correlation scales objective mapping and absolute geostrophic flow in the california current the spatial covariances of the time dependent density and geostrophic velocity fields off southern california are determined from a unique set of repeated hydrographic observations 44 cruises made by the california cooperative oceanic fisheries investigations from 1984 to 1994 the covariances and objective analysis are used to combine direct velocity observations from shipboard acoustic doppler current profiler adcp measurements made on a recent survey october 1993 with hydrographic observations the analysis reduces ageostrophic noise in the adcp velocities by smoothing and enforcing horizontal nondivergence additionally the velocities are mapped over scales that are dynamically consistent with the hydrography maximum surface geostrophic flow in the california current in october 1993 is about 35 cm s 1 50 larger than that estimated assuming a 500 m level of no motion absolute flow at 500 m is o 10 cm s 1 and indicates that the surface eddy field penetrates through the thermocline uncertainty in the geostrophic reference calculated from the adcp measurements is of o 4 cm s 1 the velocity residual objectively analyzed minus raw adcp estimates exhibits smaller correlation scales than the geostrophic flow

analysis of the mesoscale structure in the imecocal region off baja california from hydrographic adcp and altimetry data we present geostrophic velocities obtained using hydrographic altimeter data and direct measurements of currents from 11 cruises offshore of baja california from january 2000 to july 2002 the study area was dominated by meanders and eddies in geostrophic balance two mechanisms of eddy generation were observed the first associated with the geometry of the coastline and the second a product of the cooling of the california current and the california undercurrent from the south there were two persistent eddies observed during the study the first eddy was offshore of bahia vizcaino and had an anticyclonic circulation situated in the southern region the rotation of the second eddy was dependant on which current was first to enter the transition zone along the coast spring was a transition period characterized by the formation of meanders the summer brought a period of eddy generation along the coast autumn and winter were marked by a separation of eddies from the coast and their subsequent drift towards the west the phase velocity of the mesoscale eddies was in accordance with the theory of the linear propagation of a rossby wave

greenland flow variability from ice sheet wide velocity mapping using radarsat synthetic aperture radar data we have mapped the flow velocity over much of the greenland ice sheet for the winters of 2000 01 and 2005 06 these maps provide a detailed view of the ice sheet flow including that of the hundreds of glaciers draining the interior the focused patterns of flow at the coast suggest a strong influence of bedrock topography differences between our two maps confirm numerous early observations of accelerated outlet glacier flow as well as revealing previously unrecognized changes the overall pattern is one of speed up accompanied by terminus retreat but there are also several instances of surge behavior and a few cases of glacier slowdown comprehensive mappings such as these at regular intervals provide an important new observational capability for understanding ice sheet variability

geochemistry mineralogy and technological properties of coals from rio maior portugal and penarroya spain basins abstract this study focuses on the geochemistry and mineralogy of pliocene lignites from the rio maior basin portugal and of late westphalian bituminous and anthracite coals from the penarroya basin spain major mineral phases present in the rio maior lignites are quartz and clay minerals with minor amounts of other detrital minerals depending on the sedimentary environment and the source of the detrital input the concentration of rb cs sc v u and gd in lignites is higher than the maximum value established for the usual worldwide concentration range for coal geochemical affinity study for major and trace elements in rio maior established three major associations i aluminium silicate affinity fe mg na k li rb sc zr v cr co ni se pb sb gd and tb ii the sulphur affinity mo and as and iii organic affinity sr ca mn ba and u ce and cs affinities could not be explained with the available data in the penarroya bituminous coals the main mineral phases identified were quartz and clay minerals kaolinite and illite minor traces of anatase and epigenetic carbonates elements with inorganic affinity fe mg na k ti li rb cs ba sc zr v cr co ni pb u se ce gd tb cu have a high to medium aluminium silicate affinity anomalous concentrations of li rb cs sc v and cr could be related to the input of detrital minerals from the precambrian and lower palaeozoic rocks in the northeastern part of penarroya basin anthracites from the penarroya basin have the following mineral phases calcium iron and magnesium carbonates clay minerals and quartz as well as traces of apatite and of pyrite carbonates and some kaolinite are clearly epigenetic as a consequence of fluid circulation related to magmatic activity two main geochemical associations were found i aluminium silicate affinity na k ti rb cs ba sc cr mo ni cd as sb se ce gd tb cu and ii carbonate affinity ca mg fe v mn sr an anomalous amount of mn and v is considered to be related with the circulation of magmatic fluids the geochemical and mineralogical variations observed were primarily related to coal rank in the penarroya basin whilst paleoenvironmental depositional conditions were more important in the rio maior basin the chemical composition of the high temperature ashes is related to the trend followed by the ash fusion temperatures and to the predictive indices associated with slagging and fouling propensities these indices indicate low to medium slagging and fouling propensities for all the coals studied

observations and models of inertial waves in the deep ocean the structure of the inertial peak in deep ocean kinetic energy spectra is studied here records were obtained from polymode arrays deployed in the western north atlantic ocean 40 w to 70 w 15 n to 42 n the results are interpreted both in terms of local sources and of turning point effects on internal waves generated at lower latitudes in most of the data there is a prominent inertial peak slightly above f however the peak height above the background continuum varies with depth and geographical environment three classes of environment and their corresponding spectra emerge from peak height variations class 1 is the 1500 m level near the mid atlantic ridge with the greatest peak height of 18 db class 2 includes a the upper ocean depth less than 2000 m b the deep ocean depth greater than 2000 m over rough topography and c the deep ocean underneath the gulf stream with intermediate peak height of 11 5 db class 3 is the deep ocean over smooth topography with the lowest peak height of 7 5 db near f the horizontal coherence scale is 0 60 km at depths from 200 m to 600 m and the vertical coherence scale is 0 200 m in the lower part of the main thermocline and 0 1000 m in the deep water the phase difference suggests a downward energy propagation in the lower thermocline and standing waves in the deep water a one turning point model is developed to describe inertial waves at mid latitudes based on the assumption that inertial waves are randomly generated at lower latitudes global generation where their frequency wave number spectrum is given by the model of garrett and munk 1972 1975 using the globally valid wave functions obtained by munk and phillips 1968 various frequency spectra near f are calculated numerically the model yields a prominent inertial peak of 7 db in the horizontal velocity spectrum but no peaks in the temperature spectrum the model is latitudinally dependent the frequency shift and bandwidth of the inertial peak decrease with latitude energy level near f is minimum at about 30 and higher at low and high latitudes the observations of class 3 can be well described by the model a low zonal wave number cutoff is required to produce the observed frequency shift of the inertial peak the differences between the global generation model and the observations of class 1 and class 2 are interpreted as the effects of local sources a locally forced model is developed based on the latitudinal modal decomposition of a localized source function asymptotic eigensolutions of laplace s tidal equation are therefore derived and used as a set of expansion functions the forcing is through a vertical velocity field specified at the top or bottom boundaries of the ocean for white noise forcing the horizontal velocity spectrum of the response has an inertial peak which diminishes in the far field with the forcing located at either the surface or the bottom several properties of the class 2 observations can be described qualitatively by a combination of the global and local models the reflection of inertial waves from a turbulent benthic boundary layer is studied by a slab model of given depth frictional effects are confined to the boundary layer and modeled by a quadratic drag law for given incident waves reflection coefficients are found to be greater than 0 9 for the long waves which contain most of the energy this result suggests that energy containing inertial waves can propagate over great distance as is required by the validity of the model of global generation

coal facies studies in spain this work is a synthesis of the distribution of the main coal basins and sub basins in spain as well as the research carried out on their coal facies the coal fields are distributed through the paleozoic mainly pennsylvanian mesozoic cretaceous and cenozoic times peats also exist in the southeast spain granada area although these types of deposits are not included in this review spanish coal basins are both of a paralic and intramontane type and the coal rank is highly variable from lignite in the case of the younger coal seams to anthracite for those of carboniferous age

a barotropic inverse tidal model for the arctic ocean 1 we describe high resolution 5 km grid linear dynamics and inverse models of arctic ocean barotropic tides obtained with the osu tidal inversion software otis package the 8 constituent dynamics based model uses the latest ibcao bathymetry and open boundary forcing from the recent tpxo 6 2 global barotropic tidal solution this model performs significantly better than the present benchmark arctic tidal model 14 km grid by z kowalik and a proshutinsky as judged by comparisons with 300 coastal tide gauges the greatest improvements are found in the canadian arctic archipelago nares strait and the baffin bay and labrador sea and can be explained by the higher resolution of the new model in these topographically complex regions the new arctic inverse model assimilates coastal and benthic tide gauges and topex poseidon and ers altimetry for further improvements of the 4 dominant constituents m2 s2 k1 and o1

spreading of red sea overflow waters in the indian ocean as a result of its remarkably high salinity and despite its small volume input remnants of red sea water rsw have been identified in the agulhas current over 6000 km distant of their source this provided the motivation to investigate the long term mean spreading of rsw throughout the indian ocean using a comprehensive set of observations taken from the national oceanographic data center archives and from the world ocean circulation experiment hydrographic program for the indian ocean after emerging from the gulf of aden into the arabian sea rsw spreads predominantly southwestward along the african continental slope as indicated by strongly inclined isohalines across the arabian sea there is some monsoon variability so that during the winter monsoon there is more rsw present in the gulf of aden and an intensification of southward spreading along the western boundary between 12 and 5 n elsewhere the intermediate depth salinity field of the indian ocean appears relatively stationary between 5 and 10 s in the region of the south equatorial current isohalines of the rsw layer become quasi zonal across the width of the indian ocean only dipping southward toward the western boundary west of 50 e south of here there is a strong tongue of rsw spreading southward through the mozambique channel and into the agulhas current these conclusions concur with previous localized investigations of intermediate water properties using a simple mixing model the percentage of rsw throughout the indian ocean was quantified it was found that the flux of salt into the gulf of aden from the red sea is similar to that estimated to cross 32 s in the agulhas current this result implies that all the rsw which is mixed into the interior of the indian ocean may eventually be exported at the western boundary furthermore it implies that rsw is the dominant component of the salt budget for the intermediate layer and that input from the indonesian seas and via diapycnic processes are small

