rapid circulation of warm subtropical waters in a major glacial fjord in east greenland the recent rapid increase in mass loss from the greenland ice sheet is primarily attributed to an acceleration of outlet glaciers oceanographic data obtained in summer 2008 show that subtropical waters that reside year round in the shelf ocean off greenland continuously enter a large glacial fjord in east greenland and contribute to melting at the glacier terminus the recent rapid increase in mass loss from the greenland ice sheet1 2 is primarily attributed to an acceleration of outlet glaciers3 4 5 one possible cause of this acceleration is increased melting at the ice ocean interface6 7 driven by the synchronous warming8 9 10 of subtropical waters offshore of greenland however because of the lack of observations from greenland s glacial fjords and our limited understanding of their dynamics this hypothesis is largely untested here we present oceanographic data collected in sermilik fjord east greenland by ship in summer 2008 and from moorings our data reveal the presence of subtropical waters throughout the fjord these waters are continuously replenished through a wind driven exchange with the shelf where they are present all year the temperature and renewal of these waters indicate that they currently cause enhanced submarine melting at the glacier terminus key controls on the melting rate are the volume and properties of the subtropical waters on the shelf and the patterns of along shore winds suggesting that the glaciers acceleration has been triggered by a combination of atmospheric and oceanic changes our measurements provide evidence for a rapid advective pathway for the transmission of oceanic variability to the ice sheet margins

asynchronous behavior of outlet glaciers feeding godthabsfjord nuup kangerlua and the triggering of narsap sermia s retreat in sw greenland we thank w dryer and d podrasky for assistance with fieldwork and l kenefic for assisting with digitizing glacier front positions ch2 m hill polar services and air greenland provided logistics support the spot 5 images used for the 2008 dem were provided by the spirit program centre national d etudes spatiales france the digitalglobe worldview images used for the 2014 dem were obtained from p morin terminus positions were derived from landsat images courtesy of the u s geological survey funding was provided by the us national science foundation nsf office of polar programs opp grants nsf plr 0909552 and nsf plr 0909333 cassotto is supported by nasa under the earth and space science fellowship program grant nnx14al29h k k kjeldsen acknowledges support from the danish council research for independent research grant no dff 409000151 k kjaer is thanked for his support during the earlier phases of this study on ice weather stations are operated by geus denmark within the programme for monitoring of the greenland ice sheet promice j mortensen acknowledges support from iiknn greenland defrost project of the nordic centre of excellence program interaction between climate change and the cryosphere and the greenland ecosystem monitoring programme www g e m dk s rysgaard was funded by the canada excellence research chair programme additional funding was provided by the geophysical institute university of alaska fairbanks and greenland climate research centre scientific editor h fricker and reviewers h jiskoot and g cogley provided very constructive feedback that helped improve the paper

submarine melting at the terminus of a temperate tidewater glacier leconte glacier alaska u s a heat fresh and sea water balances indicate that the late summer rate of submarine melting at the terminus of tidewater leconte glacier alaska u s a in 2000 was about 12md 1 w e averaged over the submerged face this is 57 of the estimated total ice loss at the terminus calving plus melting at this time submarine melting may thusprovidea significantcontributiontotheoverallablationofatidewaterglacier oceano graphic measurements conductivity temperature depth made 200 500m from the ter minus identified an isohaline 27ppt and isothermal 7 2 c layer extending from 130m depthto the fjord floor capping this is a 40mthick overflow plume distinguishedby high outflow rates low salinity 22 25ppt and lower temperatures 5 6 c mixing models indicate that fresh water comprised about11 of this plume it originates mostly as sub glacial discharge whose buoyancy drives convection at the terminus deep warm saline watersareincorporatedintotheplumeasitascends causingsubstantialmeltingoficealong the submarine face the calving terminus undergoes seasonal changes that coincide with changes in subglacial discharge and fjord water temperatures and we suggest that these fluctuations interminuspositionare directly relatedto changes in submarine melting

midlatitude atmosphere ocean interaction during el nino part i the north pacific ocean abstract atmosphere ocean experiments are experiments are used to investigate the formation of sea surface temperature sst anomalies in the north pacific ocean during fall and winter of the el nino year experiments in which the ncar community climate model ccm surface fields am used to force a mixed layer ocean model in the north pacific no air sea feedback are compared to simulations in which the ccm and north pacific ocean model are coupled anomalies in the atmosphere and the north pacific ocean during el nino are obtained from the difference between simulations with and without prescribed warm sst anomalies in the tropical pacific in both the forced and coupled experiments the anomaly pattern resembles a composite of the actual sst anomaly field during el nino warm ssts develop along the cost of north america and cold ssts form in the central pacific in the coupled simulations air sea interaction results in a 25 to 50 reduction in the magnitude of the sst and mixed layer depth anomalies

simulations of permian climate and comparisons with climate sensitive sediments abstract we use a climate model to simulate two intervals of permian climate the sakmarian ca 280 ma at the end of the major permo carboniferous glaciation and the wordian ca 265 ma we explore the climate sensitivity to various levels of atmospheric co2 concentration and to changes in geography and topography between the two periods the model simulates large seasonality and high aridity in the continental interiors of both hemispheres for both periods the northern summer monsoon weakens and the southern monsoon strengthens between the sakmarian and the wordian owing to changes in geography and topography the northern middle and high latitudes cool in winter between the sakmarian and wordian associated with northward shift of the continents this high latitude cooling strengthens the winter westerlies and shifts the maximum storm track precipitation south in the southern hemisphere the winter westerlies weaken from the sakmarian to the wordian starting the simulations with no permanent i

spring bloom dynamics in a subarctic fjord influenced by tidewater outlet glaciers godthabsfjord sw greenland in high latitude fjord ecosystems the spring bloom accounts for a major part of the annual primary production and thus provides a crucial energy supply to the marine food web however the environmental factors that control the timing and intensity of these spring blooms remain uncertain in 2013 we studied the spring bloom dynamics in godthabsfjord a large fjord system adjacent to the greenland ice sheet our surveys revealed that the spring bloom did not initiate in the inner stratified part of the fjord system but only started farther away from tidewater outlet glaciers a combination of out fjord winds and coastal inflows drove an upwelling in the inner part of the fjord during spring april may which supplied nutrient rich water to the surface layer this surface water was subsequently transported out fjord and due to this circulation regime the biomass accumulation of phytoplankton was displaced away from the glaciers in late may the upwelling weakened and the dominant wind direction changed thus reversing the direction of the surface water transport warmer water was now transported toward the inner fjord and a bloom was observed close to the glacier terminus overall our findings imply that the timing intensity and location of the spring blooms in godthabsfjord are controlled by a combination of upwelling strength and wind forcing together with sea ice cover the hydrodynamic regime hence plays a crucial role in structuring food web dynamics of the fjord ecosystem

gold in the oceans through time during sedimentation and diagenesis of carbonaceous shales in marine continental margin settings au is adsorbed from seawater and organic matter and becomes incorporated into sedimentary pyrite la icpms analysis of over 4000 sedimentary pyrite grains in 308 samples from 33 locations around the world grouped over 123 determined ages has enabled us to track in a first order sense the au content of the ocean over the last 3 5 billion years gold was enriched in the meso and neoarchean oceans several times above present values then dropped by an order of magnitude from the first great oxidation event goe1 through the paleoproterozoic to reach a minimum value around 1600 ma gold content of the oceans then rose with perturbations through the meso and neoproterozoic showing a steady rise at the end of the proterozoic 800 to 520 ma which most likely represents the effects of the second great oxidation event goe2 gold in the oceans was at a maximum at 520 ma when oxygen in the oceans rose to match current maximum values in the archean and proterozoic the au content of seawater correlates with the time distribution of high mg greenstone belts black shales and banded iron formations suggesting that increases in atmospheric oxygen and marine bio productivity combined with the higher background of au in komatiitic and mg rich basalts were the first order causes of the pattern of au enrichment in seawater we suggest the lack of major au deposits from 1800 to 800 ma is explained by the low levels of au in the oceans during this period

the 1100ma sturgeon falls paleosol revisited implications for mesoproterozoic weathering environments and atmospheric co2 levels abstract during the active rifting stage of the 1100 ma midcontinental rift in north america alluvial sediments were deposited intermittently between basalt flows on the north and south shores of present day lake superior at times of depositional quiescence paleosols developed in both areas on the alluvial sediments and on the antecedent basalt new results from the sturgeon falls paleosol in michigan characterizing the weathering processes at the time of its formation indicate moderate maturity high degrees of hydrolysis and leaching and a low degree of salinization geochemical provenance indices indicate a homogeneous source for the paleosols and in contrast to earlier work there is little evidence for k metasomatism as a result atmospheric co 2 levels of 4 6 pre industrial atmospheric levels were calculated using a mass balance model this result is consistent with previous calculations from nearly contemporaneous paleosols from the other side of the keweenawan rift and from the 100 ma younger sheigra paleosol in scotland the calculated co 2 values are also consistent with the calculated weathering environment proxies that indicate weak to moderate weathering at this time frame and suggest that the higher greenhouse gas loads indicated by paleoproterozoic paleosols had dissipated by the mid late mesoproterozoic

