characteristics of the antarctic surface mass balance 1958 2002 using a regional atmospheric climate model temporal and spatial characteristics of the antarctic specific surface mass balance ssmb are presented including its components solid precipitation sublimation deposition and melt for this purpose we use the output of a regional atmospheric climate model racmo2 ant horizontal resolution of 55 km for the period 1958 2002 racmo2 ant uses european centre for medium range weather forecasts ecmwf 40 year re analysis era 40 fields as forcing at the lateral boundaries racmo2 ant underestimates ssmb in the high interior of east and west antarctica and overestimates ssmb on the steep coastal slopes otherwise the modeled spatial pattern of ssmb is in good qualitative agreement with recent compilations of in situ observations large scale patterns like the precipitation shadow effect of the antarctic peninsula are well reproduced and mesoscale ssmb patterns such as the strong precipitation gradients on law dome are well represented in the model the integrated ssmb over the grounded ice sheet is 153mmw e a 1 for the period 1958 2002 which agrees within 5 with the latest measurement compilations sublimation and melt remove 7 and

mass changes of the greenland and antarctic ice sheets and shelves and contributions to sea level rise 1992 2002 changes in ice mass are estimated from elevation changes derived from 10 5 years greenland and 9 years antarctica of satellite radar altimetry data from the european remote sensing satellites ers 1 and 2 for the first time the dh dt values are adjusted for changes in surface elevation resulting from temperature driven variations in the rate of firn compaction the greenland ice sheet is thinning at the margins 42 2g t a 1 below the equilibrium line altitude ela and growing inland 53 2g t a 1 above the ela with a small overall mass gain 11 3g t a 1 0 03 mm a 1 sle sea level equivalent the ice sheet in west antarctica wa is losing mass 47 4g t a 1 and the ice sheet in east antarctica ea shows a small mass gain 16 11 gt a 1 for a combined net change of 31 12 gt a 1 0 08 mm a 1 sle the contribution of the three ice sheets to sea level is 0 05 0 03 mm a 1 t he antarctic ice shelves show corresponding mass changes of 95 11 gt a 1 in wa and 142 10 gt a 1 in ea thinning at the margins of the greenland ice sheet and growth at higher elevations is an expected response to increasing temperatures and precipitation in a warming climate the marked thinnings in the pine island and thwaites glacier basins of wa and the totten glacier basin in ea are probably ice dynamic responses to long term climate change and perhaps past removal of their adjacent ice shelves the ice growth in the southern antarctic peninsula and parts of ea may be due to increasing precipitation during the last century

thermal history of australian passive margin cover sequences accreted to timor during late neogene arc continent collision indonesia abstract paleotemperature indicators and apatite fission track analysis of australian continental margin cover sequences accreted to the active banda arc continent collision indicate little to no heating during rapid late neogene uplift and exhumation thermal maturation patterns of vitrinite reflectance conodont alteration and illite crystallinity show that peak paleotemperatures ppt increase with stratigraphic and structural burial the highest ppt is found in the northern hinterland of the accretionary wedge which was beneath progressively thicker parts of the upper plate towards the north major discontinuities in the pattern of ppt are associated with the position of major thrust ramps such as those forming the ramelau kekneno arch rka ppt for upper triassic to neogene strata south of the rka are 60 80 c which are similar to and in many cases lower than correlative and age equivalent units drilled on the nw australian shelf permian to lower triassic sedimentary strata thrust over younger units within and north of the rka have ppt of 100 220 c thrust sheets accreted beneath the upper plate have ppt approximately 90 c higher than those frontally accreted metamorphism of the northernmost units of these sequences yield ppt of 300 c thrust stacking yields an inverted thermal profile of ppt decreasing discontinuously downward and to the south towards the foreland the timing of ppt is constrained by apatite fission track ages from mostly triassic continental margin cover sequences ages of upper triassic units are primarily coeval with deposition and show little evidence of thermal annealing whereas those of lower triassic units are almost completely annealed and range from 1 8 0 5 19 2 9 7 ma the clustering of apatite fission track ages into two distinct groups indicates that the upper boundary of the partial annealing zone has remained for some time at a triassic stratigraphic interval in the slope and rise of the nw australian continental margin the position of this zone on the present shelf is higher in the stratigraphic column due to the greater thickness of post breakup shelf facies units thrust stacking of rise slope and shelf units produces an inverted vertical profile of increasing apatite fission track age with depth lack of any long confined track lengths in apatite from all of the units requires rapid and recent exhumation of the thrust stack which is coincident with rapid phases of pliocene pleistocene exhumation documented throughout timor these data preclude pre late miocene tectonic burial or pre pliocene exhumation of the nw australian continental margin

a new perspective on southern hemisphere storm tracks abstract a detailed view of southern hemisphere storm tracks is obtained based on the application of filtered variance and modern feature tracking techniques to a wide range of 45 yr european centre for medium range weather forecasts ecmwf re analysis era 40 data it has been checked that the conclusions drawn in this study are valid even if data from only the satellite era are used the emphasis of the paper is on the winter season but results for the four seasons are also discussed both upper and lower tropospheric fields are used the tracking analysis focuses on systems that last longer than 2 days and are mobile move more than 1000 km many of the results support previous ideas about the storm tracks but some new insights are also obtained in the summer there is a rather circular strong deep high latitude storm track in winter the high latitude storm track is more asymmetric with a spiral from the atlantic and indian oceans in toward antarctica and a subtropical jet related lower latitu

