impact of iceberg calving on the retreat of thwaites glacier west antarctica over the next century with different calving laws and ocean thermal forcing

rapid circulation of warm subtropical waters in a major glacial fjord in east greenland the recent rapid increase in mass loss from the greenland ice sheet is primarily attributed to an acceleration of outlet glaciers oceanographic data obtained in summer 2008 show that subtropical waters that reside year round in the shelf ocean off greenland continuously enter a large glacial fjord in east greenland and contribute to melting at the glacier terminus the recent rapid increase in mass loss from the greenland ice sheet1 2 is primarily attributed to an acceleration of outlet glaciers3 4 5 one possible cause of this acceleration is increased melting at the ice ocean interface6 7 driven by the synchronous warming8 9 10 of subtropical waters offshore of greenland however because of the lack of observations from greenland s glacial fjords and our limited understanding of their dynamics this hypothesis is largely untested here we present oceanographic data collected in sermilik fjord east greenland by ship in summer 2008 and from moorings our data reveal the presence of subtropical waters throughout the fjord these waters are continuously replenished through a wind driven exchange with the shelf where they are present all year the temperature and renewal of these waters indicate that they currently cause enhanced submarine melting at the glacier terminus key controls on the melting rate are the volume and properties of the subtropical waters on the shelf and the patterns of along shore winds suggesting that the glaciers acceleration has been triggered by a combination of atmospheric and oceanic changes our measurements provide evidence for a rapid advective pathway for the transmission of oceanic variability to the ice sheet margins

ocean forcing of the greenland ice sheet calving fronts and patterns of retreat identified by automatic satellite monitoring of eastern outlet glaciers 1 we have developed an automatic method to identify changes in the position of calving glacier margins using daily modis imagery application of the method to 32 ocean terminating glaciers in east greenland produced 26 802 margin positions for a 10 year long period 2000 2009 we report these high resolution data and show that the glaciers exhibit seasonal cycles with magnitudes of advance and retreat proportional to glacier width despite similar seasonality there is a distinct difference between the interannual trends of calving front positions north and south of 69 n all glaciers above this latitude showed very limited or no change when seasonality was excluded while glaciers south of 69 n retreated significantly between 2001 and 2005 2 3 km on average approximately 26 of the retreat of southern glaciers was regained by readvance from 2005 to 2009 to explain the latitudinal boundary of glacier dynamics we review basic climatic factors including summer and winter atmospheric forcing sea ice conditions and ocean temperature we conclude that the southern retreats were strongly influenced by warm oceanic conditions associated with increased transport of subtropical waters to the irminger sea and to fjords and coastal regions south of 69 n northern glaciers remained stable despite significant increase in runoff in this region because fjords at latitudes higher than 69 n are less exposed to subtropical waters the southern retreats illustrate sensitive behavior of calving glaciers and we hypothesize that the calving fronts retreated because they were exposed to rapid ice front melting

the limiting pressure on a circular pile loaded laterally in cohesive soil in the analysis of the undrained loading of laterally loaded piles an important quantity is the ultimate lateral resistance at depth to purely horizontal movement if the soil is modelled as a perfectly plastic cohesive material then the calculation of this quantity reduces to a plane strain problem in plasticity theory in which the load is calculated on a long cylinder which moves laterally through an infinite medium an exact calculation of the load on such a cylinder is presented if this load is non dimensionalized with respect to the soil strength and the diameter of the pile it is found that the load factor varies between for a perfectly smooth pile and for a perfectly rough pile this result is discussed in the context of previous calculations for the lateral load capacity of piles and is compared with approximate calculations using cavity expansion theory and a wedge failure near the soil surface la resistance laterale limite en profondeur au seul mouvement horizontal represente un parametre im

effects of preloading and consolidation on the uplift capacity of skirted foundations centrifuge tests investigating the effect of compressive preloading and consolidation on the subsequent uplift capacity of shallow skirted foundations that rest on lightly over consolidated kaolin clay are reported the uplift resistance total and pore pressures at the foundation invert were monitored during the installation consolidation and uplift the results show that uplift performed immediately after the preloading generates a lower capacity due to the remoulding of the clay and reduction in soil strengths that result from the application of preloading the soil strength can be recovered and eventually enhanced by the subsequent consolidation process a theoretical framework where the variation of the soil operative strength with preloading and consolidation is interpreted using the critical state concept is proposed to explain and justify the experimental observations the framework is validated through retrospective prediction of the uplift resistance of the centrifuge model tests with good ag

rapid submarine melting of the calving faces of west greenland glaciers widespread glacier acceleration has been observed in greenland in the past few years oceanographic observations taken in summer 2008 show that ocean waters melted a substantial fraction of ice along the calving fronts of three west greenland glaciers indicating that submarine melting has a profound influence on grounding line stability widespread glacier acceleration has been observed in greenland in the past few years1 2 3 4 associated with the thinning of the lower reaches of the glaciers as they terminate in the ocean5 6 7 these glaciers thin both at the surface from warm air temperatures and along their submerged faces in contact with warm ocean waters8 little is known about the rates of submarine melting9 10 11 and how they may affect glacier dynamics here we present measurements of ocean currents temperature and salinity near the calving fronts of the eqip sermia kangilerngata sermia sermeq kujatdleq and sermeq avangnardleq glaciers in central west greenland as well as ice front bathymetry and geographical positions we calculate water mass and heat budgets that reveal summer submarine melt rates ranging from 0 7 0 2 to 3 9 0 8 m d 1 these rates of submarine melting are two orders of magnitude larger than surface melt rates but comparable to rates of iceberg discharge we conclude that ocean waters melt a considerable but highly variable fraction of the calving fronts of glaciers before they disintegrate into icebergs and suggest that submarine melting must have a profound influence on grounding line stability and ice flow dynamics

the parkable piezoprobe for determining c v and strength modelling and interpretation methods the parkable piezoprobe is a site investigation tool for measuring the coefficient of consolidation in situ offshore at shallow embedment depths the device applies a similar bearing pressure to

heat salt and freshwater budgets for a glacial fjord in greenland abstractin greenland s glacial fjords heat and freshwater are exchanged between glaciers and the ocean submarine melting of glaciers has been implicated as a potential trigger for recent glacier acceleration and observations of ocean heat transport are increasingly being used to infer the submarine melt rates the complete heat salt and mass budgets that underlie such methods however have been largely neglected here a new framework for exploring glacial fjord budgets is developed building on estuarine studies of salt budgets the heat salt and mass transports through the fjord are decomposed and new equations for calculating freshwater fluxes from submarine meltwater and runoff are presented this method is applied to moored records from sermilik fjord near the terminus of helheim glacier to evaluate the dominant balances in the fjord budgets and to estimate freshwater fluxes throughout the year two different regimes are found in the nonsummer months advective transports are balanced by