rapid submarine melting of the calving faces of west greenland glaciers widespread glacier acceleration has been observed in greenland in the past few years oceanographic observations taken in summer 2008 show that ocean waters melted a substantial fraction of ice along the calving fronts of three west greenland glaciers indicating that submarine melting has a profound influence on grounding line stability widespread glacier acceleration has been observed in greenland in the past few years1 2 3 4 associated with the thinning of the lower reaches of the glaciers as they terminate in the ocean5 6 7 these glaciers thin both at the surface from warm air temperatures and along their submerged faces in contact with warm ocean waters8 little is known about the rates of submarine melting9 10 11 and how they may affect glacier dynamics here we present measurements of ocean currents temperature and salinity near the calving fronts of the eqip sermia kangilerngata sermia sermeq kujatdleq and sermeq avangnardleq glaciers in central west greenland as well as ice front bathymetry and geographical positions we calculate water mass and heat budgets that reveal summer submarine melt rates ranging from 0 7 0 2 to 3 9 0 8 m d 1 these rates of submarine melting are two orders of magnitude larger than surface melt rates but comparable to rates of iceberg discharge we conclude that ocean waters melt a considerable but highly variable fraction of the calving fronts of glaciers before they disintegrate into icebergs and suggest that submarine melting must have a profound influence on grounding line stability and ice flow dynamics

estimating ocean heat transports and submarine melt rates in sermilik fjord greenland using lowered acoustic doppler current profiler ladcp velocity profiles submarine melting at the ice ocean interface is a significant term in the mass balance of marine terminating outlet glaciers however obtaining direct measurements of the submarine melt rate or the ocean heat transport towards the glacier that drives this melting has been difficult due to the scarcity of observations as well as the complexity of oceanic flows here we present a method that uses synoptic velocity and temperature profiles but accounts for the dominant mode of velocity variability to obtain representative heat transport estimates we apply this method to the sermilik fjord helheim glacier system in southeastern greenland using lowered acoustic doppler current profiler ladcp and hydrographic data collected in summer 2009 we find a mean heat transport towards the glacier of 29 10 9 w implying a submarine melt rate at the glacier face of 650 m a 1 t he resulting adjusted velocity profile is indicative of a multilayer residual circulation where the meltwater mixture flows out of the fjord at the surface and at the stratification maximum

characteristic variations of sea surface temperature with multiple time scales in the north pacific abstract temporal evolution and spectral structure of sea surface temperature sst anomalies in the north pacific over the last 37 years are investigated on the three characteristic time scales shorter than 24 months hf 24 60 months es and longer than 60 months dc the leading empirical orthogonal function eof for the dc time scale is characterized by a zonally elongated monopole centered at around 40 n 180 the leading eof for the hf time scale is somewhat similar to that for the dc time scale although there are two centers of action with the same polarity at the mid and western pacific the leading eof for the es time scale however exhibits a different pattern whose center of action at the mid pacific is located farther southeastward in the time evolution of the sst anomalies associated with the leading eof of the dc time scale several anomaly periods can be identified that last five years or longer the transition from a persistent period to another with the opposite polarity is gene

reconstruction of historical sea surface temperatures using empirical orthogonal functions abstract studies of climate variability often rely on high quality sea surface temperature sst anomalies although the high resolution national centers for environmental prediction formerly the national meteorological center optimum interpolation oi sst analysis is satisfactory for these studies the oi resolution cannot be maintained before november 1931 due to the lack of satellite data longer periods of ssts have come from traditional analyses of in situ ship and buoy sst observations alone a new interpolation method is developed using spatial patterns from empirical orthogonal functions e0fs that is a principal component analysis to improve analyses of sst anomalies from 1950 to 1981 the method uses the more accurate oi analyses from 1982 to 1993 to produce the spatial eofs the dominant eof modes which correspond to the largest variance are used as basis functions and are fit in a least squares sense to the in situ data to determine the time dependence of each mode a complete field

heat salt and freshwater budgets for a glacial fjord in greenland abstractin greenland s glacial fjords heat and freshwater are exchanged between glaciers and the ocean submarine melting of glaciers has been implicated as a potential trigger for recent glacier acceleration and observations of ocean heat transport are increasingly being used to infer the submarine melt rates the complete heat salt and mass budgets that underlie such methods however have been largely neglected here a new framework for exploring glacial fjord budgets is developed building on estuarine studies of salt budgets the heat salt and mass transports through the fjord are decomposed and new equations for calculating freshwater fluxes from submarine meltwater and runoff are presented this method is applied to moored records from sermilik fjord near the terminus of helheim glacier to evaluate the dominant balances in the fjord budgets and to estimate freshwater fluxes throughout the year two different regimes are found in the nonsummer months advective transports are balanced by

21st century evolution of greenland outlet glacier velocities earlier observations on several of greenland s outlet glaciers starting near the turn of the 21st century indicated rapid annual scale and large 100 increases in glacier velocity combining data from several satellites we produce a decade long 2000 to 2010 record documenting the ongoing velocity evolution of nearly all 200 of greenland s major outlet glaciers revealing complex spatial and temporal patterns changes on fast flow marine terminating glaciers contrast with steady velocities on ice shelf terminating glaciers and slow speeds on land terminating glaciers regionally glaciers in the northwest accelerated steadily with more variability in the southeast and relatively steady flow elsewhere intraregional variability shows a complex response to regional and local forcing observed acceleration indicates that sea level rise from greenland may fall well below proposed upper bounds

the seasonal circulation of the glacier bay alaska fjord system the seasonal circulation in glacier bay an alaskan fjord system with active tidewater glaciers is derived from oceanographic data collected on 13 cruises from june 1964 to september 1967 the fjord bottom waters were renewed annually between november and april by saline intrusion over the 69 m deep entrance sill in february the inlet waters were homogeneous with temperature of 3 c and salinity of 31 0 freshwater runoff derived from melting glacial ice stored runoff and precipitation led to a pycnocline formation in april or may the deepening pycnocline cut off the saline intrusion at the entrance sill the period from april to november was characterized by the downward mixing of brackish surface waters some evidence is presented for mixing by tidally induced internal waves these waves oscillate at twice the tidal frequency and have amplitudes of at least 50m vertical diffusion coefficients of the order of 5 0 cm2s 1 are reported the topographic influence of the glaciated terrain and retreating glaciers on the fjord circulation is demonstrated

quantifying energy and mass fluxes controlling godthabsfjord freshwater input in a 5 km simulation 1991 2012 abstractfreshwater runoff to fjords with marine terminating glaciers along the greenland ice sheet margin has an impact on fjord circulation and potentially ice sheet mass balance through increasing heat transport to the glacier front here the authors use the high resolution 5 5 km hirham5 regional climate model allowing high detail in topography and surface types to estimate freshwater input to godthabsfjord in southwest greenland model output is compared to hydrometeorological observations and while simulated daily variability in temperature and downwelling radiation shows high correlation with observations typically 0 9 there are biases that impact the results in particular overestimated albedo leads to underestimation of melt and runoff at low elevations in the model simulation 1991 2012 the ice sheet experiences increasing energy input from the surface turbulent heat flux up to elevations of 2000 m and shortwave radiation at all elevations southerly wind anomalies and declining

selenium and tellurium resources in kisgruva proterozoic volcanogenic massive sulphide deposit norway abstract the former mining site at kisgruva near kongsberg norway is primarily composed of worked sulphide ore deposits of hydrothermal origin which occur within precambrian metamorphic basement though the original targets at the kisgruva mine site were extraction of copper cu sulphur s and iron fe the sulphide ore also contains exceptionally high concentrations of selenium se and tellurium te hosted within selenides clausthalite and minor naumannite and tellurides hessite and minor altaite and tellurobismuthite both se and te are also present within the sulphide ore in pyrite and chalcopyrite which contain exceptionally high concentrations of up to 688 ppm se and 81 ppm te additionally oxidative weathering of the exposed bedrock has resulted in the accumulation of hyper enriched unconsolidated weathered crust deposits at surface se up to 1590 ppm te up to 63 ppm containing selenite seo32 and tellurite teo32 ions concentrations of se and te are subsequently higher in the weathering products than in the sulphide ore due to fixation on to organic matter 0 4 in weathered ore crusts jarosite formed from oxidation of sulphides from the primary ore ferric oxide and hydroxide phases goethite and haematite increasing demand for se and te to use in green technologies has led to the reassessment of these orebodies and their associated weathered ore crust deposits though these elements are currently considered mining contaminants this and similar sites may be of future economic importance particularly as demand for se and te continues to rise

