the shape and internal structure of the moon from the clementine mission global topographic and gravitational field models derived from data collected by the clementine spacecraft reveal a new picture of the shape and internal structure of the moon the moon exhibits a 16 kilometer range of elevation with the greatest topographic excursions occurring on the far side lunar highlands are in a state of near isostatic compensation whereas impact basins display a wide range of compensation states that do not correlate simply with basin size or age a global crustal thickness map reveals crustal thinning under all resolvable lunar basins the results indicate that the structure and thermal history of the moon are more complex than was previously believed

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

subaqueous melting of store glacier west greenland from three dimensional high resolution numerical modeling and ocean observations we present three dimensional high resolution simulations of ice melting at the calving face of store glacier a tidewater glacier in west greenland using the massachusetts institute of technology general circulation model we compare the simulated ice melt with an estimate derived from oceanographic data the simulations show turbulent upwelling and spreading of the freshwater laden plume along the ice face and the vigorous melting of ice at rates of meters per day the simulated august 2010 melt rate of 2 0 0 3 m d is within uncertainties of the melt rate of 3 0 1 0 m d calculated from oceanographic data melting is greatest at depth above the subglacial channels causing glacier undercutting melt rates increase proportionally to thermal forcing raised to the power of 1 2 1 6 and to subglacial water flux raised to the power of 0 5 0 9 therefore in a warmer climate store glacier melting by ocean may increase from both increased ocean temperature and subglacial discharge key points simulated melt agrees with estimates from a hydrographic survey of the glacier with more runoff glaciers will melt faster at constant ocean temperature 2013 american geophysical union all rights reserved

submarine landforms in the fjords of southern chile implications for glacimarine processes and sedimentation in a mild glacier influenced environment abstract chilean fjords are the lowest latitude at which glaciers reach the sea today high accumulation and mass throughput sustain tidewater glacier margins in this relatively mild climatic and oceanographic setting 27 000 km 2 of swath bathymetry allow mapping of sea floor landforms and inferences on glacimarine sediments and sedimentation tidewater glaciers are present in several fjords beyond retreating tempano glacier a terminal moraine marks the limit of probable little ice age advance with smaller transverse ridges closer to the glacier beyond advancing pio xi glacier there are few signs of organised submarine landforms older moraine ridges along several fjords formed at still stands during deglaciation elsewhere meltwater fed braided rivers connect the glacial and marine sedimentary systems swath imagery shows glacifluvial and fluvial deltas with small channels and chutes that develop into long and sinuous turbidity current channels few iceberg ploughmarks and submarine slope failures were observed but several fields of pockmarks were present the fjords of chile are dominated by sediment delivery from turbid meltwater which distributes fine grained debris widely producing sorted and laminated fine grained ice proximal wedges and draping ice distal seismic architecture to give a predominantly smooth sea floor turbidity currents also transfer sediments to some ice distal environments the chilean fjordlands represent the mildest climatic and oceanographic end member of a continuum of glacier influenced marine settings similar to south east alaska in the northern hemisphere components of a landform assemblage model for climatically mild meltwater dominated fjords include ice contact moraine ridges glacifluvial and fluvial deltas and turbidity current channels full glacial and deglacial streamlined subglacial landforms are likely to have been buried in many areas by subsequent glacimarine sedimentation

submarine melting at the terminus of a temperate tidewater glacier leconte glacier alaska u s a heat fresh and sea water balances indicate that the late summer rate of submarine melting at the terminus of tidewater leconte glacier alaska u s a in 2000 was about 12md 1 w e averaged over the submerged face this is 57 of the estimated total ice loss at the terminus calving plus melting at this time submarine melting may thusprovidea significantcontributiontotheoverallablationofatidewaterglacier oceano graphic measurements conductivity temperature depth made 200 500m from the ter minus identified an isohaline 27ppt and isothermal 7 2 c layer extending from 130m depthto the fjord floor capping this is a 40mthick overflow plume distinguishedby high outflow rates low salinity 22 25ppt and lower temperatures 5 6 c mixing models indicate that fresh water comprised about11 of this plume it originates mostly as sub glacial discharge whose buoyancy drives convection at the terminus deep warm saline watersareincorporatedintotheplumeasitascends causingsubstantialmeltingoficealong the submarine face the calving terminus undergoes seasonal changes that coincide with changes in subglacial discharge and fjord water temperatures and we suggest that these fluctuations interminuspositionare directly relatedto changes in submarine melting

ice front variations and speed changes of calving glaciers in the southern patagonia icefield from 1984 to 2011 patagonian icefields are losing volume and their loss is due partly to rapid changes in their outlet glaciers that terminate in lakes or the ocean despite this key influence from outlet glaciers relatively few of these calving glaciers have had high frequency measurements on their frontal variations and ice speed changes we describe here recent frontal variations and ice speed changes of all 28 major calving glaciers in the southern patagonia icefield spi including ice speed maps covering approximately half of the entire icefield the analysis is based on satellite data from 1984 to 2011 over this period only the two termini of glaciar pio xi advanced of the remaining glacial fronts 12 changed less than 0 5 km but 17 retreated at least 0 5 km in the latter group three glacial fronts glaciar jorge montt hps12 and upsala retreated over 6 km averaged over all 31 glacial fronts of the calving glaciers the front positions retreated 1 56 km median is 0 71 km along the flowline within 20 km of the front the ice speeds up to 5900 200 m a 1 except for regions showing large acceleration or deceleration the mean speed over the measured area decreased by 30 m a 1 from 1984 to 2011 the three most rapidly retreating glaciers showed much larger acceleration near the calving front suggesting that ice dynamics drive their rapid retreat thus we see retreat as a long term trend for the calving glaciers in the spi with behavior that implies a dynamically controlled rapid recession that may explain the recently reported volume change of the spi

