the effect of earth rheology and ice sheet size on fault slip and magnitude of postglacial earthquakes abstract moderate past and present day seismicity is observed in formerly deglaciated regions of north america and europe an understanding of the occurrence of these earthquakes is important for estimating the seismic risk within these areas as well as areas affected by recent ice sheet melting in particular greenland and antarctica we have developed a new finite element approach that allows us to estimate the fault throw for areas once covered by a continental ice sheet the simulation is initialized by loading a two dimensional earth model with an ice sheet the model incorporates a stress field consisting of rebound horizontal background and vertical stresses as well as a fault that can accommodate slip the sensitivity of fault throw and activation time is tested with respect to lithospheric and crustal thickness viscosity structure of upper and lower mantle and ice sheet thickness and width as well as fault location and angle single event seismic displacements of up to 18 5 m are obtained approximately equivalent to an earthquake with a moment magnitude of 8 5 the thickness of the crust and lithosphere are major parameters affecting the total magnitude of fault slip whereas the size of the ice sheet primarily affects the activation time most faults start to move close to the end of deglaciation and movement typically stops for our simulations after one thrusting reverse earthquake however in our simulations faults with a dip of 60 also show several fault movements before and after the end of deglaciation

combined influences of seasonal east atlantic pattern and north atlantic oscillation to excite atlantic multidecadal variability in a climate model the physical processes underlying the internal component of the atlantic multidecadal variability amv are investigated from a 1 000 yr pre industrial control simulation of the cnrm cm5 model the low frequency fluctuations of the atlantic meridional overturning circulation amoc are shown to be the main precursor for the model amv the full life cycle of amoc amv events relies on a complex time evolving relationship with both north atlantic oscillation nao and east atlantic pattern eap that must be considered from a seasonal perspective in order to isolate their action the ocean is responsible for setting the multidecadal timescale of the fluctuations amoc rise leading to a warm phase of amv is statistically preceded by wintertime nao and eap from lag 40 20 yrs associated wind stress anomalies induce an acceleration of the subpolar gyre spg and enhanced northward transport of warm and saline subtropical water concurrent positive salinity anomalies occur in the greenland iceland norwegian seas in link to local sea ice decline those are advected by the eastern greenland current to the labrador sea participating to the progressive densification of the spg and the intensification of ocean deep convection leading to amoc strengthening from lag 10 yrs prior an amoc maximum opposite relationship is found with the nao for both summer and winter seasons despite negative lags nao at that time is consistent with the atmospheric response through teleconnection to the northward shift intensification of the inter tropical convergence zone in link to the ongoing warming of tropical north atlantic basin due to amoc rise amv build up nao acts as a positive feedback for the full development of the model amv through surface fluxes but at the same time prepares its termination through negative retroaction on amoc relationship between eap and amoc is also present in summer from lags 30 10 yrs while winter eap is favored around the amv peak based on additional atmospheric forced experiments both are interpreted as the local seasonal dependent atmospheric response to warmer north atlantic finally advection of fresher water from the tropical basin created by local atmosphere ocean anomalous circulation on one hand and from the arctic on the other hand due to large scale sea ice melting leads to decrease of density in the spg and contributes terminating the model amoc amv events all together the combined effects of nao and eap their intertwined seasonal forcing forced role upon by the ocean and the primary role of salinity anomalies associated with oceanic dynamical changes acting as an integrator are responsible in cnrm cm5 for an irregular and damped mode of variability for amoc amv that takes about 35 40 15 20 years to build up dissipate

a 20 year coupled ocean sea ice atmosphere variability mode in the north atlantic in an aogcm in order to understand potential predictability of the ocean and climate at the decadal time scales it is crucial to improve our understanding of internal variability at this time scale here we describe a 20 year mode of variability found in the north atlantic in a 1 000 year pre industrial simulation of the ipsl cm5a lr climate model this mode involves the propagation of near surface temperature and salinity anomalies along the southern branch of the subpolar gyre leading to anomalous sea ice melting in the nordic seas which then forces sea level pressure anomalies through anomalous surface atmospheric temperatures the wind stress associated to this atmospheric structure influences the strength of the east greenland current across the denmark strait which in turn induces near surface temperature and salinity anomalies of opposite sign at the entrance of the labrador sea this starts the second half of the cycle after approximatively 10 years the time scale of the cycle is thus essentially set by advection of tracers along the southern branch of the subpolar gyre and by the time needed for anomalous east greenland current to accumulate heat and freshwater anomalies at the entrance of the labrador sea the atlantic meridional overturning circulation amoc does not play a dominant role in the mode that is confined in the subpolar north atlantic but it also has a 20 year preferred timescale this is due to the influence of the propagating salinity anomalies on the oceanic deep convection the existence of this preferred timescale has important implications in terms of potential predictability of the north atlantic climate in the model although its realism remains questionable and is discussed

activity along the osning thrust in central europe during the lateglacial ice sheet and lithosphere interactions abstract the osning thrust is one of the major fault systems in central europe with a length of approximately 115 km it underwent a polyphase tectonic evolution in the mesozoic that ranged from extensional movements in the jurassic to reverse faulting and thrusting during inversion in the late cretaceous a series of complex metre scale faults and related fold structures are developed within the upper pleistocene alluvial aeolian complex of the upper senne 1 km away from the thrust the faults dip towards the north and show offsets in a range of several decimetres growth strata indicate a two fold evolution of the structures the faults began as normal faults and were later transformed into reverse faults which resulted in the formation of small scale inversion structures with a typical harpoon shape glaciotectonics can be ruled out as the driving mechanism for these structures because new optically stimulated luminescence osl ages imply that the sedimentary succession was deposited during the late pleistocene between 29 3 2 9 ka and 13 1 1 5 ka at which time the ice margin was much further to the northeast we believe the inversion structures were caused by movement on the osning thrust due to generation of a forebulge of the late pleistocene weichselian ice sheet this led to normal faulting as a consequence of extension in the forebulge area during glaciation the osl ages for the normal fault related growth strata are in a range of 16 13 ka later reverse movements occurred during deglaciation due to the n s directed compressional stress field in northern germany numerical simulations of the deglaciation seismicity point to seismic events with a thrust mechanism in the study area between 15 5 and 12 3 ka bp although normal faulting is also possible in this time period numerous soft sediment deformation structures imply that movement on the osning thrust caused earthquakes with a significant magnitude in the autumn of 1612 an earthquake took place in this area it is very likely that this event is related to background seismicity on this fault although movement due to the influence of the ongoing glacial rebound in fennoscandia is also possible

sequential evolution and diagenesis of pleistocene coral reefs south sinai egypt abstract the uplifted pleistocene coral reefs in south sinai represent two major depositional sequences they generally form two morphological terraces which locally are tilted and offset by still active faulting the major reef sequences are composed of several small scale sequences corals grew rapidly when accommodation space was created by eustatic sea level rise or fault block subsidence as the accommodation decreased coral rubble and siliciclastic sands prograded over reefal and lagoonal sediments thus creating a shallowing upward sequence terrigenous input was further stimulated by a more humid climate during interglacial times 230 th 234 u dating places the older reef cycle between 350 000 and 270 000 years b p which corresponds to the interglacial period of isotope stage 9 the younger reef cycle has been dated between 140 000 and 60 000 years b p isotope stage 5 an intermediate relic sequence found in only one outcrop can be attributed to isotope stage 7 correlation of the small scale sequences is difficult age dating is not precise enough and local tectonic activity in many cases overruled the smaller eustatic fluctuations the younger reef sequence commonly exhibits marine cements whereas the older sequence was exposed to freshwater dissolution and cementation an important feature is the locally pervasive dolomitization especially of the older reef oxygen and carbon isotope values suggest that the dolomite formed in a seawater dominated mixing zone multiple phases of dissolution cementation and dolomitization point to a very complex diagenetic history

