constraining continental margin seismicity by extending on shore seismograph stations to critical off shore sites the westernmost north american plate margin in central california includes major faults with both onshore and offshore segments prior to deployment during 1997 and 1998 of a suite of ocean bottom seismometers within monterey bay the distribution and focal mechanisms of offshore earthquakes were poorly constrained the use of ocean bottom seismic stations improves the accuracy of locations for events in monterey bay especially for those far offshore and permits more robust focal mechanism solutions by reducing uncertainties in strike dip and rake these initial results using u s geological survey crustal velocity models and location parameters reduce the apparent scatter of seismic events and focal mechanisms and the more consistent solutions provide valuable information on fault characteristics for the san gregorio fault sgf and monterey bay fault zone mbfz most seismic events are relocated to the northern section of the sgf defining a zone of compressional deformation and relatively high microseismicity the mbfz is the source for fewer but important and well located events surprisingly no events were observed on the southern sgf offshore of carmel and pebble beach despite the well defined trace of the san gregorio along carmel canyon

a 5500 year oxygen isotope record of high arctic environmental change from southern spitsbergen the oxygen isotope composition of chironomid head capsules in a sediment core spanning the past 5500 years from lake svartvatnet in southern spitsbergen was used to reconstruct the oxygen isotope composition of lake water 18olw and local precipitation the 18olw values display shifts from the baseline variability consistent with the timing of recognized historical climatic episodes such as the roman warm period the dark ages cold period and the little ice age the highest values of the record ca 3 above modern 18olw values occur at ca 1900 1800 cal yr bp three negative excursions increasing in intensity toward the present at 3400 3200 1250 1100 and 350 50 cal yr bp are tentatively linked to roughly synchronous episodes of increased glacier activity and general cold spells around the northern north atlantic their manifestation in the svartvatnet 18olw record not only testify to the sensitivity and potential of high arctic lacustrine 18ochir records in tracking terrestrial climate ev

preservation of glaciochemical time series in snow and ice from the penny ice cap baffin island a detailed investigation of major ion concentrations of snow and ice in the summit region of penny ice cap pic was performed to determine the effects of summer melt on the glaciochemical time series while ion migration due to meltwater percolation makes it difficult to confidently count annual layers in the glaciochemical profiles time series of these parameters do show good structure and a strong one year spectral component suggesting that annual to biannual signals are preserved in pic glaciochemical records

115 year ice core data from akademii nauk ice cap severnaya zemlya high resolution record of eurasian arctic climate change from 1999 to 2001 a 724 m deep ice core was drilled on akademii nauk ice cap severnaya zemlya to gain high resolution proxy data from the central russian arctic despite strong summertime meltwater percolation this ice core provides valuable information on the regional climate and environmental history we present data of stable water isotopes melt layer content and major ions from the uppermost 57 m of this core covering the period 1883 1998 dating was achieved by counting seasonal isotopic cycles and using reference horizons multi annual 18 o values reflect eurasian sub arctic and arctic surface air temperature variations we found strong correlations to instrumental temperature data from some stations e g r 0 62 for vardo northern norway the 18 o values show pronounced 20th century temperature changes with a strong rise about 1920 and the absolute temperature maximum in the 1930s a recent decrease in the deuterium excess time series indicates an increasing role of the kara sea as a regional moisture source from the multi annual ion variations we deduced decreasing sea salt aerosol trends in the 20th century as reflected by sodium and chloride whereas sulphate and nitrate are strongly affected by anthropogenic pollution

nitrogen fixation on arctic glaciers svalbard telling j anesio a m tranter m irvine fynn t hodson a butler c wadham j 2011 nitrogen fixation on arctic glaciers svalbard journal of geophysical research biogeosciences 116 article number g03039

holocene glacial and climatic variations on spitsbergen svalbard holocene glacial and climatic variations have been inferred from investigations of sediment cores from the proglacial lake linnevatnet western spitsbergen a low content of glacially derived coal absence of regular laminations and a slow sedimentation rate in the lower part of the lacustrine sediments indicate that the former glaciers that existed within the catchment area during the last ice age melted quickly away as a result of the younger dryas holocene warming and during the next 6000 years there were no glaciers in the valley increasing coal content incipient laminations and rising sedimentation rates indicate that the glacier linnebreen started to form 4000 5000 years ago probably as a response to the late holocene cooling the holocene maximum extent of the glacier occurred during the little ice age starting with a pronounced ice advance in the thirteenth or fourteenth century a well dated core from billefjorden which is assumed to reflect glacial fluctuations in the inner part of the i

glaciochemistry of polar ice cores a review human activities have already modified the chemical composition of the natural atmosphere even in very remote regions of the world the study of chemical parameters stored in solid precipitation and accumulated on polar ice sheets over the last several hundred thousand years provides a unique tool for obtaining information on the composition of the preindustrial atmosphere and its natural variability over the past this paper deals with the chemistry of polar ice focused on the soluble mineral na nh4 k ca mg h f cl no3 so4 and h2o2 and organic methanesulfonate ch3so3 formate hcoo acetate ch3coo and formaldehyde hcho species and their interpretation in terms of past atmospheric composition aerosols and water soluble gaseous species we discuss ice core dating the difficulties connected with trace measurements and the significance of the ionic composition of snow we examine temporal from the last decades back to the last climatic cycle and spatial including examples from coastal as well as central areas of greenland and antarctica variations in the ionic budget of the precipitation and evaluate ice core studies in terms of the chemical composition of our past atmosphere we review 1 how greenland and antarctic ice cores that span the last few centuries have provided information on the impact of human activities and 2 how the chemistry of deep ice cores provides information on various past natural phenomena such as climatic variations glacial interglacial changes el nino volcanic eruptions and large boreal forest fires

reconstruction of three centuries of annual accumulation rates based on the record of stable isotopes of water from lomonosovfonna svalbard we use the upper 81 in of the record of stable isotopes of water from a 122 in long ice core from lomonosovfonna central spitsbergen svalbard to construct an ice core chronology and the annual accumulation rates over the icefield the isotope cycles are counted in the ice core record using a model that neglects short wavelength and low amplitude cycles we find approximately the same number of delta 18 o cycles as years between known reference horizons and assume these cycles represent annual cycles testing the validity of this assumption using cycles in deltad shows that both records give similar numbers of cycles using the delta 18 o chronology and decompressing the accumulation records using the nye flow model we calculate the annual accumulation for the ice core site back to ad 1715 we find that the average accumulation rate from 1715 to 1950 was on average 0 30 in w e accumulation rates increased about 25 during the later part of the 20th century to an average of 0 41 in w e for the period 1950 97 the accumulation rates show highly significant 2 1 and 21 year periodicities which gives credibility to our time scale

lomonosovfonna and holtedahlfonna ice cores reveal east west disparities of the spitsbergen environment since ad 1700 an ice core extracted from holtedahlfonna ice cap western spitsbergen record spanning the period 1700 2005 was analyzed for major ions the leading empirical orthogonal function eof component is correlated with an index of summer melt log na mg 2 from 1850 and shows that almost 50 of the variance can be attributed to seasonal melting since the beginning of the industrial revolution the holtedahlfonna d 18 o value is less negative than in the more easterly lomonosovfonna ice core suggesting that moist air masses originate from a closer source most likely the greenland sea during the little ice age the lower methanesulfonic acid msa concentration and msa non sea salt sulfate fraction are consistent with the greenland sea as the main source for biogenic ions in the ice cores both the melt index and the msa fraction suggest that the early decades of the 18th century may have exhibited the coldest summers of the last 300 years in svalbard ammonium concentrations rise from 1880 which may result from the warming of the greenland sea or from zonal differences in atmospheric pollution transport over svalbard during winter neutralized aerosols are trapped within the tropospheric inversion layer which is usually weaker over open seas than over sea ice placing holtedahlfonna within the inversion more frequently than lomonosovfonna

global and regional ridge patterns on mars abstract over 16 000 wrinkle ridges on mars have been classified mapped and digitized to provide a large computer accessible data base for analyzing regions subjected to possible compressive stresses the survey has revealed major compressive structures that occur well beyond the tharsis dominated hemisphere the large variety of affected geologic terrains indicate stresses not simply localized in the intercrater plains one major area of inferred compression occurs in the southern cratered highlands near longitude 180 w where major ridges and scarps extend over 3000 km the occurrence and orientation of many ridges are locally controlled by ancient impact basins the chryse basin in particular has an important effect on ridges in northern lunae planum the removal of all basin concentric ridges reveals however a complex global pattern although such patterns may yet be controlled by heavily degraded impact basins major regional trends also emerge that appear to require broader scale global stresses most ridges in the western hemisphere are shown to be orthogonal to three centers corresponding to tharsis 1 n 122 w syria 12 s 104 w and chryse 19 n 47 w ridges not included in these three sets are generally more random and highly localized most but by no means all ridges in the eastern hemisphere are controlled by the hellas and isidis basins a simple global grid is not yet identifiable and may not be recognizable owing to the large number of regional patterns

