propagation of signals in basin scale ocean bottom pressure from a barotropic model 1 the exchange of atmospheric plus oceanic mass between ocean basins is investigated using a global barotropic ocean model we find two particular cases of exchange between two basins at periods of 4 6 days the exchange is between the atlantic and pacific basins and represents a known oscillation forced by atmospheric pressure this mode represents a failure of the inverse barometer relationship due to the large scale and high frequency of atmospheric forcing and the presence of continents significant exchange between atlantic and pacific also occurs at longer periods the second case is most prominent at periods longer than 30 days strongest at periods longer than 100 days and represents a mass exchange between the southern ocean and the pacific the southern ocean part of this exchange is clearly related to the southern mode of fluctuations in antarctic circumpolar transport forced by southern ocean wind stress the reason for the exchange being with the pacific rather than other basins is explored and is found to be related to the balance of wind stress by form stress in drake passage exchange with the atlantic and indian oceans becomes dominant if drake passage topography is removed while recognizing the limitations of a barotropic model we contend that it is necessary to understand the barotropic adjustment process in order to make sense of longer timescale processes accordingly we end with speculation on the possible importance of the barotropic results for global sea level and tropical dynamics

variations in the age of arctic sea ice and summer sea ice extent 1 three of the past six summers have exhibited record low sea ice extent on the arctic ocean these minima may have been dynamically induced by changes in the surface winds based on results of a simple model that keeps track of the age of ice as it moves about on the arctic ocean we show that the areal coverage of thick multi year ice decreased precipitously during 1989 1990 when the arctic oscillation was in an extreme high index state and has remained low since that time under these conditions younger thinner ice anomalies recirculate back to the alaskan coast more quickly decreasing the time that new ice has to ridge and thicken before returning for another melt season during the 2002 and 2003 summers this anomalously younger thinner ice was advected into alaskan coastal waters where extensive melting was observed even though temperatures were locally colder than normal the age of sea ice explains more than half of the variance in summer sea ice extent

arctic ocean circulation patterns revealed by grace abstractmeasurements of ocean bottom pressure obp anomalies from the satellite mission gravity recovery and climate experiment grace complemented by information from two ocean models are used to investigate the variations and distribution of the arctic ocean mass from 2002 through 2011 the forcing and dynamics associated with the observed obp changes are explored major findings are the identification of three primary temporal spatial modes of obp variability at monthly to interannual time scales with the following characteristics mode 1 50 of the variance is a wintertime basin coherent arctic mass change forced by southerly winds through fram strait and to a lesser extent through bering strait these winds generate northward geostrophic current anomalies that increase the mass in the arctic ocean mode 2 20 reveals a mass change along the siberian shelves driven by surface ekman transport and associated with the arctic oscillation mode 3 10 reveals a mass dipole with mass decreasing

seasonal variations in the west spitsbergen current estimated from bottom pressure measurements from 1982 to 1985 two pressure gauges were deployed across the continental shelf northwest of spitsbergen to determine the seasonal variations in the barotropic component of the west spitsbergen current the variation in current velocity was calculated after analysis and removal of the tidal signals and correction of the pressure difference across the 47 km section for bottom buoyancy effects the pressure derived velocity fluctuates about 10 cm s 1 peak to peak with the maximum northward flow occurring in the winter the maximum appears to the correlated with the seasonal cycle of wind stress curl in the northern greenland sea in fact the magnitude of the velocity variation corresponds to the sverdrup transport due to the fluctuation in wind stress curl at 79 n 7 5 e the idea that the observed variation might also be due to the spin up of the basin by wind stress curl is explored with two simple analytical models basin spin up does appear to be a possible cause however east greenland current velocity data from muench et al 1986 indicate that the fluctuation about the mean in the deep currents on the western side of the basin is northward in winter while basin spin up would produce a southward fluctuation this supports the idea that sverdrup transport dominates basin spin up at least at the margins of the basin the fluctuations in transport and heat flux though the pressure gauge section are estimated to be 2 sv and 30 to 60 tw peak to peak these values are major fractions of historical estimates of the mean transport and heat flux values in the west spitsbergen current and they are significant fractions of the total oceanic fluxes into the arctic ocean this suggests that long time series are required to make meaningful estimates of the heat budget of the arctic

post processing removal of correlated errors in grace data 1 gravity fields produced by the gravity recovery and climate experiment grace satellite mission require smoothing to reduce the effects of errors present in short wavelength components as the smoothing radius decreases these errors manifest themselves in maps of surface mass variability as long linear features generally oriented north to south i e stripes the presence of stripes implies correlations in the gravity field coefficients here we examine the spectral signature of these correlated errors and present a method to remove them finally we apply the filter to a model of surface mass variability to show that the filter has relatively little degradation of the underlying geophysical signals we seek to recover

contributions of geoarchaeology and remote sensing to the study of holocene hunter gatherer and agro pastoral groups in arid margins the case of north gujarat northwest india the present work aims at setting the bases for the critical study of settlement patterns and resource management among holocene hunter gatherer and agro pastoral groups in arid margins the case study is set on the sw margin of the thar desert in n gujarat an ecotone sensitive to the slightest shifts in precipitation patterns indian summer monsoon the potential significance of published and newly acquired archaeological information is discussed in the light of physiographical data collected from satellite imagery and field exploration the review of available and newly acquired records includes a the integration of field and remote observation of regional traits and b the definition of active morphological processes that may bias archaeological preservation and visibility a synthetic geoarchaeological map of the study area is proposed that integrates physiographical and archaeological evidence at the regional scale the potential significance of the archaeological evidence in the region i e presence absence concentration of archaeological materials in different physiographical units is discussed in terms of preservation and visibility at this stage results are considered at the regional level of macroscopic units the results constitute the first step towards the full multi scalar integration of landscape architectures stratified archaeological sites and surface sediments at regional and local levels