sequence stratigraphy of carbonate evaporite basins models and application to the upper permian zechstein of northeast england and adjoining north sea the successions of carbonate evaporite basins which are periodically cut off from the world ocean are considered in terms of their sequence stratigraphy two basin types are distinguished those where incomplete drawdown takes place and those showing complete drawdown and wholesale basin desiccation it is argued that following relative sea level falls sequences begin with the evaporites precipitated as marginal lowstand gypsum wedges in the first basin type and as lowstand basin centre halite fills in the second the evaporites pass up into carbonate sediments which are mainly deposited on shallow water platforms around the basin during transgressive and highstand systems tracts the concepts and models developed are applied to the zechstein upper permian strata of northeast england and adjoining north sea seven sequences are proposed with some containing thin parasequences the sequence approach to carbonate evaporite basins which considers both basin margin and basin centre facies gives a more encompassing perspective of sedimentation than the traditional cycle concept with its emphasis on the basin centre

new empirical relationships among magnitude rupture length rupture width rupture area and surface displacement source parameters for historical earthquakes worldwide are compiled to develop a series of empirical relationships among moment magnitude m surface rupture length subsurface rupture length downdip rupture width rupture area and maximum and average displacement per event the resulting data base is a significant update of previous compilations and includes the additional source parameters of seismic moment moment magnitude subsurface rupture length downdip rupture width and average surface displacement each source parameter is classified as reliable or unreliable based on our evaluation of the accuracy of individual values only the reliable source parameters are used in the final analyses in comparing source parameters we note the following trends 1 generally the length of rupture at the surface is equal to 75 of the subsurface rupture length however the ratio of surface rupture length to subsurface rupture length increases with magnitude 2 the average surface displacement per event is about one half the maximum surface displacement per event and 3 the average subsurface displacement on the fault plane is less than the maximum surface displacement but more than the average surface displacement thus for most earthquakes in this data base slip on the fault plane at seismogenic depths is manifested by similar displacements at the surface log linear regressions between earthquake magnitude and surface rupture length subsurface rupture length and rupture area are especially well correlated showing standard deviations of 0 25 to 0 35 magnitude units most relationships are not statistically different at a 95 significance level as a function of the style of faulting thus we consider the regressions for all slip types to be appropriate for most applications regressions between magnitude and displacement magnitude and rupture width and between displacement and rupture length are less well correlated and have larger standard deviation than regressions between magnitude and length or area the large number of data points in most of these regressions and their statistical stability suggest that they are unlikely to change significantly in response to additional data separating the data according to extensional and compressional tectonic environments neither provides statistically different results nor improves the statistical significance of the regressions regressions for cases in which earthquake magnitude is either the independent or the dependent parameter can be used to estimate maximum earthquake magnitudes both for surface faults and for subsurface seismic sources such as blind faults and to estimate the expected surface displacement along a fault for a given size earthquake

lake sediment evidence of paleoseismicity timing and spatial occurrence of late and postglacial earthquakes in finland abstract sediment profiles in six lake basins located near the late and postglacial fault surface ruptures in northern finland were investigated for turbidites and soft sediment deformation structures that could reveal information on the timing and spatial occurrence of paleoearthquakes in the area we used geophysical sub bottom profiling and lithological logging of sediment cores combined with radiocarbon and paleomagnetic dating in three lakes immeljarvi aakenus and laukkujarvi sediment records provided evidence of postglacial earthquakes or landslides whereas in three others lakes pyhajarvi kallojarvi and syvajarvi no disturbance structures were observed in their sequences that cover roughly the holocene period combined with previous data on paleoseismicity in finland the results enhance the non stationary hypothesis of seismicity throughout the late weichselian and the holocene with three general maxima that cluster around the deglaciation 12 0 10 0 kyr bp the mid holocene 5 0 7 0 kyr bp and the late holocene 1 5 3 0 kyr bp a strong asymmetry of the offset profiles of the finnish postglacial fault complexes indicate that the general rupture propagation was from sw to ne the present data also indicates that the oldest and highest magnitude events mw 7 or higher generally took place in the sw sector of the finnish pgf complexes during or soon after the retreat of the continental ice sheet the ruptures then propagated towards the ne sector of pgf complexes in a cascading fashion and were generally characterized by lower magnitude events mw 6 during the holocene

major earthquake at the pleistocene holocene transition in lake vattern southern sweden lake vattern sweden is within a graben that formed through rifting along the boundary between two precambrian terrains geophysical mapping and geological coring show that substantial tectonic movements along the lake vattern graben occurred at the very onset of the holocene this is evident from deformation structures in the soft sediment accumulated on the lake floor our interpretation of these structures suggests as much as 13 m of vertical tectonic displacements along sections of a 80 km long fault system if these large displacements are from one tectonic event lake vattern must have had an earthquake with seismic moment magnitudes to 7 5 in addition our geophysical mapping shows large landslides along sections of the steep lake shores pollen analysis of sediment infillings of some of the most prominent sediment deformation structures places this major seismic event at the younger dryas preboreal transition ca 11 5 ka we suggest that this event is mainly related to the rapid release of ice sheet load following the deglaciation this paleoseismic event in lake vattern ranks among the larger known intraplate tectonic events in scandinavia and attests to the significance of glacio isostatic unloading

astronomical frequencies for pre quaternary palaeoclimate studies the sensitivity of the earth s orbital frequencies involved in the astronomical theory of palaeoclimates to the earth moon distance and consequently to the length of the day and to the dynamical ellipticity of the earth has been investigated for the last billion years the shortening of the earth moon distance and of the length of the day back in time induces a shortening of the fundamental astronomical periods for the obliquity and the precession a shortening which is larger for the longer periods these periods of precession and obliquity influenced by the changing earth moon distance length of the day and dynamical ellipticity of the earth have been recomputed for the last 440 million years

sea level changes an integrated approach sea level changes an integrated approach in october 1985 sepm sponsored a four day conference entitled sea level changes an integrated approach the purpose of the conference was to provide a forum for an interdisciplinary exchange of ideas on sea level changes and to provide an opportunity for integrating various types of evidence in approaching unresolved issues the conference was successful in bringing together scientists from industry academia and government representing all of the major geosciences disciplines presentations of many new papers plus significant releases of data that were previously held proprietary provided fertile ground for discussion this much cited volume represents the best of the material presented at the conference includes the early vail chart

a consistent poleward shift of the storm tracks in simulations of 21st century climate 1 a consistent poleward and upward shift and intensification of the storm tracks is found in an ensemble of 21st century climate simulations performed by 15 coupled climate models the shift of the storm tracks is accompanied by a poleward shift and upward expansion of the midlatitude baroclinic regions associated with enhanced warming in the tropical upper troposphere and increased tropopause height the poleward shift in baroclinicity is augmented in the southern hemisphere and partially offset in the northern hemisphere by changes in the surface meridional temperature gradient the poleward shift of the storm tracks also tends to be accompanied by poleward shifts in surface wind stress and precipitation and a shift towards the high index state of the annular modes these results highlight the integral role that the storm tracks play in the climate system and the importance of understanding how and why they will change in the future