the california current system in the southern california bight and the santa barbara channel recent observations in the santa barbara channel and over the california cooperative oceanic fisheries investigations calcofi southern california grid are used to examine seasonal circulation patterns in and near the southern california bight defined as the region east of the santa rosa ridge and including the santa barbara channel poleward flow relative to 500 m is found throughout the bight in all seasons except for spring and all subregions except the western part of the santa barbara channel in spring there is equatorward flow throughout the bight at all depths to 500 m though it tends to be surface or midcolumn intensified equatorward flow offshore of the bight present in all seasons narrows and accelerates into a jet like feature and simultaneously moves close to the santa rosa ridge in summer current meter data from the eastern entrance to the santa barbara channel are consistent with the seasonal results from the calcofi data and further show an upward propagation of phase at annual period with a phase speed of 1 to 2 m d 1 comparison with the calcofi ship winds suggests that poleward flow in the bight may be the result of positive wind stress curl through a sverdrup balance though the observed transport is only about 75 of that expected from the curl amplitude equatorward flow in the bight may be the result of coastal upwelling though the transport is larger than expected from the relatively weak winds in the bight and the offshore extent of the equatorward flow is about 10 rossby radii farther than might be expected for linearized coastal upwelling equatorward flow outside the bight cannot be explained as a sverdrup flow because the wind stress curl is positive throughout most of the region upward propagation of phase and downward propagation of energy may be indicative of forcing by remote wind equatorward of the bight given the complexity of possible forcing mechanisms for circulation in and near the bight a model that includes effects of remote wind forcing ekman pumping and topography is needed to explain the observations in a satisfactory way

fast retreat of zachariae isstrom northeast greenland after 8 years of decay of its ice shelf zachariae isstrom a major glacier of northeast greenland that holds a 0 5 meter sea level rise equivalent entered a phase of accelerated retreat in fall 2012 the acceleration rate of its ice velocity tripled melting of its residual ice shelf and thinning of its grounded portion doubled and calving is now occurring at its grounding line warmer air and ocean temperatures have caused the glacier to detach from a stabilizing sill and retreat rapidly along a downward sloping marine based bed its equal ice volume neighbor nioghalvfjerdsfjorden is also melting rapidly but retreating slowly along an upward sloping bed the destabilization of this marine based sector will increase sea level rise from the greenland ice sheet for decades to come

characterizing the transition from balanced to unbalanced motions in the southern california current author s chereskin teresa k rocha cesar b gille sarah t menemenlis dimitris passaro marcello

petrographic composition and depositional environments of cretaceous coals and coal measures in the middle benue trough of nigeria abstract cretaceous coals and coal measure sequences in the area around the obi lafia part of the middle benue trough of nigeria were studied petrographically the turonian santonian awgu formation and the maastrichtian lafia formation constitute the sedimentary successions in both outcrop and borehole profiles of this area maceral analyses of 32 coal samples from this area allow subdivision of the coal beds into three different coal facies the vitrinite fusinite coal facies the trimaceritic coal facies and the shaly coal facies in the vitrinite fusinite coal facies vitrinite constitutes on average 67 3 liptinite 4 2 inertinite 17 1 and mineral matter 11 4 the trimaceritic coal facies has 42 3 vitrinite 22 4 liptinite 23 8 inertinite and 11 5 mineral matter in the shaly coal facies vitrinite constitutes 29 9 liptinite inertinite and mineral matter are 13 8 22 0 and 34 3 respectively correlation of the distribution of microfossils in the interseam sediments with the tissue preservation gelification groundwater and vegetation indices of the coal facies indicates that the vitrinite fusinite coal facies was deposited in wet forest swamp subenvironments along and within lagoons the trimaceritic facies was deposited in limno telmatic clastic marsh subenvironments in lower delta plains the shaly coal facies shows characteristics of various subenvironments but generally tends to be more marine than the other two facies

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

seasonal to multiyear variability of glacier surface velocity terminus position and sea ice ice melange in northwest greenland glacier ice discharge which depends on ice velocity and terminus fluctuations is a primary component of greenland ice sheet mass loss some research suggests that ice melange influences terminus calving in turn affecting glacier velocity the details and broad spatiotemporal consistency of these relationships however is undetermined focusing on 16 northwestern greenland glaciers during 2009 through summer 2014 we examined seasonal surface velocity changes glacier terminus position and sea ice and ice melange conditions for a longer term analysis we also produced extended records of four glaciers from 1999 to 2014 there is a strong correspondence between seasonal near terminus sea ice melange conditions and terminus change with rigid ice melange conditions associated with advance and open water associated with retreat extended sea ice free periods and reduced rigid melange are also linked with anomalously large terminus retreat in all but one case sustained multiyear retreat of greater than 1 km during both the 15 year and 6 year records was accompanied by interannual velocity increases seasonal velocity patterns however correspond more strongly with runoff changes than terminus behavior projections of continued warming and longer sea ice free periods around greenland indicate that notable retreat over wide areas may continue this sustained retreat likely will contribute to multiyear speedup longer melt seasons and earlier breakup of melange may also alter the timing of seasonal ice flow variability

deeply incised submarine glacial valleys beneath the greenland ice sheet the bed topography beneath the greenland ice sheet controls the flow of ice and its discharge into the ocean a combination of sparse radar soundings of ice thickness and high resolution ice motion data suggest that many submarine ice covered valleys extend significantly deeper below sea level and farther inland than thought

grounding line migration from 1992 to 2011 on petermann glacier north west greenland we use satellite radar interferometry to investigate changes in the location of the petermann glacier grounding line between 1992 and 2011 the grounding line location was identified in 17 quadruple difference interferograms produced from european remote sensing ers 1 2 data the most extensive time series assembled at any ice stream to date there is close agreement 20 6 cm between vertical displacement of the floating ice shelf and relative tide amplitudes simulated by the arctic ocean dynamics based tide model 5 aodtm 5 arctic tide model over the 19 a period the groundling line position varied by 470 m on average with a maximum range of 7 0 km observed on the north east margin of the ice stream although the mean range 2 8 km and variability 320 m of the grounding line position is considerably lower if the unusually variable north east sector is not considered our observations demonstrate that large isolated movements cannot be precluded thus sparse temporal records should be analysed with care the grounding line migration observed on petermann glacier is not significantly correlated with time r 2 0 22 despite reported ice shelf thinning and episodes of large iceberg calving which suggests that unlike other ice streams on the south west margin of the greenland ice sheet petermann glacier is dynamically stable

a view of the 1993 1994 california current based on surface drifters floats and remotely sensed data near surface drifters were deployed in the california current system during the period 1993 1994 in order to study mean and eddy currents the deployment scheme allowed a 2 year period where data density was high enough to make meaningful estimates of eddy statistics and of seasonal mean currents and variances on a 5 grid eddy variability which tended to be isotropic was higher near the coast standard deviations around 0 2 m s 1 and decreased offshore down to 0 1 m s 1 seasonal mean surface flow west of california was southward during all seasons if a davidson current existed during 1993 1995 it was probably either short lived or only found closer to the coast than our study area i e within 100 150 km of shore in some cases drifter populations within a discrete feature were high enough to allow some detailed resolution of its behavior we note a tendency for individual eddies which can last for up to 3 5 months to drift westward at rates of o 5 km day 1 not all eddies in the region are surface intensified there is clear evidence for at least the occasional presence of a thin meandering southward jet in the region that can be 1000 km or more long this jet can be identified with that found in the coastal transition zone program in association with cool filaments the jet appears to become broader and slower south of point conception we hypothesize on the basis of others results as well as ours that the eddies that are strongest at the surface result primarily from instabilities on a southward alongshore mean current and that eddies that are maximal at depth are spawned by the northward undercurrent

poleward flows in the southern california current system glider observations and numerical simulation 1 three years of continuous spray glider observations in the southern california current system ccs are combined with a numerical simulation to describe the mean and variability of poleward flows in the southern ccs gliders provide upper ocean observations with good across shore and temporal resolution along two across shore survey lines while the numerical simulation provides a dynamically consistent estimate of the ocean state persistent poleward flows are observed in three areas within 100 km of the coast at point conception within the southern california bight scb and offshore of the scb and the santa rosa ridge srr poleward transport by the flows within the scb and offshore of the srr exceeds the poleward transport off point conception suggesting that the poleward flows are not continuous over the 225 km between observation lines the numerical simulation shows offshore transport between the survey lines that is consistent with some of the poleward flow turning offshore before reaching point conception the poleward current offshore of the srr is unique in that it is strongest at depths greater than 350 m and it is observed to migrate westward away from the coast this westward propagation is tied to westward propagating density anomalies originating in the scb during the spring summer upwelling season when wind stress curl is most strongly positive the across shore wave number frequency and phase speed of the westward propagation and the lack of across shore transport of salinity along isopycnals are consistent with first mode baroclinic rossby dynamics

basal terraces on melting ice shelves ocean waters melt the margins of antarctic and greenland glaciers and individual glaciers responses and the integrity of their ice shelves are expected to depend on the spatial distribution of melt the bases of the ice shelves associated with pine island glacier west antarctica and petermann glacier greenland have similar geometries including kilometer wide hundreds of meter high channels oriented along and across the direction of ice flow the channels are enhanced by and constrain oceanic melt new meter scale observations of basal topography reveal peculiar glaciated landscapes channel flanks are not smooth but are instead stepped with hundreds of meters wide flat terraces separated by 5 50 m high walls melting is shown to be modulated by the geometry constant across each terrace changing from one terrace to the next and greatly enhanced on the 45 inclined walls melting is therefore fundamentally heterogeneous and likely associated with stratification in the ice ocean boundary layer challenging current models of ice shelf ocean interactions

