a simple ice ocean model for the greenland sea abstract a steady coupled model of the upper ocean circulation and ice cover in a meridional channel is presented and applied to the greenland sea the main ocean gyre is driven by wind stress however a nonzero boundary condition on meridional velocity is applied at the western side to produce a southward flowing coastal current representative of the east greenland current egc to match the egc to the interior sverdrup solution a munk type western boundary layer is introduced the upper ocean temperature is governed by an advection diffusion equation which is forced at the boundaries and by heat exchange with the atmosphere the ice model is purely thermodynamic and the ice edge position is determined iteratively since the streamfunction and temperature fields depend on the ice cover and in turn the ice cover is determined by both the ocean and air temperature the range of behavior of the temperature field and ice edge position is studied as a function of the ice ocean drag the wind stress tra

atmospheric and depositional environments traced from unique chemical compositions of the snow over an inland high plateau antarctica surface snow samples from the inland high plateau east queen maud land antarctica show unique chemical characteristics they are characterized by high acidity accompanying the high electrical conductivity so that the hydrogen ion is the dominant ion coupling with chloride and nitrate ions the chemical composition differs sharply from sea salts these characteristics appear more clearly than previously reported in antarctica and are most strongly developed in snow samples from the high region the tritium content increases in the inland high area especially in the region higher than 3600 m asl above sea level which corresponds to the region where the effects of katabatic wind have vanished in the glaciological observations the highest tritium content occurs in the vertical profile at a snow pit 3761 m asl 77 00 s 35 00 e which corresponds to the snow deposition in 1966 the concentration is the highest ever reported in antarctica and is almost as high as the one observed in the precipitation in the inland region of north america which is the highest value ever reported in the world all the results suggest that most of the ions contained in snow samples from the inland high plateau especially higher than 3600 m asl are not brought directly through the troposphere from the sea around antarctica but from the higher atmosphere and that they are under the influence of the physicochemical reactions occurring there

changes of relative sea level during the past 5000 years in the ancient harbor of marseilles southern france in the ancient harbor of marseilles marine fauna fixed upon archaeological structures as well as bio sedimentary units document a 1 5 m steady rise in relative sea level during the past 5000 years followed by a near stable level at present datum from about 1500 years ad to the last century this trend is similar to the one previously documented along the rocky coasts of the same region field observations inside and outside the harbor confirm that no sea level stand higher than the present ever occurred during the studied period in contradiction with the numerical model of peltier but in agreement with the glacio hydro isostatic models of lambeck and johnston and lambeck and bard q 2001 elsevier science b v all rights reserved

a soil chronosequence study of the reno valley italy insights into the relative role of climate versus anthropogenic forcing on hillslope processes during the mid holocene abstract relatively few soil chronosequences with good age control exist for late pleistocene and holocene deposits in the mediterranean region of europe yet surface soils and their young buried counterparts can provide meaningful information about the timing and processes of landscape response to external forcing such as climate or anthropogenic change here we present the results of a study that examines a well dated chronosequence of nineteen soil exposures in surficial deposits ranging in age from hundreds of years to hundreds of thousands of years located in the reno river valley near bologna italy the soil forming climate of the reno valley sits on a threshold between that which facilitates the accumulation of caco 3 and that which facilitates the translocation and formation of clay minerals and iron oxides once formed secondary iron oxides are relatively immobile in oxidizing conditions in the soil profile and therefore consistently record age trends with feo fed ratios decreasing predictably with soil age for all soils in the chronosequence the morphology of secondary carbonate accumulation and its depth of leaching also vary predictably with soil age but only for soils younger than about 12 000 years in these young soils horizons that contain secondary carbonate progress from relatively shallow stage i bk horizons in late holocene aged soils to deeper stage iii bk horizons in latest pleistocene aged soils in soils older than approximately 12 000 cal ybp however carbonate dissolution during wetter climates and the addition of colluvium and or dust to terrace surfaces become important factors in the preservation of carbonate in the profile and carbonate content is not predictable by age alone without significant depositional additions these older soils become decalcified pedogenic carbonate precipitated during drier climates is susceptible to dissolution during wetter periods as evidenced by discontinuous carbonate coatings on grains in some soils therefore overall measurable pedogenic carbonate content is spatially and temporally variable as a function of input of fresh carbonate and locally controlled soil moisture conditions particle size does not decrease predictably with soil age for reno valley soils and appears to be strongly influenced by parent material variability in younger soils and by dust additions in older soils our detailed examination of soil stratigraphy in the reno valley revealed evidence of significant aggradation of colluvium and tributary fans in the middle holocene between 6000 and 4000 ybp this aggradation pre dates bronze age agricultural expansion and appears to be instead attributable to the climate conditions of the middle holocene that have been documented elsewhere in italy for this time period this study demonstrates that late pleistocene and holocene surface soils in the mediterranean region of europe can effectively help elucidate rates and processes of landscape evolution

mixing in the west spitsbergen current abstract twenty eight profiles of temperature and salinity down to 1 km depth have been measured in the area north from the coast of svalbard to latitude 84 40 n between 0 and 32 e longitude they show atlantic waters of the west spitsbergen current entering the arctic ocean in a bifilimentary mode one filament following the coastline and the other 300 km farther north apparently following the continental shelf break the profiles show these filaments mixing into the ambient water in a series of intrusive layers which are remarkably uniform over distances of hundreds of kilometers a triple peak structure at the atlantic water maximum is the dominant oceanographic characteristic of the area with salt fingering occurring on the upper surface of the cold intrusions and indications of double diffusive exchanges through the lower surface a system or eddies or meanders is postulated as the mechanism for the production of multiple fronts allowing the intrusive layers to extend to distances much greater t

the tiber river delta plain central italy coastal evolution and implications for the ancient ostia roman settlement geomorphologic stratigraphic faunistic palynological and carbon isotope analyses were carried out in the area of the tiber river mouth the results depict a complex palaeoenvironmental evolution

