warming of global abyssal and deep southern ocean waters between the 1990s and 2000s contributions to global heat and sea level rise budgets abyssalglobalanddeepsouthern oceantemperature trendsarequantifiedbetweenthe1990sand2000sto assesstheroleofrecentwarmingoftheseregionsin globalheatandsealevelbudgets theauthors1 compute warming rates with uncertainties along 28 full depth high quality hydrographic sections that have been occupied two or more times between 1980 and 2010 2 divide the global ocean into 32 basins defined by the topography and climatological ocean bottom temperatures and then 3 estimate temperature trends in the 24 sampled basins the three southernmost basins show a strong statistically significant abyssal warming trend with that warming signal weakening to the north in the central pacific western atlantic and eastern indian oceans eastern atlantic and western indian ocean basins show statistically insignificant abyssal cooling trends excepting the arctic ocean and nordic seas the rate of abyssal below 4000 m global ocean heat content change in the 1990s and 2000s is equivalent to a heat flux of 0 027 60 009 w m 22 applied over the entire surface of the earth deep 1000 4000 m warming south of the subantarctic front of the antarctic circumpolar current adds 0 068 60 062 w m 22 the abyssal warming produces a 0 053 60 017 mm yr 21 increase in global average sea level and the deep warming south of the subantarctic front adds another 0 093 60 081 mm yr 21 thus warmingin theseregions ventilatedprimarilyby antarcticbottomwater accounts for a statistically significant fraction of the present global energy and sea level budgets

predicted bounds on peak global mean sea level during marine isotope stages 5a and 5c abstract estimates of marine isotope stage mis 5c and 5a global mean sea level gmsl based on marine terraces and coastal indicators range from 15 37 m and 9 30 m below present respectively tectonic displacement and glacial isostatic adjustment gia complicate efforts to refine this range we revisit this issue using numerical predictions of post glacial sea level change and updated estimates of site specific tectonic signals based upon these predictions laurentide and cordilleran peripheral bulge dynamics and variations in the gravitational effect of these ice masses dominate the gia signal along the east and west coasts of north america published compilations suggest that mis 5 sea level indicators extending from virginia to the caribbean lie on the outer flank of the peripheral bulge while those along a transect from oregon to baja california sit on the inner flank of the bulge our gia modeling reconciles these data by adopting a significantly weaker i e lower viscosity upper mantle in analyzing data on the pacific coast relative to the atlantic an inference supported by seismic tomography we present a sensitivity analysis that compares the observed elevation of globally distributed high stand markers to a suite of gia simulations that vary the earth model and gmsl from the last interglaciation mis 5e 130 115 ka to 70 ka we conclude that gmsl peaked at 8 5 4 6 m 1 during mis 5a and 9 4 5 3 m during mis 5c a more restrictive analysis yields slightly wider bounds corresponding to 10 5 5 5 m and 11 1 6 6 m respectively

preliminary analysis of acceleration of sea level rise through the twentieth century using extended tide gauge data sets august 2014 this work explores the potential for extending tide gauge time series from the permanent service for mean sea level psmsl using historical documents psmsl ancillary data and by developing additional composite time series using near neighbor tide gauges the aim was to increase the number completeness and geographical extent of records covering most or all of the twentieth century the number of at least 75 complete century scale time series have been approximately doubled over the original psmsl data set in total over 4800 station years have been added with 294 of these added to 10 long southern hemisphere records individual century scale acceleration values derived from this new extended data set tend to converge on a value of 0 01 0 008 mm yr2 this result agrees closely with recent work and is statistically significant at the 1 sigma level possible causes of acceleration and errors are briefly discussed results confirm the importance of current data archeology projects involving digitization of the remaining archives of hard copy tide gauge data for sea level and climate studies

