coastal dune ridge systems as chronological markers of palaeoseismic activity a 650 yr record from southwest new zealand a study of two shore parallel dune ridge sequences in southwest new zealand shows that tectonic activity has been the primary controlling influence in their formation since at least ad 1450 the timing of dune building episodes at the mouths of the haast and okuru rivers was determined using the ages of colonizing trees episodic dune formation was indicated by clear discontinuities in tree ages with distinct cohorts having colonized successive newly formed dune ridge swale units at both sites four dune ridge swale units have formed since ad 1450 with each unit closely postdating an alpine fault rupture c ad 1460 c ad 1615 ad 1717 ad 1826 colonizing cohorts of trees started growing within 20 46 years after an earthquake at both sites and all known major regional earthquakes have resulted in a dunebuilding episode no other dunes are present at either site progradational coastal dune systems have potential as a tool for palaeoseismic studies in regions with high background levels of sedime

evidence for an earthquake and tsunami about 3100 3400 yr ago and other catastrophic saltwater inundations recorded in a coastal lagoon new zealand abstract okupe lagoon is 2 02 masl brackish and ponded behind two boulder banks at the northern end of kapiti island new zealand the sediments of the lagoon provide a record of late holocene environmental changes such as tectonic uplift catastrophic saltwater inundation and vegetation change five main events were identified over a 5300 yr record with a sixth representing a re evaluation of previous work an uplift event of 1 5 3 0 m and an associated tsunami are recorded and are inferred to have been caused by a local fault rupture possibly the northern extension of the wairau fault about 3360 40 yr bp two additional tsunami generated by ruptures of either the ohariu or wellington faults 1290 and 1220 ad respectively and either the wellington or alpine faults 1450 ad have been tentatively proposed two catastrophic saltwater inundations csis have also been identified one possibly a tsunami generated by either the wairarapa fault 500 ad or taupo eruption 190 ad the other about 4780 150 yr bp may relate to a local fault rupture however further work is needed to determine whether these are tsunami or storm surge related and they are therefore designated csis the sixth event is the 1855 tsunami recorded from a raised shore platform to the west of okupe lagoon

surface velocity and mass balance of ice streams d and e west antarctica over 75 000 surface velocity measurements are extracted from sequential satellite imagery of ice streams d and e to reveal a complex pattern of flow not apparent from previous measurements horizontal and vertical strain rates calculated from surface velocity indicate that the bed experiences larger basal shear where the surface of these ice streams is rougher ten airborne radar profiles and one surface based radar profile of ice thickness make possible the calculation of mass balance for longitudinal sections of each ice stream improved data collection methods increase data density substantially reducing random errors in velocity however systematic errors continue to limit the ability of the flux differencing technique used here to resolve local variations in mass balance nevertheless significant local variations in mass balance are revealed while overall ice streams d and e are in approximate equilibrium an earlier estimate of the net mass balance for ice stream d is improved

multi track extraction of two dimensional surface velocity by the combined use of differential and multiple aperture insar in the amery ice shelf east antarctica abstract glaciers and ice streams drain the ice from the ice sheets to the ice shelves and contribute to global sea level changes therefore ice velocity is an essential parameter for the assessment of mass balance in this paper we propose an approach for the multi track extraction of two dimensional ice surface velocity by the combined use of multiple aperture interferometry mai and differential synthetic aperture radar interferometry dinsar the azimuth and ground range ice movements of each individual track are first estimated by the use of mai and dinsar respectively a seamless two dimensional ice velocity map is then achieved by calibration and mosaicking of the estimated velocity of the multi temporal and multi track measurements over a large area finally the dynamic behavior of the amery ice shelf is analyzed by formulating a long term series of ice flow velocities consisting of historical surface velocities 1968 1990 the estimated surface velocity by the proposed method with ers 1 2 data 1996 existing surface velocity products such as the radarsat 1 antarctic mapping project ramp velocities 1997 2000 and rignot s results 2007 2010 as well as the estimated velocities obtained by the use of the offset tracking method from landsat 8 images 2013 2014 the results show that the estimated velocity obtained by the use of the proposed method is superior to the other methods and the long term series of ice velocity measurements shows that the ice velocity in the amery ice shelf has hardly changed over the past 45 years 1968 2014 we conclude that the ice flow velocity of the amery ice shelf has showed a slight deceleration over the past 45 years

