice the arctic sea ice cover has been studied using near simultaneous observations by passive and active synthetic aperture radar sar microwave sensors upward looking and sidescan sonars a lidar profilometer and an infrared sensor data from two aircraft and a submarine over an approximately 100 km track of central arctic sea ice were registered and analyzed to evaluate the characteristics of the ice cover and the utility of each sensor in ice studies the results of comparative and correlation analyses are as follows the probability density functions of ice draft from sonar and elevation from lidar were found to be almost identical when isostasy is taken into account this result suggests that the basic ice thickness distribution can be derived from the surface topography measurements alone reasonable correlation was found between sar backscatter and ice draft or elevation especially when scales were adjusted such that 15 20 sar pixels were averaged however surface roughness derived directly from standard deviations in the lidar elevation data was found to be poorly correlated to the sar backscatter these results indicate that the sar values are affected more by scattering from the ice than from the snow covered surface the active and passive microwave sensors are shown to generally complement each other as the two sensors are especially sensitive to different physical properties of the sea ice undeformed first year ice showed low backscatter values but high brightness temperatures while some multiyear ice showed high backscatter values and low brightness temperature however surfaces identified as multiyear ice by the passive system have a large spread in the unaveraged sar backscatter indicating limitations when using a one channel sar for ice type identification at the highest resolution also ridged ice identified by sonar and sar data covers a large range of passive microwave emissivity suggesting considerable variability in the age and salinity of this type of ice significant variations about 0 11 in the minimum emissivity of consolidated multiyear ice are observed in different regions of the arctic using the high resolution 30 m passive microwave data this suggests that regional variations in texture and scattering characteristics of multiyear ice in the arctic are present likely influenced by different histories of formation of the ice in different regions

cenozoic landscape development in the blue mountains se australia lithological and tectonic controls on rifted margin morphology abstract cenozoic landscape development on the southeastern australian rifted margin as recorded by mid tertiary basalt flows that preserve ancient landforms is generally considered to be very slow eocene miocene basalts of the southeastern australian highlands flowed down paleovalleys indicating that landscape dissection was already well under way at the time of their eruption within the deeply incised blue mountains however miocene basalts cap relatively flat hilltops suggesting that most incision postdates their emplacement we have studied the controls on these apparent lateral variations in cenozoic landscape development using both field observations and numerical models we have mapped the blue mountains basalts in detail to reconstruct the miocene landscape and to quantify both the amount of subbasalt relief and postbasalt incision rates new geochemical and k ar geochronological data indicate that most of the blue mountains basalts were derived from a common magma source and were erupted i

sea ice thickness from airborne laser altimetry over the arctic ocean north of greenland 1 we present a new method to measure ice thickness of polar sea ice freeboard heights using airborne laser altimetry combined with a precise geoid model giving estimates of thickness of ice through isostatic equilibrium assumptions in the paper we analyze a number of flights from the polar sea off northern greenland and estimate accuracies of the estimated freeboard values to be at a 13 cm level corresponding to about 1 m in absolute thickness

thickness and surface properties of different sea ice regimes within the arctic trans polar drift data from summers 2001 2004 and 2007 1 large scale sea ice thickness and surface property data were obtained in three summers and in three different sea ice regimes in the arctic trans polar drift tpd by means of helicopter electromagnetic sounding distribution functions p of sea ice thickness and of the height spacing and density of sails were analyzed to characterize ice regimes of different ages and deformations results suggest that modal ice thickness is affected by the age of a sea ice regime and that the degree of deformation is represented by the shape of p mean thickness changes with both age and deformation standard error calculations showed that representative mean and modal thickness could be obtained with transect lengths of 15 km and 50 km respectively in less deformed ice regimes such as those around the north pole in heavier deformed ice regimes closer to greenland 100 km transects were necessary for mean thickness determination and a representative modal thickness could not be obtained at all mean sail height did not differ between ice regimes whereas sail density increased with the degree of deformation furthermore the fraction of level ice open melt ponds and open water along the transects were determined although overall ice thickness in the central tpd was 50 thinner in 2007 than in 2001 first year ice fyi was not significantly thinner in 2007 than fyi in 2001 with a decrease of only 0 3 m thinner fyi in 2007 only occurred close to the sea ice edge where open water covered more than 10 of the surface melt pond coverage retrieved from laser measurements was 15 in both the 2004 myi regime and the 2007 fyi regime

modelling the spread of oil under fast sea ice using three dimensional multibeam sonar data 1 a substantial portion of the world s remaining oil and gas reserves are found in the arctic exploration pressure will intensify as sea ice thinning and retreat continue and the subsequent production could involve spills or blowouts under various kinds of sea ice existing models for the spread of oil under ice are inadequate because they are unable to replicate the complexity or uniqueness of different ice regimes through the novel combination of 3 d under ice imagery from an autonomous under water vehicle auv and oil trajectory modelling we demonstrate that it is possible to overcome these deficiencies results suggest that we are presently underestimating the spread of oil under sea ice by an order of magnitude this is an important result with wide ranging ramifications as it suggests that our present ability to contain and recover oil under ice is limited

soil production on a retreating escarpment in southeastern australia the functional dependence of bedrock conversion to soil on the overlying soil depth the soil production function has been widely recognized as essential to understanding landscape evolution but was quantified only recently here we report soil production rates for the first time at the base of a retreating escarpment on the soil mantled hilly slopes in the upper bega valley southeastern australia concentrations of 10 be and 26 al in bedrock from the base of the soil column show that soil production rates decline exponentially with increasing soil depth these data define a soil production function with a maximum soil production rate of 53 m m y under no soil mantle and a minimum of 7 m m y under 100 cm of soil thus constraining landscape evolution rates subsequent to escarpment retreat the form of this function is supported by an inverse linear relationship between topographic curvature and soil depth that also suggests that simple creep does not adequately characterize the hillslope processes spatial variation of soil production shows a landscape out of dynamic equilibrium possibly in response to the propagation of the escarpment through the field area within the past few million years in addition we present a method that tests the assumption of locally constant soil depth and lowering rates using concentrations of 10 be and 26 al on the surfaces of emergent tors