secular variation of northern hemisphere 50 kpa geopotential height abstract there is accumulating evidence in the literature that different short period climate regimes subclimates may have characterized the northern hemisphere during the past 40 years we therefore investigate the 40 yr record of 50 kpa height 1946 85 and analyze the time series of zonal anomalies stratified by season we find that there appears to be two contiguous regimes with a rather abrupt transition during the early 1960s which had significantly different means trends and degrees of variability the results are compared with those from recent investigations of northern hemisphere surface and or tropospheric temperature variation the possibility of a climatic jump during the early 1960s is discussed our results raise the question of an appropriate period to use for determining normals whether for standard level surfaces or more generally for calculating the statistics of the general circulation both in the horizontal and vertical

evidence for stability enhancement of sea ice in the greenland and labrador seas malmberg proposed in 1969 that anomalously low surface upper 200 m salinities in the iceland seas during the late 1960s could increase the stability of the water column sufficiently to prevent deep convection the increased stability would then enhance the formation of sea ice during winter in this region because even at the freezing point 1 8 c the surface water density is sufficiently low to prevent mixing with the water below hence only a small portion of the water column need be cooled before freezing can occur and ice formation is enhanced here we explore this concept further by examining hydrographic data from three locations bordering greenland and iceland and then compare these with colocated sea ice concentrations for the period 1953 1980 it is shown that the lag correlations between surface salinity and sea ice anomalies show a common structure for the case where salinity anomalies lead sea ice anomalies it is shown that this correlation structure can be reproduced by a simple statistical feedback model using a nonstationary negative feedback coefficient to account for salinity forcing of ice anomalies the data presented are all consistent with the concept of stability enhancement of sea ice formation

greenland sea convection in the winter of 1987 1988 during february 1988 a layer of almost uniform temperature and salinity between 100 and 1250 m depth was observed in the central greenland sea this feature indicative of previous deep convection is explained in terms of a conceptual penetrative convection model

a box model study of the greenland sea norwegian sea and arctic ocean we develop a simple dynamical system model of the arctic ocean and marginal seas by applying the martinson killworth and gordon box model of a high latitude two layer ocean to four regions connected together the greenland sea the norwegian sea the arctic ocean and the greenland gyre the latter is a small convective region embedded in the northwest corner of the norwegian sea the model for each region consists of a thermodynamic ice layer that covers two layers of saline water which can under specific conditions become statically unstable and hence create a state of active overturning the system is forced by monthly mean atmospheric temperatures in the four regions by continental runoffs and by inflows from adjacent oceans the model predicts the ice thickness and the temperature and salinity of the water in the upper layer of the four regions also determined are the water temperature and salinity of the lower layer in the arctic ocean box the convective state of any given region i e whether it is in an active overturning mode or not is also determined as a continuous function of time the different output variables of the model which are the response to climatological forcing conditions compare favourably with observed data in the control run the arctic ocean region is characterized by continuous ice cover the greenland sea and greenland gyre have ice cover only during winter and the norwegian sea region never forms an ice cover another feature of the control run is the winter time occurrence of convective overturning in the upper 200 m in the greenland gyre region the model is also used for different anomaly experiments a positive air temperature anomaly which represents a global warming of the earth a negative salt anomaly in the norwegian sea which simulates the great salinity anomaly of the 1960s and 1970s and an increase in the ice flux through fram strait which parameterizes anomalous ice production in the arctic

high resolution sequence stratigraphy from piezocone tests an example from the late quaternary deposits of the southeastern po plain abstract cone penetration tests are traditionally regarded as a major tool for geotechnical investigations this study based upon interpretation of 234 cone penetration tests with pore pressure measurements piezocone tests or cptu carried out in the late quaternary deposits of the southeastern po plain shows how cptu tests can also be used for sedimentological purposes including detailed facies characterization subsurface stratigraphic correlations and identification of the key surfaces for sequence stratigraphic interpretation the late quaternary depositional history of the southeastern po plain reconstructed on the basis of data from seventeen continuously cored boreholes includes 1 alluvial plain development during the late quaternary lowstand and the early stages of transgression 2 formation of a rapidly migrating barrier lagoon system during the late transgressive phases 8800 6000 y bp 3 construction and progradation of a wave dominated delta ancient po delta during the following sea level highstand 6000 800 y bp and 4 development of the present day alluvial plain following the delta lobe abandonment in the 13th century a d local execution of cptu tests in coincidence with drilling sites enables the calibration of borehole data with piezocone penetration profiles lithofacies characterization is based upon estimation of three major parameters corrected cone resistance q t sleeve friction f s and pore water pressure u plotting of q t versus the ratio of cone friction to cone bearing fr is adopted as the major tool for sediment texture classification eight major facies associations for the southeastern po plain are identified these are for decreasing q t values 1 fluvial channel sands 2 beach ridge sands 3 transgressive barrier sands 4 crevasse sands and silts 5 levee silts and sands 6 floodplain silts and clays 7 prodelta clays and 8 marsh clays and peats cptu profile interpretation also provides the basis for the identification of the three major key surfaces within the late quaternary 4th order depositional sequence 1 the transgressive surface ts marking the boundary between the locally pedogenized stiff pleistocene alluvial clays and the overlying holocene transgressive paralic deposits has a distinctive pore pressure response with very low u values and is characterized by a sharp downward increase in f s which is paralleled by a moderate increase in q t 2 the ravinement surface rs corresponding to the boundary between fine grained back barrier deposits and the overlying transgressive barrier sands is invariably marked by a sharp upward increase in q t and decrease in fr 3 the maximum flooding surface mfs which is not clearly recognizable on the sole basis of core data is identified within shallow marine prodelta clays in combination with minor peaks of q t which have been interpreted to reflect a laterally extensive fossil lag with transition in proximal areas to sand shell rich layers simplicity speed and comparatively low costs of cptu tests imply that an extensive use of this method when used in conjunction with core programs can be a very attractive alternative to economically less convenient methods for the geological mapping of alluvial coastal plain areas consisting of non gravel deposits

