surface and bed topography of trapridge glacier yukon territory canada digital elevation models and derived hydraulic geometry measurements of ice thickness and surface elevation are prerequisite to many glaci ological investigations a variety of techniques has been develo ped for inter pret ation of these data including means of constructing regularly gridded digital eleva tion models dem s for use in numcrical studies here we present a simple yet stati sti cally sound method for processing ice pe netr ating radar data and descr ibe a tech nique for interpol ating these data onto a regular grid dems generatcd fort rapridge glacier yukon territory canada are used to derive geometric quantities lhal give pre liminary insights into the underlying basin scale hydrol ogical syste m this simple geo metric analysis suggests that at low water press ures a dendrilic drainage netw ork exists that evolves into a uniaxial morphology as water pressure approaches notation these pre dictions are compared to hydraulic connection probabilities based on bore hole drilling

dynamical response of equatorial indian ocean to intraseasonal winds zonal flow nonlinear and linear 4 layer ocean models are used to explore the dynamics of intraseasonal 20 90 day periods zonal flow in the equatorial indian ocean the model simulations suggest that the observed 40 60 day zonal surface current is forced primarily by wind associated with the madden julian oscillation mjo which peaks at 40 60 days the strongest spectral peak of zonal flow however occurs at 90 day period in the model and a corresponding 90 day peak appears in the observed sea level data the 90 day current results from the preferential excitation of kelvin and rossby waves by the lower frequency component of intraseasonal wind and from the enhancement by rossby waves reflected from the eastern ocean boundary

structure and composition of organic reefs and carbonate mud mounds concepts and categories defined here as essentially in place calcareous deposits created by sessile organisms organic reefs are diverse and complex structures with a long geological history their classification has been the subject of fierce debate often characterized by reliance on subjective features such as wave resistance and qualitative attempts to discriminate between first and second class reefs in contrast emphasis is here placed on the objective characteristic of the type of sedimentary support which largely determines the sedimentary composition of the deposit constructional and depositional processes result in three principal sedimentary components matrix m essentially in place skeletons s and cavity cement c whose proportions can be represented on msc triangular plots separately or together these components also provide the structural support for the reef on these compositional and structural bases three main categories of organic reef are recognized 1 matrix supported reefs agglutinated microbial reefs cluster reefs segment reefs 2 skeleton supported reefs frame reefs 3 cement supported reefs cement reefs agglutinated microbial reefs possess laminated clotted or aphanitic fabrics created by microbial trapping of particulate sediment in place skeletons and large primary cavities are rare early cementation may provide added support topographic relief is limited by the need for currents to provide sediment to accreting surfaces cluster reefs skeletal reefs in which essentially in place skeletons are adjacent but not in contact resulting in matrix support characterized by relatively high matrix skeleton ratios and low volumes of extra skeletal early cement sediment trapping is an important corollary of skeletal growth and cluster reef organisms are tolerant of loose sediment absence of framework limits the topographic relief that cluster reefs can attain relative to spatial extent and may permit bedding to develop within the reef close cluster reefs have skeletons up to 1 unit distance apart spaced cluster reefs have skeletons more than 1 and up to 2 unit distances apart with increasing separation of skeletons they grade to level bottom communities segment reefs matrix supported reefs in which skeletons are adjacent and may be in contact but are mostly disarticulated and mainly parauthochtonous matrix abundance is high and early cement relatively low moderate relief can develop in response to intense on reef sediment production frame reefs skeletal reefs in which essentially in place skeletons including calcified microbes are in contact characterized by relatively high skeleton matrix ratio skeletal support enables them to raise themselves above the substrate independently of cementation and particulate sedimentation simultaneously by creating partly open shelter cavities skeletal support may facilitate early cementation both relief and early lithification promote marginal talus formation skeletal shape and orientation distinguish conical stick like dendritic domical and laminar frames each of these may be open or filled open frame reefs

seaglider observations of equatorial indian ocean rossby waves associated with the madden julian oscillation during the cindy dynamo field campaign of september 2011 january 2012 a seaglider was deployed at 80 e and completed 10 north south sections between 3 and 4 s measuring temperature salinity dissolved oxygen concentration and chlorophyll fluorescence these high resolution subsurface observations provide insight into equatorial ocean rossby wave activity forced by three madden julian oscillation mjo events during this time period these rossby waves generate variability in temperature o 1 c salinity o 0 2 g kg 1 density o 0 2 kg m 3 and oxygen concentration o 10 mol kg 1 associated with 10 m vertical displacements of the thermocline the variability extends down to 1000 m the greatest depth of the seaglider observations highlighting the importance of surface forcing for the deep equatorial ocean the temperature variability observed by the seaglider is greater than that simulated in the ecco jpl reanalysis especially at depth there is also marked variability in chlorophyll fluorescence at the surface and at the depth of the chlorophyll maximum upwelling from rossby waves and local wind stress curl leads to an enhanced shoaling of the chlorophyll maximum by 10 25 m in response to the increased availability of nutrients and light this influence of the mjo on primary production via equatorial ocean rossby waves has not previously been recognized

radio echo sounding studies of englacial water movement in variegated glacier alaska une crue glaciaire du variegated a ete enregistree a l aide d un emetteur mono impulsion de 3mhz les discontinuites intraglaciaires ont ete observees dans le domaine des 12 a 30 mhz les changements dans la forme des echos sont interpretes en terme de redistribution de l eau dans les canaux glaciaires et les cavites reliees au lit a quelque distance a l aval

origins and dynamics of the 90 day and 30 60 day variations in the equatorial indian ocean abstract sea level observations in the equatorial indian ocean show a dominant spectral peak at 90 days and secondary peaks at 30 60 days over an intraseasonal period 20 90 days a detailed investigation of the origins and dynamics of these variations is carried out using an ocean general circulation model namely the hybrid coordinate ocean model hycom two parallel experiments are performed in the tropical indian ocean basin for the period 1988 2001 one is forced by ncep 3 day mean forcing fields together with the climate prediction center cpc merged analysis of precipitation cmap pentad precipitation and the other is forced by monthly mean fields to help to understand the role played by the wind driven equatorial wave dynamics a linear continuously stratified ocean model is also used both the observed and modeled 90 day sea level anomaly fields and hycom surface current clearly show equatorial kelvin and first meridional mode rossby wave structures that are forced by the 90 day winds the

characterizing englacial drainage in the ablation zone of the greenland ice sheet rapid local drainage of surface meltwater to the base of the greenland ice sheet is thought to result in surface velocity variations as far inland as the equilibrium zone zwally and others 2002 ice penetrating radar surveys throughout this region allow us to characterize englacial drainage features that appear as vertically stacked diffraction hyperbolae in common offset profiles these data are used with a radar simulation model which allows for variations in geometry penetration depth and infill material to understand the characteristics of these hyperbolae and the likelihood that they are produced by moulins we find only a moderate correlation between the locations of these possible moulins and supraglacial lakes indicating that many lakes drain over the surface of the ice sheet or do not contain sufficient water to reach the bed through moulin formation we find a strong correlation between moulin location in the ablation region and elevated along flow tension due to flow over rough bedrock which generates surface crevassing and provides an entry point for meltwater although theory suggests that moulins may form anywhere on the ice sheet given sufficient meltwater input our data suggest that they are far more common in the ablation zone than near or inland from the equilibrium line