major lunar crustal terranes surface expressions and crust mantle origins in light of global remotely sensed data the igneous crust of the moon can no longer be viewed as a simple globally stratified cumulus structure composed of a flotation upper crust of anorthosite underlain by progressively more mafic rocks and a residual melt kreep sandwich horizon near the base of the lower crust instead global geochemical information derived from clementine multispectral data and lunar prospector gamma ray data reveals at least three distinct provinces whose geochemistry and petrologic history make them geologically unique 1 the procellarum kreep terrane pkt 2 the feldspathic high lands terrane fht and 3 the south pole aitken terrane spat the pkt is a mafic province coincident with the largely resurfaced area in the procellarum imbrium region whose petrogenesis relates to the early differentiation of the moon here some 40 of the th in the moon s crust is concentrated into a region that constitutes only about 10 of the crustal volume this concentration of th average 5 ppm and by implication the other heat producing elements u and k led to a fundamentally different thermal and igneous evolution within this region compared to other parts of the lunar crust lower crustal materials within the pkt likely interacted with underlying mantle materials to produce hybrid magmatism leading to the magnesian suite of lunar rocks and possibly kreep basalt although rare in the apollo sample collection widespread mare volcanic rocks having substantial th enrichment are indicated by the remote data and may reflect further interaction between enriched crustal residues and mantle sources the fht is characterized by a central anorthositic region that constitutes the remnant of an anorthositic craton resulting from early lunar differentiation basin impacts into this region do not excavate significantly more mafic material suggesting a thickness of tens of kilometers of anorthositic crust the feldspathic lunar meteorites may represent samples from the anorthositic central region of the fht ejecta from deep penetrating basin impacts outside of the central anorthositic region however indicate an increasingly mafic composition with depth the spat a mafic anomaly of great magnitude may include material of the upper mantle as well as lower crust thus it is designated a separate terrane whether the spa basin impact simply uncovered lower crust such as we infer for the fht remains to be determined

distributed subglacial discharge drives significant submarine melt at a greenland tidewater glacier this is the publisher s final pdf the article is copyrighted by american geophysical union and published by john wiley sons inc it can be found at http agupubs onlinelibrary wiley com agu journal 10 1002 28issn 291944 8007

the effect of meltwater plumes on the melting of a vertical glacier face abstractfreshwater produced by the surface melting of ice sheets is commonly discharged into ocean fjords from the bottom of deep fjord terminating glaciers the discharge of the freshwater forms upwelling plumes in front of the glacier calving face this study simulates the meltwater plumes emanated into an unstratified environment using a nonhydrostatic ocean model with an unstructured mesh and subgrid scale mixing calibrated by comparison to established plume theory the presence of an ice face reduces the entrainment of seawater into the meltwater plumes so the plumes remain attached to the ice front in contrast to previous simple models ice melting increases with height above the discharge also in contrast to some simple models and the authors speculate that this overcutting may contribute to the tendency of icebergs to topple inwards toward the ice face upon calving the overall melt rate is found to increase with discharge flux only up to a critical value which depends on the channel size

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

ice loss from the southern patagonian ice field south america between 2000 and 2012 1 a time series composed of 156 aster derived digital elevation models dems and a radar penetration bias corrected version of the shuttle radar topography mission srtm dem is used to derive ice surface height and volume changes at the southern patagonian ice field spi in southern south america the observations made between february 2000 and march 2012 indicate that the ice field is rapidly losing volume at many of the largest outlet glaciers and in most cases thinning extends to the highest elevations of the ice field mass loss is occurring at a rate of 20 0 1 2 gt a 1 which when summed with mass loss at the adjacent northern patagonian ice field results in a combined rate of 24 4 1 4 gt a 1 equivalent to 0 067 0 004 mm a 1of sea level rise our decade long mass loss rates are substantially higher than those derived during the last three decades of the 20th century but are in good agreement with recent grace observations our volume loss estimate is sensitive to constraints applied to the amount of thickening in the accumulation zone new field measurements and a continued dem time series will be required to refine our estimates

concentrations of radioactive elements in lunar materials as an aid to interpreting data obtained remotely on the distribution of radioactive elements on the lunar surface average concentrations of k u and th as well as al fe and ti in different types of lunar rocks and soils are tabulated the u th ratio in representative samples of lunar rocks and regolith is constant at 0 27 k th ratios are more variable because k and th are carried by different mineral phases in nonmare regoliths at the apollo sites the main carriers of radioactive elements are mafic i e 6 8 fe impact melt breccias created at the time of basin formation and products derived therefrom

convection driven melting near the grounding lines of ice shelves and tidewater glaciers subglacial meltwater draining along the bed of fast flowing marine terminating glaciers emerges at the groundingline wheretheiceeithergoesafloattoformaniceshelforterminates inacalvingface theinputof freshwater to the ocean provides a source of buoyancy and drives convective motion alongside the ice ocean interface this process is modeled using the theory of buoyant plumes that has previously been applied to the study of the larger scale circulation beneath ice shelves the plume grows through entrainment of ocean waters and the heat brought into the plume as a result drives melting at the ice ocean interface the equations are nondimensionalized by using scales appropriate for the region where the subglacial drainage rather than the subsequent addition of meltwater supplies the majority of the buoyancy forcing it is found that the melt rate within this region can be approximated reasonably well by a function that is linear in ocean temperature has a cube root dependence on the flux of subglacial meltwater and has a complex dependency on the slope of the ice ocean interface the model is used to investigate variability in melting induced by changes in both ocean temperature and subglacial discharge for a number of realistic examples of ice shelves and tidewater glaciers the results show how warming ocean waters and increasing subglacial drainage both generate increases in melting near the grounding line

modeling turbulent subglacial meltwater plumes implications for fjord scale buoyancy driven circulation abstractfjord scale circulation forced by rising turbulent plumes of subglacial meltwater has been identified as one possible mechanism of oceanic heat transfer to marine terminating outlet glaciers this study uses buoyant plume theory and a nonhydrostatic three dimensional ocean ice model of a typical outlet glacier fjord in west greenland to investigate the sensitivity of meltwater plume dynamics and fjord scale circulation to subglacial discharge rates ambient stratification turbulent diffusivity and subglacial conduit geometry the terminal level of a rising plume depends on the cumulative turbulent entrainment and ambient stratification plumes with large vertical velocities penetrate to the free surface near the ice face however midcolumn stratification maxima create a barrier that can trap plumes at depth as they flow downstream subglacial discharge is varied from 1 750 m3 s 1 large discharges result in plumes with positive temperature and salinity anomalies in the upper water column for

major compositional units of the moon lunar prospector thermal and fast neutrons global maps of thermal and fast neutron fluxes from the moon suggest three end member compositional units a high thermal and low fast neutron flux unit correlates with the lunar highlands and is consistent with feldspathic rocks the south pole aitken basin and a strip that surrounds the nearside maria have intermediate thermal and fast neutron flux levels consistent with more mafic rocks there appears to be a smooth transition between the most mafic and feldspathic compositions which correspond to low and high surface altitudes respectively the maria show low thermal and high fast neutron fluxes consistent with basaltic rocks

ocean forcing of glacier retreat in the western antarctic peninsula in recent decades hundreds of glaciers draining the antarctic peninsula 63 to 70 s have undergone systematic and progressive change these changes are widely attributed to rapid increases in regional surface air temperature but it is now clear that this cannot be the sole driver here we identify a strong correspondence between mid depth ocean temperatures and glacier front changes along the 1000 kilometer western coastline in the south glaciers that terminate in warm circumpolar deep water have undergone considerable retreat whereas those in the far northwest which terminate in cooler waters have not furthermore a mid ocean warming since the 1990s in the south is coincident with widespread acceleration of glacier retreat we conclude that changes in ocean induced melting are the primary cause of retreat for glaciers in this region

