numerical simulations of marine hydrothermal plumes for europa and other icy worlds abstract the liquid water interiors of europa and other icy moons of the outer solar system are likely to be driven by geothermal heating from the sea floor leading to the development of buoyant hydrothermal plumes these plumes potentially control icy surface geomorphology and are of interest to astrobiologists we have performed a series of simulations of these plumes using the mit gcm ocean circulation model we assume here that europa s ocean is deep of order 100 km and unstratified and that plume buoyancy is controlled by temperature not composition our experiments explore a limited region of parameter space with ocean depth h ranging from 50 to 100 km deep source heat flux q between 0 1 and 10 gw and coriolis parameter f corresponding to europa latitudes between 9 and 47 as predicted by earlier work the plumes in our simulations form narrow cylindrical chimneys a few km across under the influence of the coriolis effect these plumes broaden over time until they become baroclinically unstable breaking up into cone shaped eddies when they become 10 35 km in diameter the shed eddies are of a similar size large scale currents in the region of the plume range between 1 and 5 cm s temperature anomalies in the plume far from the seafloor are tiny varying between 10 and 180 k variations in plume size shape speed and temperature are in excellent agreement with previous laboratory tank experiments and in rough agreement with theoretical predictions plume dynamics and geometry are controlled by a natural rossby number which depends strongly on depth h and coriolis parameter f but only weakly on source heat flux q however some specific theoretical predictions are not borne out by these simulations this may occur because the plumes are reingesting their own emissions a process not considered in our earlier theory

cassini finds molecular hydrogen in the enceladus plume evidence for hydrothermal processes saturn s moon enceladus has a subsurface ocean covered by a layer of ice some liquid escapes into space through cracks in the ice which is the source of one of saturn s rings in october 2015 the cassini spacecraft flew directly through the plume of escaping material and sampled its chemical composition waite et al found that the plume contains molecular hydrogen h2 a sign that the water in enceladus ocean is reacting with rocks through hydrothermal processes see the perspective by seewald this drives the ocean out of chemical equilibrium in a similar way to water around earth s hydrothermal vents potentially providing a source of chemical energy science this issue p 155 1 see also p 132 2 1 lookup doi 10 1126 science aai8703 2 lookup doi 10 1126 science aan0444

researching the earth and a few of its neighbors during my career our knowledge of erupting geysers and volcanoes in the solar system has exploded in this prefatory i tell how i became fascinated with high speed processes through studying meteorite impact dynamics and then how my initial idea of studying old faithful geyser as a volcanic analog led me to work not only on the dynamics of eruption of mount st helens in 1980 but also on geysers erupting on io a fiery satellite of jupiter triton a frigid satellite of neptune and enceladus an active satellite of saturn unforeseeably the study of these events also led to work on mineral thermodynamics and the hydraulics and geomorphic evolution of rapids in the grand canyon this is a narrative not a formal review article but the reader can find references in the related resources section to explore topics in more detail

consistent patterns of antarctic ice sheet interannual variations from envisat radar altimetry and grace satellite gravimetry summary interannual variations of the antarctic ice sheet due to surface mass balance smb fluctuations are important for mass balance estimates and interpretations to date these variations are primarily assessed by global or regional atmospheric modelling satellite altimetry and satellite gravimetry over the ice sheet provide complementary observations of the related volume and mass effects respectively yet so far the interannual signal contents of these observations have not been extensively studied we compare and jointly interpret envisat radar altimetry ra and grace satellite gravimetry results relying on ra products from the along track repeat satellite ra approach and on the grace 10 d solutions by cnes grgs ra results and grace results are expressed in terms of variations of ice sheet thickness z t and ice equivalent thickness zice t respectively in view of the different errors and limitations of both techniques and of differences between z t and zice t expected due to firn related processes our principal approach is a comparison of qualitative patterns in space and time to adjust the spatial resolution of both data sets we describe the spatial filtering inherent to the regularization of the cnes grgs grace solutions and apply this filtering to the envisat ra height changes in a consistent fashion after correction for glacial isostatic adjustment the spatial patterns of linear trends seen by envisat ra and grace over the period 2002 october to 2009 august agree well not only for the extreme ice losses in the west antarctic amundsen sea sector but also for an alternating sequence of gains and losses along the east antarctic coast our main focus is on interannual signals which we represent by the low pass filtered non linear non seasonal components of the z t and zice t time series these components should reflect interannual smb variations apart from effects of changes in ice flow we find an agreement between the interannual variation patterns from envisat ra and grace with temporal correlation coefficients typically in the order of 0 8 this qualitative agreement prevailing even in the theoretical absence of a simple proportionality between z t and zice t indicates that both observational signals primarily originate in common geophysical variations combining both geodetic data sets aids their interpretation and promises to be valuable for the reduction of smb uncertainties in a case study based on the analysis of both grace and envisat ra we identify a prominent interannual feature in west antarctica in 2005 september october as an event of excess snow accumulation with a mass effect of 82 31 gt