intraseasonal to semiannual variability of sea surface height in the astern equatorial indian ocean and southern bay of bengal intraseasonal to semiannual variability of sea surface height ssh in the eastern equatorial indian ocean eeio and southern bay of bengal bob is investigated using altimetric data and solutions to 1 layer first baroclinic mode and linear continuously stratified lcs multi baroclinic mode models the amplitude and dominant period of ssh variability differ regionally large amplitude variability is found along the west coast of sumatra in a zonal band across the bob centered along 5 n east of sri lanka and in the northwestern bob respectively along the sumatran west coast ssh variability peaks at 30 60 days 90 days and 180 days along 5 n and east of sri lanka the 30 60 day variability is dominant sensitivity experiments using a nonlinear version of the 1 layer model forced by realistic winds reproduce the observed patterns of intraseasonal variability in the southern bob at 30 60 days the solutions show that eddies nonlinear rossby waves propagating from the east rather than local wind forcing account for most of the variance east of sri lanka furthermore they demonstrate that the variance is significantly enhanced by the nonlinear transfer of 90 120 day energy into the intraseasonal band of 30 60 days the lcs solutions show that the first two baroclinic modes explain most of the ssh variance at 90 180 days the second baroclinic mode dominates the ssh variance at 180 days a consequence of basin resonance and strong wind forcing

interpretation of basal ice conditions from radio echo soundings in the eastern heimefrontfjella and the southern vestfjella mountain ranges east antarctica interpretation of basal ice conditions from radio echo soundings in the eastern heimefrontfjella and the southern vestfjella mountain ranges east antarctica

ocean temperature and salinity components of the madden julian oscillation observed by argo floats new diagnostics of the madden julian oscillation mjo cycle in ocean temperature and for the first time salinity are presented the mjo composites are based on 4 years of gridded argo float data from 2003 to 2006 and extend from the surface to 1 400 m depth in the tropical indian and pacific oceans the mjo surface salinity anomalies are consistent with precipitation minus evaporation fluxes in the indian ocean and with anomalous zonal advection in the pacific the argo sea surface temperature and thermocline depth anomalies are consistent with previous studies using other data sets the near surface density changes due to salinity are comparable to and partially offset those due to temperature emphasising the importance of including salinity as well as temperature changes in mixed layer modelling of tropical intraseasonal processes the mjo forced equatorial kelvin wave that propagates along the thermocline in the pacific extends down into the deep ocean to at least 1 400 m coherent statistically significant mjo temperature and salinity anomalies are also present in the deep indian ocean

in search of ice stream sticky spots the form drag of large bedrock bumps sticking into the base of an ice stream can produce effective sticky spots supporting large basal shear stress bedrock regions surrounded by lubricating till at the same topographic level can cause sticky spots but tend to collect lubricating water and thus are unlikely to support a shear stress of more than a few tenths of a bar unless they contain abundant large bumps raised regions on the ice air surface also can cause moderate increases in the shear stress supported on the bed beneath surveys of large scale bedrock roughness strain grids across the margins of ice surface highs and possibly water pressure measurements in regions of thin or zero till would help identify and characterize sticky spots

ocean rossby waves as a triggering mechanism for primary madden julian events the madden julian oscillation mjo is sporadic with episodes of cyclical activity interspersed with inactive periods however it remains unclear what may trigger a madden julian mj event which is not immediately preceded by any mjo activity a primary mj event a combination of case studies and composite analysis is used to examine the extent to which the triggering of primary mj events might occur in response to ocean dynamics the case studies show that such events can be triggered by the arrival of a downwelling oceanic equatorial rossby wave which is shown to be associated with a deepening of the mixed layer and positive sea surface temperature sst anomalies of the order of 0 5 1 c these sst anomalies are not attributable to forcing by surface fluxes which are weak for the case studies analysed furthermore composite analysis suggests that such forcing is consistently important for triggering primary events the relationship is much weaker for successive events due to the many other triggering mechanisms which operate during periods of cyclical mjo activity this oceanic feedback mechanism is a viable explanation for the sporadic and broadband nature of the mjo additionally it provides hope for forecasting mj events during periods of inactivity when mjo forecasts generally exhibit low skill copyright c 2011 royal meteorological society

geostatistics in glaciology implications of a study of scharffenbergbotnen dronning maud land east antarctica geostatistical methods are applied in the analysis of radio echo data from scharffenbergbotnen dronning maud land east antarctica in order to allow the following investigations detailed and reliable cartography of subglacial bed topography and ice thickness comparison of recent ice flow patterns and ice flow during earlier glacial maxima and mass balance studies in relation to climatic changes

coral reefs and growth dynamics of a low angle carboniferous platform records from tianlin southern china abstract metazoan reef building receded globally during the carboniferous after the late devonian extinction events shallow water bioconstructions were generally small and scarce and corals played a minor role in their construction however in southern china one large 50 m high and three small 6 16 m high coral reefs dating from the late visean serpukhovian have recently been discovered in two localities in guangxi to understand the occurrence of these coral reefs and to constrain the factors that controlled their growth three sections around langping guangxi were measured and selected samples were analysed using petrography biostratigraphy and chemostratigraphy the depositional environment of these exceptional mississippian reefs was interpreted as a low angle platform 1 2 5 recording oligotrophic conditions and normal salinity the three small reefs have grown around the fair weather wave base whereas the large coral reef has grown in a deeper environment between the fair weather and storm wave base during carboniferous the global temporal reef distribution can be partly ascribed to paleoclimate changes however in southern china the growth of extended mississippian coral reefs is restricted to a short time window the late visean serpukhovian which coincides with high amplitude and high frequency sea level fluctuations most likely related to glacial pulses recent studies revealed that several rugose coral species survived the mid carboniferous glaciation event thanks to the persistence of warm water ocean currents maintaining tropical conditions on the platform due to the scarcity of extended coral reefs elsewhere it cannot be excluded that tianlin provided an ecological refuge for corals related to oceanic currents another potential favorable factor could be the mid ramp depositional setting the deep water platform areas could potentially provide more stable conditions less affected by global stress events however the deep reef refugia hypothesis remains debatable as only very few studies have explored its validity at the community level even if the causes of the occurrence of an extended coral reef in southern china cannot be fully constrained the existence of this large coral framework in the late visean serpukhovian provides additional evidence that coral communities did build reefs after the late devonian extinction events

ice thickness and bedrock elevation in western neuschwabenland and berkner island antarctica in 1985 86 western neuschwabenland was surveyed with an electromagnetic reflection system emr over flight tracks totalling 6100 km the area spans a triangle from ekstrom ice shelf and heimefront range to the kraul mountains vestfjella and covers 48 000 km2 data on surface elevation ice thickness and bedrock topography are presented in maps the bedrock elevation map shows more detail than earlier compilations with a remarkable graben like structure north of the heimefront range and large areas of bedrock below sea level in the same season tracks totalling 1600 km were flown over berkner island high electromagnetic reflectivity was found over the southern part of berkner island whereas the northern part showed considerably lower reflectivity we believe that this is due to melting conditions in the southern part and freezing conditions in the northern part

impact of remote equatorial winds and local mesoscale eddies on the existence of river in the sea along the east coast of india inferred from satellite smap

shelf progradation on a glaciated continental margin queen maud land antarctica abstract a detailed survey of the continental margin in the eastern weddell sea demonstrates shelf progradation by material input from discrete glacial wedges that amalgamate to form the present near rectilinear shelf edge kvitkuven ice rise is located between two trough mouth fans and rests on a thick sediment substratum that predates the shelf sequences north of it shelf progradation west of the ice rise preceded the progradation east of it in this way the seaward progression of a shelf edge may reflect the broad scale expansion of the east antarctic ice sheet but the timing of shelf progradation can be different in adjacent areas the progradational glacial wedges on the continental shelf mapped by this survey are correlated stratigraphically to be within the post late miocene glacial sequence drilled at odp site 693 on the middle continental slope 200 km to the northeast two submarine moraine ridge complexes on the shelf parallel the shelf edge a radiocarbon age of 18 950 280 years bp from the front of the inner complex water depth 319 m suggests that grounded ice at most reached the present mid shelf area in front of the ice rise during the late wisconsin glacial maximum or had retreated to this position at that time

