large areas surface deformation analysis through a cloud computing p sbas approach for massive processing of dinsar time series abstract we present in this work a methodology for computing surface deformation time series and mean velocity maps of large areas our approach relies on the availability of a multi temporal set of synthetic aperture radar sar data collected from ascending and descending orbits over an area of interest and also permits us to estimate the vertical and horizontal east west components of the earth s surface deformation the adopted methodology is based on an advanced cloud computing implementation of the differential sar interferometry dinsar parallel small baseline subset p sbas processing chain which allows the unsupervised processing of large sar data volumes from the raw data level 0 imagery up to the generation of the corresponding dinsar time series and maps the solution presented which is highly scalable has been tested on ascending and descending envisat sar archives comprising approximately 400 gb of data which have been acquired over a large area of southern california us that extends over about 90 000 km 2 such an input dataset has been processed in parallel by exploiting 280 computing nodes of the amazon web services cloud environment the overall processing lasted about 8 h and cost approximately 1900 usd moreover to produce the final mean deformation velocity maps of the vertical and horizontal east west displacement components of the whole investigated area we also took advantage of the information available from external gps measurements that permit us to account for possible regional trends not easily detectable by dinsar and to refer the p sbas measurements to an external geodetic datum the results presented clearly demonstrate the effectiveness of the proposed approach that paves the way to the extensive use of the available ers 1 2 and envisat sar data archives furthermore the proposed methodology can be particularly suitable to deal with the very large data flow provided by the sentinel 1 constellation thus permitting the extension of the dinsar analyses at a nearly global scale

spatial and temporal deformation along the northern san jacinto fault southern california implications for slip rates the san timoteo badlands is an area of uplift and erosional dissection that has formed as a result of late quaternary uplift along a restraining bend in the san jacinto fault of the san andreas fault system in southern california this bend currently is located in a region where late quaternary deposits and associated surfaces have formed in lower san timoteo canyon we have used morphometric analysis of these surfaces in conjunction with computer modeling of deformational patterns along the san jacinto fault to reconstruct spatial and temporal variations in uplift along the bend morphometric techniques used include envelope subenvelope map ping a gradient length index along channels and denudation values age control is determined using a combination of thermoluminescence tl and near infrared op tical simulation luminescence dating irosl and correlation of soil development indices these approaches are combined with an elastic half space model used to determine the deformation associated with the fault bend the region of modeled uplift has a similar distribution as that determined by morphometric techniques luminescence dates and soil correlation age estimates generally agree based on soil development surfaces within the study area were stabilized at approximately 300 700 ka for q3 43 67 ka for q2 and 27 5 67 ka for q1 luminescence ages both tl and irosl for the formation of the younger two surfaces are 58 to 94 ka for q2 and 37 to 62 ka for q1 ages reported to 1r uncertainty periods of uplift were determined for the surfaces in the study area resulting in approximate uplift rates of 0 34 to 0 84 m ka for the past 100 ka and 0 13 to 1 00 m ka for the past 66 ka comparison of these rates of uplift to those generated by the model support a higher rate of lateral slip along the san jacinto fault than commonly assumed greater than 20 mm yr as compared to 8 12 mm yr commonly cited this higher slip rate supports the proposal that a greater amount of slip has transferred from the san andreas fault to the san jacinto fault than generally held the san jacinto fault may have accommodated a significant portion of the plate boundary slip during the past 100 ka

decorrelation in interferometric radar echoes a radar interferometric technique for topographic mapping of surfaces implemented utilizing a single synthetic aperture radar sar system in a nearly repeating orbit is discussed the authors characterize the various sources contributing to the echo correlation statistics and isolate the term which most closely describes surficial change they then examine the application of this approach to topographic mapping of vegetated surfaces which may be expected to possess varying backscatter over time it is found that there is decorrelation increasing with time but that digital terrain model generation remains feasible the authors present such a map of a forested area in oregon which also includes some nearly unvegetated lava flows such a technique could provide a global digital terrain map

national geohazards mapping in europe interferometric analysis of the netherlands abstract the launch of copernicus the largest earth observation program to date is significant due to the regular reliable and freely accessible data to support space based geodetic monitoring of physical phenomena that can result in natural hazards in this study wide area interferometric synthetic aperture radar insar capability is demonstrated by processing 435 copernicus sentinel 1 c band sar images may 2015 may 2017 using the intermittent small baseline subset isbas method to produce a wide area map wam covering 53 000 km2 of the netherlands belgium and germany the isbas wam contains over 19 million measurements achieving a ground coverage of 94 the retrieval of measurements over soft surfaces i e agricultural fields forests and wetlands was crucial due the dominance of non urban land cover a statistical analysis of the velocities reveals that intermittently coherent measurements in rural areas can provide reliable additional deformation information with a very high degree of confidence 5 which spatially correlates to known deformation features associated with compressible soils infrastructure settlement peat oxidation gas production salt mining and underground and opencast mining the spatial distribution of deformations concurs with independent data sources such as previous persistent scatterer interferometry psi deformation maps models of subsidence and settlement susceptibility and quantitatively with gps measurements over the groningen gas field remotely derived deformation products with near complete spatial coverage provide a powerful screening tool for mitigation and remediation of geological and geotechnical issues to help in the protection of assets property and life the isbas wam demonstrates that routine generation of such products on a continental scale is now theoretically achievable given the establishment of the copernicus programme and the development of state of the art insar methods such as isbas

a small baseline approach for investigating deformations on full resolution differential sar interferograms this paper presents a differential synthetic aperture radar sar interferometry difsar approach for investigating deformation phenomena on full resolution difsar interferograms in particular our algorithm extends the capability of the small baseline subset sbas technique that relies on small baseline difsar interferograms only and is mainly focused on investigating large scale deformations with spatial resolutions of about 100 spl times 100 m the proposed technique is implemented by using two different sets of data generated at low multilook data and full single look data spatial resolution respectively the former is used to identify and estimate via the conventional sbas technique large spatial scale deformation patterns topographic errors in the available digital elevation model and possible atmospheric phase artifacts the latter allows us to detect on the full resolution residual phase components structures highly coherent over time buildings rocks lava structures etc as well as their height and displacements in particular the estimation of the temporal evolution of these local deformations is easily implemented by applying the singular value decomposition technique the proposed algorithm has been tested with data acquired by the european remote sensing satellites relative to the campania area italy and validated by using geodetic measurements