arctic sea ice variability revisited this paper explores spatial and temporal relationships between variations in arctic sea ice concentration summer and winter and near surface atmospheric temperature and atmospheric pressure using multivariate statistical techniques trend empirical orthogonal function eof and singular value decomposition svd analyses are used to identify spatial patterns associated with covariances and correlations between these fields results show that 1 in winter the arctic oscillation still explains most of the variability in sea ice concentration from 1979 to 2006 and 2 in summer a decreasing sea ice trend centered in the pacific sector of the arctic basin is clearly correlated to an arctic wide air temperature warming trend these results demonstrate the applicability of multivariate methods and in particular svd analysis which has not been used in earlier studies for assessment of changes in the arctic sea ice cover results are consistent with the interpretation that a warming signal has now emerged from the noise in the arctic sea ice record during summer our analysis indicates that such a signal may also be forthcoming during winter

modeling global sea ice with a thickness and enthalpy distribution model in generalized curvilinear coordinates abstract a parallel ocean and ice model poim in generalized orthogonal curvilinear coordinates has been developed for global climate studies the poim couples the parallel ocean program pop with a 12 category thickness and enthalpy distribution ted sea ice model although the poim aims at modeling the global ocean and sea ice system the focus of this study is on the presentation implementation and evaluation of the ted sea ice model in a generalized coordinate system the ted sea ice model is a dynamic thermodynamic model that also explicitly simulates sea ice ridging using a viscous plastic rheology the ted model is formulated such that all the metric terms in generalized curvilinear coordinates are retained following the pop s structure for parallel computation the ted model is designed to be run on a variety of computer architectures parallel serial or vector when run on a computer cluster with 10 parallel processors the parallel performance of the poim is close to that of a correspon

nonseasonal fluctuations of the arctic ocean mass observed by the grace satellites 1 time variable gravity observations from the grace satellites reveal strong nonseasonal fluctuations of bottom pressure in the arctic ocean on the time scales from 2 to 6 months and a record high bottom pressure anomaly in february of 2011 here we examine the nature and driving forces behind those fluctuations we find that the nonseasonal variability of the arctic ocean mass is strongly coupled to wind forcing the zonal wind pattern is correlated with a dipole pattern of arctic ocean mass changes westerly wind intensification over the north atlantic at about 60 n as well as over the russian arctic continental shelf break cause the ocean mass to decrease in the nordic seas and in the central arctic and to increase over the russian arctic shelf basin wide arctic ocean mass fluctuations are correlated with northward wind anomalies over the northeastern north atlantic and nordic seas and over the bering sea we show that positive negative arctic ocean mass anomalies are associated with anticyclonic cyclonic anomalies of the large scale ocean circulation pattern based on ocean model simulations we conclude that the observed nonseasonal arctic ocean mass variability is mostly explained by the net horizontal wind driven transports and the contribution of fresh water fluxes is negligible we demonstrate that transport anomalies across both the atlantic and pacific gateways were equally important for generating large arctic ocean mass anomalies in 2011

sea surface height and dynamic topography of the ice covered oceans from cryosat 2 2011 2014 we examine 4 years 2011 2014 of sea surface heights ssh from cryosat 2 cs 2 over the ice covered arctic and southern oceans results are from a procedure that identifies and determines the heights of sea surface returns along 25 km segments of satellite ground tracks variability in the retrieved sshs is between 2 and 3 cm standard deviation in the arctic and is slightly higher 3 cm in the summer and the southern ocean average sea surface tilts along these 25 km segments are 0 01 3 8 cm 10 km in the arctic and slightly lower 0 01 2 0 cm 10 km in the southern ocean intra seasonal variability of cs 2 dynamic ocean topography dot in the ice covered arctic is nearly twice as high as that of the southern ocean in the arctic we find a correlation of 0 92 between 3 years of dot and dynamic heights dh from hydrographic stations further correlation of 4 years of area averaged cs 2 dot near the north pole with time variable ocean bottom pressure from a pressure gauge and from grace yields coefficients of 0 83 and 0 77 with corresponding differences of 3 cm rms these comparisons contrast the length scale of baroclinic and barotropic features and reveal the smaller amplitude barotropic signals in the arctic ocean broadly the mean dot from cs 2 for both poles compares well with those from the icesat campaigns and the dot2008a and dtu13mdt fields short length scale topographic variations due to oceanographic signals and geoid residuals are especially prominent in the arctic basin but less so in the southern ocean

boundary wave communication of bottom pressure and overturning changes for the north atlantic 1 the relationship between changes in sea surface height bottom pressure and overturning is explored using isopycnal model experiments for the north atlantic changes in high latitude forcing are communicated rapidly over the basin through boundary wave propagation along the continental slope involving a hybrid mixture of kelvin and topographic rossby waves as well as spreading more slowly through advection along the western boundary this wave communication leads to coherent signals in sea surface height and bottom pressure variability extending for several thousand kilometers along the continental slope the model results are in broad agreement with altimetric diagnostics and the patterns only alter in detail with the realism of the topography the adjustment in bottom pressure is directly linked to a change in overturning since west east contrasts in bottom pressure are associated with a zonal integral in the meridional geostrophic flow correlation patterns reveal that temporal changes in overturning are primarily connected to the vertical contrast in bottom pressure across the shelf and continental slope along the western boundary

the role of summer surface wind anomalies in the summer arctic sea ice extent in 2010 and 2011 1 strong summertime anticyclonic wind anomalies over the arctic ocean with anomalous flow toward the fram strait during summer months of 2007 contributed to the record low the arctic sea ice extent observed in september of that year had the summer winds over the arctic during the summers of 2010 and 2011 been the same as those in 2007 september sea ice extent would have reached new record lows in those years as well by regulating the flow of ice toward and through the fram strait variations in low level winds over the arctic have contributed to the month to month year to year and decade to decade variability of sea ice extent

