radiocarbon based carbon source quantification of anomalous isotopic foraminifera in last glacial sediments in the western north pacific a previous study interpreted extremely 13c depleted excursions of planktonic and benthic foraminifera in last glacial sediments 17 500 to 25 400 cal years b p of the core retrieved from off shimokita peninsula and off hokkaido japan as evidence for periodic releases of methane arising from the dissociation of methane hydrate to better understand the formation process of the 13c depleted excursions we conducted high resolution natural radiocarbon measurements and biogeochemical analyses we found highly depleted 13c excursions ranging from 10 2 to 1 6 and 6 8 to 1 6 in planktonic and benthic foraminifera respectively most of the foraminiferal tests in these horizons were brown most likely as a result of postdepositional alteration reflecting the formation of authigenic carbonate on the surface of tests these alterations were also supported by high levels of mg calcite and the acid leaching test for anomalous foraminifera to evaluate the carbon sources in the altered foraminifera tests we quantified the relative contributions of 14c free methane derived carbon sources to the formation of authigenic carbonates in foraminifera with depleted 13c excursions using a coupled mass balance isotopic model 14c c and 13c 12c the radiocarbon ages of both planktonic and benthic 13c depleted foraminifera were approximately 600 to 2000 years older than those of normal tests from nearby horizons the relative contributions of authigenic carbonates derived from the methane oxidizing process reached to 22 wt for planktonic foraminifera and 15 wt for benthic foraminifera the 13c values of methane calculated from the mass balance model were between 29 and 68 for planktonic foraminifera and between 40 and 108 for benthic foraminifera consistent with 13c values reported for thermogenic and abiogenic methane in global methane hydrate reservoirs these data consistently suggest that methane related drastic environmental change occurred in the horizons that included 13c anomalies this study provides important information for interpreting geological records of the methane hydrate instability associated with climate

modeling co2 chemistry δ13c and oxidation of organic carbon and methane in sediment porewater implications for paleo proxies in benthic foraminifera i present a numerical diffusion advection reaction model to simulate co2 chemistry 13c and oxidation of organic carbon and methane in sediment porewater the model takes into account detailed reaction kinetics of dissolved co2 compounds h2o h oh boron and sulfide compounds these reactions are usually assumed to be in local equilibrium which is shown to be a good approximation in most cases the model also includes a diffusive boundary layer across which chemical species are transported between bottom water and the sediment water interface while chemical concentrations and 13ctco2 13ctco2 at these locations are frequently assumed equal i demonstrate that they can be quite different in this case shells of benthic foraminifera do not reflect the desired properties of bottom water even for species living at the sediment water interface z 0 cm environmental conditions recorded in their shells are strongly influenced by processes occurring within the sediment the model is then applied to settings in the santa barbara basin and at hydrate ridge cascadia margin locations of strong organic carbon and methane oxidation in contrast to earlier studies i show that a limited contribution of methane derived carbon to porewater tco2 in the santa barbara basin cannot be ruled out simulation of methane venting shows that at oxidation rates greater than fch4 50 molcm 2y 1 the 13c of porewater tco2 at z 1 cm is depleted by more than 15 relative to bottom water depletions of this magnitude have not been observed in living benthic foraminifera even at methane vents with much higher oxidation rates this suggests that foraminifera at these sites either calcify at very shallow sediment depth or during times when oxidation rates are much lower than 50 mol cm 2 y 1

seasonal and interannual global surface mass variations from multisatellite geodetic data 1 monthly global surface mass distribution changes are estimated in the spherical harmonic domain with a complete spectrum up to degree and order 50 the estimates are derived by inverting gps displacement series measured at roughly 450 continuously tracking sites and ocean bottom pressure obp estimates of a data assimilated ocean circulation model from 1993 to 2004 the inversion uses a hybrid estimator after singular value decomposition of the normalized measurement equations with reduced reliance on a priori spectral information the results are then compared and combined with gravity recovery and climate experiment grace gravity data to provide enhanced spectral and geographic coverage high fidelity degree 1 surface mass variation coefficients are recovered corresponding to equivalent geocenter motion with better than 0 5 mm annual amplitude precisions in all three components a clear annual surface mass cycle occurs in both gps obp and grace derived results there is very good agreement among the low degree spherical harmonic coefficients and in global geographic pattern but with significant regional differences in amplitudes annual variations of average mass over the global oceans antarctica and greenland are then derived total surface mass over both antarctica and greenland peak in their respective summers due to increased atmospheric mass large interannual variations have also been found involving several continents in the 11 year gps obp solution the patterns of variation suggest that the recent satellite laser ranging slr observation of a reversal in trend of the earth s oblateness may be largely an interannual surface mass cycle with considerable contribution from the northern continents

timing of millennial scale climate change at siple dome west antarctica during the last glacial period using atmospheric methane and the isotopic composition of o2 as correlation tools we place the dd record of ice from the siple dome west antarctica ice core on a precise common chronology with the gisp2 greenland ice core for the period from 9 to 57 ka the onset of major millennial warming events in siple dome preceded major abrupt warmings in greenland and the pattern of millennial change at siple dome was broadly similar though not identical to that previously observed for the byrd ice core also in west antarctica the addition of siple dome to the database of well dated antarctic paleoclimate records supports the case for a coherent regional pattern of millennial scale climate change in antarctica during much of the last ice age and glacial interglacial transition