contribution of the patagonia icefields of south america to sea level rise digital elevation models of the northern and southern patagonia icefields of south america generated from the 2000 shuttle radar topography mission were compared with earlier cartography to estimate the volume change of the largest 63 glaciers during the period 1968 1975 2000 these glaciers lost ice at a rate equivalent to a sea level rise of 0 042 0 002 millimeters per year in the more recent years 1995 2000 average ice thinning rates have more than doubled to an equivalent sea level rise of 0 105 0 011 millimeters per year the glaciers are thinning more quickly than can be explained by warmer air temperatures and decreased precipitation and their contribution to sea level per unit area is larger than that of alaska glaciers

near glacier surveying of a subglacial discharge plume implications for plume parameterizations at tidewater glaciers plume dynamics affect submarine melting fjord circulation and the mixing of meltwater models often rely on buoyant plume theory to parameterize plumes and submarine melting however these parameterizations are largely untested due to a dearth of near glacier measurements here we present a high resolution ocean survey by ship and remotely operated boat near the terminus of kangerlussuup sermia in west greenland these novel observations reveal the 3d structure and transport of a near surface plume originating at a large undercut conduit in the glacier terminus that is inconsistent with axisymmetric plume theory the most common representation of plumes in ocean glacier models instead the observations suggest a wider upwelling plume a truncated line plume of 200 m width with higher entrainment and plume driven melt compared to the typical axisymmetric representation our results highlight the importance of a subglacial outlet s geometry in controlling plume dynamics with implications for parameterizing the exchange flow and submarine melt in glacial fjord models

the impact of melting ice on ocean waters abstract ice melts when it is in contact with ocean waters that have temperatures above the in situ freezing point the product is a mixture of meltwater and seawater having properties intermediate between those of the two components density is one of the properties that is affected and this has important implications for how the melt induced changes are eventually manifested although the direct impact of melting is to cool and dilute the ocean subsequent convection can carry the products of melting to parts of the water column where they are comparatively warm and salty these principles are illustrated with a set of observations from the continental shelf of the amundsen sea measurements made near a floating glacier are used to calculate the concentration of meltwater in the water column concentrations approaching 2 are associated with comparatively high temperatures low dissolved oxygen concentrations and negligible stable isotope anomalies the impact of drifting icebergs on the southern ocea

integration of the clementine uv vis spectral reflectance data and the lunar prospector gamma ray spectrometer data a global scale multielement analysis of the lunar surface using iron titanium and thorium abundances 1 we present a statistical analysis based on a systematic clustering method of a data set integrating the global abundances maps of iron titanium and thorium derived from clementine and lunar prospector homogeneous geological units are compositionally characterized and spatially defined in relation to the major rock types sampled on the moon with the lowest abundances in fe ti and th found on the moon the lunar highlands terrains are quite homogeneous with two major large feldspathic units one being slightly more mafic than the other two distinct regions with unique compositions are unambiguously identified the procellarum kreep terrane pkt and the south pole aitken spa the pkt which includes all the units with th abundances higher than 3 5 ppm kreep rich materials is delimited by an almost continuous ring like unit in particular it includes the western nearside maria except for mare humorum within the pkt a th rich unit corresponding to the highest th concentrations found on the moon may represent kreep volcanic deposits excavated from relatively shallow depth with concentrations in fe ti and th enhanced relative to the surrounding highlands the south pole aitken basin floor represents a large mafic anomaly on the farside suggesting wide deposits of lower crust and possible mantle materials however due to indirect residual latitude effects in the clementine spectral reflectance measurements iron abundances might have been overestimated in spa thus implying that crustal materials rather than mantle materials might represent the dominant contributor to the mafic component exposed on the basin floor

paleoenvironmental changes since 3000 bc in the coastal marsh of vravron attica se greece abstract the coastal area of the vravron bay in the vicinity of the homonym archaeological site is a marshy plain located on the eastern part of the attica peninsula eastern greece in order to provide evidence for palaeoenvironmental changes and landscape evolution of the area detailed micropaleontological palynological and sedimentological analyses have been conducted at the underlying late holocene coastal deposits the recovered sediments lithostratigraphic units a d represent a continuous record of the environmental history of the area since the early bronze age covering all subsequent historical periods the base of the recovered deposits is older than the 3rd millennium bc until late medieval times the studied sequence contains plenty evidence for the existence of the natural port reported from the mycenaean lithostratigraphic unit a that infilled after repeated flooding events during the classic period lithostratigraphic unit b and gradually developed into a shallower marine environment lithostratigraphic unit c in the uppermost part of the sequence lithostratigraphic unit d a transition towards brackish environment with intense fresh water input is featured around 1540 ad signs of human agricultural activities in vravron appear since 3000 bc early bronze age and are linked to the history of inhabitation in the area

does calving matter evidence for significant submarine melt abstract during the summer in the northeast pacific ocean the alaska coastal current sweeps water with temperatures in excess of 12 c past the mouths of glacierized fjords and bays the extent to which these warm waters affect the mass balance of alaskan tidewater glaciers is uncertain here we report hydrographic measurements made within icy bay alaska and calculate rates of submarine melt at yahtse glacier a tidewater glacier terminating in icy bay we find strongly stratified water properties consistent with estuarine circulation and evidence that warm gulf of alaska water reaches the head of 40 km long icy bay largely unaltered a 10 20 m layer of cold fresh glacially modified water overlies warm saline water the saline water is observed to reach up to 10 4 c within 1 5 km of the terminus of yahtse glacier by quantifying the heat and salt deficit within the glacially modified water we place bounds on the rate of submarine melt the submarine melt rate is estimated at 9 m d 1 at least half the rate at which ice flows into the terminus region and can plausibly account for all of the submarine terminus mass loss our measurements suggest that summer and fall subaerial calving is a direct response to thermal undercutting of the terminus further demonstrating the critical role of the ocean in modulating tidewater glacier dynamics

ice motion of the patagonian icefields of south america 1984 2014 2015 american geophysical union all rights reserved we present the first comprehensive high resolution mosaic of ice velocity of the northern npi and southern patagonian icefields spi from multiple synthetic aperture radar and optical data collected between 1984 and 2014 the results reveal that many of the outlet glaciers extend far into the central ice plateaus which implies that changes in ice dynamics propagate far inside the accumulation area we report pronounced seasonal to interannual variability of ice motion on pio xi and jorge montt a doubling in speed of jorge montt a major slow down of o higgins significant fluctuations of upsala and a deceleration of san rafael which illustrate the need for sustained continuous time series of ice motion to understand the long term evolution of the rapidly thinning icefields the velocity product also resolves major ambiguities in glacier drainage in areas of relatively flat topography illustrating the need to combine topography and flow direction to map drainage basins

