fertilizing potential of volcanic ash in ocean surface water the fertilization potential of newly erupted and well preserved ash from the 2000 hekla eruption in iceland was measured for the first time by flow through experiments as previously shown 1 the north atlantic ocean including the subarctic seas surrounding iceland is the largest net sink of the world s oceans for atmospheric co 2 owing to biological drawdown during summer 2 almost complete consumption of phosphate in chlorophyll rich areas of the north atlantic ocean might limit primary production and 3 in the southern pacific ocean and parts of the equatorial pacific ocean iron might limit primary production we found through laboratory experiments that volcanic ash exposed to seawater initially releases large amounts of adsorbed phosphate 1 7 mmol g 21 h 21 iron 37 0 mmol g 21 h 21 silica 49 5 mmol g 21 h 21 and manganese 1 7 mmol g 21 h 21 dissolution of acid aerosols adsorbed to the surface of the ash caused the high initial release of major and trace elements because of the instantaneous dissolution of adsorbed components when newly erupted volcanic ash comes in contact with the ocean surface water macronutrients and bioactive trace metals are released fast enough to become available to support primary production

winter to summer oceanographic observations in the arctic ocean north of svalbard oceanographic observations from the eurasian basin north of svalbard collected between january and june 2015 from the n ice2015 drifting expedition are presented the unique winter observations are a key contribution to existing climatologies of the arctic ocean and show a 100m deep winter mixed layer likely due to high sea ice growth rates in local leads current observations for the upper 200m show mostly a barotropic flow enhanced over the shallow yermak plateau the two branches of inflowing atlantic water are partly captured confirming that the outer yermak branch follows the perimeter of the plateau and the inner svalbard branch the coast atlantic water observed to be warmer and shallower than in the climatology is found directly below the mixed layer down to 800m depth and is warmest along the slope while properties inside the basin are quite homogeneous from late may onwards the drift was continually close to the ice edge and a thinner surface mixed layer and shallower atlantic water coincided with significant sea ice melt being observed this article is protected by copyright all rights reserved

pollution and paradigms lessons from icelandic volcanism for continental flood basalt studies grattan j pollution and paradigms lessons from icelandic volcanism for continental flood basalt studies lithos 2005 79 pp 343 353

impact of eastern arctic shelf waters on the nansen basin intermediate layers the eurasian shelves supply water to the nansen basin intermediate layers in two ways as buoyancy driven plumes of dense winter water and as permanent inflow of the barents sea branch of atlantic water while the plumes are local and seasonal phenomena the barents sea flow is part of the large scale circulation both interact with atlantic water which enters the arctic ocean through fram strait and moves as a subsurface boundary current eastward along the continental slope during the polarstern cruise ark ix 4 in summer 1993 the fram strait branch was observed as a narrow core within tens of kilometers of the barents sea shelf edge here several patches of cold low salinity water spread across the slope down to about 500 m depth their origin is assumed to be the northern barents sea they mix with the warm saline fram strait branch water fsbw so that the core properties of the latter become modified downstream in the eastern nansen basin the fram strait branch is displaced toward the inner basin by inflow of the barents sea branch of atlantic water bsbw this inflow appears as a broad 200 km wedge extending from 200 to 1300 m depth bsbw is colder and less saline than water of the fram strait branch and it is less dense and less stratified than the ambient water both branches appear to undergo vigorous mixing while spreading eastward so that any eastward continuation of the boundary flow transports about 50 bsbw and 50 fsbw above 600 m and about 80 bsbw and 20 fsbw below that level toward the canadian basin according to available observations the barents and kara seas are the only source areas for shelf waters ventilating the nansen basin below the halocline and these waters constitute a freshwater input rather than a salt input winter shelf water from the laptev sea cannot contribute to layers deeper than the upper halocline

seasonal cycle of mesoscale instability of the west spitsbergen current abstractthe west spitsbergen current wsc is a topographically steered boundary current that transports warm atlantic water northward in fram strait the 16 yr 1997 2012 current and temperature salinity measurements from moorings in the wsc at 78 50 n reveal the dynamics of mesoscale variability in the wsc and the central fram strait a strong seasonality of the fluctuations and the proposed driving mechanisms is described in winter water is advected in the wsc that has been subjected to strong atmospheric cooling in the nordic seas and as a result the stratification in the top 250 m is weak the current is also stronger than in summer and has a greater vertical shear this results in an e folding growth period for baroclinic instabilities of about half a day in winter indicating that the current has the ability to rapidly grow unstable and form eddies in summer the wsc is significantly less unstable with an e folding growth period of 2 days observations of the eddy kinetic energy eke show a p