controls on the early holocene collapse of the bothnian sea ice stream new high resolution multibeam data in the gulf of bothnia reveal for the first time the subglacial environment of a bothnian sea ice stream the geomorphological record suggests that increased meltwater production may have been important in driving rapid retreat of bothnian sea ice during deglaciation here we apply a well established one dimensional flowline model to simulate ice flow through the gulf of bothnia and investigate controls on retreat of the ice stream during the post younger dryas deglaciation of the fennoscandian ice sheet the relative influence of atmospheric and marine forcings are investigated with the modelled ice stream exhibiting much greater sensitivity to surface melting implemented through surface mass balance and hydrofracture induced calving than to submarine melting or relative sea level change such sensitivity is supported by the presence of extensive meltwater features in the geomorphological record the modelled ice stream does not demonstrate significant sensitivity to changes in prescribed ice stream width or overall bed slope but local variations in basal topography and ice stream width result in non linear retreat of the grounding line notably demonstrating points of short lived retreat slowdown on reverse bed slopes retreat of the ice stream was most likely governed by increased ice surface meltwater production with the modelled retreat rate less sensitive to marine forcings despite the marine setting

origin of the northern indus fan and murray ridge northern arabian sea interpretation from seismic and magnetic imaging abstract the nature and origin of the sediments and crust of the murray ridge system and northern indus fan are discussed the uppermost unit consists of middle miocene to recent channel levee complexes typical of submarine fans this unit is underlain by a second unit composed of hemipelagic to pelagic sediments deposited during the drift phase after the break up of india seychelles africa a predrift sequence of assumed mesozoic age occurring only as observed above basement ridges is composed of highly consolidated rocks different types of the acoustic basement were detected which reflection seismic pattern magnetic anomalies and gravity field modeling indicate to be of continental character the continental crust is extremely thinned in the northern indus fan lacking a typical block faulted structure the indian continent ocean transition is marked on single mcs profiles by sequences of seaward dipping reflectors sdr in the northwestern arabian sea the indian plate margin is characterized by several phases of volcanism and deformation revealed from interpretation of multichannel seismic profiles and magnetic anomalies from this study thinned continental crust spreads between the northern murray ridge system and india underneath the northern indus fan

channelized bottom melting and stability of floating ice shelves 1 the floating ice shelf in front of petermann glacier in northwest greenland experiences massive bottom melting that removes 80 of its ice before calving into the arctic ocean detailed surveys of the ice shelf reveal the presence of 1 2 km wide 200 400 m deep sub ice shelf channels aligned with the flow direction and spaced by 5 km we attribute their formation to the bottom melting of ice from warm ocean waters underneath drilling at the center of one of channel only 8 m above sea level confirms the presence of ice shelf melt water in the channel these deep incisions in ice shelf thickness imply a vulnerability to mechanical break up and climate warming of ice shelves that has not been considered previously

experimental investigation of reverse end bearing of offshore shallow foundations shallow skirted foundations can mobilize uplift resistance from end bearing in the short to medium term however uncertainty exists over the magnitude of reverse end bearing resistance compared wi

acceleration of the contribution of the greenland and antarctic ice sheets to sea level rise 1 ice sheet mass balance estimates have improved substantially in recent years using a variety of techniques over different time periods and at various levels of spatial detail considerable disparity remains between these estimates due to the inherent uncertainties of each method the lack of detailed comparison between independent estimates and the effect of temporal modulations in ice sheet surface mass balance here we present a consistent record of mass balance for the greenland and antarctic ice sheets over the past two decades validated by the comparison of two independent techniques over the last 8 years one differencing perimeter loss from net accumulation and one using a dense time series of time variable gravity we find excellent agreement between the two techniques for absolute mass loss and acceleration of mass loss in 2006 the greenland and antarctic ice sheets experienced a combined mass loss of 475 158 gt yr equivalent to 1 3 0 4 mm yr sea level rise notably the acceleration in ice sheet loss over the last 18 years was 21 9 1 gt yr2 for greenland and 14 5 2 gt yr2 for antarctica for a combined total of 36 3 2 gt yr2 this acceleration is 3 times larger than for mountain glaciers and ice caps 12 6 gt yr2 if this trend continues ice sheets will be the dominant contributor to sea level rise in the 21st century

interpretation of t bar penetrometer tests at shallow embedment and in very soft soils the cylindrical t bar penetrometer was developed for profiling the undrained strength of soft soils in the centrifuge and is now a widely used offshore site investigation tool the conventional interpretation of the t bar test is to convert the measured penetration resistance to soil strength using a single bearing factor associated with steady flow of soil around the bar this paper describes a new analysis for the interpretation of t bar penetrometer tests at shallow embedment and in soft soils which is an increasingly significant consideration in the design of seabed infrastructure including pipelines the analysis captures two mechanisms that are usually neglected i soil buoyancy and ii the reduced bearing factor arising from the shallow failure mechanism mobilized prior to the full flow of soil around the bar the framework derives from theoretical considerations and is calibrated using large deformation finite element analyses the depth at which the steady deep penetration condition is reach

q structure beneath the north and central indian ocean from the inversion of observed love and rayleigh wave attenuation data abstract the fundamental mode love and rayleigh waves generated by 57 earthquakes which occurred in the north and central indian ocean extending to 40 s and recorded at indian seismograph and other wwssn stations such as how shl vis mdr hyb kod chg trd poo bom goa ndi nil and que are analysed love and rayleigh wave attenuation coefficients are estimated at periods of 15 100 s using the spectral amplitude of these waves for 98 different paths across the bay of bengal fan the arabian fan and the north and central indian ocean the large standard deviations observed in the surface wave attenuation coefficients may be a result of regional variation of the attenuative properties of the crust and upper mantle beneath these regions love wave attenuation coefficients are found to vary from 0 000 03 to 0 000 45 km 1 for the bay of bengal fan from 0 000 03 to 0 000 85 km 1 for the arabian fan and from 0 000 03 to 0 000 35 km 1 for the north and central indian ocean similarly rayleigh wave attenuation coefficients vary from 0 000 03 to 0 0004 km 1 for the bay of bengal fan from 0 000 06 to 0 0007 km 1 for the arabian fan and from 0 000 03 to 0 0007 km 1 for the north and central indian ocean backus and gilbert inversion theory is applied to these surface wave attenuation data to obtain average q 1 models for the crust and upper mantle beneath the bay of bengal the arabian fan and the north and central indian ocean inversion of love and rayleigh wave attenuation data shows a high attenuation zone centred at a depth of 120 km q 125 for the bay of bengal fan similarly a high attenuation zone q 40 70 occurs at a depth of 60 160 km for the arabian fan at 100 160 km q 115 for the indian ocean off ninetyeast ridge and at 80 160 km q 80 for the indian ocean across the ninetyeast ridge the q 1 models show a lithosphere thickness of 120 km beneath the bay of bengal fan similarly lithosphere thickness of 70 100 and 80 km is estimated beneath the arabian fan and the indian ocean off ninetyeast ridge and across ninetyeast ridge respectively the base of the lithosphere is identified as the depth at which there is a significant increase in the q 1 value which attains its maximum value in the asthenosphere the thinning of indian lithosphere beneath the arabian fan suggests high temperature below moho depth 60 km from surface which has caused a high attenuation zone at this shallow depth