grace hydrological estimates for small basins evaluating processing approaches on the high plains aquifer usa the gravity recovery and climate experiment grace satellites provide observations of water storage variation at regional scales however when focusing on a region of interest limited spatial resolution and noise contamination can cause estimation bias and spatial leakage problems that are exacerbated as the region of interest approaches the grace resolution limit of a few hundred km reliable estimates of water storage variations in small basins require compromises between competing needs for noise suppression and spatial resolution the objective of this study was to quantitatively investigate processing methods and their impacts on bias leakage grace noise reduction and estimated total error allowing solution of the trade offs among the methods tested is a recently developed concentration algorithm called spatiospectral localization which optimizes the basin shape description taking into account limited spatial resolution this method is particularly suited to retrieval of basin scale water storage variations and is effective for small basins to increase confidence in derived methods water storage variations were calculated for both csr center for space research and grgs groupe de recherche de geodesie spatiale grace products which employ different processing strategies the processing techniques were tested on the intensively monitored high plains aquifer 450 000 km2 area where application of the appropriate optimal processing method allowed retrieval of water storage variations over a portion of the aquifer as small as 200 000 km2

nature distribution and origin of co2 on enceladus abstract we present the first map of co2 at the surface of enceladus using data obtained by the cassini visible infrared mapping spectrometer vims in order to measure the weak and narrow co2 absorption band depths around 4 26 m we improved 1 the calibration of vims spectra 2 the calculation of geographic coordinates and 3 the projection techniques we averaged multiple observations of a given area to obtain a signal to noise ratio high enough to map the co2 abundances co2 is reliably detected mostly in the south polar region this region includes active faults tiger stripes the highest observed surface temperatures and locations of active plume eruptions the occurrence here of co2 is consistent with an endogenic origin controlled by tectonics both pure co2 ice and complexed co2 are detected from the positions of absorption bands between 4 27 and 4 24 m the highest concentrations of co2 are between the main active faults of the south polar region where the surface temperature is low pure co2 ice deposits at the surface of enceladus are best modeled by the formation of gas pockets below the icy crust and above the surface of the internal ocean these pockets eventually release cold co2 gas 70 to 119 k at low velocity seeping between the tiger stripes matson et al 2018 icarus 302 18 26 co2 clathrate hydrates may form in the ocean and may be subsequently released when a co2 gas pocket blows out and erupts other mechanisms may contribute to reinforcing the anti correlation of the co2 distribution of any type with respect to the location of the tiger stripes such as successive sublimation of co2 and condensation on colder areas and partial frost cover by h2o releases from plume eruptions

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

the ph of enceladus ocean abstract saturn s moon enceladus is a geologically active waterworld the prevailing paradigm is that there is a subsurface ocean that erupts to the surface which leads to the formation of a plume of vapor and ice above the south polar region the chemistry of the ocean is just beginning to be understood but is of profound geochemical and astrobiological interest here we determine the ph of the ocean using a thermodynamic model of carbonate speciation observational data from the cassini spacecraft are used to make a chemical model of ocean water on enceladus the model suggests that enceladus ocean is a na cl co3 solution with an alkaline ph of 11 12 the dominance of aqueous nacl is a feature that enceladus ocean shares with terrestrial seawater but the ubiquity of dissolved na2co3 suggests that soda lakes are more analogous to the enceladus ocean the high ph implies that the hydroxide ion should be relatively abundant while divalent metals should be present at low concentrations owing to buffering by carbonates and phyllosilicates on the ocean floor carboxyl groups in dissolved organic species would be negatively charged while amino groups would exist predominately in the neutral form knowledge of the ph improves our understanding of geochemical processes in enceladus ocean the high ph is interpreted to be a key consequence of serpentinization of chondritic rock as predicted by prior geochemical reaction path models although degassing of co2 from the ocean may also play a role depending on the efficiency of mixing processes in the ocean serpentinization leads to the generation of h2 a geochemical fuel that can support both abiotic and biological synthesis of organic molecules such as those that have been detected in enceladus plume serpentinization and h2 generation should have occurred on enceladus like on the parent bodies of aqueously altered meteorites but it is unknown whether these critical processes are still taking place or if enceladus rocky core has been completely altered by past hydrothermal activity the presence of native h2 in the plume would provide strong evidence for contemporary aqueous alteration that replenishes this source of energy for possible life the high ph also suggests that the delivery of strong oxidants from the surface to the ocean has not been significant otherwise sulfuric acid would be produced which would be consistent with geophysical models of episodic resurfacing activity on enceladus this paper represents an expansion of chemical oceanography to an ocean planet beyond earth

