the retreat of a tidewater glacier observations and model calculations on hansbreen spitsbergen based on observations and model calculations the retreat over the last two decades of hansbreen a tidewater glacier in southern spitsbergen svalbard is investigated the observations of the calving front position between 1982 and 1998 show an abrupt retreat in 1990 which is suggested to be related to a depression in the glacier bed the observed seasonal variations of the front position are mainly due to variations of the calving rate the observations of hansbreen further indicate that during periods of slow front position changes melting at the water line may play an important role in triggering the process of calving the evolution of hansbreen between 1982 and 1998 is simulated with a numerical model for the dynamics of tidewater glaciers using a flotation criterion for calving in which for each time step the part of the glacier terminus which is below a critical height above buoyancy is removed we are able to reproduce the observed rapid retreat of hansbreen through the depression in the glacier bed from the observations and model calculations we conclude that the rapid retreat is mainly an effect of basal topography in the terminus region and not a direct response to a change in mass balance

glacial valley cross profile morphology tian shan mountains china abstract the morphology of glacial valley cross sections can be described in terms of power law y ax b or quadratic equations y a bx cx 2 fitted to empirical data the quadratic solution provides a more robust way of describing the morphology of glacial valley cross sections whereas the power law has more potential in understanding the cross sectional shapes and their evolution these two functions are used to study the cross sectional morphology of glacial valleys in the middle and western tian shan mountains and to discuss the comparison with fluvial channels the major conclusions are 1 power law equation parameters a and b are sensitive to the origin selection with larger sensitivity in vertical and a a ln a values conversely c values of the quadratic equation are more stable regardless of different origins selected 2 hirano and aniya earth surf processes landforms 13 1988 707 716 suggested two characteristic patterns in the relationship between the power law exponent b and the valley form ratio fr however glacial valleys in these areas do not fit the rocky mountain model for b fr values described by hirano and aniya for alpine glacial valleys this indicates that this rocky mountain model cannot be applied to all alpine glacial areas 3 the c values of the quadratic equation represent a curvi linear trend with its corresponding fr s at the same time power law parameters a and b fit a closed linear relationship both from these areas and others in the published literature 4 the cross sectional shapes of glacial valleys show clear differences with fluvial channels by comparing a b values of glacial valleys with the hydraulic geometry of fluvial channels this implies that the a b relationship and the variation range of b values commonly with 1 5 2 5 may be helpful to differentiate valleys formed by different processes

bathymetric control of tidewater glacier mass loss in northwest greenland abstract it has been suggested that fjord geometry could be an important contributor to the observed mass loss variability in greenland by modulating the flow of warm water to marine terminating glaciers new gravity derived bathymetry of greenlandic fjords confirms the link between the grounding line depth and rates of glacier mass loss a relationship previously predicted only in ice models we focus on two neighboring glaciers to minimize differences in external forcing and therefore isolate the role of the fjord bathymetry tracy glacier has a deeper grounding line and has been retreating since 1892 with a contemporary mass budget of 1 63 gt a 1 heilprin glacier has a shallower grounding line depth a stable ice terminus and a mass budget of only 0 53 gt a 1 because of its deeper grounding line tracy has more ice in contact with warm subsurface water leaving it more vulnerable to changes in ocean forcing and therefore mass loss

paleoenvironments of lacustrine coals the occurrence of algae in humic coals abstract according to previous studies there is a significant difference in the thickness and number of coal seams from the foredeep and the intermontane coal basins or basins situated on platforms and cratons recent petrographic and geochemical investigations on selected coal samples from foredeep and intermontane basins of europe carboniferous and tertiary and south america permian show that the coal seams in each of these coal basins have significant differences in their petrographic and geochemical compositions many intermontane coals are characterized by more liptinite than foredeep coals fluorescence studies show that up to 75 of the liptinite macerals of these humic coals can be attributed to alginite and or degradation products of algae this indicates that generally subaquatic conditions occurred more often in the peats that formed within intermontane basins

recent changes in the flow of the ross ice shelf west antarctica abstract comparison of surface velocities measured during the ross ice shelf geophysical and glaciological survey riggs 1973 to 1978 and velocities measured via feature tracking between two moderate resolution imaging spectroradiometer modis mosaics compiled from 2003 4 and 2008 9 images reveals widespread slowing and minor areas of acceleration in the ross ice shelf ris over the approximately 30 year interval the largest changes 13 ma 2 occur near the whillans and mercer ice streams grounding line in the southernmost part of the ice shelf speed has increased over the interval up to 5 ma 2 between the macayeal ice stream grounding line and the shelf front and along the eastern shelf front changes in ice thickness computed using icesat laser altimetry are used together with a well tested model of the ice shelf to investigate underlying causes of change in the flow of the ice shelf over time the observed transients represent a combination of recent forcings and ongoing response to ice stream discharge variations over the past millennium while evidence of older events may be present the modern signal is dominated by shorter time scale events including the stagnation of kamb ice stream about 160 years ago recent changes in basal drag on the whillans ice stream ice plain and perhaps iceberg calving details in embayment geometry for example the shallow sea floor below crary ice rise modulate the spatial pattern of ice shelf response to boundary condition perturbations

