geoforschungszentrum anomaly magnetic map gamma a candidate model for the world digital magnetic anomaly map the world digital magnetic anomaly map wdmam is an ongoing effort toward the mapping of worldwide available aeromagnetic data it is led by a task force of the international association for geomagnetism and aeronomy iaga and aims at distributing a global map in printed and digital forms in this paper we describe in detail our candidate model which has to be evaluated by the iaga task force together with five other candidate maps after discussing the quality of the available data we show a simple but effective method applied to successfully process reduce and merge together individual compilations the near surface data are corrected using global field models and further refined with two dimensional polynomial corrections after the upward continuation to 5 km altitude data are resampled to a 3 minute grid and merged together we then calculate a spherical harmonic model up to degree 199 and analyze the magnetic spectrum of the global map this helps us to confirm that wavelengths larger than 400 km are spurious at a global scale in aeromagnetic compilations therefore we substitute them using a satellite based lithospheric field model mf5 to degree 100 finally our proposed candidate map for wdmam is presented

curie point depths in northeast china and their geothermal implications for the songliao basin abstract this work integrates processing and interpretation of the combined geomagnetic anomaly model of ngdc 720 v3 1 to better constrain thermal structures of the northeast china lithosphere which shows intensive extension and active volcanism during the mesozoic and cenozoic numerical tests demonstrate that magnetic anomalies calculated at 20 km altitude can be used for accurate curie depth estimation averaged curie depths using a 3d fractal exponent of 3 0 vary from 13 2 0 to 33 4 1 km with a mean of 22 2 4 km in northeast china with temperature dependent thermal conductivity models constrained by incorporated surface heat flow and curie depths in different geological blocks the thermal lithospheric thicknesses are estimated mostly between 45 and 90 km based on 1d steady state thermal conduction equation beneath the songliao basin the moho temperatures are abnormally high ranging from ca 700 to 1000 c and the mantle contributes about 65 of the total surface heat flow the shallow curie points and thermal lithosphere asthenosphere boundary together with high moho temperatures and mantle heat flow support abnormally high geotherms in the songliao basin originated from hot upper mantle upwelling triggered likely by lithospheric delamination

statistical analysis of the oceanic magnetic anomaly data abstract the study of the statistical properties of ocean magnetic anomalies could be very important to obtain new understanding on plate tectonics especially about the past properties of the lithospheric oceanic plates here we analyse in terms of statistical distributions the ocean magnetic anomaly data at the global scale covering the crustal oceanic ages from the present to 180 ma our results show that the marine magnetic anomaly data follow the laplace statistical distribution this behaviour is observed at global scale and for any time interval within the last 180 ma in addition the statistical parameters of the laplace distribution are used to define some properties of the crustal oceanic magnetic field focusing our investigation on the cretaceous normal superchron finally we also provide a physical explanation of this statistical distribution of marine magnetic anomaly data using a test with synthetic data

crustal magnetic anomaly in the ordos region and its tectonic implications abstract in this paper the ngdc 720 v3 model is utilized to investigate the distribution of crustal magnetic anomaly and curie surface in the ordos block and its surrounding areas the curie surface is compared with the regional heat flow bouguer anomalies moho and seismicity the interior block has strong wide distributed magnetic anomalies well corresponding to the basement lithofacies the surrounding areas have weak anomalies of various strikes and intensities the magnetic anomaly confirms the geological finding that the yabulai and bayanhot basins are small blocks detached from the northern ordos block the magnetic anomalies at the satellite altitude reveal that deep materials flow northward from the northeast margin of tibet plateau to the qilian fold belt the depth of curie surface ranges from 24 to 42 km and the ordos block is dominated by curie surface depth over 32 km and average heat flow value of 44 mw m2 the distribution of bouguer anomalies is consistent with that of magnetic anomalies the well correlation between the curie surface and the seismicity is also explained

the distribution of tropical thin cirrus clouds inferred from terra modis data thin cirrus clouds with optical depths t k 1 play a potentially important role in the earth s atmosphere however their tenuous nature makes them difficult to detect and as a result there are few quantitative global analyses of them the moderate resolution imaging spectrometer modis on board the terra satellite has a channel at 1 375 mm that is specifically designed to detect these clouds and can measure optical depths as low as 0 02 with an uncertainty factor of 2 during two 3 day periods from december 2000 and june 2001 about one third of the pixels flagged as cloud free by the modis cloud mask are shown to contain detectible thin cirrus these thin cirrus generally have optical depths below 0 05 and appear with greater frequency and optical depth near deep convection

a modeling assessment of the interplay between aeolian iron fluxes and iron binding ligands in controlling carbon dioxide fluctuations during antarctic warm events 1 we add a prognostic biogeochemical model to the bern3d ocean circulation model to test the impact of increased aeolian iron fluxes in various regions of the ocean on long time scales atmospheric co2 is most sensitive when modern dust flux is increased 100 fold in the southern ocean for 1000 years resulting in a reduction of 10 ppmv seeding the indian ocean and south pacific results in increased export production and co2 drawdown in the southern ocean due to interbasinal transport of iron the non sea salt calcium record from dome c antarctica is used to scale aeolian iron deposition in the southern ocean in transient simulations over four antarctic warm events of the last glacial period our results suggest changes in dust flux to the southern ocean played a limited role in modulating co2 variations the impact of iron fluxes on co2 is dependent on parameter values chosen for the iron binding ligand