arctic contribution to upper ocean variability in the north atlantic abstract because much of the deep water of the world s oceans forms in the high latitude north atlantic the potential climatic leverage of salinity and temperature anomalies in this region is large substantial variations of sea ice have accompanied north atlantic salinity and temperature anomalies especially the extreme and long lived great salinity anomaly of the late 1960s and early 1970s atmospheric pressure data are used hem to show that the local forcing of high latitude north atlantic ocean fluctuations is augmented by antecedent atmospheric circulation anomalies over the central arctic these circulation anomalies are consistent with enhanced wind forcing of thicker older ice into the transpolar drift stream and an enhanced export of sea ice fresh water from the arctic into the greenland sea prior to major episodes of ice severity in the greenland and iceland seas an index of the pressure difference between southern greenland and the arctic asian coast reached its highest value of the twe

genetically related alluvial deposits across active fault zones an example of alluvial fan terrace correlation from the upper quaternary of the southern po basin italy integrated studies of alluvial fan systems and related intramontane valley deposits provide potentially useful tools for understanding the character of alluvial sedimentation and its control in fault controlled piedmont zones an example is reported from the uppermost quaternary alluvial deposits of the northern apennines and the southern margin of the po basin a distinctive cyclicity characterizes both the outcropping and the buried units in the study area in intramontane valleys individual cycles consist of regular alternations of sections displaying high and low terrace preservation in the subsurface a rhythmic alternation of coarse grained bodies and laterally extensive pelitic horizons occurs at various scales and represents the basic cyclic motif of the depositional system the correlation between the terrace sequences and the depositional cycles in the subsurface allows the differentiation of distinct sequences with a characteristic internal architecture in the lower part of sequences poorly preserved terrace deposits are laterally correlatable with alluvial fan gravel bodies whereas highly preserved terrace deposits are correlated laterally with predominantly floodplain sediments in the upper part of sequences reliable correlation lines have been constructed using 14c dating thrust tectonics and climate exerted a major control on sequence development deep valley excavation with subsequent low terrace preservation occurred in response to relief rejuvenation during successive thrusting events on the other hand decreasing erosion related to periods of minor tectonic activity led to terrace preservation in the intramontane valleys the coeval episodes of alluvial fan growth and abandonment recorded at the basin margin are interpreted to reflect changes in the efficiency of the drainage system due to variations of tectonic uplift in the adjacent areas alternating phases of deglaciation and renewed glaciation however are inferred to have played a major role in controlling the amount and type of sediment delivered to the alluvial fan complexes

comparison between instrumental observational and high resolution proxy sedimentary records of late holocene climatic change a discussion of possibilities abstract variability of the north atlantic region is a key factor in the workings of global climate changes related to orbital factors and to the thermohaline circulation thc occur on timescales ranging from 1000 to 100 000 years whereas subdecadal decadal and multidecadal trends are associated with changes in atmospheric circulation sea surface temperature sst and salinity long term changes are known only from proxies whereas shorter periodicities are identified in instrumental and other observational data between lies a range of less well known centennial periodicities too long to be recorded observationally and too short for all but the highest resolution proxy records such as tree rings atmospheric 14c and varved lake sediments numerous investigations of such periodicities involve comparisons between the proxy and the observational record however results depend on the length of the datasets being analysed the relative strength of the periodicities present whether data are stationary or non stationary the degree to which they have been smoothed in order to remove particular fluctuations and the methods of analysis employed ideally comparisons should be between datasets of equal length and of similar properties but these criteria are not always easy to fulfill a search for periodicities in a range of well known multidecadal datasets reveals that whilst some frequencies previously identified in the central england temperature cet record and in the koch sea ice index are statistically significant those found by several authors in the index of the north atlantic oscillation nao are not as the index approximates to white noise instead decadal periodicity of the nao described by several authors appears to be result of smoothing of the raw data periodicities of 6 1 33 9 and 213 years identified in a proxy record from laminated sediments from loch ness scotland appear respectively to be related to a subdecadal variations in sst and salinity in the north atlantic ocean b multidecadal interactions between the nao and the north atlantic thc and c a well known centennial solar periodicity

geoarchaeology the four dimensional 4d fluvial matrix and climatic causality abstract geoarchaeology is the application of geological and geomorphological techniques to archaeology and the study of the interactions of hominins with the natural environment at a variety of temporal and spatial scales geoarchaeology in the uk over the last twenty years has flourished largely because it has gone beyond technological and scientific applications over the same period our ability to reconstruct the 3 dimensional stratigraphy of fluvial deposits and the matrix of fluvial sites has increased dramatically because of a number of technological advances these have included the use of lidar laser imaging and radar to produce high resolution digital surface models the use of geophysics particularly ground penetrating radar and electrical resistivity to produce sediment depth models and the use of gis and data visualisation techniques to manipulate and display the data these techniques along with more systematic and detailed sedimentological recording of exposed sections have allowed the construction of more precise 3 dimensional volumetric models of the matrix of artefacts within fluvial deposits additionally a revolution in dating techniques particularly direct sediment dating by luminescence methods has enabled the creation of 4 dimensional models of the creation and preservation of these sites these 4 dimensional models have the ability to provide far more information about the processes of site creation preservation and even destruction and also allow the integration of these processes with independent data sources concerning cultural evolution and climatic change all improvements in the precision of dating fluvial deposits have archaeological importance in our need to translate events from a sequential or geological timeframe to human timescales this allows geoarchaeology to make a more direct contribution to cultural history through the recognition of agency at the individual or group level this data can then form a component of biocomplexity or agent based modelling which is becoming increasingly used in the natural sciences particularly ecology and geomorphology and which can be used to test scenarios including the impact on and response of hominins to abrupt or catastrophic environmental change whilst catastrophic events clearly represent the atypical they can be illuminating in revealing cognitive processes resulting in abandonment coping mitigation and innovation these points are exemplified using two in depth case studies one from the holocene geoarchaeological record of the river trent in central england and the other from the palaeolithic record from rivers in south west britain in the former the interaction between climate change and human activity is illustrated at the year to century timescale whilst in the other the timescale is millennial these case studies have deliberately been chosen to be as different as possible in temporal and spatial scale with the aim of examining the applicability of methodological and theoretical aspects of geoarchaeology lastly the paper considers the problem of scale in geoarchaeology and concludes it is process dependency which ultimately affects the questions we can ask and that questions of human response to climate change are fundamentally a product of materiality and cognitive processes this demands an in depth contextual approach to such questions rather than database driven assertions of causality