posteruptive impacts of pyroclastic deposits from basaltic andesite stratovolcanoes on surface water composition volcanic ash deposition following explosive eruptions can pose significant hazards for water quality human health agriculture and infrastructure functionality many studies have examined how fresh ash deposition may lower the ph of and introduce a range of potentially toxic elements into exposed surface waters however no study has yet determined the effects on water composition as a result of mechanical pyroclast disaggregation and production of new fresh particle surfaces and increasingly fine grained particles such disaggregation could result from natural posteruptive processes such as debris avalanches lahars or fluvial aeolian transport and human activities such as cleanup efforts or mining of pyroclastic deposits the posteruption time scales of pyroclast disaggregation may vary from months in moist tropical or temperate environments to years or decades in arid settings here we show for the first time in experimental studies that mechanical milling of pyroclasts will introduce a range of elements into exposed waters including al which can be toxic at elevated levels and na which increases the electrical conductivity of solutions the ph of leaching solutions also increases by several log units such dramatic changes on the experimental scale may have implications for surface water composition in posteruptive settings necessitating longer term risk assessments for ecosystem health and consideration of the role of pyroclastic deposits in element cycling in volcanically active regions

rapid releases of metal salts and nutrients following the deposition of volcanic ash into aqueous environments deposition of volcanic ash into aqueous environments leads to dissolution of adsorbed metal salts and aerosols increasing the bioavailability of key nutrients volcanogenic fertilization events could increase marine primary productivity leading to a drawdown of atmospheric co2 here we conduct flow through experiments on unhydrated volcanic ash samples from a variety of locations and sources measuring the concentrations and fluxes of elements into de ionized water and two contrasting ocean surface waters comparisons of element fluxes show that dissolution of adsorbed surface salts and aerosols dominates over glass dissolution even in sustained low ph conditions these surface ash leachates appear unstable decaying in situ even if kept unhydrated volcanic ash from recent eruptions is shown to have a large fertilization potential in both fresh and saline water fluorine concentrations are integral to bulk dissolution rates and samples with high f concentrations display elevated fluxes of some nutrients particularly fe si and p bio limiting micronutrients are released in large quantities suggesting that subsequent biological growth will be limited by macronutrient availability importantly acidification of surface waters and high fluxes of toxic elements highlights the potential of volcanic ash leachates to poison aqueous environments in particular large ph changes can cause undersaturation of caco3 polymorphs damaging populations of calcifying organisms deposition of volcanic ash can both fertilize and or poison aqueous environments causing significant changes to surface water chemistry and biogeochemical cycles

diurnal tides near the yermak plateau recent current measurements obtained from drifting platforms over the yermak plateau in the eastern arctic ocean confirm that the plateau is a region of greatly enhanced diurnal tidal currents modulation of the diurnal currents is clearly related to the plateau topography as has been previously proposed we show however that temporal variability due to spring neap modulation must also be considered in interpreting records from drifting platforms we review simple models of tidal current amplification in this region and find that the previous assumption of near resonant barotropic shelf waves propagating around the plateau s entire perimeter is inconsistent with the true topography instead we propose that the diurnal variability is due to topographic shelf waves at the k1 and o1 tidal frequencies that are generated at points on the plateau s perimeter where the waves group velocities are near zero observed cross slope variations in ellipticity orientation and magnitude of tidal oscillations are consistent with the presence of topographic waves generated in this manner the topographic enhancement of the diurnal tide near the yermak plateau has important consequences for the sea ice cover hydrography and general circulation of this region for example the stress divergence applied by the tidal currents at the ice base greatly exceeds the typical divergence of the surface wind stress and tides may therefore be important to local ice deformation the strong cross slope tidal currents also appear to be responsible for the production of high frequency internal wave packets which are associated with energetic diapycnal mixing in the pycnocline we also consider the possibility that tidal rectification is responsible for a mean current transporting atlantic water clockwise around the plateau

spatial distribution of dissolved constituents in icelandic river waters summary in this study we map the spatial distribution of selected dissolved constituents in icelandic river waters using gis methods to study and interpret the connection between river chemistry bedrock hydrology vegetation and aquatic ecology five parameters were selected alkalinity sio2 mo f and the dissolved inorganic nitrogen and dissolved inorganic phosphorus mole ratio din dip the highest concentrations were found in rivers draining young rocks within the volcanic rift zone and especially those draining active central volcanoes however several catchments on the margins of the rift zone also had high values for these parameters due to geothermal influence or wetlands within their catchment area the din dip mole ratio was higher than 16 in rivers draining old rocks but lowest in rivers within the volcanic rift zone thus primary production in the rivers is limited by fixed dissolved nitrogen within the rift zone but dissolved phosphorus in the old tertiary catchments nitrogen fixation within the rift zone can be enhanced by high dissolved molybdenum concentrations in the vicinity of volcanoes the river catchments in this study were subdivided into several hydrological categories importantly the variation in the hydrology of the catchments cannot alone explain the variation in dissolved constituents the presence or absence of central volcanoes young reactive rocks geothermal systems and wetlands is important for the chemistry of the river waters we used too many categories within several of the river catchments to be able to determine a statistically significant connection between the chemistry of the river waters and the hydrological categories more data are needed from rivers draining one single hydrological category the spatial dissolved constituent distribution clearly revealed the difference between the two extremes the young rocks of the volcanic rift zone and the old tertiary terrain