geological modeling of the new champ magnetic anomaly maps using a geographical information system technique 1 reliable global crustal field anomaly maps produced from magnetic measurements of the champ satellite mission now allow for quantitative geological studies of crustal structure and composition we have developed a gis based forward modeling technique to model these anomaly maps on the basis of the geologic and tectonic maps of the world laboratory susceptibility values of the occurring rock types and the seismic thickness of the crust a vertically integrated susceptibility grid is generated in the gis system in addition a remanent magnetization grid is computed for the oceanic crust using a digital isochron map of the ocean floor and rotation models of the paleoplates combining the global vis and remanent magnetization grids the vertical magnetic field anomaly is computed at satellite altitude and compared with the corresponding champ magnetic anomaly map over the oceans induced and remanent magnetization explains well the prominent observed anomalies over the cretaceous quiet zones we also find a good agreement between predicted and observed anomalies over the continents remaining discrepancies between the predicted and observed anomalies can be used to adjust poorly known boundaries and the composition of the buried precambrian provinces until the recomputed anomalies fit the observed anomalies the feasibility of this approach is demonstrated on greenland the west african craton bangui in central africa and the kolyma omolon block in siberia we conclude that quantitative information on the lateral extent the composition and the thickness of the lower crust within a precambrian province can thus be inferred from the new satellite magnetic anomaly maps

rapid changes of glacial climate simulated in a coupled climate model abrupt changes in climate termed dansgaard oeschger and heinrich events have punctuated the last glacial period approximately 100 10 kyr ago but not the holocene the past 10 kyr here we use an intermediate complexity climate model to investigate the stability of glacial climate and we find that only one mode of atlantic ocean circulation is stable a cold mode with deep water formation in the atlantic ocean south of iceland however a warm circulation mode similar to the present day atlantic ocean is only marginally unstable and temporary transitions to this warm mode can easily be triggered this leads to abrupt warm events in the model which share many characteristics of the observed dansgaard oeschger events for a large freshwater input such as a large release of icebergs the model s deep water formation is temporarily switched off causing no strong cooling in greenland but warming in antarctica as is observed for heinrich events our stability analysis provides an explanation why glacial climate is much more variable than holocene climate

deep water formation in the north pacific and deglacial co2 rise deep water formation in the north atlantic and southern ocean is widely thought to influence deglacial co 2 rise and climate change here we suggest that deep water formation in the north pacific may also play an important role we present paired radiocarbon and boron isotope data from foraminifera from sediment core md02 2489 at 3640 m in the north east pacific these show a pronounced excursion during heinrich stadial 1 with benthic planktic radiocarbon offsets dropping to 350 years accompanied by a decrease in benthic 11 b we suggest that this is driven by the onset of deep convection in the north pacific which mixes young shallow waters to depth old deep waters to the surface and low ph water from intermediate depths into the deep ocean this deep water formation event was likely driven by an increase in surface salinity due to subdued atmospheric monsoonal freshwater flux during heinrich stadial 1 the ability of north pacific deep water npdw formation to explain the excursions seen in our data is demonstrated in a series of experiments with an intermediate complexity earth system model these experiments also show that breakdown of stratification in the north pacific leads to a rapid 30 ppm increase in atmospheric co 2 along with decreases in atmospheric 13 c and 14 c consistent with observations of the early deglaciation our inference of deep water formation is based mainly on results from a single sediment core and our boron isotope data are unavoidably sparse in the key hs1 interval so this hypothesis merits further testing however we note that there is independent support for breakdown of stratification in shallower waters during this period including a minimum in 15 n younging in intermediate water 14 c and regional warming we also re evaluate deglacial changes in north pacific productivity and carbonate preservation in light of our new data and suggest that the regional pulse of export production observed during the bolling allerod is promoted by relatively stratified conditions with increased light availability and a shallow potent nutricline overall our work highlights the potential of npdw formation to play a significant and hitherto unrealized role in deglacial climate change and co 2 rise

constraint of the co2 rise by new atmospheric carbon isotopic measurements during the last deglaciation 1 the causes of the 80 ppmv increase of atmospheric carbon dioxide co2 during the last glacial interglacial climatic transition remain debated we analyzed the parallel evolution of co2 and its stable carbon isotopic ratio 13co2 in the european project for ice coring in antarctica epica dome c ice core to bring additional constraints agreeing well but largely improving the taylor dome ice core record of lower resolution our 13co2 record is characterized by a w shape with two negative 13co2 excursions of 0 5 during heinrich 1 and younger dryas events bracketing a positive 13co2 peak during the bolling allerod warm period the comparison with marine records and the outputs of two c cycle box models suggest that changes in southern ocean ventilation drove most of the co2 increase with additional contributions from marine productivity changes on the initial co2 rise and 13co2 decline and from rapid vegetation buildup during the co2 plateau of the bolling allerod

origin and consequences of cyclic ice rafting in the northeast atlantic ocean during the past 130 000 years deep sea sediment cores recovered from the northeast atlantic ocean were examined in order to elucidate the influence of the earth s orbital parameters on major ice rafting analyses of coarse grained ice rafted debris and planktonic foraminifers revealed a strong reaction to the precession signal since 130 000 yr b p dropstone layers have been deposited each half period of a precessional cycle 11 000 1000 yr ice rafting occurs during times of winter minimum summer maximum insolation and summer minimum winter maximum insolation in the first case high summer insolation forces meltwater discharge from the ice sheets into the polar seas which subsequently enhances formation of sea ice during the winter in the second case growth of continental ice enhances iceberg production which also leads to a salinity reduction of surface seawater both situations result in a southward penetration of polar water thus the marine record of dropstones documents ice rafting not only during weichselian stades but also during cold events within interstades the regularity of ice rafting yields a useful framework to calibrate and elucidate climatic changes not only in the region of the north atlantic ocean but also in remote areas such as the pacific ocean and the antarctic