climatology and variability of historical soviet snow depth data some new perspectives in snow indian monsoon teleconnections this study presents the monthly climatology and variability of the historical soviet snow depth data this data set was developed under the bilateral data exchange agreement between united states of america and the former union of soviet socialist republics the original data is for 284 stations for periods varying from 1881 upto 1985 the seasonal cycle of the mean snow depth has been presented both as spatial maps and as averages over key locations the deepest snow 80 cms day areas are found over siberia in particular over 80 100 e 55 70 n during march over the course of the annual cycle average snow depth over this region changes dramatically from about 10 cms in october to about 80 cms in march the variability is presented in the form of spatial maps of standard deviation to investigate the interaction of snow depth with indian monsoon rainfall imr lag and lead correlation coefficients are computed results reveal that the winter time snow depth over western eurasia surrounding moscow eastern eurasia in central siberia shows significant negative positive relationship with subsequent imr following the monsoon the signs of relationship reverse over both the regions this correlation structure is indicative of a midlatitude longwave pattern with an anomalous ridge trough over asia during the winter prior to a strong weak monsoon as the time progresses from winter to spring the coherent areas of significant relationship show southeastward propagation empirical orthogonal function analysis of the snow depth reveal that the first mode describes a dipole type structure with one centre around moscow and the other over central siberia depicting similar pattern as the spatial correlation structure the decadal scale imr variations seem to be more associated with the northern hemisphere midlatitude snow depth variations rather than with the tropical enso el nino southern oscillation variability

regional analysis of northern hemisphere 50 kpa geopotential heights from 1946 to 1985 abstract in knox et al the interannual variation of the northern hemisphere 50 kpa geopotential height field averaged between 30 and 80 n was investigated for the 40 year period from 1946 to 1985 we presented strong statistical evidence supporting the notion that a rather abrupt transition in the climate system took place during the early 1960s there was no attempt to compare the spatial distribution of the 50 kpa height difference between regime 1 1946 62 and regime 2 1963 85 as a sequel to the first paper we investigate the spatial characteristics of the transition height field we find that the difference in the 50 kpa height field between regime 1 and regime 2 is characterized by low frequency circulation modes of the pacific north american pna teleconnection pattern the north atlantic oscillation nao and an arctic oscillation there was an increase in the residual sense of the frequency and amplitude of the positive phase of the pna in regime 2 relative to regime 1 fourier analysi

sea ice anomalies observed in the greenland and labrador seas during 1901 1984 and their relation to an interdecadal arctic climate cycle two independent ice data sets from the greenland and labrador seas have been analyzed for the purpose of characterizing interannual and decadal time scale sea ice extent anomalies during this century sea ice concentration data for the 1953 1984 period revealed the presence of a large positive anomaly in the greenland sea during the 1960s which coincided with the great salinity anomaly an upper ocean low salinity water mass that was observed to travel cyclonically around the northern north atlantic during 1968 1982 this ice anomaly as well as several smaller ones propagated into the labrador sea and then across to the labrador and east newfoundland coast over a period of 3 to 5 years a complex empirical orthogonal function analysis of the same data also confirmed this propagation phenomenon an inverse relation between sea ice and salinity anomalies in the greenland labrador sea region was also generally found an analysis of spring and summer ice limit data obtained from danish meteorological institute charts for the period 1901 1956 indicated the presence of heavy ice conditions i e positive ice anomalies in the greenland sea during 1902 1920 and in the late 1940s and generally negative ice anomalies during the 1920s and 1930s only limited evidence of the propagation of greenland sea ice anomalies into the labrador sea was observed however probably because the data were from the ice melt seasons on the other hand several large ice anomalies in the greenland sea occurred 2 3 years after large runoffs in the early 1930s and the late 1940s from northern canada into the western arctic ocean similarly a large runoff into the arctic during 1964 1966 preceded the large greenland sea ice anomaly of the 1960s these facts together with recent evidence of climatic jumps in the northern hemisphere tropospheric circulation suggest the existence of an interdecadal self sustained climate cycle in the arctic in the greenland sea this cycle is characterized by a state of large sea ice extent overlying an upper layer of cool relatively fresh water that does not convectively overturn which alternates every 10 15 years with a state of small sea ice extent and relatively warm saline surface water that frequently overturns

interdecadal variations in north atlantic sea surface temperature and associated atmospheric conditions abstract evidence is presented for a distinct pattern of ocean atmosphere relationship associated with interdecadal variability in the north atlantic region using a century of surface marine observations it is shown that middle and high latitude sea surface temperature sst display a long term fluctuation with negative anomalies before 1920 and during the 1970s and 1980s positive sst conditions prevailed from about 1930 to 1960 the pattern of interdecadal sst variability is constructed by subtracting the average field during 15 cold years from that during a similar interval of warm years the early century warming and the more recent cooling display a similar spatial pattern in both cases the pattern is basin scale and largely of one polarity with maxima in the vicinity of iceland in the labrador sea and northeast of bermuda the corresponding differences in surface atmospheric conditions are determined by averaging and subtracting in the same manner fields of sea level pressure slp and surf

