resolving mass flux at high spatial and temporal resolution using grace intersatellite measurements 1 the grace mission is designed to monitor mass flux on the earth s surface at one month and high spatial resolution through the estimation of monthly gravity fields although this approach has been largely successful information at submonthly time scales can be lost or even aliased through the estimation of static monthly parameters through an analysis of the grace data residuals we show that the fundamental temporal and spatial resolution of the grace data is 10 days and 400 km we present an approach similar in concept to altimetric methods that recovers submonthly mass flux at a high spatial resolution using 4 4 blocks at 10 day intervals we estimate the mass of surplus or deficit water over a 52 60 grid centered on the amazon basin for july 2003 we demonstrate that the recovered signals are coherent and correlate well with the expected hydrological signal

dwindling groundwater resources in northern india from satellite gravity observations 1 northern india and its surroundings home to roughly 600 million people is probably the most heavily irrigated region in the world temporal changes in earth s gravity field in this region as recorded by the grace satellite mission reveal a steady large scale mass loss that we attribute to excessive extraction of groundwater combining the grace data with hydrological models to remove natural variability we conclude the region lost groundwater at a rate of 54 9 km3 yr between april 2002 the start of the grace mission and june 2008 this is probably the largest rate of groundwater loss in any comparable sized region on earth its likely contribution to sea level rise is roughly equivalent to that from melting alaskan glaciers this trend if sustained will lead to a major water crisis in this region when this non renewable resource is exhausted

numerical simulations of low cape flows over a mountain ridge abstract in a recent study the authors performed numerical simulations of conditionally unstable flows past a mesoscale mountain ridge in order to investigate the statistically stationary features of the solution precipitation characteristics for intermediate to high values of convective available potential energy cape that study proposed a functional dependence of the rain rate on three parameters related respectively to the triggering and the orographic forcing of convection and to the ratio of the advective to convective time scales the present study extends that analysis to cover larger regions of the parameter space including experiments corresponding to a wider range of cape it is found here that the low cape moderate wind experiments do not fit the functional dependence for rain rate amount and location proposed in the authors previous study the analysis of the present solutions suggests that two additional nondimensional parameters should be taken into account

time variable gravity from grace first results eleven monthly grace gravity field solutions are now available for analyses we show those fields can be used to recover monthly changes in water storage both on land and in the ocean to accuracies of 1 5 cm of water thickness when smoothed over 1000 km the amplitude of the annually varying signal can be determined to 1 0 cm results are 30 better for a 1500 km smoothing radius and 40 worse for a 750 km radius we estimate the annually varying component of water storage for three large drainage basins the mississippi the amazon and a region draining into the bay of bengal to accuracies of 1 0 1 5 cm

reply to comment on the timing and evolution of the post glacial transgression across the sea of marmara shelf south of istanbul by hiscott et al marine geology 248 228 236 in their comment hiscott and co authors adhere rigidly to ages and sources for sedimentary units in the subsurface of the marmara shelf that they have previously reported in their publications from 2002 through 2007 this adherence is in spite of a superior age depth model from our 13 m long sediment core that penetrated deeply into the deposits under consideration and in disregard to the results of subsequent more detailed and full coverage mapping of the region under scrutiny the age revisions are dismissed by the authors of the comment as representing sediments severely disturbed during coring we rebut this criticism the bosporus source attributed by them to the sedimentary units sampled and dated by us appears to be driven by their conception that the black sea had a persistent outflow prior to its two way connection with marmara irrespective of whether the outflow was persistent our reply shows that the drawing of the isopachs of the sedimentary units by hiscott and co authors was accomplished in a fashion to promote the bosporus source hypothesis regardless of the geographic limits of their survey the ages assigned to the units are equally indeterminate because the cores used by them have missing core tops of unknown lengths that are not discussed in their publications furthermore the sub bottom reflectors at the sites where the reflectors were calibrated to their only core without a missing top are actually hidden by the finite width of the bottom reflecting wavelet

area and mass changes of siachen glacier east karakoram here we present a comprehensive assessment of siachen glacier east karakoram in terms of its area and elevation change velocity variations and mass budget utilizing different satellite datasets including landsat hexagon cartosat i shuttle radar topography mission envisat advanced synthetic aperture radar and japanese advanced land observing satellite phased array type l band sar the total areal extent of siachen glacier did not change significantly between 1980 and 2014 however the exposed ice area decreased during that period the terminus of the glacier has experienced substantial downwasting on average 30 m over the period of 1999 2007 followed by a retreat of the transition between exposed and debris covered ice by a distance of 1 3 km during the short span 2007 14 the spatial patterns of the elevation difference and velocity are heterogeneous over the large areal extent of siachen glacier the average velocity of the entire glacier as computed between 11 december 2008 and 26 january 2009 was 12 3 0 4 cm d 1 while those estimated separately for the accumulation and ablation regions were 9 7 0 4 cm d 1 and 20 4 0 4 cm d 1 respectively the mass budget of siachen glacier is estimated to be 0 03 0 21 m w e a 1 for the period of 1999 2007