north atlantic ventilation of southern sourced deep water in the glacial ocean one potential mechanism for lowering atmospheric co2 during glacial times is an increase in the fraction of the global ocean ventilated by the north atlantic which produces deep water with a low concentration of unused nutrients and thus drives the ocean s biological pump to a high efficiency however the data indicate that during glacial times a water mass low in 13c 12c and 14c c occupied the deep atlantic apparently at the expense of north atlantic deep water nadw this water is commonly referred to as southern sourced because of its apparent entry into the atlantic basin from the south prompting the inference that it was ventilated at the southern ocean surface here we propose that this deep atlantic water mass actually included a large fraction of north atlantic ventilated water the chemical characteristics of which were altered by recirculation in the deep southern and indo pacific oceans in an ocean model sensitivity experiment that reduces antarctic bottom water formation and weakens its overturning circulation we find that a much greater fraction of nadw is transported into the southern ocean without contacting the surface and is entrained and mixed into the southern sourced deep water that spreads into the global abyssal ocean thus north atlantic ventilation takes over more of the ocean interior lowering atmospheric co2 and yet the abyssal atlantic is filled from the south with old water low in 13c 12c and 14c c consistent with glacial data

impact of oceanic reorganizations on the ocean carbon cycle and atmospheric carbon dioxide content a zonally averaged circulation biogeochemical ocean model is used to explore how the distribution of po4 and 13c in the major basins and the atmospheric pco2 respond to rapid changes in the thermohaline circulation thc different evolutions of the atlantic thc are simulated by applying surface freshwater pulses typical for example of heinrich events and the last deglaciation in the model when the thc completely collapses po4 increases 0 5 mmol m 3 and 13c decreases 1 because of a longer residence time of waters at the surface these surface anomalies are propagated to the bottom north atlantic when the thc resumes when the thermohaline overturning is only partly reduced and at shallower depths changes in bottom waters are accompanied by a po4 decrease and 13c increase at intermediate levels in the mid latitude atlantic this results in enhanced vertical gradients of these properties consistent with chemical and isotopic reconstructions for the last glacial maximum finally the atmospheric pco2 increases during the cold period in the north atlantic when the thc is reduced with an amplitude 7 30 atm and timescale 10 to 1 2 10 yr depending on the intensity of the thc change this is qualitatively consistent with recent data from an antarctic ice core documenting a pco2 increase during the younger dryas and after heinrich events 4 and 5

atlantic pacific seesaw and its role in outgassing co2 during heinrich events 1 paleoproxy records indicate that a marked weakening of the atlantic meridional overturning circulation amoc during heinrich events was often accompanied by a notable atmospheric co2 increase however previous modeling studies display conflicting atmospheric co2 responses to an amoc shutdown here we use model simulations combined with paleoproxy records to show that depending on the deep and bottom water transport in the northern and southern pacific ocean during an amoc weakening the ocean can act either as a sink or a source of carbon results from idealized meltwater experiments as well as from a transient experiment covering heinrich stadial 4 suggest that a shutdown of the amoc during heinrich stadials 4 hs4 and 1 hs1 led to an enhancement of antarctic bottom water aabw and north pacific deep water npdw transport we show that enhanced deep and bottom water transport in the pacific ocean ventilates deep pacific carbon through the southern ocean thus contributing to a rise in atmospheric co2 this mechanism yields a good agreement between paleoproxy records and modeling results thus highlighting the possible establishment of an atlantic pacific seesaw during heinrich stadials enhanced aabw and npdw transport could account for most of the observed atmospheric co2 increase during hs4 and for about 30 of the atmospheric co2 increase during hs1

the impact of atmospheric pco2 on carbon isotope ratios of the atmosphere and ocean it is well known that the equilibration timescale for the isotopic ratios 13c 12c and 14c 12c in the ocean mixed layer is on the order of a decade 2 orders of magnitude slower than for oxygen less widely appreciated is the fact that the equilibration timescale is quite sensitive to the speciation of dissolved inorganic carbon dic in the mixed layer scaling linearly with the ratio dic co2 which varies inversely with atmospheric pco2 although this effect is included in models that resolve the role of carbon speciation in air sea exchange its role is often unrecognized and it is not commonly considered in the interpretation of carbon isotope observations here we use a global three dimensional ocean model to estimate the redistribution of the carbon isotopic ratios between the atmosphere and ocean due solely to variations in atmospheric pco2 under last glacial maximum lgm pco2 atmospheric 14c is increased by 30 due to the speciation change all else being equal raising the surface reservoir age by about 250 years throughout most of the ocean for 13c enhanced surface disequilibrium under lgm pco2 causes the upper ocean atmosphere and north atlantic deep water 13c to become at least 0 2 higher relative to deep waters ventilated by the southern ocean conversely under high pco2 rapid equilibration greatly decreases isotopic disequilibrium as a result during geological periods of high pco2 vertical 13c gradients may have been greatly weakened as a direct chemical consequence of the high pco2 masquerading as very well ventilated or biologically dead strangelove oceans the ongoing anthropogenic rise of pco2 is accelerating the equilibration of the carbon isotopes in the ocean lowering atmospheric 14c and weakening 13c gradients within the ocean to a degree that is similar to the traditional fossil fuel suess effect

atmospheric δ13co2 and its relation to pco2 and deep ocean δ13c during the late pleistocene the ratio of the stable carbon isotopes of atmospheric co2 13co2 contains valuable information on the processes which are operating on the global carbon cycle however current 13co2 ice core records are still limited in both resolution and temporal coverage as well as precision in this study we performed simulations with the carbon cycle box model bicycle with special emphasis on atmospheric 13co2 proposing how changes in 13co2 might have evolved over the last 740 000 years we furthermore analyze the relationship between atmospheric 13co2 pco2 and deep ocean 13c of dissolved inorganic carbon dic 13cdic in both our modeling framework and proxy records when available our analyses show that mean ocean and deep pacific 13cdic are mainly controlled by the glacial interglacial uptake and release of carbon temporarily stored in the terrestrial biosphere during warmer climate periods in contrast glacial interglacial changes in pco2 and 13co2 represent mainly a mixture of ocean related processes superimposed on the slow glacial interglacial change in terrestrial carbon storage the different processes influencing atmospheric 13co2 largely compensate each other and cancel all variability with frequencies of 1 100 kyr 1 large excursions in 13co2 can a priori be expected as any small phase difference between the relative timing of the dominant and opposite sign processes might create large changes in 13co2 amplitudes in 13co2 caused by fast terrestrial uptake or release during millennial scale climate variability depend not only on the amount of transferred carbon but also on the speed of these changes those which occur on timescales shorter than a millennium are not detectable in 13co2 because of gas exchange equilibration with the surface ocean the 13co2 signal of fast processes on the other hand is largely attenuated in ice core records during the firnification and gas enclosure we therefore suggest to measure 13co2 with priority on ice cores with high temporal resolution and select times with rather fast climatic changes