glacier and lake level variations in west central europe over the last 3500 years on the basis of glacier and lake level records this paper attempts for the first time a comparison between high resolution palaeohydrological and palaeoglaciological data in west central europe over the past 3500 years a data set of tree ring width radiocarbon and archaeological data in addition to historical sources were used to reconstruct fluctuations of the great aletsch the gorner and the lower grindelwald glaciers in the swiss alps the three ice streams experienced nearly synchronous advances at c 1000 600 bc and ad 500 600 800 900 1100 1200 and 1300 1860 these glacier fluctuations show strong correspondence with lake level variations reconstructed in eastern france jura mountains and pre alps and on the swiss plateau this supports the hypothesis of climatically driven fluctuations historical data available for the period since ad 1550 reveal in detail various meteorological conditions behind the successive glacier advances however in agreement with the general trend shown by th

seasonal temperature variability of the neoglacial 3300 2500 bp and roman warm period 2500 1600 bp reconstructed from oxygen isotope ratios of limpet shells patella vulgata northwest scotland abstract seasonal sea surface temperature variability for the neoglacial 3300 2500 bp and roman warm period rwp 2500 1600 bp which correspond to the bronze and iron ages respectively was estimated using oxygen isotope ratios obtained from high resolution samples micromilled from radiocarbon dated archaeological limpet patella vulgata shells the coldest winter months recorded in neoglacial shells averaged 6 6 0 3 c and the warmest summer months averaged 14 7 0 4 c one neoglacial shell captured a year without a summer which may have resulted from a dust veil from a volcanic eruption in the katla volcanic system in iceland rwp shells record average winter and summer monthly temperatures of 6 3 0 1 c and 13 3 0 3 c respectively these results capture a cooling transition from the neoglacial to rwp which is further supported by earlier studies of pine history in scotland pollen type analyses in northeast scotland and european glacial events the cooling transition observed at the boundary between the neoglacial and rwp in our study also agrees with the abrupt climate deterioration at 2800 2700 bp also referred to as the subboreal subatlantic transition and therefore may have been driven by decreased solar radiation and weakened north atlantic oscillation conditions

winter weather patterns over northern eurasia and arctic sea ice loss abstractusing ncep ncar reanalysis and japanese 25 yr reanalysis jra 25 winter daily 1 december 28 february data for the period 1979 2012 this paper reveals the leading pattern of winter daily 850 hpa wind variability over northern eurasia from a dynamic perspective the results show that the leading pattern accounts for 18 of the total anomalous kinetic energy and consists of two subpatterns the dipole and the tripole wind patterns the dipole wind pattern does not exhibit any apparent trend the tripole wind pattern however has displayed significant trends since the late 1980s the negative phase of the tripole wind pattern corresponds to an anomalous anticyclone over northern eurasia during winter as well as two anomalous cyclones occurring over southern europe and in the mid to high latitudes of east asia these anomalous cyclones in turn lead to enhanced winter precipitation in these two regions as well as negative surface temperature anomalies over the mid to high latitudes of asia the

late pleistocene climatic trajectory in the phase space of global ice ocean state and co2 observations and theory we consider the evolution of three main slow response variables describing the state of the climate system during the late pleistocene global ice mass atmospheric carbon dioxide and the ocean state as measured respectively by the specmap 18o record the vostok co2 record and the north atlantic sea surface temperature record at 50 n core k708 1 which is coherent with other ocean state properties their coevolution is portrayed in the form of a trajectory in the phase space of the three variables and its projections on its three phase planes the oscillatory nature and phase lags of the variables are clearly illustrated suggesting a physical process scenario that can account for the observations the basic element of this scenario is a free near 100 kyr period oscillation driven by internal instability involving feedbacks between all three variables under the influence of earth orbital milankovitch forcing and long term tectonic co2 forcing it is shown that a phenomenological theory advanced by the authors emphasizing the role of co2 provides a credible account of the phase space trajectory

the impact of rapid early to mid holocene palaeoenvironmental changes on neolithic settlement at nea nikomideia thessaloniki plain greece the site of nea nikomideia is one of the oldest and most important neolithic settlements in northern greece and the wider balkan peninsula having been first occupied by early farmers at around 6500 cal bc important archaeological excavations conducted in the 1960s suggested that the settlement was located close to an ancient coastline during the neolithic however palaeoenvironmental change and landscape evolution in the vicinity of the site have seldom been considered in detail six cores from the western and central parts of the thessaloniki plain were therefore drilled in 2008 and subjected to palaeoenvironmental analyses including sedimentology laser grain size and magnetic susceptibility measurements chemical analysis loss on ignition and carbonate content stable isotopes analysis coupled with x ray diffraction measurements molluscan faunal analysis and radiocarbon dating the recognition of several important facies representing freshwater lacustrine and fluvial and brackish lagoonal and marine influenced conditions have shed light on the environmental and landscape evolution of the western part of the thessaloniki plain and associated impacts on human occupation during the last 10 000 years the general sequence proved in the cores indicates the predominance of lacustrine conditions during the early holocene with the occurrence of a marine transgression at c 6000 5800 cal b c this major palaeoenvironmental change corresponds with the 8 2 ka event and is a likely cause for the desertion of nea nikomideia at that time subsequent regression of the shoreline to the east saw that the area around nea nikomideia returns to predominantly terrestrial conditions and the deposition of lacustrine and fluvial deposits

