regional patterns of sea level change related to interannual variability and multidecadal trends in the atlantic meridional overturning circulation some studies of ocean climate model experiments suggest that regional changes in dynamic sea level could provide a valuable indicator of trends in the strength of the atlantic meridional overturning circulation moc this paper describes the use of a sequence of global ocean ice model experiments to show that the diagnosed patterns of sea surface height ssh anomalies associated with changes in the moc in the north atlantic na depend critically on the time scales of interest model hindcast simulations for 1958 2004 reproduce the observed pattern of ssh variability with extrema occurring along the gulf stream gs and in the subpolar gyre spg but they also show that the pattern is primarily related to the wind driven variability of moc and gyre circulation on interannual time scales it is reflected also in the leading eof of ssh variability over the na ocean as described in previous studies the pattern however is not useful as a fingerprint of longer term changes in the moc as shown with a companion experiment a multidecadal gradual decline in the moc of 5 sv 1 sv 106 m3 s 1 over 5 decades induces a much broader basin scale ssh rise over the mid to high latitude na with amplitudes of 20 cm the detectability of such a trend is low along the gs since low frequency ssh changes are effectively masked here by strong variability on shorter time scales more favorable signal to noise ratios are found in the spg and the eastern na where a moc trend of 0 1 sv yr 1 would leave a significant imprint in ssh already after about 20 years

seismic guided waves trapped in the fault zone of the landers california earthquake of 1992 a mobile seismic array of seven stations was deployed at 11 sites along the fault trace of the m7 4 landers earthquake of june 28 1992 with a maximum offset of 1 km from the trace we found a distinct wave train with a relatively long period following the s waves that shows up only when both the stations and the events are close to the fault trace this wave train is interpreted as a seismic guided wave trapped in a low velocity fault zone to study the distribution of amplitude of the guided waves with distance from the fault trace and also their attenuation with travel distance along the fault zone we eliminated source and recording site effects by the coda normalization method the normalized amplitudes of guided waves show a spectral peak at 3 4 hz which decays sharply with distance from the fault trace spectral amplitudes at high frequencies 8 15 hz show an opposite trend increasing with distance from the fault trace the normalized amplitudes of guided waves at 3 4 hz also show a systematic decrease with hypocentral distance along the fault zone from which we infer an apparent q of 50 in order to confirm the existence of the guided waves a dense array of 31 stations was deployed at one of the 11 sites the resultant records revealed unequivocal evidence for the existence of guided waves associated with the fault zone by modeling the waveforms as s waves trapped in a low velocity waveguide sandwiched between two homogeneous half spaces with velocity vs 3 0 km s we infer a waveguide width of about 180 m a shear velocity of 2 0 2 2 km s and a q of 50 hypocenters of aftershocks with clear guided waves show a systematic distribution both laterally and with depth delineating the extent of the low velocity fault zone in three dimensions we find that the zone extends to a depth of at least 10 km this zone apparently continues to the south across the pinto mountain fault because guided waves are observed at stations north of the pinto mountain fault for earthquakes with epicenters south of it on the other hand the zone appears to be discontinuous at the fault bend located about 20 km north of the mainshock epicenter guided waves were observed for stations and epicenters which are located on the same sides of the fault bend but not for those on the opposite sides

the heterogeneous upper mantle low velocity zone abstract the upper mantle low velocity zone lvz is a depth interval with slightly reduced seismic velocity compared to the surrounding depth intervals the zone is present below a relatively constant depth of 100 km in most continental parts of the world both in cratonic areas with high average velocity and tectonically active areas with low average velocity evidence for the low velocity zone arises from controlled and natural source seismology including studies of surface waves and of primary and multiple reflections of body waves from the bounding interfaces calculations of receiver functions and absolute velocity tomography the available data indicates a more pronounced reduction in seismic velocity and q value for s waves than p waves as well as high electrical conductivity in the lvz seismic waves are strongly scattered by the zone which demonstrates the existence of small scale heterogeneity the depth to the base of the lvz is systematically shallower in cold stable cratonic areas than in hot active regions of the world because of its global occurrence below a relative constant depth of 100 km the lvz cannot be explained by metamorphic or compositional variation and rheological changes calculated upper mantle temperatures indicate that the rocks are close to the solidus in an interval with variable thickness below 100 km depth provided that the rocks contain water and carbon dioxide the presence of even small amounts of such fluids in the mantle rocks will lower the solidus by several hundred degrees and introduce a characteristic kink on the solidus curve around 80 100 km depth the seismic velocities and q values are significantly reduced of rocks which are close to the solidus or contain small amounts of partial melt hence the lvz may be explained by upper mantle temperatures being close to the solidus in a depth interval below 100 km assuming that the rocks contain only limited amounts of fluids this mechanism may explain the low velocities q values and resistivity as well as the intrinsic scattering and the characteristic variation in thickness of the low velocity zone

persistent solar influence on north atlantic climate during the holocene surface winds and surface ocean hydrography in the subpolar north atlantic appear to have been influenced by variations in solar output through the entire holocene the evidence comes from a close correlation between inferred changes in production rates of the cosmogenic nuclides carbon 14 and beryllium 10 and centennial to millennial time scale changes in proxies of drift ice measured in deep sea sediment cores a solar forcing mechanism therefore may underlie at least the holocene segment of the north atlantic9s 1500 year cycle the surface hydrographic changes may have affected production of north atlantic deep water potentially providing an additional mechanism for amplifying the solar signals and transmitting them globally