episodic post rift deformation in the south eastern australian passive margin evidence from the lapstone structural complex identifying the influence of neotectonics on the morphology of elevated passive margins is complicated in that major morpho structural patterns might plausibly be explained by processes related to late mesozoic to early cenozoic rifting and or differential erosion induced by cenozoic epeirogenic uplift the proportional contribution of each process can vary from continent to continent and potentially even within the same passive margin in the passive margin setting of the southeast australian highlands the documented occurrence of neotectonic deformation is rare and accordingly its role in landscape evolution is difficult to establish the results of investigations within the lapstone structural complex which forms the eastern range front of the blue mountains plateau provide evidence for two periods of cenozoic neotectonic uplift in this part of the highlands the first demonstrated by seismic and structural evidence is suggested to have occurred in the paleogene and is thus unrelated to cretaceous rifting the second period demonstrated by evidence from the kurrajong fault presented herein suggests that uplift occurred in both the mio pliocene and the middle pleistocene the cumulative neogene and younger uplift of 15 m determined for the kurrajong fault is less than 10 of the 130 m of total measured throw across the fault the apparently minor contribution of neotectonism to the current elevation of the blue mountains plateau supports a predominantly erosional exhumation origin for the topographic relief at the plateau s eastern edge this finding contrasts with evidence from fault complexes associated with similar topographic relief elsewhere in the south eastern highlands indicating that present day topography cannot be directly related to relief generated by neogene and younger uplift even from relatively closely spaced 150 km structures within the same passive margin these findings have implications for understanding the spatio temporal variability of post rift faulting in continental passive margin settings and the evolution of landscapes therein commonwealth of australia earth surface processes and landforms 2014 john wiley sons ltd

a new procedure for gridding elevation and stream line data with automatic removal of spurious pits abstract a morphological approach to the interpolation of regular grid digital elevation models dems from surface specific elevation data points and selected stream lines is described the approach has given rise to a computationally efficient interpolation procedure which couples the minimization of a terrain specific roughness penalty with an automatic drainage enforcement algorithm the drainage enforcement algorithm removes spurious sinks or pits yielding dems which may be used to advantage in hydrological process studies the drainage enforcement algorithm has also been found to significantly increase the accuracy of dems interpolated from sparse but well chosen surface specific elevation data moreover it facilitates the detection of errors in elevation data that would not be detected by more conventional statistical means and forms a sound physical basis for cartographic generalization

holocene hydrologic variability in temperate southeastern australia an example from lake george new south wales lake george is one of the largest freshwater lakes in australia when full and provides one of the most complete records of quaternary sedimentation in the southeastern part of the continent the lake is currently ephemeral but sediments within the basin preserve evidence of multiple permanent and dry lake conditions in the past we present an optically stimulated luminescence osl chronology of recent lake shoreline sediments in order to reconstruct holocene hydrologic variability at lake george providing past climatic context for the presently ephemeral lake conditions the osl chronology indicates three distinct periods of permanent lake conditions up to 15 18 m depth over the holocene period at approximately 10 8 6 2 4 and 0 7 0 3 ka with lower lake levels occurring in between those events there appears to be a trend towards lake regression over this period despite relatively recent high lake levels the chronology is broadly synchronous with comparable records of holocene climatic variability across southeastern australia we also investigate the intrinsic luminescence characteristics of different sediment types as diagnostic tools but these appear not to be appropriate in this context or form

comparison of thermoluminescence and radiocarbon age determinations from late pleistocene alluvial deposits near sydney australia abstract radiocarbon and thermoluminescence tl age determinations have been obtained for a large pleistocene alluvial terrace on the nepean river near sydney new south wales australia the deposit was laid down by a braided river system prior to the last glacial maximum six thoroughly pretreated samples of charcoal and degraded wood buried within gravels at the base of the terrace yielded apparent 14 c ages of 37 000 42 000 yr b p these compare favorably with four tl determinations that gave apparent ages of 41 000 47 000 yr b p for the same deposit adjustment of the 14 c ages to take geomagnetic effects into account further improves the correlation between these two independent dating techniques in addition 14 c and tl correctly identified a reworked portion of the fine grained alluvial overburden as being substantially younger than the main body of the terrace these results augur well for the usefulness of tl age determinations of certain alluvial deposits

morphology of sea ice pressure ridges in the northwestern weddell sea in winter altimeter during winter weddell outflow study with the german r v polarstern in 2006 an optimal cutoff height of 0 62 m derived from the best fits between the measured and theoretical ridge height and spacing distributions was first used to separate pressure ridges from other sea ice surface undulations it was found that the measured ridge height distribution was well modeled by a negative exponential function and the ridge spacing distribution by a lognormal function next based on the ridging intensity ri the ratio of mean ridge sail height to mean spacing all profiles were clustered into three regimes by an improved k means clustering algorithm ri 0 01 0 01 0 026 denoted as c1 c 2 and c3 respectively mean and standard deviation of sail height was 0 99 0 07 m in regime c1 1 12 0 06 m in c2 and 1 17 0 04 m in c3 respectively while the mean spacings and standard deviations were 232 240 m 54 20 m and 31 5 6 m these three ice regimes coincided closely with distinct sea ice regions identified in a satellite radar image where c1 corresponded to the broken ice in the marginal ice zone and level ice formed in the larsen polynya c2 corresponded to the deformed first and second year ice formed by dynamic action in the center of the study region and c3 corresponded to heavily deformed ice in the outflowing branch of the weddell gyre the results of our analysis showed that the relationship between the mean ridge height and frequency was well modeled by a logarithmic function with a correlation coefficient of 0 8 although such correlation was weaker when considering each regime individually the measured ridge height and frequency were both greater than those reported by others for the ross sea compared with reported values for other parts of the antarctic the present ridge heights were greater but the ridge frequencies and ridging intensities were smaller than the most extreme of them meanwhile average thickness of ridged ice in our study region was significantly larger than that of the coastal ross sea showing the importance of deformation and ice age for ice conditions in the northwestern weddell sea