sea surface temperature anomalies planetary waves and air sea feedback in the middle latitudes the mechanisms that contribute to the generation and damping of large scale mid latitude sea surface temperature sst anomalies are discussed the sst anomalies reflect primarily the response of the upper ocean to the changes in air sea fluxes that are associated with daily weather fluctuations heat flux forcing is dominant in the lower middle latitudes while wind driven entrainment may be most effective in the high latitudes advection by anomalous ekman current is generally less important and ekman pumping is negligible the sst anomalies decay in part because of entrainment effects associated with mixed layer deepening and oceanic mixing and in part because of heat exchanges with the atmosphere the three approaches commonly used to model the evolution of sst anomalies are reviewed case studies based on monthly or seasonal anomaly maps of the large scale sst and atmospheric anomalies numerical simulations with one dimensional mixed layer models and stochastic forcing models we stress the similarities in the different approaches and discuss their main advantages and limitations the response of the atmosphere to mid latitude sst anomalies is considered first we discuss the poorly known relationship between sst anomalies and diabatic heating using a crude assumption for the air sea coupling we consider a two layer quasi geostrophic channel model and discuss the stationary wave response to sst anomaly forcing and the resulting air sea feedback it is found that the back interaction of the sst anomalies onto the atmosphere causes a weak sst anomaly damping at large scales and a strong one at small scales the air sea coupling should also act as an eastward propagator for the sst anomalies the response of more realistic linear wave models to prescribed diabatic heating is then reviewed and it is suggested that realistic mid latitude sst anomalies have a weak influence on the atmospheric circulation corresponding to changes in the geopotential height of 10 30 m at most this order of magnitude is consistent with the results of general circulation model experiments and with the limited climate predictability associated with mid latitude sst anomalies

the ratio of tellurium and selenium in geological material as a possible paleo redox proxy abstract only few data for both tellurium and selenium in different geological materials including international reference materials have been available so far in this study the te se ratio has been investigated in more detail to provide a better understanding of the correlation of these two elements in the geological environment nine international reference materials irms and 79 different geological samples spanning a wide range of formation times and conditions from the paleoproterozoic to present were analyzed with quadrupole dynamic reaction cell drc icp ms these samples include basalts shales river and beach sediments loess dolomites a recent cold water coral precambrian manganese and iron formations and cenozoic marine ferromanganese nodules and crusts a wide range of concentrations between 0 01 and 1 5 g g for se and 0 01 and 90 g g for te was measured and the most interesting feature was found to be the te se ratio in the different geological matrices while most rock and sediment samples fall within the range of te se ratios typical of the average earth s crust a significant enrichment of te over se is evident for modern marine mn fe oxide precipitates with the most pronounced te enrichment found for hydrogenetic ferromanganese crusts which form under fully oxidizing conditions the apparent positive trend of the degree of te se fractionation with the redox potential of the formation environment suggests that the te se ratio may represent a potential paleo proxy for redox environments

severe selenium depletion in the phanerozoic oceans as a factor in three global mass extinction events abstract selenium se is one of the key trace elements required by all animal and most plant life and se deficiencies in the food chain cause pathologies or death here we show from new geochemical analyses of trace elements in phanerozoic marine pyrite that sustained periods of severe se depletion in the past oceans correlate closely with three major mass extinction events at the end of the ordovician devonian and triassic periods these represent periods of se depletion 1 5 2 orders of magnitude lower than current ocean abundances being within the range to cause severe pathological damage in extant se reliant organisms se depletion may have been one of several factors in these complex extinction scenarios recovery from the depletion extinction events is likely part of a natural marine cycle although rapid rises in global oxygen from sudden major increases in marine productivity and plant biomass after each extinction event may also have played a crucial role

tellurium and selenium in mesoproterozoic red beds abstract samples of red bed sediments in several mesoproterozoic successions contain enrichments of tellurium te including discrete telluride minerals the tellurides were neoformed during redox controlled diagenesis rather than representing mechanical concentrations of heavy minerals tellurium is enriched relative to selenium which may reflect erosion of archean and palaeoproterozoic rocks with high te contents high continentality during the mesoproterozoic would have limited the delivery of te and other trace elements to the oceans so accumulated te on the continents

tectonic setting and basin evolution of the bangemall supergroup in the northwestern capricorn orogen abstract the mesoproterozoic bangemall supergroup is the youngest depositional element within the capricorn orogen and comprises 4 to 10 km of fine grained siliciclastic and carbonate sedimentary rocks this succession is intruded by two generations of dolerite sills with ages of 1465 and 1070 ma field studies and geochronological data support a two fold subdivision of the bangemall supergroup into the c 1620 1465 ma edmund group and the c 1400 1070 ma collier group the principal syndepositional structural elements are parallel to the trend of major structures in the underlying ashburton fold belt and gascoyne complex these structures include the talga fault the faulted southwestern limb of the wanna syncline the lyons river fault and the northwest trending fault system that bounds the mangaroon and ti tree synclines the bangemall supergroup can be divided into six depositional packages defined by basal unconformities or major marine flooding surfaces packages 1 4 make up the edmund basin and consist of carbonate and siliciclastic shelf to basinal facies that are strongly controlled by synsedimentary movement along northwest trending basement faults source areas for the siliciclastic rocks were to the northwest northeast and southeast during deposition of packages 5 and 6 which form the collier basin the influence of the basement faults was less marked and the basin was filled with deltaic to deep marine siliciclastic facies that were derived from the northwest and southeast the bangemall supergroup has been frequently compared with proterozoic successions in northern australia but these successions are either too old or imprecisely dated to make meaningful correlations in addition the west and north australian cratons may not have been joined until the assembly of rodinia in the late mesoproterozoic

role of the gulf stream and kuroshio oyashio systems in large scale atmosphere ocean interaction a review abstract ocean atmosphere interaction over the northern hemisphere western boundary current wbc regions i e the gulf stream kuroshio oyashio and their extensions is reviewed with an emphasis on their role in basin scale climate variability sst anomalies exhibit considerable variance on interannual to decadal time scales in these regions low frequency sst variability is primarily driven by basin scale wind stress curl variability via the oceanic rossby wave adjustment of the gyre scale circulation that modulates the latitude and strength of the wbc related oceanic fronts rectification of the variability by mesoscale eddies reemergence of the anomalies from the preceding winter and tropical remote forcing also play important roles in driving and maintaining the low frequency variability in these regions in the gulf stream region interaction with the deep western boundary current also likely influences the low frequency variability surface heat fluxes damp the low frequency sst anomalies ove

north atlantic warming and the retreat of greenland s outlet glaciers mass loss from the greenland ice sheet quadrupled over the past two decades contributing a quarter of the observed global sea level rise increased submarine melting is thought to have triggered the retreat of greenland s outlet glaciers which is partly responsible for the ice loss however the chain of events and physical processes remain elusive recent evidence suggests that an anomalous inflow of subtropical waters driven by atmospheric changes multidecadal natural ocean variability and a long term increase in the north atlantic s upper ocean heat content since the 1950s all contributed to a warming of the subpolar north atlantic this led in conjunction with increased runoff to enhanced submarine glacier melting future climate projections raise the potential for continued increases in warming and ice mass loss with implications for sea level and climate

winter to winter recurrence of sea surface temperature salinity and mixed layer depth anomalies abstract the mean seasonal cycle of mixed layer depth mld in the extratropical oceans has the potential to influence temperature salinity and mixed layer depth anomalies from one winter to the next temperature and salinity anomalies that form at the surface and spread throughout the deep winter mixed layer are sequestered beneath the mixed layer when it shoals in spring and are then re entrained into the surface layer in the subsequent fall and winter here we document this re emergence mechanism in the north pacific ocean using observed ssts subsurface temperature fields from a data assimilation system and coupled atmosphere ocean model simulations observations indicate that the dominant large scale sst anomaly pattern that forms in the north pacific during winter recurs in the following winter the model simulation with mixed layer ocean physics reproduced the winter to winter recurrence while model simulations with observed ssts specified in the tropical pacific and a 50 m slab in the north pacific did not this difference between the model results indicates that the winter to winter sst correlations are the result of the re emergence mechanism and not of similar atmospheric forcing of the ocean in consecutive winters the model experiments also indicate that sst anomalies in the tropical pacific associated with el nino are not essential for re emergence to occur the recurrence of observed sst and simulated sst and sss anomalies are found in several regions in the central north pacific and are quite strong in the northern 50 n part of the basin the winter to winter autocorrelation of sss anomalies exceed those of sst since only the latter are strongly damped by surface fluxes the re emergence mechanism also has a modest influence on mld through changes in the vertical stratification in the seasonal thermocline

quantifying flow and stress in ice melange the world s largest granular material tidewater glacier fjords are often filled with a collection of calved icebergs brash ice and sea ice for glaciers with high calving rates this melange of ice can be jam packed so that the flow of ice fragments is mostly determined by granular interactions in the jammed state ice melange has been hypothesized to influence iceberg calving and capsize dispersion and attenuation of ocean waves injection of freshwater into fjords and fjord circulation however detailed measurements of ice melange are lacking due to difficulties in instrumenting remote ice choked fjords here we characterize the flow and associated stress in ice melange using a combination of terrestrial radar data laboratory experiments and numerical simulations we find that during periods of terminus quiescence ice melange experiences laminar flow over timescales of hours to days the uniform flow fields are bounded by shear margins along fjord walls where force chains between granular icebergs terminate in addition the average force per unit width that is transmitted to the glacier terminus which can exceed 107 n m increases exponentially with the melange length to width ratio these buttressing forces are sufficiently high to inhibit the initiation of large scale calving events supporting the notion that ice melange can be viewed as a weak granular ice shelf that transmits stresses from fjord walls back to glacier termini

