spreading of greenland meltwaters in the ocean revealed by noble gases we present the first noble gas observations in a proglacial fjord in greenland providing an unprecedented view of surface and submarine melt pathways into the ocean using optimum multiparameter analysis noble gas concentrations remove large uncertainties inherent in previous studies of meltwater in greenland fjords we find glacially modified waters with submarine melt concentrations up to 0 66 0 09 and runoff 3 9 0 29 radiogenic enrichment of helium enables identification of ice sheet near bed melt 0 48 0 08 we identify distinct regions of meltwater export reflecting heterogeneous melt processes a surface layer of both runoff and submarine melt and an intermediate layer composed primarily of submarine melt intermediate ocean waters carry the majority of heat to the fjords glaciers and warmer deep waters are isolated from the ice edge the average entrainment ratio implies that ocean water masses are upwelled at a rate 30 times the combined glacial meltwater volume flux

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

glacial meltwater identification in the amundsen sea abstractpine island ice shelf in the amundsen sea is losing mass because of warm ocean waters melting the ice from below tracing meltwater pathways from ice shelves is important for identifying the regions most affected by the increased input of this water type here optimum multiparameter analysis is used to deduce glacial meltwater fractions from water mass characteristics temperature salinity and dissolved oxygen concentrations collected during a ship based campaign in the eastern amundsen sea in february march 2014 using a one dimensional ocean model processes such as variability in the characteristics of the source water masses on shelf and biological productivity respiration are shown to affect the calculated apparent meltwater fractions these processes can result in a false meltwater signature creating misleading apparent glacial meltwater pathways an alternative glacial meltwater calculation is suggested using a pseudo circumpolar deep water endpoint and using an artificial increase

estimating ocean heat transports and submarine melt rates in sermilik fjord greenland using lowered acoustic doppler current profiler ladcp velocity profiles submarine melting at the ice ocean interface is a significant term in the mass balance of marine terminating outlet glaciers however obtaining direct measurements of the submarine melt rate or the ocean heat transport towards the glacier that drives this melting has been difficult due to the scarcity of observations as well as the complexity of oceanic flows here we present a method that uses synoptic velocity and temperature profiles but accounts for the dominant mode of velocity variability to obtain representative heat transport estimates we apply this method to the sermilik fjord helheim glacier system in southeastern greenland using lowered acoustic doppler current profiler ladcp and hydrographic data collected in summer 2009 we find a mean heat transport towards the glacier of 29 10 9 w implying a submarine melt rate at the glacier face of 650 m a 1 t he resulting adjusted velocity profile is indicative of a multilayer residual circulation where the meltwater mixture flows out of the fjord at the surface and at the stratification maximum

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

rapid submarine melting of the calving faces of west greenland glaciers widespread glacier acceleration has been observed in greenland in the past few years oceanographic observations taken in summer 2008 show that ocean waters melted a substantial fraction of ice along the calving fronts of three west greenland glaciers indicating that submarine melting has a profound influence on grounding line stability widespread glacier acceleration has been observed in greenland in the past few years1 2 3 4 associated with the thinning of the lower reaches of the glaciers as they terminate in the ocean5 6 7 these glaciers thin both at the surface from warm air temperatures and along their submerged faces in contact with warm ocean waters8 little is known about the rates of submarine melting9 10 11 and how they may affect glacier dynamics here we present measurements of ocean currents temperature and salinity near the calving fronts of the eqip sermia kangilerngata sermia sermeq kujatdleq and sermeq avangnardleq glaciers in central west greenland as well as ice front bathymetry and geographical positions we calculate water mass and heat budgets that reveal summer submarine melt rates ranging from 0 7 0 2 to 3 9 0 8 m d 1 these rates of submarine melting are two orders of magnitude larger than surface melt rates but comparable to rates of iceberg discharge we conclude that ocean waters melt a considerable but highly variable fraction of the calving fronts of glaciers before they disintegrate into icebergs and suggest that submarine melting must have a profound influence on grounding line stability and ice flow dynamics

upper ocean distribution of glacial meltwater in the amundsen sea antarctica pine island ice shelf in the amundsen sea is losing mass due to increased heat transport by warm ocean water penetrating beneath the ice shelf and causing basal melt tracing this warm deep water and the resulting glacial meltwater can identify changes in melt rate and the regions most affected by the increased input of this freshwater here optimum multi parameter analysis is used to deduce glacial meltwater fractions from independent water mass characteristics standard hydrographic observations noble gases and oxygen isotopes collected during a ship based campaign in the eastern amundsen sea in february march 2014 noble gases neon argon krypton and xenon and oxygen isotopes are used to trace the glacial melt and meteoric water found in seawater and we demonstrate how their signatures can be used to rectify the hydrographic trace of glacial meltwater which provides a much higher resolution picture the presence of glacial meltwater is shown to mask the winter water properties resulting in differences between the water mass analyses of up to 4 g kg 1 glacial meltwater content this discrepancy can be accounted for by redefining the pure winter water endpoint in the hydrographic glacial meltwater calculation the corrected glacial meltwater content values show a persistent signature between 150 400 m of the water column across all of the sample locations up to 535 km from pine island ice shelf with increased concentration towards the west along the coastline it also shows for the first time the signature of glacial meltwater flowing off shelf in the eastern channel