usarray shear wave splitting shows seismic anisotropy from both lithosphere and asthenosphere north america provides an important test for assessing the coupling of large continents with heterogeneous archean to cenozoic aged lithospheric provinces to the mantle flow we use the unprecedented spatial coverage of the usarray seismic network to obtain an extensive and consistent data set of shear wave splitting intensity measurements at 1436 stations overall the measurements are consistent with simple shear deformation in the asthenosphere due to viscous coupling to the overriding lithosphere the fast directions agree with the absolute plate motion direction with a mean difference of 2 with 27 standard deviation there are however deviations from this simple pattern including a band along the rocky mountain front indicative of flow complication due to gradients in lithospheric thickness and variations in amplitude through the central united states which can be explained through varying contributions of lithospheric anisotropy thus seismic anisotropy may be sourced in both the asthenosphere and lithosphere and variations in splitting intensity are due to lithospheric anisotropy developed during deformation over long time scales

temperature differences between the hemispheres and ice age climate variability 1 the earth became warmer and cooler during the ice ages along with changes in the earth s orbit but the orbital changes themselves are not nearly large enough to explain the magnitude of the warming and cooling atmospheric co2 also rose and fell but again the co2 changes are rather small in relation to the warming and cooling so how did the earth manage to warm and cool by so much here we argue that for the big transitions at least the earth did not warm and cool as a single entity rather the south warmed instead at the expense of a cooler north through massive redistributions of heat that were set off by the orbital forcing oceanic co2 was vented up to the atmosphere by the same redistributions the north then warmed later in response to higher co2 and a reduced albedo from smaller ice sheets this form of north south displacement is actually very familiar as it is readily observed during the younger dryas interval 13 000 years ago and in the various millennial scale events over the last 90 000 years

resolution of direction of oceanic magnetic lineations by the sixth generation lithospheric magnetic field model from champ satellite magnetic measurements the champ satellite continues to provide highly accurate magnetic field measurements from decreasing orbital altitudes 350 km at solar minimum conditions using the latest 4 years 2004 2007 of readings from the champ fluxgate magnetometer including an improved scalar data product we have estimated the lithospheric magnetic field to spherical harmonic degree 120 corresponding to 333 km wavelength resolution the data were found to be sensitive to crustal field variations up to degree 150 down to 266 km wavelength but a clean separation of the lithospheric signal from ionospheric and magnetospheric noise sources was achieved only to degree 120 this new mf6 model is the first satellite based magnetic model to resolve the direction of oceanic magnetic lineations revealing the age structure of oceanic crust

imaging three dimensional crustal conductivity structures reflecting continental flood basalt effects hidden beneath thick intracratonic sedimentary basin a large scale array of long period magnetic data and a deep probing magnetotelluric profile were recorded in the intracratonic parana sedimentary basin in central eastern south america which presents a thick and extensive sedimentary magmatic sequence that allows its basement to be investigated only by indirect methods integration of the results from both methods showed that the crust beneath the basin presents several quasi linear highly conductive channeled zones with limited lateral extent in coincidence with some of the main tectonic structures recognized at the surface and a moderate but pervasive lithosphere conductivity enhancement beneath its central part upward movement of co2 bearing volatiles and magmas precipitating highly conducting mineral phases along discrete subvertical fault zones that served as feeder conduits for early cretaceous voluminous continental flood basalts was a likely process responsible for the localized conductivity enhancements correlation between some of the linear conductive zones and elongated magnetic anomalies and between the maximum depth occurrence of most of these conductive anomalies and the curie depth at which crustal rocks lose their magnetism gives strong support to interconnected iron oxides especially magnetite and iron sulfides such as pyrrhotite as the main conductive sources the moderate bulk conductivity increase in the crust and upper mantle beneath the central part of the basin is unexpected for a postulated cratonic basement and is tentatively associated with impregnation of the lithosphere by conducting minerals related either to widespread tectonic events in the ordovician or late precambrian or to dispersed magmatic residues of an early cretaceous magma differentiation contaminating the entire lithosphere

ventilation of the deep southern ocean and deglacial co2 rise past glacial interglacial increases in the concentration of atmospheric carbon dioxide co2 are thought to arise from the rapid release of co2 sequestered in the deep sea primarily via the southern ocean here we present radiocarbon evidence from the atlantic sector of the southern ocean that strongly supports this hypothesis we show that during the last glacial period deep water circulating around antarctica was more than two times older than today relative to the atmosphere during deglaciation the dissipation of this old and presumably co2 enriched deep water played an important role in the pulsed rise of atmospheric co2 through its variable influence on the upwelling branch of the antarctic overturning circulation

grimm the gfz reference internal magnetic model based on vector satellite and observatory data summary in this paper the new gfz reference internal magnetic model grimm is presented the model has been derived from nearly 6 yr of champ satellite data and 5 yr of observatory hourly means at high latitudes full vector satellite data are used at all local times which allows a separation between on one hand the fields generated by ionosphere and field aligned currents and on the other hand the fields generated in the earth s core and lithosphere this selection technique leads to a data set without gaps during the polar summers resulting in a core field model that has an unprecedented time resolution the modelled static core field secular variation and lithospheric field are all in good agreement with previously published magnetic field models order five b splines are used to model the variation in time of the core field the energy in the secular acceleration has therefore a smooth behaviour in time and increases continuously from 2003 5 mapping the field acceleration from 2001 5 to 2005 5 reveals its rapid and complex evolution over this time period at the earth s surface due to the applied regularization technique the acceleration energy in spherical harmonics 6 11 is significantly larger than for other models and we show that such a spectrum is acceptable