mean structure and seasonal variability of the poleward undercurrent off southern california 1 the magnitude location and extent of the california undercurrent cuc off southern california is investigated using cruises of the california cooperative oceanic fisheries investigations calcofi from 1993 to 2003 which provide hydrographic biochemical and acoustic doppler current profiler adcp velocity data on a quarterly basis this study is the first use of the decade long adcp time series it improves on prior geostrophic calculations by providing an absolute velocity reference for estimates of currents and transport the long term mean reveals two undercurrent cores in the region south of point conception and north of baja california one in the region of the continental slope within the southern california bight scb and a second off the santa rosa ridge srr a single core is observed off point conception spiciness is found to be a good indicator of the presence of the cuc however direct velocity observations or a deep reference level are required to resolve the full strength of the cuc cores in particular the core off the srr would be almost entirely missed by geostrophic calculations relative to 500 m the maximum depth sampled by calcofi the undercurrent transport off point conception is estimated to be about 1 7 0 1 sv slightly less than the sum of that estimated for the scb 1 0 0 1 sv and that estimated off the srr 1 1 0 1 sv and consistent with some of the flow turning offshore at point conception the cuc in the scb is strongest in summer while that off the srr is strongest in fall the cuc off point conception is strong in both summer and fall reflecting the confluence of these two branches interannual variability is also present and the velocity and spiciness of the cuc appear to peak during el nino periods

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

northern larsen ice shelf antarctica further retreat after collapse changes of larsen ice shelf antarctica and the surrounding glaciers after its collapse in 1995 were investigated using satellite radar imagery with emphasis onchanges in the glaciers which previously nourished the ice shelf north of seal nunataks the large glaciers retreated several kilometres inland of the previousgrounding line the velocity field of drygalski glacier the largest glacier in this area was mapped by means of interferograms derived from pairs of ers syntheticaperture radar images from 1995 and 1999 the main part of the glacier showed significant acceleration of flow over these 4 years with an increase of veocity upto three fold at the terminus similar accelerations were observed by means of interferometry on several other grounded glaciers suggesting that the removal ofice shelves could lead to an effect on eustatic sea level for larsen b the northernmost surviving part of larsen ice shelf the retreat of the ice front to october2000 is documented

tidal modulation of buoyant flow and basal melt beneath petermann gletscher ice shelf greenland a set of collocated in situ oceanographic and glaciological measurements from petermann gletscher ice shelf greenland provides insights into the dynamics of under ice flow driving basal melting at a site 16 km seaward of the grounding line within a longitudinal basal channel two conductivity temperature ct sensors beneath the ice base and a phase sensitive radar on the ice surface were used to monitor the coupled ice shelf ocean system a 6 month time series spanning 23 august 2015 to 12 february 2016 exhibited two distinct periods of ice ocean interactions between august and december radar derived basal melt rates featured fortnightly peaks of 15 m yr 1 which preceded the arrival of cold and fresh pulses in the ocean that had high concentrations of subglacial runoff and glacial meltwater estimated current speeds reached 0 20 0 40 m s 1 during these pulses consistent with a strengthened meltwater plume from freshwater enrichment such signals did not occur between december and february when ice ocean interactions instead varied at principal diurnal and semidiurnal tidal frequencies and lower melt rates and current speeds prevailed a combination of estimated current speeds and meltwater concentrations from the two ct sensors yields estimates of subglacial runoff and glacial meltwater volume fluxes that vary between 10 and 80 m3 s 1 during the ocean pulses area average upstream ice shelf melt rates from these fluxes are up to 170 m yr 1 revealing that these strengthened plumes had already driven their most intense melting before arriving at the study site

large scale ice flow over a viscous basal sediment theory and application to ice stream b antarctica recent seismic studies of ice stream b antarctica and field analysis of mid latitude glacial deposits suggest that deformable basal sediments e g water saturated till are important in determining ice sheet flow if the ratio of till viscosity to effective ice viscosity is small vertical shear associated with horizontal flow is confined to the deforming bed alone ice flow over a deformable bed is thus akin to that of floating ice shelves because ice shelves flow over inviscid seawater for some antarctic ice streams and possibly for portions of the late wisconsin ice sheets in north america and eurasia basal drag associated with deforming basal sediment does not induce significant vertical gradients of horizontal velocity instead basal drag affects the flow as if it were a horizontal body force balanced by longitudinal and transverse deviatoric stress gradients comparison of the observed flow of ice stream b to finite element simulations incorporating a viscous basal till suggest that a simple till theology is sufficient to explain the current velocity profile these simulations also highlight the importance of horizontal deviatoric stress in regions where driving stress and basal stress do not locally balance while bed deformation is critical to ice stream existence sensitivity tests suggest that ice shelf back pressure is still a crucial control affecting ice stream response to atmospheric and oceanic climate

changes in ice dynamics elevation and mass discharge of dinsmoor bombardier edgeworth glacier system antarctic peninsula abstract the northern antarctic peninsula is one of the fastest changing regions on earth the disintegration of the larsen a ice shelf in 1995 caused tributary glaciers to adjust by speeding up surface lowering and overall increased ice mass discharge in this study we investigate the temporal variation of these changes at the dinsmoor bombardier edgeworth glacier system by analyzing dense time series from various spaceborne and airborne earth observation missions precollapse ice shelf conditions and subsequent adjustments through 2014 were covered our results show a response of the glacier system some months after the breakup reaching maximum surface velocities at the glacier front of up to 8 8 m d in 1999 and a subsequent decrease to 1 5 m d in 2014 using a dense time series of interferometrically derived tandem x digital elevation models and photogrammetric data an exponential function was fitted for the decrease in surface elevation elevation changes in areas below 1000 m a s l amounted to at least 130 15 m between 1995 and 2014 with change rates of 3 15 m a between 2003 and 2008 current change rates 2010 2014 are in the range of 1 7 m a mass imbalances were computed with different scenarios of boundary conditions the most plausible results amount to 40 7 3 9 gt the contribution to sea level rise was estimated to be 18 8 1 8 gt corresponding to a 0 052 0 005 mm sea level equivalent for the period 1995 2014 our analysis and scenario considerations revealed that major uncertainties still exist due to insufficiently accurate ice thickness information the second largest uncertainty in the computations was the glacier surface mass balance which is still poorly known our time series analysis facilitates an improved comparison with grace data and as input to modeling of glacio isostatic uplift in this region the study contributed to a better understanding of how glacier systems adjust to ice shelf disintegration

petrography and depositional conditions of the 64 65 coal seam in the intrasudetic basin sw poland abstract variation in petrological composition of the coal of the 64 65 seam has been studied two types of vertical lithotype succession were distinguished the first type is represented by bright lithotypes interlayered with clastic partings while the second one shows a succession of lithotypes from bright to dull between clastic partings the occurrence of these two types is believed to be the result of a different rate of subsidence a trend of upward decreasing vitrinite content has been observed in the seam with the second type of the vertical succession this pattern was frequently interrupted by clastic partings this tendency was not developed in the seam of the first succession type on the basis of microlithotype and maceral composition it is found that the 64 65 seam represents a wide range of peat forming environments from telmatic forest moor to open moor almost all bright banded and banded coals were deposited in telmatic forest moor facies while dull banded coal depending upon its petrographic composition represents telmatic forest moor telmatic reed moor limno telmatic forest moor and limno telmatic reed moor dull coal represents only an open moor environment facial analysis of clastic sediments surrounding the seam revealed that there was a relationship between coal and clastic sedimentation the features of the seam are strongly related to sub peat topography distance from active distributaries and stability of the area sulfur and ash contents as well as character of clastic partings and petrology of the seam suggest conditions typical for groundwater and surface dominated swamps with ph a little higher than 4

the response of petermann glacier greenland to large calving events and its future stability in the context of atmospheric and oceanic warming this study assesses the impact of a large 2010 calving event on the current and future stability of petermann glacier greenland and ascertains the glacier s interaction with different components of the climate and ocean system we use a numerical ice flow model that captures the major aspects of the glacier s mass budget the resistive forces controlling glacier flow and includes dynamic calving satellite observations and model results show that the recent break off of 25 of the floating tongue did not result in a significant glacier speed up due to the low lateral resistance of this relatively wide and thin ice tongue we demonstrate that seasonal speed up at petermann glacier is mainly driven by meltwater lubrication rather than freeze up conditions in the fjord results also show that sub shelf ocean melt may have a profound effect on the future stability of petermann glacier emphasizing the urgent need for more observations and a better understanding of fjord temperature variability and circulation

separation of tidal and subtidal currents in ship mounted acoustic doppler current profiler observations a simple method is developed to analyze current measurements obtained from a moving platform the need for this is motivated by the now common use of the ship mounted acoustic doppler current profiler adcp to acquire absolute velocity data during an oceanographic survey of a given region the full potential of this new measurement technique is severely hindered when the presence of high frequency phenomena e g tidal or inertial motions prevents a clear visualization of the lower frequency current structure of interest our analysis method is based on a spatial interpolation scheme using arbitrary functions that allows for the tidal current time variability which then permits the tide induced motions to be subtracted from the adcp data to yield the subtidal current field the method also allows nearby moored and drifter current measurements if available to be combined with the shipboard adcp observations in a single analysis to obtain the best description of the tidal and subtidal currents to illustrate this method we present results from the analysis of adcp data taken during oceanographic surveys in two different continental shelf regions the east china sea and the amazon shelf a 5 day conductivity temperature depth ctd and adcp survey was made in the east china sea near the mouth of the yellow sea during january 1986 there the currents were essentially barotropic and dominated by the semidiurnal tide the adcp derived cotidal chart for the m2 12 42 hours component agrees well with existing charts derived empirically from sea level observations or from regional numerical models the adcp derived steady flow is also consistent with the observed density field and indicates little flow in or out of the yellow sea and a transport of about 1 sv toward the tsushima strait two ctd adcp surveys lasting 21 and 23 days were conducted over the amazon shelf during march and may 1990 simultaneously moored current observations were also obtained at three locations along a cross shelf array 200 km north of the amazon river mouth for a common period of at least 2 months february 12 to april 13 over the shelf tidal and subtidal currents were comparable in magnitude our analysis indicates that the tidal currents were essentially barotropic semidiurnal and polarized in the cross shelf direction increasing in magnitude toward the inner shelf where current values of more than 2 m s are common the adcp derived steady currents were aligned in the along shelf direction and strongly influenced by the north brazil current nbc during both adcp surveys the northwestward flowing nbc was transporting more than 2 sv over the shelf at depths shallower than 100 m