characteristics of ocean waters reaching greenland s glaciers interaction of greenland s marine terminating glaciers with the ocean has emerged as a key term in the ice sheet mass balance and a plausible trigger for their recent acceleration our knowledge of the dynamics however is limited by scarcity of ocean measurements at the glacier ocean boundary here data collected near six marine terminating glaciers 79 north kangerdlugssuaq helheim and petermann glaciers jakobshavn isbrae and the combined sermeq kujatdleq and akangnardleq are compared to investigate the water masses and the circulation at the ice ocean boundary polar water of arctic origin and atlantic water from the subtropical north atlantic are found near all the glaciers property analysis indicates melting by atlantic water aw found at the grounding line depth near all the glaciers and the influence of subglacial discharge at depth in summer aw temperatures near the glaciers range from 4 58c in the southeast to 0 168c in northwest greenland consistent with the distance from the subtropical north atlantic and cooling across the continental shelf a review of its offshore variability suggests that aw temperature changes in the fjords will be largest in southern and smallest in northwest greenland consistent with the regional distribution of the recent glacier acceleration

dissolved gas dynamics in perennially ice covered lake fryxell antarctica we use the concentrations of noble gases he ne and ar helium isotopes and tritium to characterize the mechanisms and rates of ventilation for lake fryxell antarctica as well as the physical processes controlling dissolved gases the upper oxic zone is ventilated on timescales of several decades the anoxic bottom waters are weakly ventilated with a turnover time of 3 800 years in the upper euphotic zone helium and neon are greatly undersaturated with respect to solubility equilibrium with the atmosphere whereas argon is greatly supersaturated owing to equilibrium partitioning of the gases between ice water and air inclusions in the ice in the bottom waters the inert dissolved gas concentrations may be remnants of a near desiccation event that occurred 2 000 years b p consistent with current paleoclimatic theories

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

biological and physical controls on o 2 ar ar and p co 2 variability at the western antarctic peninsula and in the drake passage abstract using simultaneous sub kilometer resolution underway measurements of surface o2 ar total o2 and pco2 from annual austral summer surveys in 2012 2013 and 2014 we explore the impacts of biological and physical processes on the o2 and pco2 system spatial and interannual variability at the western antarctic peninsula wap in the wap mean o2 ar supersaturation was 7 6 9 1 and mean pco2 supersaturation was 28 22 we see substantial spatial variability in o2 and pco2 including sub mesoscale mesoscale variability with decorrelation length scales of 4 5 km consistent with the regional rossby radius this variability is embedded within onshore offshore gradients o2 in the lter grid region is driven primarily by biological processes as seen by the median ratio of the magnitude of biological oxygen o2 ar to physical oxygen ar supersaturation anomalies relative to atmospheric equilibrium 2 6 however physical processes have a more pronounced influence in the southern onshore region of the grid where we see active sea ice melting total o2 measurements should be interpreted with caution in regions of significant sea ice formation and melt and glacial meltwater input pco2 undersaturation predominantly reflects biological processes in the lter grid in contrast we compare these results to the drake passage where gas supersaturations vary by smaller magnitudes and decorrelate at length scales of 12 km in line with latitudinal changes in the regional rossby radius here biological processes induce smaller o2 ar supersaturations mean 0 14 1 3 and pco2 undersaturations mean 2 8 3 9 than in the wap and pressure changes bubble and gas exchange fluxes drive stable ar supersaturations

optimum multiparameter analysis of mixing in the thermocline of the eastern indian ocean a method of water mass analysis is developed which optimizes the use of all information contained in a hydrographic data set by solving an overdetermined linear set of mixing equations it requires representation of water masses by a finite number of water types and observations from at least as many oceanographic parameters as water types the procedure to establish the water types find the correct weights for the parameters and solve the mixing equations through minimization of the residuals is described in detail the method is applied to a data set from the eastern indian ocean where indian central water and australasian mediterranean water meet to produce a strong front in the thermocline it is shown that although most of the water from the indonesian archipelago is carried westward north of 11 s contributions from the australasian mediterranean water are found as far south as 25 s particularly along the australian shelf as a result of advection with the leeuwin current

structure and dynamics of a subglacial discharge plume in a greenlandic fjord discharge of surface derived meltwater at the submerged base of greenland s marine terminating glaciers creates subglacial discharge plumes that rise along the glacier ocean interface these plumes impact submarine melting calving and fjord circulation observations of plume properties and dynamics are challenging due to their proximity to the calving edge of glaciers therefore to date information on these plumes has been largely derived from models here we present temperature salinity and velocity data collected in a plume that surfaced at the edge of saqqarliup sermia a mid sized greenlandic glacier the plume is associated with a narrow core of rising waters approximately 20 m in diameter at the ice edge that spreads to a 200 m by 300 m plume pool as it reaches the surface before descending to its equilibrium depth volume flux estimates indicate that the plume is primarily driven by subglacial discharge and that this has been diluted in a ratio of 1 10 by the time the plume reaches the surface while highly uncertain meltwater fluxes are likely two orders of magnitude smaller than the subglacial discharge flux the overall plume characteristics agree with those predicted by theoretical plume models for a convection driven plume with limited influence from submarine melting this article is protected by copyright all rights reserved

an optimized estimate of glacial melt from the ross ice shelf using noble gases stable isotopes and cfc transient tracers 1 isotopes of helium and neon and the h218o h216o ratio of water are proven proxies for melt from glacial ice beneath floating ice shelves and at ice shelf fronts their high concentrations in glacial meltwater compared to other environmental sources make them ideal tracers for studies of the pathways of glacial meltwater from its origins into the ocean interior we combine noble gas and stable isotopes with temperature salinity and dissolved oxygen measurements from three cruises along the ross ice shelf during the austral summers of 1993 1994 and 1999 2000 and to the ross sea in 2000 2001 and use optimal multiparameter analysis to compute the water mass concentration including glacial meltwater the distribution of meltwater at the front of the ross ice shelf extended east from 180 w with the highest concentrations found near 165 w in both 1994 and 2000 the mean meltwater concentration at the ice shelf front was 2 0 0 33 in 1994 2 2 0 36 in 2000 and 0 25 0 1 in the western ross sea in 2001 water mass concentrations are used to correct for bias in the cfc age introduced by mixing with cfc free waters an effect revealed by comparing cfc age with transit time distribution curves the water residence time within the ice shelf cavity using cfcs and the mean meltwater concentration implies a basal melt rate of 33 50 km3 a 1