origin chronology and environmental significance of holocene aeolian and alluvial sands at blue mountain falkland islands extensive and thick sand accumulations containing organic rich horizons at blue mountain falkland islands are most probably derived from weathering of local bedrock under late pleistocene periglacial conditions weathering and subsequent deflation produced several shallow basins that are now occupied by lakes sand morphology sedimentary structures and site characteristics indicate that the sand deposits are predominantly aeolian although some alluvial sands are also present deflation occurred either before the lakes existed or at times of lower lake levels sixteen 14c dates from organic rich horizons show that some sand accumulated in the early holocene or late pleistocene but that most is of mid to late holocene age landscape stability instability phases were not synchronous between sites and cannot be explained by the regional trends of holocene climate change a period of significantly lower lake levels and major aeolian erosion at c 5000 4500 bp is proposed but is not supported by regio

location of the carlsberg fault zone from seismic controlled source fan recordings 1 we locate the concealed carlsberg fault zone in the city of copenhagen from seismic fan recordings the fault is part of a fault system close to the border between the danish basin and the baltic shield recent earthquakes indicate that this area is tectonically active the fault zone is a seismic low velocity zone fan shots were recorded on three receiver arrays 1 5 2 4 km long arcs across the fault sources were placed inside and up to 500 m away from the 400 700 m wide fault zone at offsets of up to 7 km shots inside the fault zone show 1 weak delayed first arrivals inside the fault zone 2 stronger first arrivals outside the fault zone 3 guided waves inside the fault zone the fault is a shadow zone for shots detonated outside the fault zone our approach facilitates fault mapping in densely urbanized areas where seismic profiling is not feasible

stone run block stream formation in the falkland islands over several cold stages deduced from cosmogenic isotope 10be and 26al surface exposure dating cosmogenic isotope 10be and 26al surface exposure dating has been applied to valley axis and hillslope stone runs relict periglacial block streams and their source outcrops in the falkland islands south atlantic the data indicate that stone runs are considerably older landforms than previously envisaged and afford no evidence that they are a product of the last glacial maximum the samples range in apparent 10be age from 42k to 731k yr bp but some of these are minima the results indicate that valley axis stone runs may be up to 700 800k yr old have simple exposure histories and are composite landforms that developed over several cold stages analyses of some hillslope and outcrop samples also demonstrate simple exposure histories with 10be ages from 42k to 658k yr bp in contrast isotopic ratios from other hillslope and outcrop samples reveal they have had a complex exposure history involving periods of burial or shielding the samples range in 10be age from 59k to 569k yr bp and these are regarded as minimum age estimates larger stone runs may be older than smaller runs and there is a possibility that stone runs older than 800k yr exist in other parts of the falklands the assertion that glaciation in the falklands was restricted to the highest uplands is supported by the data and the potential for age determination of other boulder strewn and bedrock landforms using cosmogenic isotope analysis in order to extend the geochronology of quaternary events and processes is noted

holocene glacier fluctuations in south america and antarctica abstract glacial geologic evidence indicates that glaciers throughout the andes and antarctica fluctuated during the holocene radiocarbon dating and other age determinations suggest that glaciers readvanced significantly only during the last 5 ka reaching positions from several 100 m to a few kilometres beyond their present limits in south america tenuous evidence from radiocarbon dates with dendrochronological data and environmental interpretations from pollen analyses indicate four main periods of neoglacial advance culminating 5000 4000 bp 3000 2000 bp 1300 1000 bp and 15th late 19th centuries smaller advances may have occurred at ca 8400 bp ca 7500 bp and ca 6300 bp the meagre data are consistent in indicating broad synchrony throughout the andes during the last 5 ka suggesting response to global climatic changes anomalies exist in patagonia where some tide water glaciers reached their maximal holocene limits recently this century the broad spectrum of differing antarctic environments produces interesting contrasts some local glaciers in the mcmurdo sound area of the east artarctic continent are more extensive now than during the global glacial maximum ca 18 ka bp when they were starved of precipitation consistent agreement among 14 radiocarbon dates from the south shetland islands indicates two main holocene glacier advances the most extensive 2 3 km peaking in the 12th century the other culminating in the 18th 19th century glaciers in south georgia reached their most advanced holocene limits before 2200 bp moraine fjord glacier which culminated as a 6 km advance between 1460 1700 radiocarbon bp may have lagged 400 650 years behind the climatic forcing because it could only advance in its deep water fjord by building a moraine bank smaller advances in south georgia culminated in the 17th 19th centuries and during the 1920s 30s there is no firm evidence of glacier advances before 3 ka bp in the southern ocean sub antarctic domain but broad synchrony in glacier advances during the last ca 3000 years appears to have occurred throughout the andes antarctic transect caution is required in the interpretation and correlation of moraines associated with calving glaciers and of those with poorly constrained dating

palaeoclimates in central and south america since 18 000 bp based on pollen and lake level records abstract the last 18 ka of palaeoclimates are discussed at 3 ka intervals based on palaeoenvironmental changes shown in pollen and lake level records from central and south america a total of 61 pollen records fulfill the requirements of continuity and chronology to be used in this synthesis 8 records from tropical and subtropical lowlands in central and south america 7 records from the central american highlands 26 records from the high andes north and south of the equator 2 records from the southern subtropics and 18 from the southern andes and subantarctic islands palaeoclimatic interpretation of the pollen records is semiquantitative based on bioclimatic parameters such as e g elevational temperature gradients or latitudinal precipitation gradients that can be related to vegetation zonation additional palaeoclimatic information is obtained from lake level records derived either from dated shorelines or from the limnological history of lake sediment sections large scale palaeoclimatic comparison of the proxy data records indicates that full and late glacial climates throughout central and south america were cooler than today by about 4 to 5 c but that moisture patterns showed regional differentiation thus in both the southern subtropics and high latitudes in southern chile conditions were substantially moister than today during full and late glacial times whereas everywhere else conditions were far drier than today in terms of palaeocirculation this scenario can be interpreted as a poleward shift of the subtropical as well as the westerly circulation a scenario that has been suggested by palaeoclimatic simulations from general circulation models gcm another major palaeoclimatic aspect predicted by the gcm simulations is the suppressed early holocene summer monsoon in the southern subtropics although proxy records are few from this zone their palaeoenvironmental history during that time shows a period of aridity that would support the model one of the most controversial aspects of south american palaeoclimates concerns the existence of a younger dryas equivalent a cold period between 11 and 10 ka bp based on the existing data from south america that show a great diversity of palaeoclimatic trends the concept of an interval that is characterized by the same climatic signal as documented for the north atlantic seems too simplistic moreover at this point only very few records have been analysed in sufficient detail to yield unambiguous climatic information for the interval in question the principal outcome of this palaeoenvironmental and palaeoclimatic synthesis is the better understanding of the type and quality of data available at present and the realization of regions and periods where much more and concerted effort is needed to address problems of intra and interhemispheric palaeoclimatic correlations only then can questions concerning the mechanism of climatic change be tackled successfully