decomposing observations of high frequency radar derived surface currents by their forcing mechanisms decomposition techniques and spatial structures of decomposed surface currents 1 surface current observations from a high frequency radar network deployed in southern san diego are decomposed according to their driving forces pure tides and their neighboring off band energy local winds and low frequency several superposed ocean responses are present as a result of the complicated bottom topography and relatively weak winds off southern san diego as opposed to coastal regions where circulation can be explained by a dominant forcing mechanism this necessitates an application of a statistical decomposition approach surface currents coherent with pure tides are calculated using harmonic analysis locally wind driven surface currents are estimated by regression of observed winds on observed surface currents the dewinded and detided surface currents are filtered by weighted least squares fitting assuming white noise and three colored signal bands low frequency band less than 0 4 cycles per day and near tidal peaks at the diurnal k1 and semidiurnal m2 frequencies the spatial and temporal variability of each part of the decomposed surface currents is investigated in terms of ocean response to the driving forces in addition the spatial correlations of individual components exhibit gaussian and exponential shapes with varying decorrelation length scales

lower satellite gravimetry estimates of antarctic sea level contribution a new model of glacial isostatic adjustment used in conjunction with grace satellite data suggests that ice loss from antarctica is contributing 0 19 millimetres per year to global mean sea level which is substantially less than previous grace based estimates estimates for recent mass loss from antarctica vary widely making it difficult to calculate any subsequent contributions to sea level rise one prominent approach uses the grace gravity recovery and climate experiment satellites to detect changes in gravity but the final estimates are dependent on the modelled response of the continent to changes in ice loading over time and to changes in lithospheric elastic rebound matt king and colleagues apply a new model of this glacial isostatic adjustment to the grace data and estimate antarctic mass loss between 2002 and 2010 to be about 69 gigatonnes per year much lower than previous estimates and equivalent to an annual sea level rise of about 0 2 millimetres recent estimates of antarctica s present day rate of ice mass contribution to changes in sea level range from 31 gigatonnes a year gt yr 1 ref 1 to 246 gt yr 1 ref 2 a range that cannot be reconciled within formal errors3 time varying rates of mass loss2 4 5 6 contribute to this but substantial technique specific systematic errors also exist3 in particular estimates of secular ice mass change derived from gravity recovery and climate experiment grace satellite data are dominated by significant uncertainty in the accuracy of models of mass change due to glacial isostatic adjustment7 8 gia here we adopt a new model of gia developed from geological constraints which produces gia rates systematically lower than those of previous models and an improved fit to independent uplift data9 after applying the model to 99 months from august 2002 to december 2010 of grace data we estimate a continent wide ice mass change of 69 18 gt yr 1 0 19 0 05 mm yr 1 sea level equivalent this is about a third to a half of the most recently published grace estimates2 5 which cover a similar time period but are based on older gia models plausible gia model uncertainties and errors relating to removing longitudinal grace artefacts destriping confine our estimate to the range 126 gt yr 1 to 29 gt yr 1 0 08 0 35 mm yr 1 sea level equivalent we resolve 26 independent drainage basins and find that antarctic mass loss and its acceleration is concentrated in basins along the amundsen sea coast outside this region we find that west antarctica is nearly in balance and that east antarctica is gaining substantial mass

a comparative modeling study of the brunt ice shelf stancomb wills ice tongue system east antarctica two diagnostic dynamic thermodynamic ice shelf models are applied to the brunt ice shelf stancomb wills ice tongue system located off caird coast coats land antarctica the brunt ice shelf stancomb wilis ice tongue system is characterized as a thin unbounded ice shelf with an atypical and highly heterogeneous structure in contrast to other ice shelves a composite mass of icebergs that calved at the grounding line and were then locked within fast sea ice exists between the fast moving stancomb wills ice stream and the slow moving brunt ice shelf we simulate the present flow regime of the ice shelf that results from the ice thickness distribution and the inflow at the grounding line with two different models and compare the model results with feature tracking and insar flow velocities we then incorporate two observed features a rift and a shear margin into the models with two different approaches and demonstrate the effects of variations in numerical values for the shear strength and viscosity in these zones on the simulated velocity field a major result is that both kinds of implementation of the rifts lead to similar effects on the entire velocity field while there are discrepancies in the vicinity of the rifts

currents in haida eddies abstract measurements by a variety of sensors provided details of flow in haida eddies which are anticyclonic mesoscale features that move slowly westward through the eastern gulf of alaska these measurements provided the best comparison and analysis to date of mesoscale eddy currents by various ship and satellite based sensors the relative contribution of barotropic currents to the total eddy orbital motion at ocean surface was found to be up to 16 based on comparison of total sea surface height anomalies measured by satellite altimetry and baroclinic elevation of the ocean surface detected by ship based measurements of density through the eddies acoustic doppler current meters on a ship transiting two haida eddies found that the observed currents were considerably different from the expected orbital motion perhaps due to inertial currents or to previously undetected barotropic structure lagrangian drifters drogued near the ocean surface in two eddies revealed that inertial currents in late spring and summer were similar in magnitude to eddy orbital motion and larger than eddy currents following periods of strong winds drifter tracks also provided evidence that the eddy rotated as a solid body constant vorticity within 30 40 km of the eddy center and that material could remain in these central waters for at least 2 months in summer for most of the 2 month period during which the drifters were tracked they steadily moved away from the center of the eddy implying a gradual uplift of the pycnocline within the eddy core due to slow decay of the eddy or to its uplift as it moved westward into denser ambient waters

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

sedimentological and petrographical characteristics of cretaceous strandplain coals a model for coal accumulation from the north american western interior seaway abstract coal seams formed on many cretaceous wave dominated strandplain sediments in north america are characterized by great lateral continuity tens to hundreds of kilometres substantial thicknesses up to 12 m relatively low ash and sulphur contents the coals formed behind an active shoreline in areas undergoing subsidence due to shale compaction and dewatering the zone of peat accumulation was remote from the shoreline and storm tidal inundations and generally protected from fluvial flooding if the rate of subsidence was too great lakes formed and peat did not accumulate statistical evaluation of petrographic properties by correspondence analysis of the lower cretaceous coals show that the strandplain coals form distinctive petrographic groups that are characterized by relatively low vitrinite contents and high inertinite contents semifusinite and inertodetrinite dominate in the inertinite maceral group liptinite contents are negligible tissue preservation indices and gelification indices indicate for the strandplain coals a forest type paleodepositional environment in which a relatively low water table allowed the accumulation of oxidized and partly oxidized components fusinite and semifusinite significant amounts of detrital components such as inertodetrinite and vitrinite b are diagnostic that some transportation of the organic material took place prior to deposition comparison of coal facies and depositional environments from permian coals of australian show that the lower cretaceous strandplain coals have petrographic similarities to coals that were formed under regressive back barrier conditions in the permian due to differences in nomenclature previously interpreted regressive back barrier environments may be similar to the strandplain environments discussed here

a mesoscale eddy dipole in the offshore california current there is a transition zone in the california current system between inshore coastal and offshore oceanic flow this transition zone is associated with the main core of the california current and is populated with offshore mesoscale eddies the structure of isolated eddies and dipole eddy pairs found within the transition zone is examined using water mass analysis spiciness and dissolved oxygen the analyses show that these offshore mesoscale eddies have cores which contain california undercurrent water these observations and independent observations of the sitka eddy near sitka alaska support the conclusion that a bathymetrically induced instability of the california undercurrent is a likely generation mechanism for the offshore eddies this conclusion also is consistent with mathematical models of eddy generation in a subsurface poleward baroclinic current the similarity between long term mean conditions caicofi conditions observed during january 1981 and july 1985 and those of the sitka eddy coupled with the bathymetric effects provides a plausible explanation for the recurrence of offshore mesoscale eddies at preferred locations within the transition zone

evidence of recent climatic warming on the eastern antarctic peninsula air temperatures at the stations marambio esperanza and matienzo have been analysed to investigate recent climate change on the eastern part of the antarctic peninsula the data are compared with the station orcadas on the south orkney islands the longest record available in antarctica and with faraday on the western coast of the peninsula though the interannual variability is comparatively high and the stations are located in different climatic regimes a pronounced warming trend shows up in all records at marambio a temperature increase of 1 5 c has been observed since the beginning of the record in 1971 this is of similar magnitude as the increase at the station faraday on the west coast with 2 5 c for the longer period since 1945 the steady retreat and collapse of the northern larsen ice shelf coincided with this warming trend of particular importance for the ice shelf mass balance in this region are the summer temperatures which show a statistically significant warming trend at the stations marambio and esperanza the representativity of the summer temperatures of marambio for northern larsen ice shelf is confirmed by intercomparison with the parallel measurements at matienzo which is located on the ice shelf

