timing and origin of recent regional ice mass loss in greenland within the last decade the greenland ice sheet gris and its surroundings have experienced record high surface temperatures mote 2007 box et al 2010 ice sheet melt extent fettweis et al 2011 and record low summer sea ice extent nghiem et al 2007 using three independent data sets we derive for the first time consistent ice mass trends and temporal variations within seven major drainage basins from gravity fields from the gravity recovery and climate experiment grace tapley et al 2004 surface ice velocities from inteferometric synthetic aperture radar insar rignot and kanagaratnam 2006 together with output of the regional atmospheric climate modelling racmo2 gr ettema et al 2009 and surface elevation changes from the ice cloud and land elevation satellite icesat sorensen et al 2011 we show that changing ice discharge d surface melting and subsequent run off m r and precipitation p all contribute in a complex and regionally variable interplay to the increasingly negative mass balance of the gris observed within the last decade interannual variability in p along the northwest and west coasts of the gris largely explains the apparent regional mass loss increase during 2002 2010 and obscures increasing m r and d since the 1990s in winter 2002 2003 and 2008 2009 accumulation anomalies in the east and southeast temporarily outweighed the losses by m r and d that prevailed during 2003 2008 and after summer 2010 overall for all basins of the gris the decadal variability of anomalies in p m r and d between 1958 and 2010 w r t 1961 1990 was significantly exceeded by the regional trends observed during the grace period 2002 2011 2012 elsevier b v

validation of the ice 3g model of wurm wisconsin deglaciation using a global data base of relative sea level histories a global data base consisting of radiocarbon controlled relative sea level rsl histories from 392 different geographic locations has been compiled for use in analyses of the glacial isostatic adjustment process these data may be employed to constrain both the spatiotemporal characteristics of the last deglaciation event of the current ice age and the rheological structure of the planetary interior in a previous paper in this series tushingham and peltier 1991 we employed the rsl data in this set from sites that were once ice covered to refine the apriori model of deglaciation that had been delivered by past research in the area of pleistocene geomorphology peltier and andrews 1976 wu and peltier 1983 to produce a new global model of this event that we have called ice 3g in the present paper following a description of the full data base and of the methods used to compile it we employ data from the sites that were not ice covered 200 time series to verify the plausibility of this refined model of deglaciation and to test the extent to which the totality of the observations constrain the radial viscoelastic structure of the planet the analysis of solutions to the forward problem presented here reinforce previous inferences of a preference for a thick lithosphere by rsl data from sites along the u s east coast and a preference by data from most near field sites for an increase in viscosity across the 670 km discontinuity in the mantle by a factor of approximately 2 when the viscosity of the upper mantle is fixed to the value of 1021 pa s originally deduced by haskel 1935 on the basis of his analysis of the data from fennoscandia

seasonal variation of counterclockwise eddies downstream of the tsushima islands abstract the seasonal variation of counterclockwise eddies downstream of the tsushima islands in the tsushima straits was investigated from 2004 to 2008 using long term acoustic doppler current profiler adcp data eddy activity was high from summer to autumn july november the eddies were formed in short term intervals of 5 8 days almost corresponding to the formation cycle of karman vortices the eddy activity varied on a longer time period about 13 days the mean kinetic energy mke converted to eddy kinetic energy eke at current shears between the eastern and western channels of the tsushima straits the counterclockwise eddies that formed downstream of the tsushima islands were intensified and maintained by energy conversion from mke to eke at the northern shear of the current core in the eastern channel the countercurrent east of the tsushima islands from summer to autumn was intensified by energy conversion from eke to mke

understanding the responses of sea surface temperature to the two different types of el nino in the western north pacific abstract in this study we examine the physical processes of the response of sea surface temperature sst in the western north pacific to the two different types of el nino the central pacific el nino and the eastern pacific el nino while a center of anomalous warm sst is observed in the eastern tropical pacific in the case of the eastern pacific el nino it is located in the central tropical pacific for the central pacific el nino we investigate the detailed sst response in the kuroshio extension region where the anomalous sst is warm cool in the central pacific el nino eastern pacific el nino during the boreal fall and winter we diagnose the sst tendency to identify the roles of the surface net heat fluxes and ekman transport during the fall and winter the atmospheric teleconnections over the north pacific are quite different between the two types of el nino which might be due to changes in atmospheric diabatic forcing in relation to rainfall in the tropical pacific our results suggest that the physical processes which are responsible for the western north pacific sst in response to the two different types of el nino are basically similar that is ekman heat transport plays a key role in warming and cooling of the sst anomalies in the kuroshio extension region in the central pacific el nino and eastern pacific el nino respectively in contrast the net surface heat fluxes act to weaken the sst anomalies this result indicates that changes in the anomalous atmospheric circulation over the north pacific which is directly associated with ekman currents at the upper levels are important to determine the responses of sst in the kuroshio extension region to the two types of el nino