multitemporal analysis for preservation of obsidian sources from melka kunture ethiopia integration of fieldwork activities digital aerial photogrammetry and multispectral stereo ikonos ii analysis abstract an integrated analysis of recent satellite imageries and dated aerial photos demonstrated to be a good investigation tool gallo et al 2009 for the identification of new sites and for the assessment of landscape changes of wide archaeological areas in ethiopia in the melka kunture archaeological sequence the obsidian exploitation represents a leitmotiv during the last 1 7 myr and the first known example of oldowan utilization piperno et al 2009 the primary nearest obsidian source the site of balchit 7 km north from melka kunture is a dome flow dated to 4 37 0 07 myr chernet et al 1998 large areas of the balchit site are covered by secondary obsidian debris resulting from the erosion of primary sources the proximity between primary and secondary balchit obsidian sources and the high quality of this raw material easily available in large quantity represent a unique condition in the framework of the oldowan and acheulian east african sites piperno et al 2009 in order to evaluate the human impact on the multitemporal change of obsidian sources the land use of the study area following the corine land cover nomenclature has been classified from aerial photos and ikonos ii imageries respectively dated to 1972 and 2006 the accurate positioning of the primary and secondary sources and their extent have been measured thanks to the multispectral characteristics and to the high spatial resolution of the available imageries satellite scenes covering an area of about 100 km 2 have been also utilized in stereoscopy for the creation of the new topographic map at the scale of 1 10 000 and of the digital elevation model dem images orientation has been performed through the use of rational polynomial coefficients rpc which accuracy has been improved by the availability of ground control points gcps properly measured during a dgps survey then the images have been orthorectified and radiometrically and spectrally enhanced in order to favour the recognition of obsidian presence in respect with ground observations collected during fieldworks photointerpretation and semi automatic classification processes of images have been performed with the support of spectral signatures of obsidian samples recorded by a fieldspec pro spectroradiometer ranging in the visible short wave infrared electromagnetic interval 0 4 2 5 m

dynamic topography of the ice covered arctic ocean from icesat 1 we construct the dynamic ocean topography dot of the arctic ocean for five icesat campaigns winter of 2004 2008 using sea surface height estimates in open leads results show that the mean winter dot over the arctic ocean varies by 1 m and features a distinct dome of 40 cm over the beaufort sea standard deviation of the mean field is 20 cm spatial coherence between the five winter dots is consistently high 0 9 whereas the coherence between the dots and the winter djfm sea level pressure fields over the arctic basin is variable this suggests persistence of the underlying hydrodynamic processes at interannual time scales compared to seasonal atmospheric forcing comparison of dynamic heights dh from hydrographic surveys and the dot in 2008 shows a remarkable correlation of 0 92 the geostrophic velocity fields computed from the dot and interpolated dh fields highlight the smaller scale oceanographic features in the satellite estimates

enhancing rescue archaeology using geomorphological approaches archaeological sites in paredes asturias nw spain abstract palaeolithic remnants a necropolis roman villa and another minor archaeological site were discovered in paredes spain these sites were the focus of multidisciplinary research during the construction of a large shopping centre in asturias nw spain the aims of this study are 1 to contribute to archaeological prospection in the sites and 2 to develop evolutionary models of the sites based on geomorphological inferences detailed archaeological prospection 103 trenches geomorphologic mapping stratigraphic studies 36 logs and ground penetration radar gpr surveys on five profiles indicate that the location of the settlement source of the necropolis is outside the construction perimeter farther to the southeast the pre holocene evolution of the fluvial landscape is marked by the development of two terraces t1 and t2 that host the early palaeolithic remains in the area ca 128 71 ka the holocene evolution of the landscape was marked by the emplacement of the nora river flood plain covered by alluvial fans after ca 9 ka bp cal bc 8252 7787 subsequently neolithic pebble pits dated ca 5 3 ka bp cal bc 4261 3963 and 4372 4051 were constructed on t2 at the area reoccupied as a necropolis during the late roman period 1590 45 years bp cal ad 382 576 coeval human activity during the late roman period at 1670 60 years bp cal ad 320 430 is also recorded by channel infill sediments in a minor site at the margin of an alluvial fan located to the southeast this work shows that a rescue archaeological study can be significantly enhanced by the implementation of multidisciplinary scientific studies in which the holistic view of geomorphologic settings provide key insights into the geometry and evolution of archaeological sites

investigation of past archaeological landscapes using remote sensing and gis a multi method case study from mount ida crete spatial analysis in geoarchaeological applications can be improved by implementing a wider set of geoecological parameters in order to provide more precise results the aim of the paper is to show how geoscientific ground truth and techniques can be adopted for detailed archaeological studies using a comprehensive set of environmental variables that might have influenced ancient settlement patterns the project focuses on spatial patterns of archaeological sites as well as bronze age communication paths in central crete by applying a multi method approach surveying remote sensing dem analysis least cost analysis candidate site detection predictive modelling etc in contrast to conventional archaeological gis applications this enhanced strategy offers promising prospects regarding landscape and settlement modelling

evaluation of new grace time variable gravity data over the ocean 1 monthly grace gravity field models from the three science processing centers csr gfz and jpl are analyzed for the period from february 2003 to april 2005 over the ocean the data are used to estimate maps of the mass component of sea level at smoothing radii of 500 km and 750 km in addition to using new gravity field models a filter has been applied to estimate and remove systematic errors in the coefficients that cause erroneous patterns in the maps of equivalent water level the filter is described and its effects are discussed the grace maps have been evaluated using a residual analysis with maps of altimeter sea level from jason 1 corrected for steric variations using the world ocean atlas 2001 monthly climatology the mean uncertainty of grace maps determined from an average of data from all 3 processing centers is estimated to be less than 1 8 cm rms at 750 km smoothing and 2 4 cm at 500 km smoothing which is better than was found previously using the first generation grace gravity fields

relation between sea level and bottom pressure and the vertical dependence of oceanic variability 1 the relation between large scale sea level and bottom pressure variability is studied using long 50 yr simulations of a general circulation model under realistic forcing admittance and coherence analyses are used to characterize the bottom pressure and sea level relationship as a function of period horizontal spatial scale and location at the model grid scale 1 bottom pressure is found to be essentially equivalent to sea level at periods 60 and in shallow depths 200 m elsewhere bottom pressure and sea level fields can differ significantly results indicate an increase of the importance of baroclinic signals with decreasing latitude and spatial scale with significant baroclinic signals at intra seasonal and longer periods present in many subtropical and mid latitude regions variability is clearly baroclinic at inter annual periods regardless of location and spatial scale results have broad implications for the interpretation and processing of both satellite altimetry and gravity data and for their assimilation into numerical models

