el nino la nina and sahel precipitation during the middle holocene simulations with a synchronously coupled atmo sphere land ocean sea ice model indicate el nino la nina like events in the eastern tropical pacific ocean during the middle holocene 6 ka with similar intensities and frequencies as at present 0 ka july august september sahel precipitation shifts northward as expected from proxy data for present day interannual decadal variability of western sahel precipi tation is correlated with both pacific el nino la nina sea sur face temperature sst anomalies and the atlantic dipole teleconnections at 6 ka between sahel precipitation and el nino la nina sst anomalies are absent with tropical atlantic ssts asserting a dominant influence these results illustrate potential problems with using present day teleconnection patterns in interpreting past climate variability from proxy data

south atlantic multidecadal variability in the climate system model abstract strong multidecadal variability is detected in a 300 yr integration of the ncar climate system model in the south atlantic region through the application of two signal recognition techniques the multitaper method and singular spectrum analysis significant oscillations of a 25 30 yr period are found in the sea surface temperature sea level pressure and barotropic transport fields a similar scale signal is also captured in about one century long observational records a composite analysis of several model variables is performed based on the extremes of the sea surface temperature oscillation the proposed mechanism for this basin scale multidecadal signal involves changes in the intensity of the westerlies associated with variability in the southward extension of the subtropical anticyclone which drives changes in the ocean mass transport this results in variability in the intensity of the malvinas western boundary current and in the position of the brazil malvinas confluence zone anomalo

development of a sea ice model for use in zonally averaged energy balance climate models abstract a sea ice model for use in zonally averaged energy balance climate models is presented which includes the following processes surface melting basal freezing and melting lateral melting from ice flee water or growth of new ice in leads snowfall and the formation of white ice ice advection and a parameterized ice and snow thickness distribution which represents the effects of small scale dynamics the ice growth equations of hibler are solved analytically thereby permitting a gradual increase in zonal ice fraction in fall and winter both lateral and vertical melting lead to a continuous decrease of ice fraction during ice decay the correlation between ice thickness and ice thickness sensitivity to the upward heat flux at the ice base is of opposite sign seasonally and latitudinally the parameterized feedback between ice thickness and the minimum permitted lead fraction is found to be very important to the ice simulation and is a process which needs to be studied using higher resolution

asperities and barriers on the seismogenic zone in north chile state of the art after the 2007 mw 7 7 tocopilla earthquake inferred by gps and insar data the mw 7 7 2007 november 14 earthquake had an epicentre located close to the city of tocopilla at the southern end of a known seismic gap in north chile through modelling of global positioning system gps and radar interferometry insar data we show that this event ruptured the deeper part of the seismogenic interface 30 50 km and did not reach the surface the earthquake initiated at the hypocentre and was arrested 150 km south beneath the mejillones peninsula an area already identified as an important structural barrier between two segments of the peru chile subduction zone our preferred models for the tocopilla main shock show slip concentrated in two main asperities consistent with previous inversions of seismological data slip appears to have propagated towards relatively shallow depths at its southern extremity under the mejillones peninsula our analysis of post seismic deformation suggests that small but still significant post seismic slip occurred within the first 10 d after the main shock and that it was mostly concentrated at the southern end of the rupture the post seismic deformation occurring in this period represents 12 19 per cent of the coseismic deformation of which 30 55 per cent has been released aseismically post seismic slip appears to concentrate within regions that exhibit low coseismic slip suggesting that the afterslip distribution during the first month of the post seismic interval complements the coseismic slip the 2007 tocopilla earthquake released only 2 5 per cent of the moment deficit accumulated on the interface during the past 130 yr and may be regarded as a possible precursor of a larger subduction earthquake rupturing partially or completely the 500 km long north chile seismic gap

monitoring subsidence at messara basin using radar interferometry the messara valley is the largest and most productive region in the island of crete greece over the last 20 years extensive exploitation of the aquifer mainly for agricultural purposes has led to a 40 m decrease in the level of groundwater this investigation aims at mapping ground subsidence that might be induced by such overpumping of groundwater using conventional differential interferometry a total of 29 ers 1 and 2 sar and 7 alos palsar images have been used for forming interferograms the images used cover the period from 1992 to 2000 and 2007 to 2010 respectively processing of alos l band data 23 6 cm has revealed a ground motion away from the line of sight of the satellite los direction that amounts to at least 3 cm year for the period 2007 2010 piezometric measurements and other geological parameters have also been analyzed

effect of ocean gateways on the global ocean circulation in the late oligocene and early miocene 1 we investigate the effect of changes in the tectonic boundary conditions on global ocean circulation patterns using a fully coupled climate model in an idealized setup we compare situations corresponding to the late oligocene the early miocene and present day the model results show the existence of a flow reversal through the panama seaway between the oligocene and miocene this flow reversal is induced by global tectonic changes related to the widening of the southern ocean passages and the closing of the tethys seaway it mainly involves the wind driven ocean circulation in agreement with previous model studies the global thermohaline circulation in the oligocene and miocene simulations is significantly different from the present day conveyor circulation as there is deepwater formation in both the north atlantic and the north pacific oceans in particular in the oligocene simulation the salinity contrast between the atlantic and pacific oceans is reduced because of water mass exchange through the low latitude connections between the two oceans

recent advances in sar interferometry time series analysis for measuring crustal deformation abstract synthetic aperture radar sar interferometry is a technique that permits remote detection of deformation at the earth s surface and has been used extensively to measure displacements associated with earthquakes volcanic activity and many other crustal deformation phenomena analysis of a time series of sar images extends the area where interferometry can be successfully applied and also allows detection of smaller displacements through the reduction of error sources here we review recent advances in time series sar interferometry methods that further improve accuracy this is particularly important when constraining displacements due to processes with low strain rates such as interseismic deformation we include examples of improved algorithms applied to image deformation associated with the 2010 eruption of eyjafjallajokull volcano in iceland slow slip on the guerrero subduction zone in mexico and tectonic deformation in western anatolia turkey