recent snowfall anomalies in dronning maud land east antarctica in a historical and future climate perspective 1 enhanced snowfall on the east antarctic ice sheet is projected to significantly mitigate 21st century global sea level rise in recent years 2009 and 2011 regionally extreme snowfall anomalies in dronning maud land in the atlantic sector of east antarctica have been observed it has been unclear however whether these anomalies can be ascribed to natural decadal variability or whether they could signal the beginning of a long term increase of snowfall here we use output of a regional atmospheric climate model evaluated with available firn core records and gravimetry observations and show that such episodes had not been seen previously in the satellite climate data era 1979 comparisons with historical data that originate from firn cores one with records extending back to the 18th century confirm that accumulation anomalies of this scale have not occurred in the past 60 years although comparable anomalies are found further back in time we examined several regional climate model projections describing various warming scenarios into the 21st century anomalies with magnitudes similar to the recently observed ones were not present in the model output for the current climate but were found increasingly probable toward the end of the 21st century

palaeozoic structural development along the tornquist zone kattegat area denmark abstract the interpretation of newly released commercial 2d reflection seismic data in the kattegat area denmark has provided us with a better understanding of the palaeozoic tectonic processes along the tornquist fault zone a base palaeozoic time structure map a lower palaeozoic twt isopach map a true lower palaeozoic twt isopach map an upper carboniferous lower permian syn rift twt isopach map a top pre zechstein time structure map and a zechstein combined twt isopach and palaeogeography map have been generated the uniform lower palaeozoic sequence thickness in the kattegat both inside and outside the tornquist zone indicates only minor lateral movements if any whereas the extensive upper silurian sequence increasing in thickness to the north indicates a relatively fast regional subsidence the base palaeozoic time structure map and the late palaeozoic syn rift isopach map show a clear late palaeozoic extension in the area the syn rift isopach map in combination with the time equivalent opening of the skagerrak graben at right angles to the tornquist zone in the kattegat indicates that this extensional tectonic event had a dextral slip component measurements on internal extensional faults in the tornquist zone give a minimum right lateral displacement of 10 4 km the footwall blocks were deeply eroded during the early permian rifting and at zechstein times the area became a peneplane the tornquist zone was later exposed to several tectonic phases where dextral slip played a role indicated by the push up and pull down structures caused by restraining and releasing bends of the borglum fault the dextral displacement along the borglum fault since the beginning of the permian is in the order of 5 7 km based on the displacement of a lower palaeozoic local depocentre early permian depocentres and faults which gives a total amount of right lateral displacement since the early palaeozoic in the order of 15 20 km the continuously repeated tectonic episodes along the tornquist zone throughout most of the phanerozoic show that the zone was easily reactivated implying deep seated basement faults the tornquist zone can be seen as a buffer zone between continental blocks whenever changes in the regional stress field are induced

widespread rapid grounding line retreat of pine island thwaites smith and kohler glaciers west antarctica from 1992 to 2011 we measure the grounding line retreat of glaciers draining the amundsen sea sector of west antarctica using earth remote sensing ers 1 2 satellite radar interferometry from 1992 to 2011 pine island glacier retreated 31 km at its center with most retreat in 2005 2009 when the glacier ungrounded from its ice plain thwaites glacier retreated 14 km along its fast flow core and 1 to 9 km along the sides haynes glacier retreated 10 km along its flanks smith kohler glaciers retreated the most 35 km along its ice plain and its ice shelf pinning points are vanishing these rapid retreats proceed along regions of retrograde bed elevation mapped at a high spatial resolution using a mass conservation technique that removes residual ambiguities from prior mappings upstream of the 2011 grounding line positions we find no major bed obstacle that would prevent the glaciers from further retreat and draw down the entire basin 2014 american geophysical union all rights reserved