the sturgeon falls paleosol and the composition of the atmosphere 1 1 ga bp a paleosol is exposed along the north bank of the sturgeon river some 25 km sw of baraga michigan the paleosol was developed on hydrothermally altered keweenawan basalt and is overlain by the jacobsville sandstone textures mineralogy and chemical composition change gradually upwards from unweathered metabasalt through the paleosol to the contact of the paleosol with the jacobsville sandstone many of these changes are similar to those in modern soils developed on basaltic rocks however k has clearly been added to the paleosol probably by solutions which had equilibrated with k feldspar in the jacobsville sandstone the keweenawan basalt was oxidized quite extensively during its conversion to greenstone during weathering the remaining fe2 was oxidized to fe3 and was retained in the paleosol the composition of the parent greenstone and its change during weathering can be used to define an approximate lower limit to the ratio of the o2 pressure to the co2 pressure in the atmosphere during the formation of the paleosol formula see text free o2 must have been present in the atmosphere 1 1 ga ago but its partial pressure could have been 10 3 times lower than in the atmosphere today

interdecadal variability over the north pacific in a multi century climate simulation interdecadal variability in the north pacific region is investigated in a 500 y control integration of the hamburg echam lsg coupled ocean atmosphere general circulation model the spectrum is predominantly red but a significant peak with a period of about 18 y is detected in the spectrum of sea surface temperature sst this peak is shown to be associated with an irregular oscillation that involves both the model ocean and atmosphere the sst sea level pressure and geopotential height at 500 hpa all undergo a primarily standing oscillation with an extensive monopole structure centered near the date line the surface anticyclone is situated to the northeast of the warm sst anomaly and there is a small westward tilt with height temporal changes are approximately in phase the anomalous surface heat flux accompanying the warm phase of sst is primarily out of the ocean but is compensated by anomalous warm advection by surface currents allowing the sst anomaly to persist oceanic thermocline anomalies propagate northward in the western pacific and lag the atmosphere indicating a disequilibrium with the atmosphere sub surface thermal advection appears to play an important role a comparison is made between the model s 18 y oscillation and oscillatory components identified in an analysis of the gisst observational sst dataset which have periods of approximately 6 and roughly 30 y

low temperature concentration of tellurium and gold in continental red bed successions there is very little understanding of tellurium te distribution and behaviour in sedimentary rocks a suite of 15 samples of reduction spheroids centimetre scale pale spheroids in otherwise red rock including samples from eight localities in triassic red beds across the british isles were mapped for te using laser ablation inductively coupled plasma mass spectrometry almost all showed enrichment in te in the cores of the spheroids relative to background red bed concentrations by up to four orders of magnitude some were also enriched over background in gold and or mercury in one case discrete telluride minerals were recorded the data show that te is mobile and can be concentrated in low temperature sedimentary environments controlled by redox variations the consistency in enrichment across widely separate localities implies that the enrichment is a normal aspect of red bed diagenesis and so likely to be controlled by a ubiquitous process such as microbial activity

the reemergence of sst anomalies in the north pacific ocean abstract sea surface temperature sst data and two different upper ocean temperature analyses are used to study the winter to winter recurrence of sst anomalies in the north pacific ocean the ssts recur when temperature anomalies that form in the deep ocean mixed layer in late winter early spring are isolated from the atmosphere in the summer seasonal thermocline and then reemerge at the surface when the mixed layer deepens during the following fall winter this reemergence mechanism is evaluated over the basin by correlating the time series of the leading pattern of ocean temperature anomalies in the summer seasonal thermocline 60 85 m in august september with sst anomalies over the course of the year the results indicate that the dominant large scale sst anomaly pattern that forms in the north pacific during late winter with anomalies of one sign in the central pacific and the opposite sign along the coast of north america is sequestered in the seasonal thermocline in summer and returns to the

simple coupled midlatitude climate models a set of simple analytical models is presented and evaluated for interannual to decadal coupled ocean atmosphere modes at midlatitudes the atmosphere and ocean are each in sverdrup balance at these long timescales the atmosphere s temperature response to heating determines the spatial phase relation between sst and sea level pressure slp anomalies vertical advection balancing heating produces high low slp lying east of warm cold sst anomalies as observed in the antarctic circumpolar wave acw the decadal north pacific mode and the interannual north atlantic mode zonal advection in an atmosphere with a rigid lid produces low slp east of warm sst however if an ad hoc equivalent barotropic atmospheric response is assumed high slp lies east of warm sst relaxation to heating produces behavior like the observed north atlantic decadal pattern with low slp over warm sst meridional advection in the atmosphere cannot produce the observed sst slp patterns the dominant balance in the ocean s temperature equation determines the phase speed of the modes the coupled mode is nondispersive in all models examined here indicating the need for additional processes for modes with an sst slp offset as observed in the acw and north pacific ekman convergence acting as a heat source causes eastward propagation relative to the mean ocean flow sverdrup response to ekman convergence acting on the mean meridional temperature gradient causes westward propagation relative to the mean ocean flow when the ocean temperature adjusts through surface heat flux alone the mode is advected by the mean ocean flow and is damped relaxation to heating in the atmosphere when operating with sverdrup response in the ocean produces the only complete solution presented here that exhibits growth with an e folding timescale of order 100 days this solution appears appropriate for the north atlantic decadal mode in northern hemisphere basins with meridional boundaries the same sets of dynamics create the observed sst slp phase relation an additional factor is the creation of sst anomalies through variations in the western boundary current strengths which are related to the zonally integrated wind stress curl over the whole basin if barotropic and hence fast adjustment is assumed the resulting positive feedback can maintain or strengthen the coupled anomalies in the north pacific and interannual north atlantic modes

spatially distributed runoff at the grounding line of a large greenlandic tidewater glacier inferred from plume modelling understanding the drivers of recent change at greenlandic tidewater glaciers is of great importance if we are to predict how these glaciers will respond to climatic warming a poorly constrained component of tidewater glacier processes is the near terminus subglacial hydrology here we present a novel method for constraining near terminus subglacial hydrology with application to marine terminating kangiata nunata sermia in south west greenland by simulating proglacial plume dynamics using buoyant plume theory and a general circulation model we assess the critical subglacial discharge if delivered through a single compact channel required to generate a plume that reaches the fjord surface we then compare catchment runoff to a time series of plume visibility acquired from a time lapse camera we identify extended periods throughout the 2009 melt season where catchment runoff significantly exceeds the discharge required for a plume to reach the fjord surface yet we observe no plume we attribute these observations to spatial spreading of runoff across the grounding line persistent distributed drainage near the terminus would lead to more spatially homogeneous submarine melting and may promote more rapid basal sliding during warmer summers potentially providing a mechanism independent of ocean forcing for increases in atmospheric temperature to drive tidewater glacier acceleration

interdecadal variability in a numerical model of the northeast pacific ocean 1970 89 abstract variations in the thermocline depth of the northeast pacific ocean during 1970 1989 are investigated using a reduced gravity numerical model forced by the local surface wind stress and at the southern land ocean boundary by a coastal kelvin wave signal three experiments are presented with forcings by wind only kelvin wave only and a combination of both the wind forcing generates an anticyclonic gyre circulation with mostly annual variations the kelvin waves along the coast excite rossby waves that propagate into the basin interior producing changes in upper layer thickness related to changes in thermocline depth that last for years after the kelvin signal has passed two sequential upwelling kelvin waves in 1973 and 1975 produce upwelling rossby waves that reduce the mean upper layer thickness by approximately 10 20 m during 1976 this shift is reinforced by later upwelling events lasting until the early 1980s the authors present a new hypothesis that the previously known climate shift o

impact of fjord dynamics and glacial runoff on the circulation near helheim glacier greenland to show that the melting circulation is affected by seasonal runoff from the glacier and by the fjord s externally forced currents and stratification the presence of light arctic and dense atlantic waters in the fjord in particular causes meltwater to be exported at depth and influences the vertical distribution of heat along the ice margin our results indicate that the melting circulation is more complex than hypothesized and influenced by multiple external parameters we conclude that the shape and stability of greenland s glaciers may be strongly influenced by the layering of the arctic and atlantic waters in the fjord as well as their variability

subglacial discharge driven renewal of tidewater glacier fjords the classic model of fjord renewal is complicated by tidewater glacier fjords where submarine melt and subglacial discharge provide substantial buoyancy forcing at depth here we use a suite of idealized high resolution numerical ocean simulations to investigate how fjord circulation driven by subglacial plumes tides and wind stress depends on fjord width grounding line depth and sill height we find that the depth of the grounding line compared to the sill is a primary control on plume driven renewal of basin waters in wide fjords the plume exhibits strong lateral recirculation increasing the dilution and residence time of glacially modified waters rapid drawdown of basin waters by the subglacial plume in narrow fjords allows for shelf waters to cascade deep into the basin wide fjords result in a thin boundary current of shelf waters that flow toward the terminus slightly below sill depth wind forcing amplifies the plume driven exchange flow however wind induced vertical mixing is limited to near surface waters tidal mixing over the sill increases in fjord transport of deep shelf waters and erodes basin stratification above the sill depth these results underscore the first order importances of fjord glacier geometry in controlling circulation in tidewater glacier fjords and thus ocean heat transport to the ice