magnetic anomalies in the eastern caribbean despite the many different studies on the origin and evolution of the caribbean plate no proposal has been widely accepted so far a key element within this field of research is the characterization of the plate subsurface oceanic crust as it would clarify the conditions in which it originated the geological period when it formed and its possible geographical location at this first evolution stage based on partial results of this research work we can say that the conclusions of previous studies are valid to a great extent namely the ne sw orientation of the striped magnetic anomalies in the venezuelan basin s western section and the existence of w e preferentially oriented stripes parallel to the leeward antilles the magnetic response of the triangular section in the southeast of the venezuelan basin represents cretaceous magnetic quiet zone cmqz and therefore shows a considerable attenuation of the stripe pattern indicating that the whole east caribbean subsurface features oceanic crustal material as for the period recorded by the caribbean magnetic stripes we propose the interval between chrons m23 and m0 and part of cmqz the wavelengths of the identified anomalies suggest that the ridge associated with the formation of caribbean ocean floor was slow spreading when compared to average currently active ridges

how important are southern hemisphere wind changes for low glacial carbon dioxide a model study 1 the response of atmospheric co2 to modifications in the strength and position of southern hemisphere westerlies is examined with the bern3d ocean model the model responds more sensitively to changes in the wind amplitude than to variations in latitudinal position depending on the model setup a 50 reduction in wind strength leads to a co2 drawdown of 3 34 ppm while a 50 increase results in a rise of 10 24 ppm a poleward shift of 5 lowers co2 by 2 16 ppm whereas an equatorward shift of 5 induces a co2 increase of 2 14 ppm physical and biological mechanisms equally contribute to the modeled changes in atmospheric co2 our results are in conflict with the hypothesis that southern hemisphere wind changes are responsible for the low atmospheric co2 concentrations during glacial periods

the 13c record for atmospheric co2 what is it trying to tell us abstract records of the 13c to 12c ratio of atmospheric co2 13catm trapped in antarctic ice may offer important insights into past changes in the carbon cycle and drivers of past fluctuations in atmospheric pco2 a recently published record offers the highest resolution 13catm record to date covering the last deglaciation schmitt et al 2012 two features are of particular interest one is the small magnitude 0 15 0 05 of the 13catm difference between the last glacial maximum lgm and the holocene the other is the abrupt drop 0 30 0 05 in 13catm between 17 5 and 16 0 ka this drop is coincident with that of dust deposition on the antarctic ice cap and into the ocean off south australia consistent with the hypothesis that increased efficiency of southern ocean nutrient utilization during the last glacial period and the consequent reduction in atmospheric pco2 was driven in part by dust related iron fertilization however in order to further explore either the small lgm holocene difference or the rapid drop during the early deglaciation 13catm changes related to the lgm cooling the lgm upper ocean 13c change ocean circulation changes and the lgm change in the photosynthetic fractionation factor must be known as each is currently the subject of a sizable uncertainty we present only a roadmap regarding what must be done in order to interpret the schmitt et al 2012 record

the last glacial termination a major puzzle of paleoclimatology is why after a long interval of cooling climate each late quaternary ice age ended with a relatively short warming leg called a termination we here offer a comprehensive hypothesis of how earth emerged from the last global ice age a prerequisite was the growth of very large northern hemisphere ice sheets whose subsequent collapse created stadial conditions that disrupted global patterns of ocean and atmospheric circulation the southern hemisphere westerlies shifted poleward during each northern stadial producing pulses of ocean upwelling and warming that together accounted for much of the termination in the southern ocean and antarctica rising atmospheric co2 during southern upwelling pulses augmented warming during the last termination in both polar hemispheres

age spreading rates and spreading asymmetry of the world s ocean crust we present four companion digital models of the age age uncertainty spreading rates and spreading asymmetries of the world s ocean basins as geographic and mercator grids with 2 arc min resolution the grids include data from all the major ocean basins as well as detailed reconstructions of back arc basins the age spreading rate and asymmetry at each grid node are determined by linear interpolation between adjacent seafloor isochrons in the direction of spreading ages for ocean floor between the oldest identified magnetic anomalies and continental crust are interpolated by geological estimates of the ages of passive continental margin segments the age uncertainties for grid cells coinciding with marine magnetic anomaly identifications observed or rotated to their conjugate ridge flanks are based on the difference between gridded age and observed age the uncertainties are also a function of the distance of a given grid cell to the nearest age observation and the proximity to fracture zones or other age discontinuities asymmetries in crustal accretion appear to be frequently related to asthenospheric flow from mantle plumes to spreading ridges resulting in ridge jumps toward hot spots we also use the new age grid to compute global residual basement depth grids from the difference between observed oceanic basement depth and predicted depth using three alternative age depth relationships the new set of grids helps to investigate prominent negative depth anomalies which may be alternatively related to subducted slab material descending in the mantle or to asthenospheric flow a combination of our digital grids and the associated relative and absolute plate motion model with seismic tomography and mantle convection model outputs represents a valuable set of tools to investigate geodynamic problems

an ellipsoidal harmonic representation of earth s lithospheric magnetic field to degree and order 720 1 while high degree models of the earth s gravity potential have been inferred from measurements for more than a decade corresponding geomagnetic models are difficult to produce the primary challenge lies in the estimation of the magnetic potential which is not completely determined by available field intensity measurements and cannot be computed by direct integration described here is the methodology behind the third generation of the national geophysical data center s degree 720 magnetic model key issues are 1 the ellipsoidal harmonic representation of the magnetic potential 2 the reduction of ambiguities by a suitable penalty function and 3 the use of an iterative method to estimate the model coefficients the ngdc 720 model provides the lithospheric magnetic field vector at any desired location and altitude close to and above the earth s surface anticipated uses are in geological and tectonic studies of the lithosphere as a local correction for magnetic navigation and heading systems and the calibration of ground marine airborne and spaceborne magnetometers the ngdc 720 model is available at http geomag org models ngdc720 html and for long term archive at http earthref org cgi bin er cgi s erda cgi n 989