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

recent ice dynamics and mass balance of jorge montt glacier southern patagonia icefield the southern patagonia icefield spi withdrawal in recent decades shows contrasting behaviours between adjacent basins one of the basins with highest volumetric losses is located at northernmost spi we refer to jorge montt tidewater glacier 48 30 s 73 30 w 445 km 2 in 2018 which retreated 2 7 km between 2011 and 2018 and thinned at rates of up to 21 m a 1 over this period based on the retreat record remote sensing imagery field data a mass balance model and a calving parameterisation we attempted to differentiate climatic induced changes i e surface mass balance and dynamic responses i e calving fluxes the surface mass balance reached 4 15 km 3 w e a 1 between 2012 and 2017 when frontal ablation is included the net mass balance is 17 79 km 3 w e a 1 this represents a change of trend compared with modelling estimations of positive surface mass balance prior to 2010 this shift is attributed to higher ablation rates given that accumulation is known to have increased between 1980 and 2015 the available evidence therefore indicates that frontal ablation is the main factor supported by observed rates at jorge montt as high as 3 81 km 3 w e a 1 in 2015 with ice velocities peaking at 11 km a 1

late postglacial paleoenvironmental change in the northeastern mediterranean region combined palynological and molecular biomarker evidence three gravity cores collected from the ne mediterranean nemr across a transect from the northern aegean sea north skyros basin to the south cretan margin scm were investigated for pollen and terrestrial biomarkers derived from epicuticular waxes of vascular plants during the last 20 ky pollen data show diversified mixed temperate forest in the northern borderlands and enhanced mediterranean vegetation in the southern areas documenting an n s climatic trend terrestrial plant biomarkers and their diagnostic geochemical indices exhibit latitudinal patterns which are interpreted in terms of the different delivery pathways fluvial runoff vs atmospheric transport resulting from the climate conditions during different periods during the late glacial and early deglaciation periods 20 14 ka bp relatively increased humidity h index is recorded in the north aegean sea while in the south drier climate was the limiting factor for vegetation development during this interval terrestrial n alkanes showed increased accumulation rates suggesting massive transport of terrestrial organic matter through runoffs and rivers followed by weaker input after 14 ka bp after 11 ka bp a major expansion of forest cover is evidenced in the nemr accompanied by a higher h index because of the climatic amelioration the forest vegetation exhibited regionally different characteristics with cool temperate taxa being more abundant in the aegean cores while the scm record is being featured by mediterranean elements at the onset of the holocene and throughout the holocene climatic optimum the delivery of terrestrial biomarkers increased and became more significant in the aegean sites compared to the scm site within the holocene the average chain length acl of long chain n alkanes exhibits lower values in the northern aegean than in the southeastern aegean and scm indicating the predominance of warmer species southwards finally the h index records a conspicuous humidity increase between 5 4 and 4 3 ka bp in the south aegean that coincides with an increase in the terrestrial biomarker supply and the deposition of a distinct sapropel like layer smh sapropel mid holocene similar trends in t temperature and h indices are slightly delayed and attenuated in the northern aegean and are accompanied by an increase in the acl index a noticeable increase in the accumulation rates ars of terrestrial biomarkers and the hpa index values during this period are clearly recorded in all three cores indicative of enhanced terrigenous inputs of organic matter along with higher in situ preservation

subglacial discharge driven renewal of tidewater glacier fjords the classic model of fjord renewal is complicated by tidewater glacier fjords where submarine melt and subglacial discharge provide substantial buoyancy forcing at depth here we use a suite of idealized high resolution numerical ocean simulations to investigate how fjord circulation driven by subglacial plumes tides and wind stress depends on fjord width grounding line depth and sill height we find that the depth of the grounding line compared to the sill is a primary control on plume driven renewal of basin waters in wide fjords the plume exhibits strong lateral recirculation increasing the dilution and residence time of glacially modified waters rapid drawdown of basin waters by the subglacial plume in narrow fjords allows for shelf waters to cascade deep into the basin wide fjords result in a thin boundary current of shelf waters that flow toward the terminus slightly below sill depth wind forcing amplifies the plume driven exchange flow however wind induced vertical mixing is limited to near surface waters tidal mixing over the sill increases in fjord transport of deep shelf waters and erodes basin stratification above the sill depth these results underscore the first order importances of fjord glacier geometry in controlling circulation in tidewater glacier fjords and thus ocean heat transport to the ice

mapping the feo and tio2 content of the lunar surface with multispectral imagery the derivation of quantitative elemental concentrations from multispectral imaging of the moon has long been a goal of lunar remote sensing concentration maps at the spatial resolutions available from the recent clementine mission would provide a revolutionary new tool for understanding the origin and evolution of the lunar crust lucey et al 1995 presented a method for extracting the concentration of fe from multispectral imaging of the moon this paper examines and quantifies important aspects ofthat technique left unexamined by lucey et al which had the potential to severely limit its utility these aspects include the effects of maturity grain size mineralogy shading due to topography and the presence of glass we also present a new algorithm for derivation of tio2 from multispectral imaging of both mare and highland units we find that both techniques are only weakly sensitive to maturity and that they have about 1 wt accuracy based on examination of the spectral properties and compositions of resolved lunar sampling stations presented by blewett et al 1997 we also discuss these findings in the context of two contrasting views of the effect of composition on lunar spectral properties presented by pieters and coworkers and hapke and coworkers we find the view of hapke and coworkers to be more consistent with our observations using a global mosaic of clementine multispectral data and these element derivation algorithms we find that the global modal abundance of feo is 4 5 wt 1 wt and the global modal abundance of tio2 is 0 45 wt 1 wt

iceberg meltwater fluxes dominate the freshwater budget in greenland s iceberg congested glacial fjords freshwater fluxes from the greenland ice sheet have increased over the last two decades due to increases in liquid i e surface and submarine meltwater and solid ice i e iceberg fluxes to predict potential ice sheet ocean climate feedbacks we must know the partitioning of freshwater fluxes from greenland including the conversion of icebergs to liquid i e meltwater fluxes within glacial fjords here we use repeat 0 5 m resolution satellite images from two major fjords to provide the first observation based estimates of the meltwater flux from the dense matrix of floating ice called melange we find that because of its expansive submerged area 100 km2 and rapid melt rate 0 1 0 8 m d 1 the ice melange meltwater flux can exceed that from glacier surface and submarine melting our findings suggest that iceberg melt within the fjords must be taken into account in studies of glacial fjord circulation and the impact of greenland melt on the ocean