role of greenland freshwater anomaly in the recent freshening of the subpolar north atlantic the cumulative greenland freshwater flux anomaly has exceeded 5 000 km3 since the 1990s the volume of this surplus freshwater is expected to cause substantial freshening in the north atlantic analysis of hydrographic observations in the subpolar seas reveals freshening signals in the 2010s the sources of this freshening are yet to be determined in this study the relationship between the surplus greenland freshwater flux and this freshening is tested by analyzing the propagation of the greenland freshwater anomaly and its impact on salinity in the subpolar north atlantic based on observational data and numerical experiments with and without the greenland runoff a passive tracer is continuously released during the simulations at freshwater sources along the coast of greenland to track the greenland freshwater anomaly tracer budget analysis shows that 44 of the volume of the greenland freshwater anomaly is retained in the subpolar north atlantic by the end of the simulation this volume is sufficient to cause strong freshening in the subpolar seas if it stays in the upper 50 100 m however in the model the anomaly is mixed down to several hundred meters of the water column resulting in smaller magnitudes of freshening compared to the observations therefore the simulations suggest that the accelerated greenland melting would not be sufficient to cause the observed freshening in the subpolar seas and other sources of freshwater have contributed to the freshening impacts on salinity in the subpolar seas of the freshwater transport through fram strait and precipitation are discussed

the impact of glacier geometry on meltwater plume structure and submarine melt in greenland fjords meltwater from the greenland ice sheet often drains subglacially into fjords driving upwelling plumes at glacier termini ocean models and observations of submarine termini suggest that plumes enhance melt and undercutting leading to calving and potential glacier destabilization here we systematically evaluate how simulated plume structure and submarine melt during summer months depends on realistic ranges of subglacial discharge glacier depth and ocean stratification from 12 greenland fjords our results show that grounding line depth is a strong control on plume induced submarine melt deep glaciers produce warm salty subsurface plumes that undercut termini and shallow glaciers produce cold fresh surface trapped plumes that can overcut termini due to sustained upwelling velocities plumes in cold shallow fjords can induce equivalent depth averaged melt rates compared to warm deep fjords these results detail a direct ocean ice feedback that can affect the greenland ice sheet

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

north atlantic warming and the retreat of greenland s outlet glaciers mass loss from the greenland ice sheet quadrupled over the past two decades contributing a quarter of the observed global sea level rise increased submarine melting is thought to have triggered the retreat of greenland s outlet glaciers which is partly responsible for the ice loss however the chain of events and physical processes remain elusive recent evidence suggests that an anomalous inflow of subtropical waters driven by atmospheric changes multidecadal natural ocean variability and a long term increase in the north atlantic s upper ocean heat content since the 1950s all contributed to a warming of the subpolar north atlantic this led in conjunction with increased runoff to enhanced submarine glacier melting future climate projections raise the potential for continued increases in warming and ice mass loss with implications for sea level and climate

excess helium and neon in the southeast pacific tracers for glacial meltwater 1 we analyze helium he and neon ne isotope data sets from the southeast pacific sector of the southern ocean collected in 1992 and 1994 and describe a new method to estimate glacial meltwater fluxes independent of previous approaches the waters sampled during these cruises reveal large atmospheric he and ne excess concentrations in the upper 500 m that are derived predominantly from the dissolution of air contained in glacial ice during melting underneath and at the front of floating ice shelves at elevated hydrostatic pressure on the stations sampled the meltwater fractions are largest near the northern and southern ice shelf fronts of george vi ice shelf 1 5 2 5 consistent with prior inferences from 18o the inventories of 4he and ne with local glacial meltwater origin south of 70 s between 210 e and 295 e are 2 5 0 7 1011 cm3stp 4he and 7 9 2 7 1011 cm3stp ne respectively the associated meltwater volumes are 430 120 gt for 4he and 400 140 gt for ne for an estimated seawater residence time of 2 years on the continental shelf the amounts of glacial meltwater translate into bulk melting rates of 215 170 gt yr 1 for 4he and 200 170 gt yr 1 for ne the values derived from 4he are expected to be larger than those obtained from ne because of the terrigenic he component which accounts for 10 15 of the he excess in this region our regional melting rate of 200 215 gt yr 1 is comparable to a prior estimate but subject to uncertainties resulting from the station distribution the air sea gas exchange and the estimate of the net transport through the study region

localized plumes drive front wide ocean melting of a greenlandic tidewater glacier support was provided by the national science foundation nsf through plr 1418256 and plr 1744835 and through woods hole oceanographic institution whoi ocean and climate change institute occi and the clark foundation this work was also supported by a uk natural environmental research council nerc phd studentship ne l501566 1 and scottish alliance for geoscience environment society sages early career research exchange funding to d a s