localized analysis of satellite tracking data for studying time variable earth s gravity fields 1 we present a method to analyze the observations of relative distance change between two low earth orbiting satellites of the gravity recovery and climate experiment grace mission after removing the effects caused by the mean gravity field and better known temporal mass redistribution the gravitational acceleration exerted by the block mean mass within a region on the earth surface is formulated by point mass approximation and by spherical harmonic expansion in addition to the regional mass parameters the arc dependent parameters initial relative state vectors is simultaneously modeled to remove the signals not associated with the mass variation within the focus area while a certain level of approximation that is committed when locally formulating the gravitational acceleration vector for numerical integration causes model error we benefit from regionally estimating time variable mass with improved spatial and temporal resolutions in addition various temporal parameterizations depending on geographical areas and expected signals can be applied for the regional analysis in a straightforward manner and it helps to retrieve even sub daily time variable signals such as tides from many years of grace data we present the results of hydrology and ocean tide recovery in south america africa north america and antarctica from the analysis of 3 5 years of grace tracking data and compare them with the traditional global harmonic approach the algorithm development thoroughly described here will be helpful for the science community to exploit fundamental data range rate of the grace mission in addition to monthly gravity products

seasonal clockwise gyration and tilt of the australian continent chasing the center of mass of the earth s system from gps and grace as atmosphere ocean ice and terrestrial water are redistributed the center of mass cm of the earth s system moves and the accompanying loading yields global surface deformation in australia when gps surface displacements were corrected for local mass change hydrology atmosphere and ocean with grace data the residual gps data reveal a peculiar seasonal mode of continental deformation during the southern summer the entire continent coherently shifts northwest by 1 mm and the southeastern part is uplifted while the northwestern part is subsided by 2 3 mm and the opposite patterns of deformation are observed during the southern winter such characteristic deformation could be understood to be a result of the earth s elastic response to globally averaged surface mass load generally heavier in europe during southern summer and in the south pacific ocean during southern winter it was found that such deformation is even larger than local hydrology induced loading effects in horizontal motion over australia a simple method of determining locations of the cm was developed by combining gps and grace data the latter being insensitive to the cm motion but sufficiently accurate to remove the local hydrologic and atmospheric effects in gps data the cm signals are pronounced over systematic errors in gps and grace data the cm coordinates estimated by inversion of the australian gps dataset and grace agree with the geocenter motions determined by satellite tracking analysis this study suggests an independent way of monitoring the cm motion entirely based on two distinct geodetic measurements of gps and grace

on the origin and timing of rapid changes in atmospheric methane during the last glacial period we present high resolution records of atmospheric methane from the gisp2 greenland ice sheet project 2 ice core for four rapid climate transitions that occurred during the past 50 ka the end of the younger dryas at 11 8 ka the beginning of the bolling allerod period at 14 8 ka the beginning of interstadial 8 at 38 2 ka and the beginning of interstadial 12 at 45 5 ka during these events atmospheric methane concentrations increased by 200 300 ppb over time periods of 100 300 years significantly more slowly than associated temperature and snow accumulation changes recorded in the ice core record we suggest that the slower rise in methane concentration may reflect the timescale of terrestrial ecosystem response to rapid climate change we find no evidence for rapid massive methane emissions that might be associated with large scale decomposition of methane hydrates in sediments with additional results from the taylor dome ice core antarctica we also reconstruct changes in the interpolar methane gradient an indicator of the geographical distribution of methane sources associated with some of the rapid changes in atmospheric methane the results indicate that the rise in methane at the beginning of the bolling allerod period and the later rise at the end of the younger dryas were driven by increases in both tropical and boreal methane sources during the younger dryas a 1 3 ka cold period during the last deglaciation the relative contribution from boreal sources was reduced relative to the early and middle holocene periods

surface mass redistribution inversion from global gps deformation and gravity recovery and climate experiment grace gravity data monitoring hydrological redistributions through their integrated gravitational effect is the primary aim of the gravity recovery and climate experiment grace mission time variable gravity data from grace can be uniquely inverted to hydrology since mass transfers located at or near the earth s surface are much larger on shorter timescales than those taking place within the deeper earth and because one can remove the contribution of atmospheric masses from air pressure data yet it has been proposed that at larger scales this may be achieved independently by measuring and inverting the elastic loading associated with redistributing masses e g with the global network of the international gps service igs this is particularly interesting as long as grace monthly gravity solutions do not yet match the targeted baseline accuracies at the lower spherical harmonic degrees in this contribution 1 we describe and investigate an inversion technique which can deal jointly with gps data and monthly grace solutions 2 previous studies with gps data have used least squares estimators and impose solution constraints through low degree spherical harmonic series truncation here we introduce a physically motivated regularization method that guarantees a stable inversion up to higher degrees while seeking to avoid spatial aliasing 3 we apply this technique to gps data provided by the igs service covering recent years we can show that after removing the contribution ascribed to atmospheric pressure loading estimated annual variations of continental scale mass redistribution exhibit pattern similar to those observed with grace and predicted by a global hydrology model although systematic differences appear to be present 4 we compute what the relative contribution of grace and gps would be in a joint inversion using current error estimates gps could contribute with up to 60 to degree 2 till 4 spherical harmonic coefficients and up to 30 for higher degree coefficients