sand veins and wedges in cold aeolian environments sedimentary structures formed by the progressive primary infilling of thermal contraction cracks with sand are termed primary sand veins and sand wedges in addition to simple vein or wedge shapes irregularities can be caused by sand veins branching from their sides and toes primary sand wedges form widely in sandy polar deserts locally in sandy areas of tundra and probably in seasonally frozen ground there are no unique criteria for distinguishing primary sand veins and wedges from sand veins and wedges of other origins identification of the former depends on the occurrence of distinctive features not always present and on evaluation of their lithofacies and palaeoenvironmental contexts care and caution are advocated in the use of ancient relict primary sand veins and wedges as quantitative palaeoenvironmental indicators because modern active wedge distribution is poorly known and hence inferred thermal climatic threshold values are questionable it is suggested that ancient relict primary sand wedges exceeding 2 m in depth and with well developed vertical lamination probably indicate the former occurrence of continuous permafrost whereas sand veins and narrow sand wedges frost cracks are potentially ambiguous as they may form not only in the active layer above and within continuous permafrost but also in seasonally frozen ground in non permafrost areas

the little ice age and medieval warm period in the sargasso sea sea surface temperature sst salinity and flux of terrigenous material oscillated on millennial time scales in the pleistocene north atlantic but there are few records of holocene variability because of high rates of sediment accumulation holocene oscillations are well documented in the northern sargasso sea results from a radiocarbondated box core show that sst was approximately 1 degree c cooler than today approximately 400 years ago the little ice age and 1700 years ago and approximately 1 degree c warmer than today 1000 years ago the medieval warm period thus at least some of the warming since the little ice age appears to be part of a natural oscillation 39 refs 4 figs 1 tab

can long term variability in the gulf stream transport be inferred from sea level recent studies by sturges and collaborators suggest a simple but powerful technique to estimate climatic changes in the transport of the gulf stream from the difference between the oceanic sea level calculated with a simple wind driven rossby wave model and the observed coastal sea level the hypothesis behind this technique is tested using 40 years of data 1950 to 1989 obtained from a three dimensional atlantic ocean model forced by observed surface data the analysis shows that variations in sea level difference between the ocean and the coast are indeed coherent with variations of the gulf stream transport for periods shorter than 1 year or longer than 4 5 years the results obtained from the three dimensional model confirm the findings of the simple rossby wave model that decadal climatic changes in the gulf stream transport vary considerably with latitude

persistent positive north atlantic oscillation mode dominated the medieval climate anomaly the medieval climate anomaly mca was the most recent pre industrial era warm interval of european climate yet its driving mechanisms remain uncertain we present here a 947 year long multidecadal north atlantic oscillation nao reconstruction and find a persistent positive nao during the mca supplementary reconstructions based on climate model results and proxy data indicate a clear shift to weaker nao conditions into the little ice age lia globally distributed proxy data suggest that this nao shift is one aspect of a global mca lia climate transition that probably was coupled to prevailing la nina like conditions amplified by an intensified atlantic meridional overturning circulation during the mca

fluvial aeolian interactions part i modern systems two modern fluvial aeolian depositional systems great sand dunes national monument colorado and the mojave river wash california are remarkably similar in spite of different climates sizes fluvial sediment textures and relative directions of aeolian and fluvial transport dune growth and migration and deflation of blowouts create 8 10 m of local relief in unflooded aeolian landscapes there are six prominent fluvial aeolian interactions 1 fluvial flow extends into the aeolian system until it is dammed by aeolian landforms 2 interdune areas overbank interdunes upstream of aeolian dams and alongside channels are flooded 3 water erodes dunes alongside channels and interdunes 4 flood waters deposit sediment in interdune areas 5 fluvially derived groundwater floods interdunes interdune playas 6 wind erodes fluvial sediment and redeposits it in the aeolian system unique and characteristic sediments are deposited in overbank interdunes and in interdune playas reflecting alternate fluvial and aeolian processes and rapidly changing flow and salinity conditions these fluvial aeolian interdune deposits are characterized by irregular concave up bases and flat upper surfaces containing mudcracks or evaporite cement characteristic low relief surfaces form in aeolian systems as an effect of flooding fluvial deposits are resistant to aeolian deflation aeolian sand is preserved when flood sediments are deposited around the bases of the dunes thus repetitive fluvial and aeolian aggradation tends to be stepwise as interdune floors are suddenly raised during floods the effects of flooding should be easy to recognize in ancient aeolianites even beyond the area covered with overbank muds