fluxes of 230th and 231pa to the deep sea implications for the interpretation of excess 230th and 231pa 230th profiles in sediments abstract analysis of samples obtained with deep sea moored sediment traps deployed at 15 sites representing a wide range of oceanic conditions confirms that the flux of 230 th scavenged to the seafloor remains close to its production rate from the decay of 234 u in the overlying water column and generally validates the use of 230 th as a normalizing tool for paleoflux reconstruction after correction for trapping efficiency the flux of 230 th measured in the low flux regions amounts to 90 6 of the production rate with the notable exceptions of one site near the arabian sea upwelling and one site in the weddell sea a 230 th flux equivalent to 120 of the production rate was found in panama basin similar or more extensive scavenging of 230 th may be occurring at a pacific margin site off california and south of the polar front but these estimates are obscured by large errors on our trapping efficiency estimates in contrast the flux of 231 pa and the 231 pa 230 th ratio can vary strongly with particle flux following distinct trends in different oceanic basins in the atlantic ocean 231 pa fluxes and 231 pa 230 th are low and not sensitive to particle flux this is because of the short residence time of deep water in this basin resulting from thermohaline circulation which prevents the full development of lateral concentration gradients and full expression of boundary scavenging in the pacific ocean the sensitivity of 231 pa 230 th to particle flux is highest reflecting the longer residence time of deep water in the southern ocean 231 pa 230 th ratios are invariably high even when particle fluxes are low reflecting the predominance of opal which fractionates minimally between the two radionuclides interpretation of 231 pa 230 th recorded in sediments is thus complex in the atlantic this ratio is better suited for recording past changes in the strength of thermohaline circulation in the pacific it has the best potential for providing synoptic maps of past changes in particle flux in the southern ocean retrieval of information from 231 pa 230 th is more difficult and requires a more quantitative understanding of the influence of particle composition

molecular composition of dissolved organic matter in the mediterranean sea the molecular composition of marine dissolved organic matter dom is still poorly understood particularly in the mediterranean sea in this work dom from the open mediterranean sea and the adjacent northeast atlantic ocean was isolated by solid phase extraction spe dom and molecularly characterized using fourier transform ion cyclotron resonance mass spectrometry we assessed the gradual reworking of the spe dom transported by the shallow overturning circulation of the mediterranean sea by following the increase in molecular weight 20 da oxygenation 5 degradation index ideg 22 and the proportional decrease of unsaturated aliphatic compounds 34 along the levantine intermediate water this reworked spe dom that leaves the mediterranean sea through the strait of gibraltar strongly contrasts with the fresh material transported by the inflow of atlantic water ideg 25 in the deep eastern and western overturning cells the molecular composition of the deep waters varied according to their area and or time of formation spe dom of the waters formed in the aegean sea during the eastern mediterranean transient emt was more processed than the dom in pre emt waters formed in the adriatic sea molecular weight and the proportion of unsaturated aliphatic compounds were increased by 5 da and 9 respectively furthermore pre emt waters contain more reworked spe dom ideg 7 than post emt waters formed also in the adriatic sea in summary our study shows that the mediterranean sea constitutes a laboratory basin where degradation processes and diagenetic transformations of dom can be observed on close spatial and temporal scales

elucidating the dynamics and mixing agents of a shallow fjord through age tracer modelling abstract the mixing agents and their role in the dynamics of a shallow fjord are elucidated through an eulerian implementation of artificial tracers in a three dimensional hydrodynamic model the time scales of vertical mixing in this shallow estuary are short and the artificial tracers are utilized in order to reveal information not detectable in the temperature or salinity fields the fjord s response to external forcing is investigated through a series of model experiments in which we quantify vertical mixing transport time scales of fresh water runoff and estuarine circulation in relation to external forcing using age tracers released at surface and bottom we quantify the time scales of downward mixing of surface water and upward mixing of bottom water wind is shown to be the major agent for vertical mixing at nearly all depth levels in the fjord whereas the tide or external sea level forcing is a minor agent and only occasionally more important just close to the bottom the time scale of vertical mixing of surface water to the bottom or ventilation time scale of bottom water is estimated to be in the range 0 7 h to 9 0 days with an average age of 2 7 days for the year 2004 the fjord receives fresh water from two streams entering the innermost part of the fjord and the distribution and age of this water are studied using both ageing and conservative tracers the salinity variations outside this fjord are large and in contrast to the salinity the artificial tracers provide a straight forward analysis of river water content the ageing tracer is used to estimate transport time scales of river water i e the time elapsed since the water left the river mouth in may 2004 the typical age of river water leaving the fjord mouth is 5 days as the major vertical mixing agent is wind it controls the estuarine circulation and export of river water when the wind stress is set to zero the vertical mixing is reduced and the vertical salinity stratification is increased and the river water can be effectively exported out of the fjord we also analyse the river tracer fields and salinity field in relation to along estuary winds in order to detect signs of wind induced straining of the along estuary density gradient we find that events of down estuary winds are primarily associated with a reduced along estuary salinity gradient due to increased surface salinity in the innermost part of the fjord and with an overall decrease in vertical stratification and river water content at the surface thus our results show no apparent signs of wind induced straining in this shallow fjord but instead they indicate increased levels of vertical mixing or upwelling during down estuary wind events