storm tracks in the southern hemisphere abstract from 1979 to 1989 global european centre for medium range weather forecasts ecmwf analyses of many meteorological variables important in baroclinic storms have been bandpass filtered to highlight fluctuations on 2 to 8 day time scales in order to illuminate the relationships among the variables in baroclinic storm track regions because of the greater zonal symmetry in the southern hemisphere sh versus the northern hemisphere nh it is possible to examine these relationships over a zonal sector without being dominated by local effects associated with jet stream entrance and exit regions of the storm tracks the bandpassed variance of geopotential height is used to define the storm track and its meridional profile has a pronounced midlatitude maximum in the sh the locations of the jet stream and the variance maxima of meridional and zonal velocity components vorticity vertical motion specific humidity and temperature all bear a distinctive relationship to the storm track but the lat

coupling of mantle temperature anomalies and the flow pattern in the core interpretation based on simple convection calculations abstract the association of some relatively stationary features of the magnetic field at the core mantle boundary cmb with temperature anomalies in the deep mantle inferred from seismic tomography has led to the speculation that flow in the core is locked to thermal anomalies in the mantle with downwellings upwellings in the core lying below cold hot anomalies in the lower mantle bloxham and gubbins the relatively large temperature anomalies in the mantle act to control the heat flux out of the core with high heat flux into colder than average mantle and low perhaps negative heat flux into regions of hotter than average mantle we use a simple two dimensional internally heated convection model in a cartesian geometry with varying thermal boundary conditions to investigate this problem the relationship between upwellings downwellings and maxima minima in surface heat flux depends upon the thermal boundary condition with maximum heat flux sometimes associated with upwellings sometimes downwellings and sometimes neither however for moderate rayleigh numbers large aspect ratio geometries and large variations in heat flux the bloxham and gubbins hypothesis is supported

climate links and recent extremes in antarctic sea ice high latitude cyclones southern annular mode and enso in this article we study the climate link between the southern annular mode sam and the southern sea ice extent sie and discuss the possible role of stationary waves and synoptic eddies in establishing this link in doing so we have used a combination of techniques involving spatial correlations of sie eddy streamfunction and wind anomalies and statistics of high latitude cyclone strength it is suggested that stationary waves may be amplified by eddy anomalies associated with high latitude cyclones resulting in more sea ice when the sam is in its positive phase for most but not all longitudes a similar association is observed during enso la nina years although this synergy in the sam enso response may partially reflect preferential areas for wave amplification around antarctica the short extent of the climate records does not allow for a definite causality connection to be established with sie stronger polar cyclones are observed over the areas where the stationary waves are amplified these deeper cyclones will break up and export ice equatorward more efficiently but the near coastal regions are cold enough to allow for a rapid re freeze of the resulting ice break up we speculate that if global warming continues this same effect could help reverse the current positive antarctic sie trends once the ice gets thinner similarly to what has been observed in the northern hemisphere

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

synoptic activity in the seas around antarctica abstract the recent ncep department of energy doe reanalysis 2 update of the original ncep ncar dataset provides what is arguably the highest quality analyses spanning two decades available for the high southern latitudes it therefore offers an excellent starting point from which to assemble a modern comprehensive and reliable picture of synoptic activity in the subantarctic region this set covering the modern satellite era from january 1979 to february 2000 is used herein in addition the exploration in this study has been conducted with sophisticated feature tracking and trajectory analysis software it is shown that the high southern latitude cyclone system density is greatest in the indian ocean and to the south of australia near or to the south of 60 s the numbers in winter exceed those in summer except over a few but important regions such as the bellingshausen sea the antarctic coastal region is confirmed as one of high cyclonicity as is that in the northern part of the antarctic

orogeny and orography the effects of erosion on the structure of mountain belts a numerical model of the coupled processes of tectonic deformation and surface erosion in convergent orogens is developed to investigate the nature of the interaction between these processes crustal deformation is calculated by a two dimensional finite element model of deformation in response to subduction and accretion of continental crust erosion operates on the uplifted surface of this model through fluvial incision which is taken to be proportional to stream power the relative importance of the tectonic and erosion processes is given by a dimensionless erosion number relating convergence velocity rock erodibility and precipitation rate this number determines the time required for a system to reach steady state and the final topographic shape and size of a mountain belt fundamental characteristics of the model orogens include asymmetric topography with shallower slopes facing the subducting plate and an asymmetric pattern of exhumation with the deepest levels of exhumation opposite to subduction these characteristics are modified when the regional climate exhibits a dominant wind direction and orographically enhanced precipitation on one side of the mountain belt the two possible cases are dominant wind in the direction of motion of the subducting plate and dominant wind direction in the opposite direction of the subducting plate velocity models of the former case predict a broad zone of exhumation with maximum exhumation in the orogen interior models of the latter case predict a focused zone of exhumation at the margin of the orogen and at high erosion number a reversal in the topographic asymmetry natural examples of these two cases are presented the southern alps of new zealand exhibits the climate and exhumation asymmetry characteristic of wind in the direction opposite to motion of the subducting plate the asymmetry of topography suggests that erosion is not efficient enough to have reversed the topographic asymmetry the contrasting example of dominant wind in the direction of subduction motion is provided by the olympic mountains of washington state in this case exhumation of deep levels of the cascadia accretionary wedge shows a broad domal pattern consistent with the observed orographic precipitation