trace element degassing and enrichment in the eruptive plume of the 2000 eruption of hekla volcano iceland during its last eruption in february 2000 hekla volcano iceland emitted a sub plinian plume that was condensed and scavenged down to the ground by heavy snowstorms offering the unique opportunity to study the chemistry of the gaseous plume released during highly explosive eruptions in this paper we present results on trace element and minor volatile species sulfates chlorides and fluorides concentrations in snow samples collected shortly after the beginning of the eruption the goal of this study is to better constrain the degassing and mobility of trace elements in gaseous emissions trace element volatility at hekla is quantified by means of enrichment factors ef relative to be well known volatile trace elements e g transition metals heavy metals and metalloids are considerably enriched in the volcanic plume of hekla their abundances are governed by the primary magmatic degassing of sulfate and or halide compounds which are gaseous at magmatic temperature their volatility is however slightly lower than in basaltic systems most likely because of the lower magma temperature and higher magma viscosity at hekla more surprisingly refractory elements e g ree th ba and y are also significantly enriched in the eruptive plume of hekla where their apparent volatility is two orders of magnitude higher than in mafic systems in addition ree patterns normalized to the hekla 2000 lava composition show a significant enrichment of hree over lree suggesting the presence of ree fluorides in the volcanic plume such enrichments in the most refractory elements and ree fractionation are difficult to reconcile with primary degassing processes since ree fluorides are not gaseous at magma temperature ree enrichments at hekla could be attributed to incongruent dissolution of tephra grains at low temperature by f rich volcanic gases and aerosols within the eruptive plume this view is supported by both leaching experiments performed on hekla tephra and thermodynamic considerations on ree mobility in hydrothermal fluids and modeling of glass dissolution in f rich aqueous solutions tephra dissolution may also explain the observed enrichments in other refractory elements e g th y and ba and could contribute to the degassing mass balance of some volatile trace elements provided they are mobile in f rich fluids it thus appears that both primary magmatic degassing and secondary tephra dissolution processes govern the chemistry of eruptive plumes released during explosive eruptions

chemical weathering of basalts southwest iceland effect of rock crystallinity and secondary minerals on chemical fluxes to the ocean river ground and peat water from a basaltic catchment area laxa in kjos southwest iceland were sampled and analyzed for major element concentrations to define the effect of glassy versus crystalline basalt the formation of secondary minerals and runoff on fluxes of dissolved elements to the ocean the proportions of the dissolved solids in the water samples derived from precipitation air and rock weathering were estimated the amounts of na mg ca k and s originating from precipitation were calculated from the respective solute cl marine ratios and the estimated aqueous cl originated from precipitation which was calculated using measured b content of the waters and b cl molal marine and rock ratios the rock contribution from weathering ranged from 22 to 46 percent of the total dissolved solids of the waters iron and al showed low mobility compared to na this was primarily due to consumption of these elements by ferrihydroxides allophane imogolite and clay minerals also si and to a lesser degree ca show apparent slightly lower mobility than na these results are in good agreement with these phases being dominant in the soils of the study area wada and others 1992 and the main secondary minerals of basaltic glass in iceland crovisier and others 1992 reaction progress calculations support these findings according to a model interaction of basaltic glass and meteoric water al fe and si are consumed by amorphous fe and al hydroxides and imogolite and allophane at low reaction progress with increasing reaction progress ca fe mg smectite became the primary secondary minerals limiting the mobility of ca fe mg si and al these findings suggest that the weathering in the laxa in the kjos catchment area has evolved into the beginning of the smectite weathering stage and that it is dominated by a relatively low reaction progress and a high water to rock ratio in the present study the effect of runoff and rock crystallinity was quantified for dissolved elemental fluxes temperature lithology other than rock crystallinity and rock age were similar in all of the catchment areas in this study silica ca f s al k mg and b had a very similar dependence on runoff on the other hand na fluxes were found to be less dependent on runoff and fe fluxes were found to be independent of runoff basaltic glass dissolves faster than fully crystallized basaltic rocks gislason and eugster 1987a therefore increased glass content of the primary rocks is thought to increase the leaching and elemental fluxes at constant runoff however because some of the solutes particularly al and fe were highly influenced or even controlled by the formation of secondary minerals this increasing dissolution with increasing glass content was hidden on the other hand basaltic glass was observed to enhance the fluxes of more mobile elements like na si ca f and s by a factor of 2 to 5 at a constant runoff of 200 cm yr constant vegetative cover and 0 to 100 percent glass content of the rocks the k and mg fluxes were found to be independent of rock crystallinity however runoff alone cannot explain the fluxes of these elements and it seems that vegetative cover and seasonal variations in biomass activities influence the k and mg fluxes