simulations of moist nearly neutral flow over a ridge although a fairly common atmospheric condition in orographic rain scenarios there is relatively little known about moist neutral flows over a ridge from theory and modeling presented in this paper are numerical simulations of the orographic flow modification occurring for a two dimensional moist nearly neutral flow over a ridge in the regime where the coriolis force can be neglected if an initially saturated moist neutral flow were to remain everywhere saturated as it flows over an obstacle then the expected solution would be the linear solution because the condition for linearity hill height less than the ambient wind velocity static stability is always met however for higher mountains the solutions indicate the development of areas of unsaturated air with correspondingly larger values of local static stability this internal switching from small to large values of static stability is an inherent nonlinearity which has far reaching consequences for understanding the orographic flow modification in this regime the sensitivity of the solution to the mountain height and to the initial cloud water content is analyzed here the authors find that the solutions fall into three basic categories if the mountain height is small enough a saturated flow can be maintained everywhere given sufficient initial cloud water for tall mountains the atmosphere upwind of the mountain is maintained in a saturated state and transitions to an unsaturated downslope flow on the lee side which has characteristics associated with downslope windstorms for mountains of intermediate height the solutions show the existence of an upwind propagating disturbance that has the effect of desaturating the atmosphere above the mountain

stable isotope studies on mono lake california 1 d18 in lake sediments as proxy for climatic change during the last 15 years mono lake is a hypersaline alkaline lake in the mono basin located at the eastern base of the californian sierra nevada its lake level history since 1912 has been recorded instrumentally showing the decline of lake surface elevations initiated by the 1941 artificial diversion of stream inflow we have made high resolution oxygen isotopic measurements on the total carbonate fraction of lake sediments and shown that the s o record parallels the lakelevel fluctuations rather well the measurements were carried out on sediments that had been leached with deionized water to isolate the isotopic signals of the calcium carbonate from those of pore water and water soluble carbonate salts in the sediment extending the s o record back in time we found that lake level changed markedly during the past 150 yr reflecting climatic variations and resultant runoff fluctuiitions lake levels were high around 1845 1880 and 19 15 and low around 1860 1900 and 1933 this study demonstrates that closed basin lake sediment s180 provides an effective means of probing past precipitation variations in arid to semiarid regions such as the great basin in the western united states numerous attempts have been made to reconstruct paleolake levels on the basis of geological and stable isotopic evidence from which paleohydrological conditions have been inferred studies on closed basin lakes in semiarid and tropical zones have contributed greatly to paleoclimatic research particularly for the late pleistocene and the holocene e g street perrott and harrison 1985 chivas et al 1986 gasse et al 1991 water entering closed basin lakes via rain and runoff leaves by evaporation hence fluctuations in lake level and volume should serve to indicate changes in the moisture budget associated with climatic change mono lake located in eastern california about 480 km north of los angeles fig l is the only terminal lake in the mono basin its present ratio of surface area 150 km2 to catchment area 2 072 km2 is 7 100 in contrast to the ratio of 33 100 for lake russell during the last glacial period russell 1889 lajoie 1968 mono lake committee 1981 since 1912 the levels of mono lake have been measured by the u s geological survey usgs and the los angeles department of water and power ladwp blevins et al 1987 since its historic high in 1915 the water level within the lake has fallen as a result of climatic changes the lake level fall has been exacerbated by the diversion of inflow to the lake by ladwp since 1941 and has caused a further increase in salinity and alkalinity dur

glaciology no ice lost in the karakoram the fate of glaciers in the greater himalaya is widely discussed but poorly known a new measurement in the central karakoram mountain range suggests that glacier mass change in this region contributes to sea level rise nearly 0 05 mm per year less than has been thought

bayesian exploration of multivariate orographic precipitation sensitivity for moist stable and neutral flows abstractrecent idealized studies examined the sensitivity of topographically forced rain and snowfall to changes in mountain geometry and upwind sounding in moist stable and neutral environments these studies were restricted by necessity to small ensembles of carefully chosen simulations research presented here extends earlier studies by utilizing a bayesian markov chain monte carlo mcmc algorithm to create a large ensemble of simulations all of which produce precipitation concentrated on the upwind slope of an idealized gaussian bell shaped mountain mcmc based probabilistic analysis yields information about the combinations of sounding and mountain geometry favorable for upslope rain as well as the sensitivity of orographic precipitation to changes in mountain geometry and upwind sounding exploration of the multivariate sensitivity of rainfall to changes in parameters also reveals a nonunique solution multiple combinations of flow topography and environment produce similar surface rainfall amo

application of theory to simulations of observed cases of orographically forced convective rainfall abstractin two recent papers the authors reported on numerical simulations of conditionally unstable flows past an idealized mesoscale mountain ridge these idealized simulations which were performed with a three dimensional explicitly cloud resolving model allowed the investigation of simulated precipitation characteristics as a function of the prescribed environment the numerical solutions were carried out for a uniform wind flowing past a bell shaped ridge and using an idealized unstable sounding with prescribed values of the relevant parameters in the present work the application of these theoretical results to observed cases of orographically forced convective rainfall including the big thompson flood 1976 colorado the oahu flood 1974 hawaii and the gard flood 2002 france is reported specifically numerical simulations have been carried out using observed and idealized soundings relevant to these cases but with idealized topography it is found that using the observed soundings but