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

recent large increases in freshwater fluxes from greenland into the north atlantic 1 freshwater fw fluxes from river runoff and precipitation minus evaporation for the pan arctic seas are relatively well documented and prescribed in ocean gcms fluxes from greenland on the other hand are generally ignored altogether despite their potential impacts on ocean circulation and marine biology here we present a reconstruction of the spatially distributed fw flux from greenland for 1958 2010 we find a modest increase into the arctic ocean during this period fluxes into the irminger basin however have increased by fifty percent 6 3 0 5 km3 yr 2 in less than twenty years this greatly exceeds previous estimates for the ice sheet as a whole the rate of increase since 1992 is 16 9 1 8 km3 yr 2 the cumulative fw anomaly since 1995 is 3200 358 km3 which is about a third of the magnitude of the great salinity anomaly gsa of the 1970s if this trend continues into the future the anomaly will exceed that of the gsa by about 2025

glacier and ocean variability in ata sund west greenland since 1400 ce to improve knowledge of marine terminating glaciers in western greenland marine sediment cores from the ata sund fjord system hosting two outlet glaciers eqip sermia and kangilerngata sermia were investigated the main objective was to reconstruct glacial activity and paleoceanographic conditions during the past 600 years ice rafted debris ird was quantified by wet sieving sediment samples and by using a computed tomography scan variability in relative bottom water temperatures in the fjord was reconstructed using foraminiferal analysis on the basis of this three periods of distinct glacial regimes were identified period 1 1380 1810 ce which covers the culmination of the little ice age lia and is interpreted as having advanced glaciers with high ird content period 2 1810 1920 ce the end of the lia which was characterised by a lowering of the glaciers calving flux in response to climate cooling during period 3 1920 2014 ce both glaciers retreated substantially to their present day extent the bottom water temperature started to decrease just before period 2 and remained relatively low until just before the end of period 3 this is interpreted as a local response to increased glacial meltwater input our study was compared with a study in disko bay nearby jakobshavn glacier and the result shows that both of these greenlandic marine terminating glaciers are responding to large scale climate change however the specific imprint on the glaciers and the different fjord waters in front of them result in contrasting glacial responses and sediment archives in their respective fjords

effects of increase glacier discharge on phytoplankton bloom dynamics and pelagic geochemistry in a high arctic fjord arctic fjords experience extremely pronounced seasonal variability and spatial heterogeneity associated with changes in ice cover glacial retreat and the intrusion of continental shelf s adjacent water masses global warming intensifies natural environmental variability on these important systems yet the regional and global effects of these processes are still poorly understood in the present study we examine seasonal and spatial variability in kongsfjorden on the western coast of spitsbergen svalbard we report hydrological biological and biogeochemical data collected during spring summer and fall 2012 our results show a strong phytoplankton bloom with the highest chlorophyll a chla levels ever reported in this area peaking 15 5 g l during late may and completely dominated by large diatoms at the inner fjord that may sustain both pelagic and benthic production under weakly stratified conditions at the glacier front a progressively stronger stratification of the water column during summer and fall was shaped by the intrusion of warm atlantic water t 3 c and sal 34 65 into the fjord at around 100 m depth and by turbid freshwater plumes t 1 c and sal 34 65 at the surface due to glacier meltwater input biopolymeric carbon fractions and isotopic signatures of the particulate organic material pom revealed very fresh and labile material produced during the spring bloom 13c enriched with values up to 22 7 at the highest chl a peak and high in carbohydrates and proteins content up to 167 and 148 g l respectively and a clear and strong continental signature of the pom present during late summer and fall 13c depleted with values averaging 26 5 and high in lipid content up to 92 g l when freshwater melting is accentuated our data evidence the importance of combining both physical i e water mass dominance and geochemical i e characteristics of material released by glacier runoff data in order to understand the timing intensity and characteristics of the phytoplankton bloom in kongsfjorden a continuously changing system due to sustained warming in a scenario where glacial retreat is predicted to increase the impacts of meltwater discharge and associated delivery of organic and inorganic material to the surrounding waters special attention is required in order to predict the consequences for arctic fjords and adjacent shelf ecosystems

oceanic heat delivery via kangerdlugssuaq fjord to the south east greenland ice sheet acceleration of the greenland ice sheet gris tidewater outlet glaciers has increased the ice sheet s contribution to global sea level rise over the last two decades coincident increases in atmospheric temperatures around greenland explain some of the increased ice loss but warm atlantic origin water aw is increasingly recognized as contributing to the accelerating ice mass loss particularly via the outlet glaciers of south east se greenland however there remains a lack of understanding of the variability in heat content of the water masses found to the east of greenland and how this heat is communicated to the outlet glaciers of the gris here a new analysis is presented of ocean gris interaction in which the oceanic heat flux toward the ice sheet in kangerdlugssuaq fjord 0 26 tw is an order of magnitude greater than that reported for the other major outlet glacier of se greenland helheim heat delivered by aw to the calving front of kangerdlugssuaq is equivalent to 10 m d 1 melt i e 30 60 of the ice flow speed and thus is highly significant during the observational campaign in september 2010 warm polar surface water psww melted a substantial volume of ice within the fjord equivalent to 25 of the volume melted by aw alone satellite derived sea surface temperatures show large interannual variability in psww over the 20 year period 1991 2011 anomalously warm psww was observed within the fjord prior to the well documented major ice front retreats of may 2004 and november 2010