intraseasonal variability of the equatorial undercurrent in the indian ocean by analyzing in situ observations and conducting a series of ocean general circulation model experiments this study investigates the physical processes controlling intraseasonal variability isv of the equatorial undercurrent euc of the indian ocean isv of the euc leads to time varying water exchanges between the western and eastern equatorial indian ocean for the 2001 14 period standard deviations of the euc transport variability are 1 92 and 1 77 sv 1 sv 10 6 m 3 s 1 in the eastern and western basins respectively the isv of the euc is predominantly caused by the wind forcing effect of atmospheric intraseasonal oscillations isos but through dramatically different ocean dynamical processes in the eastern and western basins the stronger isv in the eastern basin is dominated by the reflected rossby waves associated with intraseasonal equatorial zonal wind forcing it takes 20 30 days to set up an intraseasonal euc anomaly through the kelvin and rossby waves associated with the first and second baroclinic modes in the western basin the peak intraseasonal euc anomaly is generated by the zonal pressure gradient force which is set up by radiating equatorial kelvin and rossby waves induced by the equatorial wind stress directly forced and reflected rossby waves from the eastern basin propagate westward contributing to intraseasonal zonal current near the surface but having weak impact on the peak isv of the euc

a synthetic aperture radio echo experiment at storglaciaren sweden une experience de sondage par echo radio sensible a la polarisation a ete effectuee sur le glacier storglaciaren suede dans le but de rechercher et d examiner les echos radio emanant de cibles individuelles sous glaciaires six cibles principales ont ete identifiees et la force des echos indique que ces cibles sont probablement des cavites renfermant de l eau il n a pas ete possible de dire si ces cavites font parties d un systeme connecte de canaux sous glaciaires

mississippian paleocean chemistry from biotic and abiotic carbonate muleshoe mound lake valley formation new mexico u s a abstract it has been proposed that phanerozoic variation in the mg ca ratio of seawater has resulted in variation in the primary mineralogies of shallow water carbonates between aragonite and calcite dominated seas to test this hypothesis this study estimates the mississippian oceanic mg ca and sr ca ratios from the composition of marine carbonate cements and crinoidal carbonate both of which have been suggested to faithfully record seawater chemistry the early mississippian tournaisian visean muleshoe mound lake valley fm alamogordo nm u s a lends itself well to this endeavor because it contains abundant crinoids and marine carbonate cement stable isotope and elemental analyses as well as cathodoluminescence characteristics elucidate the diagenetic history of the bioherm and identify the least diagenetically altered materials for reconstruction of paleoseawater chemistry isotopic analyses document two diagenetic trends one meteoric and one burial diverging from values similar to literature estimates of mississippian marine calcite 1 5 18o 4 5 13c the burial diagenetic trend follows from this origin to more negative oxygen values 7 18o 3 13c the meteoric diagenetic trend is defined by a meteoric calcite line at 3 18o similarity of non luminescent marine cement and non luminescent crinoid isotopic and elemental compositions suggests that crinoidal carbonate was completely replaced by cement in the marine environment average elemental ratios for least altered marine cements are mg ca 11 mmol mol sr ca 0 2 mmol mol mn ca 0 2 mmol mol and fe ca 0 4 mmol mol early mississippian seawater is estimated to have had a mg ca ratio of 0 2 0 3 mol mol this mg ca ratio is compatible with the early mississippian being an interval of calcite sea conditions and compares well with the devonian estimate from marine cements 0 5 though it is 5 10 times lower than estimates from mass balance modeling the sr ca for early mississippian seawater was between 0 5 and 0 9 mmol mol which is much lower than previous estimates of 6 mmol mol from brachiopod calcite and argues for the development of a sr sink aragonite in the latest devonian to earliest mississippian

improved accuracy of cross borehole radar velocity models for ice property analysis cross borehole radar xbhr is widely used for the quantification of pore scale liquid water in geologic materials inferred from bulk velocity variations caused by differences in electromagnetic properties between the water and the surrounding material the xbhr can accurately and repeatedly measure variation at depth with sampled material remaining under natural stresses while maintaining good lateral sampling however even small errors in measured radar velocities result in large errors in water content estimates emphasizing the need to quantify and minimize errors we have rigorously assessed the sources of uncertainty in xbhr surveys undertaken in a glaciological setting we have summarized and quantified the three main areas of uncertainty in data collection 1 instrument time drift 2 first break picking and 3 borehole geometry our analysis of field data indicated that contemporary acquisition procedures can produce velocity errors of 3 0 0 0050 m ns equivalent to 0 84 vol water content we have developed several revisions to produce improved data acquisition through enhancement of existing techniques the velocity uncertainties were improved to 1 5 we also found the measurement of borehole diameter during hot water drilling which could hypothetically further reduce the velocity uncertainty to 0 8 equivalent to 0 2 vol water content the need for such precise measurement is clear because an increase in englacial water content from 0 to 0 8 has been proven to triple the strain rate and soften the ice liquid water between ice crystals has also been linked to faster velocities in ice streams and surging events

impact of atmospheric intraseasonal oscillations on the indian ocean dipole during the 1990s abstract effects of atmospheric intraseasonal oscillations isos on the indian ocean zonal dipole mode iozdm are investigated by analyzing available observations and a suite of solutions to an ocean general circulation model namely the hybrid coordinate ocean model hycom data and model solutions for the period 1991 2000 are analyzed a period that includes two strong iozdm events during 1994 and 1997 and a weak one in 1991 both the data analysis and model results suggest that atmospheric isos play a significant role in causing irregularity of the two strong iozdm events and the premature termination of the weak one of particular interest is a basinwide wind driven oceanic resonance with a period near 90 days involving the propagation of equatorial kelvin and first meridional mode rossby waves across the basin before the onset of the strong 1997 dipole wind variability had significant power near 90 days and the resonance was strongly excited associated with the resonance was a deepened t

structure of intraseasonal kelvin waves in the equatorial pacific ocean abstract previous studies have shown that intraseasonal kelvin waves are a prominent mode of variability in the eastern and central equatorial pacific these waves appear to be remotely forced by wind variations in the western pacific and propagate eastward at approximately first baroclinic mode phase speeds in this study moored temperature and velocity time series data from 1984 to 1987 between 110 and 140 w are studied to isolate the kelvin wave structures and to document their wave mean flow interactions with the south equatorial current equatorial undercurrent ruc system observed structures at periods of 59 125 days have rms amplitudes of about 10 cm s 1 for zonal velocity and about 1 c for temperature in the thermocline these structures exhibit significant departures from linear no mean flow theory zonal velocity is intensified below the euc core and temperature variability in the thermocline is weaker on the equator than 1 5 off the equator additionally the wave temperature signal at the

dynamical ocean forcing of the madden julian oscillation at lead times of up to five months abstractthe authors show that a simple three dimensional ocean model linearized about a resting basic state can accurately simulate the dynamical ocean response to wind forcing by the madden julian oscillation mjo this includes the propagation of equatorial waves in the indian ocean from the generation of oceanic equatorial kelvin waves to the arrival of downwelling oceanic equatorial rossby waves in the western indian ocean where they have been shown to trigger mjo convective activity simulations with idealized wind forcing suggest that the latitudinal width of this forcing plays a crucial role in determining the potential for such feedbacks forcing the model with composite mjo winds accurately captures the global ocean response demonstrating that the observed ocean dynamical response to the mjo can be interpreted as a linear response to surface wind forcing the model is then applied to study primary madden julian events which are not immediately preceded by any mjo activity or by any apparen

volume transports of the wyrtki jets and their relationship to the indian ocean dipole the equatorial indian ocean is characterized by strong eastward flows in the upper 80 100 m during boreal spring and fall referred to as the wyrtki jets these jets are driven by westerly winds during the transition seasons between the southwest and northeast monsoons and represent a major conduit for mass and heat transfer between the eastern and western sides of the basin since their discovery over 40 years ago there have been very few estimates from direct observations of the volume transports associated with these currents in this paper we describe seasonal to interannual time scale variations in volume transports based on 5 years of unique measurements from an array of acoustic doppler current profilers in the central equatorial indian ocean the array was centered at 0 80 5 e and spanned latitudes between 2 5 n and 4 s from august 2008 to december 2013 analysis of these data indicates that the spring jet peaks in may at 14 9 2 9 sv and the fall jet peaks in november at 19 7 2 4 sv around which there are year to year transport variations of 5 10 sv the relationship of the interannual transport variations to zonal wind stress forcing sea surface temperature sea surface height and surface current variations associated with the indian ocean dipole iod are further highlighted we also illustrate the role of wind forced equatorial waves in affecting transport variations of the fall wyrtki jet during the peak season of the iod

