rapid circulation of warm subtropical waters in a major glacial fjord in east greenland the recent rapid increase in mass loss from the greenland ice sheet is primarily attributed to an acceleration of outlet glaciers oceanographic data obtained in summer 2008 show that subtropical waters that reside year round in the shelf ocean off greenland continuously enter a large glacial fjord in east greenland and contribute to melting at the glacier terminus the recent rapid increase in mass loss from the greenland ice sheet1 2 is primarily attributed to an acceleration of outlet glaciers3 4 5 one possible cause of this acceleration is increased melting at the ice ocean interface6 7 driven by the synchronous warming8 9 10 of subtropical waters offshore of greenland however because of the lack of observations from greenland s glacial fjords and our limited understanding of their dynamics this hypothesis is largely untested here we present oceanographic data collected in sermilik fjord east greenland by ship in summer 2008 and from moorings our data reveal the presence of subtropical waters throughout the fjord these waters are continuously replenished through a wind driven exchange with the shelf where they are present all year the temperature and renewal of these waters indicate that they currently cause enhanced submarine melting at the glacier terminus key controls on the melting rate are the volume and properties of the subtropical waters on the shelf and the patterns of along shore winds suggesting that the glaciers acceleration has been triggered by a combination of atmospheric and oceanic changes our measurements provide evidence for a rapid advective pathway for the transmission of oceanic variability to the ice sheet margins

initiation of the neomagmatism in east anatolia abstract in eastern anatolia the neotectonic episode commenced with the complete elemination of the neo tethyan ocean floor as a result of collision between arabia and eurasia during early miocene time after the collision continuing convergence initiated a new tectonic regime and coeval magmatic activity the post collisional convergence caused crustal shortening and thickening as evidenced by regionwide development of e w trending folds and thrusts and conjugate strike slip faults the related volcanic activity has progressed in three cycles in the initial cycle weakly alkaline volcanic rocks were produced that are known as the solhan volcanics they outcrop at the western end of an e w striking neotectonic depression called the mus basin which constitutes the western prolongation of the lake van basin the basin is a thrust bounded depression that developed out of an original syncline by the disruption of its limbs the lavas of the first cycle reached the surface along n s aligned extensional structures in the second volcanic cycle a widespread k type ca volcanism occurred through crustal contribution during the late miocene early pliocene time when the continuing north south convergence caused substantial shortening and thickening of the continental crust the last volcanic cycle produced a thick volcanic cover consisting of rocks of alkaline affinity during the pleistocene and the quaternary when the thickened crust began to accommodate the ongoing north south shortening by east west extension after the formation of the east and north anatolian transform faults

the geophysics of a restless caldera long valley california at 9 33 pdt on the morning of may 25 1980 a strong earthquake of local magnitude ml 6 1 heralded the onset of an earthquake sequence that focused worldwide attention on the major geologic and tectonic fea ture nearest its epicenter the long valley caldera of eastern california this sequence included two additional ml 6 events on may 25 and a fourth ml 6 event on may 27 accompanied by more than 300 ml 3 aftershocks over the next several weeks all of which were located either within or to the south of the caldera uhrhammer ferguson 1980 cramer toppozada 1980 these were not the first major events to occur regionally within the last decade the october 4 1978 bishop event m l 5 7 located some 20 km to the southeast of long valley initiated a sequence of swarm like activity that migrated generally toward the caldera over the next two years ryall ryall 1980 van wormer ryall 1980 in fact van wormer ryall 1980 in a manuscript written prior to the may 1980 earthquakes identified this sequence of events as a