apatite fission track analysis apatite fission track aft analysis has been widely used during the past 30 years to constrain the low temperature thermal histories of many igneous metamorphic and sedimentary rocks in a wide range of geological settings applicable geological settings include orogenic belts rifted margins faults sedimentary basins cratons and mineral deposits the types of geologic problems that can be addressed include the timing and rates of tectonic events sedimentary basin evolution the timing of hydrocarbon generation and ore mineralization the absolute age of volcanic deposits the effects of major climatic changes on the near surface geothermal gradient and long term landscape evolution early work by naeser 1967 and wagner 1968 1969 first established the basic procedures that enabled the fission track dating method to be applied routinely to these geologic problems fleischer et al 1975 summarized the early studies of the broader discipline of nuclear track detection in different solid state materials more recent comprehensive overviews of fission track applications have been provided by naeser and mcculloh 1989 wagner and van den haute 1992 gallagher et al 1998 van den haute and de corte 1998 dumitru 2000 and gleadow et al 2002 etched natural fission tracks in several apatite grains are shown in figure 1 successful aft analysis is limited by the following 1 the availability of apatite from which useful aft data can be obtained often due to a lack of apatite of sufficient grain size and quality within available rock types or alternatively the lack of available rock samples due to minimal outcrop exposure or other reasons 2 economic considerations in terms of the time and money required to obtain sufficient aft data 3 the inherent limitations of aft data to resolve geological thermal history information often related to limited numbers of accumulated spontaneous fission tracks due to

paleobathymetry in the backstripping procedure correction for oxygenation effects on depth estimates abstract this paper aims to provide a straightforward and easily applicable method for estimating the depositional depth evolution of marine basins vertical movements of the basin floor can be reconstructed from the sedimentary record and more accurately constrained when information from the sedimentary history is combined with palaeodepth estimates derived from fauna to this end we propose to extend an existing method based on the percentage of planktonic foraminifera with respect to the total planktonic and benthic foraminiferal association which is expressed as the percentage planktonics p the ratio between planktonic and benthic foraminifera is related to water depth and the p generally increases with increasing distance to shore however next to water depth the oxygen level of bottom waters has a profound effect on the abundance of benthic foraminifera and as such influences the p depending on basin configuration the oxygen level at the sea floor can vary on milankovitch time scales and is reflected by the fraction of benthic foraminiferal species that indicate an effect of oxygen stress on the biotic system these species can be used as stress markers and their percentage with respect to the total benthic population is here expressed as s to assess whether the effect of sea floor oxygenation impairs depth reconstructions we studied the percentage of planktonic foraminifera p in five well dated sedimentary successions from the lower pliocene of crete corfu and milos in greece additionally we assessed whether different foraminiferal size fractions and counting methods affect the determination of the percentage of planktonic foraminifera the palaeobathymetric evolution calculated for each basin was confirmed for all successions by an independent check on depth related occurrences of benthic foraminifera after correction for bathymetry changes of the basin due to sedimentation compaction and eustatic sea level variations the vertical movement history of the basin floor was inferred we propose a standard methodology for reconstructions of palaeobathymetry of marine sedimentary successions from foraminiferal associations

observed relationships between the el nino southern oscillation and the extratropical zonal mean circulation abstract there is increasing evidence indicating that the climate response to variations in the el nino southern oscillation enso includes not only thermally forced zonal wind anomalies in the subtropics but also eddy driven zonal wind anomalies that extend into the mid high latitudes of both hemispheres in this study new insights into the observed seasonally varying signature of enso in the extratropical zonal mean circulation are provided and the associated linkages with the dominant patterns of extratropical variability are examined the zonal mean extratropical atmospheric response to enso is characterized by two principal features an equivalent barotropic dipole in the southern hemisphere sh zonal mean zonal flow with centers of action located near 40 and 60 during austral summer and a weaker but analogous dipole in the northern hemisphere nh with centers of action located near 25 and 45 during early and late boreal winter both structures are accompanied by eddy momentum flux ano

a reconciled estimate of ice sheet mass balance we combined an ensemble of satellite altimetry interferometry and gravimetry data sets using common geographical regions time intervals and models of surface mass balance and glacial isostatic adjustment to estimate the mass balance of earth s polar ice sheets we find that there is good agreement between different satellite methods especially in greenland and west antarctica and that combining satellite data sets leads to greater certainty between 1992 and 2011 the ice sheets of greenland east antarctica west antarctica and the antarctic peninsula changed in mass by 142 49 14 43 65 26 and 20 14 gigatonnes year 1 respectively since 1992 the polar ice sheets have contributed on average 0 59 0 20 millimeter year 1 to the rate of global sea level rise

increasing rates of ice mass loss from the greenland and antarctic ice sheets revealed by grace 1 we use monthly measurements of time variable gravity from the grace gravity recovery and climate experiment satellite gravity mission to determine the ice mass loss for the greenland and antarctic ice sheets during the period between april 2002 and february 2009 we find that during this time period the mass loss of the ice sheets is not a constant but accelerating with time i e that the grace observations are better represented by a quadratic trend than by a linear one implying that the ice sheets contribution to sea level becomes larger with time in greenland the mass loss increased from 137 gt yr in 2002 2003 to 286 gt yr in 2007 2009 i e an acceleration of 30 11 gt yr2 in 2002 2009 in antarctica the mass loss increased from 104 gt yr in 2002 2006 to 246 gt yr in 2006 2009 i e an acceleration of 26 14 gt yr2 in 2002 2009 the observed acceleration in ice sheet mass loss helps reconcile grace ice mass estimates obtained for different time periods