application of image cross correlation to the measurement of glacier velocity using satellite image data abstract image to image cross correlation software is applied to pairs of digital satellite images to map the velocity field of moving ice this technique uses small scale glacial surface features such as crevasse scars and snow dunes as markers on the surface of the moving ice displacements of the surface features are mapped by selecting small image areas centered on distinct features or by dividing a large area of densely featured glacial surface into a grid of areas and searching a subsequent image for matching areas using a cross correlation algorithm interpolation of the peak correlation values allows the displacements to be measured to subpixel accuracy resulting in very precise velocity measurements cross correlation is also applied to provide image coregistration in areas devoid of bedrock exposures in such areas subtle large scale topographic undulations in the ice surface related to underlying bedrock structure may be correlated by using large image areas and low pass filtered images both types of applications are demonstrated using ice stream d and ice stream e in west antarctica as test areas a high resolution map of the velocity field of the central portion of ice stream e generated by the displacement measuring technique is presented the use of cross correlation software is a significant improvement over previous manually based photogrammetric methods for velocity measurement and is far more cost effective than in situ methods in remote polar areas

satellite image derived velocity field of an antarctic ice stream the surface velocity of a rapidly moving ice stream has been determined to high accuracy and spatial density with the use of sequential satellite imagery variations of ice velocity are spatially related to surface undulations and transverse velocity variations of up to 30 percent occur such large variations negate the concept of plug flow and call into question earlier mass balance calculations for this and other ice streams where sparse velocity data were used the coregistration of images with the use of the topographic undulations of the ice stream and the measurement of feature displacement with cross correlation of image windows provide significant improvements in the use of satellite imagery for ice flow determination

influence of tides and tidal current on mertz glacier antarctica mertz glacier east antarctica is characterized by a 140 km long 25 km wide floating ice tongue in this paper we combine a large number of remotely sensed datasets including in situ global positioning system measurements satellite radar al timetry airborne radio echo sounding and satellite synthetic aperture radar imagery and interferometry these various datasets allow us to study the interaction of the ice tongue with the tides and currents however the inverse barometer effect needs to be applied to sea level variations affecting the tongue we find that the tide induced currents exert a small lateral pressure on the tongue which when integrated over the large surface of the tongue induce a flexure of up to 2 m amplitude per day simple elastic modelling of the flexure confirms the observations and helps validate the boundary conditions necessary to explain different eastward and westward tongue deflections in addition the along flow velocity of the tongue does vary daily from 1 9 to 6 8 m d 1 depending on the tidal current when the current pushes the tongue toward the eastern boundary of the fjord the tongue is retarded by the drag and the velocity decreases the accumulated stress is released allowing the tongue to flow very rapidly when the current pushes the tongue westward these forcing and boundary conditions on the floating ice flow are important and must be taken into account when studying glacier discharge and calving

glacier crevasses observations models and mass balance implications we review the findings of approximately 60 years of in situ and remote sensing studies of glacier crevasses as well as the three broad classes of numerical models now employed to simulate crevasse fracture the relatively new insight that mixed mode fracture in local stress equilibrium rather than downstream advection alone can introduce nontrivial curvature to crevasse geometry may merit the reinterpretation of some key historical observation studies in the past three decades there have been tremendous advances in the spatial resolution of satellite imagery as well as fully automated algorithms capable of tracking crevasse displacements between repeat images despite considerable advances in developing fully transient three dimensional ice flow models over the past two decades both the zero stress and linear elastic fracture mechanics crevasse models have remained fundamentally unchanged over this time in the past decade however multidimensional and transient formulations of the continuum damage mechanics approach to simulating ice fracture have emerged the combination of employing damage mechanics to represent slow upstream deterioration of ice strength and fracture mechanics to represent rapid failure at downstream termini holds promise for implementation in large scale ice sheet models finally given the broad interest in the sea level rise implications of recent and future cryospheric change we provide a synthesis of 10 mechanisms by which crevasses can influence glacier mass balance