inference of mantle viscosity from grace and relative sea level data summary gravity recovery and climate experiment grace satellite observations of secular changes in gravity near hudson bay and geological measurements of relative sea level rsl changes over the last 10 000 yr in the same region are used in a monte carlo inversion to infer mantle viscosity structure the grace secular change in gravity shows a significant positive anomaly over a broad region 3000 km near hudson bay with a maximum of 2 5 gal yr 1 slightly west of hudson bay the pattern of this anomaly is remarkably consistent with that predicted for postglacial rebound using the ice 5g deglaciation history strongly suggesting a postglacial rebound origin for the gravity change we find that the grace and rsl data are insensitive to mantle viscosity below 1800 km depth a conclusion similar to that from previous studies that used only rsl data for a mantle with homogeneous viscosity the grace and rsl data require a viscosity between 1 4 1021 and 2 3 1021 pa s an inversion for two mantle viscosity layers separated at a depth of 670 km shows an ensemble of viscosity structures compatible with the data while the lowest misfit occurs for upper and lower mantle viscosities of 5 3 1020 and 2 3 1021 pa s respectively a weaker upper mantle may be compensated by a stronger lower mantle such that there exist other models that also provide a reasonable fit to the data we find that the grace and rsl data used in this study cannot resolve more than two layers in the upper 1800 km of the mantle

ellipsoidal correction in grace surface mass change estimation the earth s shape is much closer to an ellipsoid than a sphere the commonly used spherical approximation in mass change inversion is expected to cause bias by the spherical harmonic sh solutions from gravity recovery and climate experiment grace especially in high latitude regions where significant present day ice losses occur this bias or ellipsoidal correction reaches up to 8 from the evaluation by simulations based on synthetic mass change rate models further evaluation using 14 plus years of grace monthly sh solutions from april 2002 to december 2016 indicates that the ellipsoidal correction is also noticeable in the total mass change time series over polar regions before and after the ellipsoidal correction the estimated linear rates from mass change time series differ by 4 3 4 7 5 2 5 7 and 6 6 for five selected regions over greenland antarctic peninsula ap amundsen sea embayment ase alaska glacier and svalbard islands respectively although with amplitudes likely below the current grace s uncertainty level these differences are consistently negative over the five regions this indicates that the spherical approximation leads to systematic underestimation for polar mass change rates thus the ellipsoidal correction needs to be considered for more precise mass recovery with grace sh solutions it also depends on spatial scales of mass change signals the smaller the spatial scale the larger the correction to more reliably estimate high latitude surface mass changes by grace sh solutions the ellipsoidal correction is recommended especially for ice loss signals over polar regions

global thermosteric sea level change contributed by the deep ocean below 2000 m estimated by argo and ctd data abstract due to an insufficient amount of observational data little is known about the temperature variation in the global abyssal ocean and its contribution to sea level change in this study we estimated the monthly seawater temperature below 2000 m from 2005 2015 by combining array for real time geostrophic oceanography argo and conductivity temperature depth ctd data for this purpose we divided the global ocean into 38 regions according to the ctd temperature profile properties for each region we used ctd data to construct a mathematical model to describe the relation of temperatures between 1000 2000 m and those below 2000 m we then used this mathematical model and the argo data to reconstruct the temperature profile below 2000 m and evaluate its thermostatic contribution to sea level change we discovered that the deep ocean below 2000 m contributed 0 12 0 03 mm yr to the mean global thermosteric sea level rise from 2005 2015 our result was confirmed by geodetic observations i e the rate of thermosteric sea level rise calculated using altimeter gravity recovery and climate experiment grace and argo data was approximately 0 15 0 41 mm yr the contribution of each ocean layer generally decreased with depth and there was an obvious fluctuation between approximately 4000 5000 m interpreted as being caused by geothermal heating of the ocean floor

closing the sea level rise budget with altimetry argo and grace 1 an analysis of the steric and ocean mass components of sea level shows that the sea level rise budget for the period january 2004 to december 2007 can be closed using corrected and verified jason 1 and envisat altimetry observations of total sea level upper ocean steric sea level from the argo array and ocean mass variations inferred from grace gravity mission observations we find that the sum of steric sea level and the ocean mass component has a trend of 1 5 1 0 mm a over the period in agreement with the total sea level rise observed by either jason 1 2 4 1 1 mm a or envisat 2 7 1 5 mm a within a 95 confidence interval