deformation and metamorphism of the aileu formation north coast east timor and its tectonic significance abstract the large block of metamorphic rocks along the north coast of east timor is of special interest as it occurs at the boundary between continental and oceanic crust in an island arc continent collision zone a detailed study of the structure and metamorphic history of 400 km2 of this formation showed it has a complex history of penetrative deformation but the structure is coherent pelites psammites and limestones interlayered with dolerites and amphibolites have been metamorphosed in a medium pressure environment they now form a metamorphic province zoned from low greenschist facies in the southwest to upper amphibolite facies in the east the earliest recognised deformation phase predated the metamorphism and produced a widespread layer parallel schistosity but no recognisable folds the second deformation phase post dated the metamorphic maximum and micropetrological evidence indicates a gradual cooling during this event this deformation produced tight folds with an axial plane schistosity and transposed the earlier structures the progressively weaker third and fourth phases developed crenulation cleavages and related folds under greenschist facies conditions open fifth phase macroscopic folds were probably synchronous with strike slip faulting parallel to the north coast later dip slip faulting juxtaposed the aileu formation with permian and mesozoic sediments of very low metamorphic grade reconnaissance k ar radiometric dating using hornblende and biotite showed the prograde metamorphic maximum occurred before 11 ma ago and implies that the second and strongest deformation phase occurred in the late miocene this young age establishes the relationship of the deformation events to the collision between australia and the inner banda arc the proposed models for the structure of timor must be modified to fit the deformation history of the aileu formation if timor is essentially autochthonous the aileu formation was probably deposited in a palaeozoic graben and the metamorphic maximum may have occurred in the jurassic the overthrusting models must be modified in the light of the close correlation in time between penetrative deformation and emplacement of the proposed thrust sheets the analogy proposed between timor and normal convergent margins is not supported but it may be possible to draw analogies with the molucca sea

resolving spatial heterogeneities in exhumation and surface uplift in timor leste constraints on deformation processes in young orogens although exhumation and surface uplift are important parameters in understanding orogenesis the opportunity to measure both in close proximity is rare in timor leste east timor deeply exhumed metamorphic rocks and piggyback deepwater synorogenic basins are only tens of kilometers apart permitting direct relation of uplift and exhumation by comparing micropaleontology to thermochronology interpreted through one dimensional thermal modeling foraminifera in two deepwater synorogenic basins suggest basin uplift from depths of 1 2 km to depths of 350 1000 m between 3 35 and 1 88 ma thermochronologic sampling was conducted in the central mountain belt between these basins of four muscovite 40ar 39ar samples one provides a reset age of 7 13 0 25 ma in the aileu high grade belt that suggests 9 16 km of exhumation since that time eighteen zircon u th he samples contain a group of reset ages in the aileu complex ranging from 4 4 to 1 5 ma which suggest exhumation rates of 1 0 3 1 mm yr with 2 7 7 8 km of exhumation since these ages thirteen apatite u th he ages in the gondwana sequence range from 5 5 to 1 4 ma suggesting 1 2 km of exhumation and defining a pattern of exhumation rates ranging from 0 2 to 1 3 mm yr that positively correlates with average annual rainfall seven apatite fission track samples display varying degrees of partial resetting with greatest resetting where apatite u th he ages are youngest together these data demonstrate extreme variability in surface uplift and exhumation over small spatial scales we propose ongoing subsurface duplexing driven by subduction and underplating of australian continental crust as the predominant driver for surface uplift and uplift induced exhumation

the effects of enhanced sea ice export from the ross sea on recent cooling and freshening of the southeast pacific abstractthe top 2000 m of the southern ocean has freshened and warmed over recent decades however the high latitude south of 50 s southeast pacific was observed to be cooler and fresher in the

the structural evolution of the timor collision complex eastern indonesia abstract the structural style of timor is consistent with foreland fold belt processes and zones of frontal accretion and underplating can be recognized in the australian parautochthonous sequence the parautochthon is overlain by an allochthonous sequence which corresponds to the pre collisional oceanic forearc in northern timor the parautochthon has been underplated directly beneath the allochthonous basement unlike previous interpretations of timor in terms of foreland fold belt processes the timor foldbelt is here interpreted as having evolved in a fairly straightforward way from the pre collisional forearc by the sequential addition of thrust slices of australian continental crust to the front and base of the developing collision complex

rapid pliocene uplift of timor palynology of exhumed pliocene marine turbidites and marl beds on the island of timor provide insights into crustal deformation in the indonesian region between ca 4 5 and ca 3 ma palynomorphs were sourced primarily from australia and new guinea with increasing swamp and mangrove elements sourced from an emerging proto timor following ca 3 1 ma pollen and charcoal evidence track the rapid uplift of timor to a high island with the progressive appearance of montane and dry lee side floristic elements early to mid pliocene uplift rates of 0 5 0 6 mm yr 1 increased to 2 5 mm yr 1 in the latest pliocene the rapid topographic development of timor leste initiated earlier but followed a pattern similar to that of more westerly localities in the timor sector of the banda arc timor s emergence from the marine environment is closely correlated with the timing of closure of the indonesian seaway to deep dwelling foraminfera

surface deformation and slab mantle interaction during banda arc subduction rollback the reason for the spectacular curvature of the banda subduction zone is debated tomographic images and plate reconstructions reveal subduction of a single slab the ancient geometry of the australian plate as well as the interaction between the slab and the mantle caused the deformation of the slab the spectacularly curved banda arc comprises young oceanic crust1 2 enclosed by a volcanic inner arc outer arc islands and a trough parallel to the australian continental margin3 4 5 strong seismic activity in the upper mantle defines a folded surface6 7 for which there are two contrasting explanations deformation of a single slab5 8 or two separate slabs subducting from the north and south6 9 here we combine seismic tomography with the plate tectonic evolution of the region to infer that the banda arc results from subduction of a single slab our palaeogeographic reconstruction shows that a jurassic embayment which consisted of dense oceanic lithosphere enclosed by continental crust once existed within the australian plate banda subduction began about 15 million years ago when active java subduction tore eastwards into the embayment the present morphology of the subducting slab is only partially controlled by the shape of the embayment as the australian plate moved northward at a high speed of about 7 cm yr 1 the banda oceanic slab rolled back towards the south southeast accompanied by active delamination separating the crust from the denser mantle increasing resistance of the mantle to plate motion progressively folded the slab and caused strong deformation of the crust the banda arc represents an outstanding example of large scale deformation of the earth s crust in response to coupling between the crust slab and surrounding mantle