short term flow and water temperature fluctuations in sagami bay japan associated with variations of the kuroshio during the non large meander path abstract short term flow and water temperature fluctuations in sagami bay were examined using mooring and hydrographic data observed during the non large meander path nlm of the kuroshio in the surface layer 1 in the central part of the bay this flow is a part of an intrusion of kuroshio water via the oshima west channel into the bay and or a cyclonic circulation in the northern part of the bay the cyclonic circulation which is approximately balanced under the geostrophic flow relationship is mainly generated or enhanced by the intrusion which is accompanied by eastward propagation of the small meander of the kuroshio south of japan during the transition from the nearshore non large meander path nnlm to the offshore non large meander path onlm regardless of season the water temperature fluctuation in the subsurface layer 150 m is caused by upwelling of cold deeper water and is closely related to the eastward flow fluctuations in the surface layer in the central part of the bay our analysis leads us the conclusion that the upwelling occurs as the response of the subsurface density field to the surface flow field under the earth s rotation additionally the intrusion of kuroshio water via the oshima west channel tends to cause not only cyclonic circulation and upwelling in the northern part of the bay but also the kyucho which is the coastal density current under the earth s rotation in the bay s coastal area during the non large meander path nlm

post glacial rebound and transient lower mantle rheology summary although post glacial rebound data have been conventionally interpreted as being governed by the steady state component of the mantle viscosity spectrum the radial profile of this parameter which is then inferred by fitting a model to observations is characterized by the fact that it exhibits rather slight variation with depth this disagrees with expectations based upon microphysical models of the solid state creep process it also disagrees with very recent inferences of the viscosity stratification based on isostatic geoid anomalies expected on the basis of the internal lateral heterogeneity of mantle density obtained from seismic tomographic analyses the new calculations of the signatures of post glacial rebound reported here show that these two types of information are easily reconciled if the previously inferred value of the lower mantle viscosity is interpreted as a transient value as originally suggested by weertman on the basis of qualitative considerations in these new models considered here the steady state creep resistance of the lower mantle is not constrained at all by post glacial rebound observations it can be futed only by an appeal to other geophysical data whether such models are actually required by the data should become clear in the very near future

impact of upper ocean thermal structure on the intensity of korean peninsular landfall typhoons the roles of oceanic factors in the intensity of typhoons which made landfall on the korean peninsula kp are investigated using various meteorological and oceanic measurements and the best track data special attention is given an investigation of upper ocean thermal conditions necessary for becoming the most destructive typhoons on the kp based on hydrographic measurements and ocean modeling results the subsurface thermal structure sts along the track of the kp landfall typhoons reveals two distinct features the deep subsurface warm layer regions influenced by the kuroshio branch current west of kyushu kbcwk and the tsushima current tsc and the shallow subsurface warm layer regions influenced by the yellow sea bottom cold water ysbcw jeju island is a border dividing the two regions statistical analysis shows that 70 90 of the 10 strongest typhoons on the kp passed through the eastern side of jeju island where the warm ocean currents exist at the subsurface in contrast the majority of typhoons which passed over the ysbcw regions where cold water exists at the subsurface along the western side of jeju island experience a large surface temperature cooling due to the storm s self induced vertical mixing and upwelling resulting in a significant decrease in intensity these results demonstrate that the intensity of the kp landfall typhoons is very sensitive to the storm s track and how the difference in the upper ocean thermal structures in small areas can affect the typhoon intensity change

investigations of fennoscandian glacial isostatic adjustment using modern sea level records we present a new method for determining the rates from a network of regional tide gauge data the method involves using a model for the sea level observations annual averages of relative sea level that explicitly includes a term for the interannual sealevel variations which are assumed to be constant for all sites in the network the resulting simultaneous analysis of all the sea level observations yields sea level rates which are biased by the unknown temporal slope of the interannual variations by differencing sea level rate estimates with respect to one site site referenced sea level rates are calculated which are free from this bias the differencing procedure also removes any signal due to a common sea level rate such as might be associated with eustatic sea level rise the resulting site referenced sea level rates therefore in principle reflect only the relative vertical crustal motions of the tide gauge sites with respect to the geoid these site referenced sea level rates represent a potentially more accurate data set than have previously been used for sea level studies we have used these rates to investigate glacial isostatic adjustment gia in fennoscandia specifically we have used the site referenced sea level rates within the baltic sea to estimate adjustments to the ice history and earth model which are used to calculate vertical rates of adjustment due to gia a method never before used for fennoscandia the parameters selected were lithospheric thickness the viscosities of assumed isoviscous upper and lower mantles and a fennoscandian ice thickness scaling parameter we present the results of this estimation procedure for a specific test ice model we also find evidence that the sea level record for the site nearest the center of uplift furuogrund may be contaminated by systematic errors of unknown origin data from this site have previously been used to determine a rate for the maximum uplift that we find is perhaps 1 mm yr 1 or 10 too large

middle holocene sea level rise and highstand at 2 m central texas coast new data suggest a revised picture of middle holocene sea level change for the texas gulf of mexico coast and suggest reevaluation of coastal evolution first brackish marsh facies with calibrated radiocarbon ages of 7 7 to 7 8 ka have been recovered from depths of 8 5 to 9 m in a core from the ancestral colorado river delta and are interpreted to represent a sea level pinning point second a series of ridges along the copano bay margin farther south consist of shelly mud and fine sand with subtidal foram assemblages occur at elevations of 1 95 m above the modern intertidal zone and have produced calibrated radiocarbon ages on foram tests of ca 6 8 to 4 8 ka these ridges are interpreted to represent relict shallow subtidal to intertidal spits that provide minimum sea level positions for the middle holocene and are now emergent because of later sea level fall in aggregate these data show rates of sea level rise during this time period that are very comparable to or even lower than published eustatic rates and suggest a middle holocene sea level highstand for this non uplifting non rebounding and very slowly subsiding part of the north american coastline