a reconciled estimate of ice sheet mass balance we combined an ensemble of satellite altimetry interferometry and gravimetry data sets using common geographical regions time intervals and models of surface mass balance and glacial isostatic adjustment to estimate the mass balance of earth s polar ice sheets we find that there is good agreement between different satellite methods especially in greenland and west antarctica and that combining satellite data sets leads to greater certainty between 1992 and 2011 the ice sheets of greenland east antarctica west antarctica and the antarctic peninsula changed in mass by 142 49 14 43 65 26 and 20 14 gigatonnes year 1 respectively since 1992 the polar ice sheets have contributed on average 0 59 0 20 millimeter year 1 to the rate of global sea level rise

increasing rates of ice mass loss from the greenland and antarctic ice sheets revealed by grace 1 we use monthly measurements of time variable gravity from the grace gravity recovery and climate experiment satellite gravity mission to determine the ice mass loss for the greenland and antarctic ice sheets during the period between april 2002 and february 2009 we find that during this time period the mass loss of the ice sheets is not a constant but accelerating with time i e that the grace observations are better represented by a quadratic trend than by a linear one implying that the ice sheets contribution to sea level becomes larger with time in greenland the mass loss increased from 137 gt yr in 2002 2003 to 286 gt yr in 2007 2009 i e an acceleration of 30 11 gt yr2 in 2002 2009 in antarctica the mass loss increased from 104 gt yr in 2002 2006 to 246 gt yr in 2006 2009 i e an acceleration of 26 14 gt yr2 in 2002 2009 the observed acceleration in ice sheet mass loss helps reconcile grace ice mass estimates obtained for different time periods

interpretation of an aeromagnetic survey of the african red sea shelf and coastal strip between 23 6 and 25 n abstract aeromagnetic data interpretation in the southern egyptian part of the african red sea shelf and its coastal strip was made the data suggest that this shelf can be divided into two sections a southern section of rifting oceanic crust of thickness comparable to that of oceanic layer 2 and a northern one of continental crust apparently subjected to basic volcanicity related to initial red sea rifting seafloor spreading in the southern section is shown as continuous for 13 m y commencing 22 m y ago and may have taken place under the evaporite cover an argument which may be supported by available borehole data aeromagnetic anomalies in the northern section may illustrate the juxtaposition of basic magma incident to initial rifting with shield rocks the coastal strip aeromagnetic anomalies are likely due to the well known and widespread basic volcanicity prevalent in eastern egypt in the oligocene and early miocene and which may have preceeded the actual red sea rifting

ongoing glacial isostatic contributions to observations of sea level change studies determining the contribution of water fluxes to sea level rise typically remove the ongoing effects of glacial isostatic adjustment gia unfortunately use of inconsistent terminology between various disciplines has caused confusion as to how contributions from gia should be removed from altimetry and grace measurements in this paper we review the physics of the gia corrections applicable to these measurements and discuss the differing nomenclature between the gia literature and other studies of sea level change we then examine a range of estimates for the gia contribution derived by varying the earth and ice models employed in the prediction we find similar to early studies that gia produces a small compared to the observed value but systematic contribution to the altimetry estimates with a maximum range of 0 15 to 0 5 mm yr 1 moreover we also find that the gia contribution to the mass change measured by grace over the ocean is significant in this regard we demonstrate that confusion in nomenclature between the terms absolute sea level and geoid has led to an overestimation of this contribution in some previous studies a component of this overestimation is the incorrect inclusion of the direct effect of the contemporaneous perturbations of the rotation vector which leads to a factor of two larger value of the degree two order one spherical harmonic component of the model results aside from this confusion uncertainties in earth model structure and ice sheet history yield a spread of up to 1 4 mm yr 1 in the estimates of this contribution however even if the ice and earth models were perfectly known the processing techniques used in grace data analysis can introduce variations of up to 0 4 mm yr 1 thus we conclude that a single valued gia correction is not appropriate for sea level studies based on gravity data each study must estimate a bound on the gia correction consistent with the adopted data analysis scheme