annular modes in the extratropical circulation part i month to month variability the leading modes of variability of the extratropical circulation in both hemispheres are characterized by deep zonally symmetric or annular structures with geopotential height perturbations of opposing signs in the polar cap region and in the surrounding zonal ring centered near 458 latitude the structure and dynamics of the southern hemisphere sh annular mode have been extensively documented whereas the existence of a northern hemisphere nh mode herein referred to as the arctic oscillation ao has only recently been recognized like the sh mode the ao can be defined as the leading empirical orthogonal function of the sea level pressure field or of the zonally symmetric geopotential height or zonal wind fields in this paper the structure and seasonality of the nh and sh modes are compared based on data from the national centers for environmental prediction national center for atmospheric research reanalysis and supplementary datasets the structures of the nh and sh annular modes are shown to be remarkably similar not only in the zonally averaged geopotential height and zonal wind fields but in the mean meridional circulations as well both exist year round in the troposphere but they amplify with height upward into the stratosphere during those seasons in which the strength of the zonal flow is conducive to strong planetary wave mean flow interaction midwinter in the nh and late spring in the sh during these active seasons the annular modes modulate the strength of the lagrangian mean circulation in the lower stratosphere total column ozone and tropopause height over mid and high latitudes and the strength of the trade winds of their respective hemispheres the nh mode also contains an embedded planetary wave signature with expressions in surface air temperature precipitation total column ozone and tropopause height it is argued that the horizontal temperature advection by the perturbed zonal mean zonal wind field in the lower troposphere is instrumental in forcing this pattern a companion paper documents the striking resemblance between the structure of the annular modes and observed climate trends over the past few decades

simulated variability of the circulation in the north atlantic from 1953 to 2003 abstract the variability of the circulation in the north atlantic and its link with atmospheric variability are investigated in a realistic hindcast simulation from 1953 to 2003 the interannual to decadal variability of the subpolar gyre circulation and the meridional overturning circulation moc is mostly influenced by the north atlantic oscillation nao both circulations intensified from the early 1970s to the mid 1990s and then decreased the monthly variability of both circulations reflects the fast barotropic adjustment to nao related ekman pumping anomalies while the interannual to decadal variability is due to the baroclinic adjustment to ekman pumping buoyancy forcing and dense water formation consistent with previous studies an original characteristic of the oceanic response to nao is presented that relates to the spatial patterns of buoyancy and wind forcing over the north atlantic anomalous ekman pumping associated with a positive nao phase first induces a decrease of the southern sub

coherence of antarctic sea levels southern hemisphere annular mode and flow through drake passage 1 it is known from small sets of tide gauges that sub surface pressure sea level corrected for the inverse barometer effect around antarctica varies coherently around about half of the continent and that this coherent signal is related to atmospheric forcing in the form of the antarctic oscillation or southern hemisphere annular mode we here confirm that this coherence extends to a more extensive network of tide gauges and to parts of the continental shelf far from the shore as measured by bottom pressure gauges we use time series from an eddy permitting ocean model with realistic forcing to relate the coherent mode to fluctuations in transport through drake passage and confirm using a 1 resolution barotropic model that the fluctuations are predominantly due to barotropic dynamics although baroclinic dynamics are expected to play an increasing role at interannual timescales

microearthquakes illuminate the deep structure of the endglacial parvie fault northern sweden at 155 km the parvie fault is the world s longest known endglacial fault egf it is located in northernmost sweden in a region where several kilometre scale egfs have been identified based on s

magnesian calcite cements and their diagenesis dissolution and dolomitization mururoa atoll the most ubiquitous syn sedimentary cements affecting mururoa atoll are composed of magnesian calcite three main types are distinguished fibrous bladed and sparitic on the basis of petrography morphology and mgco3 concentration of the constituting crystals while peloid infills a particular form of hmc chemical precipitation also exist petrographic evidence and isotopic signatures are compatible with marine precipitation mururoa atoll was exposed several times to meteoric diagenesis resulting in varied diagenetic alterations including selective dissolution and partial dolomitization of mg calcite cements these alterations are responsible for substantial modifications of the initial cement fabrics and may introduce unconformities in the diagenetic chronology the first stage of the partial dissolution of mg calcite induces the development of chalky white friable zones within the initially crystalline hard cement layers at ultrascale this is due to the creation of micro voids along the elongate cement fibres advanced dissolution includes total disappearance of cement portions as attested to by large voids within the cement crust and or between superposed cement layers mg calcite dissolution is related to meteoric diagenesis during periods of quaternary exposure the creation of voids within mg calcite layers is due to the mechanical removal of previously altered calcium carbonate a process suggesting marine or non marine water flow probably in the vadose environment selective dolomitization of mururoa cements involves alternations of calcite and dolomite which form successive cement like rinds within primary cavities at mururoa these alternations are the result of selective dolomitization of the pre existing mg calcite cements rather than successive precipitation of calcite and dolomite selective dolomitization of mg calcite cements at mururoa indicates that a given cement succession is not necessarily a simple chronological sequence oxygen isotope values of dolomites are enriched in 186 by about 3 pdb within calcite dolomite pseudo alternations the dolomitizing fluid at mururoa seems similar to present marine water although some mixture with meteoric water is probable to favour dissolution associated with dolomitization

interdecadal variations of the thermohaline circulation in a coupled ocean atmosphere model abstract a fully coupled ocean atmosphere model is shown to have irregular oscillations of the thermohaline circulation in the north atlantic ocean with a time scale of approximately 50 years the irregular oscillation appears to be driven by density anomalies in the sinking region of the thermohaline circulation approximately 52 n to 72 n combined with much smaller density anomalies of opposite sign in the broad rising region the spatial pattern of see surface temperature anomalies associated with this irregular oscillation bears an encouraging resemblance to a pattern of observed interdecadal variability in the north atlantic the anomalies of sea surface temperature induce model surface air temperature anomalies over the northern north atlantic arctic and northwestern europe

sequence stratigraphy and cyclic development of basal zechstein carbonate evaporite deposits with emphasis on zechstein 2 off platform carbonates upper permian northeast germany abstract although the basal zechstein is classically subdivided into two cycles z1 and z2 lower part it can alternatively be subdivided into three complete third order depositional sequences zs1 zs3 and the associated lowstand systems tract transgressive systems tract of a fourth sequence zs4 third and higher order sea level fluctuations influenced the depositional and diagenetic history of the carbonate evaporite alternations within the basal zechstein the main subject of the present study the zechstein 2 carbonate stassfurt carbonate or ca2 is interpreted to encompass both transgressive predominantly in slope and basinal settings and highstand systems tracts of zechstein sequence zs3 as well as part of the lowstand systems tract of the fourth zechstein sequence zs4 in northeastern germany hydrocarbon reservoirs of the ca2 developed along both northern and southern margins of the southern permian basin on top of the topography of the zechstein 1 cycle z1 this z1 topography resulted from deposition of the werra anhydrite a1 the highstand systems tract of the second zechstein sequence zs2 the northern ca2 carbonate platform is consistently narrow and fringed by coated grain and composite grain bars and shoals it is characterized by a steep fault controlled slope which precluded the formation of in situ shallow water grain dominated carbonates during relative sea level lowstands displaced shallow water coated grain and composite grain packstones wackestones may however occur as slope fan deposits turbidites in contrast the southern carbonate platform is wide tectonically dissected and fringed by grain dominated shallow water carbonates coated grain and composite grain bars and shoals zechstein 2 shallow water carbonates detectable by basal zechstein seismic anomalies also developed on pre existing topographical highs in off platform positions three depositional cycles ca2 cycles i ii and iii most probably reflecting high amplitude fourth order sea level fluctuations can be identified within the stassfurt carbonate our observations suggest that sea level variations possibly reflecting cyclicity in the milankovitch frequency band 0 1 0 4 ma and the pre zechstein topography pronounced during formation of the werra anhydrite were the most important factors in controlling the depositional as well as the diagenetic history of the zechstein 2 carbonate in off platform positions