inter annual and decadal sea level variations in the north western pacific marginal seas abstract long term sea level changes in the okhotsk japan east east china and yellow seas have been explored based on mean monthly values of sea level from tide gauge and altimetry measurements the analysis of low frequency sea level variability reveals clearly differentiated areas the okhotsk sea and the northern sector of the japan east sea display lower sea level variances and no sea level rise the southern japan east sea presents larger sea level variability associated with the circulation regime of the warm current entering through the tsushima strait and inter annual sea level variations that are driven by steric and atmospheric changes the largest sea level variances are found in the yellow sea due to the effect of atmospheric forcing over the continental shelf inter annual variability is spatially varying within the yellow sea and the east china sea and is mainly related to the steric sea level changes regional mean sea level indices have been synthesized for each area using the longest tide gauge records and have revealed correlations between the southern japan east and yellow seas with pdo and np climatic indices linear trends at coastal sites in the japan east east china and yellow seas show a rather heterogeneous pattern with values between 1 5 and 5 5 mm yr for the period 1960 2000 during the period 1993 2008 linear trends derived from coastal tide gauges and from altimetry observations are coherent and reveal a southwards increasing pattern with maximum averaged values reached at the yellow sea 4 9 1 9 mm yr followed by the japan east sea 3 8 0 9 mm yr decadal rates of sea level change show distinct behaviour among basins as well as with the global average the southern japan east sea the east china sea and the yellow sea display decadal variability which is out of phase with respect to the global values

deglaciation induced vertical motion of the north american continent and transient lower mantle rheology the last deglaciation event of the current ice age which began approximately 18 000 years ago and ended about 7000 years ago continues to exert a profound influence on the vertical motion of the solid earth in and surrounding the regions which were once ice covered observations of such vertical motions may be employed to constrain the radial viscoelastic structure of the planet and therefore to contribute in an important way to the understanding of geodynamic processes in general in this paper both present day rates of vertical motion as recorded on tide gauges and long time scale records of vertical motion as recorded in 14c controlled relative sea level histories are employed to refine previously constructed models of the radial viscoelastic structure an interesting sidelight to this analysis is the demonstration that the lower mantle viscosity inferred from the vertical motion data could represent a transient rather than the steady state value a fact which would help considerably to reconcile the small viscosity stratification required by the glacial rebound data with the large stratification which seems to be required by some recent analyses of the geoid height anomalies associated with internal density heterogeneity of the mantle which has been revealed by application of seismic tomographic techniques a further product of these new analyses is obtained by the application of the glacial isostatic adjustment model to filter this signal from the secular trends of relative sea level observed on tide gauges from both the east and west coasts of the north american continent these results may be important in the context of recently proposed scenarios of climatic change

a reappraisal of postglacial decay times from richmond gulf and james bay canada decay times inferred from relative sea level rsl histories of previously glaciated regions provide a potentially important constraint on mantle rheology we present a new compilation of rsl data from richmond gulf and james bay canada this recompilation reveals errors in previous compilations that led to inaccurate estimates for the richmond gulf decay time in a series of recently published articles we derive updated estimates for the decay time at richmond gulf and james bay using a methodology that incorporates errors in both the age and the height of the sea level markers this exercise is guided by a series of synthetic rsl calculations that show that decay time estimates in the region can be significantly biased if the rsl time series are not corrected for global eustatic sea level trends or if the estimates are based on composite rsl histories derived by combining data from both the richmond gulf and the james bay regions our decay time analysis for richmond gulf applies the pioneering approach of walcott 1980 to a large database and we derive a value of 4 0 6 6 kyr where the range is defined by a misfit tolerance 10 per cent higher than the minimum our analysis for james bay is based on the uplift curve derived by hardy 1976 and we estimate a decay time of about 2 0 2 8 kyr the difference between our estimates for richmond gulf and james bay may be due to errors in the observational record from these regions but could also be influenced by lateral variations in lithospheric structure associated with the assembly of laurentia

glacial isostatic adjustment i the forward problem summary the isostatic adjustment of a radially stratified visco elastic spheroid is treated using space time green functions for the associated surface mass load boundary value problem these impulse response functions are convolved with a heaviside function to give the time dependent deformation of the planet which would be produced by a unit point mass brought up from infinity at t 0 and allowed to remain on the surface the resulting heaviside green functions can be employed to simulate all of the important signatures of glacial isostatic adjustment given a space time dependent surface mass load consisting of ice sheet ablation histories and a model of the simultaneous filling of the ocean basins these source terms are simply convolved with the heaviside green function appropriate to a specific response signature a realistic model of the spatial distribution of the main late pleistocene ice loads and of their temporal disintegration is constructed the response of two visco elastic earth models is computed and compared to a global set of relaxation data relative sea level curves on the basis of this initial comparison of theory and observation the possibility that the lower mantle has a viscosity which is significantly in excess of the viscosity of the upper mantle is excluded in addition clear evidence of the presence of the lithosphere has been found in relaxation data from sites which were near the edge of the laurentide ice sheet such data should therefore prove useful as a basis for analysis of lateral variations in lithosphere thickness further extensions of the calculation are suggested