atmospheric meridional moisture flux over the southern ocean a story of the amundsen sea abstractthe antarctic ice sheet constitutes the largest reservoir of freshwater on earth representing tens of meters of sea level rise if it were to melt completely however because of the remote location of the continent and the concomitant sparse data coverage much remains unknown regarding the climate variability in antarctica and the surrounding southern ocean this study uses the high resolution ecmwf interim re analysis era interim data during 1979 2010 to calculate the meridional moisture transport associated with the mean circulation planetary waves and synoptic scale systems the resulting moisture flux which is dominated by the synoptic scales is largely consistent with results from theoretical assumptions and previous studies here high interannual and regional variability in the total meridional moisture flux is found with no significant trend over the last 30 years further the variability of the meridional moisture flux cannot be explained by the southern annular mode or el nino

the role of atmospheric rivers in anomalous snow accumulation in east antarctica recent heavy snow accumulation events over dronning maud land dml east antarctica contributed significantly to the antarctic ice sheet surface mass balance smb here we combine in situ accumulation measurements and radar derived snowfall rates from princess elisabeth station pe located in the dml escarpment zone along with the european centre for medium range weather forecasts interim reanalysis to investigate moisture transport patterns responsible for these events in particular two high accumulation events in may 2009 and february 2011 showed an atmospheric river ar signature with enhanced integrated water vapor iwv concentrated in narrow long bands stretching from subtropical latitudes to the east antarctic coast adapting iwv based ar threshold criteria for antarctica by accounting for the much colder and drier environment we find that it was four and five ars reaching the coastal dml that contributed 74 80 of the outstanding smb during 2009 and 2011 at pe therefore accounting for ars is crucial for understanding east antarctic smb

measurements of time variable gravity show mass loss in antarctica using measurements of time variable gravity from the gravity recovery and climate experiment satellites we determined mass variations of the antarctic ice sheet during 2002 2005 we found that the mass of the ice sheet decreased significantly at a rate of 152 80 cubic kilometers of ice per year which is equivalent to 0 4 0 2 millimeters of global sea level rise per year most of this mass loss came from the west antarctic ice sheet

rapid late miocene rise of the bolivian altiplano evidence for removal of mantle lithosphere abstract the oxygen isotopic compositions of carbonates deposited in the northern altiplano demonstrate a rapid change in late miocene time which we attribute to an increase in elevation rainfall samples over an elevation transect adjacent to the altiplano of northern bolivia display a systematic decrease in mean annual 18 o values and define a local 18 o vs altitude gradient r gonfiantini m a roche j c olivry j c fontes g m zuppi the altitude effect on the isotopic composition of tropical rains chem geol 181 2001 147 167 which we apply to paleo meteoric water values determined from carbonates age constraints from magnetostragraphy and paleoelevation estimates suggest surface uplift of 2 5 to 3 5 km occurred between 10 3 ma and 6 8 0 4 ma when the altiplano rose to its current elevation only the removal of dense eclogitic lower crust and mantle lithosphere can generate a change of this magnitude and rapidity this change coincides with an 30 decrease in the rate of convergence between the south america and nazca plates and the propagation of deformation into the eastern subandean zone which we infer to have resulted from the increase in the force per unit length applied by the elevated andean plateau to the surrounding lowlands

a climatological analysis of high precipitation events in dronning maud land antarctica and associated large scale atmospheric conditions the link between high precipitation in dronning maud land dml antarctica and the large scale atmospheric circulation is investigated using era interim data for 1979 2009 high precipitation events are analyzed at halvfarryggen situated in the coastal region of dml and at kohnen station located in its interior this study further includes a comprehensive comparison of high precipitation in era interim with precipitation data from the antarctic mesoscale prediction system amps and snow accumulation measurements from automatic weather stations awss with the limitations of such a comparison being discussed the era interim and amps precipitation data agree very well however the correspondence between high precipitation in era interim and high snow accumulation at the awss is relatively weak high precipitation events at both halvfarryggen and kohnen are typically associated with amplified upper level waves this large scale atmospheric flow pattern is preceded by the downstream development of a rossby wave train from the eastern south pacific several days before the precipitation event at the surface a cyclone located over the weddell sea is the main synoptic ingredient for high precipitation both at halvfarryggen and at kohnen a blocking anticyclone downstream is not a requirement for high precipitation per se but a larger share of blocking occurrences during the highest precipitation days in dml suggests that these blocks strengthen the vertically integrated water vapor transport ivt into dml a strong link between high precipitation and the ivt perpendicular to the local orography suggests that ivt could be used as a proxy for high precipitation in particular over dml s interior

snow accumulation variability over the west antarctic ice sheet since 1900 a comparison of ice core records with era 20c reanalysis this study uses a set of 37 firn core records over the west antarctic ice sheet wais to test the performance of the twentieth century from the european centre for medium range weather forecasts era 20c reanalysis for snow accumulation and quantify temporal variability in snow accumulation since 1900 the firn cores are allocated to four geographical areas demarcated by drainage divides i e antarctic peninsula ap western wais central wais and eastern wais to calculate stacked records of regional snow accumulation our results show that the interannual variability in era 20c precipitation minus evaporation p e agrees well with the corresponding ice core snow accumulation composites in each of the four geographical regions suggesting its skill for simulating snow accumulation changes before the modern satellite era pre 1979 snow accumulation experiences significantly positive trends for the ap and eastern wais a negative trend for the western wais and no significant trend for the central wais from 1900 to 2010 the contrasting trends are associated with changes in the large scale moisture transport driven by a deepening of the low pressure systems and anomalies of sea ice in the amundsen sea low region