thermal constraints on the frictional conditions of the nucleation and rupture area of the 1992 nicaragua tsunami earthquake summary the 1992 nicaragua earthquake was a tsunami earthquake which generated tsunamis disproportionately large for its surface wave magnitude ms 7 2 seismological studies and tsunami simulation indicated that the event was a slow earthquake which occurred on the plate boundary between the subducting cocos plate and the overriding caribbean plate we present a finite element model that enables us to estimate for the first time the temperature and inferred frictional conditions in the rupture area of a tsunami earthquake direct and indirect observations are used to constrain all model parameters and surface heat flux measurements provide independent information to verify the model results furthermore we used a genetic algorithm to perform a sensitivity analysis of all model parameters and to define the spatial range of thermally defined updip limit of the seismogenic zone the earthquake nucleated in the seismogenic zone at temperatures of 150 c and propagated updip towards the trench axis the centroid or centre of mass of moment release was located in a region characterized by temperatures of 50 c thus the rupture propagated through a region where plate motion is normally accommodated by aseismic creep our observations support a model in which tsunami earthquakes nucleate in the seismogenic zone near its updip limit however in such an environment coupled asperities are perhaps too small to cause large earthquakes seamounts however are abundant on the incoming cocos plate therefore in addition to temperature dependent metamorphic induration of sediments increased normal stress by seamount subduction may contribute to accumulate stress sufficiently large to release enough energy near the updip limit of the seismogenic zone to promote dynamic slip along a

relative sea level change and postglacial isostatic adjustment along the coast of south devon united kingdom previous sea level studies suggest that southwest britain has the fastest subsiding coastline in the united kingdom but tide gauge data gps and gravity measurements and geophysical models show little evidence of anomalous subsidence in this region in this paper we present 15 new sea level index points from four coastal barrier systems in south devon eight are from compaction free basal sediments and others were corrected for autocompaction our data suggest that relative sea level along the south devon coastline has risen by 21 4 m during the past 9000 years sea level rise slowed during the middle and late holocene and a rise of 8 1 m has occurred since ca 7000 cal yr bp anomalous ages for many rejected points are attributed to sediment reworking during barrier transgression the relative sea level history during the early and middle holocene shows a good fit with geophysical model predictions but the geological and modelled data diverge in the later holocene unlike the geophysical models sea level index points cannot differentiate between late holocene relative sea level histories of south devon and southwest cornwall it is suggested that this discrepancy can be resolved by obtaining additional high quality sea level index points covering the past 4000 years copyright 2008 john wiley sons ltd

glaciar jorge montt chilean patagonia dynamics derived from photos obtained by fixed cameras and satellite image feature tracking tidewater calving glaciers can undergo large fluctuations not necessarily in direct response to climate but rather owing to complex ice water interactions at the glacier termini one example of this process in chilean patagonia is glaciar jorge montt where two cameras were installed in february 2010 collecting up to four glacier photographs per day until they were recovered on 22 january 2011 ice velocities were derived from feature tracking of the geo referenced photos yielding a mean value of 13 4md 1 for the whole lower part of the glacier these velocities were compared to satellite imagery derived feature tracking obtained in february 2010 resulting in similar values during the operational period of the cameras the glacier continued to retreat 1 km experiencing one of the highest calving fluxes ever recorded in patagonia 2 4 km 3 a 1 comparison with previous data also revealed ice acceleration in recent years these very high velocities are clearly a response to enhanced glacier calving activity into a deep water fjord

viscoelastic evolution of lunar multiring basins 1 we investigate the evolution of multiring basins on the moon the orbital geophysical and geochemical data collected by lunar prospector allow three distinct groups of basins to be identified group 1 basins show well preserved topography a bull s eye gravity signature and little mare basalt fill group 2 basins contain large amounts of mare basalt and show mare dominated gravity and topography signatures group 3 basins are characterized by low amplitude topographic relief and weak gravity anomalies while the crustal structures of group 1 and 2 basins appear to date from the collapse of the transient cavity group 3 basins are highly degraded and show very little crustal thinning using a viscoelastic model we explore the evolution of the lunar multiring basins with the goal of explaining the degraded condition of group 3 basins our results show that while viscous relaxation is a plausible explanation for the state of group 3 farside basins requiring heat flux 25 40 mw m 2 the thin nearside crust renders subsolidus ductile flow in the crust unlikely the existence of many degraded basins on the nearside points to a weakened and possibly partially molten lower crust that south pole aitken appears not to have relaxed suggests that similar conditions did not exist there and that the nearside was hotter than the farside early on this is likely a consequence of the nearside farside crustal thickness dichotomy which would have caused the farside to reach full crystallization first leaving the nearside with the remaining liquid and an excess of heat producing elements

the holocene sea level story since 7500 bp lessons from the eastern mediterranean the black and the azov seas abstract this paper addresses the obvious controversy between the so far published sea level curves of the black sea and the mediterranean it starts with a discussion of the methods of reconstructing sea level curves the evaluation of sea level indicators and the application of the radiocarbon dating method at least since 7500 bp when the black sea and the mediterranean were connected both water bodies must have reacted synchronously on glacio eustatic changes it is documented that none of the mediterranean sea level curves shows the major wiggles postulated for the black sea which are supposed to reflect trans and regression cycles the very shallow bathymetric condition of the azov sea and the northern black sea should have led to considerable and traceable shoreline displacements there is neither archaeological nor historical evidence of mid and late holocene regressions of several meters the tectonic setting of the black and azov seas implicates that the tectonic signal often overrides the eustatic one therefore only local sea level curves can be established in this paper based on vibracores a locally valid sea level curve for the taman peninsula is demonstrated layers of paralic peat were used as sea level indicators and for 14 c dating the shape of this curve follows the one known from the mediterranean this study also revealed that the present peninsula of taman evolved out of a former archipelago

columbia bay alaska an upside down estuary abstract circulation and water properties within columbia bay alaska are dominated by the effects of columbia glacier at the head of the bay the basin between the glacier terminus and the terminal moraine sill depth of about 22 m responds as an upside down estuary with the subglacial discharge of freshwater entering at the bottom of the basin the intense vertical mixing caused by the bouyant plume of freshwater creates a homogeneous water mass that exchanges with the far field water through either a two or a three layer flow in general the glacier acts as a large heat sink and creates a water mass which is cooler than that in fjords without tidewater glaciers the predicted retreat of columbia glacier would create a 40 km long fjord that has characteristics in common with other fjords in prince william sound

ice thickness of the northern half of the patagonia icefields of south america from high resolution airborne gravity surveys author s gourlet p rignot e rivera a casassa g abstract 2015 american geophysical union all rights reserved we employ high resolution high precision helicopter borne gravity observations of the northern npi and southern patagonia icefields spi south america to infer ice thickness and bed topography using a three dimensional model constrained by fjord and lake bathymetry and a land ice mask the results reveal thicker ice than the reflecting horizon of radar sounders with 1 km deep ice for glaciar san rafael and colonia npi and 1 5 km deep ice for glaciar occidental spi these bedrock troughs channelize fast motion of ice from the plateaus combining ice motion and thickness we calculate balance accumulation levels of 3 6 m yr water equivalent for the plateaus bed elevation remains below sea lake level 15 20 km inland for jorge montt and o higgins which favors retreat and is at sea level for san rafael which halted its retreat the results demonstrate the utility of airborne gravity surveys for providing critical data on ice volume bed elevation and balance accumulation of temperate ice masses