satellite gravity measurements confirm accelerated melting of greenland ice sheet using time variable gravity measurements from the gravity recovery and climate experiment grace satellite mission we estimate ice mass changes over greenland during the period april 2002 to november 2005 after correcting for the effects of spatial filtering and limited resolution of grace data the estimated total ice melting rate over greenland is 239 23 cubic kilometers per year mostly from east greenland this estimate agrees remarkably well with a recent assessment of 224 41 cubic kilometers per year based on satellite radar interferometry data grace estimates in southeast greenland suggest accelerated melting since the summer of 2004 consistent with the latest remote sensing measurements

linking tephrochronology and soil characteristics in the sila and nebrodi mountains italy recent studies have demonstrated that soils formed on pyroclastic ash deposits are much more common in the mediterranean area than previously assumed these soils are an important key to understanding past volcanic events and landscape evolution chronological information in soils of quaternary volcanic events however remains still poorly understood in southern italy using a multi method forensic approach we explore the origin and age of volcanic deposits soils in sicily and calabria the geochemical signature of the soil was compared to the chemical fingerprint of the magmas of potential source areas of southern italian volcanoes the results indicate that the investigated soils on the nebrodi sicily and sila calabria mountains were both impacted by materials having a high k calc alkaline series volcanism the aeolian islands in particular lipari and vulcano are the most likely source of origin but contributions also from the etna particularly the biancavilla ignimbrites and plinian eruptions occurred weathering and leaching processes along with a potential contribution from the underlying non volcanic bedrock has altered the main chemical composition of soils often precluding direct relation to potential source areas immobile elements and their ratios e g the nb y vs zr ti plot or trace elements co th and rare earth elements laser ablation icp ms analyses of glass particles volcanic clasts and pumice like materials gave precious hints of the origin of the volcanic deposits radiocarbon dating of the h2o2 resistant soil organic fraction indicates a minimum age of 8 10 ka of the soils the weathering index wip weathering index according to parker and the chemical composition of volcanic glasses and clasts were tested as proxies for the age of the volcanic deposits and time for soil formation the soils and landscape are characterised by multiple volcanic depositional phases for the last about 50 ka in the sila mountains and about 70 ka or more in the nebrodi mountains chemical mineralogical analyses enabled the detection of deposition phases during the pleistocene and also holocene the multi method approach enabled the identification of potential source areas provided a tentative age estimate of the start and in part duration of ash deposits and therefore improved our understanding of volcanic landscape evolution

computations of the viscoelastic response of a 3 d compressible earth to surface loading an application to glacial isostatic adjustment in antarctica and canada s u m m a r y we develop a 3 d finite element model to study the viscoelastic response of a compressible earth to surface loads the effects of centre of mass motion polar wander feedback and selfconsistent ocean loading are implemented to assess the model s accuracy we benchmark the numerical results against a semi analytic solution for spherically symmetric structure we force our model with the ice 5g global ice loading history to study the effects of laterally varying viscosity structure on several glacial isostatic adjustment gia observables including relative sea level rsl measurements incanada and present day time variable gravity and uplift rates in antarctica canadian rsl observations have been used to determine the earth s globally averaged viscosity profile antarcticgps uplift rates have been used to constrainantarcticgia models and gia time variable gravity and uplift signals are error sources for grace and altimeter estimates of present day antarctic ice mass loss and must be modelled and removed from those estimates computinggia results for a 3 d viscosity profile derived from a realistic seismic tomography model and comparing with results computed for 1 d averages of that 3 d profile we conclude that 1 a gia viscosity model based on canadian relative sea level data is more likely to represent a canadian average than a true global average 2 the effects of 3 d viscosity structure on grace estimates of present day antarctic mass loss are probably smaller than the difference between gia models based on different antarctic deglaciation histories and 3 the effects of 3 d viscosity structure on antarctic gps observations of present day uplift rate can be significant and can complicate efforts to use gps observations to constrain 1 d gia models