21st century evolution of greenland outlet glacier velocities earlier observations on several of greenland s outlet glaciers starting near the turn of the 21st century indicated rapid annual scale and large 100 increases in glacier velocity combining data from several satellites we produce a decade long 2000 to 2010 record documenting the ongoing velocity evolution of nearly all 200 of greenland s major outlet glaciers revealing complex spatial and temporal patterns changes on fast flow marine terminating glaciers contrast with steady velocities on ice shelf terminating glaciers and slow speeds on land terminating glaciers regionally glaciers in the northwest accelerated steadily with more variability in the southeast and relatively steady flow elsewhere intraregional variability shows a complex response to regional and local forcing observed acceleration indicates that sea level rise from greenland may fall well below proposed upper bounds

evaluation of cryo hydrologic warming as an explanation for increased ice velocities in the wet snow zone sermeq avannarleq west greenland 1 wintertime satellite derived ice surface velocities from 2001 through 2007 suggest an increase in ice velocity in the wet snow zone of southwest greenland we present a thermomechanical model to evaluate the influence of surface meltwater runoff on englacial temperatures via cryo hydrologic warming chw as a possible mechanism to explain this velocity increase at sermeq avannarleq the model incorporates chw through a previously published dual column parameterization we compare model simulations with i chw active over the entire ice thickness base case chw ii chw active only in the surface 80 m of the ice sheet surface chw and iii no chw to represent a traditional thermomechanical model the horizontal extent of chw is prescribed based on equilibrium line altitude position and thus incorporates the upstream expansion of the ablation zone over the past decade the base case chw simulations reproduce the observed increase in inland ice velocity between 2001 and 2007 reasonably well the no chw and surface chw simulations significantly underestimate observed ice surface velocities in both epochs the higher ice velocities in the base case chw simulations are attributable to both decreased basal ice viscosities associated with increased basal ice temperatures and an increase in the extent of basal sliding permitted by temperate bed conditions only the temperate bed extent predicted by the base case chw simulation is consistent with independent observations of basal sliding based on our sensitivity analysis of chw we evaluate alternative explanations for an increase in inland ice velocity and suggest chw is the most plausible mechanism

progressive unpinning of thwaites glacier from newly identified offshore ridge constraints from aerogravity 1 a new bathymetric model from the thwaites glacier region based on icebridge airborne gravity data defines morphologic features that exert key controls on the evolution of the ice flow a prominent ridge with two distinct peaks has been identified 40 km in front of the present day grounding line undulating between 300 700 m below sea level with an average relief of 700 m presently the thwaites ice shelf is pinned on the eastern peak more extensive pinning in the past would have restricted flow of floating ice across the full width of the thwaites glacier system at present thinning rates ice would have lost contact with the western part of the ridge between 55 150 years ago allowing unconfined flow of floating ice and contributing to the present day mass imbalance of thwaites glacier the bathymetric model also reveals a 1200 m deep trough beneath a bight in the grounding line where the glacier is moving the fastest this newly defined trough marks the lowest topographic pathway to the byrd subglacial basin and the most likely path for future grounding line retreat

spatial and temporal variations in greenland glacial earthquake activity 1993 2010 1 glacial earthquakes are anomalous earthquakes associated with large ice loss events occurring at marine terminating glaciers primarily in greenland they are detectable teleseismically and a proper understanding of the source mechanism may provide a remote sensing tool to complement glaciological observations of these large outlet glaciers we model teleseismic surface wave waveforms to obtain locations and centroid single force source parameters for 121 glacial earthquakes occurring in greenland during the period 2006 2010 we combine these results with those obtained by previous workers to analyze spatial and temporal trends in glacial earthquake occurrence over the 18 year period from 1993 2010 we also examine earthquake occurrence at six individual glaciers comparing the earthquake record to independently obtained observations of glacier change our findings confirm the inference that glacial earthquake seismogenesis occurs through the capsize of large newly calved icebergs we find a close correspondence between episodes of glacier retreat thinning and acceleration and the timing of glacial earthquakes and document the northward progression of glacial earthquakes on greenland s west coast over the 18 year observing period our results also show that glacial earthquakes occur when the termini of the source glaciers are very close to the glacier grounding line i e when the glaciers are grounded or nearly grounded

角閃石中のアルミニウム圧力計を使って決定された ワシントン州 stuart山バソリスの広域的傾動 バハ ブリティシュコロンビアの北方への転移に関する意味

the stratigraphic distribution of inertinite abstract the paper presents the results of an investigation into the stratigraphic distribution of inertinite in humic coals ranging from the silurian to the neogene periods this range equals the time span during which both land plants and atmospheric oxygen evolved the survey is based on a literature study of inertinite in coals covering a variety of depositional environments and climates in all continents the inertinite percentages listed in this paper have been arranged in stratigraphic order they are the mean values based on mineral free whole coal compilations maceral compositions listed in the literature for individual subsections have been averaged to represent complete coal seams beds although this might not have been always possible due to some ambiguity in the published record moreover not all of the published and unpublished information could be used because of poor sample description obscure geographic origin or insufficient stratigraphic information the results show that there have been times in the geological past e g during the late permian in which coals were particularly rich in inertinite compared with other times e g during much of the late tertiary in which many coals contained very little inertinite occasionally such primary global trends were modulated by a diffuse distribution of inertinite percentages that correspond to differences in climate depositional settings e g active orogenic margins versus tectonically inactive shelf margins and other local or regional variations although various mechanisms for the generation of inertinite have been proposed in the past the overall pattern in its stratigraphic distribution supports the notion of incomplete combustion as the main source of inertinite in coal this points to secular variations in the atmospheric oxygen content as an explanation for the global changes in the inertinite distribution while differential subsidence and climatically influenced reaction rates governed regional and local variations in inertinite percentages