climate response to external sources of freshwater north atlantic versus the southern ocean abstract the response of an atmosphere ocean general circulation model aogcm to perturbations of freshwater fluxes across the sea surface in the north atlantic and southern ocean is investigated the purpose of this study is to investigate aspects of the so called bipolar seesaw where one hemisphere warms and the other cools and vice versa due to changes in the ocean meridional overturning the experimental design is idealized where 1 sv 1 sv 106 m3 s 1 of freshwater is added to the ocean surface for 100 model years and then removed in one case the freshwater perturbation is located in the atlantic ocean from 50 to 70 n in the second case it is located south of 60 s in the southern ocean in the case where the north atlantic surface waters are freshened the atlantic thermohaline circulation thc and associated northward oceanic heat transport weaken in the antarctic surface freshening case the atlantic thc is mainly unchanged with a slight weakening toward the end of the integration this w

local and remote impacts of a tropical atlantic salinity anomaly the climatic impacts of an enhanced evaporation prescribed during 50 years in the tropical atlantic are investigated in a coupled ocean atmosphere general circulation model locally the salinity increase leads to a rapid deepening and cooling of the surface mixed layer this induces a deepening of the equatorial undercurrent and an intensification of the south equatorial current a remote atmospheric response to the tropical atlantic perturbation is detected in the north atlantic sector after ten years it has the form of a robust wave like tropospheric perturbation seemingly excited by the weakening of atmospheric deep convection over the amazonian basin meanwhile the salt anomaly is carried northward by the mean oceanic circulation it is traced up to the convection sites and then on its return path at depth towards lower latitudes consistent with the density increase deep convection is enhanced after the arrival of the salt anomaly and the atlantic meridional overturning circulation amoc intensifies about 20 years after the beginning of the perturbation the adjustment of the tropical atlantic to the amoc intensification then modifies its initial response to the freshwater forcing leading to a weaker cooling in the northern tropical atlantic than in the southern tropical atlantic a slight northward shift of the tropical atlantic precipitation pattern and an intensification of the north brazil current on the other hand no significant anomalous precipitations are found in the pacific the initial remote atmospheric response is also modulated by an nao like response to the amoc intensification

simulating earthquake rupture and off fault fracture response application to the safety assessment of the swedish nuclear waste repository abstract to assess the long term safety of a deep repository of spent nuclear fuel upper bound estimates of seismically induced secondary fracture shear displacements are needed for this purpose we analyze a model including an earthquake fault which is surrounded by a number of smaller discontinuities representing fractures on which secondary displacements may be induced initial stresses are applied and a rupture is initiated at a predefined hypocenter and propagated at a specified rupture speed during rupture we monitor shear displacements taking place on the nearby fracture planes in response to static as well as dynamic effects as a numerical tool we use the 3dimensional distinct element code 3dec because it has the capability to handle numerous discontinuities with different orientations and at different locations simultaneously in tests performed to benchmark the capability of our method to generate and propagate seismic waves 3dec generates results in good agreement with results from both stokes solution and the compsyn code package in a preliminary application of our method to the nuclear waste repository site at forsmark southern sweden we assume end glacial stress conditions and rupture on a shallow gently dipping highly prestressed fault with low residual strength the rupture generates nearly complete stress drop and an m w 5 6 event on the 12 km 2 rupture area of the 1584 secondary fractures 150 m radius with a wide range of orientations and locations relative to the fault a majority move less than 5 mm the maximum shear displacement is some tens of millimeters at 200 m fault fracture distance

links between the southern annular mode and the atlantic meridional overturning circulation in a climate model abstract the links between the atmospheric southern annular mode sam the southern ocean and the atlantic meridional overturning circulation amoc at interannual to multidecadal time scales are investigated in a 500 yr control integration of the l institut pierre simon laplace coupled model version 4 ipsl cm4 climate model the antarctic circumpolar current as described by its transport through the drake passage is well correlated with the sam at the yearly time scale reflecting that an intensification of the westerlies south of 45 s leads to its acceleration also in phase with a positive sam the global meridional overturning circulation is modified in the southern hemisphere primarily reflecting a forced barotropic response in the model the amoc and the sam are linked at several time scales an intensification of the amoc lags a positive sam by about 8 yr this is due to a correlation between the sam and the atmospheric circulation in the northern north atlantic that reflects a symmetric e

coupled ocean atmosphere ice response to variations in the southern annular mode abstract the coupled ocean atmosphere ice response to variations in the southern annular mode sam is examined in the national center for atmospheric research ncar community coupled climate model version 2 the model shows considerable skill in capturing the predominantly zonally symmetric sam while regional deviations between model and observation sam winds go a long way in explaining the generally small differences between simulated and observed sam responses in the ocean and sea ice systems vacillations in the position and strength of the circumpolar winds and the ensuing variations in advection of heat and moisture result in a dynamic and thermodynamic forcing of the ocean and sea ice both meridional and zonal components of ocean circulation are modified through ekman transport which in turn leads to anomalous surface convergences and divergences that strongly affect the meridional overturning circulation and potentially the pathways of intermediate water ventilation a heat budget analysis de

atlantic multidecadal oceanic variability and its influence on the atmosphere in a climate model the mechanisms controlling the decadal to multidecadal variability of the atlantic meridional overturning circulation moc and its influence on the atmosphere are investigated using a control simulation with the ipsl cm4 climate model the multidecadal fluctuations of the moc are mostly driven by deep convection in the subpolar gyre which occurs south of iceland in the model the latter is primarily influenced by the anomalous advection of salinity due to changes in the east atlantic pattern eap which is the second mode of atmospheric variability in the north atlantic region the north atlantic oscillation is the dominant mode but it plays a secondary role in the moc fluctuations during summer the moc variability is shown to have a significant impact on the atmosphere in the north atlantic european sector the moc influence is due to an interhemispheric sea surface temperature sst anomaly with opposite signs in the two hemispheres but largest amplitude in the northern one the sst pattern driven by the moc mostly resembles the model atlantic multidecadal oscillation amo and bears some similarity with the observed one it is shown that the amo reflects both the moc influence and the local atmospheric forcing hence the moc influence on climate is best detected using lagged relations between climatic fields the atmospheric response resembles the eap in a phase that might induce a weak positive feedback on the moc

stress and fault parameters affecting fault slip magnitude and activation time during a glacial cycle stress and fault parameters affecting fault slip magnitude and activation time during a glacial cycle

a model of the upper branch of the meridional overturning of the southern ocean a zonal average model of the upper branch of the meridional overturning circulation of the southern ocean is constructed and used to discuss the processes wind buoyancy eddy forcing and boundary conditions that control its strength and sense of circulation the geometry of the thermocline wedge set by the mapping between the vertical spacing of buoyancy surfaces the stratification on the equatorial flank of the antarctic circumpolar current and their outcrop at the sea surface is seen to play a central role by setting the interior large scale potential vorticity distribution it is shown that the action of eddies mixing this potential vorticity field induces a residual flow in the meridional plane much as is observed with upwelling of fluid around antarctica northward surface flow and subduction to form intermediate water

sst front anchored mesoscale feature of surface wind in the southern indian ocean using 28 year satellite borne special sensor microwave imager observations features of high wind frequency hwf over the southern indian ocean are investigated climatology maps show that high winds occur frequently during austral winter located in the open ocean south of polar front in subpolar region warm flank of the subantarctic front between 55 e 78 e and south of cape agulhas where westerly wind prevails the strong instability of marine atmospheric boundary layer accompanied by increased sensible and latent heat fluxes on the warmer flank acts to enhance the vertical momentum mixing thus accelerate the surface winds effects of sea surface temperature sst front can even reach the entire troposphere by deep convection hwf also shows distinct interannual variability which is associated with the southern annual mode sam during positive phase of the sam hwf has positive anomalies over the open ocean south of polar front while has negative anomalies north of the sst front a phase shift of hwf happened around 2001 which is likely related to the reduction of storm tracks and poleward shift of westerly winds in the southern hemisphere