quasi continental oceanic structure beneath the arabian fan sediments from observed surface wave dispersion studies the fundamental and higher modes of surface waves generated by 31 earthquakes and recorded at seismographic stations along the western margins of india and pakistan trivandrum kodaikanal goa bombay poona new delhi nillore and quetta are used to estimate the crustal structure beneath the arabian fan sediments the sedimentary thickness is determined from the observed higher mode data the observed dispersion data suggest an increase in crustal thickness northward from an approximately 16 km crustal thickness at the southern tip of india trivandrum to an approximately 28 km crustal thickness at the regions of 20 n and above latitude with an overlying 6 km sedimentary thickness this gradual increase in crustal thickness in the northward direction and the attaining of quasi continental oceanic transition from continent to ocean structure beneath the arabian fan sediments suggest that the mohorovicic discontinuity may have resulted from a change in crystal structure due to increase of pressure and not a phase change the same material exists beneath the moho and it does not represent the boundary between two different materials the transition has given rise to crustal thickening in the northward direction another possible explanation is that the increase in hydrostatic pressure due to the load exerted by a large sedimentary column together with horizontal pressure caused by the collision of indian and eurasian plates has given rise to an increase in temperature near the moho because of the thermal blanketing effect of this large sedimentary column an inferred rise in temperature may have either changed the upper mantle into material with crustal like velocity or may have given rise to metamorphism of earlier existing sedimentary rocks an inferred high temperature near the moho depth beneath the arabian fan sediments is in close agreement with the high attenuating zone at the shallow depth 30 to 45 km as determined by singh 1987

structure and dynamics of a subglacial discharge plume in a greenlandic fjord discharge of surface derived meltwater at the submerged base of greenland s marine terminating glaciers creates subglacial discharge plumes that rise along the glacier ocean interface these plumes impact submarine melting calving and fjord circulation observations of plume properties and dynamics are challenging due to their proximity to the calving edge of glaciers therefore to date information on these plumes has been largely derived from models here we present temperature salinity and velocity data collected in a plume that surfaced at the edge of saqqarliup sermia a mid sized greenlandic glacier the plume is associated with a narrow core of rising waters approximately 20 m in diameter at the ice edge that spreads to a 200 m by 300 m plume pool as it reaches the surface before descending to its equilibrium depth volume flux estimates indicate that the plume is primarily driven by subglacial discharge and that this has been diluted in a ratio of 1 10 by the time the plume reaches the surface while highly uncertain meltwater fluxes are likely two orders of magnitude smaller than the subglacial discharge flux the overall plume characteristics agree with those predicted by theoretical plume models for a convection driven plume with limited influence from submarine melting this article is protected by copyright all rights reserved

shallow penetrometer tests theoretical and experimental modelling of penetration and dissipation stages shallow penetrometers are devices that penetrate into and measure the properties of surficial offshore sediments via multi phase tests involving penetration dissipation and rotation stages in fi

spatio temporal variations in seasonal ice tongue submarine melt rate at a tidewater glacier in southwest greenland submarine melting of tidewater glaciers is proposed as a trigger for their recent thinning acceleration and retreat we estimate spring submarine melt rates smrs of kangiata nunaata sermia in southwest greenland from 2012 to 2014 by examining changes in along fjord freeboard and velocity of the seasonal floating ice tongue estimated smrs vary spatially and temporally near the grounding line with mean rates of 1 3 0 6 0 8 0 3 and 1 0 0 4 m d 1 across the tongue in 2012 2013 and 2014 respectively higher melt rates correspond with locations of emerging subglacial plumes and terminus calving activity observed during the melt season using time lapse camera imagery modelling of subglacial flow paths suggests a dynamic system capable of rapid re routing of subglacial discharge both within and between melt seasons our results provide an empirically derived link between the presence of subglacial discharge plumes and areas of high spring submarine melting and calving along glacier termini

the mechanisms behind jakobshavn isbrae s acceleration and mass loss a 3 d thermomechanical model study the mechanisms causing widespread flow acceleration of jakobshavn isbrae west greenland remain unclear despite an abundance of observations and modeling studies here we simulate the glacier s evolution from 1985 to 2016 using a three dimensional thermomechanical ice flow model the model captures the timing and 90 of the observed changes by forcing the calving front basal drag in the trough is low and lateral drag balances the ice stream s driving stress the calving front position is the dominant control on changes of jakobshavn isbrae since the ice viscosity in the shear margins instantaneously drops in response to the stress perturbation caused by calving front retreat which allows for widespread flow acceleration gradual shear margin warming contributes 5 to 10 to the total acceleration our simulations suggest that the glacier will contribute to eustatic sea level rise at a rate comparable to or higher than at present

rapid submarine melting driven by subglacial discharge leconte glacier alaska 1 we show that subglacial freshwater discharge is the principal process driving high rates of submarine melting at tidewater glaciers this buoyant discharge draws in warm seawater entraining it in a turbulent upwelling flow along the submarine face that melts glacier ice to capture the effects of subglacial discharge on submarine melting we conducted 4 days of hydrographic transects during late summer 2012 at leconte glacier alaska a major rainstorm allowed us to document the influence of large changes in subglacial discharge we found strong submarine melt fluxes that increased from 9 1 1 0 to 16 8 1 3 m d 1 ice face equivalent frontal ablation as a result of the rainstorm with projected continued global warming and increased glacial runoff our results highlight the direct impact that increases in subglacial discharge will have on tidewater outlet systems these effects must be considered when modeling glacier response to future warming and increased runoff

remote sensing of glacier and ice sheet grounding lines a review abstract the precise positioning and long term monitoring of the grounding line forming the boundary between grounded and floating ice of marine ice sheets and tidewater glaciers is critical for assessing ice sheet glacier stability ice sheet glacier mass balance calculations and numerical ice modelling however mapping of the grounding line is a challenging task since it is a subglacial and transient feature remote sensing techniques do not map the grounding line directly but locate surface features in the grounding zone that serve as proxies for the true grounding line position the large variety of methods products and publications as well as an inconsistent use of terminology additionally complicate the topic we present the first detailed review of existing remote sensing techniques and data for grounding line mapping benefits and limitations of the different techniques and data sources are discussed and illustrated with examples we identify a present tradeoff between accuracy and both spatial coverage and temporal resolution of the derived grounding line products rather new methods like sentinel 1 sar synthetic aperture radar differential range offset tracking drot and pseudo crossover radar altimetry pcra offer the potential for recent measurements and to fill gaps in some areas nevertheless there is a high demand of new spaceborne radar sensors that provide time series of very short repeat pass data to enable regular grounding line monitoring with most accurate differential sar interferometry dinsar on a continental scale