molecular transformation and degradation of refractory dissolved organic matter in the atlantic and southern ocean more than 90 of the global ocean dissolved organic carbon doc is refractory has an average age of 4000 6000 years and a lifespan from months to millennia the fraction of dissolved organic matter dom that is resistant to degradation is a long term buffer in the global carbon cycle but its chemical composition structure and biochemical formation and degradation mechanisms are still unresolved we have compiled the most comprehensive molecular dataset of 197 fourier transform ion cyclotron resonance mass spectrometry ft icr ms analyses from solid phase extracted marine dom covering two major oceans the atlantic sector of the southern ocean and the east atlantic ocean ranging from 50 n to 70 s molecular trends and radiocarbon dating of 34 dom samples comprising 14c values from 229 to 495 were combined to model an integrated degradation rate for bulk doc resulting in a predicted age of 24 ka for the most persistent dom fraction first order kinetic degradation rates for 1557 mass peaks indicate that numerous dom molecules cycle on timescales much longer than the turnover of the bulk doc pool estimated residence times of up to 100 ka and the range of validity of radiocarbon dating changes in elemental composition were determined by assigning molecular formulae to the detected mass peaks the combination of residence times with molecular information enabled modelling of the average elemental composition of the slowest degrading fraction of the dom pool in our dataset a group of 361 molecular formulae represented the most stable composition in the oceanic environment island of stability these most persistent compounds encompass only a narrow range of the molecular elemental ratios h c average of 1 17 0 13 and o c average of 0 52 0 10 and molecular masses 360 28 and 497 51 da in the weddell sea doc concentrations in the surface waters were low 46 3 3 3 m while the organic radiocarbon was significantly more depleted than that of the east atlantic representing average surface water dom ages of 4920 180 a these results are in accordance with a highly degraded dom in the weddell sea surface water as also shown by the molecular degradation index ideg obtained from ft icr ms data further we identified 339 molecular formulae which probably contribute to an increased doc concentration in the southern ocean and potentially reflect an accumulation or enhanced sequestration of refractory doc in the weddell sea these results will contribute to a better understanding of the persistent nature of marine dom and its role as an oceanic carbon buffer in a changing climate

similar rates of modern and last glacial ocean thermohaline circulation inferred from radiochemical data today the ocean thermohaline circulation transports half of the 231pa produced by radioactive decay in the atlantic ocean water column to the southern ocean this export respectively imparts low and high 231pa 230th ratios to the surface sediments of these oceans ocean sediments from the last glacial maximum bear a similar isotopic fingerprint implying that advection of north atlantic deep intermediate water into the circumpolar deep water of the southern ocean occurred at a similar or slightly higher rate during the last glacial period

on the late pleistocene ocean geochemistry and circulation a box model of the atmosphere and ocean was developed to investigate how geochemical distributions extant during the late pleistocene may have come about the model simulates the regional distribution of calcium carbonate dissolution as well as the chemical oceanography and atmospheric co2 13c and radiocarbon if the downward biological flux of particulate carbon increases by a factor of 2 to 3 in the antarctic and if this increase is combined with a relative increase of the atlantic sector antarctic bottom water aabw versus north atlantic deep water nadw source ratio from 1 3 to about 2 1 then the model predicts several changes that seem to be recorded in the sedimentary record as follows 1 a global redistribution of nutrients and 12c from the intermediate to deep water takes place with the atlantic intermediate water phosphate decreasing 0 6 mole kg 1 and the 13c increasing 0 3 to 0 5 2 the dissolved oxygen level of the deep sea is reduced from an average of about 180 to 70 mole kg 1 but the intermediate water oxygen declines only a small amount 3 the decrease in intermediate water nutrient concentration results in lower average organic carbon and calcium carbonate production in the warm surface ocean 4 the atmospheric co2 decreases by 90 to 110 ppm 5 initially a global increase in calcium carbonate dissolution occurs which is followed by a relaxation toward better preservation than exists for the present ocean in the model in this paper the reduction of nadw by itself does not produce these effects rather the nutrient decrease that does occur is found mostly in north pacific intermediate water and the model atmospheric co2 decrease is only 10 to 30 ppm it is observed that 92 of the atmospheric co2 change takes place according to a 200 year time constant in the model this corresponds to the response time of the upper ocean and atmosphere to a change in the stationary state atmospheric pco2 thus according to this model the time lag between the nutrient based cause and the atmospheric co2 response is not expected to be particularly large

the displacement field of the landers earthquake mapped by radar interferometry geodetic data obtained by ground or space based techniques can be used to infer the distribution of slip on a fault that has ruptured in an earthquake although most geodetic techniques require a surveyed network to be in place before the earthquake1 3 satellite images when collected at regular intervals can capture co seismic displacements without advance knowledge of the earthquake s location synthetic aperture radar sar interferometry first introduced4 in 1974 for topographic mapping5 8 can also be used to detect changes in the ground surface by removing the signal from the topography9 10 here we use sar interferometry to capture the movements produced by the 1992 earthquake in landers california11 we construct an interferogram by combining topographic information with sar images obtained by the ers 1 satellite before and after the earthquake the observed changes in range from the ground surface to the satellite agree well with the slip measured in the field with the displacements measured by surveying and with the results of an elastic dislocation model as a geodetic tool the sar interferogram provides a denser spatial sampling 100 m per pixel than surveying methods1 3 and a better precision 3 cm than previous space imaging techniques12 13

the mean age of ocean waters inferred from radiocarbon observations sensitivity to surface sources and accounting for mixing histories a number of previous observational studies have found that the waters of the deep pacific ocean have an age or elapsed time since contact with the surface of 700 1000 yr numerical models suggest ages twice as old here the authors present an inverse framework to determine the mean age and its upper and lower bounds givenglobaloceandataanalysisproject glodap radiocarbonobservations andthey show that the potential range of ages increases with the number of constituents or sources that are included in the analysis the inversion requires decomposing the world ocean into source waters which is obtained here using the total matrix intercomparison tmi method at up to 2 83 28 horizontal resolution with 11 113 surface sources the authors find that the north pacific at 2500 m depth can be no younger than 1100 yr old which is older than some previous observational estimates accounting for the broadness of surface regions where waters originate leads to a reservoir age correction of almost 100 yr smaller than would be estimated with a two or three water mass decomposition and explains some of the discrepancy with previous observational studies a best estimate of mean age is also presented using the mixing history along circulation pathways subject to the caveats that inference of the mixing history would benefit from further observations and that radiocarbon cannot rule out the presence of extremely old waters from exotic sources the deep north pacific waters are 1200 1500 yr old which is more in line with existing numerical model results