committed sea level rise for the next century from greenland ice sheet dynamics during the past decade we use a three dimensional higher order ice flow model and a realistic initial condition to simulate dynamic perturbations to the greenland ice sheet during the last decade and to assess their contribution to sea level by 2100 starting from our initial condition we apply a time series of observationally constrained dynamic perturbations at the marine termini of greenland s three largest outlet glaciers jakobshavn isbrae helheim glacier and kangerdlugssuaq glacier the initial and long term diffusive thinning within each glacier catchment is then integrated spatially and temporally to calculate a minimum sea level contribution of approximately 1 0 4 mm from these three glaciers by 2100 based on scaling arguments we extend our modeling to all of greenland and estimate a minimum dynamic sea level contribution of approximately 6 2 mm by 2100 this estimate of committed sea level rise is a minimum because it ignores mass loss due to future changes in ice sheet dynamics or surface mass balance importantly 75 of this value is from the long term diffusive response of the ice sheet suggesting that the majority of sea level rise from greenland dynamics during the past decade is yet to come assuming similar and recurring forcing in future decades and a self similar ice dynamical response we estimate an upper bound of 45 mm of sea level rise from greenland dynamics by 2100 these estimates are constrained by recent observations of dynamic mass loss in greenland and by realistic model behavior that accounts for both the long term cumulative mass loss and its decay following episodic boundary forcing

petrographic facies analysis of lower and middle jurassic coal seams on the island of bornholm denmark abstract the lower middle jurassic succession on the island of bornholm denmark comprises a wide range of clastic depositional environments lacustrine fluvial coastal plain tidal flat and shallow marine the succession contains a number of coal seams and carbonaceous seams permitting 1 evaluation of the relationship between the different clastic environments and the associated environments of organic matter deposition and 2 assessment of facies changes within coal carbonaceous seams from different peat forming environments coal petrographic facies analysis was performed by maceral analysis of 61 coal samples from the lower jurassic ronne formation comprising the munkerup member sose bugt member and galgelokke member and from the upper lower middle jurassic baga formation the seams in the munkerup member and the sose bugt member are mainly allochthonous whereas those of the galgelokke member and the baga formation are mainly autochthonous the seams represent a broad spectrum of depositional environments from raised bogs to freshwater swamps and marine influenced swamps the facies are subaquatic to telmatic and terrestrial compositional differences between the seams are attributed to vegetation characteristics depositional facies and differences in the degradation of the organic matter the original peat forming vegetation was composed of cellulose rich shrub like plants tree ferns herbaceous plant communities and a varying amount of trees the peat forming environments represented by the carbonaceous seams in the munkerup and sose bugt members are compatible with the depositional environments indicated by the sediments however the coal seam in the galgelokke member represents deposition in a raised bog conflicting with sedimentary interpretation of a clastic tidal flat environment for the member the baga formation is considered to have formed under a lower upper delta plain or fluvial environment the composition of the coal seams supports the interpretation of a system of meandering streams in a upper delta plain to fluvial environment

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

review and update of the applications of organic petrology part 1 geological applications abstract organic petrology developed as coal petrology at the beginning of the 20th century dedicated mainly to the study of coals because of their utilization in industry coal petrology was then considered a branch of coal science later with the development of specialized nomenclature classification of coal components and the standardization and improvement of analytical microscopical methods this discipline expanded in interests and name becoming organic petrology organic petrology carries a broader context being as well a tool applied in the study of dispersed organic matter in sedimentary rocks due to its importance in exploration for fossil fuel resources at present organic petrology is a discipline widely recognized for its role in fundamental and applied research with respect to both coal utilization and in geosciences throughout the 20th century several important monographs have been published on the discipline of organic petrology including stach s textbook of coal petrology 1st edition 1935 2nd 1975 3rd 1982 updated as the more general organic petrology by taylor et al 1998 more recently the text applied coal petrology the role of petrology in coal utilization was published by suarez ruiz and crelling 2008 this review is the first in a two part review series that describes and updates the role of organic petrology in geosciences a second part complementing this one and focused on the applications of organic petrology to other scientific fields will follow

ocean circulation and properties in petermann fjord greenland the floating ice shelf of petermann glacier interacts directly with the ocean and isthought to lose at least 80 of its mass through basal melting based on three opportunisticocean surveys in petermann fjord we describe the basic oceanography the circulationat the fjord mouth the hydrographic structure beneath the ice shelf the oceanic heatdelivered to the under ice cavity and the fate of the resulting melt water the 1100 m deepfjord is separated from neighboring hall basin by a sill between 350 and 450 m deep fjord bottom waters are renewed by episodic spillover at the sill of atlantic water from thearctic glacial melt water appears on the northeast side of the fjord at depths between200 m and that of the glacier s grounding line about 500 m the fjord circulation isfundamentally three dimensional satellite imagery and geostrophic calculations suggest acyclonic gyre within the fjord mouth with outflow on the northeast side tidal flowsare similar in magnitude to the geostrophic flow the oceanic heat flux into the fjordappears more than sufficient to account for the observed rate of basal melting cold low salinity water originating in the surface layer of nares strait in winter intrudes farunder the ice this may limit basal melting to the inland half of the shelf the melt rate andlong term stability of petermann ice shelf may depend on regional sea ice cover andfjord geometry in addition to the supply of oceanic heat entering the fjord

coal facies and depositional environments of the aurora and cabeza de vaca units penarroya belmez espiel coalfield cordoba spain abstract the penarroya belmez ezpiel coalfield cordoba spain is a narrow strip 1 km wide and 50 km long parallel to the precambrian and lower palaeozoic structures of central iberian and ossa morena zones the strip corresponds to an intramontane basin the penarroya basin infilled with lower westphalian continental sediments the aurora and cabeza de vaca units situated in central eastern part correspond to the second major sedimentary event mainly represented by fluvial and lacustrine sequences including several coal bearing units the petrographic study of coals seams from the aurora unit seams 6 sucia and candelaria and the cabeza de vaca unit seams 1 3 bis 4 and 5 indicates a vitrinite rich composition despite the high content of detrital mineral matter in the majority of coals liptinite and inertinite present a very irregular distribution being liptinite mainly sporinite dominant over inertinite apart coals with very high proportions of carbominerite minerite vitrite is the dominant microlithotype nevertheless clarite and duroclarite constitute very important microlithotypes in some coal seams the paleomire systems deduced from petrographic composition and plots in coal facies diagrams vary from fen and swamps mainly associated with marginal lacustrine and alluvial and floodplain environments for seams 1 4 5 6 and sucia to more protected palaeomire systems for seams 3 bis and candelaria

observations and modeling of ocean induced melt beneath petermann glacier ice shelf in northwestern greenland we update observationally based estimates of subaqueous melt qm beneath petermann glacier ice shelf pgis greenland and model its sensitivity to oceanic thermal forcing tf and subglacial runoff qsg using the massachusetts institute of technology general circulation model mitgcm in a two dimensional domain with 20 m vertical and 40 m horizontal resolution at the grounding line we adjust the drag coefficient to match the observationally based qm with the inclusion of qsg the maximum melt rate qmmax is two times larger in summer and 1 3 larger annually than in winter qmmax increases above linear with tf and below linear with qsg we estimate that qmmax increased by 24 8 1 m yr beneath pgis from the 1990s to the 2000s from a 0 21 c warming in ocean temperature and a doubling in qsg hence contributing to its thinning if the pgis is removed we estimate that the modeled melt rate near the grounding line will increase 13 16 times

the impact of a changing southern hemisphere annular mode on antarctic peninsula summer temperatures since the mid 1960s rapid regional summer warming has occurred on the east coast of the northern antarctic peninsula with near surface temperatures increasing by more than 2 degrees c this warming has contributed significantly to the collapse of the northern sections of the larsen ice shelf coincident with this warming the summer southern hemisphere annular mode sam has exhibited a marked trend suggested by modeling studies to be predominantly a response to anthropogenic forcing resulting in increased westerlies across the northern peninsula observations and reanalysis data are utilized to demonstrate that the changing sam has played a key role in driving this local summer warming it is proposed that the stronger summer westerly winds reduce the blocking effect of the antarctic peninsula and lead to a higher frequency of air masses being advected eastward over the orographic barrier of the northern antarctic peninsula when this occurs a combination of a climatological temperature gradient across the barrier and the formation of a fohn wind on the lee side typically results in a summer near surface temperature sensitivity to the sam that is 3 times greater on the eastern side of the peninsula than on the west sam variability is also shown to play a less important role in determining summer temperatures at stations west of the barrier in the northern peninsula similar to 62 degrees s both at the surface and throughout the troposphere this is in contrast to a station farther south similar to 65 degrees s where the sam exerts little influence

multi decadal glacier surface lowering in the antarctic peninsula from approximately 400 glaciers of the western antarctic peninsula no in situ records of mass balance exist and their recent contribution to sea level is consequently poorly constrained we seek to address this shortcoming by using surface elevations from usgs and bas airborne 1948 2005 and aster spaceborne 2001 2010 stereo imagery combined by using a rigorous semi automated registration approach to determine multi decadal glacier surface elevation changes in the western antarctic peninsula for 12 glaciers all observed glaciers show near frontal surface lowering and an annual mean lowering rate of 0 28 0 03 m yr at the lower portion of the glaciers during the 4 decades following the mid 1960s with higher rates for the glaciers in the north west parts of the antarctic peninsula increased lowering of up to 0 6 m yr can be observed since the 1990s in close correspondence to increased atmospheric positive degree days in all cases surface lowering reduces to zero within 5 km of the glacier front at around 400 m altitude this lowering may have been at least partially compensated for by increased high altitude accumulation