helium a new tracer in antarctic oceanography the abyssal characteristics of the world oceans are strongly influenced by the northward propagation of antarctic bottom water aabw an important source of aabw is weddell sea bottom water wsbw which is formed in part on the continental slope of the southern weddell sea1 3 the formation of wsbw on the continental slope is related to the floating ice shelves of the southern weddell sea filchner ronne ice shelves western shelf water wsw is modified under the ice shelves by cooling and admixture of melt water to form ice shelf water isw and a substantial part of the isw flows over the sill that separates the filchner depression from the weddell sea and participates in the formation of wsbw4 5 the data reported here demonstrate that the water ice interaction leads to a strong 4he supersaturation of the isw due to dissolution of air entrapped in the ice shelf melt water the 4he supersaturation of the isw can be used as a tracer of this water mass and also influences the 4he balance of the wsbw

impact of fjord dynamics and glacial runoff on the circulation near helheim glacier greenland to show that the melting circulation is affected by seasonal runoff from the glacier and by the fjord s externally forced currents and stratification the presence of light arctic and dense atlantic waters in the fjord in particular causes meltwater to be exported at depth and influences the vertical distribution of heat along the ice margin our results indicate that the melting circulation is more complex than hypothesized and influenced by multiple external parameters we conclude that the shape and stability of greenland s glaciers may be strongly influenced by the layering of the arctic and atlantic waters in the fjord as well as their variability

oceanic boundary conditions for jakobshavn glacier part ii provenance and sources of variability of disko bay and ilulissat icefjord waters 1990 2011 abstractjakobshavn glacier west greenland has responded to temperature changes in ilulissat icefjord into which it terminates basin waters in this fjord exchange with neighboring disko bay waters of a particular density at least once per year this study determined the provenance of this isopycnic layer for 1990 2011 using hydrographic data from cape farewell to baffin bay the warm atlantic origin core of the west greenland current never filled deep disko bay or entered the fjord basin because of bathymetric impediments on the west greenland shelf instead equal parts of atlantic water and less saline polar water filled the fjord basin and bathed jakobshavn glacier the polar water fraction was often traceable to the east west greenland current but sometimes to the colder baffin current the huge annual temperature cycle on west greenland current isopycnals did not propagate into deep disko bay or the fjord basin because isopycnals over the west greenland shelf were depressed during the warm autumn

subannual and seasonal variability of atlantic origin waters in two adjacent west greenland fjords greenland fjords provide a pathway for the inflow of warm shelf waters to glacier termini and outflow of glacially modified waters to the coastal ocean characterizing the dominant modes of variability in fjord circulation and how they vary over subannual and seasonal time scales is critical for predicting ocean heat transport to the ice here we present a 2 year hydrographic record from a suite of moorings in davis strait and two neighboring west greenland fjords that exhibit contrasting fjord and glacier geometry kangerdlugssuaq sermerssua and rink isbrae hydrographic variability above the sill exhibits clear seasonality with a progressive cooling of near surface waters and shoaling of deep isotherms above the sill during winter to spring renewal of below sill waters coincides with the arrival of dense waters at the fjord mouth warm salty atlantic origin water cascades into fjord basins from winter to midsummer we then use seaglider observations at davis strait along with reanalysis of sea ice and wind stress in baffin bay to explore the role of the west greenland current and local air sea forcing in driving fjord renewal these results demonstrate the importance of both remote and local processes in driving renewal of near terminus waters highlighting the need for sustained observations and improved ocean models that resolve the complete slope trough fjord ice system

the distributions of helium isotopes and tritium along the u s geotraces north atlantic sections geotraces gao3 abstract we present the distributions of helium isotopes in the form of helium isotope ratio anomaly relative to the atmospheric ratio and tritium along two sections occupied in the subtropical north atlantic as part of the first u s geotraces survey geotraces ga03 the general distributions of these isotopes are consistent with the continuing penetration and evolution of bomb produced tritium and its daughter isotope 3 he in the main thermocline and along the western boundary current system we combine these two distributions to compute a tritium 3 he age which is related to the elapsed time since the water was at the ocean surface although it is an indicator biased by the effects of mixing and influenced by the time history and spatial distribution of bomb tritium delivery to the ocean surface it still remains a useful measure of ventilation time scales aside from the continued propagation of the tritium 3 he transient into the ocean interior there are three notable features of interest in these distributions the first is the clear signature of upwelling in the water column near the coast of mauritania characterized by the upward bowing of isochrones in the thermocline and discernable 3 he excess at the ocean surface a simple 3 he mass balance calculation suggests an upwelling flux of order 1 8 10 6 m 3 s 1 1 8 sv along the mauritanian coast the second is a mid depth 1500 2000 m core of ventilated waters centered over the mid atlantic ridge an anticyclonic circulation of waters likely originating in the labrador sea the third notable feature is a volcanic 3 he plume at about 3500 m depth emanating from the tag hydrothermal area that is detectable as much as 500 km away on each side of the mid atlantic ridge we estimate a 3 he heat ratio of 7 10 18 mol j 1 and a 3 he flux from the tag site of 15 mmol y 1 since 3 he is a conserved tracer in the absence of measureable tritium the correlation of volcanic 3 he with other hydrothermally influenced teis e g fe can be used as a dilution tracer as probe of non conservative behavior in the water column also since the regional and global fluxes of volcanic 3 he are known the correlations can be used as a regional global flux gauge for hydrothermal input of those teis