submarine melting of the 1985 jakobshavn isbrae floating tongue and the triggering of the current retreat 1 photogrammetric reanalysis of 1985 aerial photos has revealed substantial submarine melting of the floating ice tongue of jakobshavn isbrae west greenland the thickness of the floating tongue determined from hydrostatic equilibrium tapers from 940 m near the grounding zone to 600 m near the terminus feature tracking on orthophotos shows speeds on the july 1985 ice tongue to be nearly constant 18 5 m d 1 indicating negligible dynamic thinning the thinning of the ice tongue is mostly due to submarine melting with average rates of 228 49 m yr 1 0 62 0 13 m d 1 between the summers of 1984 and 1985 the cause of the high melt rate is the circulation of warm seawater thermal forcing of up to 4 2 c beneath the tongue with convection driven by the substantial discharge of subglacial freshwater from the grounding zone we believe that this buoyancy driven convection is responsible for a deep channel incised into the sole of the floating tongue a dramatic thinning retreat and speedup began in 1998 and continues today the timing of the change is coincident with a 1 1 c warming of deep ocean waters entering the fjord after 1997 assuming a linear relationship between thermal forcing and submarine melt rate average melt rates should have increased by 25 57 m yr 1 sufficient to destabilize the ice tongue and initiate the ice thinning and the retreat that followed

three dimensional imaging of the s velocity structure for the crust and the upper mantle beneath the arabian sea from rayleigh wave analysis a 3d imaging of s velocity for the arabian sea crust and upper mantle structure is presented in this paper determined by means of rayleigh wave analysis for depths ranging from zero to 300 km the crust and upper mantle structure of this region of the earth never has been the subject of a surface wave tomography survey the moho map performed in the present study is a new result in which a crustal thickening beneath the arabian fan sediments can be observed this crustal thickening can be interpreted as a quasi continental oceanic transitional structure a crustal thickness of up to 20 km also can be observed for the murray ridge system in this moho map this crustal thickening can be due to that the murray ridge system consists of indian continental crust this continental crust is extremely thinned to the southwest of this region as shown in this moho map this area can be interpreted as oceanic in origin in the depth range from 30 to 60 km the s velocity presents its lower values at the carlsberg ridge region because it is the younger region of the study area in the depth range from 60 to 105 km of depth the s velocity pattern is very similar to that shown for the previous depth range except for the regions in which the asthenosphere is reached for these regions appear a low s velocity pattern the lithosphere asthenosphere boundary lab or equivalently the lithosphere thickness determined in the present study is also a new result in which the lithosphere thickness for the arabian fan can be estimated in 60 70 km the lower lithospheric thickness observed in the lab map for the arabian fan shows that this region may be in the transition zone between continental and oceanic structure finally a low velocity zone lvz has been determined for the whole study area located between the lab and the boundary of the asthenosphere base or equivalently the lithosphere asthenosphere system thickness the asthenosphere base map calculated in the present study is also a new result

behaviour of ball penetrometer in uniform single and double layer clays the spherical ball penetrometer is increasingly being used for profiling the undrained shear strength of soils in centrifuge and offshore site investigations this paper reports the results from large deformation finite element ldfe analysis undertaken to provide insight into ball penetrometer behaviour during undrained vertical penetration through uniform and stratified clay deposits the ldfe analyses simulated continuous penetration of ball penetrometers from the seabed surface the results were validated against centrifuge test data and plasticity solutions prior to undertaking a detailed parametric study exploring a range of normalised soil properties and layer thicknesses and roughnesses of the soil ball interface the influence of the shaft or area ratio was also identified the evolving soil failure patterns in single and double layer soils revealed two interesting aspects soil backflow above the penetrometer and trapping of the stronger material beneath the penetrometer a framework has b

constraints on plate motions in southern pakistan and the northern arabian sea from the focal mechanisms of small earthquakes the focal mechanism and depth were determined for nine small earthquakes m0 1025 dyn cm m 5 5 that occurred in southern pakistan and the northern arabian sea from an analysis of the vertical component of rayleigh waves in combination with limited first motion data focal parameters were determined from the rayleigh waves by using an event pair method of analysis for earthquakes that are located very close to each other 50 km the event pair method is able to remove a significant proportion of propagation effects at all periods in the range of interest 20 50 s for events separated by more than 100 km the propagation effects are reduced for only the longer periods 40 50 s the earthquakes that were studied provide evidence for a model of plate interactions in the vicinity of the southern pakistan triple junction the owen fracture zone is a transform fault that accommodates right lateral motion between the indian and arabian plates the plate boundary in the vicinity of the murray ridge is also partially made up of transform segments that strike subparallel to the owen fracture zone spreading centers may also exist in the vicinity of the murray ridge but were not documented by seismic or other evidence the slip azimuths for earthquakes along this boundary are significantly more northerly than those predicted by various regional and worldwide models of plate motion the arabian plate is being subducted beneath the eurasian plate along the southern coast of pakistan slip vectors for earthquakes along this boundary trend northnortheasterly in general agreement with predicted directions left lateral motion is documented along the boundary between the indian and eurasian plates in southern pakistan the predicted direction of relative motion between these plates is not significantly different from that observed two of the earthquakes studied appear to be intraplate in nature the depth and focal mechanism of one intraplate event which may have occurred within the accretionary prism along the makran coast however are based on limited data the other intraplate earthquake occurred within the sedimentary deposits along the western edge of the indian subcontinent near the indian eurasian plate boundary appendix is available with entire article on microfiche order from american geophysical union 2000 florida avenue n w washington dc 20009 document b83 009 2 50 payment must accompany order

soil deformation measurement using particle image velocimetry piv and photogrammetry a deformation measurement system based on particle image velocimetry piv and close range photogrammetry has been developed for use in geotechnical testing in this paper the theory underlying this system is described and the performance is validated digital photography is used to capture images of planar soil deformation using piv the movement of a fine mesh of soil patches is measured to a high precision since piv operates on the image texture intrusive target markers need not be installed in the observed soil the resulting displacement vectors are converted from image space to object space using a photogrammetric transformation a series of validation experiments are reported these demonstrate that the precision accuracy and resolution of the system are an order of magnitude higher than previous image based deformation methods and are comparable to local instrumentation used in element testing this performance is achieved concurrent with an order of magnitude increase in the number of meas