2001 2009 elevation and mass losses in the larsen a and b embayments antarctic peninsula we investigate the elevation and mass balance response of tributary glaciers following the loss of the larsen a and b ice shelves antarctic peninsula in 1995 and 2002 respectively our study uses modis imagery to track ice extent and aster and spot5 digital elevation models dems plus atm and icesat laser altimetry to track elevation changes spanning the period 2001 09 the measured larsen b tributary glaciers hektoria green evans punchbowl jorum and crane lost up to 160 m in elevation during 2001 06 and thinning continued into 2009 elevation changes were small for the more southerly flask and leppard glaciers which are still constrained by a larsen b ice shelf remnant in the northern embayment continued thinning of 3 m a 1 on drygalski glacier 14 years after the larsen a ice shelf disintegrated suggests that mass losses for the exposed larsen b tributaries will continue for years into the future grounded ice volume losses exceed 13 km 3 for crane glacier and 30 km 3 for the hektoria green evans glaciers the combined mean loss rate for 2001 06 is at least 11 2 gt a 1 our values differ significantly from published mass budget based estimates for these embayments but are a reasonable fraction of grace derived rates for the region 40 gt a 1

accelerated ice discharge from the antarctic peninsula following the collapse of larsen b ice shelf acceleration exceeds 27 km 3 per year and ice is thinning at rates of tens of meters per year we attribute this abrupt evolution of the glaciers to the removal of the buttressing ice shelf the magnitude of the glacier changes illustrates the importance of ice shelves on ice sheet mass balance and contribution to sea level change index terms 1827 hydrology glaciology 1863 1863 hydrology snow and ice 1827 3349 meteorology and atmospheric dynamics polar meteorology 6924 radio science interferometry 9310 information related to geographic region antarctica citation rignot e g casassa p gogineni w krabill a rivera and r thomas 2004 accelerated ice discharge from the antarctic peninsula following the collapse of larsen b ice shelf geophys res lett 31 l18401 doi 10 1029 2004gl020697

planetary wave propagation off california and its effect on zooplankton abstract lagged correlation of dynamic height from the gappy california cooperative oceanic fisheries investigation calcofi with monthly san diego sea level for the period 1949 2001 shows that the dynamic height propagates westward at 4 10 cm s 1 about double the speed of the large scale low frequency rossby wave 2 2 cm s 1 ocean topography experiment topex poseidon jason 1 s along track sea level height estimates since january 1993 filtered interannually propagate westward at 4 3 cm s 1 verifying that observed westward propagation is about double that expected including the effect of the mean california current on the rossby wave propagation does not explain the discrepancy but rather slightly increases it if variations in the ocean depth in the calcofi region are also taken into account the westward propagation is still only about one half that observed standard theory therefore does not explain the observations because of the westward propagation interannual variations in alongshore ge

grounding line variability and subglacial lake drainage on pine island glacier antarctica we produced a 6 year time series of differential tidal displacement for pine island ice shelf antarctica using speckle tracking methods applied to fine resolution terrasar x data these results reveal that the main grounding line has maintained a relatively steady position over the last 6 years following the speedup that terminated in 2009 in the middle of the shelf there are grounded spots that migrate downstream over the 6 year record examination of high resolution digital elevation models reveals that these grounded spots form where deep keels thickness anomalies advect over an approximately flow parallel bathymetric high maintaining intermittent contact with the bed these data sets also reveal several subsidence and uplift events associated with subglacial lake drainages in the fast flowing region above the grounding line although these drainages approximately double the rate of subglacial water flow over periods of a few weeks they have no discernible effect on horizontal flow speed

sensitivity of greenland ice sheet projections to model formulations physically based projections of the greenland ice sheet contribution to future sea level change are subject to uncertainties of the atmospheric and oceanic climatic forcing and to the formulations within the ice flow model itself here a higher order three dimensional thermomechanical ice flow model is used initialized to the present day geometry the forcing comes from a high resolution regional climate model and from a flowline model applied to four individual marine terminated glaciers and results are subsequently extended to the entire ice sheet the experiments span the next 200 years and consider climate scenario sres a1b the surface mass balance smb scheme is taken either from a regional climate model or from a positive degree day pdd model using temperature and precipitation anomalies from the underlying climate models our model results show that outlet glacier dynamics only account for 6 18 of the sea level contribution after 200 years confirming earlier findings that stress the dominant effect of smb changes furthermore interaction between smb and ice discharge limits the importance of outlet glacier dynamics with increasing atmospheric forcing forcing from the regional climate model produces a 14 31 higher sea level contribution compared to a pdd model run with the same parameters as for ipcc ar4

antarctic grounding line mapping from differential satellite radar interferometry 1 the delineation of an ice sheet grounding line i e the transition boundary where ice detaches from the bed and becomes afloat in the ocean is critical to ice sheet mass budget calculations numerical modeling of ice sheet dynamics ice ocean interactions oceanic tides and subglacial environments here we present 15 years of comprehensive high resolution mapping of grounding lines in antarctica using differential satellite synthetic aperture radar interferometry dinsar data from the earth remote sensing satellites 1 2 ers 1 2 radarsat 1 and 2 and the advanced land observing system alos palsar for years 1994 to 2009 dinsar directly measures the vertical motion of floating ice shelves in response to tidal oceanic forcing with millimeter precision at a sample spacing better than 50 m simultaneously over areas several 100 km wide in contrast with earlier methods that detect abrupt changes in surface slope in satellite visible imagery or altimetry data on stagnant and slow moving areas we find that breaks in surface slope are reliable indicators of grounding lines but on most fast moving glaciers and ice streams our dinsar results reveal that prior mappings have positioning errors ranging from a few km to over 100 km a better agreement is found with icesat s data also based on measurements of vertical motion but with a detection noise one order of magnitude larger than with dinsar overall the dinsar mapping of antarctic grounding lines completely redefines the coastline of antarctica

glacier motion estimation using sar offset tracking procedures two image to image patch offset techniques for estimating feature motion between satellite synthetic aperture radar sar images are discussed intensity tracking based on patch intensity cross correlation optimization and coherence tracking based on patch coherence optimization are used to estimate the movement of glacier surfaces between two sar images in both slant range and azimuth direction the accuracy and application range of the two methods are examined in the case of the surge of monacobreen in northern svalbard between 1992 and 1996 offset tracking procedures of sar images are an alternative to differential sar interferometry for the estimation of glacier motion when differential sar interferometry is limited by loss of coherence i e in the case of rapid and incoherent flow and of large acquisition time intervals between the two sar images in addition an offset tracking procedure in the azimuth direction may be combined with differential sar interferometry in the slant range direction in order to retrieve a two dimensional displacement map when sar data of only one orbit configuration are available

evaluating the use of high frequency radar coastal currents to correct satellite altimetry 1 coastal altimeter waveforms may differ from the ones in the open ocean either from rapid changes in the sea state or the presence of land within the satellite altimeter footprint the optimal retracking method for an individual track may turn out to be a combination of several retrackers and may depend on the sea state the coastal high frequency radar hfr ocean surface currents hourly interpolated with a resolution up to 2 km and an offshore range up to 150 km are evaluated to validate the altimeter sea surface height ssh measurements a method to derive hfr ssh mapped with a varying spatial scale optimal interpolation from the hfr velocities has been implemented evaluated mainly in the regions farther than 25 km off the u s west coast the hfr ssh shows good agreement with jason 1 2 altimetry products over the years 2008 and 2009 three jason 2 pistach retrackers and one generic open ocean retracker have been analyzed using the traditional 1 hz sampling rate nearshore an experimental reprocessing of the 20 hz range measurements is also tested to check for a gain in along track spatial resolution referencing to the hfr ssh indicate the need to have several retrackers available even over the continental shelf with ice3 fitting better during bloom events and mle 4 or red3 for high sea states these studies demonstrate the value of hfr as a potential tool to correct coastal altimeter ssh refine their spatial resolution and provide some insight into the altimeter behavior as a function of ocean conditions

ocean warming and sea level rise along the southwest u s coast hydrographic time series data recorded during the past 42 years in the upper 500 meters off the coast of southern california indicate that temperatures have increased by 0 8 c uniformly in the upper 100 meters and that temperatures have risen significantly to depths of about 300 meters the effect of warming the surface layer of the ocean and there by expanding the water column has been to raise sea level by 0 9 0 2 millimeter per year tide gauge records along the coast are coherent with steric height and show upward trends in sea level that vary from about 1 to 3 millimeters per year

a sar record of early 21st century change in greenland glaciers in greenland are changing rapidly to better understand these changes we have produced a series of seven synthetic aperture radar sar backscatter mosaics for seven winters during the period from 2000 to 2013 six of the mosaics were created using radarsat fine beam data and the seventh used alos palsar fine beam single polarization data the radarsat mosaics are radiometrically calibrated and capture changes in the backscatter coefficient related to melt and other events particularly the strong melting in the summer of 2012 comparison of features in the ascending orbit alos mosaic and the descending orbit radarsat mosaics indicate that in areas of smooth to moderate topography their locations are consistent to within a few 10s of meters the locations of features identifiable in the radarat mosaics which were collected with the same imaging parameters generally agree to within better than the 20 m posting of the data with such geometric accuracy these data establish a record of change in greenland for the early part of the 21st century thus providing a baseline that can be compared with new radar and optical data sets