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

the impact of glacier geometry on meltwater plume structure and submarine melt in greenland fjords meltwater from the greenland ice sheet often drains subglacially into fjords driving upwelling plumes at glacier termini ocean models and observations of submarine termini suggest that plumes enhance melt and undercutting leading to calving and potential glacier destabilization here we systematically evaluate how simulated plume structure and submarine melt during summer months depends on realistic ranges of subglacial discharge glacier depth and ocean stratification from 12 greenland fjords our results show that grounding line depth is a strong control on plume induced submarine melt deep glaciers produce warm salty subsurface plumes that undercut termini and shallow glaciers produce cold fresh surface trapped plumes that can overcut termini due to sustained upwelling velocities plumes in cold shallow fjords can induce equivalent depth averaged melt rates compared to warm deep fjords these results detail a direct ocean ice feedback that can affect the greenland ice sheet

changes in the velocity structure of the greenland ice sheet using satellite radar interferometry observations of greenland we detected widespread glacier acceleration below 66 north between 1996 and 2000 which rapidly expanded to 70 north in 2005 accelerated ice discharge in the west and particularly in the east doubled the ice sheet mass deficit in the last decade from 90 to 220 cubic kilometers per year as more glaciers accelerate farther north the contribution of greenland to sea level rise will continue to increase

trace elements in the lower pliocene fossiliferous kangal lignites sivas turkey abstract the kangal lignite basin which is one of the most productive lignite basins in eastern anatolia turkey includes two lignite seams containing abundant gastropoda shells in the lower pliocene kalburcayiri formation the seams are currently exploited in an open cast mine in the kalburcayiri field and supply feed coal to a power plant with 300 mw capacity the average thickness of each of the two seams in this mine is about 10 m and they are separated by about 20 m of tuffaceous sedimentary rocks a 15 20 cm thick tuff bed occurs within the upper seam the purpose of the study was to understand mineralogy and trace element concentrations of the two lignite seams in the kalburcayiri formation which were affected by volcanic ashes fifty nine core samples of the lignites from seven boreholes across the basin and eight channel samples from the working lignite seams were collected and analysed by proximate analysis x ray powder diffraction xrd inductively coupled plasma mass spectrometry icp ms and scanning electron microscopy sem with energy dispersive x ray microanalysis techniques the samples show that the worked lignite seams on an as received basis contain high moisture contents 43 4 57 8 all the samples on an air dried basis have high ash yields from 19 5 to 81 7 and a broad range of total sulfur contents from 1 16 to 7 04 and calorific values 684 to 4621 kcal kg except for two samples with no temperature rise due to high ash yield the mineral matter of the studied samples is made up of calcite quartz feldspar pyrite opal ct clay minerals gypsum and traces of aragonite the trace element analyses on a whole coal dry basis indicate that most of the borehole samples showed enrichment in specific elements including zn 15 1394 g g mo 13 368 g g and u 5 5 131 g g when compared to the range of these elements for most coals in the world the contents of zn mo and u for the samples from the worked lignite seams are respectively 38 187 54 161 and 28 55 g g the sem studies show that zn is hosted mainly in micron sized zn bearing mineral sphalerite but no mo and u bearing minerals have been detected during these studies except for monazites containing th and u traces the mo and u concentrations are negatively correlated with the ash yields and these elements are contained mainly within organic matter

contribution of alaskan glaciers to sea level rise derived from satellite imagery over the last 50 years retreating glaciers and ice caps gic contributed 0 5 mm yr to sea level rises slr and one third is believed to originate from ice masses bordering the gulf of alaska however these estimates of ice wastage in alaska are based on methods that measure a limited number of glaciers and extrapolate the results to estimate ice loss for the many thousands of others how these methods capture the complex pattern of decadal elevation changes at the scale of individual glacier and mountain range is unclear here combining a comprehensive glacier inventory with elevation changes derived from sequential digital elevation models dems we found that between 1962 and 2006 alaskan glaciers lost 41 9 8 6 km 3 yr water equivalent w e and contributed 0 12 0 02 mm yr to slr our ice loss is 34 lower than previous estimates reasons for our lower values include the higher spatial resolution of our glacier inventory and the reduction of ice thinning under debris and at the glacier margins which were not resolved in earlier work estimates of mass loss from gic in other mountain regions could be subject to similar revisions

large scale changes in greenland outlet glacier dynamics triggered at the terminus the recent dramatic retreat of many outlet glaciers of the greenland ice sheet has raised concerns over greenland s contribution to future sea level rise simulations with a numerical ice flow model indicate that the recent rates of mass loss in greenland s outlet glaciers are transient and should not be extrapolated into the future