sediment biogeochemistry of iron and sulfur in an acidic lake abstract the biogeochemical cycling of fe and s in the sediments of acidic big moose lake adirondack park ny u s a was investigated sediment cores and porewater samples were collected along a depth transect from the hypolimnion 24 m water depth metalimnion 17 m and epilimion 8 12 m four vertically distinguishable zones in the sediment environment were observed at each site 1 1 no3 disappearance near the sediment water interface 2 2 accumulation of solid phase fe in the top 5 cm 3 3 coincident accumulation of chromium reducible sulfur crs disappearance of so4 and minima in c s and 34s at or slightly below maxima in oxide bound fe and 4 4 homogenous background concentrations in s and fe below 30 and 10 cm respectively iron and sulfur accumulations in the upper 10 cm occurred at the same depths in cores of different ages indicating that diagenetic rather than depositional processes played a dominant role in determining near surface fe and s profiles although sediment accumulation rates varied along the transect the four zones were located at similar depths in the sediment column at all sites diagenetic processes play a major role in the development of these features in big moose lake the extent of fe enrichment was considerably greater in the metalimnetic and epilimnetic sediments in contrast concentrations of fe were lower in hypolimnetic sediments which appeared to be losing fe to the water column at all sites increases in total s from a background concentration of 60 80 mol g 1 of dry mass occurred in sediments dated approximately 1850 more recent increases to 560 mol sg 1 occurred asynchronously in the cores indicating an important role of sulfate reduction in adding s to sediments however organic sulfur accumulation accounted for 22 56 of the recent increase in sediment s concentrations of iron and organic carbon were high in lake sediments and probably do not limit s storage in this lake

geodetic and direct mass balance measurements comparison and joint analysis this paper describes a new compilation of both direct and geodetic mass balance measurements develops a procedure to reduce diverse balance measurements over different time spans to common time spans and presents updated estimates of global average balance of small glaciers based on the enlarged compilation although geodetic measurements are fewer than direct measurements they cover four times as many balance years direct and geodetic measurements are unbiased with respect to one another but differences are often substantial the statistical procedure can be understood by imagining that an n year balance measurement is an average of a series of 1 year measurements the series is hypothetical but we can calculate the uncertainty of each of its elements if in addition to its measured average we can also estimate its standard deviation for this claim to be valid the annual series must be stationary and normally distributed with independent roughly uncorrelated elements for which there is reasonable evidence the need to know the standard deviation means that annual direct measurements from a nearby glacier or equally reliable information about variability are indispensable given this information the new methodology results in moderately more negative balances this is probably because tidewater glaciers are better represented in the geodetic data in any case the most recent published estimate of global average balance 0 8 1 0 mm a 1 of sea level equivalent for 2001 04 is now increased substantially to 1 1 1 4 mm a 1 for 2001 05

a joint analysis of river runoff and meteorological forcing in the karakoram upper indus basin satellite geodetic altimetry investigations in the karakoram have indicated slight mass gain or loss of the glaciers during the early part of 21st century equivalent discharge in the upper indus basin uib due to these mass changes has been estimated at 5 to 10 of mean annual flow however satellite altimetry and geodetic glacier mass estimates in the extreme topography of the karakoram have not yet been counter validated by hydrological analysis therefore we present a first cross validation of three to five decades of river flow data from the three major watersheds in the karakoram with matching series of monthly precipitation temperature and evaporation provided by six atmospheric reanalysis products for 1979 2014 the analyses suggest that in most cases river flows have been increasing steadily from the end of the 1960 s and 1970 s to the middle of the 1990 s and have stabilized or are in decline since then hunza watershed in karakoram west shows consistently declining flows over the first half of the analysis period and stable flows during the second half for most of the summer melting season suggesting mass accumulation rising river flows in the shyok and shigar watersheds followed by stabilizing or slightly declining flows from 1995 onward can be explained by consistently increasing precipitation during the first half of the analysis period and successive stabilization or minor decline thereof flow data do not necessarily suggest considerable loss or gain of glacial mass in the karakoram during the late 90 s and early 2000 s as suggested by satellite based altimetry studies

physical properties of a porcellanite layer southwest indian ridge constrained by geophysical logging abstract a distinct porcellanite layer from the southwest indian ridge intercalated in pleistocene diatom ooze was studied using nondestructive physical property measurements and sedimentological data this bed was sampled by two piston cores at a water depth of 2615 m the 3 5 cm thick porcellanite layer appears in the cores at a depth of 6 03 m core ps2089 2 and 7 73 m core ps2089 1 below the seafloor due to its characteristic physical properties the porcellanite bed can be detected with core measurements and its distribution and lateral extent mapped with echosounding the physical index properties wet bulk density and electrical resistivity increase significantly across this bed magnetic susceptibility is used to compare the lithological units of both cores and to distinguish whether resistivity anomalies are caused by a higher amount of terrigenous components or by the presence of porcellanite the porcellanite has the special characteristic to affect a positive anomaly in resistivity but not in susceptibility most marine sediments in contrast show a positive correlation of magnetic susceptibility versus electrical resistivity therefore a combination of electrical resistivity and magnetic susceptibility logs yields a definite detection of the porcellanite bed images from the x ray ct survey indicate that the porcellanite is lithified and brittle and fragmented when the piston corer penetrated the bed

further results on moist nearly neutral flow over a ridge abstract in a recent study the authors performed numerical simulations of moist nearly neutral flows over a ridge using the weather research and forecasting wrf model in a regime where the coriolis force can be neglected and with the simple kessler warm rain microphysical scheme in the present work further numerical solutions using more general and realistic experimental conditions are discussed the upstream propagating disturbance which was found in the author s previous study to desaturate the initially saturated sounding for intermediate mountain heights is present for all the simulations with taller mountains considered in the present work the inclusion of the coriolis force however suppresses the upwind propagation of the dry region and weakens the downstream development of convective cells the sensitivity to different microphysical schemes has also been investigated the simple kessler scheme was compared with a more complete scheme by lin et al which includes ice species some differ