quaternary glaciations of the southern andes abstract the southern andes comprise the southernmost portion of the andean cordillera beginning at the edge of the puna altiplano lat 27 s and ending at isla de los estados lat 55 s the late cainozoic glacial record of these mountains spans the interval from the late miocene to the present and is one of the most complete to be found anywhere in the world this has arisen for several reasons i the conterminous mountain ice cap extended to the piedmont zone on both flanks of the range where the sedimentary and morphological record has been well preserved ii periodic volcanism mainly from monogenetic fissure eruptions of basalt east of the range and from central tephra producing cones along the mountain crest has provided opportunity for the preservation and radiometric dating of interbedded glacial deposits iii a tectonically induced interval of stream incision in the mid pleistocene and simultaneous uplift has preserved glacial sediments on interfluves iv in the chilean lakes region west of the mountains late quaternary glaciers terminated in a well vegetated landscape thus creating scope for radiocarbon dating of interbedded and incorporated organic materials consequently the last glaciation in the llanquihue area of chile is one of the best dated sequences in south america thus the llanquihue glaciation is proposed as the south american equivalent of the wisconsin and weichsel glaciations of north america and north west europe respectively

fine structure of p wave velocity distribution along the atotsugawa fault central japan abstract a seismic experiment with five explosive sources and 396 seismic stations was conducted in august 2005 in the atotsugawa fault area central japan the 396 seismic stations were located on a survey line with a length of 47 km the profile line was located along the atotsugawa fault the average spacing of the seismic stations was about 119 m the spatially high density linear array was used to reveal the seismic structure of the fault zone the fine structure along the atotsugawa fault was obtained at depths shallower than 6 km a large lateral variation of p wave velocity which was consistent with the geological structure was found at the shallowest layer the heterogeneous variation with a velocity range of 5 7 km s 6 2 km s was obtained at the second layer the second layer was divided into three parts the western part of the research area was determined to be high velocity the low velocity area was detected at the central part at the east end of the profile line the p wave velocity was higher than that of the central part the low velocity area coincided with a low seismicity area the depth section of the reflection profile showed a boundary located at a depth of around 13 km the boundary was roughly consistent with the cut off depth of the seismicity of the microearthquakes the high seismic activity area was characterized to be reflective

distribution of modern salt marsh foraminifera in the albemarle pamlico estuarine system of north carolina usa implications for sea level research abstract we described the distributions of foraminifera from ten physiographically distinct salt marshes in the albemarle pamlico estuarine system north carolina using 193 surface samples we defined elevation dependent ecological zones at individual sites using cluster analysis and detrended correspondence analysis additionally seven principal biozones of salt marsh foraminifera were identified that have distinctive spatial distributions reflecting a pattern of salinity regimes caused by the current configuration of barrier island inlets high salinity sites along the southern outer banks are associated with sub tidal calcareous assemblages low marshes dominated by miliammina fusca and high marsh environments defined by haplophragmoides wilberti trochammina inflata and arenoparrella mexicana in contrast lower salinity marshes have ammobaculites spp in sub tidal settings miliammina fusca dominated low marshes and high marsh settings characterized by jadammina macrescens spatial variation of foraminiferal populations and the potential for biozones to migrate in response to changing inlet configuration and salinity suggests that datasets of modern salt marsh foraminifera from multiple environments would be appropriate for reconstructing holocene relative sea level in north carolina

barrier island response to late holocene climate events north carolina usa the outer banks barrier islands of north carolina usa contain a geologic record of inlet activity that extends from ca 2200 cal yr bp to the present and can be used as a proxy for storm activity optically stimulated luminescence osl dating 26 samples of inlet fill and flood tide delta deposits recognized in cores and geophysical data provides the basis for understanding the chronology of storm impacts and comparison to other paleoclimate proxy data osl ages of historical inlet fill compare favorably to historical documentation of inlet activity providing confidence in the technique comparison suggests that the medieval warm period mwp and little ice age lia were both characterized by elevated storm conditions as indicated by much greater inlet activity relative to today given present understanding of atmospheric circulation patterns and sea surface temperatures during the mwp and lia we suggest that increased inlet activity during the mwp responded to intensified hurricane impacts while elevated inlet activity during the lia was in response to increased nor easter activity a general decrease in storminess at mid latitudes in the north atlantic over the last 300 yr has allowed the system to evolve into a more continuous barrier with few inlets

a relationship between dunes fire and climate recorded in the holocene deposits of quebec during the past 5 000 yr bp the tropics have experienced an increase in aridity and aeolian activity in both maritime and continental areas1 4 in contrast the onset and subsequent development of post hypsithermal climates in northern latitudes were primarily conducive to global cooling it is suggested here that aeolian activity in cold environments represents a direct response to this long term cooling trend that began after 6 000 5 000 yr bp at the end of the climatic optimum5 9 this study establishes the holocene chronology of sand dunes near the outer forest limit in northern quebec fig 1 i show here that fires initiate the aeolian activity and that the fire dune relationship is typical of cooling period on this basis a palaeoclimatic reconstruction since the climatic optimum is proposed

gulf stream density structure and transport during the past millennium the gulf stream transports approximately 31 sv 1 sv 10 6 m 3 s 1 of water and 1 3 10 15 w of heat into the north atlantic ocean the possibility of abrupt changes in gulf stream heat transport is one of the key uncertainties in predictions of climate change for the coming centuries given the limited length of the instrumental record our knowledge of gulf stream behaviour on long timescales must rely heavily on information from geologic archives here we use foraminifera from a suite of high resolution sediment cores in the florida straits to show that the cross current density gradient and vertical current shear of the gulf stream were systematically lower during the little ice age ad 1200 to 1850 we also estimate that little ice age volume transport was ten per cent weaker than today s the timing of reduced flow is consistent with temperature minima in several palaeoclimate records implying that diminished oceanic heat transport may have contributed to little ice age cooling in the north atlantic the interval of low flow also coincides with anomalously high gulf stream surface salinity suggesting a tight linkage between the atlantic ocean circulation and hydrologic cycle during the past millennium