synchronous retreat and acceleration of southeast greenland outlet glaciers 2000 06 ice dynamics and coupling to climate a large portion of the recent increase in the rate of mass loss from the greenland ice sheet is from increased outlet glacier discharge along its southeastern margin while previous investigations of the region s two largest glaciers suggest that acceleration is a dynamic response to thinning and retreat of the calving front it is unknown whether this mechanism can explain regional acceleration and what forcing is responsible for initiating rapid thinning and retreat we examine seasonal and interannual changes in ice front position surface elevation and flow speed for 32 glaciers along the southeastern coast between 2000 and 2006 while substantial seasonality in front position and speed is apparent nearly all the observed glaciers show net retreat thinning and acceleration with speed up corresponding to retreat the ratio of retreat to the along flow stress coupling length is proportional to the relative increase in speed consistent with typical ice flow and sliding laws this affirms that speed up results from loss of resistive stress at the front during retreat which leads to along flow stress transfer large retreats were often preceded by the formation of a flat or reverse sloped surface near the front indicating that subsequent retreats were influenced by the reversed bed slope many retreats began with an increase in thinning rates near the front in the summer of 2003 a year of record high coastal air and sea surface temperatures this anomaly was driven in part by recent warming suggesting that episodes of speed up and retreat may become more common in a warmer climate

effects of pile shape and pile end condition on the lateral response of displacement piles in soft clay a series of lateral tests conducted in a centrifuge on displacement piles in kaolin is used to examine the effects of pile shape pile end condition and clay overconsolidation on the lateral load t

rapid changes in ice discharge from greenland outlet glaciers using satellite derived surface elevation and velocity data we found major short term variations in recent ice discharge and mass loss at two of greenland s largest outlet glaciers their combined rate of mass loss doubled in less than a year in 2004 and then decreased in 2006 to near the previous rates likely as a result of fast re equilibration of calving front geometry after retreat total mass loss is a fraction of concurrent gravity derived estimates pointing to an alternative source of loss and the need for high resolution observations of outlet dynamics and glacier geometry for sea level rise predictions

rayleigh wave attenuation and its variation across the atlantic ocean summary fundamental mode rayleigh walies generated by several earthquakes situated on great circle paths traversing pairs of seismograph stations in american and european coastal regions and on atlantic islands have been analysed to obtain anelastic attenuation coefficients group and phase velocities and specific quality factors at periods between 15 and 100s inversions of the dispersion and attenuation data have yielded shear velocity and shear wave internal friction qj models of the upper mantle for regions of varying age in the atlantic ocean the attenuation coefficients and internal friction values can be related to the age of the atlantic ocean floor older regions being characterized by lower internal friction or higher q values a lowq zone is prominent in the upper mantle of all regions less than 65 myr in age but is poorly developed in older regions in contrast to the attenuation results no systematic variations of rayleigh or shear velocities with age can be resolved using the dispersion data of this study a comparison of internal friction models beneath the atlantic with those beneath the pacific indicates that for regions of similar age internal friction is smaller or q larger beneath the atlantic than beneath the pacific especially in the younger regions immediately contiguous with the ridges in particular the upper mantle low velocity low q zone is less prominent beneath the atlantic the fact that spreading rates of the lithospheric plates are also smaller in the atlantic suggests that internal friction and the rate of long term creep in the mantle are closely related

3d s velocity model of the lithosphere asthenosphere system beneath the bering sea the 3d s velocity structure for the bering sea region is determined from dispersion analysis rayleigh waves from which the most conspicuous features of the crust and upper mantle from 0 to 400 km depth will be revealed in the depth range from 0 to 5 km this model shows the distribution of the sedimentary basins present in the study area in terms of s velocity for the bering shelf the s velocity values decrease southward indicating the presence of deep sedimentary basins in the southern bering shelf in the depth range from 5 to 30 km the s velocity model shows clearly the division of the bering sea basin in three sub basins the aleutian basin the bowers basin and the komandorsky basin produced by the bowers ridge and the shirshov ridge in this model the low s velocity pattern determined for the bering shelf confirms that its crust is similar to a continental type crust no an oceanic crust the moho map determined in the present study from the 3d s velocity model is the first moho map calculated for the bering sea region in this map the crust beneath the bering shelf shows thicker thickness than a typical oceanic crust from which is concluded that this crust must be considered as a transitional crustal structure in the depth range from 30 to 100 km the aleutian basin shows a pattern of high s velocity that can be correlated with the origin of this basin because this basin is considered as formed by the entrapment of a piece of pacific plate in the depth range from 45 to 60 km the low s velocity pattern shown for the eastern aleutian arc is associated to the active arc volcanoes present in this region from the s velocity model the asthenosphere beneath the study area is firstly determined from 100 to 180 km depth for the depth range from 80 to 400 km the high s velocity pattern determined for the eastern aleutian arc allows the modeling imaging of the subducting pacific slab in terms of s velocity this pattern of high s velocity is not visible beneath the western aleutian arc because the pacific plate is not subducting beneath the bering sea in the western aleutian arc

variation of rayleigh wave group velocity dispersion and seismic heterogeneity of the indian crust and uppermost mantle we present group velocity dispersion results from a study of regional fundamental mode rayleigh waves propagating across the indian region 1 d path averaged dispersion measurements have been made for 1001 source receiver paths and these combined to produce tomographic images between 15 and 45 s period because of the dense station coverage in peninsular india these images have substantially higher lateral resolution for this region than is currently available from global and regional group velocity studies testing of the group velocity model shows that the average resolution across the region is about 7 5 for the periods used in this study the tomographic maps demonstrate that while the indian shield is characterized by high crustal and uppermost mantle group velocities comparatively lower velocities exist beneath the himalaya due to the thickened crust and beneath the gangetic plains caused by the mollasse sediments and recent alluvium cover in the himalayan foredeep northeastern india north of the shillong plateau also displays higher velocities similar to the south indian shield indicative of colder crust beneath the region the northern bay of bengal shows extremely low velocities due to the thick sediment blanket of the bengal fan likewise the katawaz basin in southern pakistan shows lower velocities that resemble those seen in the bay of bengal the geometry of the velocity contours south of the katawaz basin closely matches the prograding indus fan in the arabian sea finally the tibetan plateau has lower group velocities compared to the indian shield at all periods as a result of the thick crust beneath southern tibet

effects of reconsolidation time on holding capacity of deepwater dynamically installed anchors a dynamically installed anchor dia is a practical and promising type of anchor for deepwater offshore engineering currently very few research studies have reported the effects of reconsolidatio

terminus driven retreat of a major southwest greenland tidewater glacier during the early 19th century insights from glacier reconstructions and numerical modelling tidewater glaciers in greenland experienced widespread retreat during the last century information on their behaviour prior to this is often poorly constrained due to lack of observations while determining the drivers prior to instrumental records is also problematic here we present a record of the dynamics of kangiata nunaata sermia kns southwest greenland from its little ice age maximum liamax to 1859 the period before continuous air temperature observations began at nuuk in 1866 using glacial geomorphology historical accounts photographs and gis analyses we provide evidence kns was at its liamax by 1761 had retreated by 5 km by 1808 and a further 7 km by 1859 this predates retreat at jakobshavn isbrae by 43 113 years demonstrating the asynchroneity of tidewater glacier terminus response following the lia we use a one dimensional flowband model to determine the relative sensitivity of kns to atmospheric and oceanic climate forcing results demonstrate that terminus forcing rather than surface mass balance drove the retreat modelled glacier sensitivity to submarine melt rates is also insufficient to explain the retreat observed however moderate increases in crevasse water depth driving an increase in calving are capable of causing terminus retreat of the observed magnitude and timing