the effect of volcanic eruptions on the chemistry of surface waters the 1991 and 2000 eruptions of mt hekla iceland abstract the mt hekla eruptions in 1991 and 2000 have provided a unique opportunity to study the local environmental effects of high latitude volcanic eruptions in the middle of winter both eruptions started around sunset at sub zero temperatures in order to define better these effects we studied the chemistry of surface waters in the vicinity of the volcano additionally we describe and predict the environmental consequences of these volcanic eruptions on the chemistry of surface waters on land and in the ocean several dissolved elements in the polluted snow melt from the 2000 eruption cl f al fe mn as cd pb zn and u exceeded the limits for water intended for human consumption the volcanic ash the primary minerals and secondary mineral phases that commonly form in the weathering environment of iceland were undersaturated in the polluted snow melts with the exception of fluorite barite goethite and amorphous feooh these minerals can constrain the maximum initial concentration of the respective dissolved constituents in the meltwaters it took few days after the first rainfall on the volcanic ash to flush out the readily soluble constituents in the vicinity of the headwaters of the ytri ranga river the polluted river waters were oversaturated with respect to several secondary minerals resulting in precipitation of amorphous al hydroxide and feooh and further scavenging of some trace elements on the al and fe surfaces dissolved al and f were the main contaminants in the ytri ranga river water previous studies have shown that combined al f toxicity is directly related to the predominance of specific al f species in solution model calculations for mixing of a hekla type volcanic cloud with 4 surface water end members shows al f species to be most important in rain and dilute river waters this makes al and f phyto available but diminishes the concentration of the al 3 species the most toxic al species mixing with high alkalinity river waters or seawater results in the domination of non toxic al oh 4 species at dilutions greater than 800 thus hindering al toxicity and bioavailability this study indicates that h 2 so 4 contamination from volcanic eruptions is time and place dependent volcanic eruptions that take place during winter at high latitudes result in relatively high global sulfur contamination and relatively low local sulfur contamination due to the low oxidation rate of so 2 into h 2 so 4 because of the low solar radiation

seasonal release of anoxic geothermal meltwater from the katla volcanic system at solheimajokull iceland understanding patterns of geothermal and volcanic activity at many of iceland s most active volcanic systems is hampered by thick overlying ice which prevents direct observation and complicates interpretation of geophysical signals katla is a prime example being a large and restless volcanic system covered by the 740 m thick m rdalsjokull ice cap whose eruptions have triggered some of the most powerful known meltwater floods in historical times to shed new light on geothermal and subglacial hydrological processes at katla we have determined the sulphate isotopic composition of a series of glacial meltwater samples discharged from solheimajokull a valley glacier of m rdalsjokull between 2009 and 2012 dual isotopic analysis of 34s and 18o in dissolved sulphate allows identification of source mixing processes and chemical evolution during subglacial meltwater transport strikingly meltwater 18oso4 signatures indicate redox conditions at the glacier bed which are inverse to those normally encountered at arctic and alpine glaciers discharge of reduced anoxic meltwater in summer rather than winter points towards seasonal release of geothermally derived volatile gases we attribute this to headward expansion of the channelized subglacial drainage system during the summer melt season accessing key areas of geothermal activity within the katla caldera volatile release may be further enhanced by unloading of overburden pressure due to snowpack melting in the summer season in winter restriction of subglacial channels to lower elevations effectively seals geothermal fluids and dissolved gases beneath the ice cap with only sporadic release permitted by periodic increases in subglacial water pressure when the subglacial drainage configuration permits access to key geothermal areas sulphate isotopic signatures thereby form sensitive indicators of geothermal activity occurring deep beneath the m rdalsjokull ice cap