local gravity anomalies produced by dislocation sources rundle 1978 and walsh and rice 1979 have shown that the change in the vertical component of gravity is proportional to uplift for a spherical source of dilatation and for slip on an infinitely long dip slip fault in the first case no free air gravity anomaly is produced and in the second case no bouguer gravity anomaly gravity anomalies due to other dislocation sources in three dimensions are as follows for strike slip faulting the ratio of the gravity change to uplift depends upon position however the gravity change contours are roughly similar to those corresponding to a zero free air gravity anomaly nor is the ratio constant for dip slip faulting except for the two special cases of dip slip on a vertical fault and horizontal slip on a horizontal fault neither of which produce a bouguer anomaly the bouguer anomaly produced by an open horizontal crack is the same as would be produced had the material within the crack been mined out without deforming the solid if the horizontal crack were filled with material of density equal to the host rock a good approximation to sill formation no bouguer anomaly is produced for cracks of other inclinations the ratio of gravity change to uplift is not constant thus dilatancy in general does not correspond to the absence of a free air anomaly as might be suggested by the special case of a spherical source of dilatation for two dimensional models a cylindrical source of dilatation produces no free air gravity anomaly dip slip faulting produces no bouguer anomaly and open cracks produce a bouguer anomaly equal to that which would be produced had the material within the crack been mined out without deforming the solid a two dimensional crack filled with material of density equal to that of the host rock would produce no bouguer anomaly jachens et al 1983 have reported temporal changes in gravity elevation and area strain along the san andreas fault in southern california such that the bouguer anomaly apparently remains unchanged and the uplift to strain ratio is about 100 km several dislocation mechanisms are proposed that fulfill these constraints but these mechanisms appear to be rather contrived and are not regarded as satisfactory explanations

the 1987 southeastern alaska gravity calibration range absolute and relative gravity measurements in june 1987 a gravimeter calibration range was set up in southeastern alaska and the yukon territory as part of a geophysical determination of the newtonian gravitational constant absolute gravity measurements were made between the range endpoints using the institute of geophysics and planetary physics absolute gravity meter the calibration range spans 171 841 0 014 mgal with a midpoint g value of 9 81746500 ms 2 relative gravity meters including a lacoste and romberg borehole gravity meter were read along this range a scale factor correction sfc for borehole meter 14 was found to be 8 1 1 5 10 4 and for meter g 349 the correction was 3 3 1 7 10 4 the sfc for meter d 85 has an upper bound of 1 0 10 4

analysis of two color geodimeter measurements of deformation within the long valley caldera june 1983 to october 1985 line length changes from several baselines in a trilateration network within the long valley caldera clearly define a decrease in strain rate from june 1983 through october 1985 the data consist of more than 1600 length measurements on 23 baselines using a two color geodimeter which has a precision of 0 2 ppm of the line length initial measurements made during the summer of 1983 show extension rates were as high as 6 ppm yr on some baselines the rates subsequently decreased steadily to less than 1 ppm yr during the summer of 1985 ih contrast the strain rates on a few other baselines were less than 0 2 ppm yr averaged over the 2 3 year interval a model is constructed using these observations as well as yearly observations of a trilateration network within and near the caldera the model contains two points of inflation located at 5 and 10 km beneath the resurgent dome of the caldera plus dextral slip on a fault plane within the south moat within an elastic half space to mimic the observed time dependence in the two color geodimeter data we conclude that the rates of both slip and inflation have steadily decreased over the survey interval because the two color geodimeter network is closer to all three sources than the single color geodimeter network these data are important for defining the factor of 2 3 rate decrease of slip and inflation comparing our estimates of slip and inflation with similar estimates for the year prior to july 1983 we conclude that the rate decrease is probably a result of postseismic and postinflation relaxation following the earthquake swarm in the south moat in january 1983

deformation gravity and potential changes due to volcanic loading of the crust a method for calculating deformation gravity and potential changes induced by volcanic loads imposed within and on the earth s crust is presented the method involves application of techniques developed for earthquake loading problems in elastic gravitational earth models by considering the elastic gravitational equilibrium of the layered system the gravitational and displacement response due to intruding masses and to pressurized magma chambers can be computed for applications involving seamount loading variations in the height of sea level can be calculated by requiring that seawater lie along an equipotential in continental loading problems the change in potential can be used to calculate the orthometric height cahnge as distinct from the geometric height change for some plausible loading geometries the difference between these two qunatities can be significant results for various loads and earth structures are shown and discussed in particular a magmatic mass intruding into an elastic gravitational lithosphere overlying a compressible gravitating asthenosphere produces distinct gravity anomalies which depend on the depth of intrusion applications of this result can be made to problems of isostatic compensation the intrusion of a magmatic mass together with the associated pressurization of the magma chamber produces distinctive surface gravity and deformation in the near field gravity gradients more defined as surface gravity divided by uplift vary with distance from the source moreover orthometric elevations can be significantly 25 less than geometric elevations these results have clear application to data from events such as the posteruption deflation of kilauea volcano less