ice sheet grounding line dynamics steady states stability and hysteresis 1 the ice sheet ice shelf transition zone plays an important role in controlling marine ice sheet dynamics as it determines the rate at which ice flows out of the grounded part of the ice sheet together with accumulation this outflow is the main control on the mass balance of the grounded sheet in this paper we verify the results of a boundary layer theory for ice flux in the transition zone against numerical solutions that are able to resolve the transition zone very close agreement is obtained and grid refinement in the transition zone is identified as a critical component in obtaining reliable numerical results the boundary layer theory confirms that ice flux through the grounding line in a two dimensional sheet shelf system increases sharply with ice thickness at the grounding line this result is then applied to the large scale dynamics of a marine ice sheet our principal results are that 1 marine ice sheets do not exhibit neutral equilibrium but have well defined discrete equilibrium profiles 2 steady grounding lines cannot be stable on reverse bed slopes and 3 marine ice sheets with overdeepened beds can undergo hysteresis under variations in sea level accumulation rate basal slipperiness and ice viscosity this hysteretic behavior can in principle explain the retreat of the west antarctic ice sheet following the last glacial maximum and may play a role in the dynamics of heinrich events

subannual and seasonal variability of atlantic origin waters in two adjacent west greenland fjords greenland fjords provide a pathway for the inflow of warm shelf waters to glacier termini and outflow of glacially modified waters to the coastal ocean characterizing the dominant modes of variability in fjord circulation and how they vary over subannual and seasonal time scales is critical for predicting ocean heat transport to the ice here we present a 2 year hydrographic record from a suite of moorings in davis strait and two neighboring west greenland fjords that exhibit contrasting fjord and glacier geometry kangerdlugssuaq sermerssua and rink isbrae hydrographic variability above the sill exhibits clear seasonality with a progressive cooling of near surface waters and shoaling of deep isotherms above the sill during winter to spring renewal of below sill waters coincides with the arrival of dense waters at the fjord mouth warm salty atlantic origin water cascades into fjord basins from winter to midsummer we then use seaglider observations at davis strait along with reanalysis of sea ice and wind stress in baffin bay to explore the role of the west greenland current and local air sea forcing in driving fjord renewal these results demonstrate the importance of both remote and local processes in driving renewal of near terminus waters highlighting the need for sustained observations and improved ocean models that resolve the complete slope trough fjord ice system

a reconciled estimate of glacier contributions to sea level rise 2003 to 2009 glaciers distinct from the greenland and antarctic ice sheets are losing large amounts of water to the world s oceans however estimates of their contribution to sea level rise disagree we provide a consensus estimate by standardizing existing and creating new mass budget estimates from satellite gravimetry and altimetry and from local glaciological records in many regions local measurements are more negative than satellite based estimates all regions lost mass during 2003 2009 with the largest losses from arctic canada alaska coastal greenland the southern andes and high mountain asia but there was little loss from glaciers in antarctica over this period the global mass budget was 259 28 gigatons per year equivalent to the combined loss from both ice sheets and accounting for 29 13 of the observed sea level rise

occurrence and distribution of sulfur in peat forming environments of southern florida abstract cores and surface samples of peats from the everglades mangrove region of southern florida were analyzed for total sulfur and pyritic sulfur these values were compared with the petrographic botanical components of the peats as determined from point counts of oriented microtome sections pyrite occurs as individual euhedral crystals loosely packed framboids and lenses or crusts of minute crystals framboids and minute crystals are often associated with organic matter and sometimes with bacteria and fungi pyrite tends to selectively occur in void spaces in or between peat tissues in samples containing very small amounts of pyrite framboidal pyrite is the prevalent form marine to brackish peats contain the highest pyrite and total sulfur contents with brackish peats generally containing more pyrite than marine peats pyrite tends to be lower in all peats within 30 cm of the surface whether marine or brackish burial of freshwater peats beneath marine or brackish peats tends to increase the total sulfur and pyritic sulfur in the underlying peats burial beneath brackish water clay rich deposits such as splays tends to increase total sulfur and pyritic sulfur in the underlying deposits more than burial beneath less clay rich deposits

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

threefold increase in marine terminating outlet glacier retreat rates across the atlantic arctic 1992 2010 accelerated discharge through marine terminating outlet glaciers has been a key component of the rapid mass loss from arctic glaciers since the 1990s however glacier retreat and its climatic controls have not been assessed at the pan arctic scale consequently the spatial and temporal variability in the magnitude of retreat and the possible drivers are uncertain here we use remotely sensed data acquired over 273 outlet glaciers located across the entire atlantic arctic i e areas potentially influenced by north atlantic climate and or ocean conditions specifically greenland novaya zemlya franz josef land and svalbard to demonstrate high magnitude accelerating and near ubiquitous retreat between 1992 and 2010 overall mean retreat rates increased by a factor of 3 5 between 1992 and 2000 30 5 m a 1 and 2000 10 105 8 m a 1 with 97 of the study glaciers retreating during the latter period the retreat was greatest in northern western and south eastern greenland and also increased substantially on the barents sea coast of novaya zemlya glacier retreat showed no significant or consistent relationship with summer air temperatures at decadal timescales the rate of frontal position change showed a significant but weak correlation with changes in sea ice concentrations we highlight large variations in retreat rates within regions and suggest that fjord topography plays an important role we conclude that marine terminating arctic outlet glaciers show a common response of rapid and accelerating retreat at decadal timescales