light δ13c events during deglaciation of the east greenland continental shelf attributed to methane release from gas hydrates we have documented high resolution stable isotope records from three marine cores on the east greenland shelf these records exhibit three rapid light 13c events 3 to 7 in benthic and planktic foraminifera during deglaciation that are spatially and temporally transgressive the light 13c events are associated with light planktic 18o indicative of meltwater in kangerlussuaq trough the first 13c event occurs at initial deglaciation 13 94 14 0 cal ka and the second occurs at 12 85 12 9 cal ka a younger event at 10 3 9 3 cal ka is recorded near the mouth of nansen fjord during final deglaciation the hypothesized mechanism for the light 13c is expulsion of methane from gas hydrates in the seafloor from pressure release during ice sheet retreat

the use of gps horizontals for loading studies with applications to northern california and southeast greenland received 23 august 2012 revised 15 january 2013 accepted 20 january 2013 published 25 april 2013 1 we describe how gps measurements of horizontal crustal motion can be used to augment vertical crustal motion measurements to improve and extend gps studies of surface loading we show that the ratio of the vertical displacement to the horizontal displacement combined with the direction of the horizontal motion can help determine whether nearby loading is concentrated in a small region for example in a single lake or glacier and where that region is we illustrate this method by applying it to two specific cases an analysis of gps data from northern california to monitor the level of lake shasta and the analysis of data from a single gps site in southeast greenland to determine mass variability of two large nearby outletglaciers helheim glacier and midgaard glacier the californiaexampleserves largely as a proof of concept where the results can be assessed by comparing with independent observations lake shasta tide gauge data in this case our greenland results show that both helheim and midgaard have experienced notable interannual variations in mass loss rate over the last decade helheim sm ass loss accelerated rapidly in mid 2003 decelerated in late 2005 and increased again in 2008 2009 before returning to about its pre 2003 rate in late 2010 midgaard s mass loss accelerated in mid 2004 and remained more or less constant before returning to its pre 2003 rate in late 2008

is methane driven deglaciation consistent with the ice core record the rapid climate changes at the terminations marking the end of the last glaciation are poorly understood this study uses the cambridge two dimensional atmospheric model to investigate the impact of a large marine sediment slump or permafrost rupture releasing 4000 tg of ch 4 into the high latitudes of the northern hemisphere with particular emphasis on the evolution of atmospheric ch 4 concentrations which may have led to an associated direct radiative effect of the order of 1 w m 2 persisting for a few decades because of enhanced levels of atmospheric ch4 the model generated ch 4 concentrations were converted into synthetic ice core signals for 66 n and 85 s representing arctic and antarctic cores respectively a range of possible averaging times was considered the results show that irrespective of the site or enclosure time chosen with the current sampling interval of 300 years it is not possible to discount completely the existence of a spike as a result of the instantaneous release of 4000 tg of ch 4 detection or refutation of a ch 4 spike would however be probable if the sampling interval were reduced to around 50 100 years

height profile of the mean velocity of an aeolian saltating cloud wind tunnel measurements by particle image velocimetry abstract the velocity of saltating particles is an important parameter in studying the aeolian sand movement we used particle image velocimetry to measure the variation with height of the mean particle velocity of a saltating cloud over a loose sand surface in a wind tunnel the results suggest that both the horizontal and vertical particle velocities fit the gaussian distribution well and that the mean particle velocity of a saltating cloud varies with wind velocity particle size and the height above bed the mean horizontal velocity is mainly the result of acceleration by the wind and increases with an increase in friction wind velocity but decreases with an increase in grain size because greater wind velocity causes more acceleration and finer particles are more easily accelerated at a given wind velocity it also increases with an increase in height by a power function in agreement with previous results obtained by other methods such as the high speed multi flash photographic method and particle dynamics analyzer pda reflecting first the increase in wind velocity with height through the boundary layer and second the longer trajectory particle path length increases with height and affords a longer time for acceleration by the wind an empirical model relating the mean horizontal particle velocity and height friction wind velocity as well as particle size is developed the ratio of the mean horizontal particle velocity to the clean wind velocity at the same height increases with height but decreases with grain size the magnitude of mean vertical velocity is much less one or two orders less compared with the mean horizontal velocity the average movement in the vertical direction of a saltating cloud is upward the mean vertical velocity is positive although the upward velocity of a saltating particle should decrease with height due to gravity the mean vertical upward velocity the average of both ascending and descending particles generally shows a tendency to increase with height it seems that at higher elevations the data are more and more dominated by the high flyers the underlying mechanism for the mean vertical velocity distribution patterns needs to be clarified by further study

climate driven deformation of the solid earth from grace and gps 1 grace data indicate large seasonal variations in gravity that are assumed to be related to climate driven fluxes of surface water seasonal redistribution of surface mass should deform the earth and our calculations using grace data suggest vertical deformations of 13 mm in the region of greatest flux the amazon river basin to test the grace gravity hydrology connection we analyzed gps data acquired from sites in this region after accounting for degree 1 variations not observable with grace we find that annual deformation measured with gps correlates highly with predictions calculated from grace measurements these results confirm the variations in surface water sensed by grace which are significantly larger than those predicted by some hydrology models the results also demonstrate that grace can be an important tool for monitoring deformation of the earth and suggest that combined analysis of grace and gps may be a useful approach for estimation of geocenter variations