greenland ice sheet surface properties and ice dynamics from ers 1 sar imagery c band synthetic aperture radar sar imagery from the european space agency s ers 1 satellite reveals the basic zonation of the surface of the greenland ice sheet the zones have backscatter signatures related to the structure of the snowpack which varies with the balance of accumulation and melt at various elevations the boundaries of zones can be accurately located with the use of this high resolution imagery the images also reveal a large flow feature in northeast greenland that is similar to ice streams in antarctica and may play a major role in the discharge of ice from the ice sheet

a method for sub pixel scale feature tracking using radarsat images applied to the mertz glacier tongue east antarctica abstract tracking features between pairs of satellite synthetic aperture radar sar images using image cross correlation methods is a powerful tool for defining regions of image movement such as ice flow of antarctic glaciers unlike optical images processed sar images have various instrumental effects such as view angle distortions and lateral displacement errors caused by slant range mapping co registration issues are problematic and need to be addressed if there are few no suitable stationary tie points at or near sea level within the images methods are presented that use radarsat scansar images to reliably measure sub pixel displacements with errors of 0 25 pixels but this estimate is target dependent the techniques and issues are illustrated using examples from a long term study of the mertz glacier tongue in east antarctica for image pairs only a few days apart this extensive structure forms an excellent grid like test pattern which provides up to 5000 valid correlation matches images separated by 100 s of days can then be processed in the same way to reveal many subtle and some large changes over time the technique described is robust and may be widely applicable

soil stratigraphic techniques in the study of soil and landform evolution across the southern alps new zealand the southern alps lie along the convergent pacific indian plate boundary geomorphically distinct eastern axial and western regions reflect the east west gradient in tectonic uplift 1 to 10 mm a 1 and precipitation 600 to 10 000 mm a 1 the eastern region is divided into front ange and basin and range subregions soil sequence studies on terraces established temporal contrasts in pedogenesis within and between eastern and western regions encompassing entisols inceptisols and spodosols on late pleistocene and early holocene terraces dystrochrepts are persistent soils in the eastern region and aquods in the western region these soil sequences are used in the interpretation of relative soil age stratigraphy and erosion history in hill and mountain drainage basins of the eastern and western regions in the subhumid to humid eastern front range subregion simple soil forms occur as catenary sequences and there is little evidence of erosion following the destruction of forests in the last millenium mollisols are dominant in the subhumid and dystrochrepts in humid areas respectively soil debris mantle regoliths date from the early holocene and are still developing on slopes the soil pattern on mountain slopes in the humid eastern basin and range subregion is a complex array of simple eroded composite and compound soils this pattern has resulted from erosion following forest destruction within the last millenium the oldest surface or buried forest soils are dystrochrepts dating from the late pleistocene to early holocene wind erosion of these low fertility soils contributes to the loessial sediments in which younger soils have formed in the western region soil patterns and soil stratigraphy indicate continous instability with a complex pattern of highly leached shallow orthents and bedrock outcrops on slopes the soils are eroded from slopes within 2 ka these contrasts in soil development and erosion periodicity in the eastern and western regions of the southern alps parallel the east west contrasts in erosion rates of ca 1 10 mm a 1

evidence for eight great earthquake subsidence events detected with ground penetrating radar willapa barrier washington a new approach to detect holocene subduction zone earthquakes combines the results from ground penetrating radar gpr vibracores and accelerator mass spectrometry ams dates from a barrier spit located west of willapa bay southwest washington gpr data show a 10 m thick facies of beach sand within which we identify and vibracores confirm beach parallel wave eroded buried scarps mantled with multiple beds of magnetite the eight gpr detected buried scarps are interpreted to be eroded by minor transgressions caused by instantaneous barrier subsidence during earthquakes associated with the juan de fuca plate subducting under the north american plate of these scarps four have been ams dated at 300 1110 2540 and 4250 radiocarbon yr b p no datable material has yet been found for the other four radar detected scarps but we interpolate and extrapolate dates of 1800 3400 5000 and 5800 yr b p