airgrav results a comparison of airborne gravity data with gsc test site data sander geophysics sgl has developed an airborne gravimeter system that uses three orthogonal accelerometers mounted on a three axis gyroscopically stabilized platform the system called airgrav airborne inertially referenced gravimeter was designed specifically for airborne use this has resulted in an instrument with significant advantages over the modified sea gravimeters commonly used for airborne surveying the main benefit of the new instrument is that it is more stable in attitude and less subject to noise from horizontal accelerations

rapid bottom melting widespread near antarctic ice sheet grounding lines as continental ice from antarctica reaches the grounding line and begins to float its underside melts into the ocean results obtained with satellite radar interferometry reveal that bottom melt rates experienced by large outlet glaciers near their grounding lines are far higher than generally assumed the melting rate is positively correlated with thermal forcing increasing by 1 meter per year for each 0 1 c rise in ocean temperature where deep water has direct access to grounding lines glaciers and ice shelves are vulnerable to ongoing increases in ocean temperature

ice front change of marine terminating outlet glaciers in northwest and southeast greenland during the 21st century the increasingly negative mass balance of the greenland ice sheet gris over the last 25 years has been associated with enhanced surface melt and increased ice loss from marine terminating outlet glaciers accelerated retreat during 2000 2010 was concentrated in the southeast and northwest sectors of the ice sheet however there was considerable spatial and temporal variability in the timing and magnitude of retreat both within and between these regions this behaviour has yet to be quantified and compared for all glaciers in both regions furthermore it is unclear whether retreat has continued after 2010 in the northwest and whether the documented slowdown in the southeast post 2005 has been sustained here we compare spatial and temporal patterns of frontal change in the northwest and southeast gris for the period 2000 2015 our results show near ubiquitous retreat of outlet glaciers across both regions for the study period however the timing and magnitude of inter annual frontal position change is largely asynchronous we also find that since 2010 there is continued terminus retreat in the northwest which contrasts with considerable inter annual variability in the southeast analysis of the role of glacier specific factors demonstrates that fjord and bed geometry are important controls on the timing and magnitude of glacier retreat

baffin island and west greenland current systems in northern baffin bay abstract temperature salinity and direct velocity observations from northern baffin bay are presented from a summer 2003 survey the data reveal interactions between fresh and cold arctic waters advected southward along baffin island and salty and warm atlantic waters advected northward along western greenland geostrophic currents estimated from hydrography are compared to measured ocean currents above 600 m depth the baffin island current is well constrained by the geostrophic thermal wind relation but the west greenland current is not furthermore both currents are better described as current systems that contain multiple velocity cores and eddies we describe a surface intensified baffin island current seaward of the continental slope off canada and a bottom intensified west greenland current over the continental slope off greenland acoustic doppler current profiler observations suggest that the west greenland current system advected about 3 8 0 27 sv sv 10 6 m 3 s 1 towards the north west at this time the most prominent features were a surface intensified coastal current advecting 0 5 sv and a bottom intensified slope current advecting about 2 5 sv in the same direction most of this north westward circulation turned southward in the baffin island current system the baffin island system was transporting 5 1 0 24 sv to the south east at the time that includes additional contributions from nares strait to the north 1 0 0 2 sv and lancaster sound to the east 1 0 0 2 sv net freshwater fluxes were 72 and 187 msv for the west greenland and baffin island currents respectively empirical uncertainty arises from unknown temporal variations at weekly time scales and pertubations introduced by unresolved eddies eddies with 10 km horizontal and 400 m vertical scales were common and recirculated up to 1 sv our 2003 observations represent conditions when the north atlantic oscillation index nao was close to zero analysis of historical hydrographic data averaged along isobaths during nao positive years reveals a baroclinic circulation in baffin bay more intense than 2003 with stronger southward flow of fresher arctic waters along baffin island and stronger northward inflow of saltier atlantic waters along greenland during negative nao years this cyclonic circulation weakens as evidenced by a 1979 synoptic survey of the hydrography along baffin island

iceberg calving during transition from grounded to floating ice columbia glacier alaska 1 the terminus of columbia glacier alaska unexpectedly became ungrounded in 2007 during its prolonged retreat visual observations showed that calving changed from a steady release of low volume bergs to episodic flow perpendicular rifting propagation and release of very large icebergs a style reminiscent of calving from ice shelves here we compare passive seismic and photographic observations through this transition to examine changes in calving mechanical changes accompany the visible changes in calving style post flotation generation of seismic energy during calving is substantially reduced we propose this is partly due to changes in source processes