improved methods for observing earth s time variable mass distribution with grace using spherical cap mascons we discuss several classes of improvements to gravity solutions from the gravity recovery and climate experiment grace mission these include both improvements in background geophysical models and orbital parameterization leading to the unconstrained spherical harmonic solution jpl rl05 and an alternate jpl rl05m mass concentration mascon solution benefitting from those same improvements but derived in surface spherical cap mascons the mascon basis functions allow for convenient application of a priori information derived from near global geophysical models to prevent striping in the solutions the resulting mass flux solutions are shown to suffer less from leakage errors than harmonic solutions and do not necessitate empirical filters to remove north south stripes lowering the dependence on using scale factors the global mean scale factor decreases by 0 17 to gain accurate mass estimates ocean bottom pressure obp time series derived from the mascon solutions are shown to have greater correlation with in situ data than do spherical harmonic solutions increase in correlation coefficient of 0 08 globally particularly in low latitude regions with small signal power increase in correlation coefficient of 0 35 regionally in addition to reducing the error rms with respect to the in situ data reduction of 0 37 cm globally and as much as 1 cm regionally greenland and antarctica mass balance estimates derived from the mascon solutions agree within formal uncertainties with previously published results computing basin averages for hydrology applications shows general agreement between harmonic and mascon solutions for large basins however mascon solutions typically have greater resolution for smaller spatial regions in particular when studying secular signals

does the oxidation of methane leave an isotopic fingerprint in the geologic record 1 pore water co2 and 13c data are presented for the dysoxic santa barbara and santa monica basins in an attempt to constrain the influence of methane oxidation on the pore water gradients and benthic foraminiferal 13c although these two basins are adjacent to one another santa barbara basin has steeper pore water co2 and 13c gradients methane oxidation could be contributing to the higher gradients in this basin the isotope mass balance for pore water co2 indicates however that the pore water gradients in the upper 2 cm of both basins are controlled only by the rate of photosynthate carbon oxidation and the rate of diffusion methane derived co2 has no discernable influence on pore water or carbonate 13c values at these sediment depths in either basin benthic foraminiferal species inhabiting different depth horizons in the top centimeter incorporate these steep isotopic gradients in their calcite tests and can be used therefore to reconstruct the history of carbon oxidation within the basins on the basis of these modern geochemical constraints a more likely explanation for the apparent 13c excursions recorded in the late pleistocene sediments from santa barbara basin involves enhanced carbon rain and carbon oxidation in the basin sediments rather than clathrate destabilization

a model for late quaternary methane ice core signals wetlands versus a shallow marine source 1 a three reservoir model with first order kinetics for methane records in the vostok antarctica and gisp2 greenland ice cores reproduces the sawtooth pattern and the maximum and minimum concentrations the model also returns an atmospheric methane relaxation time of 10 years for both cores which is the same as current estimates the characteristics of the source reservoirs are long relaxation times 33 3 and 100 ky and high initial methane concentrations 2500 and 7000 ppm for gisp2 and vostok respectively these characteristics are consistent with gas hydrate sources in shallow marine sediments but not with wetland sources which have insufficient storage capacity and low source strength

n2o and ch4 variations during the last glacial epoch insight into global processes 1 greenhouse gas measurements along polar ice cores provide important insight into the former composition of the atmosphere its natural variations and the responses to fast climatic changes in the past we present high resolution nitrous oxide n2o and methane ch4 records measured along two ice cores from central greenland covering part of marine isotope stages 3 and 4 in the last glacial epoch the n2o data confirm the hypothesis that n2o shows variations in phase to fast climatic changes observed in the northern hemisphere the so called dansgaard oeschger d o events variations exist not only for events with a long duration 1500 years and more but also for the shorter ones the comparison with ch4 unveils interesting differences between the response of ch4 and n2o to d o events while the average amplitudes of ch4 oscillations associated with d o events are similar to those of the northern hemisphere summer insolation the magnitude of the n2o concentration change instead correlates with the duration of the d o events the records give further insight into the timing of concentration changes at the beginning of d o events they show that for long lasting events the n2o concentration starts to increase before both the sharp increase in the ch4 concentration and the temperature reconstructed for greenland

the attenuation of fast atmospheric ch4 variations recorded in polar ice cores 1 to reconstruct fast atmospheric trace gas variations from polar ice cores it has to be considered that their amplitudes are attenuated during the enclosure process in the ice relevant processes for the attenuation are the molecular diffusion in the open pores of the firn column and the gradual bubble close off in the depth of the transition from firn to ice these processes depend mainly on temperature and accumulation rate and lead e g to a strong attenuation for cold sites with low accumulation rates with a diffusion and enclosure model it is possible to calculate the attenuation for a single event and to compare ice core records from different sites we investigate the atmospheric methane ch4 variation during the cold event 8200 years ago and calculate that its amplitude as recorded in the epica dome c ice core is attenuated to a magnitude between 34 and 59