synchronized terrestrial atmospheric deglacial records around the north atlantic on the basis of synchronization of three carbon 14 c 14 dated lacustrine sequences from sweden with tree ring and ice core records the absolute age of the younger dryas preboreal climatic shift was determined to be 11 450 to 11 390 80 years before the present a 150 year long cooling in the early preboreal associated with rising delta 14 c values is evident in all records and indicates an ocean ventilation change this cooling is similar to earlier deglacial coolings and box model calculations suggest that they all may have been the result of increased freshwater forcing that inhibited the strength of the north atlantic heat conveyor although the younger dryas may have begun as an anomalous meltwater event

fennoscandian earthquakes whole crustal rupturing related to postglacial rebound local and regional earthquake locations provide seismic evidence that large shield earthquakes have occurred in northern fennoscandia these paleoearthquakes with fault lengths of up to 160 kilometers and average displacements of up to 15 meters were triggered by nonisostatic compressive stresses caused by the removal of the ice at the end of the last deglaciation the fennoscandian faults were probably formed by single events that ruptured through most of the crust the largest event moment magnitude mw 8 2 was larger than other known stable continent earthquakes outside failed rifts or extended crust

seismic deformation of varved sediments in southern fennoscandia at 7400 cal bp abstract soft sediment deformation structures are preserved in clastic biogenic varves of the lake nurmijarvi sequence from central southern finland deformation structures include centimeter scale folding and faulting structures and larger convolute bedding which are separated from the overlying undisturbed varved section by a turbidite dated at 7400 cal bp the soft sediment deformation provides evidence for postglacial seismic activity ca 3500 years after the deglaciation of the study area by screening the sizes of potential source faults for the event the maximum earthquake moment magnitudes associated with the deformation structures were constrained to mw 5 1 6 9 with realistic 40 rupture scenarios or up to mw 5 1 7 7 if more conservative scenarios are considered the results of the study thus indicate a relatively high magnitude postglacial seismic event in southern finland which adds to the evidence that the postglacial seismic activity was not just restricted to northern fennoscandia but was a more widespread phenomenon the age of the lake nurmijarvi seismic event further demonstrates that high magnitude seismic activity was not restricted to a relatively short period after deglaciation but the period of high magnitude postglacial seismic activity was much longer than previously thought by assessing the orientations of faults that are presently active and using available focal mechanism data our results suggest that strike slip faulting may be a more important mechanism for the generation of both present day and postglacial earthquakes in southern finland than reverse faulting which should further be accounted for in the assessment of long term seismic hazards

evidence of multiple slip events on postglacial faults in northern fennoscandia abstract an analysis of high resolution lidar based digital elevation models dems trenching of quaternary deposits diamond drilling and a structural analysis of the bedrock were conducted in order to characterise the geological structure and to derive full slip profiles of the venejarvi jauhojarvi postglacial fault complex located in northern finland the venejarvi jauhojarvi fault complex consists of 17 surface ruptures striking in a sw ne direction cutting through late weichselian till and traceable for a total distance of 29 9 km based on stratigraphical and structural analysis we show that the naamivitikko fault segment which is part of the venejarvi jauhojarvi complex hosted up to three distinct slip events and it is therefore argued that the prevailing single rupture hypothesis of postglacial faults should be treated with caution based on the measured surface rupture dimensions it is conservatively estimated that the maximum moment magnitude of the paleoseismic event that the complex hosted ranged between mw 5 8 8 4 if uncertainties in the scaling laws equating surface rupture dimensions to moment magnitudes are accounted for a more realistic maximum moment magnitude range between mw 5 8 7 6 is given

the role of eddies in the southern ocean temperature response to the southern annular mode the role of eddies in modulating the southern ocean response to the southern annular mode sam is examined usinganoceanmodelrunatmultipleresolutionsfromcoarsetoeddyresolving thehigh resolution versionsof the model showan increase in eddy kinetic energy that peaks 2 3 yr after a positive anomalyin the sam index previous work has shown that the instantaneous temperature response to the sam is characterized by predominant cooling south of 458s and warming to the north at all resolutions the model captures this temperatureresponse this responseis also evidentin the coarse resolution implementation of the model with no eddy mixing parameterization showing that eddiesdo not play an important role in the instantaneous response on the longer time scales an intensification of the mesoscale eddy field occurs which causes enhanced poleward heat flux and drives warming south of the oceanic polar front this warming is of greater magnitude and occurs for a longer period than the initial cooling response the results demonstrate that this warming is surface intensified and strongest in the mixed layer non eddy resolving models are unable to capturethedelayededdy driventemperatureresponsetothesam theauthorsthereforequestiontheability

the signature of the annular modes in the tropical troposphere the extratropical annular modes are coupled with a distinct pattern of climate anomalies that spans the circulation of the tropical troposphere the signature of the annular modes in the tropical troposphere exhibits a high degree of equatorial symmetry it is associated with upper tropospheric zonal wind anomalies centered about the equator midtropospheric temperature anomalies located 208n and 208s and opposing mean meridional circulation anomalies that span the subtropics of both hemispheres the linkages between the annular modes and the tropical circulation are only evident during the cold season months and are most robust in association with the northern hemisphere annular mode nam the coupling between the annular modes and the circulation of the tropical troposphere is consistent with forcing by waves originating at extratropical latitudes both annular modes are characterized by anomalies in the eddy momentum flux convergence at tropical latitudes that act to reinforce the changes in the tropical wind and temperature fields the most pronounced tropical anomalies lag indices of the annular modes by 2 weeks and are found over the eastern tropical pacific where climatological westerlies permit extratropical waves to propagate into the deep tropics the linkages between the nam and the tropical tropospheric circulation are

deglaciation seismotectonics a principal influence on intraplate seismogenesis at high latitudes abstract in many high latitude stable continental regions deglaciation dominates the current crustal strain field interference between polarised tectonic and radial deglaciation strain fields affects the deviatoric stress state and fault stability margins and in consequence both the levels and properties of seismicity throughout glacial loading and unloading the most notable present day affects of this strain interference are predicted to include alternating quadrants of enhanced seismicity and aseismicity around rebound domes and former peripheral forebulges such strain interference can explain much of the geography and timing of holocene earthquake occurrence across northern europe and eastern north america

surficial geology indicates early holocene faulting and seismicity central sweden in sweden knowledge of the location and timing of glacially induced faulting and seismicity is critical to effective engineering of a long term nuclear disposal facility to improve understanding and modeling of the complex ice induced and tectonic stresses associated with glacially induced faulting field studies detailing the location and timing of movement of such structures are required although the fault has not been confirmed in the bedrock multi proxy surficial geologic evidence indicates that the recently discovered scarp in bollnas is such a structure machine excavated trenches across the scarp reveal landsliding down the scarp and in one location faulted and vertically offset fine grained glacial sediments the presence of water escape structures in trenches excavated on a topographic high strongly suggests a co seismic origin derived from earthquake magnitudes 5 5 numerous landslides in till exist in the region as well four slopes with landslides were examined in detail and the factors of safety for these slopes indicate stable conditions and suggest a seismic trigger basal radiocarbon dates from peat bogs located stratigraphically above the landslides provide minimum limiting ages for the co seismic landslides the oldest date indicates sliding prior to 10 180 calendar years before the present the proposed bollnas fault is 400 km south of the so called lapland fault province to date it is the southernmost confirmed glacially induced fault in sweden the results of this study are consistent with existing modeling results that indicate fault instability in this region of central sweden following deglaciation