deflation of mount etna monitored by spaceborne radar interferometry ground based measurements of volcano deformation can be used to assess eruptive hazard but require the costly and often hazardous installation and maintenance of an instrument network here we show that spaceborne radar interferometry which has already shown its utility in mapping earthquake related deformation1 can be used to monitor long term volcano deformation two families of synthetic aperture radar images acquired from ascending and descending orbits by the satellite ers 1 and looking at mount etna from opposite sides cover the time period from 17 may 1992 to 24 october 1993 and include the second half of etna s most recent eruption despite artefacts of the interferometric technique we can observe a volcano wide deflation which is an expected consequence of the eruption but which had not previously been appreciated we quantify it using a simple model based on the change of pressure in a sphere located in an elastic half space the modelled deformation increases linearly with time until the end of the eruption our results show that it will be possible to use this technique to detect the inflation of volcanic edifices that usually precedes eruptions

the effects of thermohaline circulation on wind driven circulation in the south china sea abstractthe dynamic influence of thermohaline circulation on wind driven circulation in the south china sea scs is studied using a simple reduced gravity model in which the upwelling driven by mixing in the abyssal ocean is treated in terms of an upward pumping distributed at the base of the upper layer because of the strong upwelling of deep water the cyclonic gyre in the northern scs is weakened but the anticyclonic gyre in the southern scs is intensified in summer while cyclonic gyres in both the southern and northern scs are weakened in winter for all seasons the dynamic influence of thermohaline circulation on wind driven circulation is larger in the northern scs than in the southern scs analysis suggests that the upwelling associated with the thermohaline circulation in the deep ocean plays a crucial role in regulating the wind driven circulation in the upper ocean

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

abyssal water carbon 14 distribution and the age of the world oceans the carbon 14 distribution in the abyssal waters of the world oceans indicates replacement times for pacific indian and atlantic ocean deep waters more than 1500 meters deep of approximately 510 250 and 275 years respectively the deep waters of the entire world ocean are replaced on average every 500 years

what do benthic δ13c and δ18o data tell us about atlantic circulation during heinrich stadial 1 approximately synchronous with the onset of heinrich stadial 1 hs1 13c decreased throughout most of the upper 1000 2500 m atlantic and at some deeper north atlantic sites this early deglacial 13c decrease has been alternatively attributed to a reduced fraction of high 13c north atlantic deep water nadw or to a decrease in the nadw 13c source value here we present new benthic 18o and 13c records from three relatively shallow 1450 1650 m subpolar northeast atlantic cores with published data from other cores these data form a depth transect 1200 3900 m in the subpolar northeast atlantic we compare last glacial maximum lgm and hs1 data from this transect with data from a depth transect of cores from the brazil margin the largest lgm to hs1 decreases in both benthic 13c and 18o occurred in upper waters containing the highest nadw fraction during the lgm we show that the 13c decrease can be explained entirely by a lower nadw 13c source value entirely by a decrease in the proportion of nadw relative to southern ocean water or by a combination of these mechanisms however building on insights from model simulations we hypothesize that reduced ventilation due to a weakened but still active atlantic meridional overturning circulation also contributed to the low 13c values in the upper north atlantic we suggest that the benthic 18o gradients above 2300 m at both core transects indicate the depth to which heat and north atlantic deglacial freshwater had mixed into the subsurface ocean by early hs1

constraints on deep water formation from the oceanic distributions of 10be 1 an analysis of the oceanic distribution of cosmogenic 10be shows that deep waters are formed by descending of cold dense surface waters at a rate of 18 sv 106 m3 s 1 in the northern north atlantic and 21 sv of which 17 sv enters the pacific in the antarctic over the last mixing cycle of 800 years lending support to the estimates based on radiocarbon and nutrient distributions it also indicates that deep water production in the northern north atlantic is 50 higher averaging over the recent 100 years than over the last mixing cycle suggesting a possible increase in the thermohaline ventilation of the north atlantic during the past century

enhanced landslide investigations through advanced dinsar techniques the ivancich case study assisi italy abstract we extensively exploit advanced differential sar interferometry dinsar techniques for enhanced landslide investigations we focus on the ivancich area assisi central italy which is affected by a deep seated landslide investigated through in situ surveys for this area large data sets of sar acquisitions were collected by the c band ers 1 2 and envisat sensors from april 1992 to november 2010 and by the x band radars of the cosmo skymed csk constellation from december 2009 to february 2012 we concentrate on the advanced dinsar technique referred to as small baseline subset sbas approach benefiting of its capability to generate deformation time series at full spatial resolution and from multi sensor sar data this allows us to present one of the first examples for a landslide area of ers 1 2 envisat deformation time series exceeding 18 years the results allowed characterizing the long term behaviour of the landslide and identifying sectors of the unstable slope affected by different deformation dynamics analysis of the csk data set characterized by a reduced revisit time and improved spatial resolution resulted in a 15 time larger point density with respect to the ers envisat measurements allowing to investigate nearly all the buildings and in many cases portions of buildings in the landslide area lastly we present an innovative modelling approach based on the effective integration of the dinsar measurements with traditional geological and geotechnical information providing deeper insights on the kinematical evolution of the landslide we consider our analysis a prototype example that can be extended to different geological and geotechnical conditions providing significant advances in the understanding of ground deformations induced by active landslides