a diverse ecosystem response to volcanic aerosols unexpectedly high aluminium concentrations beside fluoride and essential elements are released from metal salts adsorbed to volcanic ash through simulation of the mixing of pristine volcanic ash leachate with fresh water and seawater using phreeqc we found an increased potential toxicity in fresh waters through the combination of high aluminium and fluoride concentrations owing to the mixing of acid ash leachate with fresh water aluminofluoride complexes alfx 3 x persist in aqueous systems with low turnover rates and could be toxic to both plants and animals in contrast due to the well buffered and relatively high ph in seawater the speciation of the ash leachate seawater mixture shows that complexes of fluoride and aluminium i e alfx 3 x will not dominate in a well mixed marine system instead al oh x 3 x species will occur at greatest concentration consequently compared with fresh water environments the mixing of ash leachate with seawater indicates reduced toxic effects due to decreased formation of alfx 3 x complexes and the low solubility of al hydroxides in addition the deposition of volcanic aerosols may enhance biological activity in the marine environment by providing micronutrients as some oceanic phytoplankton species tolerates extreme concentrations of fluoride f

weather radar observations of the hekla 2000 eruption cloud iceland the hekla eruption cloud on 26 27 february 2000 was the first volcanic cloud to be continuously and completely monitored advecting above iceland using the c band weather radar near the keflavik international airport real time radar observations of the onset advection and waning of the eruption cloud were studied using time series of ppi plan position indicator radar images including vmi normal echotop and cappi level 2 displays the reflectivity of the entire volcanic cloud ranges from 0 to 60 dbz the eruption column above the vent is essentially characterised by vmi normal and cappi level 2 values 30 dbz due to the dominant influence of lapilli and ash tephra on the overall reflected signal the cloud generated by the column was advected downwind to the north northeast it is characterised by values between 0 and 30 dbz and the persistence of these reflections likely result from continuing water condensation and freezing on ash particles echotop radar images of the eruption onset document a rapid ascent of the plume head with a mean velocity of 30 to 50 m s 1 before it reached an altitude of 11 12 km the evolution of the reflected cloud was studied from the area change in pixels of its highly reflected portions 30 dbz and tied to recorded volcanic tremor amplitudes the synchronous initial variation of both radar and seismic signals documents the abrupt increase in tephra emission and magma discharge rate from 18 20 to 19 00 utc on 26 february from 19 00 the 45 dbz and 30 45 dbz portions of the reflected cloud decrease and disappear at about 7 and 10 5 h respectively after the eruption began indicating the end of the decaying explosive phase the advection and extent of the reflected eruption cloud were compared with eyewitness accounts of tephra fall onset and the measured mass of tephra deposited on the ground during the first 12 h differences in the deposit map and volcanic cloud radar map are due to the fact that the greater part of the deposit originates by fallout off the column margins and from the base of the cloud followed by advection of falling particle in lower level winds

analysis of the warmest arctic winter 2015 2016 december through february 2015 2016 defines the warmest winter season over the arctic in the observational record positive 2 m temperature anomalies were focused over regions of reduced sea ice cover in the kara and barents seas and southwestern alaska a third region is found over the ice covered central arctic ocean the period is marked by a strong synoptic pattern which produced melting temperatures in close proximity to the north pole in late december and anomalous high pressure near the taymyr peninsula atmospheric teleconnections from the atlantic contributed to warming over eurasian high latitude land surfaces and el nino related teleconnections explain warming over southwestern alaska and british columbia while warm anomalies over the central arctic are associated with physical processes including the presence of enhanced atmospheric water vapor and an increased downwelling longwave radiative flux preconditioning of sea ice conditions by warm temperatures affected the ensuing spring extent

trace element behaviour in seawater during etna s pyroclastic activity in 2001 concurrent effects of nutrients and formation of alteration minerals abstract the eruption of etna in sicily on 13 july 2001 marked the most intense activity of the volcano in the last 300 years the eruption occurred while the oceanographic cruise ansic 01 was being conducted to the east of sicily presenting a unique opportunity for the investigation of the chemical effects on the marine system during a period of significant 1 g m 2 ash deposition comparison of trace element data with measured concentrations from the oceanographic cruise juvenile 99 carried out two years before indicates large enrichments of v cr mn fe co cu and pb we attribute this behaviour to leaching of freshly erupted volcanic ash according to trace element concentrations measured in suspended particulate matter spm the exception is pb which is likely to be influenced by another possibly anthropogenic source trace element behaviour in the water column and during leaching experiments suggests that trace element distributions are driven by the occurrence of alteration minerals on glass surfaces given that the main trace element source in seawater appears to come from the soluble ash fraction trace element solubility is likely to be increased by organic complexation which accelerates the alteration of ash particles organic substances suitable for complex trace elements are probably formed during the lysis of phytoplankton cells produced during an increase in marine primary productivity associated with the volcanic fertilisation of surface waters