coastal geomorphology of the martian northern plains the paper considers the question of the formation of the outflow channels and valley networks discovered on the martian northern plains during the mariner 9 mission parker and saunders 1987 and parker et al 1987 1989 data are used to describe key features common both in the lower reaches of the outflow channels and within and along the margins of the entire northern plains it is suggested that of the geological processes capable of producing similar morphologies on earth lacustrine or marine deposition and subsequent periglacial modification offer the simplest and most consistent explanation for the suit of features found on mars

the large thaumasia graben on mars is it a rift 1 we investigate the morphology and topography of one of the largest fault bounded tectonic structures on mars a complex approximately n s trending system of troughs and scarps at the western border of the thaumasia plateau in the claritas region hereinafter referred to as thaumasia graben or tg it is located between 15 s and 38 s latitude and at 255 e longitude no detailed investigation of its morphotectonic setting has been performed yet the region is a complexly fractured area with a number of different fault sets including simple and complex graben the tg extends over more than 1000 km along its trend averaging 100 km in width and 1 6 km in depth crustal extension is accommodated by the formation of a system of asymmetric graben or halfgraben on the basis of fault orientation and trough depth the tg can be subdivided in a north south direction into three segments except for the northernmost segment the predominant master fault system is located along the eastern flank of the tg highlighting the overall asymmetric architecture fault length segments vary from 50 to 90 km with observable displacements of 1 3 2 2 km crustal extension inferred from gridded mola topography across scarp offsets varies along trend between 0 5 km and 4 km assuming a fault dip of 60 this is relatively moderate extension if compared to terrestrial continental rifts but consistent with extension measured across the tempe rift on mars we find that the thaumasia graben displays some characteristics which are common to terrestrial continental rifts whereas other properties are distinctively not rift like

martian rampart crater ejecta experiments and analysis of melt water interaction abstract viking images of martian craters with rampart bordered ejecta deposits reveal distinct impact ejecta morphology when compared to that associated with similar sized craters on the moon and mercury topographic control of distribution lobate and terraced margins cross cutting relationships and multiple stratigraphic units are evidence for ejecta emplacement by surface flowage it is suggested that target water explosively vaporized during impact alters initial ballistic trajectories of ejecta and produces surging flow emplacement the dispersal of particulates during a series of controlled steam explosions generated by interaction of a thermite melt with water has been experimentally modeled preliminary results indicate that the mass ratio of water to melt and confining pressure control the degree of melt fragmentation ejecta particle size and the energy and mode of melt ejecta dispersal study of terrestrial lobate volcanic ejecta produced by steam blast explosions reveals that particle size and vapor to clast volume ratio are primary parameters characterizing the emplacement mechanism and deposit morphology martian crater ramparts are formed when ejecta surges lose fluidizing vapors and transported particles are deposited en masse this deposition results from flow yield strength increasing above shear stress due to interparticle friction

spatial and temporal variability of snow accumulation using ground penetrating radar and ice cores on a svalbard glacier a 50 mhz ground penetrating radar was used to detect horizontal layers in the snowpack along a longitudinal profile on nordenskjoldbreen a svalbard glacier the profile passed two shallow and one deep ice core sites two internal radar reflection layers were dated using parameters measured in the deep core radar travel times were converted to water equivalent yielding snow accumulation rates along the profile for three time periods 1986 99 1963 99 and 1963 86 the results show 40 60 spatial variability in snow accumulation over short distances along the profile the average annual accumulation rate for 1986 99 was found to be about 12 higher than for the period 1963 86 which indicates increased accumulation in the late 1980s and 1990s

warm summers and ion concentrations in snow comparison of present day with medieval warm epoch from snow pits and an ice core from lomonosovfonna svalbard snow pits sampled during two consecutive years 2001 2002 at the summit of lomonosov fonna ice cap in central spitsbergen svalbard showed that ion concentrations were spatially homogeneous the snowpack on lomonosovfonna shows no evidence of aerosol deposition from arctic haze in contrast to holtedahlfonna a glacier at a similar altitude in northern spitsbergen where there is a clear signature in common with many other ice caps in the arctic lomonosovfonna experiences periodic melting and the deepest of the snow pits contained a record of one exceptionally warm 2001 and one long summer 2000 the most easily eluted species are nitrate and the divalent ions very low ion concentrations and high values of a melt indicator log na mg 2 were a result of either deep percolation or runoff of ions during melting comparing the snow pit record with the ion record of more than 800 years from an ice core drilled on lomonosovfonna in 1997 reveals some layers with similar composition to those that suffered significant melting in the snowpack a few years in the 20th century and around ad 1750 and all of the core from before ad 1200 show unusually heavy melting

a note on the effect of bottom currents on an ocean bottom seismometer abstract two three component ocean bottom seismometers and a current meter were deployed a few hundred meters apart on the southern blake plateau off the united states eastern coast to study the effect of near bottom currents on the background noise level of seismometers although analysis of the data is limited somewhat by instrumental problems the increase in current speed which ranged from 2 to 25 cm sec is correlated with a broadband increase in the noise level at frequencies below 10 hz intermittent periods of narrow band 8 hz noise which were also observed are not correlative with bottom currents and were tentatively attributed to passing ships details of the mechanism of generation of the background noise cannot be determined from the present data set

some comments on climatic reconstructions from ice cores drilled in areas of high melt poor consideration has been given in many arctic circum polar ice core studies to the effect of summer snow melt on chemistry stable isotope concentrations and time scales many of these corps are drilled close to the firn line where melt is intense some come from below the firn line where accumulation is solely in the form of super imposed ice in all cases seasonal signals are reduced or removed and in some time gaps develop during periods of excessive melting which situate the drill site in the ablation zone consequently cross correlations of assumed synchronous events among the cores are invalid so that time scales along the same cores differ between authors by factors of over 2 many so called climatic signals are imaginary rather than real by reference to published analyses of cores from the superimposed ice zone on devon ice cap koerner 1970 and meighen ice cap koerner and paterson 1974 it is shown how melt affects all the normally well established ice core proxies and leads to their misinterpretation despite these limitations the cores can give valuable low resolution records for all or part of the holocene they show that the thermal maximum in the circum polar arctic occurred in the early holocene this maximum effected negative balances on all the ice caps and removed the smaller ones cooler conditions in the second half of the holocene have caused the regrowth of these same ice caps

analysis of the seismic origin of landslides examples from the new madrid seismic zone by analyzing two landslides in the new madrid seismic zone we develop an approach for judging if a landslide or group of landslides of unknown origin was more likely to have formed as a result of earthquake shaking or in aseismic conditions the two landslides analyzed are representative of two groups of land slides that previous research on the geomorphology and regional distribution of landslides in this region indicates may have been triggered by the 1811 1812 new madrid earthquakes slope stability models of aseismic conditions show that neither landslide is likely to have formed aseismically even in unrealistically high ground water conditions dynamic stability analysis using newmark s method shows that both slides probably would have experienced large inertial displacements during earthquake shaking similar to that which occurred in 1811 1812 these displacements are large enough that catastrophic failure is highly probable thus the stability analyses are consistent with other lines of evidence that these landslides formed as a result of strong earthquake shaking during the 1811 1812 earthquakes our analysis yields a general relationship between newmark landslide displacement earthquake shaking intensity and the critical acceleration of a landslide using this relationship we estimate the minimum shaking intensities required to trigger the types of landslides studied an mb 5 8 or m 5 9 earthquake is the lower bound threshold at zero epicentral distance that could trigger catastrophic movement of typical block slides in the new madrid seismic zone for earth flows mb 5 4 or m 5 3 is the threshold earthquake

a new ice core record from lomonosovfonna svalbard viewing the 1920 97 data in relation to present climate and environmental conditions in 1997 a 121 m ice core was retrieved from lomonosovfonna the highest ice field in spitsbergen svalbard 1250 m a s l radar measurements indicate an ice depth of 126 5 m and borehole temperature measurements show that the ice is below the melting point high resolution sampling of major ions oxygen isotopes and deuterium has been performed on the core and the results from the uppermost 36 rn suggest that quasi annual signals are preserved the 1963 radioactive layer is situated at 18 5 18 95 m giving a mean annual accumulation of 0 36 m we for the period 1963 96 the upper 36 rn of the ice core was dated back to 1920 by counting layers provided by the seasonal variations of the ions in addition to using a constant accumulation rate with thinning by pure shear according to nye 1963 the stratigraphy does not seem to have been obliterated by meltwater percolation in contrast to most previous core sites on svalbard the anthropogenic influence on the svalbard environment is illustrated by increased levels of sulphate nitrate and acidity both nitrate and sulphate levels started to increase in the late 1940s remained high until the late 1980s and have decreased during the last 15 years the records of delta o 18 msa methanesulphonic acid and melt features along the core agree with the temperature record from longycarbyen and the sea ice record from the barents sea at a multi year resolution suggesting that this ice core reflects local climatic conditions