strong intraseasonal variability of meridional currents near 5 n in the eastern indian ocean characteristics and causes abstractthis paper reports on strong intraseasonal upper ocean meridional currents observed in the indian ocean between the bay of bengal bob and the equator and elucidates the underlying physical processes responsible for them in situ measurements from a subsurface mooring at 5 n 90 5 e reveal strong intraseasonal variability of the meridional current with an amplitude of 0 4 m s 1 and a typical period of 30 50 days in the upper 150 m which by far exceeds the magnitudes of the mean flow and seasonal cycle such prominent intraseasonal variability is however not seen in zonal current at the same location further analysis suggests that the observed intraseasonal flows are closely associated with westward propagating eddylike sea surface height anomalies sshas along 5 n the eddylike sshas are largely manifestations of symmetric rossby waves which result primarily from intraseasonal wind stress forcing in the equatorial waveguide and reflection of the equatorial kelvin waves at the eastern bou

growth dynamics of pennsylvanian carbonate mounds from a mixed terrigenous carbonate ramp in the puebla de lillo area cantabrian mountains northern spain abstract carbonate mounds are widespread in many places around the world and are especially well exposed in the cantabrian mountains northern spain this study focuses on the composition and growth dynamics of two large mound complexes well exposed near the village of puebla de lillo 70 km northeast of leon and evaluates the impact of sea level accommodation and siliciclastic input on mound growth the mound substrate consists of bedded dark skeletal bindstone the core facies exhibits patchy growth forms of alternating massive microbial algal boundstone and skeletal and nonskeletal wackestone reflecting the overall mound internal composition of smaller coalescent bodies microbial activity as inferred from the volumetrically important clotted peloids appears to be the main factor leading to the high accumulation rate in the cores the steeply dipping flanks presumably resulted from early cementation and subsequent lithification and stabilization induced mainly by microbial activity in the intermound strata carbonate beds and small mounds alternate with fine grained sandstone siltstone and shales the intermound carbonates consist of skeletal and intraclastic mudstone to wackestone whereas algal microbial boundstone is a minor component overall facies transition from the mound core towards the flanks or the mound capping beds is gradual however the volume of bioclasts and intraclasts increases towards the flank and capping facies inversely to amount of clotted peloids or micrite the substrate and the cores of the two mound complexes likely formed in the photic zone as inferred from the common calcareous algae carbonate precipitation favored by microbial activity and algal growth along with gain in accommodation space led to mound core accretion the growth of the small mound complexes was most likely stopped by recurrent sea level fall and siliciclastic input the large high relief mound complex actually kept growing until reaching shallow water and high energy conditions unlike many late paleozoic counterparts these mounds were not subaerially exposed during growth the great thickness and the aggradational mound growth are indicative of a high subsidence rate at a later stage however siliciclastic input also buried the large mound complex rapid subsidence sea level fluctuations and siliciclastic input were thus decisive factors controlling carbonate production this study reveals that mound complexes nucleated and grew on preexisting paleohighs maintaining consistent growth in these specific settings paleohighs recurrent sea level fluctuations presumably linked to glacio eustasy and episodic siliciclastic input are the principal factors that controlled the shape size and growth evolution furthermore the internal architecture as a mosaic of juxtaposed small bodies composing the complexes represents an important finding for better understanding of mound growth and thus for better constraining reservoir heterogeneity particularly for upper paleozoic deposits

radio and electrical measurements on glacial streams we discuss the suggestion that small under water transmitters might be used to illuminate the interior of major englacial water channels with radio waves once launched the radio waves would naturally tend to be guided along the channels until attenuated by absorption and by radiative loss receivers placed within the channels or at the glacier surface could be used to detect the signals they would provide valuable information about the connectivity of the water system the electrical conductivity of the water is of crucial importance a surface stream on storglachlren in sweden was found using a low frequency technique to have a conductivity of approximately 4 x 10 4 s m i although this is several hundred times higher than the conductivity of the surrounding glacier ice the contrast is not sufficient to permit us simply to use electrical con ductivity measurements to establish the connectivity of englacial water channels however the water conductivity is sufficiently small that under favourable circumstances radio signals should be detectable after travelling as much as a few hundred metres along an englacial water channel in a preliminary field experiment we demonstrated se mi quantitatively that radio waves do indeed propagate as expected at least in surface streams we conclude that under water radio transmitters could be of real practical value in the study of the englacial water system provided that sufficiently robust devices can be constructed in a subglacial channel however we expect the radio range would be much smaller the environment much harsher and the technique of less practical value

wind driven response of the upper ocean along the u s west coast to tropical mjo convection in this study time lagged composites of oscar upper ocean currents from february to may of 1993 2016 were binned by active phase of the leading atmospheric mode of intraseasonal variability the madden julian oscillation mjo seven days after the convectively active phase of the mjo is present in the tropical indian ocean anomalously strong south southeastward upper ocean currents are seen along nearly the entire u s west coast seven days after the convectively active phase is present in the tropical western pacific ocean upper ocean current anomalies reverse along the u s west coast with weaker southward flow a physical pathway to the ocean was found for both of these phases a tropical mjo convection modulates upper tropospheric heights and circulation over the pacific ocean b those anomalous atmospheric heights adjust the strength and position of the aleutian low and hawaiian high c surface winds change in response to the adjusted atmospheric pressure patterns and d those surface winds project onto upper ocean currents

where did ancient carbonate mounds grow in bathyal depths or in shallow shelf waters abstract carbonate mounds are important and ubiquitous components of the sedimentary rock record throughout the phanerozoic nevertheless factors controlling their occurrence and growth remain enigmatic in particular because the depositional depths of such mounds are poorly constrained and it is assumed that fossil examples lack modern analogues factors currently used to constrain the water depth that ancient mounds grew in include water energy occurrence of specific organisms that perform photosynthesis particularly calcareous algae and distinct non biogenic components in reviewing the main criteria used to delineate water depth of formation of fossil carbonate mounds most if not all criteria traditionally used to assume shallow water settings appear to be no longer substantiated in the light of current knowledge gained from modern carbonate mounds high energy assumed to indicate shallow water conditions is ongoing in water as deep as 1000 m the occurrence of peloids and processes such as micritization is not diagnostic of water depth furthermore virtually none of the calcareous algae assumed to indicate the photic zone have a taxonomically granted affiliation over the last years research in the deep ocean in particular thanks to the deployment of new devices and techniques provided a good database revealing a wide distribution of modern carbonate mounds reviewing the characteristics of ancient carbonate mounds with emphasis on depositional settings and confronting the criteria used with current knowledge from sub recent and modern carbonate mounds we conclude that for many ancient mounds a bathyal origin is at least as likely as a shallow water origin this conclusion is well supported by the sedimentary records left by these modern mounds that are astonishingly similar to those seen in palaeozoic and mesozoic carbonate mounds

design and operation of a portable digital impulse radar we have constructed a back portable impulse radar instrument that weighs roughly 12 kg can be powered by dry cells and records and stores data digitally the radar is controlled by an on board purpose built microcomputer that ensures simple field operation facilitates modifications and allows unattended operation when investigating time varying targets the transmitting unit is triggered from the receiver via an optical link and generates an electromagnetic wavelet by discharging two high voltage capacitors through back to back silicon controlled rectifiers into a resistively loaded dipole antenna successful field operations carried out during the summers of 1986 and 1987 include depth profiling as well as studies of englacial and subglacial targets on several temperate and sub polar glaciers