deformation and exhumation in timor distinct stages of a young orogeny abstract timor island in the outer banda arc bordering the timor sea preserves the orogenic product of an arc continent collision between the australian plate and the banda arc that commenced after 10 9 9 8 ma gts2004 but emerged above sea level only 3 1 ma ago the orogenic pile includes large tracts of material from the australian margin including the permian to middle jurassic gondwana megasequence and the late jurassic to early late miocene australian margin megasequence which occur in thrust slices in addition material from the banda arc side of the plate margin referred to as the banda terrane occurs throughout the island and includes both seafloor metamorphosed igneous material and cover sediments also in thrust sheets however the distribution of thrust slices is unclear in many areas perhaps because only the uppermost nappes of the thrust pile are currently emergent and also because the thrust piles have been disrupted by later high angle faulting evidence from east timor suggests that the major break between deformed pre collisional strata and the relatively undeformed overlying deposits was during the late miocene 9 8 5 5 ma we present evidence for the timing of three distinct phases of orogenic development as determined from east timor including initial collision and emplacement of the early nappes creating loading and diapirism within the 9 8 5 5 ma interval a tectonic quiet interval 5 5 ma 4 5 ma that extended for about a million years during the middle of the collision and may represent the time of locking of the subduction system and a post 4 5 ma phase of uplift unroofing and further diapirism in response to isostatic rebound our conclusions offer an alternative model for the evolution of this part of the banda arc

asymmetries in the moisture origin of antarctic precipitation the seasonality of moisture sources for precipitation in antarctica is studied with a lagrangian moisture source diagnostic moisture origin for precipitation in antarctica has strongly asymmetric properties which are related to the antarctic topography seasonal sea ice coverage and the land ocean contrasts in the mid latitudes of the southern hemisphere the highest altitudes of the east antarctic ice shield where major ice cores have been drilled have mean source latitudes of 45 40 s year round this finding contrasts to results from previous lagrangian studies which detected a more southerly moisture origin due to too short trajectories now results from lagrangian moisture source diagnostics are consistent with findings from general circulation models with tagged tracers thus both approaches can serve as a common benchmark for the interpretation of moisture source indicators based on stable isotopes such as deuterium excess in antarctic ice cores

twentieth century increase in snowfall in coastal west antarctica the amundsen sea sector of the west antarctic ice sheet has been losing mass in recent decades however long records of snow accumulation are needed to place the recent changes in context here we present 300 year records of snow accumulation from two ice cores drilled in ellsworth land west antarctica the records show a dramatic increase in snow accumulation during the twentieth century linked to a deepening of the amundsen sea low asl tropical sea surface temperatures and large scale atmospheric circulation the observed increase in snow accumulation and interannual variability during the late twentieth century is unprecedented in the context of the past 300 years and evidence that the recent deepening of the asl is part of a longer trend

tomography the geoid and plate motions the dynamics of the earth s mantle and its relationship to mantle structure as revealed by seismic tomography the geoid and plate motions are discussed in a critical review of u s research from the period 1987 1990 sections are devoted to plates and mantle convection seismic anomalies flow and the geoid subducted slabs and the 670 km discontinuity the physical properties of the mantle plumes and computational and experimental modeling efforts also included is a comprehensive bibliography for the period 248 refs

the secular variation of earth s magnetic field models of the magnetic field at the core mantle boundary at selected epochs from 1715 0 to 1980 0 reveal novel features in the field at the core these suggest that the flow of core fluid is coupled to the mantle and that magnetic diffusion is significant

the depth dependency of planktonic benthic foraminiferal ratios constraints and applications abstract study of the ratio between planktonic and benthic foraminifera in a great number of areas shows that variation of this ratio with depth can be described using organic matter flux equations essentially the share of benthic foraminifera in the total association is inversely proportional to depth as is the amount of organic matter resulting from primary productivity reaching the sea bottom variation in the p b ratio from area to area appears to be strongly dependent on the amount of inbenthic living foraminifera if the ratios are corrected for this the regressions between the proportion of planktonic foraminifera p and depth appear to be near identical in the gulf of mexico the gulf of california the west coast of the usa and the adriatic sea this regression can be described by depth e 3 58718 0 03534 p a study of the behaviour of this function in nine cores from the adriatic upper quaternary reveals that the palaeodepth reconstructions are not influenced by fluctuations in productivity and temperature but that they are significantly influenced by redeposition of fine grained deposits

snowfall driven mass change on the east antarctic ice sheet 1 an improved understanding of processes dominating the sensitive balance between mass loss primarily due to glacial discharge and mass gain through precipitation is essential for determining the future behavior of the antarctic ice sheet and its contribution to sea level rise while satellite observations of antarctica indicate that west antarctica experiences dramatic mass loss along the antarctic peninsula and pine island glacier east antarctica has remained comparably stable in this study we describe the causes and magnitude of recent extreme precipitation events along the east antarctic coast that led to significant regional mass accumulations that partially compensate for some of the recent global ice mass losses that contribute to global sea level rise the gain of almost 350 gt from 2009 to 2011 is equivalent to a decrease in global mean sea level at a rate of 0 32 mm yr over this three year period