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

the relationship between macerals and sulphur content of some south african permian coals abstract there is a positive correlation between sulphur concentration and the vitrinite maceral group content in permian vryheid formation coals in south africa the reverse is true for the inertinite maceral family this relationship is evident at intraseam interseam and intercoalfied levels vitrinite precursors formed where the water table in peat forming environments was high and eh low these conditions favoured bacterial sulphate reduction and resulting h 2 s reacted with fe 2 and organic peat compounds to form pyrite and organic sulphur components inertinite precursors formed when the water table was low and eh high aerobic respiration prevailed and little h 2 s was produced organic sulphur derived from peat forming plant tissue is dominant in intertinite rich low sulphur coal pyritic sulphur exceeds organic sulphur in high sulphur coals dur to preferential reaction of h 2 s with fe 2

oceanic controls on the mass balance of wilkins ice shelf antarctica 0 8 m a 1 driven by a mean basal melt rate of wb 1 3 0 4 m a 1 interannual variability was large associated with changes in both surface mass accumulation and wb basal melt rate declined significantly around 2000 from 1 8 0 4 m a 1 for 1992 2000 to 0 75 0 55 m a 1 for 2001 2008 the latter value corresponding to approximately steady state ice shelf mass observations of ocean temperature t obtained during 2007 2009 by instrumented seals reveal a cold deep halo of winter water ww t 1 6 c surrounding wis the base of the ww in the halo is 170 m approximately the mean ice draft for wis we hypothesize that the transition in wb in 2000 was caused by a small perturbation 10 20 m in the relative depths of the ice base and the bottom of the ww layer in the halo we conclude that basal melting of thin ice shelves like wis is very sensitive to upper ocean and coastal processes that act on shorter time and space scales than those affecting basal melting of thicker west antarctic ice shelves such as george vi and pine island glacier

response of glacier flow and structure to proglacial lake development and climate at fjallsjokull south east iceland over recent decades the number of outlet glaciers terminating in lakes in iceland has increased in line with climate warming the mass balance changes of these lake terminating outlet glaciers are sensitive to rising air temperatures due to altered glacier dynamics and increased surface melt this study aims to better understand the relationship between proglacial lake development climate glacier dynamics and glacier structure at fjallsjokull a large lake terminating outlet glacier in south east iceland we used satellite imagery to map glacier terminus position and lake extent between 1973 and 2016 and a combination of aerial and satellite imagery to map the structural architecture of the glacier s terminus in 1982 1994 and 2011 the temporal evolution of ice surface velocities between 1990 and 2018 was calculated using feature tracking statistically significant increases in the rate of terminus retreat and lake expansion were identified in 2001 2009 and 2011 our surface velocity and structural datasets revealed the development of localised flow corridors over time which conveyed relatively faster flow towards the glacier s terminus we attribute the overall changes in dynamics and structural architecture at fjallsjokull to rising air temperatures but argue that the spatial complexities are driven by glacier specific factors such as basal topography

ice front and flow speed variations of marine terminating outlet glaciers along the coast of prudhoe land northwestern greenland satellite images were analyzed to measure the frontal positions and ice speeds of 19 marine terminating outlet glaciers along the coast of prudhoe land northwestern greenland from 1987 to 2014 all the studied glaciers retreated over the study period at a rate of between 12 and 200 m a 1 with a median mean retreat rate of 30 40 m a 1 the glacier retreat began in the year 2000 which coincided with an increase in summer mean air temperature from 1 4 to 5 5 c between 1996 and 2000 in this region ice speed near the front of the studied glaciers ranged between 20 and 1740 m a 1 in 2014 and many of them accelerated in the early 2000s in general the faster retreat was observed at the glaciers that experienced greater acceleration as represented by tracy glacier which experienced a retreat of 200 m a 1 and a velocity increase of 930 m a 1 during the study period a possible interpretation of this observation is that flow acceleration induced dynamic thinning near the termini resulting in enhanced calving and rapid retreat of the studied glaciers we hypothesize that atmospheric warming conditions in the late 1990s triggered glacier retreat in northwestern greenland since 2000

seasonal ice speed variations in 10 marine terminating outlet glaciers along the coast of prudhoe land northwestern greenland we present a 3 year record of seasonal variations in ice speed and frontal ablation of 10 marine terminating outlet glaciers along the coast of prudhoe land in northwestern greenland the glaciers showed seasonal speedup initiated between late may and early june and terminated between late june and early july ice speed subsequently decreased from july to september the timing of the speedup coincided with the onset of the air temperature rise to above freezing suggesting an influence of meltwater availability on the glacier dynamics no clear relationship was found between the speedup and the terminus position or the sea ice ice melange conditions these results suggest that the meltwater input to the glacier bed triggered the summer speedup the excess of summer speed june august over the mean for the rest of the year accounted for 0 5 13 of the annual ice motion several glaciers showed seasonal frontal variations i e retreat in summer and advance in winter this was not due to ice speed variations but was driven by seasonal variations in frontal ablation the results demonstrate the dominant effect of glacier surface melting on the seasonal speedup and the importance of seasonal speed patterns on longer term ice motion of marine terminating outlet glaciers in greenland

improved ice loss estimate of the northwestern greenland ice sheet 1 we estimate ice volume change rates in the northwest greenland drainage basin during 2003 2009 using ice cloud and land elevation satellite icesat laser altimeter data elevation changes are often reported to be largest near the frontal portion of outlet glaciers to improve the volume change estimate we supplement the icesat data with altimeter surveys from nasa s airborne topographic mapper from 2002 to 2010 and nasa s land vegetation and ice sensor from 2010 the airborne data are mainly concentrated along the ice margin and thus have a significant impact on the estimate of the volume change our results show that adding airborne topographic mapper and land vegetation and ice sensor data to the icesat data increases the catchment wide estimate of ice volume loss by 11 mainly due to an improved volume loss estimate along the ice sheet margin furthermore our results show a significant acceleration in mass loss at elevations above 1200m both the improved mass loss estimate along the ice sheet margin and the acceleration at higher elevations have implications for predictions of the elastic adjustment of the lithosphere caused by present day ice mass changes our study shows that the use of icesat data alone to predict elastic uplift rates biases the predicted rates by several millimeters per year at gps locations along the northwestern coast