are reefs and mud mounds really so different although both ecologic reefs and mud mounds are demonstrably rigid framework reefs they are still considered to be distinct in terms of their dominant processes of formation and preferred environmental settings this distinction has rested largely upon the assumption that ecologic reefs are dominated by skeletal metazoans growing in shallow waters in contrast to the complex autochthonous micrite supported cavity systems that characterise deep water mud mounds now considered to represent either organomineralic deposits where carbonate precipitation has taken place in association with nonliving organic substrates to form automicrite or various types of microbialite where carbonate forms as a direct result of the physiological activity or decay of benthic microorganisms yet such autochthonous micrite is increasingly recognised as an important component of many ancient shallow ecologic reefs as well as some modern coral reefs and indeed may contribute locally up to 80 of the reef rock these observations raise doubts as to the validity of current fabric based definitions used to distinguish between mud mounds and ecologic reefs whether the autochthonous micrite in mud mounds proves to be dominated by either automicrite or microbialite both require particular environmental conditions for their formation automicrites form where surplus organic matter from metazoans has degraded to release quantities of acidic amino acids with a significant ability to bind ca 2 and microbialite formation also often requires either unusual marine chemistries or ecological conditions such conditions might include changes in terrigenous influx ground water seepage local anoxia and increases in the ph of interstitial reef waters or in nutrient concentration d 2001 elsevier science b v all rights reserved

a radar transparent layer in a temperate valley glacier bench glacier alaska radar surveys of bench glacier alaska collected over five field seasons between 2002 and 2006 reveal a surface layer of radar transparent ice in this temperate valley glacier the transparent layer covers the up glacier half of the ablation zone and is defined by a distinct lack of the radar scattering events considered typical of temperate ice radar scattering ice underlies the transparent zone and extends to the surface elsewhere on the glacier we observed the layering in constant offset radar surveys conducted with characteristic frequencies ranging from 5 mhz to 100 mhz the radar transparent layer extends from the surface to 20 m depth on average but up to 50 m in some places bench glacier s transparent layer appears similar to the cold surface layer of polythermal glaciers however observations in over 50 boreholes on bench glacier suggest there is no cold ice corresponding to the radar transparent layer we conclude that spatially extensive radar transparent layers normally used to identify cold ice in polythermal glaciers are present in some temperate glaciers copyright 2009 john wiley sons ltd

from detached to attached carbonate buildup complexes 3d seismic data from the upper palaeozoic finnmark platform southwestern barents sea abstract carbonate buildups were abundant during the palaeozoic three dimensional seismic data from the finnmark platform barents sea has been used to reconstruct the evolution of laterally extensive carbonate buildup complexes in space and time the results suggest that the location of upper palaeozoic warm and cool water carbonate buildups from the finnmark platform is controlled by faults and the sea floor morphology at the time of their growth a fluctuating sea level affected the growth of the carbonate buildups but they also influenced their own environment by forming lagoons atoll like ridges and possibly areas with restricted circulation warm water carbonate buildups forming ridges and isolated mounds occur in the gipsdalen group latest serpukhovian mid sakmarian where they initially grew in a detached platform setting the carbonate buildups are several tens of kilometres long up to 2 5 km wide and 300 m thick and interpreted to consist of vertically stacked complexes of sub seismic scale carbonate buildups evaporites were deposited and later subject to karstification possibly during a period of sub aerial exposure before a transgression and the subsequent carbonate deposition and buildup growth bridged the detached platform with the attached platform in the bjarmeland group lower permian 0 35 4 8 km wide 1 5 27 km long and 60 420 m thick cool water bryozoan dominated straight sinuous and continuous carbonate ridges or atoll like ridges are located on top of the warm water carbonate structures three dimensional maps of upper palaeozoic carbonate buildups document their geomorphology distribution and size through time the lateral and vertical growth of carbonate buildups has been reconstructed revealing how their distribution changed over time and with changing environmental settings

intraseasonal response of the northern indian ocean coastal waveguide to the madden julian oscillation a new observational record of upper ocean currents at 15 n on the western coast of india is dominated by intraseasonal 55 110 day variations of alongshore currents whereas sea level at the same location has a clear seasonal signal these observations can be interpreted within the framework of linear wave theory at 15 n the minimum period for planetary waves is 90 day meaning that intraseasonal energy is largely trapped at the coast in the form of poleward propagating kelvin waves while lower frequency signals associated with the annual cycle can radiate offshore as planetary waves this dynamical difference results in a steeper offshore slope of sea level at intraseasonal timescale and thus stronger geostrophic alongshore currents a consequence is that the alongshore currents are in phase with intraseasonally filtered sea level near the coast and a gridded satellite product is shown to reproduce the current variations reasonably well the intraseasonal current variations along the west coast of india are part of basin scale sea level fluctuations of the northern indian ocean equatorial and coastal waveguides the wind forcing associated with this basin scale circulation closely matches surface wind signals associated with the madden julian oscillation copyright 2009 by the american geophysical union

tv video observations of bed and basal sliding on storglaciaren sweden four boreholes in storglaciaren a small valley glacier in northernsweden were inspected with a video camera in two of the boreholes the apparentglacier bed was filmed in one borehole the bed was found to be composed of softsediment but in the other it consisted of bedrock in the latter the camera moved5 6 mm relative to the bed during an 80 min period the recorded camera movementshowed a background motion which is in the expected range of basal sliding superimposed on the background motion a jerky motion of a high speed spike wasfound the jerky motion is interpreted as a stress release induced by local topographyat the ice bed interface

characteristic trace fossil associations in oxygen poor sedimentary environments the sedimentologic record of oxygen poor depositional environments typically includes trace fossils produced by deposit feeding organisms we propose an oxygen controlled trace fossil model in which increasing oxygen concentration of interstitial water in sediment parallels a transition from fodinichnia dominated through pascichnia dominated to domichnia dominated trace fossil associations in certain places such as parts of the late paleozoic oquirrh basin in utah this model provides a reasonable alternative to the more traditional depth controlled model of trace fossil distribution

subglacial preservation of valley morphology at amundsenisen western dronning maud land antarctica on the high altitude polar plateau of amundsenisen western dronning maud land east antarctica a subglacial valley with a broad horizontal valley floor interpreted as a sediment floodplain or valley delta was studied by radio echo sounding in addition a small probably glacial valley was mapped within the same subglacial massif basal ice temperatures were calculated using field data on precipitation air temperature and ice sheet thickness discoveries of old landforms which have been preserved more or less intact beneath the former fennoscandian and laurentide ice sheets have received increasing attention during the last decade the aim of this study is to investigate whether preservation of landforms occurs under the east antarctic ice sheet and to discuss under that climatological and glaciological circumstances preservation may take place the results show that the ice sheet covering the investigated localities is frozen to bed and therefore has an insignificant erosional capability the observations suggest that a large scale subglacial sediment deposit and a small valley formed by glacial erosion have survived beneath a cold based ice sheet marginal zone for a long time period the process of glacial preservation recognized for bedrock features and tentatively observed for sediment accumulations should act on similar large scale landforms under any cold based ice sheet present or past on the basis of existing studies of the age and stability of the east antarctic ice sheet a middle pliocene age is suggested for the preserved landforms the presence of the presumed sediment filled valley further indicates that no prolonged periods of basal melting have occurred at the amundsenisen study area during the ice sheet history which includes the quaternary glaciation periods finally calculations of basal temperature for localities at different altitudes within the same subglacial massif were used to demonstrate local altitudinal control of glacial preservation 1997 by john wiley sons ltd

dynamics of intraseasonal sea level and thermocline variability in the equatorial atlantic during 2002 03 abstract satellite and in situ observations in the equatorial atlantic ocean during 2002 03 show dominant spectral peaks at 40 60 days and secondary peaks at 10 40 days in sea level and thermocline within the intraseasonal period band 10 80 days a detailed investigation of the dynamics of the intraseasonal variations is carried out using an ocean general circulation model namely the hybrid coordinate ocean model hycom two parallel experiments are performed in the tropical atlantic ocean basin for the period 2000 03 one is forced by daily scatterometer winds from the quick scatterometer quikscat satellite together with other forcing fields and the other is forced by the low passed 80 day version of the above fields to help in understanding the role played by the wind driven equatorial waves a linear continuously stratified ocean model is also used within 3 s 3 n of the equatorial region the strong 40 60 day sea surface height anomaly ssha and thermocline variability result mainly from the