late pleistocene sediments and environmental change at plaza creek falkland islands south atlantic late pleistocene organic rich sediments exposed in coastal bluffs near the head of plaza creek east falkland have yielded conventional and ams 14c dates of between 36 and 28 ka bp and possess a pollen spectrum dominated by grasses indicating a vegetation assemblage similar to that of the present day although some sample dates are anomalous and contamination by non contemporaneous carbon cannot be ruled out entirely the age estimates are consistent with evidence and dates from antarctica south america and the amphi north atlantic for climate shifts to interstadial conditions at around that time the organic rich units are developed in and enclosed by deposits attributed to processes of periglacial mass wasting grain size characteristics suggest that these sediments may have been emplaced by solifluction shallow translational landsliding and surface wash in at least five mass wasting episodes some of the mass wasting sediments might correlate with solifluction deposits above and below a podsolic soil dated to 26 ka bp at san carlos east falkland and with periods of cirque and valley glaciation identified in the uplands of the falkland islands the similarity between late pleistocene interstadial holocene and present day pollen assemblages and the lack of vegetation change within these periods is characteristic of most cool temperate southern ocean islands and may reflect the lack of sensitivity of the vegetation to climate change and or a lack of climate variability for the time intervals covered 1998 john wiley sons ltd

late pleistocene and holocene landscape evolution and environmental change in the lake sulivan area falkland islands south atlantic abstract late pleistocene and holocene landscape evolution around lake sulivan falkland islands south atlantic is assessed using morphological stratigraphical palaeoecological and 14c dating evidence data indicate a complex landscape history involving frost related activity ventifact development growth and degradation of peat terrain expansion and contraction of lakes and the development stabilisation and subsequent reworking of alluvial and aeolian sand bodies late pleistocene cold conditions favoured production of sandy diamicts on hillslopes and ventifacts on outcrops and blockfield clasts lateglacial climatic amelioration was marked by early growth of peat ca 16 500 cal yr bp since then peat accumulation changes in lake areas and depths and alluvial and or aeolian sand deposition have been recurring and dominant features of landscape change which throughout the late pleistocene and early holocene may have been a response to near synchronous climatic fluctuations along the south america antarctica axis marked landscape changes around lake sulivan coincided with intervals of glacier readvance in south america and south georgia at ca 3200 1900 and 700 100 cal yr bp with lower lake levels and aeolian sand transport from exposed lakebeds and shorelines implying greater aridity in the falklands than at present

extended late holocene relative sea level histories for north carolina usa abstract we produced 3000 year long relative sea level rsl histories for two sites in north carolina usa using foraminifera preserved in new and existing cores of dated salt marsh sediment at cedar island rsl rose by 2 4 m during the past 3000 years compared to 3 3 m at roanoke island this spatial difference arises primarily from differential gia that caused late holocene rsl rise to be 0 1 0 2 mm yr faster at roanoke island than at cedar island however a non linear difference in rsl between the two study regions particularly from 0 ce to 1250 ce indicates that additional local to regional scale processes drove centennial scale rsl change in north carolina therefore the cedar island and roanoke island records should be considered as independent of one another between site differences on sub millennial timescales cannot be adequately explained by non stationary tides sediment compaction or local sediment dynamics we propose that a period of accelerating rsl rise from 600 ce to 1100 ce that is present at roanoke island and other sites north of cape hatteras at least as far as connecticut but absent at cedar island and other sites south of cape hatteras at least as far as northeastern florida is a local to regional scale effect of dynamic ocean and or atmospheric circulation

holocene periodicity in north atlantic climate and deep ocean flow south of iceland climate fluctuations during the past millennium are relatively well documented1 on a longer timescale there is growing evidence of millennial scale variability of holocene climate at periodicities of 2 500 and 950 years possibly caused by changes in solar flux 2 3 and 1 500 years maybe related to an internal oscillation of the climate system 4 5 6 but the involvement of deep water masses in these holocene climate changes has yet to be established here we use sediment grain size data from the iceland basin to reconstruct past changes in the speed of deep water flow the study site is under the influence of iceland scotland overflow water isow the flow of which is an important component of the thermohaline circulation that modulates european climate flow changes coincide with some known climate events the little ice age and the mediaeval warm period and extend over the entire holocene epoch with aquasi periodicity of 1 500 years the grain size data indicate afaster isow flow when the climate of northern europe is warmer however a second mode of operation is observed in the early holocene when warm climate intervals are associated with slower isow flow at that time the melting remnant of land based glacial age ice may have provided a sufficient source of fresh water to the ocean to reduce isow flow south of iceland

inverted barometer contributions to recent sea level changes along the northeast coast of north america regional sea level sl changes reflect dynamic and isostatic ocean effects recent works have interpreted accelerated and extreme sl changes along the northeast coast of north america primarily in terms of dynamic changes however dedicated study of isostatic changes related to surface atmospheric pressure loading the inverted barometer ib effect has been lacking this investigation uses five different atmospheric pressure products to analyze the influence of the ib effect on annual mean sl from tide gauge records the ib effect explains 25 of interannual sl variance and accounts for 50 of the magnitude of a recent extreme event of sl rise along atlantic canada and new england estimated ib effects also amount to 10 30 of recent multidecadal sl accelerations over the mid atlantic bight and southern new england these findings reiterate the need for careful estimation and removal of isostatic effects for studies of dynamic sl

seismic reflections from the near vertical san andreas fault major near vertical strike slip faults should reflect seismic energy due to velocity contrasts within and across the fault zone analogous to sub horizontal faults commonly imaged by both multichannel and wide angle reflection surveys an increase of velocity with depth in the upper crust allows such reflections to be detected in surface seismic surveys we have observed fault reflection events from both sides of the san andreas fault in long offset common receiver gathers acquired near san francisco the events can be traced to the known surface position of the fault and provide constraints on the subsurface position to 3 7 km depth such reflections can be used to find the geometry of major near vertical faults even in areas without active seismicity providing information crucial to the understanding of the tectonics and seismic hazards of strike slip faulting