biogeochemical cycling in the global ocean 1 a new analytical model with continuous vertical resolution and high latitude dynamics a new simple analytical model of ocean chemistry is presented which includes continuous vertical resolution high latitude dynamics air sea exchange and sea ice cover in this high latitude exchange interior diffusion advection hilda model ocean physics are represented by four parameters k and w an eddy diffusion coefficient and a deep upwelling velocity in the stratified interior q a rate of lateral exchange between the interior and a well mixed deep polar ocean and u an exchange velocity between surface and deep layers in the polar ocean first estimates are made of ice free and ice covered areas at high latitudes surface temperatures and air sea exchange velocities from available data then values of the physical parameters are estimated from simultaneous least mean square fits of model solutions for temperature t and abiotic carbon 14 14c to interior profiles of t and 14c and surface layer 14c values all derived from available data best fit values for k w q and u are 3 2 10 5 m2 s 1 2 0 10 8 m s 1 7 5 10 11 s 1 and 1 9 10 6 m s 1 respectively these results are interpreted in terms of modes of ocean circulation and mixing and compared with results from other simplier and more complex models in parts 2 and 3 of this series these values for k w q and u are taken as inputs for studying phosphorus oxygen and carbon cycling in the global ocean with the hilda model

milankovitch cycles in neocene deep sea sediment pelagic carbonate sediments from the world ocean basins commonly show cyclic variations in amount and or degree of preservation of biogenic calcite with periodicities of several tens to several hundreds of thousands of years the direct causes of these cycles are fluctuations in noncarbonate dilution carbonate production carbonate dissolution and or current winnowing the overall driving force however is variation in the earth s orbital characteristics milankovitch cycles through their influence on global climate and depositional processes the main inferred climatic effects of orbital perturbations are on global ice volume global temperature ocean circulation and distribution of climatic patterns eustatic sea level is directly related to ice volume as is the rate of erosion of clastic material from continental margins changes in volume of sea ice affect the volume and intensity of bottom water flow which in turn may cause changes in the intensity of sediment winnowing by bottom currents in the intensity of upwelling of nutrient rich bottom waters and in the depth of carbonate dissolution change in productivity of calcareous plankton are difficult to prove as a cause of carbonate cycles but may have contributed to the formation of carbonate cycles off northwest and southwest africa fluctuations in winnowing of fine grained components have been demonstrated as a cause of cyclic variations in the coarse fraction component of carbonate sediments in the southwest pacific dilution of carbonate by clastic material probably was a major cause of fluctuations in carbonate content of deep sea sediments off northwest and southwest africa carbonate dissolution cycles probably are the most common manifestation of fluctuations in bottom water flow dissolution cycles are common in quaternary and neogene sediments of the north atlantic caribbean and eastern equatorial pacific the main cause of the carbonate dissolution was shoaling of the carbonate compensation depth during the early neogene in response to climatically induced fluctuations in the thickness of antarctic bottom water

magnitude and geographic variation of the radiocarbon content in antarctic marine life implications for reservoir corrections in radiocarbon dating abstract radiocarbon age estimates on marine derined materials from the antarctic appear old in comparison with the terrestrial radiocarbon timescale as a result of significantly depleted 14 c concentrations in antarctic seas we review measurements of 14 c concentrations in modern antarctic marine life from south georgia the shetland islands and antarctic peninsula and suggest correction factors required to relate radiocarbon measurements on fossil marine materials from these areas to the conventional radiocarbon timescale for dates based on shells seaweeds sealbones and penguin bones the minimum correction factor for south georgia is ca 750 years and for the south shetland islands and antarctic peninsula it may be up to 1250 1300 years for whalebones a minimum correction of 1000 years may apply over a wide geographic area for comparison we also review radiocarbon measurements on marine species and seawater from other sectors of the antarctic in high latitudes correction factors of ca 1400 years are generally applicable to shell seal and penguin samples

synthetic aperture radar interferometry to measure earth s surface topography and its deformation synthetic aperture radar interferometry insar from earth orbiting spacecraft provides a new tool to map global topography and deformation of the earth s surface radar images taken from slightly different viewing directions allow the construction of digital elevation models of meter scale accuracy these data sets aid in the analysis and interpretation of tectonic and volcanic landscapes if the earth s surface deformed between two radar image acquisitions a map of the surface dis placement with tens of meters resolution and subcentimeter accuracy can be con structed this review gives a basic overview of insar for earth scientists and presents a selection of geologic applications that demonstrate the unique capabilities of insar for mapping the topography and deformation of the earth

cadmium in the north atlantic implication for global cadmium phosphorus relationship abstract dissolved cadmium cd distribution was determined in the tropical subtropical north atlantic along geotraces ga03 section us geotraces 2010 and 2011 cruises a pronounced mid depth cd maximum extends from the productive tropical eastern north atlantic where subsurface waters in the upper themocline are depleted in dissolved oxygen at this cd maximum cd depletion relative to phosphate po4 is observed in the cd vs po4 plot but the relative cd depletion is not present in the plot of cd po4 ratio vs depth the apparent relative cd depletion at the cd maximum appears to reflect a depth dependent variation of cd po4 ratio commonly observed in the world ocean such depth dependent variation of cd po4 ratio may result from the regeneration of cd from cd poor particulate organic carbon poc in the upper ocean and from cd rich poc in the deep ocean the vertical cd regeneration may lead to the observed difference in deep water cd po4 ratio between the north atlantic and north pacific if cd to phosphorus ratio in the poc flux to the deep ocean is higher in the pacific than in the atlantic