synchronous variability in the southern hemisphere atmosphere sea ice and ocean resulting from the annular mode zonally symmetric fluctuations of the midlatitude westerly winds characterize the primary mode of atmospheric variability in the southern hemisphere during all seasons this is true not only in observations but also in an unforced 15 000 yr integration of a coarse resolution r15 coupled ocean atmosphere model here it is documented how this mode of atmospheric variability known as the southern annular mode sam generates ocean circulation and sea ice variations in the model integration on interannual to centennial timescales that are tightly in phase with the sam the positive phase of the sam is associated with an intensification of the surface westerlies over the circumpolar ocean around 608s and a weakening of the surface westerlies farther north this induces ekman drift to the north at all longitudes of the circumpolar ocean and ekman drift to the south at around 308s through mass continuity the ekman drift generates anomalous upwelling along the margins of the antarctic continent and downwelling around 458s the anomalous flow diverging from the antarctic continent also increases the vertical tilt of the isopycnals in the southern ocean so that a more intense circumpolar current is also closely associated with positive sam in addition the anomalous divergent flow advects sea ice farther north resulting in an increase in sea ice coverage finally positive sam drives increases in poleward heat transport at about 308s while decreases occur in the circumpolar region ocean and sea ice anomalies of the opposite sign occur when the sam is negative the ocean and sea ice fluctuations associated with the sam constitute a significant fraction of simulated ocean variability poleward of 308s year round the robustness of the mechanisms relating the sam to oceanic variability suggests that the sam is likely an important source of large scale variability in the real southern hemisphere ocean

isopycnal mixing in ocean circulation models abstract a subgrid scale form for mesoscale eddy mixing on isopycnal surfaces is proposed for use in non eddy resolving ocean circulation models the mixing is applied in isopycnal coordinates to isopycnal layer thickness or inverse density gradient as well as to passive scalars temperature and salinity the transformation of these mixing forms to physical coordinates is also presented

changes in the ocean transport through drake passage during the 1980s and 1990s forced by changes in the southern annular mode 1 we present the first direct evidence that interannual changes in ocean transport through drake passage are forced by variability in the southern annular mode sam this evidence is derived from two decades 1980s and 1990s of subsurface pressure measurements from the tide gauge at faraday station western antarctic peninsula combined with the output of an ocean general circulation model in recent decades the sam has moved toward a higher index state stronger circumpolar winds this trend is not simply monotonic but is the product of a long term change in the seasonality of the sam whilst we cannot address directly the effect of the long term trend on circumpolar transport bottom pressure data from drake passage during the 1990s demonstrate that ocean transport showed the same changes in seasonality as did the sam this offers a mechanism for atmospheric climate change to influence directly the largescale ocean circulation indexterms 4207 oceanography general arctic and antarctic oceanography 4215 oceanography general climate and interannual variability 3309 4532 oceanography physical general circulation 1635 global change oceans 4203 4556 oceanography physical sea level variations citation meredith m p p l woodworth c w hughes and v stepanov 2004 changes in the ocean transport through drake passage during the 1980s and 1990s forced by changes in the southern annular mode geophys res lett 31 l21305 doi 10 1029 2004gl021169

seasonal southern hemisphere multi variable reflection of the southern annular mode in atmosphere and ocean reanalyses variations of southern hemisphere sh climate variables are often linked to the southern annular mode sam variability we examined such linkage by seasons using state of the art atmosphere and ocean sea ice reanalyses the associated sam related anomaly sra fields of the climate variables denoting anomalies corresponding to the same variation in sam are overall consistent across the reanalyses among the atmospheric products 20crv2 differs from era interim and cfsr in the sea level pressure sras over the amundsen sea resulting in less warming over the antarctic peninsula among the ocean reanalyses orap5 and c glors exhibit the largest consistency the major difference between them and the lower resolution cfsr and soda reanalyses is deeper penetration of anomalous meridional currents compared to the other ocean reanalyses cfsr exhibits stronger and spatially more coherent surface current sras resulting in greater sras of sea ice motion and ice thickness along the ice edges the sras of sensible and total surface heat fluxes are reduced in cfsr due to ocean atmosphere coupling significant sea ice concentration sras are present on the west side of peninsulas along the east antarctica coast in spring and winter most notably in orap5 and c glors implying changes in new ice production and shelf water formation most atmosphere and ocean variables manifest an annular sra pattern in summer and a non annular pattern in the other seasons with a wavenumber 3 structure strongest in autumn and weakest in summer the wavenumber 3 structure should be related to the zonal wave three pattern of the sh circulation the relation of which to sam needs further exploration

re examining southern hemisphere westerly wind behavior insights from a late holocene precipitation reconstruction using new zealand fjord sediments abstract the behavior of the southern hemisphere westerly winds sww is inherently linked with climate variability understanding past sww climate feedbacks is key to predicting future climate change however we are limited by a lack of sww reconstructions particularly from the southwest pacific here we examine fjord sediments from fiordland new zealand 44 5 46 5 s to determine how the sww have fluctuated in position and strength in response to regional late holocene climate change and we compare our record to patagonia climate reconstructions in order to evaluate large scale sww behavior sww flow over the southern alps of new zealand drives orographic rainfall that is recorded within fjord sediments as changes in the relative contributions of terrestrial to marine organic matter which can be measured by bulk sediment 13 c and organic c n ratios using these proxies cores from three new zealand fjords show that precipitation decreased between 1400 1100 and 750 150 cal yr bp with short duration shifts toward drier conditions at 1900 and 900 cal yr bp precipitation increased 2100 1400 and 1100 700 cal yr bp with a short interval of wetter conditions around 400 cal yr bp these results indicate that westerly airflow over new zealand was stronger weaker during intervals of relatively warm cool climate our comparison of precipitation reconstructions from fiordland and patagonia shows dissimilarities in sww flow between regions while to date most mechanisms for changing the sww have invoked purely zonal shifts our results suggest that meridional changes in sww flow occurred in addition to zonal shifts in fiordland the meridional airflow associated with sam and or el nino like climate phenomena may be responsible for wet intervals while sam and or la nina like phenomena may promote dry conditions

comparison between hydroacoustical and terrestrial evidence of glacially induced faulting lake voxsjon central sweden the recent availability of a terrestrial high resolution digital elevation model in sweden has led to the discovery of previously unknown scarps believed to be associated with bedrock faults that ruptured to the surface during the holocene field investigations however are required to confirm these findings and determine the timing of post glacial seismicity here we present results from a unique hybrid approach where hydroacoustical data from the sediments of lake voxsjon are compared to stratigraphic and geomorphologic records from nearby terrestrial settings the hydroacoustical data are largely consistent with the terrestrial data indicating a single fault rupture shortly after deglaciation which occurred about 11 000 10 500 cal bp

paleoseismicity and geodynamics in sweden abstract paleoseismicity denotes past pre instrumental earthquakes as recorded by bedrock structures morphological features and sedimentological criteria glacial varves eskers and deltas are excellent records of paleoseismic events data from sweden are presented faults fractures and various types of sedimentary disturbances of late pleistocene and holocene age frequently occur it is concluded that the seismic activity was very intensive in connection with the peak rates of glacial isostatic uplift and that this was a natural effect of the geodynamic processes operating

response of the antarctic circumpolar current to atmospheric variability abstract historical hydrographic profiles combined with recent argo profiles are used to obtain an estimate of the mean geostrophic circulation in the southern ocean thirteen years of altimetric sea level anomaly data are then added to reconstruct the time variable sea level and this new dataset is analyzed to identify and monitor the position of the two main fronts of the antarctic circumpolar current acc during the period 1993 2005 the authors relate their movements to the two main atmospheric climate modes of the southern hemisphere the southern annular mode sam and the el nino southern oscillation enso the study finds that although the fronts are steered by the bathymetry which sets their mean pathway on first order in flat bottom areas the fronts are subject to large meandering because of mesoscale activity and atmospheric forcing while the dominant mode of atmospheric variability in the southern hemisphere sam is relatively symmetric the oceanic response of the fronts is not show