ocean circulation and properties in petermann fjord greenland the floating ice shelf of petermann glacier interacts directly with the ocean and isthought to lose at least 80 of its mass through basal melting based on three opportunisticocean surveys in petermann fjord we describe the basic oceanography the circulationat the fjord mouth the hydrographic structure beneath the ice shelf the oceanic heatdelivered to the under ice cavity and the fate of the resulting melt water the 1100 m deepfjord is separated from neighboring hall basin by a sill between 350 and 450 m deep fjord bottom waters are renewed by episodic spillover at the sill of atlantic water from thearctic glacial melt water appears on the northeast side of the fjord at depths between200 m and that of the glacier s grounding line about 500 m the fjord circulation isfundamentally three dimensional satellite imagery and geostrophic calculations suggest acyclonic gyre within the fjord mouth with outflow on the northeast side tidal flowsare similar in magnitude to the geostrophic flow the oceanic heat flux into the fjordappears more than sufficient to account for the observed rate of basal melting cold low salinity water originating in the surface layer of nares strait in winter intrudes farunder the ice this may limit basal melting to the inland half of the shelf the melt rate andlong term stability of petermann ice shelf may depend on regional sea ice cover andfjord geometry in addition to the supply of oceanic heat entering the fjord

heavy metal sex and granites crustal differentiation and bioavailability in the mid proterozoic biogeochemical and genomic studies have suggested that the availability of trace metals has been essential to the progressive evolution of life on earth in particular the evolution of eukaryotes to diverse complex multicellular life has been related to the availability of trace metals the radiation of eukaryotes and the evolution of sex is timed as mesoproterozoic but at that time the metals may have been preferentially sequestered in a sulfidic deep ocean however the addition of a huge volume of new crust to form a supercontinent ca 1 9 ga including an unprecedented episode of within plate anorogenic magmatism led to an extraordinary new flux of metals to the upper crust in the late paleoproterozoic mesoproterozoic the appearance of sulfate evaporites from ca 1 7 1 6 ga indicates extensive weathering of metallic sulfides erosion of the supercontinent into mesoproterozoic sediments introduced key metals to near surface reservoirs providing an enhanced biogeochemical environment conducive to the expansion of an evolving biota

subannual and seasonal variability of atlantic origin waters in two adjacent west greenland fjords greenland fjords provide a pathway for the inflow of warm shelf waters to glacier termini and outflow of glacially modified waters to the coastal ocean characterizing the dominant modes of variability in fjord circulation and how they vary over subannual and seasonal time scales is critical for predicting ocean heat transport to the ice here we present a 2 year hydrographic record from a suite of moorings in davis strait and two neighboring west greenland fjords that exhibit contrasting fjord and glacier geometry kangerdlugssuaq sermerssua and rink isbrae hydrographic variability above the sill exhibits clear seasonality with a progressive cooling of near surface waters and shoaling of deep isotherms above the sill during winter to spring renewal of below sill waters coincides with the arrival of dense waters at the fjord mouth warm salty atlantic origin water cascades into fjord basins from winter to midsummer we then use seaglider observations at davis strait along with reanalysis of sea ice and wind stress in baffin bay to explore the role of the west greenland current and local air sea forcing in driving fjord renewal these results demonstrate the importance of both remote and local processes in driving renewal of near terminus waters highlighting the need for sustained observations and improved ocean models that resolve the complete slope trough fjord ice system

preservation of pre vegetational mixed fluvio aeolian deposits in a humid climatic setting an example from the middle proterozoic eriksfjord formation southwest greenland abstract sedimentological studies of a 30 m thick coastal cliff section within the middle proterozoic eriksfjord formation in western south greenland reveals three distinct types of fluvial sand sheet deposits that reflect perennial streams type i semi perennial streams type ii and ephemeral flash floods type iii perennial river sand sheets are characterised by co sets of medium scale trough cross beds interbedded with isolated medium and large scale high angle tabular cross beds indications of desiccation or subaerial exposure are absent semi perennial fluvial sand sheets consist predominantly of low angle cross beds interbedded with isolated sets of high angle tabular cross beds with common reactivation surfaces horizontal lamination and climbing ripple lamination form subordinate structures associated with the sand sheets are adhesion structures and 0 05 0 4 m thick sets of wind ripple lamination indicating periods of subaerial exposure and aeolian reworking high energy ephemeral flash flood sand sheets consist almost exclusively of planar parallel lamination and climbing ripple lamination with some isolated sets of low angle cross bedding scouring and internal truncation surfaces are common the three types of sand sheets are considered to reflect deposition under changing climatic conditions varying from humid to arid or semi arid aeolian deposits are preserved within the sand sheets showing characteristics of dominantly perennial flow punctuated by shorter periods of desiccation type ii while sand sheets showing features typical of arid and or semi arid flow conditions type iii contain no preserved aeolian deposits this selective preservation is interpreted to be a result of the combined effect of groundwater table level and fluvial style which in turn are inferred to have been controlled by the climatic regime the deposits show that during pre vegetational times the preservation of aeolian deposits under certain conditions may be more optimal in fluvial systems formed in a humid climate than in fluvial systems formed under semi arid or arid circumstances the occurrence of aeolian deposits within a precambrian succession of fluvial deposits therefore need not be an indication of the most arid environmental conditions

rapid changes in ice discharge from greenland outlet glaciers using satellite derived surface elevation and velocity data we found major short term variations in recent ice discharge and mass loss at two of greenland s largest outlet glaciers their combined rate of mass loss doubled in less than a year in 2004 and then decreased in 2006 to near the previous rates likely as a result of fast re equilibration of calving front geometry after retreat total mass loss is a fraction of concurrent gravity derived estimates pointing to an alternative source of loss and the need for high resolution observations of outlet dynamics and glacier geometry for sea level rise predictions

formation of archean batholith hosted gold veins at the lac herbin deposit val d or district canada mineralogical and fluid inclusion constraints the lac herbin deposit consists of a network of mineralized parallel steep reverse faults within the synvolcanic bourlamaque granodiorite batholith at val d or in the archean abitibi greenstone belt there are two related quartz tourmaline carbonate fault fill vein sets in the faults which consist of subvertical fault fill veins associated with subhorizontal veins the paragenetic sequence is characterized by a main vein filling ore stage including quartz tourmaline carbonate and pyrite hosted gold chalcopyrite tellurides pyrrhotite and cubanite inclusions most of the gold is located in fractures in deformed pyrite and quartz in equilibrium with chalcopyrite and carbonates with local pyrrhotite sphalerite galena cobaltite pyrite or tellurides petrography and microthermometry on quartz from the main vein filling ore stage reveal the presence of three unrelated fluid inclusion types 1 gold bearing aqueous carbonic inclusions arranged in three dimensional intragranular clusters in quartz crystals responsible for the main vein filling stage 2 barren high temperature aqueous moderately saline inclusions observed in healed fractures postdating the aqueous carbonic inclusions and considered as a remobilizing agent of earlier precipitated gold in late fractures and 3 barren low temperature aqueous high saline inclusions in healed fractures similar to the crustal brines reported throughout the canadian shield and considered to be unrelated to the gold mineralization at the lac herbin deposit the aqueous carbonic inclusions are interpreted to have formed first and to represent the gold bearing fluid which were generated contemporaneous with regional greenschist facies metamorphism in contrast the high temperature aqueous fluid dissolved gold from the main vein filling ore stage transported and reprecipitated it in late fractures during a subsequent local thermal event

ice dammed lake drainage cools and raises surface salinities in a tidewater outlet glacier fjord west greenland the drainage of ice dammed lakes in the form of outburst floods in greenland is detected regularly by remote sensing and these events are expected to occur more frequently in a warmer climate however their impact on ice sheet stability and neighboring water bodies is still unknown in this interdisciplinary study we investigate lake drainages from the greenland ice sheet into a west greenland fjord by analyzing simultaneous time series of satellite observations and direct hydrographic measurements of temperature and salinity in the fjord satellite images show that in general lake drainages have occurred quasiperiodically during the last decade a particular sequence of drainage events was observed by satellite in 2009 and was analyzed together with the first direct hydrographic observations signs of ice dammed lake drainages were observed by a downstream mooring located just below the intertidal zone the release of freshwater occurred at the fjord subsurface at a tidewater outlet glacier the downstream in water sequence of property changes in relation to these drainage events was observed as an almost immediate decrease in surface layer temperature 2 c followed within a week by the arrival of a high saline pulse 5 units with elevated salinity lasting for several days during the passage during lake drainages large amounts of relatively warm and saline intermediate water are brought to the near surface layers by entrainment processes near the glacier front and this influences the hydrography of the fjord but also impacts the ecosystem through upwelling of nutrient rich intermediate water