vegetation and climate changes during the last 22 000 yr from a marine core near taitao peninsula southern chile high temporal resolution of pollen analyses from marine core md07 3088 46 s documents regional and coastal vegetation changes in the mid latitude of southern chile during the last 22 kyr bp the coastal margin was partly ice free during the last glacial period with the presence of scattered vegetation after 17 6 kyr bp the expansion of nothofagus woodland highlights a warming trend and marks the beginning of the last deglaciation the deglacial forest expansion is interrupted by the development of magellanic moorland simultaneously with the antarctic cold reversal this vegetation change illustrates a pause in the warming trend with an abrupt increase in precipitation which is related to strong intensity of southern westerly winds after 12 8 kyr bp the retreat of magellanic moorland illustrates a second step warming that is strengthened after 11 5 kyr at the onset of the holocene expansion of heliophytic taxa illustrates warmest and driest conditions of the holocene from 11 to 7 4 kyr bp later the decrease of heliophytic taxa shows a return to cooler and wetter conditions illustrated by the presence of the north patagonian rainforest that reaches modern condition after 5 kyr climate changes inferred from the marine pollen record are consistent with geochemical data changes from the same samples and illustrate a clear synchronicity with d variations of epica dome c ice core during the last deglaciation and holocene comparison between vegetation changes from the marine core and regional palaeoclimatic records highlights southward northward shifts of the southern westerly wind belt and supports a close link between southern westerly wind belt and atmospheric co2 variability during the last deglaciation

surface displacement of the 17 may 1993 eureka valley california earthquake observed by sar interferometry satellite synthetic aperture radar sar interferometry shows that the magnitude 6 1 eureka valley earthquake of 17 may 1993 produced an elongated subsidence basin oriented north northwest parallel to the trend defined by the aftershock distribution whereas the source mechanism of the earthquake implies a north northeast striking normal fault the 3 millimeter accuracy of the radar observed displacement map over short spatial scales allowed identification of the main surface rupture associated with the event these observations suggest that the rupture began at depth and propagated diagonally upward and southward on a west dipping north northeast fault plane reactivating the largest escarpment in the saline range

satellite radar interferometry time series analysis of surface deformation for los angeles california 1 the los angeles california metropolitan area is a tectonically active region with surface deformation that is a combination of fault related tectonics plus a variety of natural and anthropogenic signals we apply the small baseline subset sbas algorithm to produce an interferometric synthetic aperture radar insar time series analysis for the los angeles area using data acquired by the ers satellites from late 1995 into 2002 the result is a space time deformation product that can be exploited to view not only the smoothly varying long term surface motion but also its time varying patterns large seasonal oscillations of the santa ana aquifer observed in southern california integrated gps network scign data are accurately matched in the insar time series moreover correlations of the insar time series with an annual sinusoid allows us to investigate the dynamics of the hydrologic system index terms 1243 geodesy and gravity space geodetic surveys 1294 geodesy and gravity instruments and techniques 1803 hydrology anthropogenic effects citation lanari r p lundgren m manzo and f casu 2004 satellite radar interferometry time series analysis of surface deformation for los angeles california geophys res lett 31 l23613 doi 10 1029 2004gl021294

the complete 3 d surface displacement field in the epicentral area of the 1999 mw7 1 hector mine earthquake california from space geodetic observations we use interferometric synthetic aperture radar insar data to derive continuous maps for three orthogonal components of the co seismic surface displacement field due to the 1999 m w7 1 hector mine earthquake in southern california vertical and horizontal displacements are both predominantly antisymmetric with respect to the fault plane consistent with predictions of linear elastic models of deformation for a strike slip fault some deviations from symmetry apparent in the surface displacement data may result from complexity in the fault geometry

river flow control on intertidal mudflat sedimentation in the mouth of a macrotidal estuary abstract the objective of this study is to analyze the impact of hydrological variability influenced by climatic phenomena upon the sedimentary exchange between the turbidity maximum tm and a river mouth intertidal mudflat this study carried out over a period of 10 years 1997 2006 in the seine estuary france is specifically focused on two extreme periods a wet one from 2001 to 2002 and a drier one from 2005 to 2006 this study is based on an original approach combining data gathered via low altitude remote sensing with altimeter readings and ground level measurements during this 10 year period we observed a link between climate change and the sedimentary processes on the mudflat surface the modifications of sedimentary processes are mainly connected to the multiannual variability of hydrological flow rates that control the positioning of the turbidity maximum the source of the sedimentary material deposited in this intertidal zone the tm at the mouth of the seine estuary is well developed its maximum mass is estimated to be between 300 000 tons and 500 000 tons avoine et al 1981 with maximum concentrations in the surface waters ranging from 1 to 2 g l 1 le hir et al 2001 most of the fine particles stored within the tm have been found to originate from within the catchment area dupont et al 1994 in the seine estuary the dynamics of the estuarine tm in response to hydrodynamic forcings have been previously described avoine et al 1981 and modeled e g brenon and le hir 1999 le hir et al 2001 the tm is upstream of the northern mudflat when the river flow is low

tracers and modeling the major tracer activity of the last four years was the completion in 1983 of a survey of the north and tropical atlantic begun in 1981 as part of the transient tracers in the ocean tto project brewer et al 1985 an early set of papers brewer et al 1983 and swift 1984 discussed evidence from these observations for the freshening of the north atlantic due to cessation of overflow across the iceland scotland ridge in the period between geosecs and tto broecker et al 1985a examined observations further south within the deep northeastern atlantic and showed that there was no change of nutrient contents in this region during the same time span consistent with their conclusion that there is no ventilation of this region from the north kawase and sarmiento 1985 and 1986 used the tto data to produce a series of nutrient and salinity maps and property property plots on density surfaces in the thermocline and middepth waters of particular interest in these studies is the evidence from silica salinity observations of strong cross isopycnal mixing and advection in the equatorial region

mining related ground deformation in crescent valley nevada implications for sparse gps networks 1 we use the small baseline subset sbas insar algorithm to obtain radar line of sight deformation velocities for two adjacent sar swaths and invert the data for the 2 d velocity field in vertical and ground range direction the analysis reveals areas of rapid deformation caused by mining and agricultural activities in the crescent valley nevada usa the los displacements of up to 25 centimeters during the 1992 2002 period are caused by vertical and horizontal deformation about 8 mm yr horizontal velocity is detected 10 km from the bargen gps site lewi suggesting that the gps station may be moving in response to the water pumping in the basin and range anthropogenic ground deformation can extend several tens of kilometers from the basins into the bedrock of the ranges