time variability of the earth s gravity field hydrological and oceanic effects and their possible detection using grace the grace satellite mission scheduled for launch in 2001 is designed to map out the earth s gravity field to high accuracy every 2 4 weeks over a nominal lifetime of 5 years changes in the gravity field are caused by the redistribution of mass within the earth and on or above its surface grace will thus be able to constrain processes that involve mass redistribution in this paper we use output from hydrological oceanographic and atmospheric models to estimate the variability in the gravity field i e in the geoid due to those sources we develop a method for constructing surface mass estimates from the grace gravity coefficients we show the results of simulations where we use synthetic grace gravity data constructed by combining estimated geophysical signals and simulated grace measurement errors to attempt to recover hydrological and oceanographic signals we show that grace may be able to recover changes in continental water storage and in seafloor pressure at scales of a few hundred kilometers and larger and at timescales of a few weeks and longer with accuracies approaching 2 mm in water thickness over land and 0 1 mbar or better in seafloor pressure

detection of exposed and subsurface archaeological remains using multi sensor remote sensing abstract multi sensor airborne remote sensing has been applied to the itanos area of eastern crete to assess its potential for locating exposed and known buried archaeological remains and to delineate subsurface remains beyond the current limits of ground geophysical data in order to permit future targeted geophysical surveys and archaeological excavations a range of processing techniques e g reed xiaoli anomaly detection have been applied to the casi atm and lidar data in order to detect anomalies based on the premise that buried remains are likely to alter the physical and chemical characteristics of the soil compared with those of the surroundings due to variations in soil depth and drainage through a combination of casi atm and lidar data surface remains have been classified and mapped effectively using an object oriented approach the detection of subsurface remains is more problematic however the thermal data is most promising in this respect the value of capturing multi or hyperspectral data at a high spatial resolution has been demonstrated as well as the additional benefits of combining these with airborne lidar

a diagnostic ice ocean model abstract a coupled ice ocean model suitable for simulating ice ocean circulation over a seasonal cycle is developed by coupling the dynamic thermodynamic sea ice model of hibler with a multilevel baroclinic ocean model bryan this model is used to investigate the effect of ocean circulation on seasonal sea ice simulations by carrying out a simulation of the arctic greenland and norwegian seas the ocean model contains a linear term that damps the ocean s temperature and salinity towards climatology the damping term was chosen to have a three year relaxation time equivalent to the adjustment time of the pack ice no damping however was applied to the uppermost layer of the ocean model which is in direct contact with the moving pack ice this damping procedure allows seasonal and shorter time scale variability to be simulated in the ocean but does not allow the model to drift away from ocean climatology on longer time scales for the standard experiment an initial integration of five years was per

comparison of in situ bottom pressure data with grace gravimetry in the crozet kerguelen region two time series of deep ocean bottom pressure records bprs in between the crozet islands and kerguelen are compared with grace gravity recovery and climate experiment equivalent water heights an analysis of the correlation is performed for four time series 1 monthly averages of the equivalent water height at the crozet islands 2 the same near the kerguelen islands 3 the mean of the two preceding series and 4 the difference between the two locations expressed in terms of geostrophic transport we find that smoothed grace solutions are strongly correlated with the bpr data with correlation coefficients in the order of 0 7 0 8 consequently grace measures real oceanic mass variations in this region

a basin coherent mode of sub monthly variability in arctic ocean bottom pressure 1 a sub monthly mode of non tidal variability of ocean bottom pressure obp is observed in a 5 year record of deep sea bottom pressure at the north pole obp records from other regions in the arctic show that the north pole non tidal mass fluctuation is part of a non propagating basin coherent variation that is well represented by the ice ocean model piomas with a basin averaged winter only rms of 3 3 cm wavelet analysis of the modeled obp shows that the basin averaged mass variations are non stationary and only significant during the winter the basin averaged obp is strongly related to the meridional wind component over the nordic seas the ocean response is consistent with episodic wind forcing driving a northward geostrophic slope current the mass transport anomaly associated with the mode is significant relative to the annual net mean flow

radiogenic isotopic compositions of low concentration dust and aerosol from the gisp2 ice core abstract we have produced a record of radiogenic isotope compositions of particulate and soluble dust fractions from the gisp2 ice core from basal ice to the surface for each respective dust fraction we measured sr and nd isotope values to constrain the provenance of mineral dust and sea salt aerosol transported to the greenland ice sheet we have produced high precision measurements of end values on sub ng quantities of nd in ice core samples via tims with 1013 ohm resistors the range of measured end values of soluble material 12 9 2 6 to 7 3 0 9 is interpreted to represent sea salt aerosol based on sr isotope compositions that resemble seawater values 0 711007 0 000030 to 0 709416 0 000072 therefore the end potentially provides important insights to the atmospheric circulation patterns at high latitudes at least through mis 5 we compare end values of surface seawater from ocean basins and deltas at high latitudes to alternating relatively radiogenic and unradiogenic end at gisp2 we suggest these changes represent transitions between a climate system dominated by enhanced and persistent arctic oscillation positive anomalies as determined from sea level and ocean bottom pressure measurements and a state representative of modern atmospheric circulation which typically exhibits either negative anomalies or none altogether

nonseasonal mass fluctuations in the midlatitude north atlantic ocean measurements from the gravity recovery and climate experiment reveal spatially coherent nonseasonal fluctuations in bottom pressure pb in the midlatitude north atlantic ocean the spatial structure of the pb anomalies is centered on the north atlantic current along the intergyre region separating subtropical and subpolar ocean basins and their temporal behavior is tied to indices of climate variability namely the north atlantic oscillation and the arctic oscillation correspondence to variations in wind stress curl suggests an interpretation of the midlatitude north atlantic pb variability in terms of a barotropic sverdrup balance anomalous mass in the midlatitude north atlantic ocean covaries with mass anomalies in abutting marginal seas including the mediterranean sea and the arctic ocean as well as the north sea and hudson bay results have implications for diagnosing ocean meridional heat transports due to depth independent gyre circulation changes