a mechanism of decadal variability of the sea ice volume in the northern hemisphere a long term simulation performed with a coarse resolution global atmosphere ocean sea ice model displays strong decadal variability of the sea ice volume in the northern hemisphere with a significant peak at about 15 18 years this model results from the coupling of ecbilt a spectral t21 3 level quasi geostrophic atmospheric model and clio a sea ice ocean general circulation model first the mechanism underlying the variability of ice volume in the model was studied by performing correlation analyses between the simulated variables in a second step a series of additional sensitivity experiments was performed in order to illustrate the role of specific physical processes this as allowed us to identify a feedback loop in the ice ocean system which proceeds as follows an increase in at tic sea ice volume induces an increase in the salinity there this salinity anomaly is transported to the greenland sea where it promotes convective activity this warms up the surface oceanic layer and the atmosphere in winter and induces a decrease of the ice volume completing half a cycle the changes in ice volume are driven by a geopotential height pattern characterised by centres of action of opposite signs over greenland and the barents kara central arctic area thermodynamic feedback between the ice and the atmosphere appear also to be very important for the persistence of the oscillation the dynamical response of the atmosphere to sea ice and temperature anomalies at surface plays a smaller role

the asian australian monsoon and el nino southern oscillation in the ncar climate system model features associated with the asian australian monsoon system and el nino southern oscillation enso are described in the national center for atmospheric research ncar global coupled climate system model csm simulation characteristics are compared with a version of the atmospheric component of the csm the ncar ccm3 run with time evolving ssts from 1950 to 1994 and with observations the csm is shown to represent most major features of the monsoon system in terms of mean climatology interannual variability and connections to the tropical pacific this includes a representation of the southern oscillation links between strong asian australian monsoons and associated negative sst anomalies in the eastern equatorial pacific the equatorial sst gradient across the pacific in the csm is shown to be similar to the observed with somewhat cooler mean ssts across the entire pacific by about 18 28c the seasonal cycle of ssts in the eastern equatorial pacific has the characteristic signature seen in the observations of relatively warmer ssts propagating westward in the first half of the year followed by the reestablishment of the cold tongue with relatively colder ssts propagating westward in the second half of the year like other global coupled models the propagation is similar to the observed but with the establishment of the relatively warmer water in the first half of the year occurring about 1 2 months later than observed the seasonal cycle of precipitation in the tropical eastern pacific is also similar to other global coupled models in that there is a tendency for a stronger than observed double itcz year round particularly in northern spring but with a well reproduced annual maximum of itcz strength north of the equator in the second half of the year time series of area averaged ssts for the nino3 region in the eastern equatorial pacific show that the csm is producing about 60 of the amplitude of the observed variability in that region consistent with most other global coupled models global correlations between nino3 time series global surface temperatures and sea level pressure slp show that the csm qualitatively reproduces the major spatial patterns associated with the southern oscillation lower slp in the central and eastern tropical pacific when nino3 ssts are relatively warmer and higher slp over the far western pacific and indian oceans with colder water in the northwest and southwest pacific indices of asian australian monsoon strength are negatively correlated with nino3 ssts as in the observations spectra of time series of indian monsoon australian monsoon and nino3 sst indices from the csm show amplitude peaks in the southern oscillation and tropospheric biennial oscillation frequencies 3 6 yr and about 2 3 yr respectively as observed lag correlations between the nino3 sst index and upper ocean heat content along the equator show eastward propagation of heat content anomalies with a phase speed of about 0 3 m s21 compared to observed values of roughly 0 2 m s21 composites of el nino la nina events in the csm show similar seasonal evolution to composites of observed events with warming cooling of greater than several tenths of a degree beginning early in northern spring of year 0 and diminishing around northern spring of year 11 but with a secondary resurgence in the csm events later in northern spring of year 11 the csm also shows the largest amplitude enso sst and low level wind anomalies in the western tropical pacific with enhanced interannual variability of ssts extending northeastward and southeastward toward the subtropics compared to largest interannual sst variability in the central and eastern tropical pacific in the observations

first delimitation of areas affected by ground deformations in the guadalfeo river valley and granada metropolitan area spain using the dinsar technique abstract a differential interferometric sar dinsar analysis of terrain displacements in the province of granada southern spain is presented here for two different study zones the first zone concerns the guadalfeo river basin where abundant landslides and unstable slopes were previously identified and inventoried on a gis application however no instrumental quantification of landslide activity was available considering morphological criteria and field observations these deep seated landslides were considered to be dormant or moving extremely slowly the second study zone corresponds to the granada metropolitan area where no previous information was available on any vertical movement the analysis was based on ers1 and ers2 images covering the period from 1993 to 2000 by using dinsar we made an initial qualitative assessment of movements on landsliding slopes in the guadalfeo river basin and also vertical land movements in the alluvial quaternary sediments to the west and south of the granada metropolitan area the terrain instability assessment resulting from this research shows maximum annual velocities along the sar line of sight los of 6 mm yr for the tablones landslide and up to 13 mm yr for the albunuelas village where progressive differential settlement processes were established as the origin of the movement in the case of the granada metropolitan area two sites were detected with subsidence affecting two villages santa fe located in the western part of the area with an estimated average velocity of 8 mm yr and otura in the south of the area with maximum velocities of 12 mm yr a description of geological features of the different sites showing los ground displacement is presented with a discussion of the application of the rates to landslide activity assessment found local ground conditions or exploitation of subterranean water in urban areas

effects of rheology and ice thickness distribution in a dynamic thermodynamic sea ice model realistic treatment of sea ice processes in general circulation models is needed to simulate properly global climate and climate change scenarios as new sea ice treatments become available it is necessary to evaluate them in terms of their accuracy and computational time here several dynamic ice models are compared using both a 2 category and 28 category ice thickness distribution simulations are conducted under normal wind forcing as well as under increased and decreased wind speeds it is found that the lack of a shear strength parameterization in the cavitating fluid rheology produces significantly different results in both ice thickness and ice velocity than those produced by an elliptical rheology furthermore use of a 28 category ice thickness distribution amplifies differences in the responses of the various models while the choice of dynamic model is governed by requirements of accuracy and implementation it appears that in terms of both parameterization of physical properties and computational time the elliptical rheology is well suited for inclusion in a gcm