evaluation of glacier changes in high mountain asia based on 10 year grace rl05 models in this paper 10 years of time variable gravity data from the gravity recovery and climate experiment release 05 have been used to evaluate the glacier melting rate in high mountain asia hma using a new computing scheme i e the space domain inverse method we find that in hma area there are three different kinds of signal sources that should be treated together the two generally accepted sources glacier melting and india underground water depletion are estimated to change at the rate of 35 0 5 8 gt yr 0 09 mm yr sea level rising and 30 6 5 0 gt yr respectively the third source is the remarkable positive signal 30 gt yr in the inner tibetan plateau which is challenging to explain further we have found that there is a 5 year undulation in pamir and karakoram which can explain the controversies of the previous studies on the glacier melting rate here this 5 year signal can be explained by the influence of arctic oscillation and el nino southern oscillation

variations in the earth s oblateness during the past 28 years 1 analysis of satellite laser ranging slr data indicates that the earth s dynamic oblateness j2 has undergone significant variations during the past 28 years the dominant signatures in the observed variations in j2 are 1 a secular decrease with a rate of approximately 2 75 10 11 yr 1 2 seasonal annual variations with a mean amplitude of 2 9 10 10 3 significant interannual variations with timescales of 4 6 years and 4 a variation with period of 21 years and an amplitude of 1 4 10 10 with minimum in december 1988 two large interannual variations are related to the strong el nino southern oscillation events during the periods of 1986 1991 and 1996 2002 and it appears that another interannual cycle may have started in late 2002 the superposition of the decadal variation on the interannual signal makes the j2 fluctuation appear to be anomalously large during the 1996 2002 period contemporary models of the mass redistributions in the atmosphere ocean and surface water can explain a major part of the 4 to 6 year fluctuations however the cause of the decadal variation remains unknown

records of geomagnetic secular variation since 1200 ad and the potential for chronological control of lake sediments in northern alberta we assess whether absolutely aged declination changes can be used to date recent massive lake sediments at the sub century scale three issues limiting such studies are addressed recovery of undisturbed recent lake sediments assessment of the reliability of the geomagnetic record and the comparison of lake sediment records with historic re cords a 793 year long geomagnetic chronology was obtained from the annually laminated sediment of rainbow lake a sediment disturbance was minimized by freezing the sediment in situ and maintaining this state for geomagnetic analyses geomagnetic chronologies ca 600 years long from the massive sediments of fariya lake and ninisith lake were collected in removable plastic tubes using a piston corer sediment disturbance was minimized by ex situ draining of water from the plastic tubes the reliability of the geomagnetic record was assessed using a measure of internal co herence with an absolute cutoff of 15 by further separating the samples at coherence values of 5 and 7 5 it was possible to identify zones of disturbance and reduced compaction the most reliable samples had a high magnetic in tensity due to high inputs of magnetic minerals sediment compression and inputs of stable magnetic minerals neither freezing nor dewatering of the sediments appeared to decrease reliability of the geomagnetic record the declination chronology from the annually laminated sediments was significantly correlated with a 230 year long historical record from churchill manitoba and with the massive lake sediment chronology from fariya lake geomagnetic dating was not possible however because of the large amplitude in the annually laminated sediment declination record the large number of years of sediment in many specimens and the lack of reliability for samples that contain few years of sedi ment per specimen

ensuring confidence in radionuclide based sediment chronologies and bioturbation rates abstract sedimentary records of naturally occurring and fallout derived radionuclides are widely used as tools for estimating both the ages of recent sediments and rates of sedimentation and bioturbation developing these records to the point of data interpretation requires careful sample collection processing analysis and data modeling in this work we document a number of potential pitfalls that can impact sediment core records and their interpretation this paper is not intended as an exhaustive treatment of these potential problems rather the emphasis is on potential problems that are not well documented in the literature as follows 1 the mere sampling of sediment cores at a resolution that is too coarse can result in an apparent diffusive mixing of the sedimentary record at rates comparable to diffusive bioturbation rates observed in many locations 2 210 pb profiles in slowly accumulating sediments can easily be misinterpreted to be driven by sedimentation when in fact bioturbation is the dominant control multiple isotopes of different half lives and or origin may help to distinguish between these two possible interpretations 3 apparent mixing can occur due simply to numerical artifacts inherent in the finite difference approximations of the advection diffusion equation used to model sedimentation and bioturbation model users need to be aware of this potential problem solutions to each of these potential pitfalls are offered to ensure the best possible sediment age estimates and or sedimentation and bioturbation rates can be obtained

the gravity recovery and climate experiment mission overview and early results 1 the grace mission is designed to track changes in the earth s gravity field for a period of five years launched in march 2002 the two grace satellites have collected nearly two years of data a span of data available during the commissioning phase was used to obtain initial gravity models the gravity models developed with this data are more than an order of magnitude better at the long and mid wavelengths than previous models the error estimates indicate a 2 cm accuracy uniformly over the land and ocean regions a consequence of the highly accurate global and homogenous nature of the grace data these early results are a strong affirmation of the grace mission concept