time variable gravity from space and present day mass redistribution in theearth system abstract since 2002 the us german grace gravity recovery and climate experiment mission has been providing a precise survey of earth s time variable gravity field with unprecedented temporal and spatial sampling grace time variable gravity fields provide a means of measuring temporal and spatial variations of mass redistribution within the earth system the grace mission has launched a new era in studying a series of geophysical problems ranging from deep earth structure to tracking mass redistribution on and near the surface of the earth grace has greatly improved understanding of mass redistribution in various compartments of the climate system atmosphere oceans terrestrial water and cryosphere in this review we use examples to show how grace has fundamentally enriched a number of fields including but not limited to the global water cycle and land hydrology mass balance of polar ice sheets and mountain glaciers ocean mass and global sea level change and solid earth geophysics

combining altimeter and subsurface float data to estimate the time averaged circulation in the upper ocean 1 a new technique is presented for estimating time averaged upper ocean geostrophic velocity from a combination of altimeter data and subsurface float data the technique makes uses of the strong relationship between sea surface height anomaly and anomalous velocity at depth to reduce mesoscale eddy variability in subsurface float displacements the technique is demonstrated on a region in the north atlantic that was well sampled by argo floats the 2004 through 2006 time averaged density field was estimated from the surface to 2000 db by combining altimeter and hydrographic data from the floats in addition a reference velocity field was estimated at 1000 db based on a combination of altimeter data and subsurface float displacements the reference velocity field was combined with geostrophic shear based on the density field to produce a three dimensional estimate of geostrophic velocity from the surface to 2000 db the gulf stream transport in the upper 2000 db is estimated to be 76 sv at 73 w in addition an estimate of the 3 year average dynamic height at the surface was computed by combining the 1000 db reference dynamic height and the time averaged density field

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

a 20th century acceleration in global sea level rise 1 multi century sea level records and climate models indicate an acceleration of sea level rise but no 20th century acceleration has previously been detected a reconstruction of global sea level using tide gauge data from 1950 to 2000 indicates a larger rate of rise after 1993 and other periods of rapid sea level rise but no significant acceleration over this period here we extend the reconstruction of global mean sea level back to 1870 and find a sea level rise from january 1870 to december 2004 of 195 mm a 20th century rate of sea level rise of 1 7 0 3 mm yr 1 and a significant acceleration of sea level rise of 0 013 0 006 mm yr 2 this acceleration is an important confirmation of climate change simulations which show an acceleration not previously observed if this acceleration remained constant then the 1990 to 2100 rise would range from 280 to 340 mm consistent with projections in the ipcc tar

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

closure of the budget of global sea level rise over the grace era the importance and magnitudes of the required corrections for global glacial isostatic adjustment abstract the budget of global sea level rise includes contributions from several distinct factors including thermosteric effects the wasting of small ice sheets and glaciers and the loss of mass by the great polar ice sheets and by the continents due to desiccation since the former contribution may be estimated on the basis of both hydrographic survey data and more recently using argo float data the second may be estimated on the basis of mass balance measurements on existing ice fields and the latter on the basis of modern grace based time dependent gravity field measurements the inputs to the globally averaged rate of sea level rise may be directly constrained since grace also provides a measurement of the rate at which mass is being added to the oceans we are now in a position to ask whether this rate of mass addition to the oceans matches the rate at which mass is being removed from the continents as demonstrated herein the mass component of the budget of global sea level is closed within the observational errors when the mass derived contribution is added to the thermosteric contribution it is furthermore shown that the inference of the net rate of global sea level rise by the altimetric satellites topex poseidon and jason 1 is also reconcilable over the grace era it is noted those individual terms in the budget especially the contribution from small ice sheets and glaciers remains insufficiently accurate it is demonstrated that the lingering influence of the late quaternary ice age upon sea level is profound and that closure of the budget requires an accurate model of its impact