arctic ice ocean simulation with optimized model parameters approach and assessment 1 we present an optimized 1992 2008 coupled ice ocean simulation of the arctic ocean a green s function approach adjusts a set of parameters for best model data agreement overall model data differences are reduced by 45 the optimized simulation reproduces the negative trends in ice extent in the satellite records volume and thickness distributions are comparable to those from the ice cloud and land elevation satellite 2003 2008 the upper cold halocline is consistent with observations in the western arctic the freshwater budget of the arctic ocean and volume heat transports of pacific and atlantic waters across major passages are comparable with observation based estimates we note that the optimized parameters depend on the selected atmospheric forcing the use of the 25 year japanese reanalysis results in sea ice albedos that are consistent with field observations simulated pacific water enters the bering strait and flows off the chukchi shelf along four distinct channels this water takes 5 10 years to exit the arctic ocean at the canadian arctic archipelago nares or fram straits atlantic water entering the fram strait flows eastward merges with the st ana trough inflow and splits into two branches at the southwest corner of the makarov basin one branch flows along lomonosov ridge back to fram strait the other enters the western arctic circulates cyclonically below the halocline and exits mainly through the nares and fram straits this work utilizes the record of available observations to obtain an arctic ocean simulation that is in agreement with observations both within and beyond the optimization period and that can be used for tracer and process studies

influence of bering strait flow and north atlantic circulation on glacial sea level changes sea level fluctuations of about 20 30m occurred throughout the last glacial period these fluctuations seem to have been derived primarily from changes in the volume of northern hemisphere ice sheets 1 3 and cannot be attributed solely to ice melt caused by varying solar radiation 4 here we use a fully coupled climate model to show that the transport of relatively fresh pacific water into the north atlantic ocean was limited when lower sea level restricted or closed the bering strait resulting in saltier north atlantic surface waters this invigorated deep convection in the north atlantic ocean strengthening meridional overturning circulation and northward heat transport in our model which consequently promoted melting of ice sheets in north america and europe our simulations show that the associated sea level rise led to a reopening of the bering strait the flux of relatively fresh water into the north atlantic ocean muted meridional overturning circulation and led to cooling and ice sheet advance in the northern hemisphere we conclude that the repetition of this cycle could produce the sea level changes that have been observed throughout the last glacial cycle

decline in arctic sea ice thickness from submarine and icesat records 1958 2008 1 the decline of sea ice thickness in the arctic ocean from icesat 2003 2008 is placed in the context of estimates from 42 years of submarine records 1958 2000 described by rothrock et al 1999 2008 while the earlier 1999 work provides a longer historical record of the regional changes the latter offers a more refined analysis over a sizable portion of the arctic ocean supported by a much stronger and richer data set within the data release area dra of declassified submarine sonar measurements covering 38 of the arctic ocean the overall mean winter thickness of 3 64 m in 1980 can be compared to a 1 89 m mean during the last winter of the icesat record an astonishing decrease of 1 75 m in thickness between 1975 and 2000 the steepest rate of decrease is 0 08 m yr in 1990 compared to a slightly higher winter summer rate of 0 10 0 20 m yr in the five year icesat record 2003 2008 prior to 1997 ice extent in the dra was 90 during the summer minimum this can be contrasted to the gradual decrease in the early 2000s followed by an abrupt drop to 55 during the record setting minimum in 2007 this combined analysis shows a long term trend of sea ice thinning over submarine and icesat records that span five decades

ocean dynamics associated with rapid j2 fluctuations importance of circumpolar modes and identification of a coherent arctic mode 1 fluctuations of the earth s dynamic oblateness j2 are a measure of global redistributions of mass between equatorial and polar regions sensitive to the component which is symmetric about the equator cox and chao recently published a time series of monthly values of j2 based on satellite orbit determination which showed rapid fluctuations from month to month as well as a large change in j2 in 1997 1998 we here investigate the ocean dynamics associated with these rapid fluctuations using a barotropic ocean model forced by atmospheric wind stress and pressure we find that the model has significant skill in reproducing the observations though not the change in 1997 1998 much of the model variability is related to coherent circumpolar fluctuations in arctic and antarctic bottom pressure which despite their apparent symmetry are forced by quite different mechanisms the antarctic mode is forced by circumpolar winds whereas the arctic mode is forced by northward winds over the entrances to the polar sea comparison with in situ observations shows that the model has skill in reproducing the polar modes arctic tide gauge records confirm the presence of a coherent mode at short periods and at long periods over at least the eurasian arctic shelf if barotropic and representative of the whole arctic this would be large enough to make a major contribution to measured j2 fluctuations but does not account for the 1997 1998 event

do the north atlantic winds drive the nonseasonal variability of the arctic ocean sea level the gravity recovery and climate experiment grace satellites have observed coherent and nearly uniform nonseasonal fluctuations of bottom pressure throughout the arctic ocean and the nordic seas strong correlation between the nonseasonal grace and satellite altimetry data is found in the nordic and barents seas which suggests a possibility of using the longer altimetry records in these areas as a proxy for the nonseasonal sea level variability over the entire arctic this study identifies the dominant pattern of the nonseasonal atmospheric pressure variability that drives strong zonal wind anomalies over the northeastern north atlantic associated with the nonseasonal sea level anomalies in the nordic seas our results show that wind driven northward ekman transport anomalies in the northeastern north atlantic may induce coherent changes of sea level across the entire arctic ocean

the spatial distribution of palaeolithic human settlements and its influence on palaeoecological studies a case from northern iberia the aim of this study is to assess the influence of human site location choice on biogeographical and paleoecological studies based on archaeological remains through a case study in north western spain data from an exhaustive literature survey and field trips were managed with gis and subjected to statistical analyses the results show that the influence of the different variables shifted through the palaeolithic although certain general preferences can be seen low altitudes median 151 m a s l south facing surfaces generally gentle slopes median 13 and moderate distances to water courses median 297 m these choices were conditioned by geomorphological factors with lgm glacier extent imposing an upper limit in the range of occupied altitudes and marine and fluvial terraces conditioning site location patterns the results suggest that human site location patterns during the palaeolithic were not random conditioning the information available from archaeological remains our results allow us to identify some key areas where information on past faunal distributions and more generally on biocoenoses will be scarce or missing