geoid anomalies in a dynamic earth in order to obtain a dynamically consistent relationship between the geoid and the earth s response to internal buoyancy forces we have calculated potential and surface deformation love numbers for internal loading these quantities depend on the depth and harmonic degree of loading they can be integrated as green functions to obtain the dynamic response due to an arbitrary distribution of internal density contrasts spherically symmetric self gravitating flow models are constructed for a variety of radial newtonian viscosity variations and flow configurations including both whole mantle and layered convection we demonstrate that boundary deformation due to internal loading reaches its equilibrium value on the same time scale as postglacial rebound much less than the time scale for significant change in the convective flow pattern by calculating relaxation times for a series of spherically symmetric viscous earth models for uniform mantle viscosity the geoid signature due to boundary deformations is larger than that due to internal loads resulting in net negative geoid anomalies for positive density contrasts geoid anomalies from intermediate wavelength density contrasts are amplified by up to an order of magnitude geoid anomalies are primarily the result of density contrasts in the interior of convecting layers density contrasts near layer boundaries are almost completely compensated layered mantle convection results in smaller geoid anomalies than mantle wide flow for a given density contrast viscosity stratification leads to more complicated spectral signatures because of the sensitivity of the dynamic response functions to model parameters forward models for the geoid can be used to combine several sources of geophysical data e g subducted slab locations seismic velocity anomalies surface topography to constrain better the structure and viscosity of the mantle

high resolution seismic profiling in the sea of marmara northwest turkey late quaternary sedimentation and sea level changes high resolution sparker seismic profiling was carried out in the sea of marmara northwest turkey to study the late quaternary tectonics and sedimentation of this important active basin at the western end of the north anatolian fault zone a sedimentary unit interpreted as the clinoforms of a prograding delta was observed in places along the outer part of the southern shelf the topset foreset transitions of the latest clinoforms cluster around 100 m below present sea level they were probably deposited during the last glacial maximum and early phase of deglaciation between 25 and 13 k y b p when the level of the aegean was below that of the dardanelles sill 60 70 m below sea level at present therefore the sea of marmara was isolated from the aegean during the last glacial maximum but it is possible that a fluvial overflow existed across the dardanelles during this time stabilizing the level of the marmara lake and allowing the delta progradation rivers that drain into the sea of marmara from the south have a much greater combined drainage basin area and sediment flux than those draining the region to the north this may explain the much broader shelf to the south half graben bounded by north dipping normal faults observed within the southern shelf would tend to trap sediment sourced from the south and subdue any sea bed morphology on the shelf

late quaternary sequence stratigraphy of a slowly subsiding passive margin new jersey continental shelf high resolution seismic profiles over a 25 000 km2 area off new jersey illustrate the effects of high amplitude high frequency eustasy on a slowly subsiding 0 2 mm yr passive margin analysis of 1600 km of geopulse uniboom minisparker and air gun profiles reveals four depositional sequences with a maximum total thickness of 100 m at the shelf edge correlation of these sequences to biostratigraphic and aminostratigraphic data from drill sites suggests all of these sequences may be post oxygen isotope stage 6 140 ka sequences i and iv appear to correspond to the major glacial interglacial sea level changes 120 m during oxygen isotope stages 6 5 and 2 1 respectively sequences ii and iii reflect smaller scale sea level fluctuations all sequence boundaries are interpreted as type 1 and sequences are predominantly composed of transgressive systems tracts tst and lowstand systems tracts lst much of the tst was deposited as incised valley fills parasequences in the tst commonly are isolated and fragmented the low subsidence rate and high frequency 20 k y eustatic oscillations result in extensive erosion and reworking of previously deposited sediments both by fluvial incision during lowstands and marine erosion during transgressions and highstands on continental margins where subsidence rates and sediment supply are low relative to rates of eustasy sequences are thin fragmented and difficult to correlate local effects such as shifting river drainage salt diapir movements and glacial isostasy can significantly influence sequence preservation on such margins

plate tectonics and aspherical earth structure the importance of poloidal toroidal coupling we derive poloidal flow internal loading green functions for incompressible fluid models of the mantle consisting either of a single constant viscosity spherical shell or of two adjacent spherical shells having different viscosities from the green function we obtain kernels connecting the surface divergence the geoid and the surface topography fields to the lateral density heterogeneity inferred on the basis of the application of seismic tomographic imaging techniques and with these kernels we argue that both the surface divergence and geoid fields consisting of harmonic degrees 2 5 may be reasonably fit with only a factor of 8 viscosity increase at a depth of 1200 km we point out however that the coupling from poloidal to toroidal flow which is required to understand surface velocity spectra may allow these observations to be understood in terms of a viscosity increase at depth which is smaller than required by nonhydrostatic geoid data in the context of pure poloidal models using the observed kinetic energy in the surface plate motions as a constraint allows us to infer a value for the steady state upper mantle viscosity of 2 0 0 5 1021 pa s we comment on the implication of the difference between this number and the somewhat lower value 1 1021 pa s which has been derived on the basis of analyses of signatures of the glacial isostatic adjustment process