seasonal dynamics of the surface circulation in the southern california current system abstract the seasonal dynamics of the southern california current scc is investigated using a primitive equation ocean model with real coastlines and topography the model is tested with different wind forcing and the resulting flow fields are compared to the mean and seasonal circulation inferred from long term in situ observations california cooperative oceanic fisheries investigation calcofi the model integration forced with the output winds of a regional atmospheric model rsm best captures the statistics of the observed circulation with a 0 9 correlation coefficient for the streamlines and 0 5 for the velocity fields the model integrations reveal a pronounced linear response of the flow field to changes in winds on the shelf region a dynamical feature inferred from calcofi hydrography also suggested in topex ers maps is an annually recurrent westward propagation of ssh anomalies originated in the southern california bight scb during the upwelling season the rsm integration is the only one to capture the correct timing and spatial evolution of this process we therefore use this model integration for guidance in constructing a dynamical framework to interpret the observed circulation and its variability during the upwelling season in spring there is an upward tilt of the isopycnals along the coast directly forced by the winds in the bight as the spring transitions to the summer the upwelling winds relax in the bight but are still strong in the region offshore approximately in correspondence of the continental slope positive wind stress curl condition anomalous denser waters in the location of the southern california eddy are maintained and reinforced by the combined interaction of the coastal islands geometry and the wind stress curl through ekman dynamics the adjustment process to the denser water initiates a westward propagation of ocean density anomaly through rossby waves and reinforces the cyclonic gyre like circulation of the sce increasing positive vorticity surface poleward flow maintained by the positive wind stress curl is also reinforced in proximity of point conception as a consequence of the adjustment during the summer the cyclonic gyre becomes increasingly unstable as the core of the ocean anomalies crosses the continental slope instability processes within the cyclonic region characterized by a sharp increase in eke shed eddies that leave the region either drifting to the west or interacting with existing eddies in the region offshore the eke reaches a seasonal maximum at the end the summer in the cyclonic region and in late fall further offshore where the eddies are fully developed the shedding of eddies cannot be directly seen in the calcofi observations because of the sampling aliasing for this point we rely on the strong suggestion of the model which we assume is able to capture the leading order dynamics additional integrations with a linearized version of the model are also presented to reinforce our interpretation of the westward propagation of the isopycnal anomalous displacement associated with rossby wave dynamics

pattern of retreat and disintegration of larsen b ice shelf antarctic peninsula the retreat of the larsen b ice shelf antarctic peninsula and the collapse of its northern section are analyzed using satellite images acquired between january 1995 and may 2003 over 1 week during march 2002 after a period of steady retreat since 1995 2300 km 2 of the ice shelf broke up into many small icebergs this rapid collapse occurred at the end of an exceptionally warm summer and after a multi year period of decreasing surface net mass balance ice thinning flow acceleration and widening of rifts the ice shelf area decreased from 11 512 km 2 in january 1995 to 3463 km 2 in march 2002 and 2667 km 2 in april 2003 ers synthetic aperture radar sar images were used to identify ice shelf zones with different surface morphology which generated icebergs of different sizes and shapes the pattern of retreat and break up similar to that of larsen a in 1995 suggests that fracturing enhanced by abundant surface melt played a key role in addition the recent changes of grounded and residual floating ice north of larsen b are analyzed by means of envisat advanced synthetic aperture radar asar images up to summer 2003 showing significant loss of grounded ice upstream of those ice shelf sections which disintegrated in 1995 and 2002

a low level explanation for the recent large warming trend over the western antarctic peninsula involving blocked winds and changes in zonal circulation 1 we demonstrate a mechanism whereby the impact of stronger circumpolar westerly winds on the mountains of the antarctic peninsula contributes significantly to the enhanced warming trend observed over its western side in the last 50 years numerical and laboratory meteorological modelling demonstrate how when westerly winds impinge on this side warm air below the height 1 5 2 0 km of the peninsula is advected in a southerly direction the strength of the annual mean westerly winds has increased by about 15 20 since the 1960s while the modelling results indicate that contemporaneously the air advected to its western side originates from an increasingly northerly and warmer location this gives rise to increased northerlies and a greater transport of warm air into this region consequently there is a reduction in the sea ice extent further amplifying the local warming this low level orographic mechanism for the local climate trend is supported by observational evidence

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

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

mass loss of larsen b tributary glaciers antarctic peninsula unabated since 2002 ice mass loss continues at a high rate among the large glacier tributaries of the larsen b ice shelf following its disintegration in 2002 we evaluate recent mass loss by mapping elevation changes between 2006 and 2010 11 using differencing of digital elevation models dems the measurement accuracy of these elevation changes is confirmed by a null test subtracting dems acquired within a few weeks the overall 2006 2010 11 mass loss rate 9 0 2 1 gt a 1 is similar to the 2001 02 2006 rate 8 8 1 6 gt a 1 derived using dem differencing and laser altimetry this unchanged overall loss masks a varying pattern of thinning and ice loss for individual glacier basins on crane glacier the thinning pulse initially greatest near the calving front is now broadening and migrating upstream the largest losses are now observed for the hektoria green glacier basin having increased by 33 since 2006 our method has enabled us to resolve large residual uncertainties in the larsen b sector and confirm its state of ongoing rapid mass loss

interannual changes of the floating ice shelf of petermann gletscher north greenland from 2000 to 2012 petermann gletscher northwest greenland drains 4 of the greenland ice sheet into nares strait its floating ice shelf retreated from 81 to 48 km in length during two large calving events in 2010 and 2012 we document changes in the three dimensional ice shelf structure from 2000 to 2012 using repeated tracks of airborne laser altimetry and ice radio echo sounding icesat laser altimetry and modis visible imagery the recent ice shelf velocity measured by tracking surface features between flights in 2010 and 2011 is 1 25 km a 1 15 30 faster than estimates made before 2010 the steady state along flow ice divergence represents 6 3 gt a 1 mass loss through basal melting 5 gt a 1 and surface melting and sublimation 1 0 gt a 1 airborne laser altimeter data reveal thinning both along a thin central channel and on the thicker ambient ice shelf from 2007 to 2010 the ice shelf thinned by 5 m a 1 which represents a non steady mass loss of 4 1 gt a 1 we suggest that thinning in the basal channels structurally weakened the ice shelf and may have played a role in the recent calving events

changes in ice front position on greenland s outlet glaciers from 1992 to 2007 1 previous studies in greenland show that retreat of tidewater glaciers may be linked to recent increases in ice loss raising greenland s contribution to sea level rise we examined ice front changes of 203 tidewater glaciers land terminating glaciers and glaciers terminating with ice shelves to understand greenland glacier behavior over three periods 1992 2000 2000 2006 and 2006 2007 we observed synchronous ice sheet wide increases in tidewater retreat during 2000 2006 relative to 1992 2000 coinciding with a 1 1 c increase in mean summer temperature at coastal weather stations rates of retreat for the southeast and east slowed during 2006 2007 when temperatures were slightly cooler than the 2000 2006 average our work suggests that regional greenland tidewater retreat responds strongly to climate change with higher temperatures corresponding to increasing retreat and helps confirm a link between ice thickness velocity and ice front position

rapid retreat and acceleration of helheim glacier east greenland 1 a significant amount of the measured coastal thinning of the greenland ice sheet may be due to recent acceleration of outlet glaciers using remote sensing we measured two major periods of speedup on helheim glacier between 2000 and 2005 that increased peak speeds from approximately 8 to 11 km yr these speedups coincided with rapid retreats of the calving front totaling over 7 5 km the glacier also thinned by over 40 m from 2001 to 2003 retreat of the ice front appears to decrease resistance to flow and concentrates the gravitational driving force over a smaller area farther up glacier acceleration may be a delayed response to surface draw down and steepening of the glacier s main trunk if the 2005 speedup also produces strong thinning then much of the glacier s main trunk may un ground leading to further retreat citation howat i m i joughin s tulaczyk and s gogineni 2005 rapid retreat and acceleration of helheim glacier east greenland geophys res lett 32 l22502 doi 10 1029 2005gl024737

observations of near inertial waves in acoustic doppler current profiler measurements made during the mixed layer dynamics experiment measurements of upper ocean shear made during the mixed layer dynamics experiment mildex provide evidence of large horizontal scale motion at near inertial frequency the measurements consist of shipboard acoustic doppler current profiles four large scale spatial surveys of 2 4 days duration were made by the r v wecoma as a set of boxes approximately 60 km per side around a drifting current meter buoy velocity time series from the drifting buoy and from sonar measurements made from flip also indicated the presence of motions at near inertial frequency horizontal length and time scales of the motion are estimated from the phase of the shear vector measured during the spatial surveys estimates of the length scale of the waves range from 500 to 1000 km and the frequency is approximately 1 1f the behavior of the phase is found to be consistent with a model of narrow band inertial waves with vertical structure such that there is a zero crossing in velocity at the base of the mixed layer 40 60 m

maceral distributions in illinois coals and their paleoenvironmental implications abstract for purposes of assessing the maceral distribution of illinois u s a coals analyses were assembled for 326 face channel and drill core samples from 24 coal members of the pennsylvanian system the inertinite content of coals from the missourian and virgilian series averages 16 1 mineral free compared to 9 4 for older coals from the desmoinesian and older series this indicates there was generally a higher state of oxidation in the peat that formed the younger coals this state probably resulted from greater exposure of these peats to weathering as the climate became drier and the water table lower than was the case for the older coals although oxidation during allochthonous deposition of inertinite components is a genetic factor that needs further study to confirm the importance of the climate regional variation of the vitrinite inertinite ratio v i on a mineral and micrinite free basis was observed in the springfield no 5 and herrin no 6 coal members to be related to the geographical position of paleochannel river deposits known to have been contemporaneous with the peats that formed these two coal strata the v i ratio is highest generally 12 27 in samples from areas adjacent to the channels and lower 5 11 some 10 20 km away we interpret the v i ratio to be an inverse index of the degree of oxidation to which the original peat was exposed high v i ratio coal located near the channels probably formed under more anoxic conditions than did the lower v i ratio coal some distance away from the channels the low v i ratio coal probably formed in areas of the peat swamp where the watertable was generally lower than the channel areas