crustal magnetic anomaly and curie surface beneath tarim basin china and its adjacent area based on the geomagnetic field model ngdc 720 v3 national geophysical data center the distribution of crustal magnetic anomalies and the curie surface beneath tarim basin china and its adjacent area were investigated the results show that the spatial distribution of the magnetic anomalies in tarim basin coincides with the regional tectonic structure i e a basin sandwiched between mountain ranges shallow parts of the curie surface are located in uplifted zones of the basin and correspond well to high values of heat flow in contrast deep parts of the curie surface having low values of heat flow are distributed along the depression zones of the basin the curie point depth is consistent with the measured heat flow value with a correlation coefficient of 0 65

impact of oceanic circulation changes on atmospheric δ13co2 co measured in antarctic ice cores provides constraints on oceanic and terrestrial carbon cycle processes linked with millennial scale changes in atmospheric co however the interpretation of co is not straight forward using carbon isotope enabled versions of the loveclim and bern3d models we perform a set of sensitivity experiments in which the formation rates of north atlantic deep water nadw north pacific deep water npdw antarctic bottom water aabw and antarctic intermediate water aaiw are varied we study the impact of these circulation changes on atmospheric co as well as on the oceanic co distribution in general we find that the formation rates of aabw nadw npdw and aaiw are negatively correlated with changes in co namely strong oceanic ventilation decreases atmospheric co however since large scale oceanic circulation reorganizations also impact nutrient utilization and the earth s climate the relationship between atmospheric co levels and ocean ventilation rate is not unequivocal in both models atmospheric co is very sensitive to changes in aabw formation rates increased aabw formation enhances the transport of low co waters to the surface and decreases atmospheric co by contrast the impact of nadw changes on atmospheric co is less robust and might be model dependent this results from complex interplay between global climate carbon cycle and the formation rate of nadw a water body characterized by relatively high co

the geomagnetic power spectrum summary combining champ satellite magnetic measurements with aeromagnetic and marine magnetic data the global geomagnetic field has now been modelled to spherical harmonic degree 720 an important tool in field modelling is the geomagnetic power spectrum it allows the comparison of field models estimated from different data sets and can be used to identify noise levels and systematic errors a correctly defined geomagnetic power spectrum is flat white for an uncorrelated field such as the earth s crustal magnetic field at long wavelengths it can be inferred from global spherical harmonic models as well as from regional grids marine and aeromagnetic grids usually represent the anomaly of the total intensity of the magnetic field appropriate corrections have to be applied in estimating the geomagnetic power spectrum from such data the comparison of global and regional spectra using a consistently defined azimuthally averaged geomagnetic power spectrum facilitates quality control in field modelling and should provide new insights in magnetic anomaly interpretation

emag2 a 2 arc min resolution earth magnetic anomaly grid compiled from satellite airborne and marine magnetic measurements 1 a global earth magnetic anomaly grid emag2 has been compiled from satellite ship and airborne magnetic measurements emag2 is a significant update of our previous candidate grid for the world digital magnetic anomaly map the resolution has been improved from 3 arc min to 2 arc min and the altitude has been reduced from 5 km to 4 km above the geoid additional grid and track line data have been included both over land and the oceans wherever available the original shipborne and airborne data were used instead of precompiled oceanic magnetic grids interpolation between sparse track lines in the oceans was improved by directional gridding and extrapolation based on an oceanic crustal age model the longest wavelengths 330 km were replaced with the latest champ satellite magnetic field model mf6 emag2 is available at http geomag org models emag2 and for permanent archive at http earthref org cgi bin er cgi s erda cgi n 970

high resolution aeromagnetic data over central australia assist grenville era 1300 1100 ma rodinia reconstructions 1 high resolution aeromagnetic data covering the polydeformed and poorly exposed musgrave province of australia reveals the grenville aged crustal architecture a combination of upward continuation and the potential field tilt filter out magnetic anomalies relating to a late neoproterozoic orogenic event and emphasize the more subtle magnetic structural grain formed during the ca 1320 1150 ma musgravian orogeny the resulting images indicate that crustal architecture is defined by the distribution of ca 1150 ma magnetic granitoids within less magnetic basement and is dominantly northeast trending continuous beneath the amadeus and officer basins and defines an orogenic belt that connects mesoproterozoic provinces the orogenic belt is truncated within australia and precludes a direct east trending connection between the musgrave province and contemporaneous orogens in laurentia clockwise rotation of the south australian craton and subsequent collision with the north and west australian cratons is our preferred model to explain the grenville aged architecture observed in australia

a coupled dynamical ocean energy balance atmosphere model for paleoclimate studies abstract the bern3d coupled three dimensional dynamical ocean energy balance atmosphere model is introduced and the atmospheric component is discussed in detail the model is of reduced complexity developed to perform extensive sensitivity studies and ensemble simulations extending over several glacial interglacial cycles on large space scales the modern steady state of the model compares well with observations in a first application several 800 000 yr simulations with prescribed orbital greenhouse gas and ice sheet forcings are performed the model shows an increase of atlantic meridional overturning circulation strength at glacial inceptions followed by a decrease throughout the glaciation and ending in a circulation at glacial maxima that is weaker than at present the sensitivity of ocean temperature to atmospheric temperature atlantic meridional overturning circulation amoc and antarctic bottom water aabw strength is analyzed at 23 locations in a second application the climate sensitivi