a new high resolution radiocarbon bayesian age model of the holocene and late pleistocene from core md02 2494 and others effingham inlet british columbia canada with an application to the paleoseismic event chronology of the cascadia subduction zone annually laminated sediments from the anoxic inner basin of effingham inlet pacific coast of vancouver island british columbia canada yield a high resolution 42 m paleoenvironmental record from the present to about 14 ka 14c bp 17 ka cal bp a new age model based on 68 radiocarbon dates from twigs and small plant material from the 40 m core md02 2494 and 2 m freeze cores from the surface is anchored by the mazama ash and varve counting a poisson process sedimentation model is used applying a new method to determine the poisson k value giving a realistic age model compatible with the multi proxy core data twenty one seismites which are lithofacies in the effingham cores that may be representative of seismically triggered mass wasting events are identified and dated precisely then compared with the chronology of the deep sea turbidite record farther south in the cascadia subduction zone csz to determine if regional sediment disturbances can be identified with 16 proposed correlations

bedrock response to llanquihue holocene and present day glaciation in southernmost south america 1 modern geodetic techniques such as precise global positioning system gps measurements and high resolution space gravity mapping make it possible to measure the present day rate of viscoelastic gravitational earth response to present and past glacier mass change patagonia is a rapidly evolving glacial environment over the past decade the local rate of surface stress unloading may be the largest anywhere on the planet we compute the present day land uplift rate that could be observed using bedrock gps measurements the little ice age lia of the past half millennium generates large vertical rates since the underlying mantle material is likely to have anomalously low viscosity owing to late neogene ridge subduction

impact of resolution and radar penetration on glacier elevation changes computed from dem differencing regional glacier mass balances can be measured by subtracting multi temporal digital elevation models dems however dems are often biased with altitude and it remains unclear whether the elevation differences observed on the ice free terrain can be used to correct biases on ice covered areas iwe investigate such altitude related biases using dems from three different sensors spot5 srtm c band and srtm x band the bias due to different original resolutions can be corrected using a relationship between curvature and elevation difference calculated on ice free terrain the impact of c band radar penetration into snow and ice can be evaluated for a specific region by comparing srtm c band and srtm x band dems in our test area karakoram the resolution related bias has a minor influence on region averaged elevation change conversely not accounting for c band penetration would significantly biased the mean elevation change

mountain glaciers and ice caps around antarctica make a large sea level rise contribution the intergovernmental panel on climate change ipcc estimates that the sum of all contributions to sea level rise for the period 1961 2004 was 1 1 0 5 mm a 1 leaving 0 7

an assessment of sediment loss and distortion at the top of short gravity cores abstract examination of laminated bottom sediment cores from two glacier fed lakes in the canadian rocky mountains allows an assessment of the amount of material lost or badly distorted by open barrel gravity corer impact analysis of sediment 137cs content indicates that the laminae are of annual periodicity and allows precise dating of individual laminae examination of 8 cores from hector lake indicates that a mean of 4 6 mm of sediment was missing from the top of each using sedimentation rates in the recovered sections of core and lake wide sedimentation rate variations to approximate sedimentation rates in the missing sections of the core an additional mean thickness of 3 6 mm was strongly distorted analysis of 14 cores from bow lake indicates that on average 6 4 mm of sediment was lost at core tops and an additional 11 4 mm or less suffered severe distortion these data suggest that at least in the lakes studied high impact velocity gravity coring has less of an effect on core top sediment than has previously been reported

mechanisms of intense alpine rainfall abstract numerical studies by the authors and others of the 1994 piedmont flood show that the orographically modified flow was a critical element for the production of extraordinary rainfall to uncover the precise mechanism of orographic rainfall occurring in full physics mm5 simulations of the 1994 piedmont flood the authors carried out simulations with the same real data initial and boundary conditions but with the real orography replaced by an idealized one with excellent agreement between real and idealized orography on the rainfall rate versus time in the piedmont area analysis of the idealized orography simulation provides a clear picture of the model s mechanism of orographically induced rainfall as noted in previous studies of the 1994 piedmont case a moist saturated airflow has a reduced effective static stability and tends to flow over the mountains while an unsaturated airstream is stable and tries to flow around toward the left in the northern hemisphere in the 1994 piedmont case t

rising river flows and glacial mass balance in central karakoram summary field observations and geodetic measurements suggest that in the central part of the karakoram mountains glaciers are either stable or expanding since 1990 in sharp contrast to glacier retreats that are prevalent in the himalayas and adjoining high altitude terrains of central asia decreased discharge in the rivers originating from karakoram is cited as a supporting evidence of this somewhat anomalous phenomenon here in contrary to those citations we show that river discharge during the melting season of the glaciers in central karakoram has increased from 1985 to 2010 we have implemented a sophisticated statistical procedure involving non parametric tests combined with a benchmark smoothing technique that has proven to be a powerful method for empirical trend analysis to remove the stochastic component from the trend component in a time series melt water from winter snows is the dominant constituent of june and july flows glacial melts predominantly contribute to august and partially to september flows which are controlled by monsoonal snowfall too at elevations approximately 3500 m for all four summer months flows increased from 1985 to 2000 august flows which actually reflect the states of the glaciers have continued to rise steadily after 2000 at the same rate as those did for the period 1985 2000 however the rising trends of june and july flows changed to slightly declining trends from 2000 to 2010 these trends most likely indicate drop in winter snowfall over karakoram and do not provide direct indications about the states of the glaciers the rising trend of august discharge is due to change in glacial storage at a steadily decreasing rate of approximately 0 04 0 05 mm day year for the period 1985 2010 this rate is nearly equal to the rate of increase in precipitation during the summer months over karakoram mountains in recent decades as determined from the era 40 and gpcp precipitation datasets thereby this is most plausibly why the glacial mass balance in central karakoram is nearly neutral the rising river flows accompanying non negative glacier mass balance are consistent with predicted future river flows derived from hydrologic modeling coupled with a climate projection suggesting increasing temperature and precipitation with unchanged glacier covers this investigation reconciles two apparently contradictory observations namely rising river flows and either zero or slightly positive mass balance of central karakoram glaciers