monitoring the transport of the antarctic circumpolar current at drake passage abstract data from an extensive moored instrument array and three hydrographic cruises are used to calculate a time series of the net transport through the upper 2500 m of the drake passage the baroclinic geostrophic transport was monitored with heavily instrumented moorings at each side of the passage pressure gauge measurements at the northern and southern ends of the passage provided a reference speed at 500 m to adjust the relative transport the net transport of the upper 2500 m for the 370 day record ending in january 1980 averaged 121 106 m3 s 1 the total transport through the entire cross sectional area of drake passage is probably between 118 and 146 106 m3 s 1 fluctuations in the relative transport are related to changes in latitude of the northernmost front in the passage the subantarctic front variability of the net transport is coherent with the zonally averaged eastward wind stress

transport and variability of the antarctic circumpolar current in drake passage the baroclinic transport of the antarctic circumpolar current acc above 3000 m through drake passage is 107 3 10 4 sv and has been steady between 1975 and 2000 for six hydrographic sections 1993 2000 along the world ocean circulation experiment woce line sr1b the baroclinic transport relative to the deepest common level is 136 7 7 8 sv the acc transport is carried in two jets the subantarctic front 53 10 sv and the polar front pf 57 5 5 7 sv southward of the acc the southern antarctic circumpolar current transports 9 3 2 4 sv we observe the pf at two latitudes separated by 90 km this bimodal distribution is related to changes in the circulation and properties of antarctic bottom water three realizations of the instantaneous velocity field were obtained with lowered adcps from these observations we obtain near bottom reference velocities for transport calculations net transport due to these reference velocities ranges from 28 to 43 sv consistent with previous estimates of variability the transport in density layers shows systematic variations due to seasonal heating in near surface layers volume transport weighted mean temperatures vary by 0 40 c from spring to summer a seasonal variation in heat flux of about 0 22 pw finally we review a series of papers from the international southern ocean studies program the average yearlong absolute transport is 134 sv and the standard deviation of the average is 11 2 sv the error of the average transport is 15 to 27 sv we emphasize that baroclinic variability is an important contribution to net variability in the acc

kinematics of the pacific equatorial undercurrent an eulerian and lagrangian approach from gcm results abstract three dimensional monthly velocity fields from an ocean general circulation model are used to study the annual mean mass balance of the pacific equatorial undercurrent euc eulerian diagnostics are used to evaluate the various meridional vertical and zonal mass fluxes related to the euc there are several distinct regimes along the equator showing clear asymmetries between the western and eastern parts of the basin and between the northern and southern edges of the euc meridional fluxes are decomposed into pure ekman divergence and geostrophic convergence and it is shown that the asymmetries are mainly related to the spatial structure of the ekman divergence and thus to that of the trade winds lagrangian calculations are used to evaluate accurately the mass transfers between various sections of the euc and between the euc domain and the tropics the authors show that geostrophic convergence only ventilates the upper layers of the euc and that the euc really is a tongue of water flowing

an interpretation and catalogue of paleoseismicity in sweden abstract paleoseismic data provide a long term record of seismic activity to predict hazards for periods longer than one to a few centuries in sweden the analysis reveals there was a drastic change in dominant seismic mode from a high to super high deglacial mode to a low to moderately low mode in present and late holocene time paleoseismic criteria and characteristics include numerous different sources of information viz primary faults bedrock deformation sedimentary deformation rock and sediment slides liquefaction sorting by shaking tsunamis differing geomorphic expressions disordering and ordering of magnetic particles by applying multiple criteria it was possible to identify 44 paleoseismic events including 23 events of estimated m 6 7 12 events of m 7 8 and 6 events of m 8 varve dating often allows a precision as to a single year in one case even to the season of a year the key for paleoseismic reconstruction and testing is the application of multiple criteria

circumpolar response of southern ocean eddy activity to a change in the southern annular mode 1 analysis of satellite altimeter data reveals anomalously high eddy kinetic energy eke in the antarctic circumpolar current acc during the period 2000 2002 around 2 3 years earlier 1998 the circumpolar eastward wind stress as quantified by the southern annular mode sam showed a significant positive peak and we have shown previously that the acc peaked around 1998 in response an eddy resolving ocean model is used to investigate the delay between wind forcing and the eddy response and demonstrates that the lag is due to the time taken to influence the deep circulation of the acc winds over the southern ocean have shown a strong climatic increase over the past few decades if this increase in winds is also reflected as an increase in eddy activity as our analysis suggests it might then the increased poleward heat flux may have played a significant role in the observed warming of the southern ocean citation meredith m p and a m hogg 2006 circumpolar response of southern ocean eddy activity to a change in the southern annular mode geophys res lett 33 l16608 doi 10 1029 2006gl026499

a review of the history of the baltic sea 13 0 8 0 ka bp abstract the dynamic history of the baltic sea during the millennia following the last deglaciation has been one of the main topics for many generations of quaternary geologists around the baltic sea based on the present state of knowledge and certain hypotheses a model for the development during the baltic ice lake yoldia sea and ancylus lake stages are presented the oresund strait was the threshold of the initial stage of the baltic ice lake and was eroded down to bedrock as a result of the isostatic uplift the emerging threshold forced the baltic ice lake to rise above sea level at ca 12 0 ka bp this gradual up damming ended at ca 11 2 ka bp when the large glacial lake was lowered 5 10m by possible subglacial drainage at mt billingen a glacial readvance during the younger dryas ended a ca 400 year long land bridge between sweden and the continent by blocking the former drainage route once again the baltic ice lake had to rise above sea level to be drained over the oresund strait at ca 10 5 ka bp a gradual ice recession began and 200 years later when the receding ice sheet could not withhold the up dammed water masses the final drainage of the baltic ice lake occurred which rapidly lowered the water level within the baltic basin with ca 25 m and ended the baltic ice lake stage the next stage the yoldia sea was characterized by a complex pattern of relative sea level changes with large differences within the baltic basin a very restricted baltic sea in the south and thus an extensive landbridge at ca 9 9 ka bp a short 100 200 years saline ingression is seen in the baltic sediment records from stockholm in the north to the southernmost parts of the yoldia sea the gradually shallower strait in south central sweden the narke strait ended the saline influence 300 400 years later the two remaining outlets west of lake vanern gota alv and otteid steinselva had become too shallow to swallow the outflowing yoldia sea waters at this stage the baltic lake vanern level could thus not fall in pace with the relative sea level fall outside the outlet areas this was the isolation of lake vanern and the baltic from the sea and the beginning of the ancylus lake since the water depth of the larger gota alv outlet had to be more or less maintained the ancylus lake level had to rise in pace with the uplift of the outlet region this caused a significant and rapid transgression 10 30 m in ca 300 years in the southern baltic which flooded large areas with recently immigrated pine forests since the oresund strait during the yoldia sea stage had been uplifted more than southerly areas the ancylus transgression ended with a new drainage pathway at ca 9 2 ka bp through the darss sill area in the southern baltic and northwards through the store belt strait this so called dana river had cut off the former large land bridge the quaternary deposits of this new threshold were eroded and a fairly rapid regression set in at ca 9 0 ka bp the dana river had eroded down to the sea level which isolated lake vanern from the ancylus lake and created a land bridge between southern sweden and northwards ca 800 years later when the sea level rose above the oresund threshold marine water could enter the baltic and at ca 8 0 ka bp brackish water characterized the southern baltic this marks the end of the ancylus lake