merging airborne magnetic surveys into continental scale compilations regional compilations of airborne magnetic data are becoming more common as national databases grow grids of the magnetic survey data are joined together to form geological province scale or even continental scale compilations the advantage of these compilations is that large tectonic features and geological provinces can be better mapped and interpreted we take a holistic approach to the joining of survey grids the leveling of the grids into a regional compilation is treated as a single inverse problem we use the weighted least squares method to find the best adjustment for each survey grid such that the data value differences in the grid overlap areas are minimized the method spreads any inconsistencies between grids among all of the grid overlap areas and minimizes the introduction of long wavelength errors into the composite grid this is an improvement on the conventional approach of joining grids sequentially a comparison of leveled data over western australia with diurnally corrected long aero

magnetotelluric images of paleoproterozoic accretion and mesoproterozoic to neoproterozoic reworking processes in the northern sao francisco craton central eastern brazil abstract broadband and long period magnetotelluric mt data were collected along an east west oriented 580 km long profile across the northern sao francisco craton where extensive proterozoic and phanerozoic sedimentary cover and lack of deep probing geophysical surveys have prevented to establish unequivocally the cratonic character of the archean paleoproterozoic lithosphere following dimensionality analyses the mt dataset was interpreted using both 2 d and 3 d inversion procedures the near surface structure is better resolved in the 2 d model due to its finer resolution a huge upper crustal conductor is found all along the shallow early neoproterozoic irece basin in the central domain of the craton extending laterally for approximately 150 km and restricting signal propagation below the basin its high conductance is explained by a combination of high porosity and high fluid salinity in the sedimentary package another upper crustal conductor is observed on the west side of the profile interpreted as fractured metasedimentary rocks of the rio preto belt thrusted on top of the craton basement during neoproterozoic marginal collision the 3 d model explains significantly better the measured data related to deep structure contrary to what is expected for a stable cratonic block the geoelectric model shows pronounced electrical complexity and heterogeneity an indication that the cratonic lithosphere was multiply reworked in the past by tectonothermal events different lithospheric resistive blocks bounded by major conductive zones are identified constrained by geochemical and isotopic data these vertical conductive interfaces are interpreted as cryptic suture zones due to large scale amalgamation of continents and microcontinents leading to the assembly of the sao francisco craton in the paleoproterozoic the conductivity enhancement is more likely explained by emplacement of sulfides along previous suture zones during mafic magmatism at upper mantle depths high conductivity observed below most of the profile indicates that metasomatism or refertilization processes with incompatible elements caused by the paleoproterozoic subducting slabs and mesoproterozoic to neoproterozoic upwelling of deep fluids and melts reworked this portion of the craton mantle

fifth generation lithospheric magnetic field model from champ satellite measurements 1 six years of low orbit champ satellite magnetic measurements have provided an exceptionally high quality data resource for lithospheric magnetic field modeling and interpretation here we describe the fifth generation satellite only magnetic field model mf5 the model extends to spherical harmonic degree 100 as a result of careful data selection extensive corrections filtering and line leveling the model has low noise levels even if evaluated at the earth s surface the model is particularly suited for inferring large scale structure and composition of the lithosphere it is also meant to serve as the long wavelength part of continental and global scale marine and aeromagnetic anomaly maps

lowering of glacial atmospheric co2 in response to changes in oceanic circulation and marine biogeochemistry 1 we use an earth system model of intermediate complexity climber 2 to investigate what recent improvements in the representation of the physics and biology of the glacial ocean imply for the atmospheric concentration the coupled atmosphere ocean model under the glacial boundary conditions is able to reproduce the deep salty stagnant water mass inferred from antarctic deep pore water data and the changing temperature of the entire deep ocean when carbonate compensation is included in the model we find a co2 drawdown of 43 ppmv associated mainly with the shoaling of the atlantic thermohaline circulation and an increased fraction of water masses of southern origin in the deep atlantic fertilizing the atlantic and indian sectors of the southern ocean north of the polar front leads to a further drawdown of 37 ppmv other changes to the glacial carbon cycle include a decrease in the amount of carbon stored in the terrestrial biosphere 540 pg c which increases atmospheric co2 by 15 ppmv and a change in ocean salinity resulting from a drop in sea level which elevates co2 by another 12 ppmv a decrease in shallow water caco3 deposition draws down co2 by 12 ppmv in total the model is able to explain more than two thirds 65 ppmv of the glacial to interglacial co2 change based only on mechanisms that are clearly documented in the proxy data a good match between simulated and reconstructed distribution of 13c changes in the deep atlantic suggests that the model captures the mechanisms of reorganization of biogeochemistry in the atlantic ocean reasonably well additional poorly constrained mechanisms to explain the rest of the observed drawdown include changes in the organic carbon caco3 ratio of sediment rain reaching the seafloor iron fertilization in the subantarctic pacific ocean and changes in terrestrial weathering

magnetic anomaly map of the world merging satellite airborne marine and ground based magnetic data sets abstract we report here a simple but practical method to combine systematically the magnetic surveys of disparate specifications from marine ground aeromagnetic and satellite platforms that aims to be helpful in the framework of the world digital magnetic anomaly map project because the satellite coverage and data quality is more uniform than near surface surveys it is adopted as the base map for wavelengths larger than 400 km and up to spherical harmonic degree inclusive of 16 2500 km after checking that satellite models and large aeromagnetic wavelengths are not consistent we filter out wavelengths longer than 400 km in aeromagnetic compilations existing regional grids and when available individual surveys are merged to give a more uniform spatial variation of the magnetic anomalies the effects of merging the grids are examined by plotting profiles and difference maps of the overlapping regions a preliminary global map is obtained after combining the magnetic anomaly map with the downward continued champ satellite derived magnetic anomaly map forthcoming availability of new datasets as well as improvements in the procedure will help to produce increasingly reliable maps