global sea level trend in the past century data derived from tide gauge stations throughout the world indicate that the mean sea level rose by about 12 centimeters in the past century the sea level change has a high correlation with the trend of global surface air temperature a large part of the sea level rise can be accounted for in terms of the thermal expansion of the upper layers of the ocean the results also represent weak indirect evidence for a net melting of the continental ice sheets

glacial isostatic adjustment and the free air gravity anomaly as a constraint on deep mantle viscosity summary a gravitationally self consistent theory for relative sea level variations forced by pleistocene deglaciation events is employed to explore the extent to which rsl and free air gravity observations together constrain the viscosity of the mantle beneath the seismic discontinuity at 670 km depth a trade off is revealed between errors in the assumed deglaciation history and errors in the inferred value of the viscosity of the lower mantle taking full account of such uncertainty plausible values of the viscosity beneath the transition region are bounded above by 1023 poise cgs units the preferred value is at least a factor of 2 lower than this and is strongly constrained by the observed free air gravity anomaly over hudson bay the calculations described in detail here show for the first time that the relatively large gravity anomalies observed over sites of wurm wisconsin deglaciation do not require any pronounced increase of mantle viscosity with depth in order to explain them

vertical gradient correction for the oceanographic atlas of the east asian seas regional climatology around the east asian seas has been developed by an international collaboration between the national oceanic data center and the korea oceanic data center it provides reliable information on temperature and salinity climatological fields with high resolution 0 1 0 1 by 137 levels however there is a problem around near bottom areas where topographic change is steep and observations are not available near the bottom this study resolves this problem using a vertical gradient correction method when the profile is statically unstable the stability is determined based on the brunt vaisala frequency with individual temperature and salinity profiles topographic following mapping technique employing the potential vorticity constraint term is used to construct a vertical gradient database for the temperature and salinity at every grid point the results show that the correction is effective for eliminating large erroneous vertical gradients around near bottom areas in addition we show the importance of the optimal length scale to construct a precise vertical gradient database in a particular area such as the northern shelf of taiwan we expect that our revised high resolution climatological mean fields will serve as important data for relevant studies around the east asian seas

calibration of the c 14 timescale over the past 30 000 years using mass spectrometric u th ages from barbados corals uranium thorium ages obtained by mass spectrometry from corals raised off the island of barbados confirm the high precision of this technique over at least the past 30 000 years comparison of the u th ages with 14c ages obtained on the holocene samples shows that the u th ages are accurate because they accord with the dendrochronological calibration before 9 000 yr bp the 14c ages are systematically younger than the u th ages with a maximum difference of 3 500 yr at 20 000 yrbp the u th technique thus provides a way of calibrating the radiocarbon timescale beyond the range of dendrochronological calibration

two types of el nino events cold tongue el nino and warm pool el nino abstract in this study two types of el nino events are classified based on spatial patterns of the sea surface temperature sst anomaly one is the cold tongue ct el nino which can be regarded as the conventional el nino and the other the warm pool wp el nino the ct el nino is characterized by relatively large sst anomalies in the nino 3 region 5 s 5 n 150 90 w while the wp el nino is associated with sst anomalies mostly confined to the nino 4 region 5 s 5 n 160 e 150 w in addition spatial patterns of many atmospheric and oceanic variables are also distinctively different for the two types of el nino events furthermore the difference in the transition mechanism between the two types of el nino is clearly identified that is the discharge process of the equatorial heat content associated with the wp el nino is not efficient owing to the spatial structure of sst anomaly as a result it cannot trigger a cold event it is also demonstrated that zonal advective feedback i e zonal adve

mantle convection and core mantle boundary topography explanations and implications abstract recent seismic inferences of the topography on the core mantle boundary cmb constitute a new and potentially important constraint on the dynamics of the thermal convective circulation in the earth s mantle we employ viscous flow models for the mantle to predict the flow induced deflections of the cmb that are expected on the basis of seismic tomographic inferences of internal mantle density heterogeneity the good agreement between our theoretical predictions and the seismically inferred cmb deflections of morelli and dziewonski 1987 suggests that the latter may indeed be good approximations to the dynamically induced cmb topography the amplitude of the seismically inferred cmb topography may be construed to provide a direct constraint on the temperature derivative of seismic p wave velocity in the lower mantle and we determine a value for this parameter in the course of fitting the data that differs significantly from the value determined by laboratory measurements as appropriate for upper mantle phases the seismically observed topography on the cmb is also shown to provide evidence favouring the whole mantle convection hypothesis and in this connection we argue that deep penetration of subducted lithospheric slabs into the lower mantle is likely to be responsible for controlling many of the features of this topography