on the relationship between tropical and north pacific sea surface temperature variations abstract empirical orthogonal function analysis of winter sea surface temperature sst anomalies over the pacific domain 60 n 20 s reveals an el nino southern oscillation enso mode that is linked to the eastern north pacific and a north pacific mode that is linearly independent of enso the north pacific mode exhibits maximum amplitude and variance explained along 40 n west of 170 w ssts in this region have decreased by 1 5 c from 1950 to 1987 the cooling in winter has been associated with a strengthening of the overlying westerly winds

upper ocean thermal variations in the north pacific during 1970 1991 abstract a newly available extensive compilation of upper ocean temperature profiles was used to study the vertical structure of thermal anomalies between the surface and 400 m depth in the north pacific during 1970 1991 a prominent decade long perturbation in climate occurred during this time period surface waters cooled by 1 c in the central and western north pacific and warmed by about the same amount along the west coast of north america from late 1976 to 1988 comparison with data from coads suggests that the relatively sparse sampling of the subsurface data is adequate for describing the climate anomaly the vertical structure of seasonal thermal anomalies in the central north pacific shows a series of cold pulses beginning in the fall of 1976 and continuing until late 1988 that appear to originate at the surface and descend with time into the main thermocline to at least 400 m depth individual cold events descend rapidly 100 m yr 1 superimposed upon a slower cooling 15 m yr 1 the inter

weathering and paleosol formation in the 1 1 ga keweenawan rift abstract at 1 1 ga the north american craton began to rift resulting in flood style basaltic volcanism during the phase of active tectonism some of that basalt was weathered and redistributed by fluvial processes new observations near the northwestern shore of lake superior have also revealed the presence of seven paleosols formed on weathered immature sediments derived from the basalt that are described here for the first time only three other paleosols have previously been described from this part of the geologic record so these new paleosols represent a significant new discovery the paleosols are weakly developed and exhibit physical and chemical characteristics similar to phanerozoic entisols in contrast to many precambrian paleosols the keweenawen paleosols have been subject to minimal post burial alteration among the paleosols three distinct pedofacies are recognized 1 waterlogged gleyed fluvial proximal paleosols 2 dry fluvial distal paleosols and 3 cumulative fluvial proximal paleosols despite these facies differences using a combination of physical and chemical measures of weathering it is found that the paleosols are all derived from the same parental basalt with one of the paleosols showing an additional extra basinal rhyolitic component by considering the mass balance behaviour of a variety of alkali and alkaline earth elements it is possible to rule out significant potassium metasomatism suggesting that these paleosols may be particularly useful for paleoatmospheric and paleobiologic reconstructions and that they form an important new source of data about mesoproterozoic weathering

seasonality of decadal sea surface temperature anomalies in the northwestern pacific abstract the seasonality of the decadal sea surface temperature sst anomalies and the related physical processes in the northwestern pacific were investigated using a three dimensional bulk mixed layer model in the kuroshio oyashio extension koe region the strongest decadal sst anomaly was observed during december february while that of the central north pacific occurred during february april from an examination of the seasonal heat budget of the ocean mixed layer it was revealed that the seasonal scale enhancement of the decadal sst anomaly in the koe region was controlled by horizontal ekman temperature transport in early winter and by vertical entrainment in autumn the temperature transport by the geostrophic current made only a slight contribution to the seasonal variation of the decadal sst anomaly despite controlling the upper ocean thermal conditions on decadal time scales through the slow rossby wave adjustment to the wind stress curl when averaging over the entire koe region the cont

subglacial drainage evolution modulates seasonal ice flow variability of three tidewater glaciers in southwest greenland b j d was funded in the form of a phd studentship provided by the scottish association for geosciences environment and society sages and the university of st andrews uk j m l is supported by a ukri future leaders fellowship grant no mr s017232 1 d f would like to acknowledge the support of this work through the epsrc and esrc centre for doctoral training on quantification and management of risk and uncertainty in complex systems environments grant no ep l015927 1

the differences between early and midwinter atmospheric responses to sea surface temperature anomalies in the northwest atlantic abstract using an atmospheric global spectral model it is shown that the winter atmosphere in the midlatitudes is capable of reacting to prescribed sea surface temperature sst anomalies in the northwest atlantic with two very different responses the nature of the response is determined by the climatological conditions of the winter regime experiments are performed using either the perpetual november or january conditions with or without the prescribed sst anomalies warm sst anomalies in november result in a highly significant anomalous ridge downstream over the atlantic with a nearly equivalent barotropic structure in january the response is a statistically less significant trough the presence of the sst anomalies also causes a northward southward shift of the atlantic storm track in the november january cases a diagnostic analysis of the anomalous heat advection in the simulations reveals that in the january cases the surface heating is offset primarily by the strong horizontal cold advect

enso like interdecadal variability 1900 93 a number of recent studies have reported an enso like eof mode in the global sea surface temperature sst field whose time variability is marked by an abrupt change toward a warmer tropical eastern pacific and a colder extratropical central north pacific in 1976 77 the present study compares this pattern with the structure of the interannual variability associated with the enso cycle and documents its time history back to 1900 the analysis is primarily based on the leading eofs of the sst anomaly and anomaly deviation fields in various domains and the associated expansion coefficient or principal component time series which are used to construct global regression maps of sst sea level pressure slp and a number of related variables the use of anomaly deviations i e departures of local sst anomalies from the concurrent global mean sst anomaly reduces the influence of global mean sst trends upon the structure of the eofs and their expansion coefficient time series an important auxiliary time series used in this study is a southern oscillation index based on marine surface observations by means of several different analysis techniques the time variability of the leading eof of the global sst field is separated into two components one identified with the enso cycle related variability on the interannual timescale and the other a linearly independent residual comprising all the interdecadal variability in the record the two components exhibit rather similar spatial signatures in the global sst slp and wind stress fields the sst signature in the residual variability is less equatorially confined in the eastern pacific and it is relatively more prominent over the extratropical north pacific the corresponding slp signature is also stronger over the extratropical north pacific and its counterpart in the cold season 500 mb height field more closely resembles the pna pattern the amplitude time series of the enso like pattern in the residual variability reflects the above mentioned shift in 1976 77 as well as a number of other prominent features including a shift of opposite polarity during the 1940s

heat sources for glacial melt in a sub arctic fjord godthabsfjord in contact with the greenland ice sheet 1 recent warming of subpolar mode water off greenland has been suggested to accelerate the mass loss from tidal outlet glaciers of the greenland ice sheet we present a comprehensive analysis of water masses dynamics and interannual hydrographic variability in godthabsfjord a sill fjord in contact with tidal outlet glaciers on the west coast of greenland through seasonal observations we recognize an intermediate baroclinic circulation mode driven by tidal currents and an associated important local heat source for the fjord during summer this results in significant warming and freshening of the intermediate layer of the main fjord and the increase in heat content is equivalent to melting of 2 1 km3 of glacial ice this is comparable to 8 km3 glacial ice discharge estimated from the kangiata nun ta sermia calving front per year during winter the external heat source in the west greenland current enters the fjord as intermittent inflows of either cold 2 c dense water in pulses of 1 to 3 months duration four distinct circulation modes are observed in the fjord of which all can contribute to glacial ice melt an important aspect of the ice distribution in the fjord is that only a minor fraction is exported out of the fjord

sill processes related to deep water renewal in a fjord observations of the gravitational circulation over the sill at the entrance to puget sound indicate a fortnightly modulation of the two layer flow with a corresponding variation in stratification gravitational circulation and stratification reach a maximum during neap tides and a minimum during spring tides the modulation appears to be a function of the turbulence generation by tidal flow over the sill which varies as a function of tidal amplitude the enhanced gravitational circulation during neap tides augments the flux of dense water across the sill region and episodes of bottom water renewal in puget sound result intrusions of dense water in the main basin of the sound show a fortnightly periodicity with a phase lag appropriate for the propagation of an internal bore from the sill region commencing at the neap tide observations indicate that the intrusions take the form of gravity currents propagating at approximately 20 cm s 1 down the main basin the detailed dynamics of the turbulent mixing processes that modulate the onset of inflow were not resolved in this study but the integrated effect of tidal mixing on the low frequency circulation is clearly demonstrated

seasonal variability of the circulation system in a west greenland tidewater outlet glacier fjord godthabsfjord 64 n many tidewater outlet glacier fjords surround the coast of greenland and their dynamics and circulation are of great importance for understanding the heat transport toward glaciers from the ice sheet thus fjord circulation is a critical aspect for assessing the threat of global sea level rise due to melting of the ice sheet however very few observational studies describe the seasonal dynamics of fjord circulation here we present the first continuous current measurements april november from a deep mooring deployed in a west greenland tidewater outlet glacier fjord four distinct circulation phases are identified during the period and they are related to exchange processes with coastal waters tidal mixing and melt processes on the greenland ice sheet during early summer warm intermediate water is transported toward the glacier at an average velocity of about 7 cm s 1 in late summer the average velocity decreases to 3 cm s 1 during a period with significant subglacial freshwater discharges during this period a large variability in current velocities is also observed the associated average heat transport in an intermediate depth range corresponds to 568 gw in early summer and is reduced to 287 gw in late summer these heat fluxes are at the higher end of previously reported fluxes our measurements show that the intermediate heat transport varies over time and during summer provides a major contribution to the heat budget and thereby potentially to glacial melt we suggest that intermediate heat transport may play a similar important role in other fjords around greenland