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

the interpretation of the icelandic sea ice record the representativeness of the icelandic sea ice record one of the longest climate indicators for the north atlantic sector is assessed by statistical analysis correlation of the sea ice index with ice concentration data for the adjacent seas suggests that the index is a reasonable measure of the ice cover of a large area of the northern north atlantic sector associations with surface air temperature and sea level pressure are strong but regional rather than hemispheric in scale the immediate causes of the variable advance of ice onto the icelandic coasts are clear in the analysis of the atmospheric circulation data severe ice conditions are associated with enhanced anticyclonicity in the icelandic region and stronger northerly and westerly winds over the greenland sea it is concluded that the icelandic index is a useful indicator of the state of the atmospheric flow north of iceland and of the character of the east greenland current one of the major avenues of meridional heat exchange in the climate system

assessment of the relative accuracy of hemispheric scale snow cover maps there are several hemispheric scale satellite derived snow cover maps available but none has been fully validated for the period october 23 december 25 2000 we compare snow maps of north america derived from the moderate resolution imaging spectroradiometer modis and the national oceanic and atmospheric administration noaa national operational hydrologic remote sensing center nohrsc which both rely on satellite data from the visible and near infrared parts of the spectrum we also compare modis and defense meteorological satellite program dmsp special sensor microwave imager ssm i passive microwave snow maps the maps derived from visible and near infrared data are more accurate for mapping snow cover than are the passive microwave derived maps however discrepancies exist as to the location and extent of the snow cover among those maps the large approx 30 km footprint of the ssm i data and the difficulty in distinguishing wet and shallow snow from wet or snow free ground reveal differences up to 5 32 million sq km in the amount of snow mapped using modis versus ssm i data algorithms that utilize both visible and passive microwave data which would take advantage of the all weather mapping ability of the passive microwave data will be refined following the launch of the advanced microwave scanning radiometer amsr in the fall of 2001

the jan mayen current of the greenland sea oceanographic measurements acquired by the usns bartlett during september 1989 in and north of the area of the jan mayen current jmc show that in terms of upper layer baroclinic flow about half of the jmc is a wide meander in the east greenland current egc and about half continues eastward to close the greenland gyre gg on the south this phenomenon has been charted in the past but has elicited no comment surface drifters and a numerical model corroborate this behavior at deeper depths 100 m the meander dissipates with the flow becoming more easterly a drifting float at 500 m depth confirms that the flow is relatively undeviated toward the east ultimately merging with the northward flowing norwegian atlantic current near the gg the fresh water content of the water column is low in the upper layers but high in the middepths where there is a substantial content of egc water e g in the jmc the converse is usually true the fwc of the gg computed for the period 1953 1966 was smaller by a factor of 2 in both layers than in 1989 indicating that 1989 is in another period of low salinity comparable to that of 1968 the period of the great salinity anomaly described by dickson et al 1988

arctic ocean water mass balance from isotope data the distributions of the oxygen 18 and tritium isotopes and of salinity yield a residence time of 10 years for the surface and halocline waters of the arctic basin we find a yearly net production of 0 59 m of sea ice and an input of 1 16 m of freshwater from continental river runoff local precipitation and bering strait salinity deficiency using the basin area value with these numbers gives long term average total net production and transport rates of 0 15 sv of ice and 0 18 sv of meteoric component bering strait water not included if in addition a reasonable depth profile of relative current velocity is assumed for the outflow a yearly input of 2 8 sv of atlantic and bering strait water is needed to replenish the upper and halocline waters these numbers should be good to 20 and are multiyear averages the isotope data clearly indicate that the barents sea is an inflow area for atlantic water to the basin but that net export of ice occurs there

onshore to offshore anatomy of a late quaternary source to sink system po plain adriatic sea italy abstract in understanding the evolution of siliciclastic systems late quaternary analogs may enable reliable predictive models of facies tract architecture the po plain adriatic sea system where a wealth of research has been conducted during the last 20 years represents one of the most intensively investigated late quaternary successions with the aid of a chronologically well constrained stratigraphy paleoenvironmental evolution is tracked for the first time from fluvial to deep marine realms over 1000 km in length vertical stacking trends onshore and stratal terminations offshore are the key observations that allow identification of surfaces with sequence stratigraphic significance systems tract boundaries in the distinct segments of the system recurring motifs in stratigraphic architecture showing tight coupling of sedimentary responses among source area catchment basin and coastal and marine depocenters reveal a cyclicity driven by glacio eustatic fluctuations in the milankovitch band due to high rates of subsidence middle pleistocene forced regressive systems tracts are exceptionally expanded and the mis5e mis2 interval late pleistocene preserves a nearly continuous record of fourth order 100 kyr stepwise sea level fall the stratigraphic architecture of last glacial maximum deposits highlights the genetic relations between channel belt development pedogenesis and sediment delivery to the lowstand delta through narrow incised valley conduits the late glacial holocene succession records the last episode of sea level rise and stabilization through well developed patterns of shoreline transgression regression tst hst that can be readily traced updip from offshore to onshore locations architectural styles across the whole system reflect a dominance of allogenic forcing in the tst as opposed to a predominantly autogenic control on stratigraphic development in the hst external drivers of facies architecture were also effective on millennial timescales the younger dryas cold reversal which marks the transgressive surface on land records a short lived episode of subaqueous progradation that is correlative onshore with widespread immature paleosol development and small sized channel belt formation quantitative assessment of sediment budgets over different time intervals requires precise positioning of the key bounding surfaces based on this approach we outline for the first time over the entire po adriatic basin an estimate of the sediment volumes stored in each systems tract

geoarchaeological approaches to the environmental history of cyprus explication and critical evaluation geoarchaeology represents crossdisciplinary research focused on environmental issues and human activities and directed primarily to social scientists site micro studies are central to the enterprise emphasizing cultural sediments and the taphonomic record of site formation preservation or destruction but when expanded to include off site investigation and watershed studies geoarchaeology can go well beyond stratigraphy and context to address human impacts on the environment or long term sustainability this paper articulates a research agenda to evaluate the largely anecdotal premise that the island of cyprus has been degraded by millennia of improvident land use first it outlines holocene settlement land use and forest histories as a differentiated model against which to apply specific types of investigation and in conjunction with other archaeological sciences second it applies quaternary style watershed study to confront commonplace misunderstandings about possible degradation to show that most of the slope and stream deposits on cyprus are of pleistocene age third it switches to examples of site micro geoarchaeology to illustrate the possibilities of understanding detailed change the purpose is heuristic in the absence of many more site and off site studies that incorporate bioarchaeology provisional inferences suggest that environmental damage may be limited that even with heavy land use stress climatic triggers were critical to inaugurate change and that the system may be more resilient than anticipated such caveats may encourage greater attention to environmental research design in ongoing and future excavation projects