new hydrographic measurements of the upper arctic western eurasian basin in 2017 reveal fresher mixed layer and shallower warm layer than 2005 2012 climatology in 2017 ice atmosphere ocean observing system autonomous drifting platforms provided extensive physical and biogeochemical data in the upper 350 m of the western eurasian basin through their 8 month drift across the amundsen basin the gakkel ridge the nansen basin and western fram strait comparison with woa13 climatology indicates a fresher surface layer and shallower warm layer in 2017 than in 2005 2012 the ice atmosphere ocean observing system 2017 data feature two halocline eddies in the amundsen basin and two atlantic water aw mesoscale structures in the nansen basin analysis of the global 1 12 mercator ocean operational system suggests that the halocline eddies resulted from instabilities in the frontal zone between fresher makarov waters and saltier eurasian waters this frontal region appears to have shifted further southeast in 2017 near 88 n 10 e compared to 2005 2012 the operational system depicts the large aw structure in the nansen basin 140 km crossed as far as 83 7 n 34 5 e as an aw meander from the arctic circumpolar boundary current which turned into an anticyclonic eddy about a month after the platforms drifted away the aw structure at 82 8 n 3 w northwest of the yermak plateau corresponds to an aw recirculating branch detaching from the yermak plateau slope back toward fram strait

dissolution of primary basaltic minerals in natural waters saturation state and kinetics abstract the state of saturation of olivine orthopyroxene and plagioclase of variable composition has been assessed in various types of natural waters in iceland including river waters groundwater and geothermal waters with temperatures up to 250 c the stability of olivine and orthopyroxene decreases with increasing mg content similarly the stability of plagioclase decreases with increasing anorthite content the river waters which are representative of the weathering environment are always undersaturated with both olivine and orthopyroxene the degree of undersaturation being dominated by the water ph all river waters tend to dissolve olivine of the composition encountered in basalts according to the linear rate law and orthopyroxene when the ph is 200 c are undersaturated with olivine orthopyroxene and plagioclase the first two particularly when fe rich and sufficient to cause olivine to dissolve according to the linear rate law at intermediate temperatures 50 150 c the geothermal waters are close to equilibrium with these minerals except for mg rich olivine it seems likely that dissolution of glass from basalt which is very reactive will favor stability of the igneous minerals

major impact of volcanic gases on the chemical composition of precipitation in iceland during the 2014 2015 holuhraun eruption the holuhraun eruption in 2014 15 was the largest in iceland for more than 200 years it resulted in emissions of large quantities of volcanic gases into the atmosphere 11 mt so2 0 1 mt hcl and 0 05 mt hf during the eruption the volcanic gases had major effects on f so4 and to a lesser extent cl concentrations in precipitation throughout iceland effects not observed in recent decades the concentrations of f cl and so4 n 705 reached values of 444 m 12 270 m and 17 324 m during the eruption and were on average 20 times higher for f and so4 and much lower for cl compared to pre eruption times the concentrations of major cations si na k ca mg al and fe n 151 in the precipitation were taken as having originated from seawater spray and dissolution of rock dust and aerosol based on the mixing model developed here it is demonstrated that the source of the enrichment of f and so4 was indeed the volcanic gas emissions with 60 100 mol of so4 and f in the precipitation originated from volcanic gas whereas the cl originated mostly from seawater spray making the volcanic gas input of cl relatively less important than for f and so4 the results showed that large volcanic eruptions can have major effects on atmospheric chemistry and impact the composition of precipitation

greater role for atlantic inflows on sea ice loss in the eurasian basin of the arctic ocean arctic sea ice loss is a leading indicator of climate change and can be attributed in large part to atmospheric forcing here we show that recent ice reductions weakening of the halocline and shoaling of the intermediate depth atlantic water layer in the eastern eurasian basin have increased winter ventilation in the ocean interior making this region structurally similar to that of the western eurasian basin the associated enhanced release of oceanic heat has reduced winter sea ice formation at a rate now comparable to losses from atmospheric thermodynamic forcing thus explaining the recent reduction in sea ice cover in the eastern eurasian basin this encroaching atlantification of the eurasian basin represents an essential step toward a new arctic climate state with a substantially greater role for atlantic inflows

carbon dioxide degassing from the albani hills volcanic region central italy the albani hills are affected by strong co2 degassing processes the amount of co2 which rises from the depths and subsequently dissolves into shallow groundwater has been estimated to be more than 4 2 109 mol year 1 most of the gas is released in localised anomalous spots lavinio solforata and ciampino albano nemi areas generated by fluid leakage processes from buried pressurized reservoirs hosted by structural highs of the calcareous siliceous marly basement the groundwater circulating in the anomalous areas becomes co2 oversaturated generating observable gas manifestations whose composition is mainly controlled by gas liquid separation processes a gas flow rate of 6 1 108 mol year 1 has been measured from the two larger manifestations using the accumulation chamber technique the presence at shallow level of co2 oversaturated groundwater can explain several episodes of sudden release of gas which was documented by historical chronicles from roman times until now