atmospheric form drag coefficients over arctic sea ice using remotely sensed ice topography data spring 2009 2015 sea ice topography significantly impacts turbulent energy momentum exchange e g atmospheric wind drag over arctic sea ice unfortunately observational estimates of this contribution to atmospheric drag variability are spatially and temporally limited here we present new estimates of the neutral atmospheric form drag coefficient over arctic sea ice in early spring using high resolution airborne topographic mapper elevation data from nasa s operation icebridge mission we utilize a new three dimensional ice topography data set and combine this with an existing parameterization scheme linking surface feature height and spacing to form drag to be consistent with previous studies investigating form drag we compare these results with those produced using a new linear profiling topography data set the form drag coefficient from surface feature variability shows lower values 0 5 1 10 3 in the more deformed ice regimes of the central arctic north of greenland and the canadian archipelago which increase with coastline proximity the results show moderate interannual variability including a strong increase in the form drag coefficient from 2013 to 2014 2015 north of the canadian archipelago the form drag coefficient estimates are extrapolated across the arctic with advanced scatterometer satellite radar backscatter data further highlighting the regional interannual drag coefficient variability finally we combine the results with existing parameterizations of form drag from floe edges a function of ice concentration and skin drag to produce to our knowledge the first pan arctic estimates of the total neutral atmospheric drag coefficient in early spring from 2009 to 2015

effective rheology across the fragmentation transition for sea ice and ice shelves funding was provided by the nerc grant ne p011365 1 calving laws for ice sheet models calismo data files for the plots are found at https doi org 10 5285 76d7d3ca 7b83 4bb0 aae5 a8e92c7da5b0

late quaternary erosion in southeastern australia a field example using cosmogenic nuclides late quaternary rates of apparent soil production bedrock incision and average erosion are determined for the southeastern highlands of australia using in situ produced cosmogenic nuclide concentrations of 10 be and 26 al apparent soil production rates define a steep inverse exponential function of soil depth with a maximum of 143 m ma 1 under zero soil depth there were no observed soil depths between about 25 cm and zero however such that the maximum observed rate is about 50 m ma 1 the bredbo river catchment average erosion rate is 157 1mm a 1 and is similar to the average hillslope erosion rate of 167 1mm a 1 bedrock incision rates average 9 mma 1 and suggest that the higher rates of hillslope erosion may be in response to a pulse of incision perhaps generated by knickpoint propagation bedrock erosion rates inferred froma tor profile average 3 8 mma 1 with higher rates on other more weathered tor tops an aboveground tor profile of nuclide concentrations is consistent with a simple model of rapid stripping of the surrounding saprolite supporting the view that at least one episodic period of increased denudation has affected the landscape evolution of the highlands we test this hypothesis by using a simple landscape evolution model to reasonably predict the spatial variation of soil depth as well as the emergence of tors r 2001 elsevier science ltd and inqua all rights reserved

an assessment of state of the art mean sea surface and geoid models of the arctic ocean implications for sea ice freeboard retrieval state of the art arctic ocean mean sea surface mss models and global geoid models ggms are used to support sea ice freeboard estimation from satellite altimeters as well as in oceanographic studies such as mapping sea level anomalies and mean dynamic ocean topography however errors in a given model in the high frequency domain primarily due to unresolved gravity features can result in errors in the estimated along track freeboard these errors are exacerbated in areas with a sparse lead distribution in consolidated ice pack conditions additionally model errors can impact ocean geostrophic currents derived from satellite altimeter data while remaining biases in these models may impact longer term multi sensor oceanographic time series of sea level change in the arctic this study focuses on an assessment of five state of the art arctic mss models ucl13 04 dtu15 13 10 and a commonly used ggm egm2008 we describe errors due to unresolved gravity features inter satellite biases and remaining satellite orbit errors and their impact on the derivation of sea ice freeboard the latest mss models incorporating cryosat 2 sea surface height measurements show improved definition of gravity features such as the gakkel ridge the standard deviation between models ranges 0 03 0 25 m the impact of remaining mss ggm errors on freeboard retrieval can reach several decimeters in parts of the arctic while the maximum observed freeboard difference found in the central arctic was 0 59 m ucl13 mss minus egm2008 ggm the standard deviation in freeboard differences is 0 03 0 06 m

in situ and remote sensing signature of meddies east of the mid atlantic ridge 1 mediterranean water eddies meddies are thought to play an important climatic role nevertheless their dynamics are not sufficiently known because of difficulties encountered in their observation though propagating below the main thermocline a number of pieces of evidence of sea surface manifestation of meddies are collected the present work is based on joint in situ and altimetry data analyses to prove that the meddies can be followed with remote sensing data for long periods of time the in situ observations are based on data from an oceanographic cruise which crossed three meddies and reanalysis of historical data sets including rafos floats paths suggested methodology permitted us to obtain uninterrupted tracks for several meddies for a period from several months to more than 2 years it was found that the dynamically calm region to the north of the azores current presents favorable conditions for meddy tracking the meddy surface signal may become shattered and difficult to follow during interaction with a strong dynamic structures the azores current surface vortexes or peaking topography theoretical considerations support the observations and lead to the conclusion that the dynamic signature of meddies at the sea surface is an intrinsic property of meddy dynamics

drag measurements for first year sea ice over a shallow sea for a free drift case a method is developed for simultaneously determining air ca and water cw drag coefficients by solving the vertically integrated stress balance equation for sea ice the method allows the algebraic determination of ca and cw from measurements of relative wind and relative current at single reference levels from estimates of the densities of all three fluids and ice thickness and from estimates of the accelerations caused by the nonsurface stress terms derived from position measurements the method treats the ice as a natural drag plate and therefore includes contributions from both skin and form drag one shortcoming of the technique is that if the relative wind and current are colinear then only the ratio of ca and cw can be determined another is that the accelerations caused by other forces need to be independently determined an experiment was conducted on a single floe in the eastern bering sea over the continental shelf during march 1981 the site was about 80 km from the ice edge and was occupied for approximately 3 days following the passage of a storm which had broken the pack into 10 20 m diameter floes both profile and slab inversion estimates of drag were made from the current meter and anemometer measurements at the site ca at 3 m was 4 55 10 3 by the profile method compared to 3 63 4 39 10 3 for slab depending on assumptions cw at 1 1 m by profile was 24 2 10 3 compared to 18 3 22 0 10 3 for slab the two methods gave results which were not statistically separable and which were among the highest drags observed for sea ice the instantaneous stress balance on the floe included contributions from material acceleration coriolis force the two surface stresses and sea surface tilt relative to mean current and tide