tropical pacific ocean and the madden julian oscillation role of wind and buoyancy forcing 1 a global ocean circulation model is used to examine the dynamical response of the tropical pacific ocean to forcing associated with the madden julian oscillation mjo model sensitivity experiments first reveal that mjo related changes in sea level are caused primarily by changes in wind stress further the mjo related changes in sea surface temperature sst are mainly caused by buoyancy heat flux in the indian ocean by wind stress in the central tropical pacific and by both buoyancy flux and wind stress in the eastern tropical pacific additional model sensitivity studies quantify the tropical pacific ocean response to mjo wind forcing the simulations reveal that the subsurface temperature variations associated with the mjo propagate eastward along the thermocline and rise to the surface in the eastern pacific zonal advection plays a dominant role in sst variation in the central pacific vertical advection plays an important role in the evolution of subsurface and surface temperatures in the eastern pacific finally it is shown that mjo wind forcing can rectify sst variations through nonlinear interactions of the intraseasonal variations of the zonal currents and the zonal sst gradient

a dynamical ocean feedback mechanism for the madden julian oscillation composite analysis is applied to study the dynamical ocean response to madden julian mj events measured by anomalies in sea surface height from the merged topex poseidon european remote sensing satellite altimetry dataset in each of the tropical ocean basins significant equatorial waves are forced which are shown to modulate the sea surface temperature sst by 0 2 0 3 degc in the absence of strong surface heat fluxes in the indian ocean there is a clear dynamical response which may play a significant role in generating later mj events surface westerly winds associated with the active phase of the madden julian oscillation mjo force an eastward propagating oceanic downwelling equatorial kelvin wave which on reaching the eastern boundary at sumatra forces reflected downwelling equatorial rossby waves and coastal kelvin waves the coastal kelvin waves propagate southwards towards northern australia and northwards into the bay of bengal and will be important for local physical chemical and biological processes the equatorial rossby waves propagate westward across the indian ocean arriving in the western indian ocean approximately 80 100 days after the initial kelvin wave was generated the arrival of these waves generates positive sst anomalies which leads to convection and may trigger the next but one mj event or amplify the low frequency tail of the mjo this constitutes a coupled feedback mechanism from the ocean dynamics onto the mjo somewhat similar to the delayed oscillator mechanism for the el nino southern oscillation

anisotropic radio wave scattering from englacial water regimes mýrdalsjokull iceland colinear polarized 5 mhz radar profiling data were obtained on m rdalsjokull a temperate glacier in iceland radar transects and therefore polarization planes were aligned approximately parallel transverse and oblique to the ice flow direction echoes from the shallower half to two thirds of the ice were 10 20db stronger on the oblique and longitudinal transects than those on the transverse transects anisotropy as a function of depth is clearly seen at the sites where the transects cross strong scattering on longitudinal transects apparently caused extinction of a radar reflecting layer that was continuously profiled on the transverse transects a radio wave scattering model shows that scattering from a longitudinal water filled conduit parallel to the glacier surface can explain the observed azimuthal variations of the echo we conclude that low frequency mhz radio waves can help to characterize englacial water regimes

intraseasonal variability of sea surface height in the bay of bengal intraseasonal variability isv of sea surface height ssh over the bay of bengal bob is studied using altimetry data and an eddy resolving ocean model in both the model hindcast and satellite observations large ssh isv is found along the eastern and northern coasts of the bob in the western bob and in a zonal band across the bay centered near 5 degrees n the isv displays a clear seasonality in the western bob it reaches its annual maximum in spring whereas it does so in summer and autumn southeast of sri lanka driven by equatorial intraseasonal winds equatorial kelvin waves propagate eastward reach the western coast of sumatra and reflect there to propagate around the perimeter of the bob as coastally trapped waves two distinct bands of high eddy activity are detected in the western and central bob respectively in both bands isolated eddies propagate southwestward eddy formation in the eddy train in the central bay is linked to the coastal wave as it bends around the corner of the irrawaddy delta off myanmar eddy activity contributes to the high isv in the central bay to some extent an energetics analysis indicates that high total eddy energy in the western bob is due to barotropic baroclinic instability of the mean current citation cheng x s p xie j p mccreary y qi and y du 2013 intraseasonal variability of sea surface height in the bay of bengal j geophys res oceans 118 816 830 doi 10 1002 jgrc 20075

interpretation of radio echoes from storglaciaren northern sweden analyse des echos d ondes metriques et decimetriques a l aide d une theorie d onde scalaire de la diffraction et d une statistique simple on peut par exemple etudier les rugosites du lit et les orientations des diffuseurs a l interieur de la glace

impact of atmospheric intraseasonal variability in the indian ocean low frequency rectification in equatorial surface current and transport an ocean general circulation model ogcm is used to investigate the low frequency period longer than 90 days rectification of atmospheric intraseasonal variability 10 90 day periods in zonal surface current and transport of the equatorial indian ocean a hierarchy of ogcm solutions is found in an actual tropical indian ocean basin for the period of 1988 2001 to help to identify and isolate nonlinear processes a linear continuously stratified model and a 4 layer intermediate ocean model are also used results from the ogcm solutions suggest 1 2 that intraseasonal atmospheric forcing acts to weaken the equatorial seasonal surface currents amplitudes of the spring and autumn eastward surface jets the wyrtki jets wj and the westward surface current during january march are reduced by as much as 15 25 cm s21 by intraseasonal atmospheric forcing and strengths of the rectification exhibit a significant interannual variability important processes that cause the low frequency rectification are asymmetric response of mixed layer depth to easterly and westerly winds entrainment and upwelling of momentum during spring and autumn the westerly easterly phase of an intraseasonal event enhances weakens or even reverses the seasonal westerly winds increases decreases equatorial convergence and entrainment and thus deepens thins the mixed layer a net westward current is generated over an event mean because easterly wind acts on a thinner surface mixed layer whereas westerly wind acts on a thicker one in contrast during january march when the seasonal winds are equatorial easterlies surface currents are westward and equatorial undercurrents euc develop the rectified surface currents are eastward which reduces the westward surface flow this eastward rectification results largely from the vertical advection and entrainment of the euc the seasonal to interannual variability of the rectified surface flow is determined primarily from the seasonal cycle and interannual variability of the background state seasonal to interannual variability of the intraseasonal wind forcing also contributes the rectified low frequency zonal volume heat transports integrated over the entire water column along the indian ocean equator are persistently eastward with an amplitude of 0 15 3 106 m3 s 21 0 1 2 pw this is because westerly winds generate equatorial downwelling advecting the surface eastward momentum downward and giving an eastward subsurface current easterly winds cause equatorial upwelling and produce an eastward pressure gradient force that drives an eastward subsurface current this eastward subsurface current is advected upward by upwelling the mean effect over an intraseasonal event at the equator is to increase the eastward transport in the water column in the layers above the thermocline the rectified zonal volume heat transports are in the same direction as the rectified surface currents results from this paper may have important implications for understanding climate variability because modification of wj strength and transports can affect the sst and heat storage in the equatorial indian ocean warm pool

dynamics of andaman sea circulation and its role in connecting the equatorial indian ocean to the bay of bengal circulation in the bay of bengal bob is driven not only by local winds but are also strongly forced by the reflection of equatorial kelvin waves ekws from the eastern boundary of the indian ocean the equatorial influence attains its peak during the monsoon transition period when strong eastward currents force the strong ekws along the equator the andaman sea lying between the andaman and nicobar island chains to its west and indonesia thailand and myanmar to the south east and north is connected to the equatorial ocean and the bob by three primary passages the southern 6 n middle 10 n and northern 15 n channels we use ocean circulation models together with satellite altimeter data to study the pathways by which equatorial signals pass through the andaman sea to the bob and associated dynamical interactions in the process the mean coastal circulation within the andaman sea and around the islands is primarily driven by equatorial forcing with the local winds forcing a weak sea level signal on the other hand the current forced by local winds is comparable to that forced remotely from the equator our results suggest that the andaman and nicobar islands not only influence the circulation within the andaman sea but also significantly alter the circulation in the interior bay and along the east coast of india implying that they need to be represented accurately in numerical models of the indian ocean