structural development of coprates chasma and western ophir planum valles marineris rift mars a portion of valles marineris was mapped in detail in order to clarify the dominant processes responsible for the formation of coprates chasma new crater counts indicate that the caprock on western ophir planum plateau has a late hesperian crater age whereas trough floor preserved in western coprates chasma has an early to late hesperian crater age caprock on western ophir planum correlates in relative age with the syria planum formation and the caprock may overlie lower hesperian ridged plains material the conspicuous absence of wrinkle ridges on ophir planum may reflect burial by this later material trough floor material in coprates chasma correlates in relative age with ridged plains material on the adjacent lunae planum and coprates plateaus and represents a structurally coherent block displaced downward by normal faulting the crater counts and detailed structural relationships demonstrate the commonly accepted view that coprates chasma occupies a graben the floor of this graben is only thinly mantled by intratrough deposits and is relatively intact the trough shows no evidence for a chaotically broken and jumbled floor as required by genesis models of collapse and subsurface drainage formation of coprates chasma by keystone collapse of locally elevated topography is not supported by available topographic data but a general association between the trough and volcanotectonic activity in the tharsis region is considered to be a likely explanation for the trough forming stresses subtle asymmetries in topography and boundary fault development across coprates chasma may imply a gentle down to the north half graben geometry for the trough normal faults that define the northern margin of western coprates chasma and those that deform the adjacent ophir planum plateau change trend systematically with position implying a 30 rotation of the local horizontal principal stresses in this region during trough growth faulting on ophir planum appears related to the faulting that created the coprates chasma trough the geology and structure of coprates chasma are comparable to those of other troughs such as melas ius and perhaps candor chasmata suggesting that these troughs may also have formed as grabens the revised crater age for western ophir planum indicates that the initiation of trough faulting and subsidence in the valles marineris system is early late hesperian and may have been synchronous across the system relative to the prevailing cratering rate

a crustal velocity model for locating earthquakes in monterey bay california the seismicity of the monterey bay displays a sparse distribution of events with a majority in northern monterey bay on the san gregorio fault the paucity of near shore and offshore seismic recording instruments and the use of velocity models from inland regions for earthquake hypocentral locations and focal mechanisms have led to uncertainties and inaccuracies for seismic events on major faults that crosscut the bay new three component seismic data were acquired during 1997 1999 by the monterey bay aquarium research institute mbari margin seismology project using ocean bottom digital corehole and standard seismometers and coastal digital reftek instruments obtained from iris passcal by the university of california santa cruz we have analyzed phases from earthquakes in the monterey bay vicinity located by these instruments and used them to supplement the adjacent coastal stations of the permanent northern california seismic network a new one dimensional velocity model for the region requires slow velocities from 2 to 6 km that we attribute to sheared granites observed in the salinian block in the center of monterey bay velocities in the 10 16 km layer are consistent with continental crustal velocities a sharp increase in velocity at 16 km suggests a boundary that results from underplating of oceanic crust this underplated zone appears to extend to a depth of 27 30 km where we observe normal upper mantle velocities near 8 0 km sec new details from the ocean bottom corehole and coastal reftek instruments for events along the sgf and monterey bay fault zones hint at local fine scale structures and have implications for tectonic history and plate reconstruction interpretation

sulphate record from a northeast greenland ice core over the last 1200 years based on continuous flow analysis a 150 m deep ice core from the low accumulation area of northeast greenland was analyzed for sulphate calcium sodium and electrolytical meltwater conductivity at a depth resolution of approximately 1 cm by continuous flow analysis cfa the calcium and sodium profiles are used to establish a relatively precise ice core chronology by annual layer counting back to ad 830 inspection of the novel cfa method for sulphate revealed relative errors typically around 15 but at least 20 ng g 1 for concentrations 5130 ng g 1 and a current detection limit for routine ice core analyses of 40 ng g 1 annual sulphate peaks are shown to occur over almost the entire core with only a small shift in seasonality between the modern and pre industrial sections inspection of volcanic horizons allowed more accurate timing of these peaks and clear identification of calcium rich events disregarding clear volcanic peaks significant long term changes of sulphate are only seen over the industrial period however a higher frequency of important volcanic inputs was identified around ad 1200

ocean rafted pumice constrains postglacial relative sea level and supports holocene ice cap survival abstract distally deposited tephra from explosive volcanic eruptions can be a powerful tool for precise dating and correlation of sedimentary archives and landforms however the morphostratigraphic and chronological potential of ocean rafted pumice has been under utilized considering its long observational history and widespread distribution on modern and palaeo shorelines around the world here we analyze the geochemical composition and elevation data of 60 samples of ocean rafted pumice collected since 1958 from raised beaches on svalbard comparison of pumice data with postglacial relative sea level history suggests eight distinct pumice rafting events throughout the north atlantic during the middle and late holocene analyzed ocean rafted pumice exhibit consistent silicic composition characteristic of deposits from iceland s volcanic system katla eruption triggered jokulhlaups are key drivers of the transport of pumice from the katla caldera to beyond the coast of iceland and into the surface currents of the north atlantic ocean thus the correlation of distinct high concentration pumice horizons from katla deposited along raised middle holocene beach ridges in svalbard further advocates for the persistence of the m rdalsjokull ice cap through the holocene thermal maximum

reconciling channel formation processes with the nature of elevated outflow systems at ophir and aurorae plana mars 1 many hesperian outflow channels head at elevations compatible with aquifer recharge beneath the martian south polar cap and such channels are widely interpreted as the products of this recharge some outflow channels head at greater elevations that are inconsistent with southern recharge including three systems located in aurorae planum and eastern ophir planum these three systems have previously been interpreted as having formed through aqueous outbursts from local aquifers recharged by the meltwaters of ancient upland glaciers to the west however the viability of this interpretation is weakened by the lack of a geomorphic record supportive of past meltwater flow from western uplands inconsistencies between hypothesized processes and the nature of regional topography and mineralogy and the absence of satisfactory analog processes for catastrophic aqueous flow from the subsurface in contrast a volcanic origin for the ophir and aurorae systems appears to be in accord with the basic characteristics of constituent channels and associated landforms the volcanotectonic nature of the valles marineris system and adjacent upland plains and the nature of available analog landforms and processes though numerous uncertainties remain a volcanic interpretation of these outflow systems can more simply account for the existence of component channels the attributes of other elevated outflow systems on mars similarly appear to be most consistent with volcanic origins if the ophir and aurorae systems formed volcanically thermal considerations imply minimum erupted lava volumes of 6 4 103 km3 for allegheny vallis and 6 2 104 km3 for elaver vallis

a non extensive statistics of the fault population at the valles marineris extensional province mars a non extensive statistical physics approach is formulated and tested for the fault length distribution in the valles marineris extensional province mars the approach is composed of the following parts 1 the tsallis entropy 5 defined as s q k b 1 sigma w i 1 p i q q 1 2 maximization of the tsallis entropy under appropriate constraints 3 derivation of the cumulative distribution function cdf of the fault length population in testing the model a non extensive q parameter equal to 1 10 for independent non interacting faults and q 1 75 for linked faults are estimated the latter supports the conclusion that the fault system in the valles marineris extensional province mars is a sub extensive one and verifies with statistical physics terms the geological criteria introduced by schultz 2000 to classify the faults in independent and linked respectively c 2011 elsevier b v all rights reserved

reconstruction of the historical temperature trend from measurements in a medium length borehole on the lomonosovfonna plateau svalbard a medium length ice core was drilled at the ice divide on the lomonosovfonna plateau 1230 m a s l svalbard in may1997 as part of this project temperature measurements were performed in the 120 m deep borehole at this site the ice thickness based on radar measurements is 126 5 m and the mean annual accumulation rate is 380 kg m 3 the measurements over the 15 120 m depth interval show a nearly isothermal profile with a mean value of 2 8 c and a standard deviation of 0 2 c the measurements reveal a temperature minimum at approximately 70 m depth and a temperature gradient of 0 011 0 004 c m 1 near the bottom the temperature minimum and relatively low temperature gradient cannot be explained in terms of a steady state climate numerical calculations with a simple onedimensional diffusion advection model show that the temperature increased at a maximum rate of 0 02 0 025 k a 1 over the last 100 years the total temperature increase amounting to 2 0 3 0 k forcing the model with the observed record at svalbard airport revealed that in the 19th century the surface temperature was at most 2 5 k lower and that the instrumental observations started during a period with temperatures comparable to the end of the 19th century the data are of particular interest for historical simulations since often no other temperature data are available in polar areas

a seismic swarm and regional hydrothermal and hydrologic perturbations the northern endeavour segment february 2005 the february 2005 swarm at the overlapping spreading center osc on the northern end of the endeavour segment is the first swarm on the juan de fuca ridge recorded on a local seafloor seismic network the swarm included several larger earthquakes and caused triggered seismicity and a hydrothermal response in the endeavour vent fields as well as regional scale hydrologic pressure perturbations the spatial and temporal pattern of over 6000 earthquakes recorded during this seismic sequence is complex small magnitude events dominate and seismicity rates wax and wane indicating a magmatic process the main swarm initiates at the northern end of the endeavour ridge however most of the moment release including six strike slip events occurs in the southwest endeavour valley where the swarm epicenters generally migrate south the main swarm is contemporaneous with a hydrologic pressure response at four sealed seafloor boreholes 25 105 km away we infer that the seismic sequence is driven by a largely aseismic magma intrusion at the northern endeavour axis resulting stress changes trigger slip on tectonic faults and possibly dike propagation at the opposing limb of the endeavour osc in the southwest endeavour valley consistent with the eventual decapitation of the endeavour by the west valley segment furthermore 2 5 days after the start of the main swarm seismicity is triggered beneath the endeavour vent fields and temperature increases at a diffuse vent in the mothra field we infer that this delayed response is due to a hydrologic pressure pulse that diffuses away from the main magma intrusion