pre bomb radiocarbon and the reservoir correction for calcareous marine species in the southern ocean four antarctic marine mollusc shells which were collected alive between 1917 and 1940 were analyzed by accelerator mass spectrometry to provide the first pre bomb radiocarbon measurements of biogenic carbonates from the southern ocean after correcting for the impact of fossil fuel combustion suess effect radiocarbon activities of the pre bomb shells averaged 149 8 10 4 in contrast the 14c values for post bomb molluscs echinoderms brachiopods and foraminifera averaged 96 1 25 2 these biogenic carbonate 14c values are nearly identical to pre bomb estimates 148 to 152 and post bomb measurements 98 4 22 0 of the surface waters in the southern ocean average radiocarbon ages of the biogenic carbonates before and after 1950 1303 84 years and 811 205 years respectively along with those from seals and penguins indicate that the antarctic marine radiocarbon reservoir has decreased in age by nearly 500 years during the second half of the 20th century marine species and seawater measurements firmly place the radiocarbon reservoir correction at 1300 100 years for calcareous marine fossils which are widespread abundant and well preserved organic materials for interpreting ice sheet climate and sea level impacts on the antarctic marine ecosystem during the holocene

radiocarbon based circulation age of the world oceans 1 the distributions of deep ocean 14c data are often used to illustrate the rate of deep ocean circulation the associated conventional 14c ages show a difference of 1000 years between the north atlantic and the southern ocean and a difference of another 1000 years between the southern ocean and the north pacific these differences may be interpreted directly and mistakenly as the timescale of circulation the characterization of the deep ocean circulation being millennial is common using objectively gridded natural 14c data of key et al 2004 i recast 14c in terms of circulation by accounting for 1 long surface ocean reservoir 14c ages and 2 two sources of deep water formed in the north atlantic and around antarctica the new distribution of circulation 14c ages is more consistent with the deep ocean being characterized by a centennial timescale than a millennial timescale also the role of the southern sourced deep water is now made more obvious by accounting for the two important controls on oceanic 14c that are not well known outside the field of chemical oceanography the new map will be useful as an illustration of global deep ocean circulation to the wider scientific community and as a pedagogical tool to new students in earth sciences and oceanography

gravity and magma induced spreading of mount etna volcano revealed by satellite radar interferometry 1 mount etna underwent a cycle of eruptive activity over the past ten years here we compute ground displacement maps and deformation time series from more than 400 radar interferograms to reveal mount etna s average and time varying surface deformation from 1992 to 2001 we find that during this time interval it experienced magmatic inflation and radial spreading to the west south and east steady relative motion between the west and south flanks and between the east and north flanks during this time interval suggests they are related to gravitational spreading of the volcanic edifice time series analysis shows that growth of a southeastern basal anticline began with the end of magma recharge in 1995 thus showing a direct link between deep seated magma intrusions and edifice spreading these observations support a complex mode of radial gravitational collapse underlain by deeper magma driven basal spreading although ultimately the two must be related

deep upwelling and diffusivity in the southern central indian basin transport of the deepest water westward through a gap at 28 s in the ninetyeast ridge between the central indian basin and the west australia basin is calculated from hydrographic data collected as part of woce hydrographic program section i8n zero reference velocity levels at mid depth were chosen through consideration of water masses the small transport of 1 0 sv westward of water denser than 4 45 92 kg m 3 through the gap must all upwell in the southern central indian basin of this 0 7 sv upwells between the central and western sill sections that is close to the sill itself using the areas covered by the isopycnal we calculate an average vertical velocity of 3 3 10 3 cm s 1 close to the sill and of 4 2 10 4 cm s 1 west of the sill associated average vertical diffusivities are 105 cm s 1 close to the sill and 13 cm s 1 west of the sill in this bottom layer

radiocarbon profiles of the nw pacific from the lgm and deglaciation evaluating ventilation metrics and the effect of uncertain surface reservoir ages during the last deglaciation the ventilation of the subarctic pacific is hypothesized to have changed dramatically including the rejuvenation of a poorly ventilated abyssal water mass that filled the deep ocean and fluctuations in the strength of north pacific intermediate and deep water formation at millennial timescales foraminiferal radiocarbon reconstructions of past ventilation changes in the pacific are valuable but are hampered by poor carbonate preservation low sediment accumulation rates bias from bioturbation and poorly constrained past surface reservoir age in this study we present paired benthic planktonic radiocarbon measurements from the okhotsk sea and emperor seamounts we take advantage of large contemporaneous peaks in benthic abundances from the last glacial maximum bolling allerod ba and early holocene to produce time slices of radiocarbon from 1 to 4 km water depth we explore the impact of uncertain surface reservoir age and evaluate several approaches to quantifying past ocean radiocarbon distribution using our nw pacific data and a compilation of published data from the north pacific both the calendar age and the absolute value of an ocean radiocarbon estimate depend on the assumed surface reservoir age but for a time slice from a small geographical area with radiocarbon independent stratigraphic correlation between cores the shape of a water column profile is independent of surface reservoir age the nw pacific profiles are similar in shape to the compilation profiles for the entire north pacific which suggests that deglacial surface reservoir age changes across the n pacific did not diverge dramatically across the areas sampled the last glacial maximum lgm profile 2 km spans a wide range of values ranging from values similar to today to lower than today however by the ba the profile has a similar shape to today ultimately local surface reservoir ages end member water mass composition and mixing ratios must each be constrained before a radiocarbon activity reconstruction can be used to confidently infer ventilation changes

north atlantic deep water export to the southern ocean over the past 14 myr evidence from nd and pb isotopes in ferromanganese crusts the intensity of north atlantic deep water nadw production has been one of the most important parameters controlling the global thermohaline ocean circulation system and climate here we present a new approach to reconstruct the overall strength of nadw export from the north atlantic to the southern ocean over the past 14 myr applying the deep water nd and pb isotope composition as recorded by ferromanganese crusts and nodules we present the first long term nd and pb isotope time series for deep southern ocean water masses which are compared with previously published time series for nadw from the nw atlantic ocean these data suggest a continuous and strong export of nadw or a precursor of it into the southern ocean between 14 and 3 ma an increasing difference in nd and pb isotope compositions between the nw atlantic and the southern ocean over the past 3 myr gives evidence for a progressive overall reduction of nadw export since the onset of northern hemisphere glaciation nhg the nd isotope data allow us to assess at least semiquantitatively that the amount of this reduction has been in the range between 14 and 37 depending on location