ocean waves across the arctic attenuation due to dissipation dominates over scattering for periods longer than 19 s the poorly understood attenuation of surface waves in sea ice is generally attributed to the combination of scattering and dissipation scattering and dissipation have very different effects on the directional and temporal distribution of wave energy making it possible to better understand their relative importance by analysis of swell directional spreading and arrival times here we compare results of a spectral wave model using adjustable scattering and dissipation attenuation formulations with wave measurements far inside the ice pack in this case scattering plays a negligible role in the attenuation of long swells specifically scattering dominated attenuation would produce directional wave spectra much broader than the ones recorded and swell events arriving later and lasting much longer than observed details of the dissipation process remain uncertain average dissipation rates are consistent with creep effects but are 12 times those expected for a laminar boundary layer under a smooth solid ice plate

on the uncertainty of sea ice isostasy during late winter 2007 coincident measurements of sea ice were collected using various sensors at an ice camp in the beaufort sea canadian arctic analysis of the archived data provides new insight into sea ice isostasy and its related r factor through case studies at three scales using different combinations of snow and ice thickness components at the smallest scale 1m point scale isostasy is not expected so we calculate a residual and define this as zjey to describe vertical displacement due to deformation from 1 to 10m length scales we explore traditional isostasy and identify a specific sequence of thickness calculations which minimize freeboard and elevation uncertainty an effective solution exists when the r factor is allowed to vary ranging from 2 to 12 with mean of 5 17 mode of 5 88 and skewed distribution at regional scales underwater airborne and spaceborne platforms are always missing thickness variables from either above or below sea level for such situations realistic agreement is found by applying small scale skewed ranges for the r factor these findings encourage a broader isostasy solution as a function of potential energy and length scale overall results add insight to data collection strategies and metadata characteristics of different thickness products

earthquake environmental effects produced by the mw 6 1 20th may 2016 petermann earthquake australia abstract earthquake environmental effects eees identified in the source region of the 20th may 2016 intraplate moment magnitude mw 6 1 petermann earthquake in central australia are described and classified using the environmental seismic intensity esi 07 scale eees include surface rupture ground fissures and cracks vegetation damage rockfalls and displaced jumped bedrock fragments the maximum esi intensity derived from eees is x consistent with previous observations from some moderate mw crustal earthquakes maximum esi isoseismals correlate with the location of the surface rupture rather than epicentre area due to the dipping geometry of the reverse source fault esi isoseismals encompass a larger area of the hanging wall than the footwall indicating stronger ground motions on the hanging wall due to increased proximity to the rupture source and ground motion amplification effects the maximum areal extent of secondary seismic shaking induced eees 300 km2 is significantly smaller than expected using the published esi 07 scale approx 5000 km2 this relates to the low topographic relief and relatively homogeneous bedrock geology of the study region which i reduced the potential for site response amplification of strong ground motions and ii reduced the susceptibility of the landscape to eee such as landsliding and liquefaction erosional degradation of the observed eee features and decreasing confidence with which they can be uniquely attributed to a seismic origin with increasing time since the earthquake highlight challenges in using many of the natural features observed herein to characterise the locations and attributes of paleo earthquakes

ice properties in the greenland and barents seas during summer resultats d analyse de carotte de glace de mer dans l arctique europeen les proprietes de la glace sont mises en rapport avec les conditions generales de la distribution de glace leur epaisseur et leur relief dans la zone exploree interpretation de la salinite sur les glaces de premiere annee et pluri annuelles

roughness of weddell sea ice and estimates of the air ice drag coefficient the roughness of a sheet of sea ice encodes its deformational history and determines its aerodynamic coupling with the overlying air and underlying water here we report snow surface ice surface and ice underside roughness computed from 47 surface elevation profiles collected during a transect of the weddell sea the roughness for each surface parameterized as the standard deviation of the surface elevation segregates according to whether or not a floe has been deformed deformed ice has greater roughness than undeformed ice regardless of deformational history the underside roughness is almost always greater than the snow surface and ice surface roughnesses which are nearly equal roughness spectra for all three surfaces and for both deformed and undeformed ice roll off roughly as k 1 when the wavenumber k is between 0 1 and 3 rad m 1 the snow surface and underside spectra roll off somewhat faster than k 1 and the ice surface spectra roll off somewhat slower than k 1 both top and underside arctic ice roughness spectra on the other hand have been reported to roll off faster than k 2 we speculate that the excess spectral intensity at high wavenumbers in the antarctic ice surface spectra results from the small scale roughness that the ice sheet had on consolidation this excess high wavenumber spectral intensity persists in the ice surface spectra of second year ice evidently once formed the ice surface remains unchanged on the microscale until the entire ice sheet melts with a remote measurement of roughness we should be able to decide whether an ice floe is deformed or undeformed our spectral analysis hints that remote sensing may also be able to differentiate between first year and second year ice from the snow surface spectra we compute a roughness scale that parameterizes the air ice momentum coupling and lets us estimate the neutral stability drag coefficient referenced to a height of 10 m cdn10 typical cdn10 values are 1 1 1 4 10 3 over undeformed ice and 1 3 1 8 10 3 over deformed ice

arctic ocean gravity geoid and sea ice freeboard heights from icesat and grace 1 icesat laser measurements provide a high resolution mapping of the sea ice surface of the arctic ocean which can be inverted to determine gravity anomalies and sea ice freeboard heights by a lowest level filtering scheme in this paper we use updated terrestrial gravity data from the arctic gravity project in combination with grace gravity field models to derive an improved arctic geoid model this model is then used to convert icesat measurements to sea ice freeboard heights with a coarse lowest level surface method the derived freeboard heights show a good qualitative agreement to the coverage of multi year sea ice however comparison to an airborne lidar underflight north of greenland shows that the lowest level filtering scheme may introduce a bias we finally use the icesat and grace results to derive new gravity anomalies by fourier inversion the satellite only gravity field shows all major tectonic features of the arctic ocean and has an accuracy of 6 mgal compared to recent airborne gravity data illustrating the usefulness of icesat data for gravity field determination