the great salinity anomaly in the northern north atlantic 1968 1982 the widespread freshening of the upper 500 800m layer of the northern north atlantic which this paper describes represents one of the most persistent and extreme variations in global ocean climate yet observed in this century though a range of explanations have been advanced to explain this event including in situ changes in the surface moisture flux this paper describes the great salinity anomaly as largely though not entirely an advective event traceable around the atlantic subpolar gyre for over 14 years from its origins north of iceland in the mid to late 1960s until its return to the greenland sea in 1981 1982 the overall propagation speed around this subpolar gyre is estimated at about 3cm s 1 of the total salt deficit associated with the anomaly as it passed south along the labrador coast in 1971 1973 about 72 109 tonnes a deficit equivalent to about two thirds of this figure 47 109 tonnes ultimately passed through the faroe shetland channel to the barents sea arctic ocean and greenland sea during the mid 1970s possible effects on deep water formation and on the representativeness of historical section data are discussed

revealing climatic variability of the last three millennia in northwestern iberia using pollen influx data climatic variability of the last 3 millennia in nw iberia has been documented using high resolution pollen analysis of vir 18 core retrieved from the ria de vigo 42degrees14 07 n 8degrees47 37 w the depth age model is based on two accelerator mass spectrometry c 14 dates and three historically dated botanical events in galicia the expansion of juglans and pinus as well as the introduction of eucalyptus during the last 3000 years the relative pollen record demonstrates the occurrence of an open deciduous oak forest indicating a humid and temperate climate in northwestern iberia two step forest reduction since 975 cal bc suggests climate as the main cause rather than major socio economic changes documented in historical archives absolute pollen influx has been compared with instrumental summer and winter temperatures and tentatively used as a proxy of short decadal scale and low amplitude similar to 1degreesc temperature variations this new approach allows us to detect for the first time in nw iberia the millennial scale climatic cyclicity suggested by north atlantic records challenging the apparent climatic stability reflected by the relative pollen record the little ice age is recorded as low pollen influx values between 1400 and 1860 cal ad with a cold maximum at 1700 cal ad maunder minimum the roman and medieval warm periods are detected through high pollen influx values at 250 cal bc 450 cal ad and 950 1400 cal ad respectively c 2003 elsevier science b v all rights reserved

limited migration of soluble ionic species in a siple dome antarctica ice core high resolution 10 samples a i glaciochemical analyses covering the last 110 years from a siple dome antarctica ice core reveal limited migration of certain soluble ionic species methane sulfonic acid n03 and mg2 the observed chemical m igration m ay be due in part to seasonal alternation between less acidic winter from h igh sea salt concentrations and m ore acidic summer from high m arine biogenic acid concentrations layers common at coastal sites such as siple dome exact mechanisms to explain the migration are unclear although simple diffusion and gravitational movement are unlikely since new peaks are formed where none previously existed in each case initial migration of each species is both sh allower and earlier at siple dome than at other sites in antarctica where similar phenomena have been observed which may be related to the relatively low accumulation rate at siple dome 13 3 cm ice a i migration appears to be limited to either the preceding or fol lowing seasonal layer for each species suggest ing that paleoclimatic interpretations based on data with lower than annual resolution are not likely to be affected

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

water management and land use in the terramare and a possible climatic co factor in their abandonment the case study of the terramara of poviglio santa rosa northern italy abstract the terramare archaeological sites generated by a civilisation which settled the centre of the po plain since the middle bronze age were abruptly abandoned at the end of the recent bronze age the reason for this abandonment is still a matter of debate in the context of a multi causal explanation this paper discusses a possible climatic factor inferred from recent discoveries at the site of poviglio santa rosa northern italy the culture of the terramare produced a systematic and intensive agricultural and pastoral exploitation of the environment and caused heavy deforestation water was a critical resource and was carefully managed the moat which typically surrounded most of the sites was meant to concentrate and redistribute water to the fields through a network of irrigation ditches the study of the water wells discovered at the fringe of the terramara of santa rosa reveals a drop in the water table during the late recent bronze age caused by a dry event of regional relevance chronological contiguity supported by the archaeological context between this occurrence and the abandonment of the terramare system strongly suggests a causative link between the two events the climatic event a minor episode in the history of the holocene climate nevertheless acted as a catalyst in a stressed environment whose resources were over exploited by rising demographic pressure

high latitude salinity effects and interhemispheric thermohaline circulations a general circulation model for the ocean is used to investigate the interaction between the global scale thermohaline circulation and the salinity distribution it is shown that an equatorially asymmetric circulation can be maintained even under equatorially symmetric basin geometry and surface forcing multiple equilibrium solutions are obtained for the same forcing by perturbing the high latitude salinity field in an otherwise equatorially symmetric initial condition the timescale of the transition from the symmetric circulation to an asymmetric circulation depends critically on the sign of the initial salinity perturbation