stable carbon isotopes as potential sea level indicators in salt marshes north carolina usa we compared the use of 13c values and c n ratios from salt marsh sediments to reconstruct relative sea level rsl with an established approach using foraminifera analysis of bulk organic sediment and plant samples collected along transects at two sites in north carolina usa demonstrates that sediment 13c values can be used to distinguish between spartina alterniflora dominated low marsh c photosynthetic pathway 13c values from 17 6 to 16 1 and juncus roemerianus dominated high marsh c 3 photosynthetic pathway 13c values from 28 2 to 21 8 environments juncus roemerianus plants undergo little decompositional change in 13c average 0 8 although there is a clear difference between spartina alterniflora tissue and bulk organic sediments approximately 4 c n ratios on bulk organic sediment from freshwater upland and salt marsh environments converge during early diagenesis rendering them of little use in reconstructing rsl the utility of 13c values as a sea level indicator is limited by the elevational range of c4 plants making it difficult to recognize salt marsh subenvironments and improve the precision of rsl reconstructions furthermore juncus roemerianus dominated high marsh and freshwater upland sediments cannot be adequately distinguished with 13c values

relative sea level change in connecticut usa during the last 2200 yrs we produced a relative sea level rsl reconstruction from connecticut usa spanning the last 2200 yrs that is free from the influence of sediment compaction the reconstruction used a suite of vertically and laterally ordered sediment samples 2 cm above bedrock that were collected by excavating a trench along an evenly sloped bedrock surface paleomarsh elevation was reconstructed using a regional scale transfer function trained on the modern distribution of foraminifera on long island sound salt marshes and supported by bulk sediment 13c measurements the history of sediment accumulation was estimated using an age elevation model constrained by radiocarbon dates and recognition of pollution horizons of known age the rsl reconstruction was combined with regional tide gauge measurements spanning the last 150 yrs before being quantitatively analyzed using an error in variables integrated gaussian process model to identify sea level trends with formal and appropriate treatment of uncertainty and the temporal distribution of data rsl rise was stable 1 mm yr from 200 bce to 1000 ce slowed to a minimum rate of rise 0 41 mm yr at 1400 ce and then accelerated continuously to reach a current rate of 3 2 mm yr which is the fastest century scale rate of the last 2200 yrs change point analysis identified that modern rates of rise in connecticut began at 1850 1886 ce this timing is synchronous with changes recorded at other sites on the u s atlantic coast and is likely the local expression of a global sea level change earlier sea level trends show coherence north of cape hatteras that are contrasted with southern sites this pattern may represent centennial scale variability in the position and or strength of the gulf stream comparison of the new record to three existing and reanalyzed rsl reconstructions from the same site developed using sediment cores indicates that compaction is unlikely to significantly distort rsl reconstructions produced from shallow 2 3 m thick sequences of salt marsh peat

application of stable carbon isotopes for reconstructing salt marsh floral zones and relative sea level new jersey usa we investigated use of 13c in bulk organic sediment to define the botanical origin of samples preserved in coastal sediment as a means to reconstruct relative sea level in new jersey usa modern transects at three sites demonstrated that low and high salt marsh floral zones dominated by c4 species spartina alterniflora and spartina patens were associated with sediment 13c values between 18 9 and 15 8 and occurred from mean tide level mtl to mean higher high water mhhw brackish transitional settings vegetated by phragmites australis with iva fructescens and typha sp c3 species and freshwater upland samples c3 species were characterized by bulk sediment 13c values of 27 0 to 22 0 and existed above mhhw parallel transects at one site suggested that intra site variability was not discernible the utility of 13c values for reconstructing relative sea level in new jersey is limited by an inability to differentiate between brackish sediments related to sea level and freshwater upland samples to facilitate this distinction in a 4 4 m core we used a multi proxy approach 13c values with presence or absence of agglutinated foraminifera to recognize indicative meanings for four sample types sediment with 13c values greater than 18 9 was derived from a vegetated salt marsh and formed between mtl and mhhw sediment with 13c values less than 22 0 and containing agglutinated foraminifera formed in a brackish transitional zone between mhhw and highest astronomical tide hat this is the narrowest elevational range of the four sample types and most precise sea level indicator sediment with 13c values less than 22 0 and lacking foraminifera can only constrain the upper bound of former sea level samples with intermediate values 22 0 to 18 9 formed between mtl and hat using these indicative meanings and radiocarbon dates we suggest that a transition from brackish to salt marsh 13c values recorded in the core took approximately 350 years from 1800 to 1450 cal a bp

late glacial and holocene glacier fluctuations and environmental change on south georgia southern ocean south georgia provides a terrestrial record of postglacial environmental change from a largely oceanic zone of the earth the record is representative of the southern westerlies and provides a link between antarctica and the temperate zones of southern south america evidence from glacial geomorphology slope stratigraphy and analyses of environmental indicators in peat and lake cores is used to interpret this record wastage of the full glacial ice cap was interrupted by a late glacial stade of the outlet and valley glaciers before ca 10 000 yr b p plant growth had begun at low altitude 50 m on the sheltered lee side northeast coast within the late glacial moraine limits by 9700 yr b p environmental conditions on slopes above 80 m probably were too rigorous for a stable vegetation cover until ca 6400 yr b p this was followed by a period from 5600 to 4800 yr b p when conditions were warmer than at present by up to 0 6 c periods of climatic cooling occurred at ca 4800 3800 yr b p ca 3400 1800 yr b p and within the last 1400 yr the most extensive holocene advance of south georgia glaciers culminated just before 2200 yr b p these holocene temperature changes of between 0 5 and 1 0 c are comparable in scale and timing to those identified from recent analyses of vostok ice cores from the antarctic ice sheet