characterization of opening mode fracture systems in the austin chalk abstract the upper cretaceous austin chalk is a low permeability fractured reservoir that has been the target of numerous horizontal wells in texas for wells to be successful parameters such as well bore azimuth target horizon and length must be optimized furthermore information on fracture height and the storage volume potentially connected to the well bore is required two case studies are presented in which the height aspect ratio and vertical persistence of opening mode fractures in the austin chalk have been examined together with previously known attributes of fracture population attributes of orientation aperture effective aperture spacing aspect ratio fracture fill and fracture permeability the studies are of an outcrop of the upper austin chalk near waxahachie north central texas grove creek and of a vertical segment and two horizontal laterals of a core in the atco member in frio county pearsall field kinlaw core large potentially open fractures are commonly clustered the distance between clusters ranging from 1 to 50 m aperture size distributions follow power laws and spacing size distributions are negative logarithmic or lognormal the aperture size at which fractures are open to fluids is variable 0 14 to 11 mm fracture permeability which is scale dependent has been determined at 7 1 d for 18 m of lower austin chalk core and 286 d for 300 m of upper austin chalk outcrop fractures may terminate at chalk marl contacts tip out within the marl or pass through the marl layers fracture height is governed by truncation effects at marl horizons and pressure solution seams which in turn partly depend on fracture aperture and thickness of the inhibiting layer

natural fractures in shale a review and new observations natural fractures have long been suspected as a factor in production from shale reservoirs because gas and oil production commonly exceeds the rates expected from low porosity and low permeability shale host rock many shale outcrops cores and image logs contain fractures or fracture traces and microseismic event patterns associated with hydraulic fracture stimulation have been ascribed to natural fracture reactivation here we review previous work and present new core and outcrop data from 18 shale plays that reveal common types of shale fractures and their mineralization orientation and size patterns a wide range of shales have a common suite of types and configurations of fractures those at high angle to bedding faults bed parallel fractures early compacted fractures and fractures associated with concretions these fractures differ markedly in their prevalence and arrangement within each shale play however constituting different fracture stratigraphies differences that depend on interface and mechanical properties governed by depositional diagenetic and structural setting several mechanisms may act independently or in combination to cause fracture growth including differential compaction local and regional stress changes associated with tectonic events strain accommodation around large structures catagenesis and uplift fracture systems in shales are heterogeneous they can enhance or detract from producibility augment or reduce rock strength and the propensity to interact with hydraulic fracture stimulation burial history and fracture diagenesis influence fracture attributes and may provide more information for fracture prediction than is commonly appreciated the role of microfractures in production from shale is currently poorly understood yet potentially critical we identify a need for further work in this field and on the role of natural fractures generally

surface expression of a wall fountain application to subglacial discharge plumes abstractwe use laboratory experiments and theoretical modeling to investigate the surface expression of a subglacial discharge plume as occurs at many fjords around greenland the experiments cons

characteristics of meltwater export from jakobshavn isbrae and ilulissat icefjord jakobshavn isbrae which terminates in ilulissat icefjord has undergone rapid retreat and is currently the largest contributor to ice sheet mass loss among greenland s marine terminating glaciers accelerating mass loss is increasing fresh water discharge to the ocean which can feed back on ice melt impact marine ecosystems and potentially modify regional and larger scale ocean circulation here we present hydrographic observations including inert geochemical tracers that allow the first quantitative description of the glacially modified waters exported from the jakobshavn icefjord system observations within the fjord suggest a deep reaching overturning cell driven by glacial buoyancy forcing modified waters containing submarine meltwater up to 2 5 0 12 subglacial discharge up to 6 0 37 and large portions of entrained ocean waters are seen to exit the fjord and flow north the exported meltwaters form a buoyant coastal gravity current reaching to 100 m depth and extending 10 km offshore

effects of sedimentary interfaces on fracture pattern linkage and cluster formation in peritidal carbonate rocks abstract the permeability of a reservoir is particularly dependent upon the proportion of its fractures that penetrate or are arrested at interfaces such as contacts and discontinuities here we report on fracture penetration and fracture arrest in lower cretaceous peritidal deposits exposed in the pizzicoli quarry gargano promontory southern italy we measured more than 2000 fractures in the field and using lidar data of which 564 fractures from the field and 518 from lidar studies are the focus of this paper fracture arrest deflection and penetration depend much on the effects of peritidal cycle interfaces such as paleosol horizons laminated carbonate mudstones and stylonodular horizons the laminated mudstones have the greatest effect 63 99 of the fractures are deflected or arrested at such interfaces whereas 63 90 are deflected arrested at paleosols and 20 35 at stylonodular horizons in the mudstones many fractures are arrested at thin internal laminae such that few penetrate the entire laminated layer and fewer still the boundaries between the layers paleosol interfaces deflect arrest more than 60 of all fractures however when small offset fractures above and below paleosols are regarded as penetrating they are evenly spaced non clustered so that fracture related fluid transport may occur across the entire paleosol stylonodular horizons deflect arrest and split some fractures but generally have little effect compared with the other types of interfaces we present three main mechanisms for fracture deflection and or arrest 1 the fracture induced tensile stress ahead of its tip referred to as the cook gordon debonding mechanism 2 rotation of the principal stresses at and across the interface resulting in the formation of stress barriers and 3 large elastic mismatch particularly as regards young s moduli between layers across an interface all these mechanisms are likely to have operated during fracture propagation and arrest in the carbonate rocks of the pizzicoli quarry

effect of near terminus subglacial hydrology on tidewater glacier submarine melt rates submarine melting of greenlandic tidewater glacier termini is proposed as a possible mechanism driving their recent thinning and retreat we use a general circulation model mitgcm to simulate water circulation driven by subglacial discharge at the terminus of an idealized tidewater glacier we vary the spatial distribution of subglacial discharge emerging at the grounding line of the glacier and examine the effect on submarine melt volume and distribution we find that subglacial hydrology exerts an important control on submarine melting under certain conditions a distributed system can induce a factor 5 more melt than a channelized system with plumes from a single channel inducing melt over only a localized area subglacial hydrology also controls the spatial distribution of melt which has the potential to control terminus morphology and calving style our results highlight the need to constrain near terminus subglacial hydrology at tidewater glaciers if we are to represent ocean forcing accurately