subducted slabs and the geoid constraints on mantle rheology and flow geoid anomalies are primarily the result of the density contrasts driving mantle convection and plate motion the total geoid anomaly resulting from a given density contrast in a convecting earth is affected by the mass anomalies associated with the flow induced deformation of the upper surface and internal compositional boundaries as well as by the density contrast itself these boundary deformations and hence the total gravity field depend on the radial distribution of effective viscosity if the internal density contrasts can be estimated as is the case for subducted slabs useful constraints can be placed on the depth and on the variation of viscosity with depth of the convecting system the degree 4 9 components of the observed long wavelength geoid are highly correlated with those predicted by a density model for seismically active subducted slabs the positive sign of the correlation requires that the effective viscosity increases with depth by a factor of 30 or more the amplitude of the correlation cannot be explained by the density contrasts associated with just the seismically active parts of subducted slabs however the amplitude can be explained if the density contrasts associated with subduction extend into the lower mantle or if old lithosphere is piled up at the base of the upper mantle beneath subduction zones to a thickness in excess of 350 km over horizontal distances of thousands of kilometers mantlewide convection in a mantle that has a viscosity increasing with depth provides a simple explanation of the long wavelength geoid anomalies over subduction zones

induced stresses and fault potential in eastern canada due to a realistic load a preliminary analysis summary in order to understand the causal relation between postglacial rebound and earthquakes a simple disc load model is used to 1 calculate stresses induced in the lithosphere and mantle by glacial loading melting and postglacial rebound and 2 evaluate the effect of glacial loading rebound on the failure potential for earthquakes in the upper crust the dependence of the failure potential and the actual mode of failure on the coefficient of friction the ambient tectonic stress magnitude direction the stress due to the overlying rocks and lithospheric thickness are investigated prominent features of this paper are the inclusion of 1 a viscoelastic mantle and thus the migration of stress and 2 the ambient tectonic stress and overburden stress contributions in the calculation of the total stress field it is assumed that throughout the earth there are optimally oriented pre existing virtual faults that are initially close to but not at failure thus a time dependent quantity called dfsm related to the coulomb mohr failure criterion can be defined such that a negative value of dfsm would advocate faulting or earthquake activities whereas a positive value of dfsm would promote stability the results indicate that under all combinations of tectonic stress magnitude and overburden stress crustal loading promotes fault stability directly underneath the load upon the removal of the load thrust faulting is predicted within the ice margin if the horizontal stress s induced by the overburden is greater than or equal to the vertical component s of the overburden stress 121 where sjs under this condition theory predicts that faulting or earthquake activity should have reached a maximum immediately after deglaciation if the horizontal stress induced by the overburden is less than the vertical component of the overburden stress 1 l then theory predicts fault stability within the ice margin the theory predicts fault instability both north and south of the ice margin the mode of failure however is completely determined by the value of i the trade off between the tectonic stress magnitude and the overburden stress parameter 1 is also investigated it is shown that a larger tectonic stress magnitude can be used to compensate a smaller value of 1 the results of this analysis show that variations in the coefficient of friction lithospheric thickness and a ductile zone below the upper crust do not significantly affect the above conclusions

will earthquake activity in eastern canada increase in the next few thousand years knowledge of whether earthquake activity will increase in the next few thousand years is important for the planning of nuclear waste repositories assuming that fault instability portends earthquak

ice 3g a new global model of late pleistocene deglaciation based upon geophysical predictions of post glacial relative sea level change a new high resolution global model of late pleistocene deglaciation is inferred on the basis of geophysical predictions of postglacial relative sea level variations in which the ice ocean solid earth interaction is treated in a gravitationally self consistent fashion for the purpose of these analyses the radial viscoelastic structure of the planet is assumed known on the basis of previously published sensitivity tests on solutions of the forward problem only radiocarbon controlled relative sea level histories from sites that were actually ice covered with one or two additions are employed to constrain the model leaving relative sea level rsl data from sites that were not ice covered to be employed to confirm its consistency results for these confirmatory analyses are reported elsewhere here the new deglaciation model referred to as ice 3g is compared to previous models derived by several independent means and tested against a number of additional observations other than sea level histories including geologically controlled retreat isochrones oxygen isotope data from deep sea sedimentary cores and coral terrace elevations the latter two observations strongly constrain the net sea level rise that has occurred since the onset of deglaciation and therefore the mass of ice that melted during the last glacial interglacial transition

the influence of a finite glaciation phase on predictions of post glacial isostatic adjustment we predict relative sea level rsl variations present day three dimensional 3d crustal deformation rates and baseline velocities and a set of anomalies in the gravitational field of the planet using a suite of models for the space time geometry of the pleistocene ice sheets these models are distinguished on the basis of the details of the glaciation phase and they include the cases of an infinite glaciation phase i e an assumption of isostatic equilibrium at the time of the last glacial maximum lgm a steady uniform glaciation and a glaciation in which the bulk of the accumulation is limited to the final stages of the growth phase comparison of the observational records of postglacial rsl change with predictions based on the assumption of isostatic equilibrium at lgm have commonly been used to infer both the space time geometry of the final deglaciation event and the mantle viscosity we conclude that both these applications may be influenced significantly by the incorporation of a finite glacial cycle as an example rsl predictions which assume isostatic equilibrium at lgm and those which incorporate a relatively rapid glaciation phase can differ by a factor of 2 or more at some sites within previously glaciated regions when an earth model characterized by a lower mantle viscosity of 1022 pa s is adopted we have also found that differences in the adopted model for the glaciation event are capable of explaining entirely the discrepancies 0 2 mm yr between previously published predictions of present day tangential velocities in north america these discrepancies are characterized by a dominant long wavelength signal and hence they do not necessarily influence strongly predictions of baseline velocities variations in the glaciation model can also have an important effect on predictions of peak gravity anomalies over previously glaciated regions and secular variations in the zonal harmonics of the earth s geoid in both cases the effect may be sufficient to alter significantly the signal from other geophysical processes which may need to be invoked to reconcile the observational constraints