atmospheric impacts and ice core imprints of a methane pulse from clathrates in relation to arctic warming the possible occurrence of methane hydrate degassing events has attracted an increasing interest in recent years we evaluate the atmospheric impact of rapid and massive emissions of methane and how they are imprinted in ice core records by combining for the first time models of atmospheric chemistry and trace gas transport in firn different emission characteristics as well as climatic conditions present pre industrial glacial are considered the d isotopic signatures characterizing stable isotopologues of methane dch3 and 13 ch4 are also analysed our results suggest little effect of clathrate degassing on the main methane oxidant oh radicals due to the relatively short atmospheric lifetime of methane the simulated clathrate induced perturbations last for less than a century this time scale is comparable to or shorter than the duration of air bubble closure in polar ice sheets as a consequence rapid methane perturbations in the atmosphere are strongly smoothed in ice core records this smoothing mostly depends on the snow accumulation rate at the site of ice core drilling we propose a methodology to identify a potential clathrate degassing event in ice core records continuous ch4 records from high accumulation rate sites could allow to decipher short time scale events d do f ch 4 should reveal a typical lying s shape at high accumulation rate sites reflecting the combined effects of the clathrate source signature negative excursion and subsequent oh fractionation in the atmosphere positive excursion the amplitude ratio of the negative and positive dd swings recorded in greenland and antarctica under similar accumulation rate conditions could also indicate the latitude of a clathrate degassing event

is methane venting at the seafloor recorded by δ13c of benthic foraminifera shells the research was supported by wcnurp grant pf806880 and by nsf grants oce 9731157 oce 9815186 and oce 9906944 curation of sediment cores at the osu norcor repository is supported by nsf

geophysical interpretation of observed geocenter variations geocenter variations are caused by mass redistribution within the earth system especially the atmosphere oceans and continental water using surface pressure fields and soil moisture and snow depth fields of the ncep ncar climate data assimilation system i cdas i 1 we estimate contributions from variations in atmospheric surface pressure and continental water storage to the earth s geocenter center of mass variation in addition sea surface anomalies determined by the topex poseidon altimeter are used to investigate geocenter variations resulting from ocean mass redistribution these sea surface height data were corrected using a simplified steric model a comparison with observed geocenter variations derived from lageos 1 and 2 satellite laser ranging data indicates that the atmosphere oceans and continental hydrological cycle all provide significant contributions at different frequencies geocenter variations estimated in this paper are in reasonably good agreement with results given by dong et al 1997 for atmospheric and ocean contributions but not for the estimates of continental hydrological contributions

horizontal motion in elastic response to seasonal loading of rain water in the amazon basin and monsoon water in southeast asia observed by gps and inferred from grace 1 we find seasonal horizontal crustal motions observed by gps positioning in elastic response to heavy rainfall in the amazon basin and to monsoons in southeast asia to be consistent with those inferred from gravity recovery and climate experiment grace gravity observations of water mass loading solid earth moves toward the amazon during heavy spring rainfall and toward southeast asia during summer monsoons and back away from these areas 6 months later when the water load is minimum vertical oscillations observed by gps and inferred from grace are 2 to 3 times larger than horizontal oscillation near the margins of the areas of large mass loading some discrepancies between gps and grace are probably caused by local effects that influence gps measurements because the gps sites that show significant discrepancies also do not match nearby gps sites however when the load is short wavelength the limited spatial resolution of grace can cause systematic misfits

deglacial methane emission signals in the carbon isotopic record of lake baikal changes in the concentrations of atmospheric greenhouse gases constitute an important part of global climate forcing here we present the first continental evidence for climatically caused changes in a methane gas hydrate reservoir the organic carbon stable isotope record from lake baikal during the past 130 000 years registers regular emissions of isotopically light carbon by the occurrence of distinct negative shifts of 3 5 at every major orbitally forced cold to warm climatic transition during the past 130 000 years including marine oxygen isotope stage boundaries 6 5e 5d 5c 5b 5a and 2 1 we conclude that these emissions were associated with decomposition of sedimentary clathrates widespread in the baikal basin among potential hypotheses to account for these methane episodes the most probable appears to be hydrate dissociation due to deglacial warming of lake water we estimate that as much as 12 33 tg of methane could have been released with each episode by recording the systematically recurring episodes of massive methane clathrate decomposition closely linked with the northern hemisphere temperatures during major orbital warmings the new baikal 13c record provides further evidence for the potential involvement of clathrate reservoir in rapid deglacial rises of atmospheric methane levels

source parameter inversion for recent great earthquakes from a decade long observation of global gravity fields we quantify gravity changes after great earthquakes present within the 10 year long time series of monthly gravity recovery and climate experiment grace gravity fields using spherical harmonic normal mode formulation the respective source parameters of moment tensor and double couple were estimated for the 2004 sumatra andaman earthquake the gravity data indicate a composite moment of 1 2 1023 n m with a dip of 10 in agreement with the estimate obtained at ultralong seismic periods for the 2010 maule earthquake the grace solutions range from 2 0 to 2 7 1022 n m for dips of 12 24 and centroid depths within the lower crust for the 2011 tohoku oki earthquake the estimated scalar moments range from 4 1 to 6 1 1022 n m with dips of 9 19 and centroid depths within the lower crust for the 2012 indian ocean strike slip earthquakes the gravity data delineate a composite moment of 1 9 1022 n m regardless of the centroid depth comparing favorably with the total moment of the main ruptures and aftershocks the smallest event we successfully analyzed with grace was the 2007 bengkulu earthquake with m0 5 0 1021 n m we found that the gravity data constrain the focal mechanism with the centroid only within the upper and lower crustal layers for thrust events deeper sources i e in the upper mantle could not reproduce the gravity observation as the larger rigidity and bulk modulus at mantle depths inhibit the interior from changing its volume thus reducing the negative gravity component focal mechanisms and seismic moments obtained in this study represent the behavior of the sources on temporal and spatial scales exceeding the seismic and geodetic spectrum