deformation induced by polar motion variations in the geocentric position of the earth s rotation axis polar motion cause deformation within the earth we estimate the effects of this deformation on radial and horizontal positions of points on the earth s surface on baseline lengths between those points and on surface gravity the effects of the oceans and of the earth s anelasticity on this deformation are found to be negligible peak to peak variations in radial motion are typically 10 20 mm over a year horizontal displacements are less than 7 8 mm variations in baseline length can be as large as 30 40 mm variations of up to 13 gal in surface gravity are possible these numbers are all small enough that they can probably not be used to learn about the earth however they are large enough to affect noticeably present high quality geodetic observations

chemical evolution of a gas capped deep aquifer southwest of iran the kangan aquifer ka is located below a gas reservoir in the crest of the kangan anticline southwest of iran this aquifer is composed of permo triassic limestone dolomite sandstone anhydrite and shale it is characterized by a total dissolved solid of about 332 000 mg l and na ca cl type water a previous study showed that the source of the ka waters is evaporated seawater chemical evolution of the ka is the main objective of this study the major minor and trace element concentrations of the ka waters were measured the chemical evolution of ka waters occurred by three different processes evaporation of seawater water rock and water gas interactions due to the seawater evaporation process the concentration of all ions in the ka waters increased up to saturation levels in comparison to the evaporated seawater the higher concentrations of ca li sr i mn and b and lower concentrations of mg so4 and na and no changes in concentrations of cl and k ions are observed in the ka waters based on the chemical evolution after seawater evaporation the ka waters are classified into four groups 1 no evolution cl k ions 2 water rock interaction na ca mg li and sr ions 3 water gas interaction so4 and i ions and 4 both water rock and water gas interactions mn and b ions the chemical evolution processes of the ka waters include dolomitization precipitation ion exchange and recrystallization in water rock interaction bacterial reduction and diagenesis of organic material in water gas interaction also occur a new type of chart caexcess versus mgdeficit is proposed to evaluate the dolomitization process

displacements of the earth s surface due to atmospheric loading effects on gravity and baseline measurements atmospheric mass loads and deforms the earth s crust by performing a convolution sum between daily global barometric pressure data and mass loading green s functions we estimate the time dependent effects of atmospheric loading including those associated with short term synoptic storms on surface point positioning measurements and surface gravity observations we calculate the response for both an oceanless earth and an earth with an inverted barometer ocean load responses for near coastal stations are significantly affected by the inclusion of an inverted barometer ocean peak to peak vertical displacements are frequently 15 20 mm with accompanying gravity perturbations of 3 6 gal baseline changes can be as large as 20 mm or more the perturbations are largest at higher latitudes and during winter months these amplitudes are consistent with the results of rabbel and zschau 1985 who modeled synoptic pressure disturbances as gaussian functions of radius around a central point deformation can be adequately computed using real pressure data from points within about 1000 km of the station knowledge of local pressure alone is not sufficient rabbel and zschau s hypothesized corrections for these displacements which use local pressure and the regionally averaged pressure prove accurate at points well inland but are in general inadequate within a few hundred kilometers of the coast

absolute gravity a reconnaissance tool for studying vertical crustal motions a major effort is underway to develop highly portable absolute gravimeters having an ultimate accuracy of 3 5 gal an accuracy which translates into a height sensitivity of several centimeters we are just finishing the construction of six such units measurements at the joint institute for laboratory astrophysics with one of these new instruments agree well with the earlier measurements made in 1981 and 1982 with a previous generation instrument recent measurements at the international bureau of weights and measures in sevres france as a part of an international intercomparison of absolute gravimeters also show good agreement with the other instruments

potential effects of ongoing postglacial adjustment on very long baseline interferometry measurements very long baseline interferometry vlbi has the potential to estimate the rates of postglacial adjustment across northern north america by employing glacial isostatic adjustment theory the radial rates of uplift or subsidence were computed at five vlbi sites the expected rates of baseline extension or reduction between these sites and seven static sites with respect to postglacial adjustment were estimated these first order estimates may act as a guide in organizing a vlbi network to measure ongoing postglacial adjustment and help determine how many years would be required to observe the deglaciation signal ideally using a network which includes sites in the region of maximum postglacial uplift and sites in the southern united states this signal should be observed in 10 years of annual measurements