southern ocean winter mixed layer austral winter 1986 observations from the polarstern along the greenwich meridian from the ice edge to the antarctic margin show the mixed layer beneath the winter sea ice cover to be significantly depressed in oxygen saturation incorporation of weddell deep water wdw into the winter mixed layer responsible for this undersaturation also introduces heat and salinity into the surface layer which strongly influences the mixed layer sea air exchanges and sea ice formation processes the total wdw transfer into the mixed layer averages 45 myr 1 implying a residence time for the surface water of 2 5 years the associated winter heat flux is 41 w m 2 which limits ice thickness to about 0 55 m agreeing quite well with observations the air temperatures during the cruise are just sufficient to remove the wdw heat input in the presence of observed ice thickness and concentration this suggests that the sea ice cover and wdw heat input into the mixed layer are in approximate balance by midwinter the annual heat flux from wdw to the surface layer and hence into the atmosphere is estimated as 16 w m 2 extrapolation of the greenwich meridian wdw entrainment value to the full circumpolar 60 70 s belt yields total up welling of 24 106 m3 s 1 similar extrapolation of the heat flux value gives a circumpolar total of 2 8 1014 w as a consequence of circulation topography interaction the maud rise water column stands out as an anomaly relative to the surrounding region with a significantly more saline and dense mixed layer below the mixed layer the water column over the crest of the rise is identical to that over the flanks if the latter water column is upwelled by 400 m this uplifting is believed to be a response of the upstream flow encountering the rise increased upstream flow would be expected to increase maud rise upwelling and the dependent salinity density of the mixed layer slight increases in the mixed layer density could trigger a convective mode and generation of a polynya it is hypothesized that spin up of the weddell gyre s barotropic circulation induced by an increase of the regional wind stress curl would enhance the probability of polynya development over maud rise

deformation and seismicity in the coso geothermal area inyo county california observations and modeling using satellite radar interferometry interferometric synthetic aperture radar insar data collected in the coso geothermal area eastern california during 1993 1999 indicate ground subsidence over a 50 km 2 region that approximately coincides with the production area of the coso geothermal plant the maximum subsidence rate in the peak of the anomaly is 3 5 cm yr 1 and the average volumetric rate of subsidence is of the order of 10 6 m 3 yr 1 the radar interferograms reveal a complex deformation pattern with at least two irregular subsidence peaks in the northern part of the anomaly and a region of relative uplift on the south we invert the insar displacement data for the positions geometry and relative strengths of the deformation sources at depth using a nonlinear least squares minimization algorithm we use elastic solutions for a prolate uniformly pressurized spheroidal cavity in a semi infinite body as basis functions for our inversions source depths inferred from our simulations range from 1 to 3 km which corresponds to the production depths of the coso geothermal plant underpressures in the geothermal reservoir inferred from the inversion are of the order of 0 1 1 mpa except a few abnormally high underpressures that are apparently biased toward the small source dimensions analysis of the insar data covering consecutive time intervals indicates that the depths and or horizontal extent of the deformation sources may increase with time this increase presumably reflects increasing volumes of the subsurface reservoir affected by the geothermal exploitation we show that clusters of microearthquakes associated with the geothermal power operation may result from perturbations in the pore fluid pressure as well as normal and shear stresses caused by the deflation of the geothermal reservoir

problems with using radiocarbon to infer ocean ventilation rates for past and present climates the oceanic c 14 distribution reflects mainly the circulation pattern and intensity but is also sensitive to the exchange processes at the air sea interface in order to separate the relative contributions of both effects that might have changed in the past we incorporate in an ocean general circulation model two passive tracers namely the normalized radiocarbon ratio delta 14 c and the actual age of water we quantify for both present and glacial conditions the decoupling between the c 14 ventilation rate and the circulation intensity as the difference between the simulated c 14 age and actual age of water the c 14 age of the model antarctic bottom water abbw appears systematically older than its actual age the discrepancy being larger for glacial conditions because of the more extensive antarctic sea ice cover our results suggest that the aabw flow rate could have been stronger than today during the last glacial maximum contrary to what might be inferred from a naive interpretation of c 14 measurements in deep sea sediment cores c 1999 elsevier science b v all rights reserved

a chlorofluoromethane and hydrographic section across drake passage deep water ventilation and meridional property transport new hydrographic and nutrient data obtained on a section across drake passage f s meteor january 1990 world ocean circulation experiment hydrographic program section s1 are in close agreement with property sections reported previously the chlorofluoromethanes cfm 11 and cfm 12 were measured in drake passage for the first time cfm concentrations are found to decrease from the surface down into the upper circumpolar deep water for which they confirm water renewal from the south for the lower circumpolar deep water in which cfm concentrations were above detection limit only south of the polar front very little water renewal on the cfm time scale is implied nonvanishing cfm is again found in the weddell sea deep water and the southeast pacific deep water toward the bottom in the south but recent ventilation for the latter water mass is rejected cfm 11 and cfm 12 concentrations vary essentially in constant proportion down to very low concentrations questioning the possibility of using cfm ratios as age markers the observed ratios are shown to be a natural feature of the upwelling regime of the southern ocean property concentrations on isopycnal surfaces display large undulations reaching down into the upper circumpolar deep water their extrema due to varying contribution of young water of southern origin are situated at the boundaries of the current bands of the antarctic circumpolar current the feature is ascribed to property advection by rings and is taken to support previous claims that rings are an important transport mechanism across the antarctic circumpolar current and that they might assist in maintaining its fronts