assessment of land degradation susceptibility by scenario analysis a case study in southern tuscany italy abstract in the mediterranean area land degradation phenomena are becoming more and more important due to future climate change and increasing climate variability as highlighted in recent global assessment projects such as the millennium ecosystem assessment or the dialogue on water and climate thus there is consistent evidence that extreme events such as droughts and floods are more frequent than before on the other hand the mediterranean area is strongly influenced by human activities such as cultivation over hundreds of years however in the last decades the cultivation methods and techniques are subject to profound changes such as mechanization use of fertilizers and pesticides remodellation of entire hillslopes etc this particular situation leads to and aggravates the existing stress on land resources as a result land degradation and soil erosion phenomena are leading to decreasing soil productivity or the loss of fertile top soil and related water quality and quantity issues the centre for soil erosion studies cres in grosseto tuscany recently started a study to identify and monitor changes of land use in southern tuscany italy the aim of this study is to assess land degradation sensitivity by scenario analysis as a proxi for land degradation surface wash erosion processes such as rill and interill erosion processes are chosen these present day processes are identified by aerial photo interpretation and subsequently modelled with a simple rusle approach on a monthly basis in this study boundary conditions such as future precipitation were taken from the a2 future climate scenario published by the international panel on climate change ipcc special report on emission scenarios sres moreover current land use was identified from aerial photographs and future land use scenarios were developed considering ecological and socio economical issues for present day conditions of the test area subsequently the different climate and land use scenarios were analysed to study soil erosion susceptibility on the landscape scale the study shows that even with a decline in precipitation volume until 2070 in some months higher erosion rates occur due to higher rainfall erosivity furthermore land use changes play an important role for soil erosion susceptibility as shown the various scenarios can effectively reduce or enhance soil erosion

formation uplift and dissection of planation surfaces at passive continental margins a new approach the usefulness of large scale low relief high level landscapes as markers of uplift events has become a subject of disagreement among geomorphologists we argue that the formation of low relief surfaces over areas of large extent and cutting across bedrock of different age and resistance must have been guided by distinct base levels in the absence of other options the most likely base level is sea level we have analysed west greenland landscapes in a recent study by combining the cooling history from apatite fission track analysis afta data with the denudation history from landscape analysis and the stratigraphic record an important difference between our approach and that of classical geomorphology is that we now have the ability to document when thick sections of rocks have been deposited and then removed the present day high level plateau in west greenland is the remnant of a planation surface that was formed by denudation that lasted c 20 million years during which up to 1 km of cover was removed after maximum burial at the eocene oligocene transition here we present additional afta data to show that the planation surface is the end product of cenozoic denudation even in basement areas and argue that phanerozoic sediments most likely of cretaceous palaeogene age must have been present prior to denudation the planation surface was offset by reactivated faults and uplifted to present day altitudes of up to 2 km the uplift occurred in two late neogene phases that caused incision of valleys below the planation surface and their subsequent uplift we therefore find that the elevated and deeply dissected plateau is evidence of episodic post rift uplift that took place millions of years after cessation of sea floor spreading west of greenland we suggest that other margins with similar morphology may also be characterized by episodic post rift uplift unrelated to the processes of rifting and continental separation rather than being permanently uplifted since the time of rifting as is commonly assumed copyright 2009 john wiley sons ltd

comparison of the sea ice thickness distribution in the lincoln sea and adjacent arctic ocean in 2004 and 2005 results of helicopter borne electromagnetic measurements of total ice plus snow sea ice thickness performed in may 2004 and 2005 in the lincoln sea and adjacent arctic ocean up to 868 n are presented thickness distributions south of 848 n are dominated by multi year ice with modal thicknesses of 3 9 m in 2004 and 4 2 m in 2005 mean thicknesses 4 67 and 5 18 m respectively modal and mean snow thickness on multi year ice amounted to 0 18 and 0 30 m in 2004 and 0 28 and 0 35 m in 2005 there are also considerable amounts of 0 9 2 2 m thick first year ice modal thickness mostly representing ice formed in the recurring refrozen lincoln polynya results are in good agreement with ground based electromagnetic thickness measurements and with ice types demarcated in satellite synthetic aperture radar imagery four drifting buoys deployed in 2004 between 868 n and 84 58 n show a similar pattern of a mean southward drift of the ice pack of 83 18 km between may 2004 and april 2005 towards the coast of ellesmere island and nares strait the resulting area decrease of 26 between the buoys and the coast is larger than the observed thickness increase south of 848 n this points to the importance of shear in a narrow band along the coast and of ice export through nares strait in removing ice from the study region

mountain building along a passive margin late neogene tectonism in southeastern victoria australia the hoddle ranges maximum elevation of 750 m above sea level lie along the southeastern australian passive margin detailed geological geomorphological studies of the southern margin of the ranges focusing on a fault block of oligocene miocene sedimentary rocks have constrained the landscape evolution in the mid cretaceous this area changed from a subduction zone accumulating volcanogenic sediments to a passive low relief margin which was crossed by north flowing rivers in the paleocene the eruption of basaltic volcanics formed a low divide which diverted these rivers towards the northeast so that sediments deposited on either side of the divide contain different heavy mineral assemblages in the middle late miocene early pliocene the area was subjected to a period of relatively rapid mountain building the kosciuszko uplift as broadly nw se oriented compression created the hoddle ranges at an uplift rate of 0 15 mm a uplift was not uniform a small southern block was uplifted only 200 m and its surface has acted as a local base level for the agnes river which flows across it with a major knickpoint on the southern side the southeastern highlands to the north were uplifted by up to 700 1000 m during the kosciuszko uplift similar to the maximum increase in elevation of the hoddle ranges 600 m the kosciuszko uplift tectonism occurred at rates greater than typical of passive margins and belies australia s reputation as a tectonically stable continent

on the spacing and draft distributions for pressure ridge keels the negative exponential distribution is reconsidered as a description of pressure ridge spacings and drafts it is found to give an excellent fit for drafts but not for spacings the spacing distribution is found to be fitted much better by a three parameter lognormal distribution of which the third parameter the threshold is dependent on the beam width of the instrument used to collect the ice bottom profile