structure propagation and mixing of energetic baroclinic tides in mamala bay oahu hawaii abstract large semidiurnal vertical displacements 100 m and strong baroclinic currents 0 5 m s 1 several times as large as barotropic currents dominate motions in mamala bay outside the mouth of pearl harbor hawaii during september 2002 the authors sought to characterize them with a 2 month mclane moored profiler deployment and a 4 day intensive survey with a towed ctd adcp and the research vessel r v revelle hydrographic sonar spatial maps and time series of turbulent dissipation rate diapycnal diffusivity k isopycnal displacement velocity u energy e and energy flux f are presented dissipation rate peaks in the lower 150 m during rising isopycnals and high strain and shows a factor of 50 spring neap modulation the largest k values in the western bay near a submarine ridge exceed 10 3 m2 s 1 the m2 phases of and u increase toward the west implying a westward phase velocity cp 1 m s 1 and horizontal wavelength 60 km consistent with theoretical mode 1 values these phase

absolute gravity measurements in california we have constructed an absolute gravity meter that determines the local gravitational acceleration by timing a freely falling mass with a laser interferometer the instrument has made measurements at 11 sites in california four in nevada and one in france the uncertainty in the results is typically 10 gal 1 gal 1 cm s2 1 gal 10 6 gal 10 8 m s2 repeated measurements have been made at several of the sites only one shows a substantial change in gravity

estuarine versus transient flow regimes in juan de fuca strait 1 residual currents in juan de fuca strait are observed to switch between two fundamental states estuarine and transient the estuarine regime which prevails roughly 90 of the time in summer and 55 of the time in winter has a fortnightly modulated three layer structure characterized by strong 50 cm s 1 outflow above 60 15 m depth moderate 25 cm s 1 inflow between 60 and 125 m depth and weak 10 cm s 1 inflow below 125 10 m depth rotation increases the upper layer depth by 40 m on the northern side of the channel and upwelling favorable coastal winds augment inflow in the bottom layer by as much as 5 cm s 1 rotation combined with modulation of the estuarine currents by tidal mixing in the eastern strait leads to fortnightly variability in the along channel velocity and cross channel positioning of the core flow regions transient flows which occur roughly 10 of the time in summer and 45 of the time in winter are rapidly evolving horizontally and vertically sheared reversals in the estuarine circulation generated during poleward wind events along the outer coast major events can persist for several weeks force a net inward transport and give rise to an o 10 km wide surface intensified o 100 cm s 1 inflow along the southern olympic peninsula boundary of the strait this olympic peninsula countercurrent is typically accompanied by an abrupt decrease in salinity indicating that it is a buoyancy flow originating with low density water on the northern washington shelf

absolute gravity measurements in california 1984 1989 repeated absolute gravity measurements have been made at 12 sites in california between 1984 3 and 1989 7 as determined in laboratory tests the instrument used has an estimated accuracy of 10 gal approximately 10 8 g the repeatability of the measurements is consistent with this accuracy assessment no gravity changes above the limits set by instrumental uncertainty and environmental noise are observed in california during this period the field observations provide upper limits on the rates of secular gravity changes which could be attributed to crustal deformation with a resolution corresponding to vertical displacement rates of 1 2 cm yr

principal component analysis of geodetically measured deformation in long valley caldera eastern california 1983 1987 typical geodetic measurements of deformation consist of repeated surveys of a particular geodetic network such deformation data can be interpreted as a consequence of one or more self coherent sources by means of principal component analysis a self coherent source is defined as any source that produces deformation that is time and space separable principal component analysis then gives the time and space factors that characterize the deformation attributed to each self coherent source geodetic measurements of deformation at long valley caldera provide two examples of the application of principal component analysis a 40 line trilateration network surrounding the caldera was surveyed in midsummer 1983 1984 1985 1986 and 1987 principal component analysis indicates that the observed deformation can be represented by a single coherent source the time dependence for that source displays a rapid rate of deformation in 1983 1984 followed by less rapid but uniform rate in the 1984 1987 interval the spatial factor seems consistent with expansion of a magma chamber beneath the caldera plus some shallow right lateral slip on a vertical fault in the south moat of the caldera an independent principal component analysis of the 1982 1983 1984 1985 1986 and 1987 leveling across the caldera requires two self coherent sources to explain the deformation the deformation pattern produced by the larger of these two sources appears to be roughly consistent with that found from the trilateration data the deformation due to the second source is a nearly uniform tilt in the uplift profile presumably that tilt is simply an artifact of systematic error in the leveling