recharge sources and hydrogeochemical evolution of groundwater in semiarid and karstic environments a field study in the granada basin southern spain abstract the objective of this study is to refine the understanding of recharge processes in watersheds representative for karstic semiarid areas by means of stable isotope analysis and hydrogeochemistry the study focuses on the granada aquifer system which is located in an intramontane basin bounded by high mountain ranges providing elevation differences of almost 2900 m these altitude gradients lead to important temperature and precipitation gradients and provide excellent conditions for the application of stable isotopes of water whose composition depends mainly on temperature samples of rain snow surface water and groundwater were collected at 154 locations for stable isotope studies 18 o d and in the case of ground and surface waters also for major and minor ion analysis thirty seven springs were sampled between 2 and 5 times from october 2004 to march 2005 along an altitudinal gradient from 552 masl in the granada basin to 2156 masl in sierra nevada nine groundwater samples were taken from the discharge of operating wells in the granada basin which are all located between 540 and 728 masl the two main rivers were monitored every 2 3 weeks at three different altitudes rainfall being scarce during the sampling period precipitation could only be sampled during four rainfall events calculated recharge altitudes of springs showed that source areas of mainly snowmelt recharge are generally located between 1600 and 2000 masl the isotope compositions of spring water indicate water sources from the western mediterranean as well as from the atlantic without indicating a seasonal trend the isotope pattern of the quaternary aquifer reflects the spatial separation of different sources of recharge which occur mainly by bankfiltration of the main rivers isotopic signatures in the southeastern part of the aquifer indicate a considerable recharge contribution by subsurface flow discharged from the adjacent carbonate aquifer no evaporation effects due to agricultural irrigation were detected

global monsoons in the mid holocene and oceanic feedback the response of the six major summer monsoon systems the north american monsoon the northern africa monsoon the asia monsoon the northern australasian monsoon the south america monsoon and the southern africa monsoon to mid holocene orbital forcing has been investigated using a coupled ocean atmosphere general circulation model foam with the focus on the distinct roles of the direct insolation forcing and oceanic feedback the simulation result is also found to compare well with the ncar csm the direct effects of the change in insolation produce an enhancement of the northern hemisphere monsoons and a reduction of the southern hemisphere monsoons ocean feedbacks produce a further enhancement of the northern africa monsoon and the north american monsoon however ocean feedbacks appear to weaken the asia monsoon although the overall effect direct insolation forcing plus ocean feedback remains a strengthened monsoon the impact of ocean feedbacks on the south american and southern african monsoons is relatively small and therefore these regions especially the south america experienced a reduced monsoon regime compared to present however there is a strong ocean feedback on the northern australian monsoon that negates the direct effects of orbital changes and results in a strengthening of austral summer monsoon precipitation in this region a new synthesis is made for mid holocene paleoenvironmental records and is compared with the model simulations overall model simulations produce changes in regional climates that are generally consistent with paleoenvironmental observations

radar interferometry and its application to changes in the earth s surface geophysical applications of radar interferometry to measure changes in the earth s surface have exploded in the early 1990s this new geodetic technique calculates the interference pattern caused by the difference in phase between two images acquired by a spaceborne synthetic aperture radar at two distinct times the resulting interferogram is a contour map of the change in distance between the ground and the radar instrument these maps provide an unsurpassed spatial sampling density 100 pixels km 2 a competitive precision 1 cm and a useful observation cadence 1 pass month 1 they record movements in the crust perturbations in the atmosphere dielectric modifications in the soil and relief in the topography they are also sensitive to technical effects such as relative variations in the radar s trajectory or variations in its frequency standard we describe how all these phenomena contribute to an interferogram then a practical summary explains the techniques for calculating and manipulating interferograms from various radar instruments including the four satellites currently in orbit ers 1 ers 2 jers 1 and radarsat the next chapter suggests some guidelines for interpreting an interferogram as a geophysical measurement respecting the limits of the technique assessing its uncertainty recognizing artifacts and discriminating different types of signal we then review the geophysical applications published to date most of which study deformation related to earthquakes volcanoes and glaciers using ers 1 data we also show examples of monitoring natural hazards and environmental alterations related to landslides subsidence and agriculture in addition we consider subtler geophysical signals such as postseismic relaxation tidal loading of coastal areas and interseismic strain accumulation we conclude with our perspectives on the future of radar interferometry the objective of the review is for the reader to develop the physical understanding necessary to calculate an interferogram and the geophysical intuition necessary to interpret it

an estimate of the mean field of arctic sea ice motion the observational basis for our understanding of sea ice motion comes from the trajectories of particular ice floes these ice floes may have been marked by a manned research station or more recently by an automatic data buoy since 1893 almost 100 station years of drift data have been recorded using the principles of optimal linear estimation these data are used to obtain a quantitative estimate of the field of mean motion

a climatology of sea ice embayments in the cosmonaut sea antarctica 1 the cosmonaut sea off the coast of antarctica is characterized by highly variable sea ice conditions as the sea ice expands during the austral fall and winter embayments open bodies of water surrounded on three sides by sea ice as well as polynyas often form using sea ice concentration data provided by satellite based passive microwave instruments from 1979 to 2004 we characterize these embayment events by their size and temporal evolution the data suggests a striking periodicity in the occurrence of these embayments with the exception of a quiet period between 1984 and 1987 the large embayment events seem to appear approximately every three years in the same location and persist for anywhere between mid june to mid august these results indicate there is predictability in the occurrence of embayment events adding important insight into the characterization of sea ice variability in this region

mid holocene climates of the americas a dynamical response to changed seasonality simulations of the climatic response to mid holocene 6 ka bp orbital forcing with two coupled ocean atmosphere models foam and csm show enhancement of monsoonal precipitation in parts of the american southwest central america and northernmost south america during northern hemisphere summer the enhanced onshore flow that brings precipitation into central america is caused by a northward displacement of the inter tropical convergence zone driven by cooling of the equatorial and warming of the northern subtropical and mid latitude ocean ocean feedbacks also enhance precipitation over the american southwest although the increase in monsoon precipitation there is largely driven by increases in land surface temperature the northward shift in the equatorial precipitation band that causes enhanced precipitation in central america and the american southwest has a negative feedback effect on monsoonal precipitation in northern south america the simulations demonstrate that mid holocene aridity in the mid continent of north america is dynamically linked to the orbitally induced enhancement of the summer monsoon in the american southwest with a spatial structure wet in the southwest and dry in the mid continent similar to that found in strong monsoon years today changes in winter precipitation along the west coast of north america in central america and along the gulf coast caused by southward displacement of the westerly storm tracks indicate that changes in the northern hemisphere winter monsoon also play a role in regional climate changes during the mid holocene although the simulations with foam and csm differ in detail the general mechanisms and patterns are common to both the model results thus provide a coherent dynamical explanation for regional patterns of increased or decreased aridity shown by vegetation lake status and aeolian data from the americas