examining the interaction between multi year landfast sea ice and the mertz glacier tongue east antarctica another factor in ice sheet stability the mertz glacier tongue mgt east antarctica has a large area of multi year fast sea ice myfi attached to its eastern edge we use various satellite data sets to study the extent age and thickness of the myfi and how it interacts with the mgt we estimate its age to be at least 25 years and its thickness to be 10 55 m this is an order of magnitude thicker than the average regional sea ice thickness and too thick to be formed through sea ice growth alone we speculate that the most plausible process for its growth after initial formation is marine frazil ice accretion the satellite data provide two types of evidence for strong mechanical coupling between the two types of ice the myfi moves with the mgt and persistent rifts that originate in the mgt continue to propagate for large distances into the myfi the area of myfi decreased by 50 following the departure of two large tabular icebergs that acted as pinning points and protective barriers future myfi extent will be affected by subsequent icebergs from the ninnis glacier and the imminent calving of the mgt fast ice is vulnerable to changing atmospheric and oceanic conditions and its disappearance may have an influence on ice tongue ice shelf stability understanding the influence of thick myfi on floating ice tongues ice shelves may be significant to understanding the processes that control their evolution and how these respond to climate change and thus to predicting the future of the antarctic ice sheet

semi automated feature tracking of east antarctic sea ice from envisat asar imagery while feature tracking of sea ice using cross correlation methods on pairs of satellite synthetic aperture radar sar images has been extensively carried out in the arctic this is not the case in the antarctic this is due to the dynamic nature of antarctic pack ice its microwave signature the tendency for sar swath paths to be poorly aligned with the often narrow sea ice zone around the continent and inadequate satellite sampling a semi automated system known as ipads imcorr imagecorrelation processing analysis and display system has been developed to map fast ice and pack ice in antarctica using multiple pairs of sar images the software processing pipeline uses overlapping image pairs which are geocoded and roughly registered using only data contained in the image headers next fast ice maps are rapidly generated using zero motion features located within ocean regions this also provides precise image registration finally the same image pairs are re examined for pack ice motion in a slower off line batch process the pack and fast ice are identified using a cluster based search method which compares both location and motion information each image pair generates a netcdf file which adds to a growing database of antarctic sea ice motion and ice roughness five image pair examples are presented to illustrate the methods used as well as their strengths and limitations substantial pack ice motion can often be detected in the marginal ice zone on sar images only a few days apart

remote sensing of ice motion in antarctica a review abstract the antarctic ice sheet holds 91 of the global ice mass making it the biggest potential contributor to global sea level rise in order to evaluate the ice sheet s present and future response to global climate change detailed information about spatial and temporal ice mass dynamics is required while ice sheet surface mass balance can be estimated from regional climate models ice discharge is often determined from spaceborne measurements of ice thickness and ice motion at selected flux gates the retrieval of ice motion is not only critical for analysing the rate of ice transport into the ocean but also for investigating the spatial and temporal pattern or the driving forcings of antarctic ice flow dynamics this study provides a comprehensive review of state of the art spaceborne ice velocity measurements in antarctica based on 201 scientific papers published over the last three decades our analysis revealed a dominant interest in local and regional scale investigations yet the launch of the ers 1 2 and radarsat 1 sar satellites in the 1990s dramatically increased data coverage over the antarctic continent and enabled the first circum antarctic velocity product to be published in the late 2000s in recent years the improved imaging capabilities of landsat 8 led to a shift towards using mainly optical satellite data and enabled great advances in circum antarctic velocity mapping data from the currently operating sentinel 1 2 missions was applied in fewer studies but will play a crucial role in future ice motion studies e g as part of esa cci projects in addition we found a growing interest in high temporal resolution velocity change analyses based on the reviewed studies we moreover summarized the highly dynamic and locally variable flow pattern over the antarctic continent being in accordance with varying local and regional driving mechanisms despite the great advances in spaceborne ice velocity mapping in antarctica we report some major drawbacks and discuss future challenges and requirements to start with our study uncovered strong variations regarding the spatial availability of investigations while we found an aggregation of studies over selected glaciers we report a major lack of studies in all three antarctic sectors additionally many velocity datasets were created with strongly heterogeneous output parameters and were provided at coarse temporal resolution or at point based measurement locations only future studies should consequently aim at creating more uniform ice motion products at defined spatial and temporal coverage and resolution standards and at analysing particularly the least studied glaciers