extending comprehensive models of the earth s magnetic field with orsted and champ data summary a new model of the quiet time near earth magnetic field has been derived using a comprehensive approach which includes not only pogo and magsat satellite data but also data from the orsted and champ satellites the resulting model shows great improvement over its predecessors in terms of completeness of sources time span and noise reduction in parameters with its well separated fields and extended time domain of 1960 to mid 2002 the model is able to detect the known sequence of geomagnetic jerks within this frame and gives evidence for an event of interest around 1997 because all sources are coestimated in a comprehensive approach intriguing north south features typically filtered out with other methods are being discovered in the lithospheric representation of the model such as the s atlantic spreading ridge and andean subduction zone lineations in addition this lithospheric field exhibits significantly less noise than previous models as a result of improved data selection the f region currents through which the satellites pass are now treated as lying within meridional planes as opposed to being purely radial results are consistent with those found previously for magsat but an analysis at orsted altitude shows exciting evidence that the meridional currents associated with the equatorial electrojet likely close beneath the satellite besides the model a new analysis technique has been developed to infer the portion of a model parameter state resolved by a particular data subset this has proven very useful in diagnosing the cause of peculiar artefacts in the magsat vector data which seem to suggest the presence of a small misalignment bias in the vector magnetometer

third generation of the potsdam magnetic model of the earth pomme the potsdam magnetic model of the earth pomme is a geomagnetic field model providing an estimate of the earth s core crustal magnetospheric and induced magnetic fields the internal field is represented to spherical harmonic sh degree 90 while the secular variation and acceleration are given to sh degree 16 static and time varying magnetospheric fields are parameterized in geocentric solar magnetospheric gsm and solar magnetic sm coordinates and include disturbance storm time dst index and interplanetary magnetic field imf by dependent contributions the model was estimated from five years of champ satellite magnetic data all measurements were corrected for ocean tidal induction and night side ionospheric f region currents the model is validated using an independent model from a combined data set of orsted and sac c satellite measurements for the core field to sh degree 13 the root mean square rms vector difference between the two models at the center of the model period is smaller than 4 nt at the earth s surface the rms uncertainty increases to about 100 nt for the predicted field in 2010 as inferred from the difference between the two models

national geophysical data center candidate for the world digital magnetic anomaly map marine and airborne magnetic anomaly data have been collected for more than half a century providing global coverage of the earth furthermore the german champ satellite is providing increasingly accurate information on large scale magnetic anomalies the world digital magnetic anomaly map project is an international effort to integrate all available near surface and satellite magnetic anomaly data into a global map database teams of researchers were invited to produce candidate maps using a common pool of data sets here we present the national geophysical data center ngdc candidate to produce a homogeneous map the near surface data were first line leveled and then merged by least squares collocation long wavelengths were found to agree surprisingly well with independent satellite information this validates our final processing step of merging the short wavelength part of the near surface data with long wavelength satellite magnetic anomalies

new insights into regional tectonics of the sunda banda arcs region from integrated magnetic and gravity modelling abstract the lombok island indonesia situated along the sunda banda arcs transition region lies between zones characterized by very large intensity magnetic anomalies these anomalies have been noted as being part of the eight most important ones seen on the 1st edition of the world digital magnetic anomaly map unfortunately only marine magnetic data of surroundings are available and no regional high resolution magnetic surveys of this island had been done since 2004 we have carried out several geomagnetic ground surveys in this region here we present modelling results for a new geological and tectonic interpretation of the magnetic anomalies the new results confirm the general pattern of contiguous negative positive anomalies revealing two active quaternary normal faults and a magmatic arc related to a subduction region this outcome agrees with earlier results in surrounding areas obtained by satellite aeromagnetic and marine platforms and provides a more detailed picture of strong anomalies on this island considering both magnetic anomalies and gravity models it is possible to suggest an extension of the flores thrust zone reaching the northwest off the lombok island the flores thrust zone may be considered as a mature subduction in the back arc region showing a tendency of progressive subduction during last decades

the southern ocean s role in carbon exchange during the last deglaciation changes in the upwelling and degassing of carbon from the southern ocean form one of the leading hypotheses for the cause of glacial interglacial changes in atmospheric carbon dioxide we present a 25 000 year long southern ocean radiocarbon record reconstructed from deep sea corals which shows radiocarbon depleted waters during the glacial period and through the early deglaciation this depletion and associated deep stratification disappeared by 14 6 ka thousand years ago consistent with the transfer of carbon from the deep ocean to the surface ocean and atmosphere via a southern ocean ventilation event given this evidence for carbon exchange in the southern ocean we show that existing deep ocean radiocarbon records from the glacial period are sufficiently depleted to explain the 190 per mil drop in atmospheric radiocarbon between 17 and 14 5 ka

a revised 1000 year atmospheric δ13c co2 record from law dome and south pole antarctica 1 we present new measurements of 13c of co2 extracted from a high resolution ice core from law dome east antarctica together with firn measurements performed at law dome and south pole covering the last 150 years our analysis is motivated by the need to better understand the role and feedback of the carbon c cycle in climate change by advances in measurement methods and by apparent anomalies when comparing ice core and firn air 13c records from law dome and south pole we demonstrate improved consistency between law dome ice south pole firn and the cape grim tasmania atmospheric 13c data providing evidence that our new record reliably extends direct atmospheric measurements back in time we also show a revised version of early 13c measurements covering the last 1000 years with a mean preindustrial level of 6 50 finally we use a kalman filter double deconvolution to infer net natural co2 fluxes between atmosphere ocean and land which cause small 13c deviations from the predominant anthropogenically induced 13c decrease the main features found from the previous 13c record are confirmed including the ocean as the dominant cause for the 1940 a d co2 leveling our new record provides a solid basis for future investigation of the causes of decadal to centennial variations of the preindustrial atmospheric co2 concentration those causes are of potential significance for predicting future co2 levels and when attempting atmospheric verification of recent and future global carbon emission mitigation measures through coupled climate carbon cycle models