the relationship between sea level and bottom pressure variability in an eddy permitting ocean model we investigate the relationship between sea level after application of an inverse barometer correction and ocean bottom pressure in an eddy permitting ocean model we find the presence of eddies can disrupt this relationship even on timescales as short as 10 20 days but only in the regions of most energetic eddy variability away from eddies the relationship is similar to that seen in a coarserresolution model with a tight relationship between sea level and bottom pressure at high frequencies but with significant correlations between sea level and bottom pressure at interannual timescales seen only in shelf sea regions in the deep ocean regions where sea level and bottom pressure remain related out to the longest timescales are in the arctic ocean and regions of the southern ocean where particularly large amplitude barotropic fluctuations are found but where the mesoscale signal is weak

molecular composition of a leaf and root bearing oligocene oxbow lake clay in the weisselster basin germany abstract a plant fossil bearing clay profile from the upper oligocene thierbach strata weisselster basin germany has been sectioned into horizons and the plant macrofossils of each section surface have been identified by morphological and anatomical studies in the upper half of the profile leaves from populus germanica and carpinus grandis and branchlets from the conifer taxodium balticum vel t dubium dominate the horizons while the lower part contains only root remains of unknown higher plants in the soxhlet extracted samples from each section n alkanes n alkanols n carboxylic acids and several terpenoids amyrin 24 25 dinoreleana 1 3 5 10 12 tetraene olean 12 en 3 one simonellite and hop 17 21 ene were identified by combined gas chromatography mass spectrometry the comparison of the extracted chemical compounds and the macrofossil record of the profile shows that simonellite occurs preferentially in the taxodium bearing horizons n alkanes n alkanols n carboxylic acids and amyrin were found in all sections but are enriched in the root containing part of the profile the distribution of hop 17 21 ene is independent of the input of higher plant remains

response of sea ice to the arctic oscillation abstract data collected by the international arctic buoy programme from 1979 to 1998 are analyzed to obtain statistics of sea level pressure slp and sea ice motion sim the annual and seasonal mean fields agree with those obtained in previous studies of arctic climatology the data show a 3 hpa decrease in decadal mean slp over the central arctic ocean between 1979 88 and 1989 98 this decrease in slp drives a cyclonic trend in sim which resembles the structure of the arctic oscillation ao regression maps of sim during the wintertime january march ao index show 1 an increase in ice advection away from the coast of the east siberian and laptev seas which should have the effect of producing more new thin ice in the coastal flaw leads 2 a decrease in ice advection from the western arctic into the eastern arctic and 3 a slight increase in ice advection out of the arctic through fram strait taken together these changes suggest that at least part of the thinning of sea ice recently observed ov

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

a meteoric water budget for the arctic ocean a budget of meteoric water mw river runoff net precipitation minus evaporation and glacial meltwater over four regions of the arctic ocean is constructed using a simple box model regional precipitation evaporation estimates from reanalysis data sets and estimates of import and export fluxes derived from the literature with a focus on the 2003 2008 period the budget indicates an approximate slightly positive balance between mw imports and exports i e no change in storage thus the observed total freshwater increase observed during this time period likely resulted primarily from changes in non mw freshwater components i e increases in sea ice melt or pacific water and or a decrease in ice export further our analysis indicates that the mw increase observed in the canada basin resulted from a spatial redistribution of mw over the arctic ocean mean residence times for mw were estimated for the western arctic 5 7 years eastern arctic 3 4 years and lincoln sea 1 2 years the mw content over the siberian shelves was estimated 14 000 km3 based on a residence time of 3 5 years the mw content over the entire arctic ocean was estimated to be 44 000 km3 the mw export through fram strait consisted mostly of water from the eastern arctic 3 237 1 370 km3 yr 1 whereas the export through the canadian archipelago was nearly equally derived from both the western arctic 1 182 534 km3 yr 1 and lincoln sea 972 391 km3 yr 1

retreat of the cold halocline layer in the arctic ocean we present a comparison of arctic ocean hydrographic data sets from the 1990s with a focus on changes in the upper few hundred meters of the eurasian basin the most recent observations discussed here were collected during the spring 1995 scientific ice expedition scicex 95 the second in a series of scientific cruises to the arctic ocean aboard u s navy nuclear submarines although the 1990s have seen an abundance of synoptic cruises to the arctic this was the only one to take place in winter spring conditions other data considered here were collected during the first scicex cruise in summer 1993 scicex 93 and during an icebreaker cruise to the eurasian basin in summer 1991 oden 91 a new russian american winter climatology is also used as a reference these comparisons reveal that the eurasian basin cold halocline layer has retreated during the 1990s to cover significantly less area than in previous years specifically we find a retreat from the amundsen basin back into the makarov basin the latter is the only region with a true cold halocline layer during scicex 95 changes are also seen in other halocline types and in the atlantic water layer heat content and depth since the cold halocline layer insulates the surface layer and thus the overlying sea ice from the heat contained in the atlantic water layer this should have profound effects on the surface energy and mass balance of sea ice in this region using a simple mixing model we calculate maximum ice ocean heat fluxes of 1 3 w m 2 in the eurasian basin where during scicex 95 the surface layer lay in direct contact with the underlying atlantic water layer the overall cause of water mass changes in the 1990s might have been a shift in the atmospheric wind forcing and resulting sea ice motion during the late 1980s which we speculate influenced the location where fresh shelf waters flow into the deeper basins of the arctic ocean finally we discuss two different mechanisms that have been proposed for cold halocline water formation and we propose a compromise that best fits these data

ocean mass variations from grace and tsunami gauges 1 we compared the mass variations from gravity recovery and climate experiment grace with those measured by bottom pressure recorders bprs deployed as tsunami gauges prior to the comparison we estimated the degree 1 stokes coefficients by the degree 1 loading method using both the gps and grace data we successfully recovered the degree 1 stokes coefficients that are consistent with those from the satellite laser ranging analysis and from the loading model we found that the use of the grace data in the degree 1 loading method significantly mitigates the aliasing effect from the unmodeled higher degree loading deformations then we compared the mass variations from grace with those from the five bprs that have been deployed as part of the deep ocean assessment and reporting of tsunamis dart system we observed a fairly good over 0 4 correlation except for one station that is close to the u s mainland however we found that the grace derived mass variations underestimate those from bprs by nearly a factor of 2 through numerical simulation we found that the artificial leakage from the landmass is responsible for the low correlation observed at the station and the spatial averaging in the grace processing may be responsible for the underestimation of the mass variations from bprs by grace these results illustrate the importance of performing a simulation for these effects with numerical models before comparing the grace derived mass variations with those from pointwise measurements