oceanic wave dynamics and interdecadal variability in a climate system model western boundary disturbances detected in the first multicentury integration of the national center for atmospheric research climate system model are analyzed and the role they play in the model interdecadal variability is investigated the boundary signals propagate southwestward along the coast of north america at depth they reach the equator and propagate along the equator but with decreasing amplitude away from the western boundary their southwestward propagation is associated with the evolution of the western boundary current system the gulf stream system in the upper part of the water column and the deep western boundary current at depth from weaker than average to stronger than average conditions thus the boundary disturbances seem to play an important role in the model thermohaline circulation variability at interdecadal timescales they show similarities with the boundary waves found in ocean only models exhibiting interdecadal variability and their role in the model s response to changes in the rate of sinking appears to be in agreement with the theory of the spin up of the deep ocean circulation the main result of this study is that the similarities with ocean only results and theories support the idea that interdecadal timescales of variability originate from the ocean dynamics

sea ice response to wind forcing from amip models abstract the arctic surface circulation simulated by atmospheric general circulation models is assessed in the context of driving sea ice motion a sea ice model is forced by geostrophic winds from eight models participating in the first atmospheric model intercomparison project amip1 and the results are compared to simulations with the sea ice model forced by observed winds the mean sea level pressure in the amip models is generally too high over the arctic ocean except in the beaufort and chukchi seas where it is too low this pattern creates anomalous winds that tend to transport too much ice away from the coast of greenland and the canadian archipalego and into the east siberian sea producing a pattern of ice thickness in the arctic that is rotated by roughly 180 relative to what is expected based on observations amip winds also drive too little ice transport through fram strait and too much transport east of svalbard by way of the barents sea these errors in ice thickness and transport inf

tropical pacific variability in the ncar climate system model a 300 yr simulation with the ncar climate system model csm version 1 captured only 60 of the observed enso signal and exaggerated the interannual variability of sst in the western tropical pacific here a simulation with a new version of the csm which significantly improves the spatial and temporal patterns of tropical pacific variability is described maximum sst variability is shifted to the central and eastern pacific a better simulation of the equatorial pacific thermocline structure results in nino 3 and nino 4 statistics com parable to the observed estimates for the last century the evolution of sst and subsurface temperature anomalies is in excellent agreement with observed events the majority of events evolve as a standing mode with weak sst anomalies occurring in the northern spring in the eastern tropical pacific and maximum anomalies covering the eastern tropical pacific ocean to the date line by the following northern winter at the same time subsurface temperature anomalies spread eastward and upward along the tropical thermocline the delayed oscillator and wyrtki s buildup hypothesis are consistent with aspects of the csm simulation on the equator a westerly wind stress anomaly in the central pacific forces off equatorial upwelling anomalies which propagate westward reaching the western boundary about one half year later this upwelling signal then propagates eastward along the equator arriving 2 months before cooling in the eastern pacific basin the tropical pacific atmospheric response to warm oceanic events also agrees with observational analyses with a negative southern oscillation pattern in sea level pressure wind stress anomalies and low level convergence to the west of the maximum sst anomalies and enhanced deep convection and precipitation in the central and eastern tropical pacific

sensing the ups and downs of las vegas insar reveals structural control of land subsidence and aquifer system deformation land subsidence in las vegas nevada united states between april 1992 and december 1997 was measured using spaceborne interferometric synthetic aperture radar the detailed deformation maps clearly show that the spatial extent of subsidence is controlled by geologic structures faults and sediment composition clay thickness the maximum detected subsidence during the 5 75 yr period is 19 cm comparison with leveling data indicates that the subsidence rates declined during the past decade as a result of rising ground water levels brought about by a net reduction in ground water extraction temporal analysis also detects seasonal subsidence and uplift patterns which provide information about the elastic and inelastic properties of the aquifer system and their spatial variability

identification of potential subsidence related to pumping in the almeria basin se spain ground subsidence of detrital deposits in the almer ia basin se spain was studied using the remote sensing technique of differential interferometry sar dinsar this basin is one of the most arid in europe receiving an average rainfall of 250 mm per year over the last 60 years the region has experienced an enormous agricultural and urban expansion whose water demand has been largely supplied from groundwater leading to the current situation of overexploitation of water resources this paper outlines the likely relationship between groundwater abstraction and subsidence to this end 34 ers and envisat images taken between 2003 and 2009 were analysed to estimate ground surface deformations and hence compared with water table variations measured in a number of piezometers in the basin the analysis shows a clear parallelism between the variations in piezometric level and deformation of the ground surface in addition the zones of greatest subsidence coincide with those areas where groundwater abstractions are concentrated subsidence over the examined period varies from 10 to 30 mm with extreme values as high as 50 mm which translates to a rate of between 1 7 and 5 mm year reaching maximum rates of 8 mm year at some points given such subsidence rates damage to urban infrastructures are for the moment incipient

the role of sea ice and other fresh water in the arctic circulation salinity stratification is critical to the vertical circulation of the high latitude ocean we here examine the control of the vertical circulation in the northern seas and the potential for altering it by considering the budgets and storage of fresh water in the arctic ocean and in the convective regions to the south we find that the present day greenland and iceland seas and probably also the labrador sea are rather delicately poised with respect to their ability to sustain convection small variations in the fresh water supplied to the convective gyres from the arctic ocean via the east greenland current can alter or stop the convection in what may be a modern analog to the halocline catastrophes proposed for the distant past the north atlantic salinity anomaly of the 1960s and 1970s is a recent example it must have had its origin in an increased fresh water discharge from the arctic ocean similarly the freshening and cooling of the deep north atlantic in recent years is a likely manifestation of the increased transfer of fresh water from the arctic ocean into the convective gyres finally we note that because of the temperature dependence of compressibility a slight salinity stratification in the convective gyres is required to efficiently ventilate the deep ocean