stable lead isotopes contaminant metals and radionuclides in upper hudson river sediment cores implications for improved time stratigraphy and transport processes radionuclide stable lead isotope and trace metal analyses on fine grained sediment cores collected along a 24 mile reach of the upper hudson river were used to establish temporal trends of contaminant loadings to establish stable lead isotopes as an additional stratigraphic tool and as tracers for resolving particle transport fluxes over periods of decades very large contaminant inputs of cd sb pb and cr were evident in the sediment record one potential large source for these metals was from a pigment manufacturing facility in glens falls ny the total range in stable lead isotope ratios observed in well dated cores from about 15 miles downstream of the potential metal inputs was large e g maximum difference in 206 pb 207 pb is 10 and characterized by four major shifts occurring in the 1950s 1960s 1970s and 1980s the temporal trend in 206 pb 207 pb has been used to establish precise dating of a sediment core from 24 miles further downstream the large magnitude and abrupt shifts in stable lead isotope ratios preserved in upper hudson sediment cores provide a way to significantly improve dating models based only on radionuclide analyses cadmium lead and antimony were identified as quite sensitive tracers of upper hudson sediments due to the magnitude of contamination and the lack of significant additional downstream sources of these contaminant metals metal measurements in a pair of sediment cores located 24 miles apart were used to constrain relative fluxes of sediment entering the river between the two coring locations with sediment sections deposited between the early 1960s and the late 1970s in these two cores suggesting that 3 4 times more sediment entered the river between the two coring sites than was transported from upstream these dilution factors agree very well with estimates based on suspended sediment measurements during a flood event in april 1994 and with estimates based on mechanistic model of suspended sediment transport between 1977 and 1992 d 2003 elsevier science b v all rights reserved

estimating geocenter variations from a combination of grace and ocean model output 1 in this study we estimate a time series of geocenter anomalies from a combination of data from the gravityrecoveryandclimateexperiment grace satellitemissionandthe outputfromoceanmodels amatrixequationisderivedrelating totalgeocentervariations to the grace coefficients of degrees two and higher and to the oceanic component of the degree one coefficients we estimate the oceanic component from two state of the art ocean models results are compared to independent estimates of geocenter derived from other satellite data such as satellite laser ranging and gps finally we compute degree one coefficients that are consistent with the processing applied to the grace level 2 gravity field coefficients the estimated degree one coefficients can be used to improve estimates of mass variability from grace which alone cannot provide them directly

sharply increased mass loss from glaciers and ice caps in the canadian arctic archipelago the canadian arctic archipelago contains one third of the global volume of land ice outside the ice sheets but its contribution to sea level change is largely unknown gardner et al use three independent techniques to reveal that mass loss from the archipelago was 92 12 gigatonnes per year in 2007 09 about three times greater than in 2004 06 and coincident with warmer summer temperatures the record is too short to allow a firm conclusion on longer term trends but it is clear that the canadian arctic archipelago is a significant contributor to sea level rise mountain glaciers and ice caps are contributing significantly to present rates of sea level rise and will continue to do so over the next century and beyond1 2 3 4 5 the canadian arctic archipelago located off the northwestern shore of greenland contains one third of the global volume of land ice outside the ice sheets6 but its contribution to sea level change remains largely unknown here we show that the canadian arctic archipelago has recently lost 61 7 gigatonnes per year gt yr 1 of ice contributing 0 17 0 02 mm yr 1 to sea level rise our estimates are of regional mass changes for the ice caps and glaciers of the canadian arctic archipelago referring to the years 2004 to 2009 and are based on three independent approaches surface mass budget modelling plus an estimate of ice discharge smb d repeat satellite laser altimetry icesat and repeat satellite gravimetry grace all three approaches show consistent and large mass loss estimates between the periods 2004 2006 and 2007 2009 the rate of mass loss sharply increased from 31 8 gt yr 1 to 92 12 gt yr 1 in direct response to warmer summer temperatures to which rates of ice loss are highly sensitive 64 14 gt yr 1 per 1 k increase the duration of the study is too short to establish a long term trend but for 2007 2009 the increase in the rate of mass loss makes the canadian arctic archipelago the single largest contributor to eustatic sea level rise outside greenland and antarctica