ocean mass from grace and glacial isostatic adjustment 1 we examine geoid rates and ocean mass corrections from two published global glacial isostatic adjustment gia models both of which have been used in previous studies to estimate ocean mass trends from gravity recovery and climate experiment grace satellite gravity data these two models are different implementations of the same ice loading history and use similar mantle viscosity profiles the model results are compared with each other and with geoid rates determined from grace during august 2002 to november 2009 when averaged over the global ocean the two models have rates that differ by nearly 1 mm yr 1 of ocean mass with the first model giving a correction closer to 2 mm yr 1 and the second closer to 1 mm yr 1 by comparing the two models we have discovered that 50 of the difference is caused by a global land ocean mean in the first model while it is appropriate to include this mean when subtracting gia effects from measurements of sea level change measured by tide gauges or satellite altimetry the mean should not be included when subtracting gia effects from ocean mass variations derived from satellite gravity data when this mean is removed the ocean mass corrections from the two models still disagree by 0 4 mm yr 1 we trace the residual difference to the fact that the first model also has large trends over the ocean related to large rates in its predicted degree 2 order 1 geoid coefficients such oceanic trends are not observed by grace nor are they predicted by the second model and they are shown to be inconsistent with the polar wander rates predicted by the first model itself if these two problems are corrected we find that the two model predictions agree at the 3 level on the basis of this analysis we conclude that the ocean mass correction for grace is closer to 1 mm yr 1 than 2 mm yr 1 although significant uncertainties remain

glacial fluctuations over the last 3500 years reconstructed from a lake sediment record in the northern tibetan plateau abstract reconstructing glacial fluctuations can provide insights into glacial variations in response to climate change and can help predict future glacial changes in the context of global warming here we use an 2 yr resolution record of inert elements derived from a sediment core from tian e lake in the northern tibetan plateau together with proxies for magnetic susceptibility and n alkanes to reconstruct fluctuations of the qiyi glacier over the last 3500 years eight major glacial advances can be identified at 1450 1250 bce 1100 800 bce 250 100 bce and 200 300 ce 600 700 ce 1250 1350 ce 1600 1750 ce and 1850 1950 ce these glacial advances coincided with cold intervals such as the neoglaciation and the little ice age suggesting often mentioned temperature controls on glacial mass variations in the past moreover due to the wet cold climate combinations in the westerlies dominated areas these intervals can also be correlated with wet conditions as revealed by previously reported carbonate contents total organic carbon levels and artemisia amaranthaceae ratios from the same lake these results indicate that humid environments can also contribute to glacial advances in the northern tibetan plateau our study reveals a series of high magnitude multi decadal to multi centennial scale glacial fluctuations during the late holocene and suggests that wet conditions can also facilitate glacial advances in the westerlies dominated regions such as the northern tibetan plateau

contribution of ice sheet and mountain glacier melt to recent sea level rise altimeter data suggest that sea level rose by about 2 4 mm per year from 2005 to 2011 but estimates of the relative contributions of ocean warming and increased ocean mass are equivocal an analysis of ocean temperature and satellite gravity data suggests that the delivery of meltwater from ice sheets and mountain glaciers contributed 75 of the observed sea level rise

elevation change mass balance dynamics and surging of langjokull iceland from 1997 to 2007 in situ mass balance survey is a joint effort of the glaciology group institute of earth sciences university of iceland and the national power company landsvirkjun we thank philippe crochet and tomas johannesson from the icelandic meteorological office for providing the gridded climate data and for useful discussions about the climatology of langjokull the 2007 lidar data were collected by the uk natural environment research council airborne research and survey facility grant ipy 07 08 additional funding was provided by the united states national science foundation grant no dge 1038596 st catharine s st john s and trinity colleges and the university of cambridge b b roberts and scandinavian studies funds we thank cameron rye for initial help coding the mass balance model

accelerated antarctic ice loss from satellite gravity measurements accurate quantification of antarctic ice sheet mass balance and its contribution to global sea level rise remains challenging gravity recovery and climate experiment data spanning the period april 2002 to january 2009 confirm earlier estimates of ice loss for antarctica and indicate that east antarctica started losing mass in about 2006