comparison of airgrav and gt 1a airborne gravimeters for research applications airbornegravimetryhasplayedavitalroleincontributing to our knowledge of the subglacial environment in polar regions previous programs have produced extensive gravity data sets inantarctica but the resolution and accuracy of the datahavebeenlimited wehaveevaluatedtherelativeperformance and suitability of two different airborne gravimeters for research applications from flight tests over the canadian rocky mountains near calgary survey design mission profiles and demands on the performance of an airborne gravimeter are different for the remote polar environment thanformostcommercialexplorationsurveys bothsystems theairgrav and gt 1a can produce higher resolution data with improved flight efficiency than can the bgm 3 and lacoste romberg gravimeters used inantarctica theairgrav and gt 1asystems are capable of draped flying of airborne gravity allowing new applications for polar use both systems could provide the academic community with a significant increase in accuracy and horizontal resolution to enablemajoradvancesinunderstandingthesubglacialenvironment compared to the gt 1a system the airgrav system hasalowernoiselevelandhigheraccuracy anditislesssensitive to changing flight conditions in particular vertical accelerationsduringturbulentflights

spreading of warm ocean waters around greenland as a possible cause for glacier acceleration we examine the pattern of spreading of warm subtropical origin waters around greenland for the years 1992 2009 using a high resolution 4km horizontal grid coupled ocean and sea ice simulation the simulation provided by the estimating the circulation and climate of the ocean phase ii ecco2 project qualitatively reproduces the observed warming of subsurface waters in the subpolar gyre associated with changes of the north atlantic atmospheric state that occurred in the mid 1990s the modeled subsurface ocean temperature warmed by 1 5 c in southeast and southwest greenland during 1994 2005 and subsequently cooled by 0 5 c modeled subsurface ocean temperature increased by 2 2 5 c in central and then northwest greenland during 1997 2005 and stabilized thereafter while it increased after 2005 by xu and others 2012 we show that the oceanic changes have very likely increased the subaqueous melt rates of the glacier fronts and in turn impacted the rates of glacier flow

distribution of forms of sulfur in peats from saline environments in the florida everglades abstract although there is published information on the mechanism of sedimentary pyrite formation resulting from bacterial reduction of sulfate little is known about the distribution of forms of sulfur including organic in peats in order to increase understanding of the geochemistry of sulfur in coals we have determined distributions of forms of sulfur in five cores of saline peat and one of brackish peat all from areas near the shark river and whitewater bay in the coastal swamps of south florida all concentrations vary widely with depth total sulfur concentrations range up to 6 of dry solids minor amounts of sulfur are present as h2s s0 so42 and acid soluble sulfide but the principal forms are usually pyritic and organic the ratio organic pyritic is highly variable but at a majority of levels in a profile is considerably greater than unity it is inferred that topochemical factors are important in determining the distribution of sulfur forms in any element of volume

recent elevation changes of svalbard glaciers derived from icesat laser altimetry abstract we have tested three methods for estimating 2003 2008 elevation changes of svalbard glaciers from multi temporal icesat laser altimetry a linear interpolation of crossover points between ascending and descending tracks b projection of near repeat tracks onto common locations using digital elevation models dems and c least squares fitting of rigid planes to segments of repeat track data assuming a constant elevation change rate the two repeat track methods yield similar results and compare well to the more accurate but sparsely sampled crossover points most glacier regions in svalbard have experienced low elevation thinning combined with high elevation balance or thickening during 2003 2008 the geodetic mass balance excluding calving front retreat or advance of svalbard s 34 600 km2 glaciers is estimated to be 4 3 1 4 gt y 1 corresponding to an area averaged water equivalent w e balance of 0 12 0 04 m w e y 1 the largest ice losses have occurred in the west and south while northeastern spitsbergen and the austfonna ice cap have gained mass winter and summer elevation changes derived from the same methods indicate that the spatial gradient in mass balance is mainly due to a larger summer season thinning in the west and the south than in the northeast our findings are consistent with in situ mass balance measurements from the same period confirming that repeat track satellite altimetry can be a valuable tool for monitoring short term elevation changes of arctic glaciers

numerical experiments on subaqueous melting of greenland tidewater glaciers in response to ocean warming and enhanced subglacial discharge the largest dischargers of ice in greenland are glaciers that terminate in the ocean and melt in contact with sea water studies of ice sheet ocean interactions have mostly focused on melting beneath near horizontal floating ice shelves for tidewater glaciers melting instead takes place along the vertical face of the calving front here we modify the massachusetts institute of technology general circulation model mitgcm to include ice melting from a calving face with the freshwater outflow at the glacier grounding line we use the model to predict melt rates and their sensitivity to ocean thermal forcing and to subglacial discharge we find that melt rates increase with approximately the one third power of the subglacial water flux and increase linearly with ocean thermal forcing our simulations indicate that consistent with limited field data melting ceases when subglacial discharge is shut off and reaches several meters per day when subglacial discharge is high in the summer these results are a first step toward a more realistic representation of subglacial discharge and of ocean thermal forcing on the subaqueous melting of tidewater glaciers in a numerical ocean model our results illustrate that the ice front melting process is both complex and strongly time dependent