radar interferometry techniques for the study of ground subsidence phenomena a review of practical issues through cases in spain subsidence related to multiple natural and human induced processes affects an increasing number of areas worldwide although this phenomenon may involve surface deformation with 3d displacement components negative vertical movement either progressive or episodic tends to dominate over the last decades differential sar interferometry dinsar has become a very useful remote sensing tool for accurately measuring the spatial and temporal evolution of surface displacements over broad areas this work discusses the main advantages and limitations of addressing active subsidence phenomena by means of dinsar techniques from an end user point of view special attention is paid to the spatial and temporal resolution the precision of the measurements and the usefulness of the data the presented analysis is focused on dinsar results exploitation of various ground subsidence phenomena groundwater withdrawal soil compaction mining subsidence evaporite dissolution subsidence and volcanic deformation with different displacement patterns in a selection of subsidence areas in spain finally a cost comparative study is performed for the different techniques applied

sea ice and polar climate in the ncar csm the climate system model csm consists of atmosphere ocean land and sea ice components linked by a flux coupler which computes fluxes of energy and momentum between components the sea ice component consists of a thermodynamic formulation for ice snow and leads within the ice pack and ice dynamics using the cavitating fluid ice rheology which allows for the compressive strength of ice but ignores shear viscosity the results of a 300 yr climate simulation are presented with the focus on sea ice and the atmospheric forcing over sea ice in the polar regions the atmospheric model results are compared to analyses from the european centre for medium range weather forecasts and other observational sources the sea ice concentrations and velocities are compared to satellite observational data the atmospheric sea level pressure slp in csm exhibits a high in the central arctic displaced poleward from the observed beaufort high the southern hemisphere slp over sea ice is generally 5 mb lower than observed air temperatures over sea ice in both hemispheres exhibit cold biases of 2 4 k the precipitationminus evaporation fields in both hemispheres are greatly improved over those from earlier versions of the atmospheric gcm the simulated ice covered area is close to observations in the southern hemisphere but too large in the northern hemisphere the ice concentration fields show that the ice cover is too extensive in the north pacific and subarctic north atlantic oceans the interannual variability of the ice area is similar to observations in both hemispheres the ice thickness pattern in the antarctic is realistic but generally too thin away from the continent the maximum thickness in the arctic occurs against the bering strait not against the canadian archipelago as observed the ice velocities are stronger than observed in both hemispheres with a consistently greater turning angle to the left in the southern hemisphere they produce a northward ice transport in the southern hemisphere that is 3 4 times the satellite derived value sensitivity tests with the sea ice component show that both the pattern of wind forcing in csm and the air ice drag parameter used contribute to the biases in thickness drift speeds and transport plans for further development of the ice model to incorporate a viscousplastic ice rheology are presented in spite of the biases of the sea ice simulation the 300 yr climate simulation exhibits only a small degree of drift in the surface climate without the use of flux adjustment this suggests a robust stability in the simulated climate in the presence of significant variability

multiband psinsar and long period monitoring of land subsidence in a strategic detrital aquifer vega de granada se spain an approach to support management decisions abstract this work integrates detailed geological and hydrogeological information with psi data to obtain a better understanding of subsidence processes detected in the detrital aquifer of the vega de granada se spain during the past 13 years ground motion was monitored by exploiting sar images from the envisat 2003 2009 cosmo skymed 2011 2014 and sentinel 1a 2015 2016 satellites psinsar results show an inelastic deformation in the aquifer and small land surface displacements up to 55 mm the most widespread land subsidence is detected during the envisat period 2003 2009 which coincided with a long dry period in the region the highest displacement rates recorded during this period up to 10 mm yr were detected in the central part of the aquifer where many villages are located for this period there is a good correlation between groundwater level depletion and the augmentation of the average subsidence velocity and slight hydraulic head changes

sensitivity of sea ice to physical parameterizations in the giss global climate model 1 the giss coupled model is used to investigate the sensitivity of sea ice to each of the following parameterizations 1 two sea ice dynamics cf cavitating fluid vp viscous plastic 2 the specification of oceanic isopycnal mixing coefficients in the gent and mcwillams isopyncal mixing gm and 3 the wajsowicz viscosity diffusion wv the large scale sea ice properties are highly sensitive to sea ice dynamics with the inclusion of resistance to shear stress vp captures the major observed sea ice drift features and improves the simulations of sea ice concentrations thickness and export through fram strait relative to cf gm significantly improves the simulation of vertical temperature distributions in the southern ocean although it leads to a dramatic reduction of antarctic sea ice cover the reduced oceanic isopycnal mixing coefficients lead to arctic sea ice that tends to be less and thinner in almost the entire arctic except in the north pacific and labrador sea while antarctic sea ice that extends more equatorward throughout the circumpolar regions the responses of sea ice to wv show an enlargement and thickening of sea ice in the arctic within the ice packs around the antarctic and a reduction and thinning of sea ice in the northern weddell and ross seas on the basis of these experiments two composite experiments with the best parameterizations are investigated the atmospheric responses associated with sea ice changes are discussed while improvements are seen there are still many unrealistic aspects that will require further improvements to sea ice and ocean components

analysis of subsidence using terrasar x data murcia case study this study was partially funded by the spanish ministry of science and technology and eu feder projects tec 2008 06764 and cgl 2009 08457 and by the generalitat valenciana project acomp 2010 082 as well as by the spanish geological and mining institute igme with the collaboration of the regional government of murcia the terrasar x images were provided by dlr in the framework of the scientific project geo0389 ers and envisat data were provided by esa in the framework of the cat1 project 2494

on the improvement of sea ice models for climate simulations the sea ice model intercomparison project experiments with dynamic thermodynamic sea ice models indicate a strong dependence of the net freezing rate sea ice transport and variability on dynamic model parameters although current dynamic thermodynamic sea ice models show relatively good agreement with observations an optimization seems to be necessary especially for the parameterizations of dynamic processes presently only a few coupled climate models use dynamic thermodynamic sea ice models in order to promote by means of coordinated numerical experiments the development of an optimal sea ice model for climate research the sea ice ocean modelling panel of the arctic climate system study acsys a project of the world climate research programme has initiated the sea ice model intercomparison project simip the first results from this model hierarchy approach are presented