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

a simple model of the ice shelf ocean boundary layer and current abstractocean forced basal melting has been implicated in the widespread thinning of antarctic ice shelves but an understanding of what determines melt rates is hampered by limited knowledge of the buoyancy and frictionally controlled flows along the ice shelf base that regulate heat transfer from ocean to ice in an attempt to address this deficiency a simple model of a buoyant boundary flow considering only the spatial dimension perpendicular to the boundary is presented results indicate that two possible flow regimes exist a weakly stratified geostrophic cross slope current with upslope flow within a buoyant ekman layer or a strongly stratified upslope current with a weak cross slope flow the latter regime which is analogous to the steady solution for a katabatic wind is most appropriate when the ice ocean interface is steep for the gentle slopes typical of antarctic ice shelves the buoyant ekman regime which has similarities with the case of an unstratified density current on a slope p

lunar rare earth element distribution and ramifications for feo and tio2 lunar prospector neutron spectrometer observations lunar prospector neutron spectrometer data have been used to map the global surface distribution of the incompatible rare earth elements gadolinium and samarium from the low altitude 30 15 km mapping orbit these results afford improved surface resolution and detailed views of the potassium rare earth elements and phosphorus kreep distribution within and around mare imbrium and elsewhere the gd and sm results serve as a complementary and independent check of the distribution of kreep on the moon in contrast with the lunar prospector gamma ray spectrometer results for thorium the neutron spectrometer observations reflect the presence of fe and ti as well as gd and sm the contributions of fe and ti are removed using high spatial resolution clementine spectral reflectance determinations of feo and tio2 abundances overall the resulting gd and sm abundance map agrees with the th abundance map determined using the lunar prospector gamma ray spectrometer in general the detailed features of the procellarum imbrium kreep terrane are found in both for example distinct highs in gd sm and th abundances are resolved over the craters mairan aristarchus kepler reinhold lalande and aristillus over the apennine bench and fra mauro regions and over the montes jura and montes carpatus indicating an enhanced abundance of kreep in these locations the neutron observations also provide constraints on feo and tio2 abundances for some high ti locales there is a significant disagreement with tio2 abundances inferred from clementine spectral reflectance

organic geochemical evidence of late glacial holocene climate instability in the north aegean sea sedimentary molecular biomarker compositions organic carbon and caco3 concentrations and bulk organic 13c and total 15n values document a series of paleoclimatic changes that have affected organic matter production and sedimentation in the north aegean sea from the termination of the latest glacial maximum through the middle holocene continental environmental conditions have been inferred from land plant biomarkers paleoproductivity patterns of diatoms prymnesiophytes dinoflagellates and nannoplankton were discerned from marine derived biomarkers although organic matter is predominantly marine variations in the proportion of marine and land contributions and in its general preservation are evident rapid changes in the eastern mediterranean thermohaline circulation evidently occurred in parallel to sea surface temperature oscillations enhanced deep water ventilation accompanied cold intervals in the late last glacial the younger dryas and during an interruption of deposition of the s1 sapropel probably in response to strengthening of north winds over the region in contrast decreased thermohaline circulation occurred during the warm interval associated with the s1 sapropel during this period increased freshwater inputs diminished ventilation of deep water masses and enhanced organic matter production and preservation intriguing fluctuations in sea surface temperatures and the concentrations of marine and terrestrial biomarkers within the sapropelic layer most prominently in the interruption from 8 2 to 7 8 calibrated radiocarbon conventional kyr bp support the hypothesis that several distinct events of deep water reoxygenation occurred in the north aegean sea during deposition of the s1 sapropel these events reflect centennial excursions to the more common low productivity and well ventilated conditions of the mediterranean that may possibly be related to north atlantic oscillation cycles

small area thorium features on the lunar surface 1 using an improved understanding of the lunar prospector gamma ray spectrometer lp grs spatial footprint we have derived a new map of global thorium abundances on the lunar surface this map has a full width half maximum spatial resolution of 80 km 2 and is mapped on the lunar surface using 0 5 0 5 pixels this map has allowed the identification and classification of 42 small area 3 g g in southwestern mare tranquillitatis near the apollo 11 landing site with our better understanding of the lp grs spatial footprint we have been able to constrain the surface thorium abundance at the compton belkovich thorium anomaly to 40 55 g g which is higher than any other measured location on the lunar surface and higher than most samples finally using 1 km pixel feo abundances from clementine and lp grs spatial footprint information we have been able to obtain plausible thorium distributions around kepler crater at a resolution of 1 km pixel the materials around kepler crater appear to be a relatively simple mixing of thorium rich mib compositions and high thorium mare basalts

thorium abundances on the lunar surface measurements of absolute thorium abundances on the lunar surface are presented using both the high and low altitude data taken with the lunar prospector gamma ray spectrometer an analysis of the uncertainties shows that the measured uncertainties are 7 g g are likely small area regions 150 km 2 using lunar topographic data we have shown that the thorium abundances in the lunar high lands and portions of south pole aitken spa basin are larger for lower elevations we have also studied a number of regions with anomalously high thorium abundances such as the northwestern region of spa basin the crater arago in western tranquillitatis and the compton belkovich region in the northeastern highlands the compton belkovich region appears to be enriched with evolved rocks such as alkali anorthosite and currently represents the only such extended region on the moon that has been identified in contrast tycho crater has very low thorium abundances which suggests that kreep was not assimilated at depth in this portion of the moon