rate and nature of podzolisation in aeolian sands in the falkland islands south atlantic abstract the rate and nature of podzolic soil development in aeolian sands in the cool temperate falkland islands south atlantic have been evaluated using 14c dating and morphological and chemical criteria in freely drained sands a carbic podzol developed over a minimum period of ca 2500 3000 years in sands with some drainage restriction a carbi ferric podzol developed within 300 500 years the shorter time span is consistent with results for podzolisation from other locations morphological and chemical contrasts between the profiles are inversely related to soil age the younger soil exhibits more complex podzolic horizonation and is attributed to pedogenesis in association with wetter profile conditions

quantitative interpretation of fossil pollen spectra dissimilarity coefficients and the method of modern analogs abstract dissimilarity coefficients measure the difference between multivariate samples and provide a quantitative aid to the identification of modern analogs for fossil pollen samples how eight coefficients responded to differences among modern pollen samples from eastern north america was tested these coefficients represent three different classes 1 unweighted coefficients that are most strongly influenced by large valued pollen types 2 equal weight coefficients that weight all pollen types equally but can be too sensitive to variations among rare types and 3 signal0to noise coefficients that are intermediate in their weighting of pollen types the studies with modern pollen allowed definition of critical values for each coefficient which when not exceeded indicate that two pollen samples originate from the same vegetation region dissimilarity coefficients were used to compare modern and fossil pollen samples and modern samples so similar to fossil samples were found that most of three late quaternary pollen diagrams could be reconstructed by substituting modern samples for fossil samples when the coefficients indicated that the fossil spectra had no modern analogs then the reconstructed diagrams did not match all aspects of the originals no modern analogs existed for samples from before 9300 yr b p at kirchner marsh minnesota and from before 11 000 yr b p at wintergreen lake michigan but modern analogs existed for almost all holocene samples from these two sites and brandreth bog new york

fault zone guided waves from explosions in the san andreas fault at parkfield and cienega valley california fault zone guided waves were successfully excited by near surface explosions in the san andreas fault zone both at parkfield and cienega valley central california the guided waves were observed on linear three component seismic arrays deployed across the fault trace these waves were not excited by explosions located outside the fault zone the amplitude spectra of guided waves show a maximum peak at 2 hz at parkfield and 3 hz at cienega valley the guided wave amplitude decays sharply with observation distance from the fault trace the explosion excited fault zone guided waves are similar to those generated by earthquakes at parkfield but have lower frequencies and travel more slowly these observations suggest that the fault zone wave guide has lower seismic velocities as it approaches the surface at parkfield we have modeled the waveforms as s waves trapped in a low velocity wave guide sandwiched between high velocity wall rocks resulting in love type fault zone guided waves while the results are nonunique the parkfield data are adequately fit by a shallow wave guide 170 m wide with an s velocity 0 85 km sec and an apparent q 30 to 40 at cienega valley the fault zone wave guide appears to be about 120 m wide with an s velocity 0 7 km sec and a q 30

a review of statistical chronology models for high resolution proxy based holocene palaeoenvironmental reconstruction abstract in this paper we explain the background workings and results obtained from three recently developed statistical age depth models implemented in freely available general purpose software packages bpeat oxcal and bchron these models aim to reconstruct the sedimentation rate in a single core typically lake peat or ocean given a limited number of scientific date estimates usually radiocarbon and fixed depths most importantly they provide a suitably qualified estimate of the uncertainty in the age depth chronology and thus can be used in a variety of applications we perform a large data driven study of the three models and discuss their general utility in chronology construction for palaeoenvironmental research

integrated seismic interpretation of the carlsberg fault zone copenhagen denmark summary we locate the concealed carlsberg fault zone along a 12 km long trace in the copenhagen city centre by seismic refraction reflection and fan profiling the carlsberg fault is located in a nnw sse striking fault system in the border zone between the danish basin and the baltic shield recent earthquakes indicate that this area is tectonically active a seismic refraction study across the carlsberg fault shows that the fault zone is a low velocity zone and marks a change in seismic velocity structure a normal incidence reflection seismic section shows a coincident flower like structure we have recorded seismic signals in a fan geometry from shots detonated both inside the low velocity fault zone and up to 500 m away from the fault zone the seismic energy was recorded on three receiver arrays 1 5 to 2 4 km long arcs across the expected location of the 400 to 700 m wide fault zone at distances of up to 7 km from the shots shots detonated inside the fault zone result in 1 weak and delayed first arrivals on the receivers located inside the fault zone compared to earlier and stronger first arrivals outside the fault zone 2 strong guided p and s waves as well as surface waves inside the fault zone the fault zone is a shadow zone to shots detonated outside the fault zone finite difference wavefield modelling supports the interpretations of the fan recordings our fan recording approach facilitates cost efficient mapping of fault zones in densely urbanized areas where seismic normal incidence and refraction profiling are not feasible

signature of the atlantic meridional overturning circulation in sea level along the east coast of north america in this letter we examine the relationship between the north atlantic meridional overturning circulation moc and sea level sl along the east coast of north america in the eddy permitting ocean model occam we find a distinctive topography following pattern of sl variability in the western north atlantic that is closely linked with the changing strength of the moc with a 2 cm drop in sl along the us east coast corresponding to a 1sv increase in the moc we find a similar pattern of sl variability in the altimetry record and show that this meridionally coherent sl mode dominates interannual sl variability at tide gauges along the north american east coast between 40 50n hence we conclude that north american coastal sea level may indeed be a useful indicator of moc variability on interannual timescales allowing an observationally based estimate of the likely range of interannual moc fluctuations to be determined citation bingham r j and c w hughes 2009 signature of the atlantic meridional overturning circulation in sea level along the east coast of north america geophys res lett 36 l02603 doi 10 1029 2008gl036215