a quasi elastic aquifer deformational behavior madrid aquifer case study summary the purpose of this paper is to analyze the quasi elastic deformational behavior that has been induced by groundwater withdrawal of the tertiary detrital aquifer of madrid spain the spatial and temporal evolution of ground surface displacement was estimated by processing two datasets of radar satellite images sar using persistent scatterer interferometry psi the first sar dataset was acquired between april 1992 and november 2000 by ers 1 and ers 2 satellites and the second one by the envisat satellite between august 2002 and september 2010 the spatial distribution of psi measurements reveals that the magnitude of the displacement increases gradually towards the center of the well field area where approximately 80 mm of maximum cumulated displacement is registered the correlation analysis made between displacement and piezometric time series provides a correlation coefficient greater than 85 for all the wells the elastic and inelastic components of measured displacements were separated observing that the elastic component is on average more than 4 times the inelastic component for the studied period moreover the hysteresis loops on the stress strain plots indicate that the response is in the elastic range these results demonstrate the quasi elastic behavior of the aquifer during the aquifer recovery phase ground surface uplift almost recovers from the subsidence experienced during the preceding extraction phase taking into account this unique aquifer system a one dimensional elastic model was calibrated in the period 1997 2000 subsequently the model was used to predict the ground surface movements during the period 1992 2010 modeled displacements were validated with psi displacement measurements exhibiting an error of 13 on average related with the inelastic component of deformation occurring as a long term trend in low permeability fine grained units this result further demonstrates the quasi elastic deformational behavior of this unique aquifer system

the influence of shelf processes in delivering dissolved iron to the hnlc waters of the drake passage antarctica abstract dissolved trace element distributions near elephant island in the drake passage show extremely high levels of dissolved fe and mn in waters above the shelf the entrainment of this enriched shelf water by the fe poor antarctic circumpolar current acc as it passes through the shackleton gap delivers an estimated 2 8 106 mol yr 1 dissolved fe to the offshore waters of the drake passage the magnitude and spatial distribution of dissolved fe mn and al over the shelf are consistent with a diagenetically produced sedimentary source but are inconsistent with eolian or upwelling sources the systematics of the mn and fe concentrations suggest that there are two distinct sources of dissolved fe to the surface waters of this region the highest fe concentrations are associated with bransfield strait water which can be identified by its characteristic temperature and salinity t s properties both inside the bransfield strait and in the bransfield current outflow between elephant and clarence islands most of the shelf area is dominated by a second water type with t s properties that are typical of modified antarctic surface water which while also enriched has a lower fe mn ratio the predominantly linear relationships between the fe and mn concentrations at the stations in each of these water mass types suggest that the distribution of these elements is largely controlled by physical mixing processes and that biological removal of fe on the shelf while certainly occurring is limited perhaps as a result of rapid physical flushing processes and relatively slow biological growth rates the consequent export of large quantities of this shelf derived fe into the acc is likely responsible for the extensive regions of enhanced primary production seen in satellite imagery downstream of the drake passage

influence of present day and glacial surface conditions on the antarctic oscillation southern annular mode 1 based upon coupled climate simulations driven by present day and glacial boundary conditions we demonstrate that the internal variability associated with the pronounced south polar climate anomalies that characterized the glacial climate regime was largely confined to the winter season in particular the intensity and spatial structure of the antarctic oscillation southern annular mode is found to display a strong seasonal cycle in the summer season we demonstrate that this mode of internal climate variability is extremely robust in response to a change from modern to glacial conditions in that it seems not to depend upon the latitudinal position of the baroclinic zone nor on the strength of the mean atmospheric zonal circulation in winter however and under glacial conditions this mode is characterized by a significantly modified atmospheric circulation that differs dramatically in terms of its internal variability from that characteristic of modern conditions

quasi stationary waves in the southern hemisphere an examination of their simulation by the ncar climate system model with and without an interactive ocean abstract the three primary quasi stationary waves in the geopotential height field of the southern hemisphere as simulated by the national center for atmospheric research ncar climate system model csm1 and the community climate model version 3 ccm3 are examined and compared with the ncar national centers for environmental prediction reanalyses fourier analysis is used to decompose the geopotential heights into its zonal harmonic components both models are able to simulate the mean and zonal asymmetry of the geopotential heights however the csm1 simulates the interannual variability considerably better than the ccm3 the amplitude and phase of wave 1 are well simulated by the models particularly in the subantarctic region the models are also able to reproduce the interannual variation in phase and amplitude of wave 1 the success of the simulation is attributed to the models ability to simulate well the important features of the geopotential height and temperature distributions the models

what sets the mean transport through drake passage twelve experiments with two coarse resolutions of a global ocean model using a variety of surface forcings are analyzed to address the question of what sets the mean transport through drake passage seven of the experiments do not have an active sea ice model but the remaining five do previous theories have suggested that the drake passage transport is governed by the cape horn sverdrup transport or alternatively is proportional to the square root of the meridional ekman transport at the latitude of drake passage the results presented here do not support either of these theories the drake passage transport depends quite strongly on the isopycnal diffusivity parameter in the model and less strongly on the background vertical diffusivity and horizontal viscosity parameters however when the magnitudes of these parameters are fixed the results show a very strong correlation between drake passage transport and both the strength of the meridional ekman transport at the latitude of drake passage and the thermohaline circulation off the antarctic shelf the relationships are monotonic but not linear the best estimate is that the meridional ekman transport drives 100 sv of drake passage transport while the remaining 30 sv are driven by the global thermohaline circulation

decadal variability in high northern latitudes as simulated by an intermediate complexity climate model a 2500 year integration has been performed with a global coupled atmospheric sea ice ocean model of intermediate complexity with the main objective of studying the climate variability in polar regions on decadal time scales and longer the atmospheric component is the ecbilt model a spectral t21 three level quasi geostrophic model that includes a representation of horizontal and vertical beat transfers as well as of the hydrological cycle ecbilt is coupled to the clio model which consists of a primitive equation free surface ocean general circulation model and a dynamic thermodynamic sea ice model comparison of model results with observations shows that the ecbilt clio model is able to reproduce reasonably well the climate of the high northern latitudes the dominant mode of coupled variability between the atmospheric circulation and sea ice cover in the simulation consists of an annular mode for geopotential height at 800 hpa and of a dipole between the barents and labrador seas for the sea ice concentration which are similar to observed patterns of variability in addition the simulation displays strong decadal variability in the sea ice volume with a significant peak at about 18 years positive volume anomalies are caused by 1 a decrease in ice export through fram strait associated with more anticyclonic winds at high latitudes 2 modifications in the freezing melting rates in the arctic due to lower air temperature and higher surface albedo and 3 a weaker heat flux at the ice base in the barents and kara seas caused by a lower inflow of warm atlantic water opposite anomalies occur during the volume decrease phase of the oscillation