aerial magnetic mapping with an unmanned aerial vehicle and a fluxgate magnetometer a new method for rapid mapping and upscaling from the field to regional scale abstract magnetic measurements with an unmanned aerial vehicle are ideal for filling the gap between ground and airborne magnetic surveying however to obtain accurate aeromagnetic data the compensation of magnetic effects of the unmanned aerial vehicle is a challenge typically scalar magnetometers are towed several metres under the unmanned aerial vehicle to minimize its magnetic field in this study a fluxgate three component magnetometer is attached 42 cm in front of the unmanned aerial vehicle at the tip of a composite pipe using a scalar calibration the sensor can be calibrated and the permanent and induced magnetic fields of the unmanned aerial vehicle can be compensated the contributions of the magnetic measurements at different altitudes to the unmanned aerial vehicle results were tested over an area of 1 km in the northern vosges mountains the area is located in a hamlet surrounded by a forest where few geological outcrops are observed three magnetic surveys of the same area are obtained at different altitudes 100 30 and 1 m above the ground the unmanned aerial vehicle magnetic data are compared with a helicopter aeromagnetic survey at 300 m above the ground and a ground magnetic survey using upward continuations of the maps to compare the results the magnetic maps 300 100 30 and 1 m above the ground show very different magnetic anomaly patterns e g amplitude shape wavelength and orientation the magnetic data at different altitudes improve the understanding of the geology from the local to more general scales

glacial isostatic adjustment and the anomalous tide gauge record of eastern north america sea level variations as recorded by the global network of tide gauges represent a rich data set for studying a wide range of natural and anthropogenic phenomena such as the sea level rise induced by possible global warming for this purpose long term sea level trends must be corrected for the contaminating effects of continuing glacial isostatic adjustment1 5 gia the numerical correction procedure has for sites on the east coast of north america yielded a set of highly anomalous sea level rates characterized by systematic geographical trends2 4 5 we demonstrate that these trends are a consequence of inadequacies in the previous standard numerical prediction for gia in particular we find that the well known trends in the gia corrected tide gauge rates are eliminated if the lower mantle viscosity of the earth model used in the gia prediction is increased this result obviates the need to explain the anomalous trend as a manifestation of gulf stream ocean circulation4 or neotectonic processes2

the last glaciation of marvin peninsula northern ellesmere island high arctic canada the limit of the last glaciation on marvin peninsula northernmost ellesmere island is recorded by extensive ice marginal landforms and early holocene glaciomarine sediments while glaciers occupied most valleys on the peninsula other areas remained ice free as did most of the adjacent fiords beyond the ice limit sparse erratics and degraded meltwater channels within weathered bedrock are evidence of older more extensive glaciation s shorelines and marine shells 50 m above the limit of the holocene sea along the north coast relate to these older glacial events thirty four new radiocarbon dates provide a chronology of ice buildup and retreat glaciers reached their limit after 23 ka and locally as late as 11 ka this was achieved by both expansion of existing glaciers and accumulation on plateau and lowland sites which are presently ice free late wisconsinan climate was characterized by cold and extreme aridity five dates ranging from 11 to 31 ka bp on subfossil bryophytes suggest that ice free

lithospheric thickness antarctic deglaciation history and ocean basin discretization effects in a global model of postglacial sea level change a summary of some sources of nonuniqueness the global model of postglacial relative sea level variations that has been developed over the past decade is employed to investigate the constraints that it may be invoked to place on the timing of the deglaciation of west antarctica the analyses presented here confirm the suggestion of p wu and w r peltier 1983 geophysical journal of the royal astronomical society74 377 450 that the model of this event employed inj a clark and c s lingle 1979quaternary research11 279 298 may be simply modified to rectify the misfits between theory and observation that are otherwise obtained at southern hemisphere sites a large number of southern hemisphere relative sea level data are shown to require that the retreat of antarctic ice substantially lagged the retreat of northern hemisphere ice if the deglaciation of antarctica was abrupt the time of onset of antarctic deglaciation is thereby shown to coincide with the time of most rapid northern hemisphere deglaciation sensitivity tests are performed which demonstrate that this result is relatively insensitive to the discretization employed to represent the ocean basins the only exception to this general rule obtains at some coastal sites at which a trade off is revealed between the delay of west antarctic melting and the thickness of the lithosphere required to reconcile the observed local variations of relative sea level at such sites which are all in the far field of the ice sheets some attention must be paid to the accuracy of the local finite element representation of the oceans and to the details of the antarctic deglaciation history