a new global mode of earth deformation seasonal cycle detected we have detected a global mode of earth deformation that is predicted by theory precise positioning of global positioning system sites distributed worldwide reveals that during february to march the northern hemisphere compresses and the southern hemisphere expands such that sites near the north pole move downward by 3 0 millimeters and sites near the equator are pulled northward by 1 5 millimeters the opposite pattern of deformation occurs during august to september we identify this pattern as the degree one spherical harmonic response of an elastic earth to increased winter loading of soil moisture snow cover and atmosphere data inversion shows the load moment s trajectory as a great circle traversing the continents peaking at 6 9 1022 kilogram meters near the north pole in winter indicating interhemispheric mass exchange of 1 0 1016 0 2 1016 kilograms

glacial interglacial wetland biomass burning and geologic methane emissions constrained by dual stable isotopic ch4 ice core records atmospheric methane ch4 records reconstructed from polar ice cores represent an integrated view on processes predominantly taking place in the terrestrial biogeosphere here we present dual stable isotopic methane records 13ch4 and d ch4 from four antarctic ice cores which provide improved constraints on past changes in natural methane sources our isotope data show that tropical wetlands and seasonally inundated floodplains are most likely the controlling sources of atmospheric methane variations for the current and two older interglacials and their preceding glacial maxima the changes in these sources are steered by variations in temperature precipitation and the water table as modulated by insolation local sea level and monsoon intensity based on our d ch4 constraint it seems that geologic emissions of methane may play a steady but only minor role in atmospheric ch4 changes and that the glacial budget is not dominated by these sources superimposed on the glacial interglacial variations is a marked difference in both isotope records with systematically higher values during the last 25 000 y compared with older time periods this shift cannot be explained by climatic changes rather our isotopic methane budget points to a marked increase in fire activity possibly caused by biome changes and accumulation of fuel related to the late pleistocene megafauna extinction which took place in the course of the last glacial

hydrological deformation induced by the west african monsoon comparison of gps grace and loading models three dimensional ground deformation measured with permanent gps stations in west africa was used for investigating the hydrological loading deformation associated with monsoon precipitation the gps data were processed within a global network for the 2003 2008 period weekly station positions were retrieved with a repeatability including unmodeled loading effects of 1 2 mm in the horizontal components and between 2 5 and 6 mm in the vertical component the annual signal in the vertical component for sites located between 9 6n and 16 7n is in the range 10 15 mm it is consistent at the 3 mm level with the annual regional scale loading deformations estimated from grace satellite products and modeled with a combination of hydrological atmospheric and nontidal oceanic models an additional 6 month transient signal was detected in the vertical component of gps estimates at most of the west african sites it takes the form of an oscillation occurring between september and march and reaching a maximum amplitude of 12 16 mm at ouagadougou 12 5n the analysis of in situ hydro geological data revealed a strong coincidence between this transient signal and peak river discharge at three sites located along the niger river timbuktu gao and niamey at ouagadougou a similar coincidence was found with the seasonal variations of the water table depth we propose a mechanism to account for this signal that involves a sequence of swelling shrinking of clays combined with local loading effects associated with flooding of the niger river

modeling the densification of polar firn including heat diffusion application to close off characteristics and gas isotopic fractionation for antarctica and greenland sites 1 modeling the densification of polar firn is essential to estimate variations of close off characteristics density close off depth delta age in relation with past climate parameters temperature and accumulation rates furthermore the air composition in the firn is modified by gravitational and thermal fractionation and stable isotope measurements of permanent gases like nitrogen or argon can provide information on the amplitude of these fractionations in this work we propose a new model coupling firn densification and heat diffusion in addition to the determination of the firn thickness and gas ice age differences the model allows a reconstruction of the time evolution of the temperature for different sites in antarctica vostok and greenland gisp2 and therefore the evolution of gravitational and thermal isotopic fractionations in firn under present day conditions the modeled profiles are in good agreement with the available temperature measurements in firn for sites with low accumulation rates such as vostok the results show the existence of temperature gradients in the firn column even when no rapid climatic changes occur the comparison of the modeled 15n results to measurements allows to better constrain the 18o temperature relationship used to infer the surface temperature history and for gisp2 the model validates the long term borehole based temperature

troposphere mapping functions for gps and very long baseline interferometry from european centre for medium range weather forecasts operational analysis data 1 in the analyses of geodetic very long baseline interferometry vlbi and gps data the analytic form used for mapping of the atmosphere delay from zenith to the line of site is most often a three parameter continued fraction in 1 sin elevation using the 40 years reanalysis era 40 data of the european centre for medium range weather forecasts for the year 2001 the b and c coefficients of the continued fraction form for the hydrostatic mapping functions have been redetermined unlike previous mapping functions based on data from numerical weather models isobaric mapping functions niell 2000 and vienna mapping functions vmf boehm and schuh 2004 the new c coefficients are dependent on the day of the year and unlike the niell mapping functions niell 1996 they are no longer symmetric with respect to the equator apart from the opposite phase for the two hemispheres compared to vmf this causes an effect on the vlbi or gps station heights that is constant and as large as 2 mm at the equator and that varies seasonally between 4 mm and 0 mm at the poles the updated vmf based on these new coefficients and called vmf1 hereinafter yields slightly better baseline length repeatabilities for vlbi data the hydrostatic and wet mapping functions are applied in various combinations with different kinds of a priori zenith delays in the analyses of all vlbi international vlbi service for geodesy and astrometry ivs r1 and ivs r4 24 hour sessions of 2002 and 2003 the investigations concentrate on baseline length repeatabilities as well as on absolute changes of station heights