centrifuge experiments on the settlement of circular foundations on clay centrifuge experiments were conducted to investigate the mechanisms governing the settlement of shallow circular foundations on clay model tests were performed on both soft and firm beds of overconsolidated kaolin clay foundation loads were applied as dead weight and also through pneumatic loading a perspex window in the centrifuge package allowed digital images to be captured of a vertical cross section during and after the application of loading soil displacements deduced by particle image velocimetry piv allow deformation mechanisms to be presented for undrained penetration creep and consol idation caused by transient flow a technique is presented for discriminating consolidation settlements from the varying rates of short and long term creep the mobilizable strength design msd method is shown to make useful predictions of the undrained penetration using an estimated stress strain behaviour of the clay with allowances made for anisotropy and rate effects subsequent creep and consolidation settlements were then determined using established correlations

pipeline soil water interaction modelling for submarine landslide impact on suspended offshore pipelines the submarine landslide is one of the major geohazards in deep water oil and gas developments the impacts of glide blocks or out runner blocks which carry the geotechnical properties of the paren

the changing strength of carbonate silt parallel penetrometer and foundation tests with cyclic loading and reconsolidation periods this paper describes a centrifuge study using novel penetrometer tests t bar and piezoball and model foundation tests to explore through life changes in the strength of a reconstituted natural ca

where glaciers meet water subaqueous melt and its relevance to glaciers in various settings glacier change is ubiquitous but the fastest and largest magnitude changes occur in glaciers that terminate in water this includes the most rapidly retreating glaciers and also several advancing ones often in similar regional climate settings furthermore water terminating glaciers show a large range in morphology particularly when ice flow into ocean water is compared to that into freshwater lakes all water terminating glaciers share the ability to lose significant volume of ice at the front either through mechanical calving or direct melt from the water in contact here we present a review of the subaqueous melt process we discuss the relevant physics and show how different physical settings can lead to different glacial responses we find that subaqueous melt can be an important trigger for glacier change it can explain many of the morphological differences such as the existence or absence of floating tongues subaqueous melting is influenced by glacial runoff which is largely a function of atmospheric conditions this shows a tight connection between atmosphere oceans and lakes and glaciers subaqueous melt rates even if shown to be large should always be discussed in the context of ice supply to the glacier front to assess its overall relevance we find that melt is often relevant to explain seasonal evolution can be instrumental in shifting a glacier into a different dynamical regime and often forms a large part of a glacier s mass loss on the other hand in some cases melt is a small component of mass loss and does not significantly affect glacier response

micromorphology of diamicton affected by iceberg keel scouring scoresby sund east greenland this research was primarily funded by the university of brighton s rising stars initiative and the school of environment and technology research investment fund with supplementary funds awarded by the quaternary research association the funding sources had no involvement in study design in collection analysis and interpretation of data in the writing of the article and in the decision to submit the article for publication

anatomy of heinrich layer 1 and its role in the last deglaciation this research used data acquired at the xrf core scanner lab at the marum center for marine environmental sciences university of bremen germany this research used samples provided by the international ocean discovery program iodp funding for this research was provided by the uk natural environmental research council nerc to hodell the nerc radiocarbon facility supported two radiocarbon dates and wally broecker generously supported the remainder with funding from the comer family foundation research by rodriguez tovar and dorador was financed by project cgl2015 66835 p b m acknowledges support from the csic ramon y cajal postdoctoral programme ryc 2013 14073 j f e would like to acknowledge funding under erc advanced grant 320750 nanopaleomagnetism

effect of trapped cavity mechanism on interpretation of t bar penetrometer data in uniform clay abstractthis paper describes large deformation finite element ldfe analysis of the penetration of the t bar penetrometer in uniform clay identifying soil flow mechanisms around the t bar the ex

acceleration of jakobshavn isbrae triggered by warm subsurface ocean waters observations over past decades show a sudden switch of jakobshavn isbrae a large outlet glacier feeding a deep ocean fjord on greenland s west coast from slow thickening to rapid thinning in 1997 this switch is associated with a doubling in glacier velocity hydrographic data show a concurrent sudden increase in subsurface ocean temperatures along the entire west coast of greenland suggesting that the changes in jakobshavn isbrae were triggered by the arrival of relatively warm water originating from the irminger sea observations over the past decades show a rapid acceleration of several outlet glaciers in greenland and antarctica1 one of the largest changes is a sudden switch of jakobshavn isbrae a large outlet glacier feeding a deep ocean fjord on greenland s west coast from slow thickening to rapid thinning2 in 1997 associated with a doubling in glacier velocity3 suggested explanations for the speed up of jakobshavn isbrae include increased lubrication of the ice bedrock interface as more meltwater has drained to the glacier bed during recent warmer summers4 and weakening and break up of the floating ice tongue that buttressed the glacier5 here we present hydrographic data that show a sudden increase in subsurface ocean temperature in 1997 along the entire west coast of greenland suggesting that the changes in jakobshavn isbrae were instead triggered by the arrival of relatively warm water originating from the irminger sea near iceland we trace these oceanic changes back to changes in the atmospheric circulation in the north atlantic region we conclude that the prediction of future rapid dynamic responses of other outlet glaciers to climate change will require an improved understanding of the effect of changes in regional ocean and atmosphere circulation on the delivery of warm subsurface waters to the periphery of the ice sheets

increased mass loss and asynchronous behavior of marine terminating outlet glaciers at upernavik isstrom nw greenland in order to model and predict future behavior of marine terminating glaciers it is essential to understand the different factors that control a glaciers response to climate change here we present a detailed study of the asynchronous changes in dynamic behavior of four adjacent marine terminating glaciers at upernavik isstrom ui northwest greenland between 1992 and 2013 velocities were stable for all outlets at ui between 1992 and 2005 the northernmost glacier started to accelerate and thin in 2006 and continued to do so into 2011 after which time the velocities stabilized the second most northerly glacier started to accelerate and thin in 2009 and continued to do so until the last observations in 2013 dramatically increasing the area affected by dynamically induced thinning the southern glaciers show little change with the most southerly glacier undergoing slight retreat and deceleration between 1992 and 2013 these observations point out the fact that the ui glaciers are reacting to climate change on different timescales the asynchronous behavior of the four neighboring glaciers is explained in terms of the individual glaciers geometry and terminus position the northernmost glacier is believed to have had a floating tongue between 1985 and 2007 which disintegrated in 2007 2008 this release of back stress destabilized the glacier causing it to accelerate and thin rapidly we suggest that the ice tongue broke up due to ocean warming induced thinning in the late 1990s recent response on ui glaciers is found to be related to increased surface melt our investigations suggest that three out of the four main glaciers in the ui are likely to be in unstable positions and may have the potential to rapidly thin and accelerate and increase their contribution to sea level in the future