volcanic winter and accelerated glaciation following the toba super eruption the eruption of toba in sumatra 73 500 years ago was the largest known explosive volcanic event in the late quaternary1 it could have lofted about 1015 g each of fine ash and sulphur gases to heights of 27 37 km creating dense stratospheric dust and aerosol clouds here we present model calculations that investigate the possible climatic effects of the volcanic cloud the increase in atmospheric opacity might have produced a volcanic winter 2 a brief pronounced regional and perhaps hemispheric cooling caused by the volcanic dust followed by a few years with maximum estimated annual hemispheric surface temperature decreases of 3 5 c the eruption occurred during the stage 5a 4 transition of the oxygen isotope record a time of rapid ice growth and falling sea level3 we suggest that the toba eruption may have greatly accelerated the shift to glacial conditions that was already underway by inducing perennial snow cover and increased sea ice extent at sensitive northern latitudes as the onset of climate change may have helped to trigger the eruption itself4 we propose that the toba event may exemplify a more general climate volcano feedback mechanism

comparison of carbonate and shale source rocks abstract as with shales the source potential of carbonate rocks depends primarily upon the organic facies rather than the mineral matrix where the depositional and early diagenetic environment is highly oxygenated the total organic carbon toc is low with a negligible generative capacity for hydrocarbons despite a relatively high hydrocarbon toc ratio in the immature state an anoxic depositional and early diagenetic environment can result in the deposition of organic rich fine grained carbonate rocks that are excellent potential source rocks excellent oil prone source rocks whether with carbonate or clay mineral matrices have many characteristics in common both form in anoxic environments are generally laminated and heterogeneous have moderate to high toc and contain high quality organic matter om gas prone organic facies are rare in carbonate rocks because such facies are usually dominated by terrestrial organic matter deposited in a dominantly clay matrix most carbonate rocks contain nongenerative organic facies as do most siliceous rocks oxygen rich depositional environments for carbonates are found from sea level reefs to the ocean depths globigerina ooze despite the basic commonality between organic rich oil prone carbonate and shale source rocks some significant differences exist oils derived from carbonate rocks are often richer in cyclic hydrocarbons and sulfur compounds than oils derived from shales due to the dearth of terrestrial plant waxes in the om and less iron in the pore water in addition the generally earlier decrease of porosity and permeability and the greater contrast between the physical properties of the om and the rock matrix in carbonate source rocks often result in different primary migration characteristics end of article last page 494

atlantic waters inflow north of svalbard insights from iaoos observations and mercator ocean global operational system during n ice2015 as part of the n ice2015 campaign iaoos ice atmosphere ocean observing system platforms gathered intensive winter data at the entrance of atlantic water aw inflow to the arctic ocean north of svalbard these data are used to examine the performance of the 1 12 resolution mercator ocean global operational ice ocean model in the marginal ice zone north of svalbard modeled sea ice extent ocean heat fluxes mixed layer depths and aw mass characteristics are in good agreement with observations model outputs are then used to put the observations in a larger spatial and temporal context model outputs show that aw pathways over and around the yermak plateau differ in winter from summer in winter the large aw volume transport of the west spitsbergen current wsc 4 sv proceeds to the north east through 3 branches the svalbard branch 0 5 sv along the northern shelf break of svalbard the yermak branch 1 1 sv along the western slope of the yermak plateau and the yermak pass branch 2 0 sv through a pass in the yermak plateau at 80 8 n in summer the aw transport in the wsc is smaller 2 sv and there is no transport through the yermak pass although only eddy permitting in the area the model suggests an important mesoscale activity throughout the aw flow the large differences in ice extent between winters 2015 and 2016 follow very distinct atmospheric and oceanic conditions in the preceding summer and autumn seasons convection induced upward heat fluxes maintained the area free of ice in winter 2016 this article is protected by copyright all rights reserved

the hekla eruption 1980 1981 the sixteenth eruption of hekla since 1104 began on august 17th 1980 after the shortest repose period on record only ten years the eruption started with a plinian phase and simultaneously lava issued at high rate from a fissure that runs along the hekla volcanic ridge the production rate declined rapidly after the first day and the eruption stopped on august 20th a total of 120 million m3 of lava and about 60 million m3 of airborne tephra were produced during this phase of the activity in the following seven months steam emissions were observed on the volcano activity was renewed on april 9th 1981 and during the following week additional 30 million m3 of lava flowed from a summit crater and crater rows on the north slope