acceleration of jakobshavn isbrae triggered by warm subsurface ocean waters observations over past decades show a sudden switch of jakobshavn isbrae a large outlet glacier feeding a deep ocean fjord on greenland s west coast from slow thickening to rapid thinning in 1997 this switch is associated with a doubling in glacier velocity hydrographic data show a concurrent sudden increase in subsurface ocean temperatures along the entire west coast of greenland suggesting that the changes in jakobshavn isbrae were triggered by the arrival of relatively warm water originating from the irminger sea observations over the past decades show a rapid acceleration of several outlet glaciers in greenland and antarctica1 one of the largest changes is a sudden switch of jakobshavn isbrae a large outlet glacier feeding a deep ocean fjord on greenland s west coast from slow thickening to rapid thinning2 in 1997 associated with a doubling in glacier velocity3 suggested explanations for the speed up of jakobshavn isbrae include increased lubrication of the ice bedrock interface as more meltwater has drained to the glacier bed during recent warmer summers4 and weakening and break up of the floating ice tongue that buttressed the glacier5 here we present hydrographic data that show a sudden increase in subsurface ocean temperature in 1997 along the entire west coast of greenland suggesting that the changes in jakobshavn isbrae were instead triggered by the arrival of relatively warm water originating from the irminger sea near iceland we trace these oceanic changes back to changes in the atmospheric circulation in the north atlantic region we conclude that the prediction of future rapid dynamic responses of other outlet glaciers to climate change will require an improved understanding of the effect of changes in regional ocean and atmosphere circulation on the delivery of warm subsurface waters to the periphery of the ice sheets

modelling intra annual dynamics of a major marine terminating arctic glacier significant intra annual variability in flow rates of tidewater terminating arctic glaciers has been observed in recent years these changes may result from oceanic and or atmospheric forcing through 1 perturbations at the terminus such as enhanced submarine melt and changes in sea ice buttressing or 2 increased surface melt in response to atmospheric warming reaching the bed and promoting glacier slip we examine the influence of these processes on belcher glacier a large fast flowing tidewater outlet of the devon island ice cap in the canadian arctic a hydrologically coupled higher order ice flow model is used to estimate changes in glacier flow speed as a result of changes in sea ice buttressing and hydrologically driven melt season dynamics daily run off from five sub catchments over the 2008 and 2009 melt seasons provides meltwater forcing for the model simulations model results are compared with remotely sensed and in situ ice surface velocity measurements sea ice effects are found to have a minor influence on glacier flow speed relative to that of meltwater drainage which is clearly implicated in short term velocity variations during the melt season we find that threshold drainage is essential in determining the timing of these short lived accelerations

industrial mineral occurrences associated with cenozoic volcanic rocks of sardinia italy geological mineralogical geochemical features and genetic implications the most important industrial mineral im deposits associated with the cenozoic volcanics of sardinia include kaolin bentonite and zeolites though of less significance perlite and potassium feldspar are also important in local and national markets bentonite and to a lesser extent kaolin and perlite form economically viable deposits and zeolites appear as very important industrial mineral commodities for future economic development the market situation for potassium feldspar is still under evaluation for use in ceramics all these deposit types occur as alteration products of cenozoic volcanic rocks which were emplaced during three main volcanic cycles in the eocene ec 55 to 51 ma oligocene miocene omc 32 to 13 ma and pliocene pleistocene ppc 5 to 0 1 ma kaolin bentonite zeolites and potassium feldspar occur as alteration products of the omc volcanites perlite occurs as an alteration product of the ppc volcanites all deposits have generally derived from the alteration of the most acidic members of the cenozoic volcanic rocks rhyolites to rhyodacites but differences among the associated ore forming phenomena are recognized hydrothermal sensu stricto deuteric alteration and weathering are the most important processes involved in ore formation weathering although of minor importance can also contribute to enhance the alteration of the deposits formed by hydrothermal and deuteric processes the extent and type of occurrences are mainly controlled by the local geological and structural features and the environmental geochemical conditions kaolin occurs in three main districts at romana and tresnuraghes it is hosted within ignimbritic sequences while at serrenti furtei it is found in pyroclastic flows and ash flow tuffs kaolin formed by hydrothermal processes occurs in high sulfidation romana and serrenti furtei and low sulfidation tresnuraghes type epithermal systems the alteration is proximal to the feeder conduits and structural setting controls kaolin formation bentonite is widespread throughout sardinia deposits occur as stratiform mineral bodies in situ altered within poor welded pumice rich and ash rich layers and also as distal fall out deposits as lenticular bodies interlayered within the miocene sedimentary sequences the former originated by deuteric alteration and formation is mainly controlled by lithology whereas the second type originated by weathering which altered the volcanic ash lenses deposited in lacustrine and or fluvial deltaic environments

physical and climatic parameters which influence the air content in polar ice abstract under present day climatic conditions the air content of polar ice v generally shows a high sensitivity to the atmospheric pressure and hence to the surface elevation of the ice sheet wherethe ice is formed the results presented here are from sixteen different sites fourteen in antartica one in greenland and one in the yukon territories canada and they allow a better understanding of the parameters which influence the air content in ice it is demonstrated the v can be expressed very simply as a function of the atmospheric pressure p i the temperature t i and the porous volume of ice v i at which the air in the firn becomes isolated in terms of pressure from the atmosphere during the process of pore close off our results confirm a v i increase with temperature and show no clear v i dependence on snow accumulation rate the possible non linearity of the v i t i relation we obtain could be due to a wind influence on v i and or to a second order effect of the accumulation rate our v i results are compared to measurements of the volume of closed pores versus depth in the firn to close we discuss the parameterization that we can obtain to interpret the air content variations observed in deep ice cores over periods covering glacial interglacial transitions in terms of paleoclimatic conditions prevailing at the surface of the ice sheet