corrigendum strength mobilization in clays and silts the range of settlements implied by the range of m 2 in the database shown in fig 10 is calculated as 2 2 to 65 1 mm at the upper end of this range there would be serviceability concerns for most structures increasing m to 3 5 reduces this range to 0 9 25 5 mm the upper end of this range roughly corresponds to an upper limit on tolerable settlements this further underlines the finding of the paper that a large mobilization factor is needed for settlement control if no knowledge of soil stress strain behaviour is considered the authors apologise to the readers of canadian geotechnical journal for these mistakes in the original paper

ice sheet grounding zone wedges gzws on high latitude continental margins abstract grounding zone wedges gzws are asymmetric sedimentary depocentres which form through the rapid accumulation of glacigenic debris along a line source at the grounding zone of marine terminating ice sheets during still stands in ice sheet retreat gzws form largely through the delivery of deforming subglacial sediments the presence of gzws in the geological record indicates an episodic style of ice retreat punctuated by still stands in grounding zone position moraine ridges and ice proximal fans may also build up at the grounding zone during still stands of the ice margin but these require either considerable vertical accommodation space or sediment derived from point sourced subglacial meltwater streams by contrast gzws form mainly where floating ice shelves constrain vertical accommodation space immediately beyond the grounding zone an inventory of gzws is compiled from available studies of bathymetric and acoustic data from high latitude continental margins the locations and dimensions of gzws from the arctic and antarctic alongside a synthesis of their key architectural and geomorphic characteristics are presented gzws are only observed within cross shelf troughs and major fjord systems which are the former locations of ice streams and fast flowing outlet glaciers typical high latitude gzws are less than 15 km in along flow direction and 15 to 100 m thick gzws possess a transparent to chaotic acoustic character which reflects the delivery of diamictic subglacial debris many gzws contain seaward dipping reflections which indicate sediment progradation and wedge growth through continued delivery of basal sediments gzw formation is inferred to require high rates of sediment delivery to a fast flowing ice margin that is relatively stable for probably decades to centuries although the long term stability of the grounding zone is controlled by ice sheet mass balance the precise location of any still stands is influenced strongly by the geometry of the continental shelf the majority of high latitude gzws occur at vertical or lateral pinning points which encourage grounding zone stabilisation through increasing basal and lateral drag and reducing mass flow across the grounding zone

estimation of soil strength in fine grained soils by instrumented free fall sphere tests the dynamic response of a sphere in soft clay is considered through field tests in which a 0 25 m dia steel sphere was allowed to free fall in water and dynamically penetrate the underlying soft soil the test data collected in a lake and a sea environment relate to sphere velocities of up to 8 m s reaching sphere invert embedments close to ten diameters an inertial measurement unit located within the sphere measured the motion response of the sphere during free fall and penetration in soil the resulting acceleration data were used within a simple framework that accounts for both geotechnical shearing resistance and fluid mechanics drag resistance but cast in terms of a single capacity factor that can be expressed in terms of the non newtonian reynolds number the merit of the framework is demonstrated by using it as a forward model in a series of inverse analyses that calculate the undrained shear strength profile from acceleration data measured in free fall sphere tests the good match between th

pathways of meltwater export from petermann glacier greenland abstractintrusions of atlantic water cause basal melting of greenland s marine terminating glaciers and ice shelves such as that of petermann glacier in northwest greenland the fate of the resulting glacial meltwater is largely unknown it is investigated here using hydrographic observations collected during a research cruise in petermann fjord and adjacent nares strait onboard icebreaker i b oden in august 2015 a three end member mixing method provides the concentration of petermann ice shelf meltwater meltwater from petermann is found in all of the casts in adjacent nares strait with the highest concentration along the greenland coast in the direction of kelvin wave phase propagation the meltwater from petermann mostly flows out on the northeast side of the fjord as a baroclinic boundary current with the depth of maximum meltwater concentrations approximately 150 m and shoaling along its pathway at the outer sill which separates the fjord from the ambient ocean approximately 0 3 msv 1 sv

effect of perforations on uplift capacity of skirted foundations on clay the retrieval of deep water subsea installations resting on soft soil such as mudmat shallow foundations can be a difficult and costly operation if significant resistance to uplift is experienc

sermeq model produces a realistic upper bound on calving retreat for 155 greenland outlet glaciers the rate of land ice loss due to iceberg calving is a key source of variability among model projections of 21st century sea level rise it is especially challenging to account for mass loss due to

recent retreat of major outlet glaciers on novaya zemlya russian arctic influenced by fjord geometry and sea ice conditions substantial ice loss has occurred in the russian high arctic during the past decade predominantly on novaya zemlya yet the region has been studied relatively little consequently the factors forcing mass loss and the relative contribution of ice dynamics versus surface melt are poorly understood here we evaluate the influence of atmospheric oceanic forcing and variations in fjord width on the behaviour of 38 glaciers on the northern ice cap novaya zemlya we compare retreat rates on land versus marine terminating outlets and on the kara versus barents sea coasts between 1992 and 2010 90 of the study glaciers retreated and retreat rates were an order of magnitude higher for marine terminating outlets 52 1 m a 1 than for land terminating glaciers 4 8 m a 1 we identify a post 2000 acceleration in marine terminating glacier retreat which corresponded closely to changes in sea ice concentrations retreat rates were higher on the barents sea coast which we partly attribute to lower sea ice concentrations but varied dramatically between individual glaciers we use empirical data to categorize changes in along flow fjord width and demonstrate a significant relationship between fjord width variability and retreat rate results suggest that variations in fjord width exert a major influence on glacier retreat

mapping the grounding zone of the ross ice shelf antarctica using icesat laser altimetry we use laser altimetry from the ice cloud and land elevation satellite icesat to map the grounding zone gz of the ross ice shelf antarctica at 491 locations where icesat tracks cross the grounding line gl ice flexure in the gz occurs as the ice shelf responds to short term sea level changes due primarily to tides icesat repeat track analysis can be used to detect this region of flexure since each repeated pass is acquired at a different tidal phase the technique provides estimates for both the landward limit of flexure and the point where the ice becomes hydrostatically balanced we find that the icesat derived landward limits of tidal flexure are in many places offset by several km and up to 60 km from the gl mapped previously using other satellite methods we discuss the reasons why different mapping methods lead to different gl estimates including instrument limitations variability in the surface topographic structure of the gz and the presence of ice plains we conclude that reliable and accurate mapping of the gl is most likely to be achieved when based on synthesis of several satellite datasets