el nino modoki and its possible teleconnection 1 using observed data sets mainly for the period 1979 2005 we find that anomalous warming events different from conventional el nino events occur in the central equatorial pacific this unique warming in the central equatorial pacific associated with a horseshoe pattern is flanked by a colder sea surface temperature anomaly ssta on both sides along the equator empirical orthogonal function eof analysis of monthly tropical pacific ssta shows that these events are represented by the second mode that explains 12 of the variance since a majority of such events are not part of el nino evolution the phenomenon is named as el nino modoki pseudo el nino modoki is a classical japanese word which means a similar but different thing the el nino modoki involves ocean atmosphere coupled processes which include a unique tripolar sea level pressure pattern during the evolution analogous to the southern oscillation in the case of el nino hence the total entity is named as el nino southern oscillation enso modoki the enso modoki events significantly influence the temperature and precipitation over many parts of the globe depending on the season the impacts over regions such as the far east including japan new zealand western coast of united states etc are opposite to those of the conventional enso the difference maps between the two periods of 1979 2004 and 1958 1978 for various oceanic atmospheric variables suggest that the recent weakening of equatorial easterlies related to weakened zonal sea surface temperature gradient led to more flattening of the thermocline this appears to be a cause of more frequent and persistent occurrence of the enso modoki event during recent decades

global glacial isostasy and the surface of the ice age earth the ice 5g vm2 model and grace abstract the 100 kyr quasiperiodic variation of continental ice cover which has been a persistent feature of climate system evolution throughout the most recent 900 kyr of earth history has occurred as a consequence of changes in the seasonal insolation regime forced by the influence of gravitational n body effects in the solar system on the geometry of earth s orbit around the sun the impacts of the changing surface ice load upon both earth s shape and gravitational field as well as upon sea level history have come to be measurable using a variety of geological and geophysical techniques these observations are invertible to obtain useful information on both the internal viscoelastic structure of the solid earth and on the detailed spatiotemporal characteristics of glaciation history this review focuses upon the most recent advances that have been achieved in each of these areas advances that have proven to be central to the construction of the refined model of the global process of glacial isos

crustal block movements from holocene shorelines crete and antikythira greece abstract marks of several shorelines left by sea level stands during the last 4000 yrs occur along the coasts of the islands of crete and antikythira in this area recent movements of the earth s crust were identified by using a systematic survey based on multidisciplinary analyses strengthened by 60 radiometric datings between 4000 and 1700 yr b p a block of lithosphere a about 150 km long fig 10 which included antikythira and the levka mountains in crete underwent a series of ten rapid subsidences from 10 to 25 cm each time without noticeable tilting these movements ended about 1 530 40 yr b p a further block of lithosphere b approximately 200 km long was then uplifted about 10 m and inclined northeastwards in a single event block b includes block a and extends 50 km further eastwards beyond the ida mountains as far as the iraklion sedimentary basin the tectonic movements were preceded by vertically reversed displacements of short duration on at least three occasions if the a block subsidences can be ascribed to gravitational forces then the b block uplift suggests a cause that originated at depth crustal consumption and elastic rebound to the east of the ierapetra graben the sitian peninsula appears to belong to a block of lithosphere c affected by a northeast tilting and separated by an active fault from the crustal block of khrisi koufonisi

isostatic adjustments in a full glacial sea during the last glaciation an ice free corridor existed between the northeast ellesmere island and northwest greenland ice sheets this corridor constituted a peripheral depression in which the marine limit marks the uppermost extent of a full glacial sea the full glacial sea is characterized by 1 14c dates on in situ marine shells that predate initial emergence unloading followed by 2 synchronous emergence from the marine limit throughout the peripheral depression relative sea level curves from the full glacial sea confirm previous morphostratigraphic and glacioisostatic evidence for limited ice extent during the last glaciation these curves also document the history of glacial unloading and the form of the relative sea level curve that one would theoretically expect in the peripheral depression the form of the curves presented here is unlike any other published emergence curves from arctic canada or from fennoscandia the relative sea level curves for northeast ellesmere island show three segme

sea level change in the irish sea since the last glacial maximum constraints from isostatic modelling models of glacio hydroisostatic sea level change have been published for the british isles that are broadly consistent with the observational evidence as well as with glaciological constraints it has been argued however that the models fail to represent sea level change along the irish sea margins and in southern ireland for the post deglaciation period the argument rests on the interpretation of the depositional environment of the elevated irish sea drift on both sides of the irish sea whether this is terrestrial or glaciomarine the isostatic models for the british isles are consistent with the former interpretation in that sea levels on either side of the irish sea south of about the isle of man are not predicted to have risen above present sea level at any time since the deglaciation of the irish sea this implies that ice over both the irish sea and ireland was relatively thin ca 600 700 m over ireland if the glaciomarine interpretation of the elevated irish sea drift is correct then the maximum ice thickness over central and southern ireland would have to reach 2000 m exceeding that over scotland furthermore for the resulting sea level change to be consistent with the holocene evidence this thick ice sheet could not have extended to the eastern side of the irish sea nor could it have been very thick at its northern and western limits if such an ice model is extreme and incompatible with glaciological observations then the alternative is to accept the interpretation of the irish sea drift as terrestrial in origin copyright 2001 john wiley sons ltd