undercutting of marine terminating glaciers in west greenland marine terminating glaciers control most of greenland s ice discharge into the ocean but little is known about the geometry of their frontal regions here we use side looking multibeam echo sounding observations to reveal that their frontal ice cliffs are grounded deeper below sea level than previously measured and their ice faces are neither vertical nor smooth but often undercut by the ocean and rough deep glacier grounding enables contact with subsurface warm salty atlantic waters aw which melts ice at rates of meters per day we detect cavities undercutting the base of the calving faces at the sites of subglacial water sgw discharge predicted by a hydrological model the observed pattern of undercutting is consistent with numerical simulations of ice melt in which buoyant plumes of sgw transport warm aw to the ice faces glacier undercutting likely enhances iceberg calving impacting ice front stability and in turn the glacier mass balance

heat sources for glacial ice melt in a west greenland tidewater outlet glacier fjord the role of subglacial freshwater discharge the melting of tidewater outlet glaciers from the greenland ice sheet contributes significantly to global sea level rise accelerated mass loss is related to melt processes in front of calving glaciers yet the role of ocean heat transports is poorly understood here we present the first direct measurements from a subglacial plume in front of a calving tidewater outlet glacier surface salinity in the plume corresponded to a meltwater content of 7 which is indicative of significant entrainment of warm bottom water and according to plume model calculations significant ice melt energy balance of the area near the glacier showed that ice melt was mainly due to ocean heat transport and that direct plume associated melt was only important in periods with high meltwater discharge rates of 100 m3 s 1 ocean mixing outside of the plume area was thus the primary heat source for melting glacier ice

seasonal variability of submarine melt rate and circulation in an east greenland fjord 1 the circulation in a glacial fjord driven by a large tidewater glacier is investigated using a nonhydrostatic ocean general circulation model with a melt rate parameterization at the vertical glacier front the model configuration and water properties are based on data collected in sermilik fjord near helheim glacier a major greenland outlet glacier the approximately two layer stratification of the fjord s ambient waters causes the meltwater plume at the glacier front to drive a double cell circulation with two distinct outflows one at the free surface and one at the layers interface in summer the discharge of surface runoff at the base of the glacier subglacial discharge causes the circulation to be much more vigorous and associated with a larger melt rate than in winter the simulated double cell circulation is consistent in both seasons with observations from sermilik fjord seasonal differences are also present in the vertical structure of the melt rate which is maximum at the base of the glacier in summer and at the layers interface in winter simulated submarine melt rates are strongly sensitive to the amount of subglacial discharge to changes in water temperature and to the height of the layers they are also consistent with those inferred from simplified one dimensional models based on the theory of buoyant plumes our results also indicate that to correctly represent the dynamics of the meltwater plume care must be taken in the choice of viscosity and diffusivity values in the model

externally forced fluctuations in ocean temperature at greenland glaciers in non summer months the factors that control the submarine melt rate at greenland s glaciers are uncertain and largely inferred from brief summer surveys in the fjords where glaciers terminate continuous records of water properties and velocity for the months september to may from two large greenland fjords reveal strong variability on 3 to 10 day timescales as a result of pulses of water that are propagated from the shelf ocean

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

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

ice shelf water overflow and bottom water formation in the southern weddell sea 1 cold shelf waters flowing out of the filchner depression in the southern weddell sea make a significant contribution to the production of weddell sea bottom water wsbw a precursor to antarctic bottom water aabw we use all available current meter records from the region to calculate the flux of cold water 1 9 c over the sill at the northern end of the filchner depression 1 6 0 5 sv and to determine its fate the estimated fluxes and mixing rates imply a rate of wsbw formation referenced to 0 8 c of 4 3 1 4 sv we identify three pathways for the cold shelf waters to enter the deep weddell sea circulation one path involves flow constrained to follow the shelf break the other two paths are down the continental slope resulting from the cold dense water being steered northward by prominent ridges that cross the continental slope near 36 w and 37 w mooring data indicate that the deep plumes can retain their core characteristics to depths greater than 2000 m probably aided by thermobaricity the plume water at this depth can flow at a speed approaching 1 m s 1 implying that the flow is occasionally supercritical we postulate that such supercriticality acts to limit mixing between the plume and its environment the transition from supercritical to slower more uniform flow is associated with very efficient mixing probably as a result of hydraulic jumps

the five stable noble gases are sensitive unambiguous tracers of glacial meltwater the five inert noble gases he ne ar kr and xe exhibit a unique dissolved gas saturation pattern resulting from the formation and addition of glacial meltwater to seawater he and ne become oversaturated and ar kr and xe become undersaturated to varying percentages for example addition of 10 glacial meltwater to seawater results in a saturation anomaly of he 12 8 ne 8 9 ar 0 5 kr 2 2 and xe 3 3 this pattern in noble gas saturation reflects a unique meltwater signature that is distinct from the other major physical processes that modify the gas concentration and saturation namely seasonal changes in temperature at the ocean surface and bubble mediated gas exchange we use optimum multiparameter analysis to illustrate how all five noble gases can help distinguish glacial meltwater from wind driven bubble injection making them a potentially valuable suite of tracers for glacial melt and its concentration in the deep waters of the world ocean