seafloor spreading magnetic anomalies in the southeastern arabian sea abstract study of closely spaced new marine magnetic profiles in the southeastern arabian sea has enabled fairly confident identification of e w trending linear magnetic anomalies 24 through 20 these magnetic lineations are consistently right laterally offset along numerous fracture zones and extend eastwards up to the base of the western slopes of the laccadive ridge obliteration of magnetic lineations further eastward is attributed to the emplacement of volcanic material of the laccadive ridge over the pre existing oceanic crust dsdp site 221 is observed to be located on the reversely magnetized oceanic crust between anomalies 22 and 21 which provide a reliable age constraint 48 myr for the oceanic crust at this site the presence of additional unidentifiable normal magnetic anomalies suggests a relatively complex spreading pattern ridge jump in the vicinity of the laccadive ridge during the interval of anomalies 24 and 23

quantifying flow regimes in a greenland glacial fjord using iceberg drifters funded by the national science foundation grant numbers oce 1130008 arc 0909274 and the university of oregon

cavity expansion model for the bearing capacity and settlement of circular shallow foundations on clay the use of an ellipsoidal cavity expansion model to estimate the bearing capacity and settlement of circular shallow foundations on clay is presented the model uses an upper bound energy approach with contours of constant soil displacement taken to be ellipsoidal within a hemispherical outer boundary the elastic and plastic work done within the soil are equated to the footing work with yield being defined using the von mises yield criterion it is shown that for two different soil rigidities results are consistent with those obtained from finite element analyses available in the literature a relationship between the bearing stress on a circular shallow foundation and its normalised settlement is developed with an expression provided for the linear working range

ocean regulation hypothesis for glacier dynamics in southeast greenland and implications for ice sheet mass changes synchronous acceleration and thinning of southeast se greenland glaciers during the early 2000s was the main contributor that resulted in the doubling of annual discharge from the ice sheet we show that this acceleration was followed by a synchronized and widespread slowdown of the same glaciers in many cases associated with a decrease in thinning rates and we propose that ice sheet ocean interactions are the first order regional control on these recent mass changes sea surface temperature and mooring data show that the preceding dynamic thinning coincides with a brief decline in the cold east greenland coastal current egcc and east greenland current we suggest this decline was partly induced by a reduction in ice sheet runoff which allowed warm water from the irminger current to reach the se greenland coast a restrengthening of the cold waters coincides with the glaciers subsequent slowdown we argue that this warming and subsequent cooling of the coastal waters was the cause of the glaciers dynamic changes we further suggest that the restrengthening of the egcc resulted in part from cold water input by increased glacier calving during the speedup and increased ice sheet runoff we hypothesize that the main mechanism for ice sheet mass loss in se greenland is highly sensitive to ocean conditions and is likely subject to negative feedback mechanisms copyright 2010 by the american geophysical union

early spreading and continental to oceanic basement transition beneath the indus deep sea fan northeastern arabian sea abstract a seismic survey to study the indus deep sea fan penetrated into basement this enabled the mapping of basement structures and a description of the geodynamical evolution of a part of the northeastern arabian sea the main tectonic structure of the basement is an e w graben gop rift with a prominent central e w horst the palitana horst this rift is cut obliquely by several ne sw faults large e w magnetic anomalies are not the continuation of the magnetic anomaly sequence of the oceanic arabian basin however these anomalies are linked to inverse magnetisation in the crust suggesting that the rift is either underlain by stretched continental crust intruded by linear volcanic bodies related to the deccan traps or by oceanic crust older than chron 28 64 ma as proposed in the laxmi basin southeastwards accompanying these structures ne sw faults with a strike slip pattern may have played the role of transform direction during the separation of the laxmi ridge from the indian continent we propose that rifting and oceanic spreading have occurred around a triple junction connecting the oceanic laxmi basin the narmada son lineament and the gop rift this phase preceded oceanic spreading in the arabian basin this interpretation is in agreement with the previously proposed initial separation of india and the seychelles before chron 28 the laxmi ridge could be a part of the seychelles microplate subsequently left attached to india

changes in the dynamics of marine terminating outlet glaciers in west greenland 2000 2009 1 recent changes in the dynamics of greenland s marine terminating outlet glaciers indicate a rapid and complex response to external forcing despite observed ice front retreat and recent geophysical evidence for accelerated mass loss along greenland s northwestern margin it is unclear whether west greenland glaciers have undergone the synchronous speed up and subsequent slow down as observed in southeastern glaciers earlier in the decade to investigate changes in west greenland outlet glacier dynamics and the potential controls behind their behavior we derive time series of front position surface elevation and surface slope for 59 marine terminating outlet glaciers and surface speeds for select glaciers in west greenland from 2000 to 2009 using these data we look for relationships between retreat thinning acceleration and geometric parameters to determine the first order controls on glacier behavior our data indicate that changes in front positions and surface elevations were asynchronous on annual time scales though nearly all glaciers retreated and thinned over the decade we found no direct relationship between retreat acceleration and external forcing applicable to the entire region in regard to geometry we found that following retreat 1 glaciers with grounded termini experienced more pronounced changes in dynamics than those with floating termini and 2 thinning rates declined more quickly for glaciers with steeper slopes overall glacier geometry should influence outlet glacier dynamics via stress redistribution following perturbations at the front but our data indicate that the relative importance of geometry as a control of glacier behavior is highly variable throughout west greenland

submarine landforms reveal varying rates and styles of deglaciation in north west greenland fjords during this work c l batchelor was in receipt of a junior research fellowship at newnham college cambridge the bathymetric data that was collected during jr175 of the rrs james clark ross to west greenland in 2009 was funded by natural environment research council nerc grant ne d001951 1 to c o cofaigh

axial sliding resistance of partially embedded offshore pipelines this paper presents the results of centrifuge model tests and three dimensional large deformation finite element analysis on axial pipe soil sliding behaviour of partially embedded subsea pipelines

influence of sea ice decline atmospheric warming and glacier width on marine terminating outlet glacier behavior in northwest greenland at seasonal to interannual timescales 1 discharge from marine terminating outlet glaciers represents a key component of the greenland ice sheet mass budget and observations suggest that mass loss from northwest greenland has recently accelerated despite this the factors controlling outlet glacier dynamics within this region have been comparatively poorly studied here we use remotely sensed data to investigate the influence of atmospheric oceanic and glacier specific controls on the frontal position of alison glacier ag northwest greenland and nine surrounding outlet glaciers ag retreated by 9 7 km between 2001 and 2005 following at least 25 years of minimal change results suggest that sea ice and air temperatures influence glacier frontal position at seasonal and interannual timescales however the response of individual outlet glaciers to forcing was strongly modified by factors specific to each glacier specifically variations in fjord width and terminus type overall our results underscore the need to consider these factors in order to interpret recent rapid changes and predict the dynamic response of marine terminating outlet glaciers to atmospheric and oceanic forcing