mantle dynamics in mars and venus influence of an immobile lithosphere on three dimensional mantle convection numerical calculations of fully three dimensional convection in constant viscosity compressible spherical shells are interpreted in terms of possible convective motions in the mantles of venus and mars the shells are heated both internally and from below to account for radiogenic heating secular cooling and heat flow from the core the lower boundary of each of the shells is isothermal and shear stress free as appropriate to the interface between a mantle and a liquid outer core the upper boundary of each of the shells is rigid and isothermal as appropriate to the base of a thick immobile lithosphere calculations with shear stress free upper boundaries are also carried out to assess the role of the rigid surface condition the ratio of the inner radius of each shell to its outer radius is in accordance with possible core sizes in both venus and mars a calculation is also carried out for a mars model with a small core to simulate mantle convection during early core formation different relative proportions of internal and bottom heating are investigated ranging from nearly complete heating from within to almost all heating from below the rayleigh numbers of all the cases are approximately 100 times the critical rayleigh numbers for the onset of convection cylindrical plumes are the prominent form of upwelling in the models independent of the surface boundary condition so long as sufficient heat derives from the core thus major volcanic centers on mars such as tharsis and elysium and the coronae and some equatorial highlands on venus may be the surface expressions of cylindrical mantle plumes the form of the downwelling sheets is significantly affected by the rigid boundary in that the sheets are more irregular in their horizontal structure than when the top boundary is shear stress free in the mainly heated from within models the downwelling sheets are also shorter and less temporally durable when the top boundary is rigid than when it is stress free thus the free motion of plates on the earth facilitates extensive durable convective currents that drive the plates while the stiffening of the lithospheres on mars and venus promotes a style of convection that is not particularly effective in breaking the lithosphere into plates in the rigid top cases the upper boundary layer surrounding the plumes appears to be interspersed with downwelling currents emanating radially from the plumes axes these currents may establish a stress field at the base of hotspot swells that could lead to radial fractures such as those on tharsis models with rigid upper boundaries have higher interior temperatures than do similar models with shear stress free upper boundaries on this basis venus not only has a higher surface temperature than earth but it would have a hotter mantle as well upwelling plumes are more numerous when the outer boundary is rigid as compared with shear stress free flows dominated by a few stong plumes occur when the proportion of basal heating is large thus if the martian crustal dichotomy were caused by a convective system dominated by spherical harmonic degree l 1 then the convection may have been driven strongly from below by a heating pulse accompanying core formation or from the flow of heat from an early hot core if a convective mechanism is responsible for the crustal dichotomy then the dichotomy is likely a very ancient feature however the small core models we consider consistently produce a convective pattern with a dominant l 2 signature which does not correlate with the martian crustal dichotomy a yet smaller core may be necessary to yield the l 1 pattern the small core convective pattern does correlate with the geoid and topography signatures of tharsis which have strong l 2 components and the model produces dynamic uplift comparable to the total topography of the tharsis rise models with larger cores i e with the probable inner to outer radius ratio of mars present mantle generate 4 km of uncompensated topography similar to estimates of the uncompensated tharsis topography thus the tharsis rise could have achieved its full height early in the evolution of mars by mantle plume dynamic uplift at present the uncompensated portion of the tharsis rise topography can be accounted for by dynamic uplift obviating the need for elastic support the present compensated portion of the tharsis topography could be attributed to volcanic or magmatic crustal thickening or depletion of the underlying mantle large core models appropriate to the present mars produce too many plumes to account for just two major volcanic centers i e tharsis and elysium mantle plume activity could be focussed beneath regions like tharsis if fracturing or thinning of the lithosphere in these regions has facilitated magma and heat transport across the lithosphere a similar mechanism could be responsible for clustering of coronae on venus there are no deep seated active linear upwellings in the venus models that could be associated with linear spreading centers in aphrodite if linear spreading is actually occurring in aphrodite the phenomenon is probably a shallow passive one similar to mid ocean ridges on earth

valles marineris mars wet debris flows and ground ice abstract detailed study of the valles marineris equatorial troughs suggests that the landslides in that area contained water and probably were gigantic wet debris flows one landslide complex generated a channel that has several bends and extends for 250 km further support for water or ice in debris masses includes rounded flow lobes and transport of some slide masses in the direction of the local topographic slope differences in speed and emplacement efficiency between martian and terrestrial landslides can be attributed to the entrainment of volatiles on mars but they can also be explained by other mechanisms support that the wall rock contained water comes from the following observations 1 the water within the landslide debris must have been derived from wall rock 2 debris appears to have been transported through tributary canyons 3 locally channels emerged from the canyons 4 the wall rock apprarently disintegrated and flowed easily and 5 fault zones within the troughs are unusually resistant to erosion the study further suggests that in the equatorial region of mars material below depths of 400 800 m was not desiccated during the time of landslide activity within the last billion years of martian history therefore the martian ground water or groundice reservoir if not a relic from ancient times must have been replenished

rheological constraints on martian landslides we use a dynamic finite difference model to simulate martian landslides in the valles marineris canyon system and olympus mons aureole using three different modal rheologies frictional bingham and power law the frictional and bingham modes are applied individually fluidized rheology is treated as a combination of frictional and power law modes general fluidization can include pore pressure contributions whereas acoustic fluidization does not we find that general fluidization most often produces slides that best match landslide geometry in the valles marineris this implies that some amount of supporting liquid or gas was present in the material during failure the profile of the olympus mons aureole is not well matched by any landslide model suggesting an alternative genesis in contrast acoustic fluidization produces the best match for a lunar slide a result anticipated for dry crust with no overlying atmosphere the presence of pressurized fluid during valles marineris landsliding may be due to liquid water beneath a thin cryosphere 1 2 km or flash sublimation of co2

svalbard summer melting continentality and sea ice extent from the lomonosovfonna ice core we develop a continentality proxy 1600 1930 based on amplitudes of the annual signal in oxygen isotopes in an ice core we show via modeling that by using 5 and 15 year average amplitudes the effects of diffusion and varying layer thickness can be minimized such that amplitudes then reflect real seasonal changes in 18o under the influence of melt a model of chemical fractionation in ice based on differing elution rates for pairs of ions is developed as a proxy for summer melt 1130 1990 the best pairs are sodium with magnesium and potassium with chloride the continentality and melt proxies are validated against twentieth century instrumental records and longer historical climate proxies in addition to summer temperature the melt proxy also appears to reflect sea ice extent likely as a result of sodium chloride fractionation in the oceanic sea ice margin source area that is dependent on winter temperatures we show that the climate history they depict is consistent with what we see from isotopic paleothermometry continentality was greatest during the little ice age but decreased around 1870 20 30 years before the rise in temperatures indicated by the 18o profile the degree of summer melt was significantly larger during the period 1130 1300 than in the 1990s

ages of valles marineris mars landslides and implications for canyon history the chronology of landslides of valles marineris the equatorial trough system of mars has been investigated by a crater population study valles marineris landslides have widespread debris aprons which offer a remarkable opportunity to study the crater population with high resolution images from mars orbiter camera moc and from mars odyssey thermal emission imaging system themis sixty six ages were determined within valles marineris including 56 landslide ages and 10 ages of the previous termcanyonnext term floor results reveal that landslides of valles marineris system of previous termcanyonsnext term occurred during a widespread period of time between 3 5 gy and 50 my in some locations the previous termcanyonnext term floor has an apparent age of 3 5 gy suggesting that at least locally within valles marineris no major refreshing processes have occurred for 3 5 gy the temporal repetitivity of landslides implies that the triggering mechanisms of the landslides are reproducible in time landslides have the same features whatever their age the dynamic of these landslides is probably the same either with intervention of water up to recently the last 100 my or without water since 3 5 gy

thick shell tectonics on one plate planets applications to mars a theory for stress distributions in thick lithospheric shells on one plate planets is developed based on the zero frequency equations of a self gravitating elastic spherical shell overlying a strengthless fluid stress distributions in lithospheres are reviewed for both the compensated and flexural modes in the former case surface stresses only depend on surface topography while for the latter case it is shown for long wavelengths that stress trajectories are mainly dependent on the lithospheric lateral density distribution and not on elastic properties computational analyses are carried out for mars and it is found that isostatically compensated models correctly predict the graben structure in the immediate tharsis region and a flexural loading model is satisfactory in explaining the graben in the regions surrounding tharsis a three stage model is hypothesized for the evolution of tharsis isostasy with north south graben formation on tharsis followed by flexural loading and radial graben formation on the perimeter of tharsis followed by a last stage of loading with little or no regional deformation this model is consistent with the martian lithosphere monotonically thickening over geologic time