the great lunar hot spot and the composition and origin of the apollo mafic lkfm impact melt breccias thorium rich mafic impact melt breccias from the apollo 14 17 missions that is those breccias identified with the composition known as lkfm are regarded largely as products of basin forming impacts that penetrated the feldspathic crust and sampled underlying mafic material and magma ocean residuum carrying the compositional signature of kreep potassium rare earth elements phosphorous despite considerable compositional variation among such breccias compositions of all of them correspond to mixtures of only four components 1 a norite with composition generally similar to that of apollo 15 basalt mean abundance 58 range 30 95 2 fo 90 dunite mean 13 range 1 27 3 feldspathic upper crust mean 29 range 4 50 and feni metal 0 1 1 7 petrographic evidence has shown that much of the feldspathic component but none of the kreep component is clastic this observation and the high proportion of kreep norite component in the breccias suggest that the melt zone of the impact or impacts forming the breccias contained little feldspathic material but consisted predominantly of material with the average composition of kreep norite the dunite component probably derives ultimately from the upper mantle these conclusions support the hypothesis that the breccias were not formed in typical feldspathic crust but instead by one or more impacts into what is designated here the great lunar hot spot that is the anomalous th rich terrane in the imbrium procellarum area identified by the apollo and lunar prospector gamma ray spectrometers the lkfm composition is a special product of the great lunar hot spot and is not the average composition of the lower crust in typical feldspathic highlands similarly mg suite and alkali suite plutonic rocks of the apollo collection are likely all differentiation products of the hot spot not of plutons that might occur in typical feldspathic crust

paleoenvironmental evolution and prehistoric human environment in the embayment of palamari skyros island greece during middle late holocene abstract palamari bay is located on the northeastern coast of skyros island sporades islands aegean sea at the northern edge of the bay a fortified prehistoric settlement is found dated between 2800 and 1700 bc early bronze age ii middle bronze age i detailed geomorphological mapping of the coastal alluvial plain and paleontological micropaleontological palynological sedimentological and micromorphological studies of the holocene coastal deposits have been conducted in order to reconstruct the palaeoenvironment and the landscape evolution of the broader area of palamari bay three main sedimentary units were recognized a b and c from oldest to youngest the lowermost sedimentary unit a deposited between before 7500 and 3500 cal bp consists of sediment deposited from high to moderate energy fresh water flows with some suspended load fallout in established water bodies the microfauna indicates a shallow fresh water environment however a tendency to oligohaline conditions was established gradually during the same period the palamari area was characterized by open mixed deciduous forests that gradually retreated as a possible consequence of the intensification of anthropic activity associated with the settlement of palamari indications of cultivating and grazing activities in the vicinity of the lagoon were identified pointing to a strong human presence since the neolithic between about 6000 and 3500 cal bp the embayment was a lagoon southeasterly connected to the sea therefore sheltered and protected from northeastern winds the overlying unit b ca 3500 800 cal bp is characterized by the dominance of brackish water microfauna indicating a brackish stagnant shallow water depositional environment which was periodically supplied with fresh water from the surrounding springs as the result of the continuous sea level rise during the late holocene part of the northern headland was submerged the decline of the palamari settlement at the time of the establishment of unit b might be related to the observed changes that rendered the embayment a restricted body of water the uppermost sedimentary unit c corresponds to a backshore environment dominated by aeolian activity modified by fluvial processes

palaeoenvironmental evolution and sea level changes in the coastal area of ne lemnos island greece during the holocene abstract the study area is located on the northeastern coast of lemnos island north aegean sea 40 2 30 n 25 00 00 e it covers the archaeological settlement of hephestia located in the purnia gulf and the coastal area of alyki lagoon reconstruction of the palaeogeography used palaeoenvironment data delivered from foraminifera and sea level changes providing archeological data about the presence of a potential harbour in the area geomorphological mapping as well as sedimentological and micropalaeontological studies of the holocene coastal deposits were conducted four boreholes were drilled from the alyki lagoon reaching 2 5 m to 11 m at the deepest and two from hephestia area reaching a depth of 6 m twenty four samples were dated using the ams radiocarbon method providing a chronology of the sedimentary units the calculated age from the boreholes provides dates from 7050 cal bp to 990 cal bp there was a constant sea level rise during the last 7000 cal bp in the study area results from the model of lambeck sea level curve and sea level index point from hephestia and alyki show a vertical difference of 0 5 1 5 m below sea level the foraminiferal fauna analysis shows the development of shallow marine conditions with fresh water influx during 7000 4000 cal bp and a temporary lagoon environment with fluctuations to shallow bay environment from 4000 to 990 cal bp

the imbrium impact event and the thorium distribution at the lunar highlands surface late in the moon s heavy bombardment period the impact that formed the imbrium basin excavated and melted a tremendous volume of material that was subsequently distributed over most of the moon s surface the apollo orbiting ray experiments metzger et al 1977 show that the imbrium projectile struck in a th rich area called the high th oval region here and regarded as a unique lunar geochemical province imbrium primary ejecta were thus probably rich in th it is shown here using ejecta deposit modeling that the distribution of th in the highlands surface along the ground tracks of the ray spectrometers is consistent with the distribution expected for imbrium ejecta deposits deep basins other than imbrium appear to have excavated regions of lower crust that were mafic and fe bearing but not th rich the possibility that the surface th distribution arises mainly from imbrium ejecta has implications for the nature of the moon s igneous differentiation and the nature of the proposed cataclysm or late bombardment with large meteoroids

multidecadal warming of antarctic waters decadal trends in the properties of seawater adjacent to antarctica are poorly known and the mechanisms responsible for such changes are uncertain antarctic ice sheet mass loss is largely driven by ice shelf basal melt which is influenced by ocean ice interactions and has been correlated with antarctic continental shelf bottom water asbw temperature we document the spatial distribution of long term large scale trends in temperature salinity and core depth over the antarctic continental shelf and slope warming at the seabed in the bellingshausen and amundsen seas is linked to increased heat content and to a shoaling of the mid depth temperature maximum over the continental slope allowing warmer saltier water greater access to the shelf in recent years regions of asbw warming are those exhibiting increased ice shelf melt

effect of a sheared flow on iceberg motion and melting icebergs account for approximately half the freshwater flux into the ocean from the greenland and antarctic ice sheets and play a major role in the distribution of meltwater into the ocean global climate models distribute this freshwater by parameterizing iceberg motion and melt but these parameterizations are presently informed by limited observations here we present a record of speed and draft for 90 icebergs from sermilik fjord southeastern greenland collected in conjunction with wind and ocean velocity data over an 8 month period it is shown that icebergs subject to strongly sheared flows predominantly move with the vertical average of the ocean currents if as typical in iceberg parameterizations only the surface ocean velocity is taken into account iceberg speed and basal melt may have errors in excess of 60 these results emphasize the need for parameterizations to consider ocean properties over the entire iceberg draft

lunar iron and titanium abundance algorithms based on final processing of clementine ultraviolet visible images the clementine mission to the moon returned global imaging data collected by the ultraviolet visible uvvis camera this data set is now in a final state of calibration and a five band multispectral digital image model dim of the lunar surface will soon be available to the science community we have used observations of the lunar sample return sites and stations extracted from the final dim in conjunction with compositional information for returned lunar soils to revise our previously published algorithms for the spectral determination of the feo and tio2 content of the lunar surface the algorithms successfully normalize the effects of space weathering so that composition may be determined without regard to a surface s state of maturity these algorithms permit anyone with access to the standard archived dim to construct high spatial resolution maps of feo and tio2 abundance such maps will be of great utility in a variety of lunar geologic studies