digital terrain mapping of the underside of sea ice from a small auv 1 in april 2007 the first three dimensional digital terrain mapping of the underside of sea ice to be done from an ice launched autonomous underwater vehicle auv was carried out at an ice camp in the beaufort sea using the gavia vehicle which could be launched and recovered through 3 1 m holes gavia was equipped with a geoswath 500 khz interferometric sonar system which yielded swaths of typical width 80 m the imagery showed the morphological distinctions between first year fy and multi year my ice undersides the contrast between the shapes of fy and my ridges and the appearance of refrozen leads ice drafts were validated by drilling and it was found that ridge slope statistics and local probability density functions pdfs of draft could be derived with high precision the special opportunities offered by access to 3 d mapping are pointed out

wearing down wearing back and gorge extension in the long term denudation of a highland mass quantitative evidence from the shoalhaven catchment southeast australia the long standing issue of the dominance of scarp retreat versus summit lowering in the denudation of a highland mass is investigated with supporting evidence provided by tertiary basalts throughout the shoalhaven catchment in southeast australia both of these forms of denudation are found to be insignificant compared to the role of fluvial gorge extension over the last 30 m y headward advancement of the shoalhaven gorge has been occurring at approximately 15 times the rate of major escarpment retreat 250 times the average rate of summit lowering and over 500 times the rate of interfluve consumption these estimates show that the headward erosion of gorges is the most important process denuding the highlands in the shoalhaven region and possibly elsewhere in the highlands of eastern australia over the long term the highlands in this region will become considerably more dissected well before they decrease substantially in height or are narrowed this conclusion has important implications for models p

soil production in heath and forest blue mountains australia influence of lithology and palaeoclimate an erratum has been published for this article in earth surfaces processes and landforms 25 13 2005 1683 1686 recent determinations of soil production from in situ cosmogenic nuclides indicate that production decreases exponentially with soil depth this contrasts with a long held assumption that maximum soil production occurs under a soil cover of finite depth sites in the blue mountains australia show a sharp decrease of soil depth where vegetation changes from forested plateau surfaces to heath covered spurs and bands of bare rock in the heath suggest that soil production depends on presence of a finite depth of soil the substrate varies from hard ferruginized sandstone to soft saprolite in situ 10be determinations indicate that apparent rates of erosion and soil production are greater under the relatively thin heath soil than under the thicker forest soil but in contrast to other studies these sites do not show significant depth dependence of apparent soil production the pattern reflects both hardness variation in the rock substrate and the effect of late quaternary climatic change optically stimulated luminescence osl dating indicates that soil 30 cm depth is of holocene age whereas the deeper soil is substantially older the age break coincides with a stone line interpreted as a former surface lag deposit assuming that pre holocene soil depths were 30 cm less than today recalculated soil production tends to decrease with increasing depth soil production at this site requires soil cover but bare rock patches and vegetation comprise a shifting mosaic in the long term average rates of erosion and soil production decrease with increasing soil depth copyright 2005 john wiley sons ltd

the underside topography of sea ice over the continental shelf of the beaufort sea in the winter of 1990 a spatial section of draft across 348 km of sea ice was obtained by moored subsea sonars in the beaufort sea in the winter of 1990 the ice field was a mixture of first year and multiyear types with mean draft of the order of 3 m level ice of 0 to 4 m draft occupied approximately 50 of the section within this fraction draft values of 0 and 1 5 m were most common while at 2 to 3 m draft a noticeable contribution was made by rafted first year ice deformed ice was observed to a maximum draft of nearly 27 m keels within the section were identified using both the rayleigh criterion and a new criterion based on level ice both criteria defined exponentially distributed populations but with different e folding scales the observations revealed an ice cover whose statistical properties are consistent with other data from the periphery of the polar pack in the beaufort sea but which are much more severe than those of ice found in the seasonal ice zone only a few tens of kilometres to the south the cross sectional shape of individual keels was highly variable but on average the distribution of ice within a keel was an exponential function of draft the topography of both first year and old ice subsections of the data was fractal in character with a dimension of about 1 5 for both ice types the average mass of sea ice per unit area was estimated as 2540 2970 kg m 2 with 68 73 of this mass contributed by deformed ice the large uncertainties in these estimates arise because the porosity of keels and the burden of snow or melt water upon the ice are not known

assessment of soil erosion sensitivity and post timber harvesting erosion response in a mountain environment of central italy article i nfo this study aimed to assess the effects of forest management on the occurrence of accelerated soil erosion by water the study site is located in a mountainous area of the italian central apennines here forest harvesting is a widespread forestry activity and is mainly performed on the moderate to steep slopes of the highlands through modeling operations based on data on soil properties and direct monitoring of changes in the post forest harvestingsoilsurfacelevelatthehillslope scale we show thattheobserved site became pronetosoilero sion after human intervention indeed the measured mean soil erosion rate of 49 t ha 1 yr 1 for the harvested watershed is about 21 times higher than the rate measured in its neighboring undisturbed forested watershed 2 3 t ha 1 yr 1 the erosive response is greatly aggravated by exposing the just harvested forest with very limited herbaceous plant cover to the aggressive attack of the heaviest annual rainfall without adopting any conservation practices the erosivity of the storms during the first four months of field measurements was 1571 mj mm h 1 ha 1

climate scale modelling of suspended sediment load in an alpine catchment debris flow rio cordon northeastern italy abstract pulsing storms and prolonged rainfall can drive hydrological damaging events in mountain regions with soil erosion and debris flow in river catchments the paper presents a parsimonious model for estimating climate forcing on sediment loads in an alpine catchment rio cordon northeastern italian alps hydroclimatic forcing was interpreted by the novel clismssl climate scale modelling of suspended sediment load model to estimate annual sediment loads we used annual data on suspended solid loads monitored at an experimental station from 1987 to 2001 and on monthly precipitation data the quality of sediment load data was critically examined and one outlying year was identified and removed from further analyses this outlier revealed that our model underestimates exceptionally high sediment loads in years characterized by a severe flood event for all other years the clismssl performed well with a determination coefficient r2 equal to 0 67 and a mean absolute error mae of 129 mg y 1 the calibrated model for the period 1986 2010 was used to reconstruct sediment loads in the river catchment for historical times when detailed precipitation records are not available for the period 1810 2010 the model results indicate that the past centuries have been characterized by large interannual to interdecadal fluctuations in the conditions affecting sediment loads this paper argues that climate induced erosion processes in alpine areas and their impact on environment should be given more attention in discussions about climate driven strategies future work should focus on delineating the extents of these findings e g at other catchments of the european alpine belt as well as investigating the dynamics for the formation of sediment loads