holocene glacial history of svalbard status perspectives and challenges abstract we synthesize the current understanding of glacier activity on svalbard from the end of the late pleistocene 12 000 yrs before present to the end of the little ice age c 1920 ad our glacier history is derived from the svalhola database the first compilation of holocene geochronology for svalbard and the surrounding waters including over 1 800 radiocarbon terrestrial cosmogenic nuclide and optically stimulated luminescence ages data have been categorized by geological setting uniformly re calibrated quality assessed and ultimately used to constrain glacier fluctuations deglaciation ice free conditions glacier re advances and ice marginal positions we advance existing knowledge by mapping the extent and distribution of ice cover during the holocene glacial maximum and the glacial minimum as well as present retreat rates and percentages within early holocene fjord systems throughout the holocene svalbard glaciers have responded to a varying combination of climatic environmental and dynamic driving factors which influence both the extent and behavior of ice margins we discuss the complexities of glacier systems and their dynamics in response to changes in climate this review provides a holistic state of the art of holocene glaciers on svalbard suitable for orienting future works which address gaps in our current knowledge

separation of melting and environmental signals in an ice core with seasonal melt we examine the impact of melt water percolation on the soluble ion chemical record from the lomonosovfonna ice core principle component analysis shows that melting produces only simple changes bet

sulfate source inventories from a svalbard ice core record spanning the industrial revolution 1 the 800 year sulfate record from lomonosovfonna was analyzed by a novel multiple linear regression algorithm that attempts to explain sulfate variability in terms of other chemical species measured in the core and sulfur emission inventories we use three statistical approaches to determine sulfate sources we examine trends using singular spectrum analysis with confidence intervals finding clear evidence that anthropogenic sources are important but not dominant we use cross wavelet coherence to examine significant multidecadal covariance in terrestrial sulfate but our main tool is multiple regression analysis of the sulfate dependency on other ions and anthropogenic emission inventories models are fitted in a moving time window of typically 50 years length explaining 80 of the sulfate variance a suite of model predictors are examined and the variation in relative magnitudes of the model coefficients along the core can be used to infer variations in the strength of various sulfate sources we observe large changes in sulfate sources at the end of the little ice age associated with changes in barents sea marine productivity changes in north atlantic sulfate input and a long lasting period of disturbance caused by the large laki volcanic eruption modeling sulfur emission inventories shows that western europe contributes about 15 of the sulfate budget with essentially no input from other regions in contrast with predictions from global circulation models incorporating sulfur chemistry multidecadal cycles are mainly confined to the little ice age and most likely associated with increased storminess and enhanced deposition of both marine aerosol and biogenic sulfate from the atlantic ocean the model residuals do not show a normal distribution but display very large spikes unexpectedly those significant at the 99 level can be closely matched to major volcanic eruptions using independent dating methods the 20th century sulfate in the core is inventoried as sea salt 15 terrestrial 10 volcanic 5 10 western european anthropogenic 10 25 barents sea biogenic 20 40 and atlantic biogenic 10 15

study of phyllosilicates and carbonates from the capri chasma region of valles marineris on mars based on mars reconnaissance orbiter compact reconnaissance imaging spectrometer for mars mro crism observations abstract spectral reflectance data from the mro crism mars reconnaissance orbiter compact reconnaissance imaging spectrometer for mars of capri chasma a large canyon within valles marineris on mars have been studied results of this analysis reveal the presence of minerals such as phyllosilicates illite smectite montmorillonite and carbonates ankerite and manganocalcite these minerals hint of the aqueous history of noachian time on mars phyllosilicates are products of chemical weathering of igneous rocks whereas carbonates could have formed from local aqueous alteration of olivine and other igneous minerals four different locations within the capri chasma region were studied for spectral reflectance based mineral detection the study area also shows the spectral signatures of iron bearing minerals e g olivine with carbonate indicating partial weathering of parent rocks primarily rich in ferrous mineral the present study shows that the minerals of capri chasma are characterized by the presence of prominent spectral absorption features at 2 31 m 2 33 m 2 22 m 2 48 m and 2 52 m wavelength regions indicating the existence of hydrous minerals i e carbonates and phyllosilicates the occurrence of carbonates and phyllosilicates in the study area suggests the presence of alkaline environment during the period of their formation results of the study are important to understand the formation processes of these mineral assemblages on mars which may help in understanding the evolutionary history of the planet

morphology evolution and tectonics of valles marineris wallslopes mars abstract hillslopes up to 11 km in height can be found along the walls of the valles marineris troughs the widest and deepest troughs are grabens in which tectonics probably exerted the primary control on the wall morphology geographical variations in the wall morphology and profiles show that they result from complex persistent tectonic influences and that significant changes in erosional processes occurred during this evolution from late hesperian to late amazonian preliminary calculations suggest that about 85 95 of the fault controlled wall relief probably formed in an ancient stage prior to this transitional period a study of the volatile content of the wall rocks based upon the morphology and distribution of impact craters on the surrounding plateaus shows that extreme erosional widening of the central valles marineris troughs occurred during the ancient stage of high ground ice content during the subsequent recent stage of tectonic and morphological evolution the wall materials were partly desiccated

effects of elevation and ridged plains thicknesses on martian crater ejecta morphology relationships between the distribution of martian crater ejecta morphologies and both elevation and ridged plains thicknesses have been investigated we observed a slight correlation between elevation and the distribution of ejecta types for the ridged plains but not for regions of the dissected cratered plateau unit a stronger correlation was identified between the thicknesses of lunae and hesperia plana two major occurrences of the ridged plains and the complexity of ejecta morphologies for a given crater size range the complexity of the ejecta increases with decreasing thicknesses of the ridged plains because more of the lower unit is excavated where the upper layer is thin we conclude that some property of the lower layer increases ejecta complexity one possible explanation is that the lower layer may fracture to smaller ejecta sizes during excavation thus relatively more ejecta can be entrained by the martian atmosphere in areas where the ridged plains are thin another possibility is that a greater volatile content within the lower layer may result in increased fluidization both by vapor expansion during impact resulting in increased brecciation within the lower layer and by the incorporation of volatiles within the ejecta the slight relationship between elevation and the distribution of ejecta types probably results from a slight correlation between elevation and ridged plains thicknesses within lunae planum this effect appears significant within our data for the ridged plains because almost half of our data were obtained in this region

ratios of mg2 na in snowpack and an ice core at austfonna ice cap svalbard as an indicator of seasonal melting snowpack and ice core samples were collected from the dome of austfonna ice cap svalbard in the spring of both 1998 and 1999 the samples were analyzed for anions cations ph liquid electrical conductivity and oxygen isotopes concentrations of chemical components in snowpack with a history of melting were much lower than those in unmelted snowpack there was a clear difference between mg 2 na ratios previously in melted snowpack 0 011 0 02 and in unmelted snowpack 0 11 0 02 we propose that the mg 2 na ratio can be used as an indicator of whether or not firn or bubbly ice in the austfonna ice core has experienced melt percolation the mg 2 na ratio indicates that firn or bubbly ice prior to ad 1920 was much less affected by melt percolation than firn or bubbly ice formed after 1920

termination of a 6 year ridge spreading event observed using a seafloor seismic network on the endeavour segment juan de fuca ridge 1 we present automatically determined epicenters and magnitudes for 36 523 earthquakes recorded along the endeavour segment between august 2003 and october 2006 using a local ocean bottom seismometer obs network the catalog is dominated by two swarm sequences in january and february 2005 in the vicinity of the endeavour overlapping spreading center which included earthquakes in west valley the northern portion of the endeavour segment southwest endeavour valley and the endeavour vent fields these swarms are attributed to volcanism including a dike intrusion on the northern endeavour in february 2005 and smaller diking events on the propagating tip of the west valley segment in both swarms the dike on the northern endeavour propagated to the south which is inconsistent with magma sourced from the axial magma chamber beneath the elevated central portion of the segment following the swarms seismic activity on the endeavour segment decreased on average to 15 of pre swarm values and almost ceased at the segment ends we infer that a 6 year non eruptive event that started with a swarm in 1999 and finished with the 2005 swarms ruptured the entire segment and relieved plate spreading stresses the inferred coupling between the 1999 and 2005 events the observation of extensive precursory activity prior to the 2005 swarms and the interaction between seismically active regions during the swarms is consistent with static triggering with delays influenced by viscoelastic relaxation hydraulic diffusion and magma withdrawal and replenishment

dark materials in valles marineris indications of the style of volcanism and magmatism on mars rifting on the equatorial canyon system of valles marineris provides a unique view of the interior of the martian crust to depths reaching 7 km exposing several in situ bedrock units which testify to past volcanic and magmatic processes on mars a thick regionally extensive deposit observed in coprates and juventae chasmata is interpreted on the basis of spectral reflectance erosional morphology and tendency for eolian mobilization to be composed of mafic glass possibly an ancient martian analogue of the lunar terra mantling deposits spectral mapping suggests that the dark floor covering materials in the lower canyons are derived from this unit a series of cliffs in the ophir chasma wall rock is interpreted to be exposures of resistant bedrock the spectral signature of this massive and uniform unit most closely resembles that of terrestrial mafic rocks altered to or coated by crystalline hematite application of computer mapping techniques to probable young volcanic materials in the central troughs yields an inferred distribution of volcanic activity consistent with the interpretation of extrusion along faults near the margins of the canyon floors this result supports the hypothesis that the valles originated through tectonic extension