understanding the sam influence on the south pacific enso teleconnection the relationship between the el nino southern oscillation enso and the southern hemisphere annular mode sam is examined with the goal of understanding how various strong sam events modulate the enso teleconnection to the south pacific 45 70 s 150 70 w the focus is on multi month multi event variations during the last 50 years a significant p 0 10 relationship is observed most marked during the austral summer and in the 1970s and 1990s in most cases the significant relationship is brought about by la nina el nino events occurring with positive negative phases of the sam more often than expected by chance the south pacific teleconnection magnitude is found to be strongly dependent on the sam phase only when enso events occur with a weak sam or when a la nina el nino occurs with a positive negative sam phase are significant south pacific teleconnections found this modulation in the south pacific enso teleconnection is directly tied to the interaction of the anomalous enso and sam transient eddy momentum fluxes during la nina sam and el nino sam combinations the anomalous transient momentum fluxes in the pacific act to reinforce the circulation anomalies in the midlatitudes altering the circulation in such a way to maintain the enso teleconnections in la nina sam and el nino sam cases the anomalous transient eddies oppose each other in the midlatitudes overall acting to reduce the magnitude of the high latitude enso teleconnection

arc parallel extrusion of the timor sector of the banda arc continent collision structural studies of synorogenic basins in timor using field and remote sensing techniques provide new structural and geomorphic evidence for syn collisional extension in the converging plate boun

thermal core mantle interactions maps of the magnetic field at the core mantle boundary for 1715 1980 reveal static features in the field and an absence of westward drift from much of the core mantle boundary the static features suggest that flow in the core is coupled to the mantle we examine different coupling mechanisms and predict lateral inhomogeneity at the core mantle boundary comparison with models of the lower mantle and core mantle boundary derived seismically and from the geoid is encouraging though their resolution is currently inadequate for a full comparison to be made with the much better resolved magnetic field

bathymetric distribution of benthic foraminifera on the australian irian jaya continental margin eastern indonesia abstract we identified 164 taxa of benthic foraminifera in 35 selected box core top samples collected on the australian irian jaya continental margin in waterdepths between 60 and 2119 m along three systematically sampled transects across the banda arc the bathymetric distribution pattern of the benthic foraminiferal faunas is related to the oceanographic situation of this area where the watermasses of the indian ocean collide with the watermasses of the pacific ocean with the results of cluster analyses and empirical depth ranges of isobathyal taxa four faunal depth zones and four subzones can be distinguished 1 a the outer shelf biofacies 60 150 m corresponding to the photic oxycline zone of the indonesian surface waters and inhabited by a benthic foraminiferal association dominated by amphistegina lessonii operculina ammonoides heterolepa dutemplei and various miliolids 2 b the upper bathyal biofacies 150 400 m reflecting the aphotic deeper indonesian surface waters dominated by bolivina robusta heterolepa mediocris hanzawaia nipponica and lenticulina spp a major faunal break is situated at the lower boundary of this depth zone 3 c the middle bathyal biofacies 400 1500 m representing the indonesian intermediate waters with minimum oxygen contents dominated by bolivina robusta cassidulina carinata gavelinopsis lobatulus and sphaeroidina bulloides in this depth zone many taxa occur with only limited depth ranges on which four subzones c1 4 could be identified allowing for a local paleo bathymetric resolution of a few hundred meters 4 d the lower bathyal biofacies 1500 2120 m corresponds with the indonesian deep waters it is dominated by pullenia bulloides and other cosmopolitan deep water indicators such as epistominella exigua laticarinina pauperata oridorsalis umbonatus and planulina wuellerstorfi the sample fraction 250 m can be used to readily delineate the major faunal trends paleobathymetric resolution improves when the sample portion 125 m is used

some analytical methods for converting thermochronometric age to erosion rate 1 an analytical method is presented for converting thermochronometric ages to surface erosion or equivalently exhumation rate the method incorporates the two most important thermal processes during cooling by erosion the dependence of closure temperature on cooling rate and the advection of heat by rock motion toward the earth s surface two thermal models are considered 1 a steady state model valid for low erosion rates and 2 an eroding half space model which has no steady state but captures the transient increase of geothermal gradient with erosion in each case it is assumed that data consist of one or more thermochronometric ages present day surface geothermal gradient and topographic information including the elevation at which the age was obtained analytical solutions are provided to derive the erosion rate from these data either as an explicit expression for the steady case or as a root finding problem for the transient case a graphical method for plotting age against erosion rate and geothermal gradient is presented as a method for solving the root finding problem and for tracking analytical errors in observations of age and surface geothermal gradient the graphical method is also appropriate for comparing data from different elevations or from different thermochronometric systems examples are provided using synthetic data or published data from the literature