laser profiling of the ice surface topography during the winter weddell gyre study 1992 a laser profiler mounted on a helicopter was used to measure the surface topography of sea ice in the weddell sea the measurements were carried out during the cruise antarktis x 4 of r v polarstern as part of the winter weddell gyre study 1992 wwgs 92 the total length of the measured surface profiles amounts to 793 km the observed mean ridge heights and mean ridge spacings are fairly well correlated therefore the ridging intensity r1 which is the ratio of ridge height and spacing was used as a quantitative classifier in order to arrange the laser data into different groups at a cutoff height of 0 8 m the average ridge height and spacing are 1 16 m and 160 m at the lowermost range of ridging intensities r1 0 04 respectively the best fits to the observed ridge height distributions are achieved by negative exponentials at lower ridging intensities as a function of ridge height at the regime of highest ridging intensity as a function of the ridge height squared the distributions of ridge spacing are well described by a lognormal distribution function a simple model is used to estimate the average thickness hd and the areal fraction of ridged ice from the laser data the values of hd range from 3 1m with an areal coverage of 5 at the lowermost range of r1 to 3 7 m with an areal coverage of 31 at the uppermost range if the ridged ice is distributed as a uniform layer over a unit area the corresponding effective thickness values are 0 14 m and 1 16 m respectively mean ridge heights and spacings are determined for different cutoff heights in order to enable comparisons to other measurements the effect of ridges on the surface stress over the ice is estimated using the drag partition theory which is applicable to the regime of lowest ridging intensity the contribution of ice ridge form drag to the total wind drag for an average ridging intensity of 0 007 and a cutoff height of 0 8 m is about 35 to 40 at neutral stability if it is assumed that the aerodynamic roughness length z0 of the intervening ice surface varies between 3 3 10 4 m and 5 5 10 4 m the drag coefficient cdn ranges from 2 08 10 3 to 2 24 10 3 at a reference height of 10 m

cause and evolution of intraplate orogeny in australia abstractintraplate orogeny remains an enigmatic process in terms of plate tectonics regional continental stress elds agree well with stress orientations predicted by the main forces driv ing and resisting plate motion however regional continental stress elds fail to explain major localized compressive plate deformation in continental interiors far away from plate bound aries global or plate wide intraplate stress models typically assume a laterally homogeneous plate rheology and are con ned to modeling the present without addressing the antiquity of the current stress eld an understanding of intraplate stress and deformation requires the linking of spatial variations in continental rheology with time dependent plate geometry and driving forces here we demonstrate how the complex interplay between juxtaposed weak and strong geological provinces and changes in far eld plate boundary forces has caused intra plate orogenesis and tectonic reactivation in southeastern australia during the tertiary our ndings are contrary to the opinion that continental interiors are insensitive to compression at plate margins and help to explain the mechanisms causing intraplate orogenesis keywords

a statistical analysis of arctic pressure ridge morphology individual pressure ridges were identified on both sensors the shape on the upward looking sonar was used to obtain draft and apparent slopes and width of each ridge while the orientation of the ridge as revealed by the side scan sonar was used to convert these figures into absolute slopes and width the data set comprises 729 ridges it was found that in addition to ridge spacing ridge drafts fit a lognormal distribution better than a negative exponential that the mean draft of ridges diminishes with downstream distance in the trans 3polar drift stream at about 0 625 m per degree suggesting a faster melt rate for ridge bottoms than for the ice as a whole and that ridge widths and slopes also fit lognormal distributions an empirical relationship was found relating ridge slope to the ratio of half width to draft the mean ridge slope varied with location but always lay in the range 21 7 to 26 5

spatial and temporal patterns of cenozoic dynamic topography around australia 1 despite its importance the spatial and temporal pattern of dynamic topography generated by mantle convective circulation is poorly known we present accurate estimates of dynamic topography from oceanic basins and continental margins surrounding australia our starting point is measurement of residual depth anomalies on the oldest oceanic floor adjacent to the continental shelf these anomalies were determined from a combined dataset of 200 seismic reflection and wide angle images of well sedimented oceanic crust they have amplitudes of between 1 km and 0 5 km and their spatial variation is broadly consistent with long wavelength free air gravity and shallow seismic tomographic anomalies along the northwest shelf a regional depth anomaly of 300 to 700 m intersects the adjacent continental shelf the temporal evolution of this anomaly was determined by analyzing the stratigraphic architecture of an extensive carbonate platform which fringes the shelf and records a dramatic switch from progradation to aggradation during neogene times three dimensional seismic mapping calibrated by boreholes was used to calculate water loaded subsidence histories at rollover points of clinoforms along the shelf at 9 3 ma the rate of subsidence increases from 5 to up 75 m myr 1 generating a subsidence anomaly of 300 to 700 m the amplitude of this anomaly varies along the shelf and cannot be generated by glacio eustatic sea level variation instead we propose that a regional subsidence episode which affects both the proximal shelf and the distal oceanic basin was generated by convective drawdown by combining our results with other published estimates of uplift and subsidence a map of australia which shows the spatial and temporal pattern of dynamic topography is presented most but not all of australia s epeirogeny can be attributed to rapid northward motion of the australian plate over a pre existing pattern of convective circulation

sea ice surface roughness estimates from airborne laser scanner and laser altimeter observations in fram strait and north of svalbard we present sea ice surface roughness estimates i e the standard deviation of relative surface elevation in the arctic regions of fram strait and the nansen basin north of svalbard acquired by an airborne laser scanner and a single beam laser altimeter in 2010 we compare the scanner to the altimeter and compare the differences between the two survey regions we estimate and correct sensor roll from the scanner data using the hyperbolic response of the scanner over a flat surface measurement surveys had to be longer than 5 km north of svalbard and longer than 15 km in fram strait before the statistical distribution in surface roughness from the scanner and altimeter became similar the shape of the surface roughness probability distributions agrees with those of airborne electromagnetic induction measurements of ice thickness the ice in fram strait had a greater mean surface roughness 0 16m vs 0 09m and a wider distribution in roughness values than the ice in the nansen basin an increase in surface roughness with increasing ice thickness was observed over fast ice found in fram strait near the coast of greenland but not for the drift ice