the 800 year long ion record from the lomonosovfonna svalbard ice core we present a high resolution record of water soluble ion chemistry from a 121 m ice core spanning about 800 years the core is well dated to 2 3 depth using cycle counting and reference horizons and a simple but close fitting model for the lower 1 3 of the core this core suffers from modest seasonal melt and so we present concentration data in decadal running means to minimize percolation effects sea salt ions na cl mg2 and k account for more than 70 of all ions in general sea salt ion concentrations are rather variable and have no clear association with climatic variations sulfate with 74 being from non sea salt sources has higher concentrations than seen on vestfonna ice cap but lower than in ny alesund aerosols suggesting central spitsbergen receives more marine westerly air masses than ny alesund but more sulfate enriched easterly air masses than nordaustlandet clear anthropogenic impacts are found for sulfate nitrate and ammonium and probably excess chloride after the mid twentieth century with sulfate showing a significant rise by the end of the nineteenth century sulfate and methanesulfonate concentrations correlate well during the twentieth century and it is clear that most of the preindustrial sulfate is of biogenic origin terrestrial component ca2 has the highest concentrations in the coldest part of the little ice age suggesting more windy conditions transporting local terrestrial dust to the ice cap all ion concentrations decrease at the end of the twentieth century which reflects loss of ions by runoff with non sea salt magnesium being particularly sensitive to melting

records of sulfate and nitrate in an ice core from mount muztagata central asia 1 annually resolved ice core records of major soluble ions na nh4 k mg2 ca2 cl so42 and no3 covering the period 1907 2002 a d from mount muztagata in central asia are presented in this paper time series of major ion concentrations generally exhibit very similar temporal trends except no3 and nh4 statistical analyses show that the chemical composition in the muztagata ice core is predominantly controlled by terrestrial dust inputs originating from the extensive arid and semiarid regions of central asia however by comparison with the typical dust derived ion ca2 the so42 and no3 concentrations increase more rapidly after the mid 1970s and late 1970s respectively possibly indicating the strong anthropogenic contributions from then on the good agreements between so42 and no3 concentration records and their precursor gas emissions from central and southwest asia suggest the potential source regions contributing to the muztagata ice core records

tracking fin whales in the northeast pacific ocean with a seafloor seismic network ocean bottom seismometer obs networks represent a tool of opportunity to study fin and blue whales a small obs network on the juan de fuca ridge in the northeast pacific ocean in 2 3 km of water recorded an extensive data set of 20 hz fin whale calls an automated method has been developed to identify arrival times based on instantaneous frequency and amplitude and to locate calls using a grid search even in the presence of a few bad arrival times when only one whale is calling near the network tracks can generally be obtained up to distances of 15 km from the network when the calls from multiple whales overlap user supervision is required to identify tracks the absolute and relative amplitudes of arrivals and their three component particle motions provide additional constraints on call location but are not useful for extending the distance to which calls can be located the double difference method inverts for changes in relative call locations using differences in residuals for pairs of nearby calls recorded on a common station the method significantly reduces the unsystematic component of the location error especially when inconsistencies in arrival time observations are minimized by cross correlation

ages of rampart craters in equatorial regions on mars implications for the past and present distribution of ground ice we are testing the idea of squyres et al 1992 that rampart craters on mars may have formed over a significant time period and therefore the onset diameter minimum diameter of a rampart crater only reflects the ground ice depth at a given time we measured crater size frequencies on the layered ejecta of rampart craters in three equatorial regions to derive absolute model ages and to constrain the regional volatile history nearly all rampart craters in the xanthe terra region are 3 8 gyr old this corresponds to the noachian fluvial activity that region rampart crater formation declines in the hesperian whereas onset diameters minimum diameter increase no new rampart craters formed after the end of the hesperian 3 gyr this indicates a lowering of the ground ice table with time in the xanthe terra region most rampart craters in the valles marineris region are around 3 6 gyr old only one large probably amazonian aged 2 5 gyr rampart crater exists these ages indicate a volatile rich period in the early hesperian and a lowering of the ground ice table with time in the valles marineris study region rampart craters in southern chryse planitia which are partly eroded by fluvial activity show ages around 3 9 gyr rampart craters superposed on channels have ages between 1 5 and 0 6 gyr the onset diameter 3 km at 1 5 gyr in this region may indicate a relatively shallow ground ice table loss of volatiles due to diffusion and sublimation might have lowered the ground ice table even in the southern chryse planitia region afterwards in general our study implies a formation of the smallest rampart craters within and or shortly after periods of fluvial activity and a subsequent lowering of the ground ice table indicated by increasing onset diameter to the present these results question the method to derive present equatorial ground ice depths from the onset diameter of rampart craters without information about their formation time

marine geophysics where there s smoke there s fire seafloor vents spewing mineral rich plumes of hydrothermal fluid termed black smokers can persist at mid ocean ridges for decades or longer earthquake data indicate that ongoing magma injection may determine their locations

fin whale tracks recorded by a seismic network on the juan de fuca ridge northeast pacific ocean fin whale calls recorded from 2003 to 2004 by a seafloor seismic network on the endeavour segment of the juan de fuca ridge were analyzed to determine tracks and calling patterns over 150 tracks were obtained with a total duration of 800 h and swimming speeds from 1 to 12 km h the dominant inter pulse interval ipi is 24 s and the ipi patterns define 4 categories a 25 s single ipi and 24 30 s dual ipi produced by single calling whales a 24 13 s dual ipi interpreted as two calling whales and an irregular ipi interpreted as groups of calling whales there are also tracks in which the ipi switches between categories call rates vary seasonally with all the tracks between august and april from august to october tracks are dominated by the irregular ipi and are predominantly headed to the northwest suggesting that a portion of the fin whale population does not migrate south in the fall the other ipi categories occur primarily from november to march these tracks have slower swimming speeds tend to meander and are predominantly to the south the distribution of fin whales around the network is non random with more calls near the network and to the east and north

a new hypothesis for the origin and redistribution of sulfates in the equatorial region of western mars 1 the formation of sulfates on mars has been under debate since they were identified by several mars missions starting from the 1970s we propose that sulfates formed as evaporites in enclosed standing bodies of water in the valles marineris area following the early alteration of martian basaltic crust were then elevated by the tharsis uplift and transported together with rock materials to meridiani planum by periodic outbursts of water where they were deposited as sediments the proposed model comprehensively addresses all forms of sulfate occurrences near the equator in the western martian hemisphere and relates it to physiographic processes volcanic tectonic and sedimentary affecting the martian surface

assessing source areas of pollutants from studies of fly ash charcoal and pollen from svalbard snow and ice 1 temporal variations in the quantities of pollen charcoal and scp spheroidal carbonaceous particles contained in the lomonosovfonna ice core from svalbard and in the surface snow of the ice cap are presented the abundance of these microparticles is illustrated for the period a d 1850 1997 from the ice core together with detailed snow pit stratigraphies for summer 2001 to spring 2002 viewing scp and pollen together is a new approach with relevance for tracing the possible origin of contaminants the scp are related to the pollution source while the pollen gives an indication of the vegetation at the point of origin the deposition of scp on the ice is also compared with deposition of scp in northern fennoscandia for the period a d 1982 1997 the quantity of pollen and the pollen types recorded suggest an origin in fennoscandia rather than in north america the temporal pattern of both scp and charcoal deposition reflects that of europe but may also contains a local signal

unprecedented low twentieth century winter sea ice extent in the western nordic seas since a d 1200 we reconstructed decadal to centennial vari ability of maximum sea ice extent in the western nordic seas for a d 1200 1997 using a combination of a regional tree ring chronology from the timberline area in fennoscandia and d 18 o from the lomonosovfonna ice core in svalbard the reconstruction successfully explained 59 of the variance in sea ice extent based on the calibration period 1864 1997 the significance of the reconstruction statistics reduction of error coefficient of efficiency is computed for the first time against a realistic noise background the twentieth century sustained the lowest sea ice extent values since a d 1200 low sea ice extent also occurred before mid seventeenth and mid eighteenth centuries early fifteenth and late thirteenth centuries but these periods were in no case as persistent as in the twentieth century largest sea ice extent values occurred from the seventeenth to the nineteenth centuries during the little ice age lia with relatively smaller sea ice covered area during the sixteenth century mod erate sea ice extent occurred during thirteenth fifteenth centuries reconstructed sea ice extent variability is dominated by decadal oscillations frequently associated with decadal components of the north atlantic oscilla tion arctic oscillation nao ao and multi decadal lower frequency oscillations operating at 50 120 year sea ice extent and nao showed a non stationary rela tionship during the observational period the present low sea ice extent is unique over the last 800 years and results from a decline started in late nineteenth century after the lia