variation in the position of the upwelling front on the oregon shelf 1 as part of an experiment to study wind driven coastal circulation 17 hydrographic surveys of the middle to inner shelf region off the coast of newport or 44 65 n from roughly the 90 m isobath to the 10 m isobath were performed during summer 1999 with a small towed undulating vehicle the cross shelf survey data were combined with data from several other surveys at the same latitude to study the relationship between upwelling intensity and wind stress field a measure of upwelling intensity based on the position of the permanent pycnocline is developed this measure is designed so as to be insensitive to density modifying surface processes such as heating cooling buoyancy plumes and wind mixing it is highly correlated with an upwelling index formed by taking an exponentially weighted running mean of the alongshore wind stress this analysis suggests that the front relaxes to a dynamic geostrophic equilibrium on a timescale of roughly 8 days consistent with a similar analysis of moored hydrographic observations this relationship allows the amount of time the pycnocline is outcropped to be estimated and could be used with historical wind records to better quantify interannual cycles in upwelling

flow and mixing in juan de fuca canyon washington we report breaking internal lee waves strong mixing and hydraulic control associated with wind driven up canyon flow in juan de fuca canyon washington unlike the flow above the canyon rim which shows a tidal modulation typical on continental shelves the flow within the canyon is persistently up canyon during our observations with isopycnals tilted consistent with a geostrophic cross canyon momentum balance as the flow encounters a sill near the canyon entrance at the shelf break it accelerates significantly and undergoes elevated mixing on the upstream and downstream sides of the sill on the downstream side a strong lee wave response is seen with displacements of o 100 m and overturns tens of meters high the resulting diffusivity is o 10 2 m2 s 1 sufficient to substantially modify coastal water masses as they transit the canyon and enter the salish sea estuarine system

terrestrial and planetary gravity fields the determination of the gravity field together with knowledge of the surface topography provides one of the primary means of inferring the density structure and dynamics of planetary interiors phillips and lambeck 1980 hager 1985 after removing the topographic gravity signal the distribution of internal density anomalies caused by thermal or compositional differences can be studied gravity field models can also be used to study the compensation of surface topography which can provide information on the mechanical properties and state of stress of the lithosphere the determination of these models has been accomplished using a wide variety of different measurement types and solution techniques the near earth measurement types can be divided into satellite tracking measurements surface gravity measurements and satellite altimeter measurements in both near earth and interplanetary contexts tracking data are used to measure gravitational perturbations affecting satellites with the accuracy and spatial temporal distribution of the data being the most important factors in the resulting field accuracy and resolution surface gravity data provide a more direct measurement of the gravity field but acquiring data uniformly over the earth has always been difficult satellite altimetry provides precise measurements of the marine gravity field provided that satellite orbit errors and non geoidal sea surface height variations can be adequately modeled comprehensive gravity field solutions must incorporate these disparate data types in order to estimate mathematical parameters describing the gravity field such as spherical harmonic coefficients the proper combination of these data along with the desire to acquire an accurate representation of the model errors require that complex procedures be developed for computing these solutions

carbonate weathering and connate seawater influencing karst groundwaters in the gevas gurpinar guzelsu basins turkey there are 59 springs at the gevas gurpinar guzelsu basins 38 of these springs emerge from the fractured karst aquifers recrystallized limestone and travertine and 21 emerge from the yuksekova ophiolites kirkgecit formation and alluvium the groundwater samples collected from 38 out of the total of 59 springs two streams one lake and 12 wells were analyzed physico chemically in the year 2002 ec and tds values of groundwater increased from the marble high altitude to the ophiolites and alluvium toward lake van as a result of carbonate dissolution and connate seawater five chemical types of groundwater are identified ca mg hco3 mg ca hco3 mg na hco3 na ca hco3 and mg ca na hco3 the calculations and hydrochemical interpretations show that the high concentrations of ca2 mg2 and hco3 as predominant ions in the waters are mainly attributed to carbonate rocks and high pco2 in soil most of the karst springs are oversaturated in calcite aragonite and dolomite and undersaturated in gypsum halite and anhydrite the water rock interaction processes that singly or in combination influence the chemical composition of each water type include dissolution of carbonate calcite and dolomite calcite precipitation cation exchange and freshening of connate seawater these processes contribute considerably to the concentration of major ions in the groundwater stable isotope contents of the groundwater suggest mainly direct integrative recharge