seismic driving of nationwide changes in geomorphology and prehistoric settlement a 15th century new zealand example abstract we propose a model for the seismic driving of environmental changes and illustrate it using a case study from new zealand dated to the 15th century ad a seismic staircase shows a chronological progression of environmental outcomes that includes tsunami rock avalanches vegetation disturbance rapid coastal dune building river aggradation and abandonment of prehistoric coastal settlements the 15th century event appears to be unique in the past millenium and is most notable for its period of rapid coastal dune building the coincidence of a catastrophic el nino episode in the mid 15th century ad may have served to move sediments rapidly through the terrestrial system thus delimiting clearly separate geomorphological after effects we contend that seismic driving is a major factor in determining paleoenvironmental change in tectonically active areas during the holocene and provides the palaeoenvironmental context within which smaller scale events operate

deformation time series generation in areas characterized by large displacement dynamics the sar amplitude pixel offset sbas technique we exploit the amplitude information of a sequence of synthetic aperture radar sar images acquired at different times in order to generate displacement time series in areas characterized by large and or rapid deformation the size of which is on the order of the image s pixel dimensions we follow the same rationale of the small baseline subset sbas differential sar interferometry dinsar approach by coupling the available sar images into pairs characterized by a small separation between the acquisition orbits we exploit the amplitudes of the selected image pairs in order to calculate the relative across track range and along track azimuth pixel offsets po finally we apply the sbas inversion strategy to retrieve the range and azimuth displacement time series this approach referred to as pixel offset po sbas technique has been applied to a set of 25 envisat sar observations of the sierra negra caldera galapagos islands spanning the 2003 2007 time interval the retrieved deformation time series show the capability of the technique to detect and measure the large displacements affecting the inner part of the caldera that in correspondence to the october 2005 eruption reached several meters moreover by comparing the po sbas results to continuous gps measurements we estimate that the accuracy of the po sbas time series is on the order of 1 30th of a pixel for both range and azimuth directions

prehistoric dates of the most recent alpine fault earthquakes new zealand we use four methods to investigate the earthquake history over the past 600 yr of the central alpine fault new zealand trenches across the active fault trace at five locations identify two ruptures on the fault in the past 450 yr three other indirect indicators episodes of landsliding and aggradation dated either via 14 c or from forest establishment on the resulting surfaces and tree ring growth anomalies provide further evidence for these two earthquakes and a greater resolution in estimates of their timing and extent the most recent earthquake occurred in a d 1717 and the rupture extended over a section of fault between milford and the haupiri river a distance of 375 km about 1630 another earthquake occurred on the fault and this extended between at least the paringa and ahaura rivers 250 km regional episodes of landsliding and forest establishment provide evidence for a third earthquake at about 1460 over the same section of fault the pattern of earthquake recurrence is not regular but averages 200 yr and varies from 100 yr to at least 280 yr which is the lapsed time since the most recent rupture

widespread acceleration of tidewater glaciers on the antarctic peninsula over the last half century the antarctic peninsula ap has been among the most rapidly warming regions on earth this has led to increased summer snowmelt loss of ice shelves and retreat of 87 of marine and tidewater glacier fronts tidewater glacier flow is sensitive to changes in basal water supply and to thinning of the terminus and faster flow leads directly to sea level rise the flow rates of most ap tidewater glaciers have never been measured however and hence their dynamic response to the recent changes is unknown we present repeated flow rate measurements from over 300 glaciers on the ap west coast through nine summers from 1992 to 2005 we show that the flow rate increased by similar to 12 on average and that this trend is greater than the seasonal variability in flow rate we attribute this widespread acceleration trend not to meltwater enhanced lubrication or increased snowfall but to a dynamic response to frontal thinning we estimate that as a result the annual sea level contribution from this region has increased by 0 047 0 011 mm between 1993 and 2003 this contribution together with previous studies that assessed increased runoff from the area and acceleration of glaciers resulting from the removal of ice shelves implies a combined ap contribution of 0 16 0 06 mm yr 1 this is comparable to the contribution from alaskan glaciers and combined with estimated mass loss from west antarctica is probably large enough to outweigh mass gains in east antarctica and to make the total antarctic sea level contribution positive