wintertime variability of the beaufort gyre in the arctic ocean derived from cryosat 2 siral observations we processed the sea surface height measured by the sar synthetic aperture radar interferometric radar altimeter siral on board cryosat 2 cs 2 and successfully estimated the monthly dynamic ocean topography dot of the arctic ocean the cs 2 monthly dot showed the interannual and monthly variability of the beaufort gyre bg during winter between 2010 2011 and 2014 2015 the northward flow at the western edge of the bg was primarily estimated over the chukchi borderland cbl however the bg extended across the cbl and the northward flow was estimated over the mendeleev ridge in the winter of 2012 2013 our analyses revealed a significantly variable bg in response to changes in the sea surface stress field our analysis indicated that 1 sea ice motion driven by wind fields acts as a driving force for the bg when sea ice motion was intensified during winter and 2 sea ice motion can also act as an inhibiting force for the bg when sea ice motion is weakened during winter in addition the relationship between the dot steric height and ocean bottom pressure implied that the dot during winter responded to varying wind stresses through baroclinic and barotropic adjustments according to a tracer experiment we inferred that in the winter of 2012 2013 the pacific origin water carried into the bg through the barrow canyon was transported to the northern shelf and shelf break of the chukchi sea rather than the cbl which is where the pacific origin water had been transported in the other years of the observation period

low frequency exchange of mass between ocean basins 1 we examine the gravity recovery and climate experiment grace data and output from an ocean model to quantify mass fluctuations for the pacific atlantic and indian ocean basins from august 2002 until december 2008 the monthly spatial mean is removed to study interbasin mass exchange we find a seasonal exchange of mass between the atlantic and pacific that is similar to one documented previously although the amplitude observed by grace is about 20 lower than that simulated by an ocean model there are also significant fluctuations with periods longer than 1 year we find large interannual exchanges in 2005 and 2007 with grace observing yearly averaged mass anomalies in the pacific that are about 30 40 larger than simulated by a model this is shown to be from significant interannual mass losses from the indian ocean that are observed by grace but not simulated by the model a longer run of the model from 1976 to 2008 suggests that such interbasin mass exchanges are a regular occurrence and can last for as long as a couple of decades

karst depressions as geoarchaeological archives the palaeoenvironmental reconstruction of zominthos central crete based on geophysical prospection sedimentological investigations and gis abstract sediment filled karst depressions e g dolines have rarely been used as geoarchives in greece due to an uncertainty about the thickness of accumulations and their vague suitability for palaeoenvironmental research however such terrestrial proxy data sources can yield important records for the analysis of the holocene landscape history a multi method approach was applied in order to evaluate the potential of colluvial fillings for reconstructing the geoarchaeological landscape in mount ida central crete subsequent to an area wide survey of appropriate karst hollows through remote sensing and gis analyses geophysical prospection refraction seismics earth resistivity tomography was conducted at the most promising archive locations selective percussion drilling within the sinkholes provided vibra cores for mineralogical and sedimentological investigations grain size distribution heavy and light minerals x ray diffraction thin sections as well as ams 14 c dates as demonstrated by the results the dolines are partially filled by loose material up to 20 m b s and thus offer valuable information about the environmental history the diversified sediment constitution indicates several geomorphodynamic oscillations and a polygenetic nature of the colluvial fills xrd spectra of clay minerals and quartz grain morphology both indicate a significant aeolian dust contribution to soil formation and pedo sediments glass shards and substantially heterogeneous heavy mineral compositions point to supra regional origin and external volcanogenic deposits minoan eruption of santorini 3 6 ka regarding the hitherto discussed distribution of z2 tephra in the mediterranean the spatial fallout must be revised as great amounts have also been deposited in the high mountains of crete moreover the redeposition of the sedimentary fills proves to be comparatively young since most materials were accumulated within the dolines post eruptively huge and previously unknown subsurface archaeological remains strongly suggest that year around settlement in the mid holocene might have been possible under better climatic conditions the results imply that karst depressions serve as suitable geoarchives particularly when investigated within a multi method approach

relaxation of central arctic ocean hydrography to pre 1990s climatology 1 upper ocean hydrography in the central arctic ocean has relaxed since 2000 to near climatological conditions that pertained before the dramatic changes of the 1990s the behavior of the anomalies of temperature and salinity in the central arctic ocean follow a first order linear response to the ao with time constant of 5 years and a delay of 3 years

circulation of summer pacific halocline water in the arctic ocean 1 we present an analysis of arctic ocean hydrographic and sea ice observations from the 1990s with a focus on the circulation of water that originates in the north pacific ocean previous studies have shown the presence of two varieties of relatively warm summer halocline water in the vicinity of the chukchi sea i e the relatively fresh alaskan coastal water acw and the relatively saltier summer bering sea water sbsw here we extend these studies by tracing the circulation of these waters downstream into the arctic ocean we find that acw is generally most evident in the southern beaufort gyre while sbsw is strongest in the northern portion of the beaufort gyre and along the transpolar drift stream we find that this separation is most extreme during the early mid 1990s when the arctic oscillation was at historically high index values this leads us to speculate that the outflow to the north atlantic ocean through the canadian archipelago and fram strait may be similarly separated as arctic oscillation index values fell during the later 1990s acw and sbsw began to overlap in their regions of influence these changes are evident in the area north of ellesmere island where the influence of sbsw is highly correlated with a 3 year lag with the arctic oscillation index we also note the presence of winter bering sea water wbsw which underlies the summer varieties all together this brings the number of distinct pacific water types in our arctic ocean inventory to three acw sbsw and wbsw

recent trends in arctic ocean mass distribution revealed by grace 1 measurements of ocean bottom pressure by the gravity recovery and climate experiment grace and new in situ bottom pressure measurements confirm the accuracy and utility of grace measurements in the arctic ocean they reveal a declining trend in bottom pressure that corresponds to mass changes due to decreasing upper ocean salinities near the north pole and in the makarov basin the spatial distribution and magnitude of these trends suggest the arctic ocean is reverting from the cyclonic state characterizing the 1990s to the anticyclonic state that was prevalent prior to the 1990s