recent and present day stresses in the granada basin betic cordilleras example of a late miocene present day extensional basin in a convergent plate boundary the diffuse convergent boundary between the eurasian and african plates in the western mediterranean is associated with a seismicity zone more than 300 km wide although the two plates are converging nw se the betic and rif cordilleras contain extensional structures that have been active since the miocene the extensional tectonics in the region which occurred simultaneously with the uplift of the cordillera have been analyzed in the southeastern sector of the late miocene to recent granada basin using earthquake focal mechanisms the determination of paleostresses from the study of the orientation and kinematics of microfaults and the study of the major structures both the geological surface data and the focal mechanisms indicate present day regional conditions of ne sw extension with triaxial to prolate stress ellipsoids however the stress field is heterogeneous with local variations in stress over time with different stresses sometimes even acting simultaneously in adjacent areas the most frequent changes consist of pluridirectional or ne sw extension favored by the prolate character of the stress ellipsoids and nw se subhorizontal compression favored by the regional tectonic setting strike slip faults are scarce even though they are the most likely structure to be expected in a region with sw ne extension and nw se compression seismicity is concentrated in the upper crust and may correspond to the activity of low to high angle normal faults similar to the surface faults although they can not be correlated with them the lower cutoff of this seismicity probably coincides with the 300 c isotherm and suggests a low thermal gradient for the region present day regional stresses have 1 vertical at the surface but in depth plunge toward the sw

the atmospheric response to realistic arctic sea ice anomalies in an agcm during winter abstract the influence of realistic arctic sea ice anomalies on the atmosphere during winter is investigated with version 3 6 of the community climate model ccm3 6 model experiments are performed for the winters with the most 1982 83 and least 1995 96 arctic ice coverage during 1979 99 when ice concentration estimates were available from satellites the experiments consist of 50 member ensembles using large ensembles proved critical to distinguish the signal from noise the local response to ice anomalies over the subpolar seas of both the atlantic and pacific is robust and generally shallow with large upward surface heat fluxes 100 w m 2 near surface warming enhanced precipitation and below normal sea level pressure where sea ice receded and the reverse where the ice expanded the large scale response to reduced enhanced ice extent to the east west of greenland during 1982 83 resembles the negative phase of the arctic oscillation north atlantic oscillation ao nao with a ridge over t

atmospheric circulation and its effect on arctic sea ice in ccsm3 simulations at medium and high resolution the simulation of arctic sea ice and surface winds changes significantly when community climate system model version 3 ccsm3 resolution is increased from t42 2 8 to t85 1 4 at t42 resolution arctic sea ice is too thick off the siberian coast and too thin along the canadian coast both of these biases are reduced at t85 resolution the most prominent surface wind difference is the erroneous north polar summer anticyclone present at t42 but absent at t85 an offline sea ice model is used to study the effect of the surface winds on sea ice thickness in this model the surface wind stress is prescribed alternately from reanalysis and the t42 and t85 simulations in the offline model ccsm3 surface wind biases have a dramatic effect on sea ice distribution with reanalysis surface winds annual mean ice thickness is greatest along the canadian coast but with ccsm3 winds thickness is greater on the siberian side a significant difference between the two ccsm3 forced offline simulations is the thickness of the ice along the canadian archipelago where the t85 winds produce thicker ice than their t42 counterparts seasonal forcing experiments with ccsm3 winds during spring and summer and reanalysis winds in fall and winter relate the canadian thickness difference to spring and summer surface wind differences these experiments also show that the ice buildup on the siberian coast at both resolutions is related to the fall and winter surface winds the arctic atmospheric circulation is examined further through comparisons of the winter sea level pressure slp and eddy geopotential height at both resolutions the simulated beaufort high is quite weak weaker at higher resolution eddy heights show that the wintertime beaufort high in reanalysis has a barotropic vertical structure in contrast high ccsm3 slp in arctic winter is found in association with cold lower tropospheric temperatures and a baroclinic vertical structure in reanalysis the summertime arctic surface circulation is dominated by a polar cyclone which is accompanied by surface inflow and a deep ferrel cell north of the traditional polar cell the arctic ferrel cell is accompanied by a northward flux of zonal momentum and a polar lobe of the zonal mean jet these features do not appear in the ccsm3 simulations at either resolution

evaluation of coupled ocean atmosphere simulations of the mid holocene using palaeovegetation data from the northern hemisphere extratropics we have used the biome4 biogeography biochemistry model and comparison with palaeovegetation data to evaluate the response of six ocean atmosphere general circulation models to mid holocene changes in orbital forcing in the mid to high latitudes of the northern hemisphere all the models produce a a northward shift of the northern limit of boreal forest in response to simulated summer warming in high latitudes the northward shift is markedly asymmetric with larger shifts in eurasia than in north america b an expansion of xerophytic vegetation in mid continental north america and eurasia in response to increased temperatures during the growing season c a northward expansion of temperate forests in eastern north america in response to simulated winter warming the northward shift of the northern limit of boreal forest and the northward expansion of temperate forests in north america are supported by palaeovegetation data the expansion of xerophytic vegetation in mid continental north america is consistent with palaeodata although the extent may be over estimated the simulated expansion of xerophytic vegetation in eurasia is not supported by the data analysis of an asynchronous coupling of one model to an equilibrium vegetation model suggests vegetation feedback exacerbates this mid continental drying and produces conditions more unlike the observations not all features of the simulations are robust some models produce winter warming over europe while others produce winter cooling as a result some models show a northward shift of temperate forests consistent with though less marked than the expansion shown by data and others produce a reduction in temperate forests elucidation of the cause of such differences is a focus of the current phase of the palaeoclimate modelling intercomparison project