palaeobathymetric gradients across timor during 5 7 3 3ma latest miocene pliocene and implications for collision uplift abstract palaeobathymetry is interpreted for the oldest post collision deposits present in timor the distributions of planktonic and benthic foraminifera in chalk marl and mudstone successions that accumulated during 5 7 3 3 ma form the bases for age zonation and water depth interpretation data from 77 samples collected from 11 stratigraphic sections in east timor are combined with information previously published from several sections in west timor to provide control points for palaeobathymetric contouring the bathymetric reconstruction is based on interpreted water depths at the control points in combination with aspects of the spatial geology of timor speculative bathymetric contours are illustrated for time slices represented by three planktonic foraminiferal zones n18 5 5 5 7 ma n19r 4 3 5 5 ma and n20r 3 3 4 3 ma studied samples provide evidence for three bathymetric zones 500 1000 m 1000 1500 m and 1500 2500 m and suggestions are made for the positions of the 500 m 1000 m and 1500 m contours during each time slice the contours show only very gradual variation from 5 7 ma to 3 3 ma and suggest a deepening bathymetric gradient from the northern region where the structurally deepest part of the orogenic pile the aileu metamorphic complex is now exposed to the south east and west the contour maps provide a suggestion for visualizing the topography of the evolving orogenic pile that forms timor from about 5 7 ma through to 3 3 ma the relatively undeformed friable chalk and marl deposits of zone 18 5 7 5 5 ma overlie highly deformed and diagenetically more altered strata this indicates that the initial phase of collision between the australian continent and the banda arc took place prior to 5 7 5 5 ma rather than later during the pliocene or pleistocene as some authors have suggested because of lack of substantiated stratigraphic evidence from anywhere in timor for the 9 8 5 7 ma interval covering much of the late miocene the antecedent topography cannot be determined the bathymetric reconstructions for 5 7 3 3 ma suggest that a deep foreland basin precursor of the present timor sea had developed by 5 7 ma with uplifted areas to the north in an emerging island

influence of large scale atmospheric circulation on marine air intrusion toward the east antarctic coast marine air intrusions into antarctica play a key role in high precipitation events here we use shipboard observations of water vapor isotopologues between australia and syowa on the east antarctic coast to elucidate the mechanism by which large scale circulation influences marine air intrusions the temporal isotopic variations at syowa reflect the meridional movement of a marine air front they are also associated with atmospheric circulation anomalies that enhance the southward movement of cyclones over the southern ocean the relationship between large scale circulation and the movement of the front is explained by northerly winds which in association with cyclones move toward the antarctic coast and push marine air with isotopically enriched moisture into the inland covered by glacial air with depleted isotopic values future changes in large scale circulation may have a significant impact on the frequency and intensity of marine air intrusion into antarctica

on going orogeny in the outer arc of the timor tanimbar region eastern indonesia abstract the timor tanimbar islands of eastern indonesia form a non volcanic arc in front of a 7 km deep fore arc basin that separates it from a volcanic inner arc the timor tanimbar islands expose one of the youngest high p t metamorphic belts in the world providing us with an excellent opportunity to study the inception of orogenic processes undisturbed by later tectonic events structural and petrological studies of the high p t metamorphic belt show that both deformation and metamorphic grade increase towards the centre of the 1 km thick crystalline belt kinematic indicators exhibit top to the north sense of shear along the subhorizontal upper boundaries and top to the south sense in the bottom boundaries of the high p t metamorphic belt overall configuration suggests that the high p t metamorphic rocks extruded as a thin sheet into a space between overlying ophiolites and underlying continental shelf sediments petrological study further illustrates that the central crystalline unit underwent a barrovian type overprint of the original high p t metamorphic assemblages during wedge extrusion and the metamorphic grade ranged from pumpellyite actinolite to upper amphibolite facies quaternary uplift marked by elevation of recent reefs was estimated to be about 1260 m in timor in the west and decreases toward tanimbar in the east in contrast radiometric ages for the high p t metamorphic rocks suggest that the exhumation of the high p t metamorphic belt started in western timor in late miocene time and migrated toward the east thus the tectonic evolution of this region is diachronous and youngs to the east we conclude that the deep seated high p t metamorphic belt extrudes into shallow crustal levels as a first step followed by doming at a later stage the so called mountain building process is restricted to the second stage we attribute this quaternary rapid uplift to rebound of the subducting australian continental crust beneath timor after it achieved positive buoyancy due to break off of the oceanic slab fringing the continental crust in contrast tanimbar in the east has not yet been affected by later doming a wide spectrum of processes starting from extrusion of the high p t metamorphic rocks and ending with the later doming due to slab break off can be observed in the timor tanimbar region

plate boundary reorganization in the active banda arc continent collision insights from new gps measurements abstract new gps measurements reveal that large sections of the se asian plate are progressively accreting to the edge of the australian continent by distribution of strain away from the deformation front to forearc and backarc plate boundary segments the study was designed to investigate relative motions across suspected plate boundary segments in the transition from subduction to collision the oblique nature of the collision provides a way to quantify the spatial and temporal distribution of strain from the deformation front to the back arc the 12 sites we measured from bali to timor included some from an earlier study and 7 additional stations which extended the epoch of observation to ten years at many sites the resulting gps velocity field delineates at least three sunda arc forearc regions around 500 km in strike length that shows different amounts of coupling to the australian plate movement of these regions relative to se asia increases from 21 to 41 to 63 eastward toward the most advanced stages of collision the regions are bounded by the deformation front to the south the flores wetar backarc thrust system to the north and poorly defined structures on the sides the suture zone between the nw australian continental margin and the sunda banda arcs is still evolving with more than 20 mm yr of movement measured across the timor trough deformation front between timor and australia

the surface windfield over the antarctic ice sheets the intense radiative cooling of air over the ice slopes of antarctica generates a surface wind regime that is strongly controlled by topography and plays a key role in determining the behaviour of the atmosphere and ocean in high southern latitudes1 7 resultant surface winds are intimately linked to the orientation of the ice terrain fig 1 and display the highest degree of persistence found on earth the close coupling between wind and topography allows estimation of the former if the latter is known with some precision here we report on time averaged near surface airflow over the antarctic continent during winter diagnosed from a recent accurate synthesis of terrain slopes and from estimates of the lower atmospheric temperature structure the simulated drainage pat tern exhibits strong spatial variability with the airflow concentrated into several zones near the coastal margin these confluence regions are responsible for strong persistent katabatic winds over downstream coastal stretches and are indicative of zones of greatest katabatic potential