possible evidence for a methane source in enceladus ocean the internal ocean of enceladus can be expected to present conditions favorable to the trapping of volatiles in clathrates this process could influence the eventual composition of the ocean and therefore of the plumes emitted by the south polar region here we used a statistical thermodynamic model to assess which species detected in the plumes by the cassini ion and neutral mass spectrometer experiment are trapped in clathrates we treated enceladus internal ocean as a terrestrial subglacial lake with a mixture of dissolved volatiles indicated by plume gas measurements we find that the conditions for clathrate formation are met in this ocean except above 20 km or in hypothetical hot spots the formation of multiple guest clathrates depletes methane below plume levels suggesting that clathrates eventually dissociate releasing methane in the fissure that connects the ocean to the surface or that another mechanism such as hydrothermal reactions is compensating by adding methane into the ocean

cassini observes the active south pole of enceladus cassini has identified a geologically active province at the south pole of saturn s moon enceladus in images acquired by the imaging science subsystem iss this region is circumscribed by a chain of folded ridges and troughs at 55 s latitude the terrain southward of this boundary is distinguished by its albedo and color contrasts elevated temperatures extreme geologic youth and narrow tectonic rifts that exhibit coarse grained ice and coincide with the hottest temperatures measured in the region jets of fine icy particles that supply saturn s e ring emanate from this province carried aloft by water vapor probably venting from subsurface reservoirs of liquid water the shape of enceladus suggests a possible intense heating epoch in the past by capture into a 1 4 secondary spin orbit resonance

accelerated west antarctic ice mass loss continues to outpace east antarctic gains a b s t r a c t article history while multiple data sources have confirmed that antarctica is losing ice at an accelerating rate different measurement techniques estimate the details of its geographically highly variable mass balance with different levels of accuracy spatio temporal resolution and coverage some scope remains for methodological improvements using a single data type in this study we report our progress in increasing the accuracy and spatial resolution of time variable gravimetry from the gravity recovery and climate experiment grace we determine the geographic pattern of ice mass change in antarctica between january 2003 and june 2014 accounting for glacio isostatic adjustment gia using the ij05 r2 model expressing the unknown signal in a sparse slepian basis constructed by optimization to prevent leakage out of the regions of interest we use robust signal processing and statistical estimation methods applying those to the latest time series of monthly grace solutions we map antarctica s mass loss in space and time as well as can be recovered from satellite gravity alone ignoring gia model uncertainty over the period 2003 2014 west antarctica has been losing ice mass at a rate of 121 8g t yr and has experienced large acceleration of ice mass losses along the amundsen sea coast of 18 5g t yr 2 doubling the mass loss rate in the past six years the antarctic peninsula shows slightly accelerating ice mass loss with larger accelerated losses in the southern half of the peninsula ice mass gains due to snowfall in dronning maud land have continued to add about half the amount of west antarctica s loss back onto the continent over the last decade we estimate the overall mass losses from antarctica since january 2003 at 92 10 gt yr

deceleration in the earth s oblateness 1 for over three decades satellite laser ranging slr has recorded the global nature of the long wavelength mass change within the earth system analysis of the most recent time series of 30 day slr based estimates of earth s dynamical oblateness characterized by the gravitational degree 2 zonal spherical harmonic j2 indicates that the long term variation of j2 appears to be more quadratic than linear in nature the superposition of a quadratic and an 18 6 year variation leads to the unknown decadal variation reported by cheng and tapley 2004 although the primary trend is expected to be linear due to global isostatic adjustment there is an evident deceleration j 2 18 1 10 13 yr2 in the rate of the decrease in j2 during the last few decades likely due to changes in the rate of the global mass redistribution from melting of the glaciers and ice sheets as well as mass changes in the atmosphere and ocean

enceladus near surface co 2 gas pockets and surface frost deposits abstract solid co2 surface deposits were reported in enceladus south polar region by brown et al 2006 they noted that such volatile deposits are temporary and posited ongoing replenishment we present a model for this replenishment by expanding on the matson et al 2012 model of subsurface heat and chemical transport in enceladus our model explains the distributions of both co2 frost and complexed co2 clathrate hydrate as seen in the cassini visual and infrared mapping spectrometer vims data we trace the journey of co2 from a subsurface ocean the ocean water circulation model of matson et al 2012 brings water up to near the surface where gas exsolves to form bubbles some of the co2 bubbles are trapped and form pockets of gas in recesses at the bottom of the uppermost ice layer when fissures break open these pockets the co2 gas is vented gas pocket venting is episodic compared to the more or less continuous eruptive plumes emanating from the tiger stripes that are supported by plume chambers two styles of gas pocket venting are considered 1 seeps and 2 blowouts the presence of co2 frost patches suggests that the pocket gas slowly seeped through fractured cold ice and when some of the gas reached the surface it was cold enough to condense i e t 70 to 119 k if the fissure opening is large a blowout occurs the rapid escape of gas and drop in pocket pressure causes water in the pocket to boil and create many small aerosol droplets of seawater these may be carried along by the erupting gas electrically charged droplets can couple to the magnetosphere and be dragged away from enceladus most of the co2 blowout gas escapes from enceladus and the remainder is distributed globally however co2 trapped in a clathrate structure does not escape it is much heavier and slower moving than the co2 gas its motion is ballistic and has an average range of about 17 km thus it contributes to deposits in the vicinity of the vent local heat flow indicates that gas pockets can be located as deep as several tens of meters below the surface gas pockets can be reused and we explore their life cycle