natural and anthropocene fluxes of trace elements in estuarine sediments of galician rias the anthropocene has been proposed as a new geo stratigraphic epoch where humans have become a global factor affecting the ecosystems estuarine sediments constitute a biogeochemical reservoir where trace elements tes from natural sources mix with a fraction generated by human activities this study assessed the natural lithogenic imprint of tes from uncontaminated sedimentary records to study anthropogenic changes sediment cores were sampled in the estuarine part of the low populated and low industrialized rias of ares a betanzos b and cedeira c which are located in the nw of the iberian peninsula cores were dated by the 210pb method covering up to the last century period sedimentation rates in mm yr 1 were 3 4 0 6 older than 1961 and 8 2 3 2 younger than 1961 for core a 0 9 0 2 1940 and 4 2 2 3 for core b and 13 4 1 4 for core c the background fluxes of tes were in the ranges of in g m 2 yr 1 50 560 for al and fe 20 320 for poc and 8 100 for ps and in mg m 2 yr 1 20 120 for as 0 2 2 0 for cd 7 110 for co 40 870 for cr 20 230 for cu 0 1 0 6 for hg 290 2800 for mn 4 24 for mo 20 410 for ni 20 150 for pb 60 800 for v and 70 700 for zn the three cores showed an anthropogenic influence since the mid 20th century the detected human impact during the anthropocene was due to the eume river damming and as pontes lignite mining the largest mine open pit in the iberian peninsula in core a by bridge road constructions vehicles emissions and river mouth urbanization in core b and changes in land use in core c sediment accumulation rates increased 2 4 core a and 4 7 times core b while tes fluxes increased 2 4 times in core a and between 3 6 and 5 1 times in core b pre industrial sedimentary records showed the lithogenic differences of the drainage basins mainly granitic watersheds for cores a and b and the prevalence of basic rocks of the ortegal geological complex for core c this explains the high concentrations and fluxes of cr ni and v of core c the different lithogenic imprints highlight the value of using local background references in contamination studies such as those on the anthropocene influence in estuaries which occurred after the spanish civil war in the studied rias

slight mass gain of karakoram glaciers in the early twenty first century the mass balance of hindu kush karakoram himalaya glaciers has been debated partly because of a severe lack of observations from the region an analysis of the regional mass balance of karakoram glaciers by comparison of digital elevation models from 1999 to 2008 reveals a small glacier mass gain in the area

a linear theory of orographic precipitation a linear theory of orographic precipitation is developed including airflow dynamics condensed water advection and downslope evaporation the formulation extends the widely used upslope model vertically integrated steady state governing equations for condensed water are solved using fourier transform techniques closed form expressions are derived for special cases for more general cases the precipitation field is computed quickly by multiplying the terrain transform by a wavenumber dependent transfer function five length scales are included in the model mountain width a buoyancy wave scale the moist layer depth and two condensed water advection distances the efficiency of precipitation in the model is sensitive to the decay of the forced ascent through the moist layer and to the advection of condensed water downwind into the region of descent the strong influence of horizontal scale on precipitation pattern and amount predicted by the model is discussed the model is illustrated by applying it to the olympic mountains in washington state

orographic effects on rainfall in map cases iop 2b and iop 8 although the large scale flow was similar important differences in mesoscale atmospheric structure made the difference between moderately intense rain in intensive observing period iop 2b and relatively light rain in iop 8 in the lago maggiore target area lmta this conclusion is supported here through analysis of data from and numerical simulations of these two cases analysis of the large scale data shows that there was in both cases a moist tongue of southerly flow moving from the west to the east of the alpine south side mesoscale data analysis and numerical simulations suggest that the most important difference between the two cases was the presence of a cold stable air mass in the po valley in iop 8 which persisted through the period in which the large scale moist tongue was progressing eastward and prevented the most humid air from reaching the lmta another difference contributing to the greater rainfall in the lmta in iop 2b was the development of conditional instability with associated convective rain due to the effect of the alps on the eastward passage of the moist tongue in iop 8 the atmosphere remained locally stable throughout the period copyright 2003 royal meteorological society

reliability of core sampling of soft bottom sediment an in situ study the performances of four light weight open sampling devices intended for use in soft sediments the axelsson hakanson gravity corer the kajak gravity corer the jenkin bottom sampler and the ekman grab box corer were examined in situ by direct observation measurement and photographic documentation by a scuba diver restrictions on the reliability of the sediment samples obtained with these devices and sediment coring instruments in general are evaluated separate studies of core shortening show 1 a positive linear relationship between sediment penetration depth at which shortening of cores starts and coring tube inner diameter 2 a tube size related shift of curve pattern in the regressions of the core shortening versus sediment depth and 3 a negative non linear relationship of shortening intensity versus increasing coring tube inner diameter these findings show the great risk when sampling soft sediments of obtaining a sample quantitatively unrepresentative of the in situ stratification an accurate correction factor for the degree of core shortening requires a knowledge of 1 the sediment depth at which core shortening commences and 2 the curve describing the relationship of shortening to depth of penetration