resolving bathymetry from airborne gravity along greenland fjords recent glacier mass loss in greenland has been attributed to encroaching warming waters but knowledge of fjord bathymetry is required to investigate this mechanism the bathymetry in many greenland fjords is unmapped and difficult to measure from 2010 to 2012 national aeronautics and space administration s operation icebridge collected a unique set of airborne gravity magnetic radar and lidar data along the major outlet glaciers and fjords in greenland we applied a consistent technique using the icebridge gravity data to create 90 bathymetric profiles along 54 greenland fjords we also used this technique to recover subice topography where warm or crevassed ice prevents the radar system from imaging the bed here we discuss our methodology basic assumptions and error analysis we present the new bathymetry data and discuss observations in six major regions of greenland covered by icebridge the gravity models provide a total of 1950 line kilometers of bathymetry 875 line kilometers of subice topography and 12 new grounding line depths

fast tidewater glaciers some iceberg calving outlet glaciers flow continuously at speeds normally associated with surging glaciers arid exhibit dramatic instability scenarios related to those suggested for marine ice sheets no temperate tidewater glaciers are known to have floating termini but many polar and subpolar tidewater glaciers do the fast flow of temperate calving glaciers is almost entirely due to basal sliding and appears to be a function of the effective pressure on the bed which may approach zero and the longitudinal back stress on the terminus the terminus boundary condition the calving relation is imperfectly known yet is vital to the dynamics of these glaciers calving relations for grounded tidewater glaciers have been suggested on empirical grounds but have not been rigorously tested the calving relations for floating termini are virtually unknown this together with the imperfect understanding of basal sliding inhibits confidence in our understanding of the stability of these glaciers columbia glacier alaska is an instructive example because observations have been made on the major changes in its geometry calving rate and dynamics that have occurred in less than 10 years the calving flux has increased more rapidly than the glacier flux causing thinning and retreat as a result the ice velocity has increased markedly the short term velocity changes relate to changes in back pressure ice recession tidal changes and the flux of water injected to the bed these results have relevance to the mechanisms of basal sliding glacier surges and the stability of marine ice streams

bathymetry of southeast greenland from oceans melting greenland omg data southeast greenland has been a major participant in the ice sheet mass loss over the last several decades interpreting the evolution of glacier fronts requires information about their depth below

fluorescence spectral analysis of resinite macerals from coals of the hanna formation wyoming u s a abstract flourescence spectral analysis indicates that resinite macerals from tertiary hanna formation coals hanna coal field southcentral wyoming u s a can be separated into five distinct groups the first resinite group fluoresces a a medium green in blue light its average spectral maximum occurs at or below 440 mm with a red green quotient of 0 22 the second resinite group fluoresces yellow green with an average spectral maximum of 500 nm and a red green quotient of 0 53 the third resinite group displays a yellow fluorescence having an average spectral maximum of 580 nm and a red green quotient of 0 86 the fourth resinite group fluorescence orange brown having an average spectral maximum of 610 nm and a red green quotient of 1 20 these four groups mostly occur as primary globular resinites exhibiting scratches and fractures indicating that they are brittle solid substances primary cell filling and secondary fracture filling resinites also occur in these four groups the fifth group only occurs as a secondary void filling material and lacks evidence of br of brittle properties it fluoresces a reddish brown has a spectral maximum at 690 nm and a red green quotient of 1 54 the fifth group has properties resembling exsudatinite the five resinite groups can be separated on the basis of their nine spectral properties alone without qualitative petrographic interpretation the relative quantities of the five resinite groups vary among hanna formation coals the origins of these five resinite groups are probably related to their botanical properties and pre and post depossitional conditions overall hanna formation resinites have petrographic characteristics similar to other north american resinites however only four resinite groups have been distinguished in in certain coals from utah and new mexico u s a and western canada

glacier dynamics near the calving front of bowdoin glacier northwestern greenland to better understand recent rapid recession of marine terminating glaciers in greenland we performed satellite and field observations near the calving front of bowdoin glacier a 3 km wide outlet glacier in northwestern greenland satellite data revealed a clear transition to a rapidly retreating phase in 2008 from a relatively stable glacier condition that lasted for 20 years ice radar measurements showed that the glacier front is grounded but very close to the floating condition these results in combination with the results of ocean depth soundings suggest bed geometry in front of the glacier is the primary control on the rate and pattern of recent rapid retreat presumably glacier thinning due to atmospheric and or ocean warming triggered the initial retreat in situ measurements showed complex short term ice speed variations which were correlated with air temperature precipitation and ocean tides ice speed quickly responded to temperature rise and a heavy rain event indicating rapid drainage of surface water to the bed semi diurnal speed peaks coincided with low tides suggesting the major role of the hydrostatic pressure acting on the calving face in the force balance these observations demonstrate that the dynamics of bowdoin glacier are sensitive to small perturbations occurring near the calving front