ice shelf dynamics near the front of the filchner ronne ice shelf antarctica revealed by sar interferometry fifteen synthetic aperture radar sar images of the ronne ice shelf also referred to as the filchner ronne ice shelf antarctica obtained by the european remote sensing satellites ers 1 and 2 are used to study ice shelf dynamics near two ends of the iceberg calving front interferograms constructed from these sar images are used to resolve the ice shelf displacement along several directions in response to both ocean tide and long term creep flow tidal motion is separated from creep flow using differential interferometry i e two or more interferograms in which fringe patterns common to all are predominantly associated with creep flow creep flow velocities thus determined compare well with prior ice shelf velocity surveys using these data we studied the influence of large scale rifts ice rises and coastal separation on the ice shelf flow many of the large rifts that appear to form the boundaries where tabular icebergs may eventually detach from the ice shelf are filled with a melange of sea ice ice shelf debris and wind blown snow the interferograms show that this melange tends to deform coherently in response to the ice shelf flow and has sufficient strength to trap large tabular ice shelf fragments for several decades before the fragments eventually become icebergs in many instances the motion of the tabular fragments is a rigid body rotation about a vertical axis that is driven by velocity shear within the melange the mechanical role of the rift filling melange may be to bind tabular ice shelf fragments to the main ice shelf before they calve this suggests two possible mechanisms by which climate could influence tabular iceberg calving first spatial gradients in oceanic and atmospheric temperature may determine where the melange melts and thus the location of the iceberg calving margin second melting or weakening of ice melange as a consequence of climate change could trigger a sudden or widespread release of tabular icebergs and lead to rapid ice shelf disintegration

seasonal changes in ground penetrating radar signature observed at a polythermal glacier bylot island canada in recent years ground penetrating radar gpr has been increasingly used for characterization of subglacial and englacial environments at polythermal glaciers the geophysical method is able to exploit the dielectric difference between water air sediment and ice allowing delineation of subsurface hydrological thermal and structural conditions more recent gpr research has endeavoured to examine temporal change in glaciers in particular the distribution of the cold ice zone at polythermal glaciers however the exact nature of temporal change that can be identified using gpr has not been fully examined this research presents the results of three gpr surveys conducted over the course of a summer ablation season at a polythermal glacier in the canadian arctic a total of approximately 30 km of gpr profiles were collected in 2002 repeatedly covering the lower 2 km of stagnation glacier bylot island 72 58 n 78 22 w comparison between profiles indicated changes in the radar signature including increased noise appearance and disappearance of englacial reflections and signal attenuation in the latter survey further an area of chaotic returns in up glacier locations which was interpreted to be a wet temperate ice zone showed marked recession over the course of the ablation season combining all the temporal changes that were detected by gpr results indicate that a polythermal glacier may exhibit strongly seasonal changes in hydrological and thermal characteristics throughout the ice body including the drainage of 17 000 m 3 of temporarily stored intra glacial meltwater it is also proposed that the liquid water content in the temperate ice zone of polythermal glaciers can be described as a fraction of a specific retention capacity copyright 2006 john wiley sons ltd

benthic carbonate factories of the phanerozoic marine carbonate precipitation occurs in three basic modes abiotic or quasi abiotic biotically induced and biotically controlled on a geologic scale these precipitation modes combine to form three carbonate production systems or factories in the benthic environment 1 tropical shallow water factory dominated by biotically controlled mainly photo autotrophic and abiotic precipitates 2 cool water factory dominated by biotically controlled mainly heterotrophic precipitates and 3 mud mound factory dominated by biotically induced mainly microbial and abiotic precipitates sediment accumulations of the factories differ in composition geometry and facies patterns and some of these differences appear prominently in seismic data thus facilitating subsurface prediction the characteristic accumulation of the tropical factory is the flat topped often reef rimmed platform in cool water systems reefs in high energy settings are scarce and hydrodynamic influence dominates producing seaward sloping shelves and deep water sediment drifts often armored by skeletal framework the typical accumulation of the mud mound factory is groups of mounds in deeper water where the mud mound factory expands into shallow water it forms rimmed platforms similar to the tropical factory the tropical factory is most productive the mud mound factory reaches 80 90 and the cool water factory 20 30 of the tropical growth rate the three factories represent end members connected by transitions in space transitions in time are linked to biotic evolution

origins of eddy kinetic energy in the bay of bengal by analyzing satellite observational data and ocean general circulation model experiments this study investigates the key processes that determine the spatial distribution and seasonality of intraseasonal eddy kinetic energy eke within the bay of bengal bob it is revealed that a complicated mechanism involving both local and remote wind forcing and ocean internal instability is responsible for the generation and modulation of eke in this region high level eke mainly resides in four regions east of sri lanka region 1 the western bob region 2 northwest of sumatra region 3 and the coastal rim of the bob region 4 the high eke levels in regions 1 and 2 are predominantly produced by ocean internal instability which contributes 90 and 79 respectively prominent seasonality is also observed in these two regions with higher eke levels in boreal spring and fall due to enhanced instability of the east indian coast current and the southwest monsoon current respectively in contrast ocean internal instability contributes 49 and 52 of the total eke in regions 3 and 4 respectively whereas the atmospheric forcing of intraseasonal oscillations isos also plays an important role isos produce eke mainly through wind stress involving both the remote effect of equatorial winds and the local effect of monsoonal winds equatorial origin wave signals significantly enhance the eke levels in regions 3 and 4 in the form of reflected rossby waves and coastal kelvin waves respectively the local wind forcing effect through ekman pumping also has a significant contribution in regions 3 and 4 24 and 22 respectively

oceanic impetus for convective onset of the madden julian oscillation in the western indian ocean abstracta theory for intraseasonal atmosphere ocean atmosphere feedback is supported whereby oceanic equatorial rossby waves are partly forced in the eastern indian ocean by the madden julian oscillation mjo reemerge in the western indian ocean 70 days later and force large scale convergence in the atmospheric boundary layer that precedes mjo deep convection downwelling equatorial rossby waves permit high sea surface temperature sst and enhance meridional and zonal sst gradients that generate convergent circulations in the atmospheric boundary layer the magnitude of the sst and sst gradient increases are 0 25 c and 1 5 c mm 1 1 megameter is equal to 1000 km respectively the atmospheric circulations driven by the sst gradient are estimated to be responsible for up to 45 of the intraseasonal boundary layer convergence observed in the western indian ocean the sst induced boundary layer convergence maximizes 3 4 days prior to the convective maximum and is hypothesized to serve as a trigger for