implications of reduced turbidity current and landslide activity for the initial eocene thermal maximum evidence from two distal deep water sites previous studies propose that submarine landslides and turbidity currents may become more likely due to future rapid global warming determining whether global warming increases likelihood assists in assessment of landslide triggered tsunami hazards and risk to seafloor structures other studies propose that landslides helped to trigger past rapid climate change due to sudden release of gas hydrates two deep water turbidite records show prolonged hiatuses in turbidity current activity during the initial eocene thermal maximum ietm at 55 ma the ietm represents a possible proxy for future anthropogenically induced climate change it is likely that our records mainly represent large and fast moving disintegrative submarine landslides statistical analysis of long term 2 3 myr records shows that turbidity current frequency significantly decreased after the ietm our results indicate that rapid climate change does not necessarily cause increased turbidity current activity and do not provide evidence for landslides as a primary trigger for the ietm

ongoing drought induced uplift in the western united states the western united states has been experiencing severe drought since 2013 the solid earth response to the accompanying loss of surface and near surface water mass should be a broad region of uplift we use seasonally adjusted time series from continuously operating gps stations to measure this uplift which we invert to estimate mass loss the median uplift is 4 mm with values up to 15 mm in california s mountains the associated pattern of mass loss which ranges up to 50 cm of water equivalent is consistent with observed decreases in precipitation and streamflow we estimate the total deficit to be about 240 gt equivalent to a 10 cm layer of water over the entire region or the annual mass loss from the greenland ice sheet

high resolution holocene n2o ice core record and its relationship with ch4 and co2 1 nitrous oxide n 2 o concentration records exist for the last 1000 years and for time periods of rapid climatic changes like the transition from the last glacial to today s interglacial and for one of the fast climate variations during the last ice age little is known however about possible n 2 o variations during the more stable climate of the present interglacial holocene spanning the last 11 thousand years here we fill this gap with a high resolution n 2 o record measured along the european project for ice coring in antarctica epica dome c antarctic ice core on the same ice we obtained high resolution methane and carbon dioxide records this provides the unique opportunity to compare variations of the three most important greenhouse gases after water vapor without any uncertainty in their relative timing the co 2 and ch 4 records are in good agreement with previous measurements on other ice cores the n 2 o concentration started to decrease in the early holocene and reached minimum values around 8 ka 260 ppbv before a slow increase to its preindustrial concentration of 265 ppbv

inversion of earth s changing shape to weigh sea level in static equilibrium with surface mass redistribution 1 we develop a spectral inversion method for mass redistribution on the earth s surface given geodetic measurements of the solid earth s geometrical shape using the elastic load love numbers first spectral coefficients are geodetically estimated to some degree spatial inversion then finds the continental surface mass distribution that would force geographic variations in relative sea level such that it is self consistent with an equipotential top surface and the deformed ocean bottom surface and such that the total ocean plus continental mass load has the same estimated spectral coefficients applying this theory we calculate the contribution of seasonal interhemispheric degree 1 mass transfer to variation in global mean sea level and nonsteric static ocean topography using published gps results for seasonal degree 1 surface loading from the global igs network our inversion yields ocean continent mass exchange with annual amplitude 2 92 0 14 1015 kg and maximum ocean mass on 25 august 3 days after correction for the annual variation in global mean vertical deformation of the ocean floor 0 4 mm amplitude we find geocentric sea level has an amplitude of 7 6 0 4 mm consistent with topex poseidon results minus steric effects the seasonal variation in sea level at a point strongly depends on location ranging from 3 to 19 mm the largest being around antarctica in mid august seasonal gradients in static topography have amplitudes of up to 10 mm over 5000 km which may be misinterpreted as dynamic topography peak continental loads occur at high latitudes in late winter at the water equivalent level of 100 200 mm

linking continental slope failures and climate change testing the clathrate gun hypothesis it has been suggested that the release of clathrates rather than expansion of wetlands is the primary cause of the rapid increases observed in the ice core atmospheric methane record during the pleistocene because submarine sediment failures can involve as much as 5000 gt of sediment and have the capacity to release vast quantities of methane hydrates one of the major tests of the clathrate gun hypothesis is determining whether the periods of enhanced continental slope failure and atmospheric methane correlate to test the clathrate gun hypothesis we have collated published dates for submarine sediment failures in the north atlantic sector and correlated them with climatic change for the past 45 k y more than 70 by volume of continental slope failures during the past 45 k y was displaced in two periods between 15 and 13 ka and between 11 and 8 ka both these intervals correlate with rising sea level and peaks in the methane record during the bolling allerod and preboreal periods these data support the clathrate gun hypothesis for glacial interglacial transitions the data do not however support the clathrate gun hypothesis for glacial millennial scale climate cycles because the occurrence of sediment failures correlates with heinrich events i e lows in sea level and atmospheric methane a secondary use of this data set is the insight into the possible cause of continental slope failures glacial period slope failures occur mainly in the low latitudes and are associated with lowering sea level this finding suggests that reduced hydrostatic pressure and the associated destabilization of gas hydrates may be the primary cause the bolling allerod sediment failures were predominantly low latitude suggesting an early tropical response to deglaciation e g enhanced precipitation and sediment load to the continental shelf or warming of intermediate waters in contrast sediment failures during the preboreal period and the majority of the holocene occurred in the high latitudes suggesting either isostatic rebound related earthquake activity or reduced hydrostatic pressure caused by isostatic rebound causing destabilization of gas hydrates

the end of the ice age methane gas hydrates may have contributed to the rapid rise in atmospheric ch4 co2 and global temperatures at the end of the last major glaciation about 13 500 years ago given suitable orbital conditions and insolation at high latitude a small triggering event such as the release of one or more arctic gas pools may have initiated massive release of methane from hydrate under ice and in permafrost the consequent greenhouse warming would have provided strong positive feedback amplifying emission this warming driven by ch4 may have induced the release of co2 from the oceans to the biosphere stabilizing the interglacial carbon cycle