recent contributions of glaciers and ice caps to sea level rise satellite measurements of earth s gravity field show that the mass loss of glaciers and ice caps contributed to sea level rise by approximately 0 4 millimetres per year between 2003 and 2010 the extent to which mass loss from ice covered land areas contributes to sea level rise is not known accurately in part because previous global estimates use different techniques for glaciers ice caps and ice sheets the gravity recovery and climate experiment grace satellite has provided monthly measurements of the global gravity field since 2002 using grace data jacob et al assess regional mass loss between 2003 and 2010 and conclude that mass loss from ice covered land areas contributed almost 1 5 mm per year to the sea level rise estimated mass loss from the high mountains of asia was negligible in contrast to some other reports glaciers and ice caps gics are important contributors to present day global mean sea level rise1 2 3 4 most previous global mass balance estimates for gics rely on extrapolation of sparse mass balance measurements1 2 4 representing only a small fraction of the gic area leaving their overall contribution to sea level rise unclear here we show that gics excluding the greenland and antarctic peripheral gics lost mass at a rate of 148 30 gt yr 1 from january 2003 to december 2010 contributing 0 41 0 08 mm yr 1 to sea level rise our results are based on a global simultaneous inversion of monthly grace derived satellite gravity fields from which we calculate the mass change over all ice covered regions greater in area than 100 km2 the gic rate for 2003 2010 is about 30 per cent smaller than the previous mass balance estimate that most closely matches our study period2 the high mountains of asia in particular show a mass loss of only 4 20 gt yr 1 for 2003 2010 compared with 47 55 gt yr 1 in previously published estimates2 5 for completeness we also estimate that the greenland and antarctic ice sheets including their peripheral gics contributed 1 06 0 19 mm yr 1 to sea level rise over the same time period the total contribution to sea level rise from all ice covered regions is thus 1 48 0 26 mm 1 which agrees well with independent estimates of sea level rise originating from land ice loss and other terrestrial sources6

patagonia icefield melting observed by gravity recovery and climate experiment grace 1 using recently released reprocessed gravity solutions from the gravity recovery and climate experiment grace we estimate the ice loss rate for the patagonia icefield pif of south america for the period april 2002 through december 2006 after postglacial rebound and hydrological effects are corrected the estimated rate is 27 9 11 km 3 year equivalent to an average loss of 1 6 m year ice thickness change if evenly distributed over the entire pif area the estimated contribution to global sea level rise is 0 078 0 031 mm year this is an independent confirmation of relatively large melting rate estimates from earlier studies employing topographic and cartographic data

tributary glacier surges an exceptional concentration at panmah glacier karakoram himalaya four tributaries of panmah glacier have surged in less than a decade three in quick succession between 2001 and 2005 since 1985 13 surges have been recorded in the karakoram himalaya more than in any comparable period since the 1850s ten were tributary surges in these ten a full run out of surge ice is prevented but extended post surge episodes affect the tributary and main glacier the sudden concentration of events at panmah glacier is without precedent and at odds with known surge intervals for the glaciers interpretations must consider the response of thermally complex glaciers at exceptionally high altitudes and of high relief to changes in a distinctive regional climate it is suggested that high altitude warming affecting snow and glacier thermal regimes or bringing intense short term melting episodes may be more significant than mass balance change

estimating selenium removal by sedimentation from the great salt lake utah abstract the mass of se deposited annually to sediment in the great salt lake gsl was estimated to determine the significance of sedimentation as a permanent se removal mechanism lake sediment cores were used to qualitatively delineate sedimentation regions very high to very low estimate mass accumulation rates mars and determine sediment se concentrations sedimentation regions were defined by comparison of isopach contours of holocene sediment thicknesses to linear sedimentation rates determined via analysis of 210 pb 226 ra 7 be and 137 cs activity in 20 short cores 10 cm these mars in the upper 1 2 cm of each long core ranged from 0 019 to 0 105 g sed cm 2 a surface sediment se concentrations in the upper 1 or 2 cm of each long core ranged from 0 79 to 2 47 mg kg representative mars and se concentrations were used to develop mean annual se removal by sedimentation in the corresponding sedimentation region the spatially integrated se sedimentation rate was estimated to be 624 kg a within a range of uncertainty between 285 and 960 kg a comparison to annual se loading and other potential removal processes suggests burial by sedimentation is not the primary removal process for se from the gsl

glaciers dominate eustatic sea level rise in the 21st century ice loss to the sea currently accounts for virtually all of the sea level rise that is not attributable to ocean warming and about 60 of the ice loss is from glaciers and ice caps rather than from the two ice sheets the contribution of these smaller glaciers has accelerated over the past decade in part due to marked thinning and retreat of marine terminating glaciers associated with a dynamic instability that is generally not considered in mass balance and climate modeling this acceleration of glacier melt may cause 0 1 to 0 25 meter of additional sea level rise by 2100

carbon and sediment accumulation in the everglades usa during the past 4000 years rates drivers and sources of error 1 tropical and subtropical wetlands are considered to be globally important sources of greenhouse gases but their capacity to store carbon is presumably limited by warm soil temperatures and high rates of decomposition unfortunately these assumptions can be difficult to test across long timescales because the chronology cumulative mass and completeness of a sedimentary profile are often difficult to establish we therefore made a detailed analysis of a core from the principal drainage outlet of the everglades of south florida in order to assess these problems and determine the factors that could govern carbon accumulation in this large subtropical wetland accelerator mass spectroscopy dating provided direct evidence for both hard water and open system sources of dating errors whereas cumulative mass varied depending upon the type of method used radiocarbon dates of gastropod shells nevertheless seemed to provide a reliable chronology for this core once the hard water error was quantified and subtracted long term accumulation rates were then calculated to be 12 1 g m 2 yr 1 for carbon which is less than half the average rate reported for northern and tropical peatlands moreover accumulation rates remained slow and relatively steady for both organic and inorganic strata and the slow rate of sediment accretion 0 2 mm yr 1 tracked the correspondingly slow rise in sea level 0 35 mm yr 1 reported for south florida over the past 4000 years these results suggest that sea level and the local geologic setting may impose long term constraints on rates of sediment and carbon accumulation in the everglades and other wetlands