glacio chemical study spanning the past 2 kyr on three ice cores from dronning maud land antarctica 2 seasonally resolved chemical records the ammonium calcium and sodium concentrations from three intermediate depth ice cores drilled in the area of dronning maud land east antarctica have been investigated since all measurements were performed by a high resolution continuous flow analysis system for the first time seasonal signals of chemical trace species could be obtained from the interior of central antarctica over a period of approximately 2 millennia although the elevation as well as the accumulation rate differ between the drilling sites similar values were obtained by comparing mean concentrations spanning the last 900 years however a distinct lack of intersite correlation was found on decadal timescales despite a noticeable accumulation change apparent in one core no significant concentration change of all three species has occurred all the measured ions show clear seasonal signals over the whole records while the sea salt related component sodium peaks simultaneously with calcium the maximum ammonium concentration occurs in the snow with a time lag of 2 months after the sea salt peak more than 60 of the calcium concentration can be attributed to an ocean source elevated sodium concentrations were found within this millennium compared to mean values of the whole records but the spatially varying shape of the increase suggests that a possible climatic signal is biased by local deposition effects

volcanic rifting at martian grabens 1 a large fraction of surface extension on mars occurred at segmented grabens having width length ratios akin to oceanic rifts on earth association with volcanic landforms such as pit craters clearly suggests interconnection between tectonic and magmatic processes a martian rift evolution model is proposed on the basis of new geomorphological and structural interpretations of imagery high resolution digital elevation models dems scaled experimental modeling and three dimensional boundary element modeling of magmatic and tectonic processes and a comparison with terrestrial rifts the dems were obtained from mars observer laser altimeter viking orbiter stereo images or a combination of both comparison of terrestrial rifts included afar iceland and the east pacific rise the ambient extensional stress field induced by regional body forces is combined at depth with decompression melting and mantle plume thermal anomaly resulting in emplacement of elongated magma reservoirs along the grabens injection of dikes above the reservoirs and flood basalt eruption result in a reservoir underpressurization of up to hundreds of mpa and induces surface collapse each collapse event is associated with an eruption of volcanic volumes akin to those of individual flow eruptions in large terrestrial igneous provinces the geometry and mechanisms of graben formation and surface collapse are described and used to infer reservoir depth and width we conclude from this study that giant dike swarms akin to typical giant terrestrial dike swarms are unlikely to underlie the volcanic martian grabens on the basis one graben one dike rather every volcanic graben segment appears to own a local dike swarm perhaps analogous to the dike swarms in the icelandic fissure zones index terms 5475 planetology solid surface planets tectonics 8149 5480 planetology solid surface planets volcanism 8450 6225 planetology solar system objects mars 8121 tectonophysics dynamics convection currents and mantle plumes 8010 structural geology fractures and faults keywords rifting graben pit crater magma chamber dyke

corehole seismometer development for low noise seismic data in a long term seafloor observatory longstanding problems unique to marine seismology in contrast to land based studies include high levels of environmental noise unpredictable instru ment placement short measurement duration and lim ited numbers of instruments traditional instruments are deployed and recovered from a surface ship with no capability to verify data acquisition until the end of the experiment they are often poorly sited and usu ally poorly coupled to the seafloor experiments have typically been short in duration with only a minimum number of instruments the result of these logistical problems is high background noise sparse data recov ery compared to continental stations and low fidelity data in an effort to solve many of these problems we have developed and deployed corehole seismometers 1 90 hz into small boreholes drilled by an underwa ter drilling system using a tethered remotely operated vehicle rov the results are seismic data with a sig nificantly lower background noise level a lower thresh old for recognition of small events well oriented and useable horizontal seismograms and a much longer de ployment capability we present new data from these instruments and compare them with data from two types of traditional instruments deployed from a sur face ship these contemporaneous deployments were conducted during 1996 and 1997 in monterey bay

a 800 year record of nitrate from the lomonosovfonna ice core svalbard detailed chemical analysis of the 122 m relatively high altitude and lowmelt lomonosovfonna ice core provides the best dated record of nitrate from svalbard a very significant non linear trend present in the record shows a a rise in concentrations from the 12th to the mid 16th century b reasonably stable concentrations until the mid19th century c a rise in concentrations into the 20th century with d a rapid rise in the 1950s and e a decrease after the mid 1980s nitrate is well correlated with ammonium before 1920 and after 1960 but not in the intervening period the correlation between ammonium and nitrate concentrations indicates that ammonium nitrate nh4no3 has been common at lomonosovfonna there are also places in the core where nitrate is very closely associated with calcium

coupling of ocean bottom seismometers to sediment results of tests with the u s geological survey ocean bottom seismometer abstract the response of an ocean bottom seismometer obs to a transient pull that excites the natural obs sediment coupling resonance can be modeled as a mass spring dashpot system in which the resonant frequency and damping are functions of instrument mass and bearing radius and of the physical properties of the sediment primarily the shear modulus for the very soft sediments sometimes found on the sea floor this resonance may be within the main frequency band of interest 2 to 15 hz for many common instrument configurations to test the model and to find an anchor that would shift the coupling resonance to a higher frequency and decrease its amplitude we conducted a series of tests which measured the response of the vertical and horizontal components of the u s geological survey obs to transient pulls as a function of anchor configuration and sediment properties the tested anchors included a concrete flowerpot a tripod a plate and a perforated plate sites were on soft organic rich ooze and on firm sand several small shots were also fired at the ooze site in order to compare the response of the plate and flowerpot anchors to seismic signals for a given anchor at a given site the observed response was very repeatable we found that the model predicts the vertical coupling response quite well and that good vertical coupling can be achieved with the plate or perforated plate anchors the response to the horizontal pulls however was similar and resonant for all anchors

estimating range to a vocalizing fin whale using the timing and amplitude of multipath arrivals a semi automated method is described to range to vocalizing fin whales using the timing and amplitude of multipath arrivals measured on seafloor receivers calls are detected and multipath arrivals identified with a matched filter multipath times and relative amplitudes are predicted as a function of range by ray tracing because the direct and first water column multiple arrivals are not always observed different hypotheses for the observed arrival paths must be considered for two arrivals an amplitude threshold is used to determine if the first arrival is the direct path and if not the call is disregarded as distant when three or more arrivals are detected three hypotheses for the paths of arrivals are considered the solution is the hypothesis and range that minimizes the timing and optionally amplitude ratio or absolute amplitude residual the method is tested with data from two ocean bottom seismometers one on the juan de fuca ridge and the other in the cascadia basin solutions obtained by

methanesulfonic acid in a svalbard ice core as an indicator of ocean climate methanesulfonic acid msa is an atmospheric oxidation product of dimethyl sulfide produced by marine biota msa preserved in a svalbard glacier between 1920 and 1996 is compared with the sea surface temperature sst and sea ice extent of the surrounding ocean over the same period on decadal timescales high msa concentrations are found to be associated with warm sst and reduced sea ice extent msa appears to be influenced by climatic changes related to variations in the import of warm atlantic water to the barents sea atlantic water plays an important role in the arctic climate system therefore msa concentrations may indirectly reflect larger scale changes in the region and may be useful as a proxy for past climate

deep drilling of glaciers in eurasian arctic as a source of paleoclimatic records abstract results of the deep drilling 80 100 m of eurasian arctic glaciers svalbard severnaya zemlya and franz josef land from the middle of the 1970s to the end of the 1990s have been discussed all spectra of the techniques used for ice core and borehole studies results of ice core dating and major paleoclimatic conclusions have been analyzed particular emphasis has been placed on the problem of accuracy and comparison of dates suggested by different authors new integrated time scale for eurasian arctic glaciers based on the ice core dating of vetreniy ice cap graham bell island and franz josef land which covers the last 700 800 years has been developed methods and results of the new paleo temperature reconstructions have been analyzed

mobility of large rock avalanches evidence from valles marineris mars measurements of h l height of drop length of runout vs volume for landslides in valles marineris on mars show a trend of decreasing h l with increasing volume this trend which is linear on a log log plot is parallel to but lies above the trend for terrestrial dry rock avalanches this result and estimates of 10 4 to 10 5 pa yield strength suggest that the landslides were not water saturated as suggested by previous workers the offset between the h l vs volume trends shows that a typical martian avalanche must be nearly two orders of magnitude more voluminous than a typical terrestrial avalanche in order to achieve the same mobility this offset might be explained by the effects of gravity on flows with high yield strengths these results should prove useful to future efforts to resolve the controversy over the mechan ics of long runout avalanches