13c enriched carbonate in mississippian mud mounds alamogordo member lake valley formation sacramento mountains new mexico u s a abstract the origin of the carbonate mud constituting paleozoic mid shelf and deeper water mud mounds has long been debated mississippian mud mounds and their laterally adjacent coeval inter mound strata in the lake valley formation are well exposed along cliff faces in south central new mexico the mounds originated on erosional surfaces on a gently sloping ramp in 110 to 250 m water depth carbonate muds that constitute the inter mound strata mud mounds and syndepositional neptunian dikes within the mounds are low mg calcite microspars with similar petrographic cathodoluminescent and fluorescent characteristics carbon and oxygen stable isotope analyses demonstrate that the microspars constituting the inter mound mound and neptunian dikes have average 13c values of 2 6 0 2 3 4 0 6 and 4 8 0 3 pdb respectively additionally well preserved brachiopods from the inter mound strata and from muleshoe mud mound have 13c values markedly different from each other but similar to their surrounding microspars i e brachiopod s 2 7 and 3 9 pdb respectively the stable isotope distributions within each environment similarity of values between microspar and brachiopod data from the same depositional environments as well as agreement of 13c values with other investigations of coeval strata support the conclusion that the measured 13c values are essentially primary values it is envisioned that 13c enriched fluids sourced by bacterial fermentation in the subjacent strata rose into the mounds some through neptunian dikes and influenced the precipitation of the microspars in the mounds and dikes near the sediment water interface these fluids mixed with normal marine waters thus precipitating the microspars or their precursors which have high 13c values that characterize the mud mounds the inter mound microspars and inter mound brachiopods have the lowest 13c values and are in agreement with worldwide coeval marine calcites that is the inter mound microspars formed under normal marine conditions the high 13c values measured in all of the mound related samples indicate that all mounds received a contribution of 13c enriched waters this relationship indicates that microspar precipitation in the mounds was associated with seepage of methanogenic fluids from the underlying strata

numerical simulation of the observed near surface east india coastal current on the continental slope we simulate the east india coastal current eicc using two numerical models resolution 0 1 circ times 0 1 circ an oceanic general circulation model ogcm called modular ocean model and a simpler linear continuously stratified lcs model and compare the simulated current with observations from moorings equipped with acoustic doppler current profilers deployed on the continental slope in the western bay of bengal bob we also carry out numerical experiments to analyse the processes both models simulate well the annual cycle of the eicc but the performance degrades for the intra annual and intraseasonal components in a model resolution experiment both models run at a coarser resolution of 0 25 circ times 0 25 circ simulate well the currents in the equatorial indian ocean eio but the performance of the high resolution lcs model as well as the coarse resolution ogcm which is good in the eicc regime degrades in the eastern and northern bob an experiment on forcing mechanisms shows that the annual eicc is largely forced by the local alongshore winds in the western bob and remote forcing due to ekman pumping over the bob but forcing from the eio has a strong impact on the intra annual eicc at intraseasonal periods local equatorial forcing dominates in the south north because the kelvin wave propagates equatorward in the western bob a stratification experiment with the lcs model shows that changing the background stratification from eio to bob leads to a stronger surface eicc owing to strong coupling of higher order vertical modes with wind forcing for the bob profiles these high order modes which lead to energy propagating down into the ocean in the form of beams are important only for the current and do not contribute significantly to the sea level

origin of intraseasonal variability of circulation in the tropical central indian ocean observed upper ocean currents south of sri lanka exhibit large irregular fluctuations with periods of days to weeks an ocean model driven by daily surface winds is able to reproduce the observed fluctuations we find from model experiments that low frequency 30 50 day intraseasonal variability isv arises when rossby waves radiated from the eastern boundary are amplified by hydrodynamic instability in the eastern and central indian ocean high frequency 10 15 day isv is forced directly by isv of the wind field in the eastern indian ocean in spite of the contribution from instability the ocean circulation south of sri lanka is a deterministic response to wind forcing

from isolated buildups to buildup mosaics 3d seismic sheds new light on upper carboniferous permian fault controlled carbonate buildups norwegian barents sea abstract carbonate buildups are a common feature of many ancient carbonate platforms and were especially abundant during the palaeozoic our present understanding of buildup distribution and the ability to better predict their location is however hampered by the fact that maps of buildups rarely show evidence of widespread spatial organisation and indeed their distribution often appears chaotic a previously unrecognized pattern of buildup distribution has been revealed by three dimensional 3d seismic data recently acquired from the loppa high norwegian barents sea here syn rift carboniferous permian buildups are not isolated but are instead linked into a mosaic of laterally extensive ridges the buildups location is controlled by the intersection of three trends of syndepositional faults systematic organisation of buildup height width density and external form across the study area appears to have been controlled by changes in accommodation space driven by differential subsidence the buildups were remarkably long lived and developed over an interval of 35 ma despite this longevity buildup location remained relatively static and true to the underlying pattern of basement faults indicating that their progradation was likely restricted by a combination of factors including limited highstand production their depositional relief

impact of indian ocean dipole on intraseasonal zonal currents at 90 e on the equator as revealed by self organizing map a neural network pattern recognition approach called self organizing map som has been used to examine the impact of the indian ocean dipole iod on intraseasonal zonal currents in the eastern equatorial indian ocean this study shows that during negative iod events the intraseasonal zonal currents are mostly dominated by the first two modes on the other hand contributions from the higher modes to the intraseasonal zonal current significantly increase during positive iod events this is attributed to the change in the background stratification associated with the iod events the sharp pycnocline in the eastern basin during the positive iod events causes the wind forcing to project more onto the higher modes

short pulse radar wavelet recovery and resolution of dielectric contrasts within englacial and basal ice of matanuska glacier alaska u s a wavelets transmitted by short pulse radar are recovered from continuous profiles and used to determine interfacial dielectric contrasts within the englacial and basal ice at the terminus area of matanuska glacier alaska u s a the field studies were in the ablation region where radar horizons could at some point be identified with interfaces between clear ice and air water or basal ice and were performed in early spring before drainage fully developed the profiles usedclosely spaced antennas with bandwidths centered near 50 and 400 mhz transmitted wavelets reflected from interfaces of known dielectric contrasts are used to establish a phase reference for other events from interfaces between unknown contrasts migration and fourier transform filtering are then applied to the profiles and shown to recover these wavelets from diffractions and reflections interfacial dielectric contrasts are determined from the relative phase of the wavelets near the terminus lake some basal ice events above 8 m depth are interpreted as voids further up glacier most englacial events are interpreted as voids but deeper localized reflectors and horizons to 90 m depth and within the basal zone are interpreted as voids water or debris phase cannot be determined for the basal substrate transition reflections recommendations are made for improving the wavelet recovery process and the quality of gpr migration

numerical modelling of the ice sheet in western dronning maud land east antarctica impacts of present past and future climates time dependent ice sheet modelling of a 176 000 km2 area in western dronning maud land east antarctica provided information on the ice sheet s response to six climate change scenarios another experiment was done to study changes in ice thickness flow and basal temperature conditions between the present ice configuration and a simulated maximum palaeo ice sheet the input to the model included new datasets of bed and surface topography compiled for this study the results of the six climate change experiments including a 0 5 c per century global warming scenario show that the ice sheet has a robust behaviour with respect to the different climate changes the maximum change in ice volume was

basin resonances in the equatorial indian ocean abstractprevious studies have investigated how second baroclinic mode n 2 kelvin and rossby waves in the equatorial indian ocean io interact to form basin resonances at the semiannual 180 day and 90 day periods this paper examines unresolved issues about these resonances including the reason the 90 day resonance is concentrated in the eastern ocean the time scale for their establishment and the impact of complex basin geometry a hierarchy of ocean models is used an idealized one dimensional 1d model a linear continuously stratified ocean model lcsm and an ocean general circulation model ogcm forced by quick scatterometer quikscat wind during 2000 08 results indicate that the eastern basin concentration of the 90 day resonance happens because the westward propagating rossby wave is slower and thus is damped more than the eastward propagating kelvin wave results also indicate that superposition with other baroclinic modes further enhances the eastern maximum and weakens sea level

intraseasonal monsoon jets in the equatorial indian ocean the zonal wind in the equatorial indian ocean eqio is westerly almost throughout the year it has a strong semiannual cycle and drives the spring and fall wyrtki jets in addition high resolution daily satellite winds show westerly wind bursts lasting 10 40 days associated with atmospheric convection in the eastern eqio these bursts have the potential to produce intraseasonal eastward equatorial jets in the ocean using an ocean model driven by quikscat scatterometer winds we show that strong westerly bursts associated with summer monsoon intraseasonal oscillations can drive monsoon jets in the eastern eqio which have been observed recently although there are distinct equatorial wind bursts associated with madden julian oscillations in january march they do not produce equatorial jets in the ocean the role of ocean dynamics in producing the selective response of the ocean is discussed