recent ice surface elevation changes of fleming glacier in response to the removal of the wordie ice shelf antarctic peninsula regional climate warming has caused several ice shelves on the antarctic peninsula to retreat and ultimately collapse during recent decades glaciers flowing into these retreating ice shelves have responded with accelerating ice flow and thinning the wordie ice shelf on the west coast of the antarctic peninsula was reported to have undergone a major areal reduction before 1989 since then this ice shelf has continued to retreat and now very little floating ice remains little information is currently available regarding the dynamic response of the glaciers feeding the wordie ice shelf but we describe a chilean international polar year project initiated in 2007 targeted at studying the glacier dynamics in this area and their relationship to local meteorological conditions various data were collected during field campaigns to fleming glacier in the austral summers of 2007 08 and 2008 09 in situ measurements of ice flow velocity first made in 1974 were repeated and these confirm satellite based assessments that velocity on the glacier has increased by 40 50 since 1974 airborne lidar data collected in december 2008 can be compared with similar data collected in 2004 in collaboration with nasa and the chilean navy this comparison indicates continued thinning of the glacier with increasing rates of thinning downstream with a mean of 4 1 0 2 m a 1 at the grounding line of the glacier these comparisons give little indication that the glacier is achieving a new equilibrium

the diversification of paleozoic fire systems and fluctuations in atmospheric oxygen concentration by comparing silurian through end permian 250 million years myr charcoal abundance with contemporaneous macroecological changes in vegetation and climate we aim to demonstrate that long term variations in fire occurrence and fire system diversification are related to fluctuations in late paleozoic atmospheric oxygen concentration charcoal a proxy for fire occurs in the fossil record from the late silurian 420 myr to the present its presence at any interval in the fossil record is already taken to constrain atmospheric oxygen within the range of 13 to 35 the fire window herein we observe that as predicted atmospheric oxygen levels rise from 13 in the late devonian to 30 in the late permian so too fires progressively occur in an increasing diversity of ecosystems sequentially data of note include the occurrence of charcoal in the late silurian early devonian indicating the burning of a diminutive dominantly rhyniophytoid vegetation an apparent paucity of charcoal in the middle to late devonian that coincides with a predicted atmospheric oxygen low and the subsequent diversification of fire systems throughout the remainder of the late paleozoic first fires become widespread during the early mississippian they then become commonplace in mire systems in the middle mississippian in the pennsylvanian they are first recorded in upland settings and finally based on coal petrology become extremely important in many permian mire settings these trends conform well to changes in atmospheric oxygen concentration as predicted by modeling and indicate oxygen levels are a significant control on long term fire occurrence

mesoscale eddies in the southern gulf of california during summer characteristics and interaction with the wind stress 1 the hydrodynamic characteristics of mesoscale eddies of the southern gulf of california are described from observations made in august 2004 vertical profiles to 1000 m were made with a conductivity temperature depth ctd probe with dissolved oxygen and fluorescence sensors and a lowered acoustic doppler profiler the four sampled eddies were aligned along the gulf axis and had alternating sense of rotation the okubo weiss parameter was used to calculate the eddy core radii and it also revealed that the current field of almost all the sampled area was eddy dominated the mean radii of the eddy cores varied between 32 and 36 km maximum surface velocities were 0 4 0 5 m s the anticyclonic eddies were 500 700 m deep while the cyclones were 450 500 m deep the depression of the isolines associated with the anticyclonic eddies was 100 m at depths between 200 and 400 m however the thermocline pycnocline which spanned from 20 to 75 m was domed by 10 m the cyclonic eddies lifted the isolines by 70 m at depths above 500 m but the isolines were flat above 60 m this suggests that different dynamics operate in the layer above the strong and shallow pycnocline in particular the wind stress curl can affect circulation and pycnocline topography and therefore the patterns that appear in chlorophyll satellite images in our case the eddies were detectable in those images because of the chlorophyll enhanced streamers along their edges and for anticyclones probably because the chlorophyll maximum found at 40 50 m depth was domed following the pycnocline

lead isotope ratios in spanish coals of different characteristics and origin lead isotope ratios in coals of different rank from several spanish basins were estimated and related with their characteristics the isotope 206pb 207pb ratio values of the coals studied range between 1 13 and 1 21 with the exception of some coal samples from the cretaceous which are more radiogenic coals were classified into groups according to their lead isotope ratios these in turn were related to the isotope ratios of the minerals galena pyrite chalcopyrite and carbonates some of the low rank coals in which lead might be expected to be associated with the organic matter were not found to be related with the isotope ratios of minerals the isotope ratios of the individual densimetric fractions separated from a bituminous coal are different to those of the raw coal the differences between these isotope ratios may not only be due to the diverse origin of lead in different coals but also with the possible presence of several lead species incorporated from various sources in a particular coal the results of this work represent an important contribution to the lead isotope ratio database essential for the accurate interpretation of data regarding pollution sources

observations of the vertical and temporal evolution of a natal pulse along the eastern agulhas bank this study re investigates the work of lutjeharms et al 2001 2003 who documented the properties of a natal pulse using isopycnal lagrangian floats we combined lagrangian analyses and eulerian maps derived from objective analysis to better describe the evolution of a natal pulse along three density surfaces referred to as the surface satellite observed shallow isopycnal 1026 8 kg m 3 and deep isopycnal 1027 2 kg m 3 layer our observations show that this natal pulse extended to a depth of 1000m and was associated with cyclonic relative vorticity values of about 6 5 to 8 5x10 5 s 1 in the surface and shallow layer and 4x10 5 s 1 in the deep layer this natal pulse contributed to cross shelf exchange through the offshore advection of eastern agulhas bank water near the surface onshore advection of south indian central water and or indian equatorial water in the shallow layer and antarctic intermediate water in the deep layer sea surface temperature maps showed that the downstream progression of the natal pulse along the 3000m isobath was related to a readjustment of its rotation axis this readjustment advected eastern agulhas bank water into the natal pulse eddy and triggered a sst cooling of about 3 c in the cyclonic area the importance of a warm recirculating agulhas plume originating from the natal pulse was highlighted this warm water plume extended to a depth of 700m and was associated with onshore velocities exceeding those experienced within the natal pulse eddy by a factor of two our observations indicate that the june july 1998 natal pulse and its associated plumes enhanced cross shelf exchanges this article is protected by copyright all rights reserved

comparison of model and observational ocean circulation climatologies for the new zealand region 1 primitive equation three dimensional regional models driven by global models can be used to generate climatologies of the ocean circulation with 1 12 resolution these model climatologies begin to resolve the coastal circulation and it is appropriate to ask whether they are adequate to replace observational climatologies we compare circulation climatologies derived from a z coordinate 36 vertical layer model run with three different diffusivities with an observational climatology csiro atlas of regional seas cars and with surface velocities derived from lagrangian drifters deployed under the global drifter program gdp all the climatologies capture the major features in the mean circulation south of the chatham rise and east of new zealand the model climatologies agree better with gdp than does cars north of the chatham rise the models overestimate the strength of the east cape eddy wave number spectra from the models suggest that instability processes which are important in the mean are captured with diffusion less than 25 m2 s 1 the model with lowest diffusion may be providing the best estimate of the mean circulation but at the expense of numerical instability

mass changes of outlet glaciers along the nordensjkold coast northern antarctic peninsula based on tandem x satellite measurements we analyzed volume change and mass balance of outlet glaciers of the northern antarctic peninsula over the period 2011 to 2013 using topographic data of high vertical accuracy and great spatial detail acquired by bistatic radar interferometry of the tandem x terrasar x satellite formation the study area includes glaciers draining into the larsen a larsen inlet and prince gustav channel embayments after collapse of buttressing ice shelves in 1995 the glaciers became tidewater calving glaciers and accelerated resulting in increased ice export downwasting of most glaciers is going on but at reduced rates compared to previous years in accordance with deceleration of ice flow the rate of mass depletion is 4 2 0 4 gt a 1 with the largest contribution by drygalski glacier amounting to 2 2 0 2 gt a 1 on the technological side the investigations demonstrate the capability of satellite borne single pass radar interferometry as a new tool for accurate and detailed monitoring of glacier volume change

coal facies interpretations based on lithotype and maceral variations in lower cretaceous gates formation coals of western canada abstract maceral analyses of lithotype samples from lower cretaceous coal seams have been used to define compositional characteristics of the various lithotypes and to assess coal facies changes within the seams based on maceral and lithotype variations the mean petrographic compositions of the lithotypes show a general trend to decreasing vitrinite increasing inertinite and increasing mineral matter contents from the bright to dull varieties the bright lithotypes are considered to have been formed in wet and densely forested swamps whereas the banded lithotypes were formed under somewhat drier conditions within the dull lithotype two distinct types were recognized based on differences in petrographic composition and the occurrence or absence of facies diagnostic macerals it is suggested that these differences are due to formation in distinct mire facies under the influence of open moor or raised mire conditions the lithotype variations within the seams together with the data on their petrographic composition were used to define facies changes which occurred during accumulation of the peats three types of seam development are recognized a seams containing a high proportion of clastic beds indicative of frequent floodings of the swamps these seams are characterized by the dominance of oscillatory sequences of bright lithotypes and dulling upward sequences below clastic beds the brighter lithotypes were formed in forested swamps and fens whereas for the duller sequences influences of open moor conditions are indicated b seams containing only minor thin clastic beds indicating relative stability of water levels during formation of the peat these seams are characterized by the predominance of duller lithotypes with common repetitions of dulling upward sequences the dulling up sequences indicate transitions from wet and very wet forest swamps to drier conditions with lower tree density c transitional seams characterized by a few clastic beds these seams formed under intermediate conditions of stability in respect to flooding events the seams are characterized by the predominance of banded lithotypes dull lithotypes near partings and brightening and dulling up sequences the brightening up sequences represent transitions from dry forest swamp to wet and very wet forest swamps while a reverse trend is indicated for the dulling up sequences the overall petrographic characteristics of full seam sections indicate that the seams are in general relatively low in vitrinite and relatively rich in inertinite macerals liptinite content is negligible and mineral matter contents are low based on petrographic indices obtained from facies diagnostic macerals an accumulation of the ancient peats under prevailing wet to very wet forest swamps is suggested vicinity to more open moor conditions is indicated for one seam by the higher input of dispersed macerals