modeling sediment yields in italian catchments abstract sediment yield observations derived from 40 long term sedimentation records in italian reservoirs were used to calibrate and validate the spatially distributed sediment delivery model watem sedem using the best data available at national scale the sediment yield data set includes records from semi natural catchments in northern italy as well as agricultural and semi natural basins in central and southern italy the average size of the catchments is 150 km2 with mean annual sediment yields ranging from 0 20 to 20 t ha 1 year 1 watem sedem estimates mean annual sediment fluxes to permanent river channels depending on the local transport capacity the sediment flux is detachment limited or transport limited the optimal transport capacity parameters for italian conditions were derived via automatic calibration procedures a global model calibration procedure taking into account all catchments in the dataset led to an overestimation of the sediment yield for the mountain catchments and an underestimation for the non mountain catchments sediment yield estimates are more reliable when calibration procedures are applied separately for mountain and non mountain catchments the model performance of watem sedem is rather poor in the mountain catchments r 0 25 which suggests that the model structure is too simplified to come to an adequate description of the sediment fluxes the model performance for the non mountain catchments which are more important from a management point of view is significantly better r 0 51 considering the fact that data layers with a 75 75 m resolution were used the results are encouraging the further development and application of spatially distributed sediment yield models at regional and national scale levels

assessing space time variations of denudation processes and related soil loss from 1955 to 2016 in southern italy calabria region studies on denudation processes and soil loss rates can provide insight into the landscape evolution climate change and human activities as well as on land degradation risk the aims of this study were to analyze the space time distribution of denudation processes and evaluate the soil loss changes occurred during the period 1955 2016 by using an approach integrating geomorphological geospatial and modeling analysis the study area is a representative stream catchment of the crati valley calabria southern italy which is affected by severe erosion processes the combined use of aerial photographs interpretation field survey geostatistics and gis processing has allowed to characterize the types of denudation processes and land use change in space and time revised universal soil loss equation implemented in gis environment was used to estimate the space time pattern of soil loss and the soil erosion rates for each investigated year the results showed that from 1955 to 2016 the study area was highly affected by denudation processes mainly related to landslides and water erosion slope wash erosion and gully erosion comparison of denudation processes maps showed that the total area affected by erosion processes has increased by about 31 and the distribution of geomorphic processes and their space time evolution resulted from the complex interrelation between geoenvironmental features and human activities the main land use changes concerned a decrease in areas covered by woodland scrubland and pasture and an increase in croplands and barren lands that favored erosion processes the most susceptible areas to soil loss in both years were mapped and the mean soil loss rates for the study area were 6 33 mg ha 1 y 1 in 1955 and 10 38 mg ha 1 y 1 in 2016 furthermore the soil loss in 2016 has increased by about 64 compared to 1955 finally the results showed that integrating multi temporal analysis of denudation processes land use changes and soil loss rates might provide significant information on landscape evolution which supports decision makers in defining soil management and conservation practices

soil erosion risk scenarios in the mediterranean environment using rusle and gis an application model for calabria southern italy abstract soil erosion by water wse has become a relevant issue at the mediterranean level in particular natural conditions and human impact have made the calabria southern italy particularly prone to intense wse the purpose of this investigation is to identify areas highly affected by wse in calabria by comparing the scenarios obtained by assuming control and preventive measures and actions as well as actual conditions generated by forest fires also in the presence of conditions of maximum rainfall erosion geographic information system techniques have been adopted to treat data of reasonable spatial resolution obtained at a regional scale for application to the rusle model this work is based on the comparison of such data with a basic scenario that has been defined by the present situation present scenario in this scenario i r has been assessed by means of an experimental relation adjusted to calabria on the basis of 5 min observations ii k has been drawn from the soil map of calabria including 160 soilscapes iii ls has been estimated according to the rusle2 model by using among other subfactors a 40 m square cell dtm iv c has been derived by processing the data inferred from the project corine land cover whose legend includes 35 different land uses on three levels and v p has been hypothesized as equal to 1 for the remaining three hypothesized scenarios the rusle factors have been adjusted according to experimental data and to data in the literature in particular forest areas subject to fire have been randomly generated as far as fire location extension structure and intensity are concerned the values obtained by the application of the rusle model have emphasized that land management by means of measures and actions for reducing wse causes a notable reduction of the erosive rate decreasing from 30 to 12 3 mg ha 1 y 1 on the other hand variations induced by hypothetical wildfires in forests on 10 of the regional territory bring wse over the whole region to values varying from 30 to 116 mg ha 1 y 1 this study can be offered to territorial planning authorities as an evaluation instrument as it highlights the merits and limitations of some territorial management actions in fact in calabria no observations exist concerning the implications of these actions

taking a look at both sides of the ice comparison of ice thickness and drift speed as observed from moored airborne and shore based instruments near barrow alaska data from the seasonal ice zone observing network sizonet acquired near barrow alaska during the 2009 10 ice season allow novel comparisons between measurements of ice thickness and velocity an airborne electromagnetic survey that passed over a moored ice profiling sonar ips provided coincident independent measurements of total ice and snow thickness and ice draft at a scale of 10 km once differences in sampling footprint size are accounted for we reconcile the respective probability distributions and estimate the thickness of level sea ice at 1 48 0 1 m with a snow depth of 0 12 0 07 m we also complete what we believe is the first independent validation of radar derived ice velocities by comparing measurements from a coastal radar with those from an under ice acoustic doppler current profiler adcp after applying a median filter to reduce high frequency scatter in the radar derived data we find good agreement with the adcp bottom tracked ice velocities with increasing regulatory and operational needs for sea ice data including the number and thickness of pressure ridges coordinated observing networks such as sizonet can provide the means of reducing uncertainties inherent in individual datasets