statistical extraction of volcanic sulphate from nonpolar ice cores 1 ice cores from outside the greenland and antarctic ice sheets are difficult to date because of seasonal melting and multiple sources terrestrial marine biogenic and anthropogenic of sulfates deposited onto the ice here we present a method of volcanic sulfate extraction that relies on fitting sulfate profiles to other ion species measured along the cores in moving windows in log space we verify the method with a well dated section of the belukha ice core from central eurasia there are excellent matches to volcanoes in the preindustrial and clear extraction of volcanic peaks in the post 1940 period when a simple method based on calcium as a proxy for terrestrial sulfate fails due to anthropogenic sulfate deposition we then attempt to use the same statistical scheme to locate volcanic sulfate horizons within three ice cores from svalbard and a core from mount everest volcanic sulfate is 5 of the sulfate budget in every core and differences in eruption signals extracted reflect the large differences in environment between western northern and central regions of svalbard the lomonosovfonna and vestfonna cores span about the last 1000 years with good extraction of volcanic signals while holtedahlfonna which extends to about ad1700 appears to lack a clear record the mount everest core allows clean volcanic signal extraction and the core extends back to about ad700 slightly older than a previous flow model has suggested the method may thus be used to extract historical volcanic records from a more diverse geographical range than hitherto

the methanesulfonic acid msa record in a svalbard ice core svalbard ice cores have not yet been fully exploited for studies of climate and environmental conditions in one recently drilled ice core from lomonosovfonna we have studied the methanesulfonic acid msa records in relation to temperature and sea ice under the present climatic conditions msa appears to be negatively correlated with the sea ice conditions in the barents sea and positively correlated with the instrumental temperature record from svalbard however prior to about 1920 the msa concentrations were about twice as high despite the more extensive sea ice coverage after exploring different possibilities we suggest that msa concentrations were higher in the 19th century than in the 20th century due to increased primary production in response to increased vertical stability of the sea surface layers caused by increased meltwater production from the more extensive sea ice cover thus the msa record from lomonosovfonna probably both is a measure of the regional sea ice variability on the multi decadal scale and reflects locally favorable conditions for marine biogenic dimethyl sulfide dms production on the sub decadal scale

ultra distal kamchatkan ash on arctic svalbard towards hemispheric cryptotephra correlation abstract rapidly deposited and geochemically distinct volcanic ash tephra markers represent a powerful chronological tool that enables precise dating and correlation of geological archives recent analytical advances now allow fingerprinting of non visible ash cryptotephra over thousands of kilometers this has opened up tantalizing possibilities for the intercontinental synchronization of records we present geochemical evidence to demonstrate that ash from a svalbard lake sediment core correlates to the kamchatkan ks 2 eruption by expanding the known dispersal range of cryptotephra by thousands of kilometers and linking the pacific and atlantic arctic this study raises cryptotephra analysis to a new level also the presented findings mark a step towards a hemispheric tephrochronological framework finally this study highlights the importance of looking beyond proximal volcanic sources to find a correlation

small rampart craters in an equatorial region on mars implications for near surface water or ice small onset diameters 1 km of rampart craters were identified in high resolution stereo camera hrsc imagery in the equatorial region of the valles marineris plateaus this is in contrast to previous global studies based on viking imagery which showed onset diameters in the range of 4 km to 7 km in equatorial regions the observed small rampart craters show morphologically eroded ejecta blankets this indicates a formation in the early martian history when erosion rates were higher volatile rich target material might have been available shortly after the formation of the hesperian aged plateaus surrounding valles marineris and this is in agreement with the reported hesperian fluvial activity in this region the lack of fresh small rampart craters indicates a lowering of the ground ice table with time

origin and evolution of the layered deposits in the valles marineris mars abstract thick sequences of layered deposits are found in the martian valles marineris they exhibit fine nearly horizontal layering and are present as isolated plateaus of what may have once been more extensive deposits individual sequences of layered deposits are as thick as 5 km the greatest total thicknesses of deposits are found in candor ophir and melas chasmata individual layer thicknesses range from about 70 to 300 m some tilting of sequences is observed but at the best image resolutions no angular unconformities are detectable in the layers the sequences of events in the canyons as deduced from morphologic and stratigraphic evidence was 1 graben formation in response to the tharsis uplift 2 canyon wall retreat and canyon enlargement roughly contemporaneous with formation of the layered deposits 3 deep erosion of the layered deposits 4 landsliding of the canyon walls and 5 eolian erosion of the layered deposits perhaps continuing up to the present we consider four hypotheses for the origin of the layered deposits they are eolian deposits they are remnants of the material that makes up the canyon walls they are deposits of explosive volcanic eruptions or they were deposited in standing bodies of water the rhythmic nature of the layers and their lateral continuity horizontality great thickness and stratigraphic relationships with other units in the canyons all appear most consistent with deposition in an aqueous environment if standing bodies of water existed in the valles marineris they were almost certainly ice covered there are three ways in which sediment could have entered an ice covered lake down through the ice cover up from the lake bottom or in from the lake margins layers of sediment could have been transported downward through an ice cover by foundering or rayleigh taylor instabilities but it is not clear whether there was a viable mechanism for repeatedly accumulating thick sediment layers on top of the ice cover subaqueous volcanic eruption on the lake bottom does not suffer from many of the morphologic arguments that make origin by subaerial volcanism seem improbable while this mechanism is attractive there are no eruptive centers observed and there is no other direct evidence to support it because canyon enlargement took place at roughly the same time as layer deposition debris from the canyon walls is an obvious and likely source for some of the material in the layered deposits however the volume of material removed from the canyon walls may be insufficient to account for all of the presently observed material we conclude that there are several geologically feasible but as yet unproven mechanisms that could have led to formation of thick deposits in ice covered paleolakes in the valles marineris present data are insufficient to choose conclusively among the various possibilities several types of data from the mars observer mission will be useful in further characterizing the deposits and clarifying the process of their origin the deposits should be considered important targets for a future mars sample return mission

effect of periodic melting on geochemical and isotopic signals in an ice core from lomonosovfonna svalbard 1 we examine the quality of atmospherically deposited ion and isotope signals in an ice core taken from a periodically melting ice field lomonosovfonna in central spitsbergen svalbard the aim is to determine the degree to which the signals are altered by periodic melting of the ice we use three diagnostics 1 the relation between peak values in the ice chemical and isotopic record and ice facies type 2 the number of apparent annual cycles in these records compared with independently determined number of years represented in the ice core and 3 a statistical comparison of the isotopic record in the ice core and the isotope records from coastal stations from the same region we find that during warm summers as much as 50 of the annual accumulation may melt and percolate into the firn in a median year this decreases to similar to25 as a consequence of percolation the most mobile acids show up to 50 higher concentrations in bubble poor ice facies compared with facies that are less affected by melt most of the other chemical species are less affected than the strong acids and the stable water isotopes show little evidence of mobility annual or biannual cycles are detected in most parameters and the water isotope record has a comparable statistical distribution to isotopic records from coastal stations we conclude that ice cores from sites like lomonosovfonna contain a useful environmental record despite melt events and percolation and that most parameters preserve an annual or in the worst cases a biannual atmospheric signal

deuterium excess record from a small arctic ice cap in this paper we present a deuterium excess d record from an ice core drilled on a small ice cap in svalbard in 1997 the core site is located at lomonosovfonna at 1255 m asl and the analyzed time series spans the period 1400 1990 a d the record shows pronounced multidecadal to centennial scale variations coherent with sea surface temperature changes registered in the subtropical to southern middle latitude north atlantic during the instrumental period we interpret the negative trend in the deuterium excess during the 1400s and 1500s as an indication of cooling in the north atlantic associated with the onset of the little ice age consistently positive anomalies of d after 1900 peaking at about 1950 correspond with well documented contemporary warming yet the maximum values of deuterium excess during 1900 1990 are not as high as in the early part of the record pre 1550 this suggests that the sea surface temperatures during this earlier period of time in the north atlantic to the south of approximately 45 degrees n were at least comparable with those registered in the 20th century before the end of the 1980s we examine the potential for a cold bias to exist in the deuterium excess record due to increased evaporation from the local colder sources of moisture having isotopically cold signature it is argued that despite a recent oceanic warming the contribution from this local moisture to the lomonosovfonna precipitation budget is still insufficient to interfere with the isotopic signal from the primary moisture region in the midlatitude north atlantic

layering stratigraphy of eastern coprates and northern capri chasmata mars abstract distinct competent layers are observed in the slopes of eastern coprates chasma part of the valles marineris system on mars our observations indicate that the stratigraphy of coprates chasma consists of alternating thin strong layers and thicker sequences of relatively weak layers the strong competent layers maintain steeper slopes and play a major role in controlling the overall shape and geomorphology of the chasmata slopes the topmost competent layer in this area is well preserved and easy to identify in outcrops on the northern rim of coprates chasma less than 100 m below the southern ophir planum surface the volume of the topmost emplaced layer is at least 70 km 3 and may be greater than 2100 km 3 if the unit underlies most of ophir planum the broad extent of this layer allows us to measure elevation offsets within the north rim of the chasma and in a freestanding massif within coprates chasma where the layer is also observed rim outcrop morphology and elevation differences between ophir and aurorae plana may be indicative of the easternmost extent of the topmost competent layer these observations allow an insight into the depositional processes that formed the stratigraphic stack into which this portion of the valles marineris is carved and they present a picture of some of the last volcanic activity in this area furthermore the elevation offsets within the layer are evidence of significant subsidence of the massif and surrounding material