influence of inherited topography on the holocene sedimentary evolution of coastal systems an example from arno coastal plain tuscany italy abstract understanding the relative control exerted by autogenic factors such as changes in sediment supply local subsidence and inherited topography is of crucial interest for a thorough comprehension of the sedimentary evolution of late quaternary coastal systems through an example from the arno coastal plain in tuscany we show to what extent sedimentation of the holocene succession even after the time of maximum marine ingression was influenced by the presence of a buried 5 7 km wide incised valley system generated by the arno river during the late pleistocene in response to the last glacial sea level fall a prominent stratigraphic marker locally known as pancone ca 5 15 m thick made up of extremely soft and homogeneous organic rich clays is reported from the upper 20 30 m of the mid holocene succession buried beneath the arno coastal plain high resolution stratigraphy integrated with microfossil investigations enables detailed facies characterization and mapping of this marker horizon at proximal most locations pancone consists of thin lagoonal deposits sandwiched between backswamp clays around the city of pisa and at more distal locations this stratigraphic marker is made up almost entirely of lagoonal clays with lateral transition to backswamp deposits the development of pancone was triggered by an abrupt transgressive pulse that led to the ultimate flooding of the arno paleovalley this transgressive event occurred shortly after a widespread episode of sub aerial exposure and climate deterioration related to the 8200 yr bp cold event confinement of the mid holocene pancone lagoon into an area formerly occupied by the post glacial arno incised valley system along with transition to backswamp facies in coincidence of the former interfluves is interpreted to reflect the higher compaction of the less indurated valley fill relative to the adjacent stiff pleistocene substratum the local increase in land subsidence contributed to the prolonged persistence of a 6 km wide lagoonal system encompassing the peak of holocene transgression and the early phases of decelerated sea level rise up to ca 6000 cal yr bp the arno coastal plain thus offers a good illustration of how inherited topography due to the presence of formerly active incised valleys may influence the holocene evolution of coastal plains favoring local development and preservation of topographic lows

a simple steady state coupled ice ocean model with application to the greenland norwegian sea abstract a thermodynamic reduced gravity ocean model forced by the steady state surface wind stress and a haney type heat flux was used to determine the climatological ice edge position ice thickness ocean circulation and upper ocean temperature in a high latitude meridional channel the ice model used is purely thermodynamic however a parameterization is used to allow the surface wind stress to be transmitted to the water below the ice the temperature distribution of the upper ocean is specified along the southern zonal boundary of the model domain and the heat equation is integrated from this boundary poleward along streamlines for the mass transport as a column of warm water moves poleward its temperature tends to decrease since the air temperature monotonically decreases to the north at high latitudes the steady state heat balance between horizontal advection and cooling to the atmosphere can no longer hold in an ice free ocean thus an ice layer forms to insulate the ocean from the very co

palaeoenvironments and palaeotopography of a multilayered city during the etruscan and roman periods early interaction of fluvial processes and urban growth at pisa tuscany italy a critical geoarchaeological approach based on fully integrated archaeological geomorphological and stratigraphic data allowed for the identification of the palaeoenvironments palaeotopography and urban growth patterns of pisa nw italy during the etruscan first half of the 5th century bc first half of the 1st century bc and roman second half of the 1st century bc 2nd century ad periods this powerful methodology based on aerial and satellite images electrical resistivity tomography lidar and core analysis led to the reconstruction of landscape evolution highlighting human environment interactions during the etruscan and roman periods pisa saw a fast urban expansion in a dense and unstable fluvial network wide portions of the city were characterised by poorly drained conditions until the 1st century ad when the alluvial plain became well drained under increasing anthropogenic pressure roman centuriatio poorly drained floodplains and channel related backswamps represent the topographically lowest zones of the ancient pisa this city developed within an intricate pattern of palaeochannels related to two main rivers the palaeoarno which flowed in proximity of its present position and the former palaeoserchio river known as auser flowing in the northern part of the city since etruscan times a mounded relief was formed in the historical city centre of pisa becoming wider and more prominent up to ca 2 m a s l during the roman period concomitant with a southward rapid expansion of the urban tissue nevertheless the urban growth patterns substantially followed the etruscan city s fabric with marked concentration of the urban structures public and private buildings and manufacturing sites on the northern relief close to the auser the auser river thus played a crucial role in the environmental and topographic evolution of the city area

topographic expression of active faults in the foothills of the northern apennines abstract active faults that rupture the earth s surface leave an imprint on the topography that is recognized using a combination of geomorphic and geologic metrics including triangular facets the shape of mountain fronts the drainage network and incised river valleys with inset terraces we document the presence of a network of active high angle extensional faults collectively embedded in the actively shortening mountain front of the northern apennines that possess unique geomorphic expressions we measure the strain rate for these structures and find that they have a constant throw to length ratio we demonstrate the necessary and sufficient conditions for triangular facet development in the footwalls of these faults and argue that rock type exerts the strongest control the slip rates of these faults range from 0 1 to 0 3 mm yr which is similar to the average rate of river incision and mountain front unroofing determined by corollary studies the faults are a near surface manifestation of deeper crustal processes that are actively uplifting rocks and growing topography at a rate commensurate with surface processes that are eroding the mountain front to base level

human landscape interactions in the bologna area northern italy during the mid late holocene with focus on the roman period integrated sedimentological and archaeological investigations of mid late holocene deposits from the subsurface of bologna elucidate the complex relationship among urban settlement human society geomorphology and climate change at the southern margin of the po plain above the pleistocene holocene unconformity the holocene succession forms an intricate mosaic of alluvial deposits two palaeosols spanning between about 8000 5000 cal yr bp and 3200 1500 cal yr bp respectively represent the most prominent stratigraphic markers across the study units a huge amount of archaeological remains from the younger palaeosol enables the identification of an uninterrupted sequence of settlements from the early iron age to the late roman period the first permanent settlements of iron age took place in a topographically elevated region protected from flooding the onset of paedogenesis during this period reflects the radical transformation of the environment by human settlements through widespread control of th

deep water formation and quaternary glaciations a large fraction of climatic varability on the quaternary time scale can be explained by nonlinear interactions between the radiation balance of the global atmosphere ocean system and the mass balance of northern hemisphere ice sheets recent analyses of paleoclimatic proxy data indicate a further important contribution to this variability from changes in deep water formation occurring in the north atlantic subpolar sea we study the effects of these changes on variations in global temperature and ice volume characteristic of the late quaternary the novel framework of boolean delay equations bdes is used to formulate a conceptual model of the climatic system under study and to analyze this formal model selfsustained oscillations in the intensity of the atlantic ocean s thermohaline circulation result from the interaction of sea ice formation with the waxing and waning of continental ice sheets the comparison of model results with paleoclimatic records suggests a considerable slowing down of the abyssal circulation during glacial episodes