the arctic oscillation signature in the wintertime geopotential height and temperature fields the leading empirical orthogonal function of the wintertime sea level pressure field is more strongly coupled to surface air temperature fluctuations over the eurasian continent than the north atlantic oscillation nao it resembles the nao in many respects but its primary center of action covers more of the arctic giving it a more zonally symmetric appearance coupled to strong fluctuations at the 50 hpa level on the intraseasonal interannual and interdecadal time scales this arctic oscillation ao can be interpreted as the surface signature of modulations in the strength of the polar vortex aloft it is proposed that the zonally asymmetric surface air temperature and mid tropospheric circulation anomalies observed in association with the ao may be secondary baroclinic features induced by the land sea contrasts the same modal structure is mirrored in the pronounced trends in winter and springtime surface air temperature sea level pressure and 50 hpa height over the past 30 years parts of eurasia have warmed by as much as several k sea level pressure over parts of the arctic has fallen by 4 hpa and the core of the lower stratospheric polar vortex has cooled by several k these trends can be interpreted as the development of a systematic bias in one of the atmosphere s dominant naturally occurring modes of variability

shelfbreak current over the canadian beaufort sea continental slope wind driven events in january 2005 the shelfbreak current over the beaufort sea continental slope is known to be one of the most energetic features of the beaufort sea hydrography in january 2005 three oceanographic moorings deployed over the canadian eastern beaufort sea continental slope simultaneously recorded two consecutive shelfbreak current events with along slope eastward bottom intensified flow up to 120 cm s 1 both events were generated by the local wind forcing associated with two pacific born cyclones passing north of the beaufort sea continental slope toward the canadian archipelago over the mooring array the associated westerly wind exceeded 15 m s 1 these two cyclones generated storm surges along the beaufort sea coast with sea surface height ssh rising up to 1 4 m following the two westerly wind maxima we suggest that the westerly along slope wind generated a surface ekman onshore transport the associated ssh increase over the shelf produced a cross slope pressure gradient that drove an along slope eastward geostrophic current in the same direction as the wind this wind driven barotropic flow was superimposed on the background baroclinic bottom intensified shelfbreak current that consequently amplified summer fall satellite altimetry data for 1992 2013 show that the ssh gradient in the southeastern beaufort sea is enhanced over the upper continental slope in response to frequent storm surge events because the local wind forcing and or sea ice drift could not explain the reduction of sea ice concentration over the beaufort sea continental slope in january 2005 we speculate that wind driven sea level fluctuations may impact the sea ice cover in winter

combining digital elevation data srtm aster high resolution satellite imagery quickbird and gis for geomorphological mapping a multi component case study on mediterranean karst in central crete abstract remote sensing data have become more and more popular for geomorphological investigations because their steadily increasing level of detail and accessibility opens up new potentials in this context this paper examines the application and quality of digital elevation models srtm and aster dems high resolution satellite imagery quickbird and gis techniques for the detection and mapping of karst landforms mainly enclosed depressions at different scales in the ida mountains of central crete besides discussing methodological issues and evaluating suitability potentials we conducted an exemplary case study based on spatial analysis of the regional karst morphology different input datasets and processing methods are applied gis based analysis land cover classification raster calculations etc in order to carry out an area wide surveying and mapping of karst depressions the findings are supported and validated by auxiliary field studies due to the level of detail and occasional data errors an exclusive use of satellite imagery or digital elevation models for automatic karst landform detection performs insufficiently our results demonstrate that mapping karst features through remote sensing is significantly dependent on scale of interest existing environmental conditions and data quality a semi automatic data integration approach on the basis of digital datasets generated by combined satellite image processing and dem analysis yields the best results especially when indirect karst indicating variables like iron oxide rich sediments are included as detection criteria the multi component application presented in this paper provides a time saving and effective tool for meso to macro scale object detection and extensive study areas however the potential of fully automated karst feature mapping still needs to be explored in future work concerning the spatial dimension of karstification in central crete the gis based results allow differentiating further geomorphological characteristics e g by indicating a significant altitudinal change of karst forms within the study area size and shape of depressions dolines uvalas and poljes vary considerably due to the geological setting climatic impacts neotectonics and elevation

detection of archaeological crop marks by using satellite quickbird multispectral imagery abstract the capability of satellite quickbird imagery for the identification of archaeological crop marks is herein presented and discussed for two test sites located in the south of italy the selected sites dating back to middle ages were buried under surfaces covered by herbaceous plants characterized by a different phenological status dry green when the satellite data were acquired the methodological approach adopted for the enhancement and extraction of crop marks is mainly based on the use of data fusion and edge detection algorithm the main remarkable differences found for the two archaeological sites can be suitably linked to the different state of vegetation that caused a different spectral response in particular near infrared nir spectral channel was able to better enhance crop marks observed for dry vegetation whereas normalized difference vegetation index ndvi was found to be more capable to better enhance crop marks observed for green vegetation

beaufort gyre freshwater reservoir state and variability from observations 1 we investigate basin scale mechanisms regulating anomalies in freshwater content fwc in the beaufort gyre bg of the arctic ocean using historical observations and data collected in 2003 2007 specifically the mean annual cycle and interannual and decadal fwc variability are explored the major cause of the large fwc in the bg is the process of ekman pumping ep due to the arctic high anticyclonic circulation centered in the bg the mean seasonal cycle of liquid fwc is a result of interplay between the mechanical ep and thermal ice transformations factors and has two peaks one peak occurs around june july when the sea ice thickness reaches its minimum maximum ice melt the second maximum is observed in november january when wind curl is strongest maximum ep and the salt input from the growing ice has not yet reached its maximum interannual changes in fwc during 2003 2007 are characterized by a strong positive trend in the region varying by location with a maximum of approximately 170 cm a 1 in the center of ep influenced region decadal fwc variability in the period 1950 2000 is dominated by a significant change in the 1990s forced by an atmospheric circulation regime change the center of maximum fwc shifted to the southeast and appeared to contract in area relative to the pre 1990s climatology in spite of the areal reduction the spatially integrated fwc increased by over 1000 km 3 relative to climatology