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

statistical analysis of thorium and fast neutron data at the lunar surface 1 a comparison is conducted between the remotely sensed abundances of thorium through gamma ray spectroscopy and major chemical elements through fast neutron spectroscopy on the lunar surface these are key elements in the investigation of lunar evolution correlations of variations of thorium abundance and fast neutron flux are analyzed on a spatial scale of 180 km through the construction of a covariance map this technique is an unbiased mathematical method for developing the borders of major formations such as the procellarum kreep terrane although thorium variations are positively correlated with those of the fast neutron flux over most of the lunar nearside several locations within the procellarum kreep terrane have negative correlations this anticorrelation may denote an emplacement for these materials by transport of impact ejecta furthermore analysis of these data reveals the presence of a distinctive structure in the northwest corner of oceanus procellarum marked by a ring of enhanced thorium this structure may be related to an ancient impact basin the confirmation of such a ring of thorium around the major basins inside procellarum kreep terrane would reinforce the hypothesis of the redistribution of thorium during impact from shallow depth

water masses and circulation in the central region of the eastern mediterranean eastern ionian south aegean and northwest levantine 1986 1987 in the framework of the major multinational coordinated poem ii 86 march april 1986 and poem v 87 september october 1987 cruises in the eastern mediterranean high resolution hydrographic ctd data were collected by r v aegaio in the eastern ionian sea south aegean sea and northwest levantine basin the intercalibrated data sets were analyzed objectively for an optimal estimation of the basin s circulation in two different seasons the analysis reveals a rather complex general circulation pattern consisting of basin sub basin and mesoscale features during both study periods the major results concern the advection of the modified atlantic water maw along its eastward route the spreading of the levantine intermediate water liw and its trapping by the eddy fields the interaction between the south aegean sea and the eastern mediterranean and the reverse circulation in the cretan sea during winter and summer from the hydrography and the dynamic height maps synthetic schemes show the main circulation features in the two seasons

detailed dynamic geometric and supraglacial moraine data for glaciar pio xi the only surge type glacier of the southern patagonia icefield chilean government through centers of excellence base financing program of comision nacional de investigacion y tecnologica de chile conicyt

wind driven modulation of warm water supply to a proglacial fjord jorge montt glacier patagonia projections of sea level rise due to ice loss from the land to the ocean have been hampered by a lack of understanding of the role the ocean is playing in glacier retreat including the processes that contribute to the supply of warm water to the ice ocean interface here shipboard moored and weather station data collected off jorge montt a rapidly retreating glacier in patagonia are analyzed to understand the influence of wind forcing during summer synoptic scale down fjord wind events enhance an estuarine like two layer flow increasing the inflow of oceanic deep water during up fjord wind events the inflow of deep water is significantly reduced and a three layer exchange flow develops overall along fjord wind forcing is shown to modulate the inflow of warm water to the fjord by a factor of 2 5 the results sug gest that local channelized winds can be an important process modulating warm water supply and melting of tidewater glaciers

on the seasonal freshwater stratification in the proximity of fast flowing tidewater outlet glaciers in a sub arctic sill fjord 1 the greenland ice sheet releases large amounts of freshwater into the fjords around greenland and many fjords are in direct contact with the ice sheet through tidewater outlet glaciers here we present the first seasonal hydrographic observations from the inner part of a sub arctic fjord relatively close to and within 4 50 km of a fast flowing tidewater outlet glacier this region is characterized by a dense glacial and sea ice cover freshwater from runoff subglacial freshwater sgfw discharge glacial and sea ice melt are observed above 50 90 m depth during summer sgfw and subsurface glacial melt mixed with ambient water are observed as a layered structure in the temperature profiles below the low saline summer surface layer 1 c intermediate water mass is a significant subsurface heat source for ice melt we analyze the temperature and salinity profiles observed in late summer with a thermodynamic mixing model and determine the total freshwater content in the layer below the summer surface layer to be between 5 and 11 the total freshwater contribution in this layer from melted glacial ice was estimated to be 1 2 while the corresponding sgfw was estimated to be 3 10 the winter measurements in the subsurface halocline layer showed a total freshwater content of about 1 and no significant contribution from sgfw

iron abundances on the lunar surface as measured by the lunar prospector gamma ray and neutron spectrometers i global measurements of iron abundances on the lunar surface are presented using data from the lunar prospector lp gamma ray spectrometer grs and neutron spectrometer ns in this study we derive relative iron abundances from the low altitude high spatial resolution 45 km 2 lp data using the 7 6 mev neutron capture gamma ray doublet as part of the lp grs analysis we demonstrate the importance of accounting for variations in neutron number density across the lunar surface by measuring neutron fluxes using lp ns data in a first step of comparing the lp grs data with previously published iron abundances inferred from clementine spectral reflectance csr data we show that the existing csr feo data are nonlinear with respect to the lp relative iron abundances we use the lp data to linearize the relationship between the csr and the relative iron values then recalibrate the csr data to iron abundance using returned soil abundances we then correlate the csr data except for major anomalies with the lp relative iron measurements to convert the lp data to absolute iron abundances when we compare the lp grs and revised csr data sets we find a very good correspondence there are two locations mare tranquillitatis and south pole aitken spa basin that show major discrepancies suggesting that the csr data are locally overestimating iron abundances in both these regions the discrepancies identified by the lp grs csr comparison are possibly explained by mineralogical differences that are not accounted for in the csr to feo calibration in regards to our understanding of the moon the lp data have found the following i there exist large expanses of mare basalt in the western mare regions that have very high iron abundances 22 23 wt feo that are underrepresented but not absent from the returned sample collection and are highly unusual for mare soils which typically contain a significant amount of highlands contamination 2 the low iron abundances in the lunar highlands 5 feo wt are consistent with a previous analysis using thermal and epithermal neutrons and with the idea that the lunar crust formed by a relatively simple magma ocean process 3 the comparison of lp and csr derived iron abundances suggests that the material within spa basin is similar to a norite type rock without an enriched mantle feo signature 4 a comparison of lp and csr data at tycho crater shows a large discrepancy such that the csr data show moderate iron abundances of 8 9 wt feo while the lp data show very low iron abundances of 3 4 wt feo this discrepancy cannot yet be easily explained by any known process