oceanic control of sea level rise patterns along the east coast of the united states 1 along the eastern seaboard of the u s from florida to maine sea level rise slr shows notable patterns and significant deviation from the global mean which have been attributed to land subsidence consistent with several recent studies we analyze various observation and modeling data and find that ocean dynamics is also an important factor in explaining these coastal slr patterns despite a southward shift since the 1990s an overall northward shift of the gulf stream during the twentieth century contributed to the faster slr in the mid atlantic region north carolina to new jersey in response to the 21st century climatic forcing the rise fall of the dynamic sea level north south of cape hatteras is mainly induced by the significant decline of ocean density contrast across the gulf stream this baroclinic process is the likely cause of the recent switch of the coastal slr to a pattern with faster slower rates north south of cape hatteras citation yin j and p b goddard 2013 oceanic control of sea level rise patterns along the east coast of the united states geophys res lett 40 doi 10 1002 2013gl057992

on the driving processes of the atlantic meridional overturning circulation because of its relevance for the global climate the atlantic meridional overturning circulation amoc has been a major research focus for many years yet the question of which physical mechanisms ultimately drive the amoc in the sense of providing its energy supply remains a matter of controversy here we review both observational data and model results concerning the two main candidates vertical mixing processes in the ocean s interior and wind induced ekman upwelling in the southern ocean in distinction to the energy source we also discuss the role of surface heat and freshwater fluxes which influence the volume transport of the meridional overturning circulation and shape its spatial circulation pattern without actually supplying energy to the overturning itself in steady state we conclude that both wind driven upwelling and vertical mixing are likely contributing to driving the observed circulation to quantify their respective contributions future research needs to address some open questions which we outline

gyre scale atmospheric pressure variations and their relation to 19th and 20th century sea level rise 1 most of the long tide gauge records in the north atlantic and north pacific commonly used to estimate global sea level rise and acceleration display a marked difference in behavior in the late 1800 s early 1900 s compared to the latter half of the 20th century the rates of sea level rise tend to be lower in the 19th compared to 20th century we show this behavior may be related to long term gyre scale surface pressure variations similar to those associated with the northern annular mode as sea level pressure increases decreases at decadal and longer timescales at the centers of the subtropical atmospheric gyres sea level trends along the eastern margins in each ocean basin decrease increase this is not an isostatic response the scaling between local surface pressure and sea level at interannual and longer timescales is 3 to 6 times greater than expected by that mechanism rather it appears to be the result of large possibly gyre scale changes in ocean circulation some evidence is also presented indicating slow 2 cm sec westward propagation of sea level changes in the atlantic from the west coast of europe to the east coast of the u s which produce the decadal variability seen there

quaternary glaciations in the southern ocean and antarctic peninsula area abstract there are three main difficulties in constructing detailed time series for late quaternary glacier fluctuations in the southern ocean sub antarctic region sea level control on ice extent differential tectonics and lack of material for radiometric dating south of 60 s the glacial equilibrium line altitude is low enough for glaciers to expand without a decrease in temperature if sea level falls thus most tidewater glaciers in this region are not reliable indicators of small scale fluctuations in climate tectonic uplift during the quaternary may explain why the falkland islands did not develop most of their glacial and nivoglacial features until the last glaciation the south shetland islands have a unique assemblage of raised marine features in the sub antarctic possibly because the crustal block overlies a zone of magmatism and may respond sensitively to isostatic changes imposed by fluctuating ice masses despite the lack of vegetation some radiometric dates have been obtained from peat seaweed and fossil remains of marine shells and bones associated with glacial and raised beach deposits together with relative weathering criteria and drift distribution these suggestthat glaciers in the southern ocean and sub antarctic region have fluctuated synchronously with glaciers elsewhere in the southern hemisphere during the last 100 ka the last glaciation maximum culminated after 26 ka bp and glacier advances are inferred for the late glacial intervals 15 14 ka and 12 10 ka bp and the neoglacial interval last 5 ka

high resolution shear wave seismics across the carlsberg fault zone south of copenhagen implications for linking mesozoic and late pleistocene structures abstract the carlsberg fault zone cfz is a nnw sse striking structure close to the transition zone between the danish basin and the baltic shield we examine the fault evolution by combining very high resolution onshore shear wave seismic data one conventional onshore seismic profile and marine reflection seismic profiles the faulting geometry indicates a strong influence of triassic subsidence and rifting in the central european basin system growth strata within the cfz surrounding hollviken graben reveal syntectonic sedimentation in the lower triassic indicating the opening to be a result of triassic rifting in the upper cretaceous growth faulting documents continued rifting these findings contrast the late cretaceous to paleogene inversion tectonics in neighboring structures such as the tornquist zone the high resolution shear wave seismic method was used to image faulting in quaternary and danian layers in the cfz the portable compact vibrator source elvis iii s8 was used to acquire a 1150 m long seismic section on the island amager south of copenhagen the shallow subsurface in the investigation area is dominated by quaternary glacial till deposits in the upper 5 11 m and danian limestone below in the shear wave profile we imaged the uppermost 30 m of the western part of cfz the complex fault zone comprises normal block faults and one reverse block fault the observed faults cut through the danian as well as the quaternary overburden hence there are strong indicators for ongoing faulting like mapped faulting in quaternary sediments and ongoing subsidence of the eastern block of the cfz as interpreted by other authors the lack of earthquakes localized in the fault zone implies that either the frequency of occurring earthquakes is too small to be recorded in the observation time span or that the movement of the shallow sub surface layers may be due to other sources than purely tectonic processes

the seal edge coombes north derbyshire a study of their erosional and depositional history periglacial landforms and deposits of devensian age are commonly observed on the higher hill slopes of north derbyshire but to date very few glacial features or sediments have been recognised at seal edge the escarpment slope has been sculptured by both frost and nivational processes but at middle seal clough there are lobate ridges located beyond the talus foot that are probably moraines formed during the dimlington stadial of the late devensian by a small corrie glacier the history of the coombe has been interpreted from a study of both the inorganic and organic sediments and although the results are not conclusive they indicate that ice and snow were important in the development of the coombe and that the peat formations in the basin also provide the earliest record to date for events in the vegetation history of the southern pennine moorlands