the mertz glacier tongue east antarctica changes in the past 100 years and its cyclic nature past present and future the mertz glacier tongue mgt in east antarctica has been studied since 1911 early expeditions produced maps using ground or ship based observations followed later by vertical and or oblique aerial photography from aircraft in the modern era extensive digital satellite imagery is available which has also been supplemented by the resurrection and scanning of some historic u s now declassified film based satellite images much of the mgt became detached and drifted away following the collision by the b 9b iceberg in february 2010 and a similar sequence or extension detachment cycle must have occurred some time after mawson s 1911 1914 observations all the available information on the position shape or appearance of the mgt has been re examined in an attempt to comprehensively study its past present and possible future motion feature tracking cross correlation methods have been applied for suitably detailed image pairs to accurately measure the mgt advance velocity the derived mean rate for 1947 2010 is 1180 14 m y 1 with an accompanying ice front loss rate of 190 m y 1 a simple model for the mgt exhibits a 73 year quasi periodic cycle of rebirth growth and demise which will affect the volume of bottom water produced in the nearby polynya some evidence for this cyclic oceanographic change has recently been reported from regional sediment data somewhat speculatively the model suggests a date of 1937 for the previous mgt break off and around or before 2083 for the next with the mgt being primed to break off every 73 years the precise date being governed by unpredictable external events such as collisions by large icebergs such cycles have probably occurred for many thousands of years

fast ice distribution in east antarctica during 1997 and 1999 determined using radarsat data 1 we present the first detailed maps of fast ice around east antarctica 75 e 170 e using an image correlation technique applied to radarsat scansar images from november in 1997 and 1999 this method is based upon searching for and distinguishing correlated regions of the ice covered ocean which remain stationary in contrast to adjacent moving pack ice within the overlapping longitudinal range of 86 e 150 6 e the total fast ice area is 141 450 km2 in 1997 and 152 216 km2 in 1999 calibrated radar backscatter data are also used to determine the distribution of two fast ice classes based on their surface roughness characteristics these are smooth fast ice 25 4 db to 13 5 db and rough fast ice 13 5 db to 2 5 db the former comprises 67 of the total area with rough fast ice making up the remaining 33 an estimate is made of fast ice volume on the basis of fast ice type as a proxy measure of ice thickness and area results suggest that although fast ice forms 2 16 of the total november sea ice area for this sector of east antarctica in 1997 and 1999 average 8 3 across maps it may comprise 6 57 of the total ice volume average 28 across maps grounded icebergs play a key role in fast ice distribution in all regions apart from 150 e 170 e these are snapshot estimates only and more work is required to determine longer term spatiotemporal variability

geophysical characterization of udaeta lake as a possible pull apart basin associated to quaternary tectonic activity along magallanes fagnano fault system abstract pull apart basins are depressions formed at releasing bends or steps in strike slip fault systems between two parallel vertical strike slip fault sections in the present study the geometry of udaeta lake located in the central section of the magellan fagnano fault system mffs and previously defined by some authors as a pull apart basin is analysed the application of multiple geophysical methods constrained by surface geological information enabled us to reveal the subsurface geometry of a section of the mffs udaeta lake area magnetic gravimetric and detailed topographic profiles together with vertical electrical soundings were surveyed the obtained results were compared with fieldwork data this combined methodology allowed the identification of a transtensional zone with two e w main sinistral strike slip faults with a normal component that control the north and south coasts of the lake this central depression occupied by the lake with a depth of 30 m is also affected by inferred ne subparallel faults the geophysical characterization of the mffs also supports the influence of this fault system on the formation of some water bodies located along the fault zone finally in spite of the lack of detailed geological and structural data udaeta lake we suggest a genesis consistent with a pull apart basin model this work constitutes an important contribution to understand earthquake rupture parameters and pattern of surface and in depth deformation and so improve knowledge of the seismological behaviour of the mffs