deciphering the role of southern gateways and carbon dioxide on the onset of the antarctic circumpolar current 1 growth of antarctic ice sheet during the cenozoic 34 million years ago appears as a potential tipping point in the long term cooling trend that began 50 ma ago for decades the onset of the antarctic circumpolar current acc following the opening of the drake passage and of the tasman seaway has been suggested as the main driver of the continental scale antarctic glaciation however recent modeling works emphasized that the eocene oligocene atmospheric carbon dioxide co2 lowering could be the primary forcing of the antarctic glaciation questioning the acc theory here we investigate the response of the acc to changes in co2concentrations occurring from the late eocene to the late oligocene we used a fully coupled atmosphere ocean model foam with a mid oligocene geography we find that the opening of southern oceanic gateways does not trigger the onset of the acc for co2typical of the late eocene 840 ppm a cooler background climatic state such as the one prevalent at the end of the oligocene is required to simulate a well developed acc in this cold configuration the intensified sea ice development around antarctica and the resulting brine formation lead to a strong latitudinal density gradient in the southern ocean favoring the compensation of the ekman transport and consequently the acc our results imply that the acc has acted as a feedback rather than as a driver of the global cooling

satellite derived maps of arctic and antarctic sea ice motion 1988 to 1994 standard image processing methods applied to 85 5 ghz special sensor microwave imager ssm i data provide previously unseen details about sea ice motion in the arctic and southern oceans means calculated from daily ice motions for 1988 1994 confirm the basic circulation patterns established from drifting stations and buoys but extend these observations to illustrate less well known transport patterns in the arctic coastal zones and sub arctic seas in the antarctic the gridded motion fields show a nearly continuous westward transport along the antarctic coast with well defined regions of exchange between this east wind drift and the antarctic circumpolar current this detailed view of mean ice motion in the southern ocean is unique and presents a comprehensive overview not previously available for antarctic ice motions

land subsidence due to groundwater withdrawal in the northern beijing plain china abstract beijing is an international metropolis where over exploration of water resource makes land subsidence becoming more and more serious the related problems cannot be avoided in the coming years because of the giant increase of population the aims of this study are to quantify land subsidence over the period 2003 to 2010 grasp the evolution of the process and investigate the relation with the triggering factors in the northern area of the beijing plain various data including deep compaction from vertical multiple borehole extensometers land subsidence from persistent scatterer interferometry and leveling surveys groundwater levels hydrogeological setting from wellbores and landsat tm image were collected and effectively used to detect the spatial and temporal features of land subsidence and its possible relation with groundwater level changes compressible layer thickness and urban development results show that land subsidence is unevenly distributed and continuously increased from 2003 to 2010 the average loss of elevation over the monitoring period amounted to 92 5 mm with rates up to 52 mm y the distribution of the subsidence bowl is only partially consistent with that of the groundwater depression cone because of the variable thickness of the most compressible fine deposits in fact extensometers reveal that silty clay layers account for the larger contribution to land subsidence with the 15 m thick silty clay layer between 102 and 117 m depth accounting for about 25 of the total subsidence finally no clear correlation has been observed between the subsidence rates and the increase of the load on the land surface connected to the impressive urban development this study represents a first step toward the development of a physically based model of the subsidence occurrence to be used for planning remediation strategies in the northern beijing plain

a simulation of the last glacial maximum climate using the ncar ccsm the national center for atmospheric research community climate system model ncar ccsm is used in a coupled atmosphere ocean sea ice simulation of the last glacial maximum lgm around 21 000 years ago climate in the tropics the simulation shows a moderate cooling of 3 c over land and 2 c in the ocean in zonal average this cooling is about 1 c cooler than the climap sea surface temperatures ssts but consistent with recent estimates of both land and sea surface temperature changes subtropical waters are cooled by 2 2 5 c also in agreement with recent estimates the simulated oceanic thermohaline circulation at the lgm is not only shallower but also weaker than the modern with a migration of deep water formation site in the north atlantic as suggested by the paleoceanographic evidences the simulated northward flow of antarctic bottom water aabw is enhanced these deep circulation changes are attributable to the increased surface density flux in the southern ocean caused by sea ice expansion at the lgm both the gulf stream and the kuroshio are intensified due to the overall increase of wind stress over the subtropical oceans the intensified zonal wind stress and southward shift of its maximum in the southern ocean effectively enhances the transport of the antarctic circumpolar current acc by more than 50 simulated ssts are lowered by up to 8 c in the midlatitudes simulated conditions in the north atlantic are warmer and with less sea ice than indicated by climap again in agreement with more recent estimates the increased meridional sst gradient at the lgm results in an enhanced hadley circulation and increased midlatitude storm track precipitation the increased baroclinic storm activity also intensifies the meridional atmospheric heat transport a sensitivity experiment shows that about half of the simulated tropical cooling at the lgm originates from reduced atmospheric concentrations of greenhouse gases

last glacial maximum in south america paleoclimate proxies and model results 1 observations in south america based on paleoenvironmental data for the last glacial maximum lgm that shows a generally lower temperatures and reduced precipitation of the region are compared to simulation results from the paleoclimate version of the national center for atmospheric research coupled climate system model analyses of the lgm wind simulation for the tropical atlantic show that the convergence zone does not extend all the way into south american continent during the austral summer this would have prevented moisture inflow into the adjacent continental area of equatorial northeastern brazil interpretations of paleoclimate proxy records from this region are consistent with this scenario in the subtropics lgm westerlies were weaker and data show characteristics of more humid conditions at higher latitudes model simulations suggest intensification of the westerlies which in combination with colder sea surface temperatures would imply less moisture influx into the south american continent from the atlantic sector low lake levels in high southern latitudes and general aridity would support the model findings

polar climate instability and climate teleconnections from the arctic to the midlatitudes and tropics abstract it is generally accepted that the ocean thermohaline circulation plays a key role in polar climate stability and rapid climate change recently reported analyses of the impact of anomalous freshwater outflows from the north american continent onto either the north atlantic or arctic oceans demonstrate that in either case a clear reduction in the atlantic meridional overturning circulation accompanied by an increase in sea ice extent is predicted the results also reconcile proxy inferred younger dryas greenland temperature variations the aim of the present work is to provide a detailed investigation of the pathways along which the signal associated with overturning circulation anomalies propagates into both the midlatitudes and the tropics and the effect such teleconnections have on the tropical ocean atmosphere system the authors consider both the impact of substantial slowing of the overturning circulation due to freshwater forcing of the north atlantic as well as its recovery after the a