acceleration of jakobshavn isbrae triggered by warm subsurface ocean waters observations over past decades show a sudden switch of jakobshavn isbrae a large outlet glacier feeding a deep ocean fjord on greenland s west coast from slow thickening to rapid thinning in 1997 this switch is associated with a doubling in glacier velocity hydrographic data show a concurrent sudden increase in subsurface ocean temperatures along the entire west coast of greenland suggesting that the changes in jakobshavn isbrae were triggered by the arrival of relatively warm water originating from the irminger sea observations over the past decades show a rapid acceleration of several outlet glaciers in greenland and antarctica1 one of the largest changes is a sudden switch of jakobshavn isbrae a large outlet glacier feeding a deep ocean fjord on greenland s west coast from slow thickening to rapid thinning2 in 1997 associated with a doubling in glacier velocity3 suggested explanations for the speed up of jakobshavn isbrae include increased lubrication of the ice bedrock interface as more meltwater has drained to the glacier bed during recent warmer summers4 and weakening and break up of the floating ice tongue that buttressed the glacier5 here we present hydrographic data that show a sudden increase in subsurface ocean temperature in 1997 along the entire west coast of greenland suggesting that the changes in jakobshavn isbrae were instead triggered by the arrival of relatively warm water originating from the irminger sea near iceland we trace these oceanic changes back to changes in the atmospheric circulation in the north atlantic region we conclude that the prediction of future rapid dynamic responses of other outlet glaciers to climate change will require an improved understanding of the effect of changes in regional ocean and atmosphere circulation on the delivery of warm subsurface waters to the periphery of the ice sheets

lithospheric controls on the formation of provinces hosting giant orogenic gold deposits ages of giant gold systems 500 t gold cluster within well defined periods of lithospheric growth at continental margins and it is the orogen scale processes during these mainly late archaean palaeoproterozoic and phanerozoic times that ultimately determine gold endowment of a province in an orogen a critical factor for giant orogenic gold provinces appears to be thickness of the subcontinental lithospheric mantle sclm beneath a province at the time of gold mineralisation as giant gold deposits are much more likely to develop in orogens with subducted oceanic or thin continental lithosphere a proxy for the latter is a short pre mineralisation crustal history such that thick sclm was not developed before gold deposition in constrast orogens with protracted pre mineralisation crustal histories are more likely to be characterised by a thick sclm that is difficult to delaminate and hence such provinces will normally be poorly endowed the nature of the lithosphere also influences the intrinsic gold concentrations of potential source rocks with back arc basalts transitional basalts and basanites enriched in gold relative to other rock sequences thus segments of orogens with thin lithosphere may enjoy the conjunction of giant scale fluid flux through gold enriched sequences although the nature of the lithosphere plays the crucial role in dictating which orogenic gold provinces will contain one or more giant deposits the precise siting of those giants depends on the critical conjunction of a number of province scale factors such features control plumbing systems traps and seals in tectonically and lithospherically suitable terranes within orogens

high selenium in the carboniferous coal measures of northumberland north east england the carboniferous lower and middle coal measures coals of the northumberland coalfield are anomalously rich in selenium se content up to 62 ppm compared to the averages for the common uk and worldwide coals as well as posing an environmental toxicity threat se is now regarded as an important resource for alloys photovoltaic products and nanotechnologies and high se coals in north east england offer an opportunity to assess the se means of occurrence origins transport mechanisms and enrichment in coals at least two generations of pyrite host high se in the sampled coal seams microbial formed disseminated pyrite both cubic and framboidal in habit and later cleat filling pyrite identified by petrographic observations laser ablation methods and sulphur isotope compositions there is a notable se enrichment of up to 250 ppm in later formed cleat filling pyrite trace element enrichment may have been sourced and influenced by seawater distribution during diagenesis and localised dykes and deformation may have acted as an enrichment mechanism for sampled seams in the region the high se coals in northumberland may provide a potential e tech element source and should be considered and carefully managed as coal mining and production are reduced in the area the study also highlights the nature of se enrichment in pyritic coals affected by cleat formation and multiple episodes of mineralisation important as critical element demand continues to increase worldwide

a global oceanic data assimilation system abstract a global oceanic four dimensional data assimilation system has been developed for use in initializing coupled ocean atmosphere general circulation models and many other applications the data assimilation system uses a high resolution global ocean model to extrapolate the information forward in time the data inserted into the model currently consists only of conventional sea surface temperature observations and vertical temperature profiles the data are inserted continuously into the model by updating the model s temperature solution every timestep this update is created using a statistical interpolation routine applied to all data in a 30 day window centered on the present timestep large scale features in the sea surface temperature analyses are consistent with those from independent analyses subsurface fields created from the assimilation are much more realistic than those produced without the insertion of data furthermore information contained in the assimilation field is shown to be re

large fluctuations in speed on greenland s jakobshavn isbrae glacier it is important to understand recent changes in the velocity of greenland glaciers because the mass balance of the greenland ice sheet is partly determined by the flow rates of these outlets jakobshavn isbrae is greenland s largest outlet glacier draining about 6 5 per cent of the ice sheet area and it has been surveyed repeatedly since 1991 ref 2 here we use remote sensing data to measure the velocity of jakobshavn isbrae between 1992 and 2003 we detect large variability of the velocity over time including a slowing down from 6 700 m yr 1 in 1985 to 5 700 m yr 1 in 1992 and a subsequent speeding up to 9 400 m yr 1 by 2000 and 12 600 m yr 1 in 2003 these changes are consistent with earlier evidence for thickening of the glacier in the early 1990s and rapid thinning thereafter our observations indicate that fast flowing glaciers can significantly alter ice discharge at sub decadal timescales with at least a potential to respond rapidly to a changing climate

on the persistence of decadal sst anomalies in the north atlantic abstract historical wintertime sea surface temperature sst data show that a sandwich pattern dominates on the decadal timescales in the north atlantic at least after the 1970s the authors investigated how such decadal sst anomalies can survive against local thermal feedback which acts to dampen them rapidly at the surface winter sst anomalies have a negligible projection with the subsequent summer anomalies while they show a significant projection with the sst anomalies in the next winter on the other hand observed summer temperature anomalies below the mixed layer tend to have the same sign as the previous winter sst anomalies although the magnitude of the former is roughly one third of the latter this suggests that a reemergence mechanism of sst anomalies associated with the seasonal cycle of the mixed layer depth mld which has been verified by alexander and deser helps maintain the decadal sst anomalies in order to examine this scenario a mixed layer model driven by daily atmospheric d

testing a dynamical model for mid latitude sea surface temperature anomalies abstract a slab model of the oceanic mixed layer is used to predict the statistical characteristics of the sea surface temperature anomalies that are forced by day to day changes in air sea fluxes in the presence of a mean current because of the short time scale of the atmospheric fields the model validity can be tested without quantitative information on the atmospheric forcing a procedure is developed for the case where the mean current is given it is applied to sea surface temperature sst anomaly data from the north pacific using ship drift data as estimates of the mean ocean currants at the 95 level of significance the model is consistent with the data over more than 85 of the investigated region the results indicate that the atmospheric forcing acts as a white noise forcing in regions of large currents advection effects are important at low frequencies however sst anomaly autospectra are equally well represented by a local model where advection is neglected the available meteorological

heat sources for glacial ice melt in a west greenland tidewater outlet glacier fjord the role of subglacial freshwater discharge the melting of tidewater outlet glaciers from the greenland ice sheet contributes significantly to global sea level rise accelerated mass loss is related to melt processes in front of calving glaciers yet the role of ocean heat transports is poorly understood here we present the first direct measurements from a subglacial plume in front of a calving tidewater outlet glacier surface salinity in the plume corresponded to a meltwater content of 7 which is indicative of significant entrainment of warm bottom water and according to plume model calculations significant ice melt energy balance of the area near the glacier showed that ice melt was mainly due to ocean heat transport and that direct plume associated melt was only important in periods with high meltwater discharge rates of 100 m3 s 1 ocean mixing outside of the plume area was thus the primary heat source for melting glacier ice

increasing meltwater discharge from the nuuk region of the greenland ice sheet and implications for mass balance 1960 2012 we assess the runoff and surface mass balance smb of the greenland ice sheet in the nuuk region southwest using output of two regional climate models rcms evaluated by observations the region encompasses six glaciers that drain into godthabsfjord rcm data 1960 2012 are resampled to a high spatial resolution to include the narrow relative to the native grid spacing glacier trunks in the ice mask comparing rcm gridded results with automatic weather station aws point measurements reveals that locally models can underestimate ablation and overestimate accumulation by up to tens of per cent however comparison with lake discharge indicates that modelled regional runoff totals are more accurate model results show that melt and runoff in the nuuk region have doubled over the past two decades regional smb attained negative values in recent high melt years taking into account frontal ablation of the marine terminating glaciers the region lost 10 20 km 3 w e a 1 in 2010 12 if 2010 melting prevails during the remainder of this century a low end estimate of sea level rise of 5 mm is expected by 2100 from this relatively small section 2 6 of the ice sheet alone