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

molecular and stable isotope compositions of natural gas hydrates a revised global dataset and basic interpretations in the context of geological settings abstract a global dataset of molecular and stable isotope compositions of gases released from 209 different specimens of natural gas hydrate is presented and discussed the 26 hydrate bearing areas from 21 geographic regions are grouped into high gas flux hgf settings low gas flux lgf settings and hydrated gas accumulations hga methane ch4 is the most abundant hydrate bound gas while co2 and c2 hydrocarbon gases are frequently present in small amounts non hydrocarbon gases such as h2s are uncommon the stable isotope composition of hydrate bound gases varies significantly e g 13c of ch4 from 74 7 to 39 6 suggesting that gases of both microbial and thermogenic origin form gas hydrates hydrate bound gases are derived from autochthonous located predominantly within the gas hydrate stability zone ghsz and allochthonous located in deep sediments sources the occurrence and concentration of gas hydrates in sediments are controlled not by the origin of gases but rather by their sources which in turn strongly depend on geological setting allochthonous gases microbial and or thermogenic dominate in hgf and hga settings where they are focused in the shallow ghsz along faults within mud volcanoes in permeable carrier beds and other geological features from underlying petroleum systems relatively high concentrations of gas hydrate average 5 15 of pores and locally up to 100 of volume occurring over small areas are typical of hgf and hga settings in contrast autochthonous and diffuse allochthonous gases mostly microbial occur in stratigraphically and structurally simple lgf settings and result in relatively low concentrations of gas hydrate average 2 of pores in the ghsz spread over large areas the major implication of this finding is that successful prediction of resource and geohazard potential of gas hydrates is possible only if regional petroleum systems extending well below the ghsz are properly evaluated in addition to the diagnosis of origins and sources of hydrate bound gases molecular and isotopic data help to better identify hydrate bearing intervals and provide valuable insights into the dynamics of hydrate bearing sites

evidence against clathrate derived methane release to santa barbara basin surface waters 1 the clathrate gun hypothesis suggests that methane from the marine sedimentary gas hydrate reservoir was episodically released into the atmosphere where it generated rapid atmospheric warming that drove late quaternary abrupt millennial scale climate change brief large negative 13c excursions recorded by planktonic up to 3 and benthic up to 5 foraminifera from santa barbara basin sediments have been interpreted as evidence of clathrate derived methane release to surface waters during or immediately before marine isotope stage mis 3 interstadials molecular biomarkers from the 13c excursion horizons have been interpreted to support this scenario however recent work at modern methane seeps show that fossil specimens can be contaminated with authigenic overgrowths or calcite replacement that may be difficult to detect through microscopy the possibility that planktonic specimens are contaminated and thus their 13c values not a primary signal warrants further inquiry we generated a high resolution continuous total organic carbon toc 13c record from fortuitously obtained samples across the younger foraminiferal 13c excursion during interstadial 8 the record exhibits variations similar in magnitude and timing to those that occurred in the basin over the last 600 years furthermore previously published toc 13c values of discreet samples from this and the three other mis 3 foraminiferal 13c excursions are also similar to recent values although there are factors that could obscure a surface water methane signal in the toc 13c record these results question the interpretation that methane was released to surface waters an alternative hypothesis to explain the available data is that the foraminiferal 13c excursions are an artifact of diagenetic processes at or below the sediment water interface this interpretation may be compatible with the molecular biomarker data further work is necessary to differentiate between the two hypotheses

assessing methane release from the colossal storegga submarine landslide 1 marine slope failure involving methane gas hydrate bearing sediments is one mechanism for releasing enormous quantities of methane to the ocean and atmosphere the storegga slide on the norwegian margin is the largest known holocene aged continental margin slope failure complex and is believed to have occurred in sediments that may have initially contained gas hydrate here we report pore water sulfate gradient measurements that are used as a proxy for the relative amounts of methane that exist in continental margin sediments associated with the colossal storegga slide these measurements suggest that a considerable inventory of methane occurs in sediments adjacent to and unaffected by the storegga slide events but indicate that methane is notably absent from sediments on the sole of the slide and distal deposits created by the slide events either methane was lost during previous pleistocene failure events or was never present in significant concentrations within the sediments that failed

the ice age methane budget 1 accounting for the natural 40 reduction in methane during the last glacial maximum lgm represents one of the most challenging problems posed by polar ice core studies inverse modelling constrained by observations suggest it is driven by a decline in wetland sources but this is not supported by forward modelling using a comprehensive earth system model we show that closure of the methane budget requires reduced emissions and an amplified sink caused by reduction in emissions of volatile organic compounds vocs from lgm forests our study emphasizes a key role for the terrestrial biosphere in the methane budget during the quaternary