mass loss of larsen b tributary glaciers antarctic peninsula unabated since 2002 ice mass loss continues at a high rate among the large glacier tributaries of the larsen b ice shelf following its disintegration in 2002 we evaluate recent mass loss by mapping elevation changes between 2006 and 2010 11 using differencing of digital elevation models dems the measurement accuracy of these elevation changes is confirmed by a null test subtracting dems acquired within a few weeks the overall 2006 2010 11 mass loss rate 9 0 2 1 gt a 1 is similar to the 2001 02 2006 rate 8 8 1 6 gt a 1 derived using dem differencing and laser altimetry this unchanged overall loss masks a varying pattern of thinning and ice loss for individual glacier basins on crane glacier the thinning pulse initially greatest near the calving front is now broadening and migrating upstream the largest losses are now observed for the hektoria green glacier basin having increased by 33 since 2006 our method has enabled us to resolve large residual uncertainties in the larsen b sector and confirm its state of ongoing rapid mass loss

snowfall driven mass change on the east antarctic ice sheet 1 an improved understanding of processes dominating the sensitive balance between mass loss primarily due to glacial discharge and mass gain through precipitation is essential for determining the future behavior of the antarctic ice sheet and its contribution to sea level rise while satellite observations of antarctica indicate that west antarctica experiences dramatic mass loss along the antarctic peninsula and pine island glacier east antarctica has remained comparably stable in this study we describe the causes and magnitude of recent extreme precipitation events along the east antarctic coast that led to significant regional mass accumulations that partially compensate for some of the recent global ice mass losses that contribute to global sea level rise the gain of almost 350 gt from 2009 to 2011 is equivalent to a decrease in global mean sea level at a rate of 0 32 mm yr over this three year period

a comparison of different ways of dealing with isostasy examples from modelling the antarctic ice sheet during the last glacial cycle the bedrock isostatic response exerts a strong control on ice sheet dynamics and is therefore always taken into account in ice sheet models this paperreviews the various methods normally used in the ice sheet modeling community to deal with the bedrock response and compares these with a moresophisticated full earth model each of these bedrock treatments five in total are coupled with a three dimensional thermomechanical ice sheet model underthe same forcing conditions to simulate the antarctic ice sheet during the last glacial cycle the outputs of the simulations are compared on the basis of thetime dependent behavior for the total ice volume and the mean bedrock elevation during the cycle and of the present rate of uplift over antarctica thiscomparison confirms the necessity of accounting for the elastic bending of the lithosphere in order to yield realistic bedrock patterns it furthermoredemonstrates the deficiencies inherent to the diffusion equation in modeling the complex deformation within the mantle nevertheless when characteristicparameters are varied within their range of uncertainty differences within one single method are often of the same order as those between the variousmethods this overview finally tries to point out the main advantages and drawbacks of each of these methods and to determine which one is mostappropriate depending on the specific modeling requirements

mass changes of outlet glaciers along the nordensjkold coast northern antarctic peninsula based on tandem x satellite measurements we analyzed volume change and mass balance of outlet glaciers of the northern antarctic peninsula over the period 2011 to 2013 using topographic data of high vertical accuracy and great spatial detail acquired by bistatic radar interferometry of the tandem x terrasar x satellite formation the study area includes glaciers draining into the larsen a larsen inlet and prince gustav channel embayments after collapse of buttressing ice shelves in 1995 the glaciers became tidewater calving glaciers and accelerated resulting in increased ice export downwasting of most glaciers is going on but at reduced rates compared to previous years in accordance with deceleration of ice flow the rate of mass depletion is 4 2 0 4 gt a 1 with the largest contribution by drygalski glacier amounting to 2 2 0 2 gt a 1 on the technological side the investigations demonstrate the capability of satellite borne single pass radar interferometry as a new tool for accurate and detailed monitoring of glacier volume change