north german zechstein facies patterns in relation to their substrate an attempt was made to relate the early zechstein facies distribution to the zechstein substrate comparable developments in the hessian trough and along the lower rhine embayment allow for the assumption that the creation of depocenters in the weser ems area are governed by interrelated late saalic tectonic pulses due to differences in the architecture and mobility of the substrate variations in the depositional model must be assumed

carbonates and relative changes in sea level abstract in the geologic record some of the most accurate gauges of changes in sea level are the sediment type geometry and diagenesis of carbonate shelves and platforms this is because carbonates frequently occur at or very near sea level and are usually less compacted than siliciclastics world wide changes in relative sea level the sum of eustatic sea level changes sedimentation and crustal movements have occurred repeatedly and cyclicly through geologic time producing characteristic responses in carbonates 1 1 relative rises in sea level usually caused by the cumulative effect of tectonic subsidence and eustatic rise may result in the following 1 1 a drowned carbonate reefs or platforms here carbonate growth potential is exceeded by relative sea level rise and is characterized by shallow water sediments overlain by hardgrounds and or deep water sediments some of which may be condensed sequences 1 2 b platforms where only the fast growing rim and patches of the interior are able to match sea level rise while the remainder of the platform is drowned temporarily 1 3 c platforms which keep up and maintain a flat top at sea level and contain shallow water sediments whose thickness at the least matches the height of the sea level rise if terrigenous supply is limited prograding sheets of shelf carbonate occur frequently capped by supratidal evaporites with prograding shelf margin carbonate clinoforms and turbidites if terrigenous supply is high the shelf carbonates encroach on deltaics 2 2 relative drops in sea level caused by crustal uplift or by subsidence being outpaced by a eustatic drop in sea level cause karst and soil development over shelves and platforms deposition of deep water evaporites in adjacent semi enclosed basins and in open marine basins the deposition of deltaic and aeolian clastics that bypassed the shelf falls are accompanied by platform wide fresh water diagenesis during relative sea level rises marine diagenesis is common in the subtidal portions of the shoaling upward carbonates and fresh water diagenesis and dolomitization and sulphate deposition is common in their intertidal and supratidal portions the stratigraphic significance of these reponses to relative sea level change is that many are tied to eustatic events and so are predictable within a basin of deposition

the variability of the atlantic meridional overturning circulation the north atlantic oscillation and the el nino southern oscillation in the bergen climate model abstract the link between the interannual to interdecadal variability of the atlantic meridional overturning circulation amoc and the atmospheric forcing is investigated using 200 yr of a control simulation of the bergen climate model where the mean circulation cell is rather realistic as is also the location of deep convection in the northern north atlantic the amoc variability has a slightly red frequency spectrum and is primarily forced by the atmosphere the maximum value of the amoc is mostly sensitive to the deep convection in the irminger sea which it lags by about 5 yr the latter is mostly forced by a succession of atmospheric patterns that induce anomalous northerly winds over the area the impact of the north atlantic oscillation on deep convection in the labrador and greenland seas is represented realistically but its influence on the amoc is limited to the interannual time scale and is primarily associated with wind forcing the tropical pacific shows a strong variability in the model

postglacial reactivation of the suasselka pgf complex in sw finnish lapland the suasselka fault complex is recognized from high resolution digital elevation models lidar dems as a complex of 37 surface ruptures striking sw ne and cutting through weichselian glacial sediments confirming the postglacial nature of the rupturing event the analysis of lidar dems geophysical profiles and trenching of glacial sediments at two sites along the suasselka postglacial fault pgf system has provided evidence of earthquakes that post and predate the late weichselian deglaciation at the suaspalo trenching site at least two different rupture events are observed the first one predates the deposition of the lowermost till unit and potentially dates to the early or even pre weichselian the second rupture event on the other hand deforms overlying tills and is thus a post weichselian event our results indicate that multiple rupturing events can take place within postglacial fault complexes which is the second time such a characteristic has been proven for pgfs in northern fennoscandia furthermore the present results provide the first evidence of either early or even pre weichselian faulting in finland suggesting that the same fault complexes were also active after glacial phases that predated the last glacial maximum of the late weichselian these results warrant re evaluation of the long term seismic risk associated with the faults as the assumption of single rupture events is erroneous considering that the suasselka pgf complex is composed of four pgf systems and 37 isolated 150 7500 m long segments we calculated the potential moment magnitudes based on the rupture length and mean maximum vertical displacement for each individual segment and system taken that they potentially ruptured independently and finally for the entire suasselka pgf complex for the entire complex rupturing in a single event the observed displacement and length of the complex yields a moment magnitude estimate of mw 6 7 8 1 however based on geomorphological and sedimentological evidence we believe that this is a conservative estimate of the moment magnitude of the paleoearthquake if isolated pgf systems are considered to have ruptured individually the moment magnitudes estimated based on surface rupture lengths range from mw 5 5 6 7 and based on mean and maximum cumulative displacement values the estimated values range from mw 6 2 7 3 and mw 6 7 8 0 respectively as we cannot with the available data distinguish the exact number of events the age of events or which segments potentially ruptured at the same time we conclude that the events that took place in the complex ranged in moment magnitude from c mw 5 5 to 8 1 the mw 8 1 estimate representing conservative upper bound for the maximum moment magnitude

mechanisms of hemispherically symmetric climate variability inspired by paleoclimate evidence that much past climate change has been symmetric about the equator the causes of hemispherically symmetric variability in the recent observational record are examined using the national centers for environmental prediction national center for atmospheric research reanalysis dataset and numerical models it was found that the dominant cause of hemispherically symmetric variability is the el nino southern oscillation during an el nino event the tropics warm at all longitudes and the subtropical jets in both hemi spheres strengthen on their equatorward flanks poleward of the tropical warming there are latitude belts of marked cooling extending from the surface to the tropopause in both hemispheres at all longitudes and in all seasons the midlatitude cooling is caused by changes in the eddy driven mean meridional circulation changes in the transient eddy momentum fluxes during an el nino event force upper tropospheric ascent in midlatitudes through a balance between the eddy fluxes and the coriolis torque the eddy driven ascent causes anomalous adiabatic cooling which is primarily balanced by anomalous diabatic heating using a quasigeostrophic spherical model forced by an imposed surface eddy disturbance of chosen wave number and frequency it is shown that the anomalous eddy momentum fluxes are caused by the impact that the changes in the tropically forced subtropical jets have on the propagation in the latitude height plane of transient eddies changes in zonal winds and associated changes in the meridional gradient of potential vorticity create an anomalous region of low meridional wavenumber in the midlatitudes that refracts waves away both poleward and equatorward tropical forcing of variability in the eddy driven mean meridional circulation is another way in addition to rossby wave teleconnections whereby the tropics can influence extratropical climate unlike teleconnections this mechanism causes climate variability that has strong zonally and hemispherically symmetric components and operates throughout the seasonal cycle

volume transport of the antarctic circumpolar current from bottom pressure measurements abstract meausrements from bottom pressure gauges located at the north and south sides of drake passage are used to extend the one year time series of volume transport of the antarctic circumpolar current acc given previously by whitworth a small error in that paper is corrected and a revised transport time series is presented which shows the importance of including the transport in the northern and southern margins of drake passage direct measurements of vertical shear averaged across the passage are in good agreement with geostrophic shear and suggest that the acc is in geostrophic balance although most of the acc transport is in the baroclinic field transport fluctuations are mainly barotropic transport estimates based on pressure difference alone differ from the estimates of whitworth by less than 10 106 m3 s 1 fluctuations in transport of almost half of the mean value occur over periods as short as two weeks