a mechanism for the recurrence of wintertime midlatitude sst anomalies abstract in the early 1970s namias and born speculated that ocean temperature anomalies created over the deep mixed layer in winter could be preserved in the summer thermocline and reappear at the surface in the following fall or winter this hypothesis is examined using upper ocean temperature observations and simulations with a mixed layer model the data were collected at six ocean weather stations in the north atlantic and north pacific concurrent and lead lag correlations are used to investigate temperature variations associated with the seasonal cycle in both the observations and the model simulations concurrent correlations between the surface and subsurface temperature anomalies in both the data and the model indicate that the penetration of temperature anomalies into the ocean is closely tied to the seasonal cycle in mixed layer depth high correlations extend to relatively deep shallow depths in winter summer lead lag correlations in both the data and the model at some of the stations

resolving bathymetry from airborne gravity along greenland fjords recent glacier mass loss in greenland has been attributed to encroaching warming waters but knowledge of fjord bathymetry is required to investigate this mechanism the bathymetry in many greenland fjords is unmapped and difficult to measure from 2010 to 2012 national aeronautics and space administration s operation icebridge collected a unique set of airborne gravity magnetic radar and lidar data along the major outlet glaciers and fjords in greenland we applied a consistent technique using the icebridge gravity data to create 90 bathymetric profiles along 54 greenland fjords we also used this technique to recover subice topography where warm or crevassed ice prevents the radar system from imaging the bed here we discuss our methodology basic assumptions and error analysis we present the new bathymetry data and discuss observations in six major regions of greenland covered by icebridge the gravity models provide a total of 1950 line kilometers of bathymetry 875 line kilometers of subice topography and 12 new grounding line depths

local coastal water masses control heat levels in a west greenland tidewater outlet glacier fjord fjords form the gateway between the open ocean and the greenland ice sheet gis and consequently play a crucial role for the stability of the ice sheet hydrographic observations especially with seasonal resolution from these fjords are limited making it difficult to assess linkages between the fjord coastal water masses and freshwater discharge from gis here we present a decade long monthly hydrographic time series from a southwest greenland fjord in direct contact with gis our observations reveal significant temporal and spatial water mass variations related to coastal glacial and atmospheric dynamics during winter the fjord circulation is dominated by seasonal dense coastal inflows and the timing of these inflows determines intermediate and deepwater temperatures during summer runoff from gis leads to a pronounced freshening of the fjord in general the fjord s seasonal circulation system damps the seasonal variation in temperature in the fjord this leads to a seasonal temperature range in the intermediate layer in the inner part of the fjord that is half the observed range at the fjord entrance changes in mean water temperatures in the intermediate layer seem predominantly linked to local coastal water masses where cold winter warm summer events decrease increase the mean water temperatures consequently these events play an important role in heat transport toward glacier termini

seasonal variability of submarine melt rate and circulation in an east greenland fjord 1 the circulation in a glacial fjord driven by a large tidewater glacier is investigated using a nonhydrostatic ocean general circulation model with a melt rate parameterization at the vertical glacier front the model configuration and water properties are based on data collected in sermilik fjord near helheim glacier a major greenland outlet glacier the approximately two layer stratification of the fjord s ambient waters causes the meltwater plume at the glacier front to drive a double cell circulation with two distinct outflows one at the free surface and one at the layers interface in summer the discharge of surface runoff at the base of the glacier subglacial discharge causes the circulation to be much more vigorous and associated with a larger melt rate than in winter the simulated double cell circulation is consistent in both seasons with observations from sermilik fjord seasonal differences are also present in the vertical structure of the melt rate which is maximum at the base of the glacier in summer and at the layers interface in winter simulated submarine melt rates are strongly sensitive to the amount of subglacial discharge to changes in water temperature and to the height of the layers they are also consistent with those inferred from simplified one dimensional models based on the theory of buoyant plumes our results also indicate that to correctly represent the dynamics of the meltwater plume care must be taken in the choice of viscosity and diffusivity values in the model

circulation and fjord shelf exchange during the ice covered period in young sound tyrolerfjord northeast greenland 74 n abstract fjords around greenland connect the greenland ice sheet to the ocean and their hydrography and circulation are determined by the interplay between atmospheric forcing runoff topography fjord shelf exchange tides waves and seasonal growth and melt of sea ice limited knowledge exists on circulation in high arctic fjords particularly those not impacted by tidewater glaciers and especially during winter when they are covered with sea ice and freshwater input is low here we present and analyze seasonal observations of circulation hydrography and cross sill exchange of the young sound tyrolerfjord system 74 n in northeast greenland distinct seasonal circulation phases are identified and related to polynya activity meltwater and inflow of coastal water masses renewal of basin water in the fjord is a relatively slow process that modifies the fjord water masses on a seasonal timescale by the end of winter there is two layer circulation with outflow in the upper 45 m and inflow extending down to approximately 150 m tidal analysis showed that tidal currents above the sill were almost barotropic and dominated by the m2 tidal constituent 0 26 m s 1 and that residual currents 0 02 m s 1 were relatively small during the ice covered period tidal pumping a tidally driven fjord shelf exchange mechanism drives a salt flux that is estimated to range between 145 kg s 1 and 603 kg s 1 extrapolation of these values over the ice covered period indicates that tidal pumping is likely a major source of dense water and driver of fjord circulation during the ice covered period

anomalous supply of bioessential molybdenum in mid proterozoic surface environments granites aged 1 9 ga to 1 5 ga exhibit molybdenite mineralization globally sandstones deposited during the mid proterozoic have a provenance dominated by 1 9 1 7 ga basement the mid proterozoic surface environment was consequently receiving detritus from the molybdenum rich granites thus there was a supply of molybdenum available in terrestrial or shallow marine environments at a time when molybdenum was required to support the evolution of multicellular life

externally forced fluctuations in ocean temperature at greenland glaciers in non summer months the factors that control the submarine melt rate at greenland s glaciers are uncertain and largely inferred from brief summer surveys in the fjords where glaciers terminate continuous records of water properties and velocity for the months september to may from two large greenland fjords reveal strong variability on 3 to 10 day timescales as a result of pulses of water that are propagated from the shelf ocean

a theory of interdecadal climate variability of the north pacific ocean atmosphere system abstract a linear coupled model for the atmosphere upper ocean system is proposed to highlight the mechanisms of decadal to interdecadal climate variability in the north pacific in this model wind stress anomalies over the north pacific are related to anomalies in the meridional temperature gradient of the upper ocean the latter depends upon air sea thermodynamical feedbacks and meridional heat transport by upper ocean currents slow adjustment of the oceanic gyre circulation to the change in wind stress is accomplished by the forced baroclinic oceanic rossby waves which carry out the meridional heat transport uncoupled ocean dynamic adjustment can produce a weak decadal to interdecadal peak in the power spectrum of the meridional transport under temporal white noise wind stress forcing with organized spatial structure coupled dynamics produce a basin scale interdecadal oscillatory mode this mode arises from the dynamic coupling and the memory of the system residing in the slow gyre circulation ad

gold in devono carboniferous red beds of northern britain authigenic gold occurs in devono carboniferous red beds in northern britain red beds exhibit concentrations of gold and pathfinder elements for gold mineralization including tellurium and mercury at redox boundaries detailed studies of samples from millport isle of cumbrae firth of clyde show particles of native gold up to 10 m size typically with less than 15 wt silver their context indicates that the gold was concentrated during diagenesis in rocks that had not experienced regional temperatures above 100 c these occurrences add to other evidence of a role for red beds in the genesis of gold mineralization

on the seasonal freshwater stratification in the proximity of fast flowing tidewater outlet glaciers in a sub arctic sill fjord 1 the greenland ice sheet releases large amounts of freshwater into the fjords around greenland and many fjords are in direct contact with the ice sheet through tidewater outlet glaciers here we present the first seasonal hydrographic observations from the inner part of a sub arctic fjord relatively close to and within 4 50 km of a fast flowing tidewater outlet glacier this region is characterized by a dense glacial and sea ice cover freshwater from runoff subglacial freshwater sgfw discharge glacial and sea ice melt are observed above 50 90 m depth during summer sgfw and subsurface glacial melt mixed with ambient water are observed as a layered structure in the temperature profiles below the low saline summer surface layer 1 c intermediate water mass is a significant subsurface heat source for ice melt we analyze the temperature and salinity profiles observed in late summer with a thermodynamic mixing model and determine the total freshwater content in the layer below the summer surface layer to be between 5 and 11 the total freshwater contribution in this layer from melted glacial ice was estimated to be 1 2 while the corresponding sgfw was estimated to be 3 10 the winter measurements in the subsurface halocline layer showed a total freshwater content of about 1 and no significant contribution from sgfw