volcanic ash leachate compositions and assessment of health and agricultural hazards from 2012 hydrothermal eruptions tongariro new zealand abstract after almost 80 years of quiescence the upper te maari vent on mt tongariro erupted suddenly at 2352 h nz time on 6 august 2012 the short lived hydrothermal eruption distributed a fine ash of minor volume 5 10 5 m 3 over 200 km from source the threat of further eruptions prompted an investigation of the possible health and agricultural impacts of any future eruptions from this volcano particularly since the most recent large scale ash falls in new zealand in 1995 1996 had generated significant agricultural problems including livestock deaths deposited ash was sampled between 5 and 200 km from the volcano as soon as possible after the eruption two sub lobes of ash were identified from different vent areas and displayed subtly different leaching properties the first was an initial small lobe directed nne likely formed from drifting low level clouds associated with the initial lateral explosive blast and surges the main fall lobe directed eastward was sourced from a short lived vertical plume that rose up to c 8 km ash from the initial fall lobe had higher concentrations of f and al in single step leaches as well as in the totals of three sequential extractions further the initial lobe showed a higher proportion of soluble f and al extracted in the first leach compared to totals a linear relationship between concentrations of al and f in single leaches from the 6 august eruption was highly significant pearson correlation coefficient r 0 987 for 1 20 leaching ratios and r 0 971 for 1 100 suggesting the presence of soluble alumino fluoride complexes alf x 3 x an even more significant 1 1 ratio is displayed for the largest concentration leached ions of ca and so 4 which correspond to the presence of crystalline gypsum throughout the newly excavated hydrothermal system although no fresh magma was erupted in this event a shallow intrusion prior to the hydrothermal explosion apparently provided significant contents of volcanic gas that was dissolved within the hydrothermal fluids and adhering to ejected particles this and the ubiquitous presence of gypsum dominated the soluble components of these ash deposits leading to a complex leaching profile the leaching study carried out here showed that agricultural and human health hazard assessment particularly of f and s is not straightforward particularly because f solubility may be complex and not well characterised by simple leaching studies in the case of s which is agriculturally important saturation effects are apparent using normal leaching protocols and also imply a need for modification of standard methods

a simple shelf circulation model intrusion of atlantic water on the west spitsbergen shelf abstractbarotropic flow along depth contours is found in accordance with standard geostrophic theory a numerical model is developed that studies the deviation from such a flow the model gives a good approximation of the dynamical processes on the west spitsbergen shelf wss and shows that the west spitsbergen current wsc the main gateway of atlantic water aw toward the arctic connects more easily to the isfjorden trough than anywhere else along the shelf the circulation of aw in the troughs along the wss is here named the spitsbergen trough current stc from hydrographical and ocean current observations it is evident that the stc is primarily barotropic and driven by the sea surface height a connection between the along coast wind stress and the stc is established and it is demonstrated how the increased occurrence of winter cyclones in fram strait during january february accelerates and widens the wsc ultimately this results in a strengthened stc and dominance of aw on the wss the stc re

long term mobilisation of chemical elements in tephra rich peat ne iceland this paper presents geochemical profiles of a tephra bearing minerotrophic peat column from ne iceland obtained using various elemental analyses of the solid phase and the pore water the influence of tephra grain size thickness and composition of each tephra on the peat geochemistry was investigated interpretations are supported by a statistical approach in particular by autocorrelation and by microscopy observations minerotrophic peat geochemistry may be strongly dependent upon post depositional mobilization and possible leaching of elements as demonstrated by fe and trace metal concentration profiles chemical elements and more specifically potentially harmful metals can be slowly leached out of volcanic falls during their weathering and re accumulate downwards it is emphasised that a tephra deposit can act as an active geochemical barrier blocking downward elemental movements and leading to the formation of enriched layers in this study the formation of poorly amorphous fe phases above the hekla 3 tephra is shown these poorly crystalline fe phases scavenged ni

recent volatile evolution in the magmatic system of hekla volcano iceland estimates of the volatile budgets for volcanic eruptions are often based on volatile concentrations measured in melt inclusions mis versus groundmass glass here we present new measurements and estimates of pre eruptive volatile concentrations in magma from the hekla volcano in iceland based on mis in recent basalts and basaltic icelandites from the 2000 eruption the last eruption at hekla occurred from 26 february to 8 march 2000 it began with a short sub plinian phase followed by lava effusion that produced 0 17 km 3 of basaltic icelandite volatile s cl f and h2o and major element concentrations were measured in mis trapped in olivine and plagioclase phenocrysts contained in the basaltic icelandite from the 2000 eruption and in basalt erupted in 1913 from a fissure adjacent to the hekla volcano same elements were measured in the groundmass glass from the 2000 tephra the observed compositional range of mis from the basalt mgo 7 73 to the basaltic icelandite mgo 2 51 is readily explained by fractional crystallisation allowing the prediction of the evolution of dissolved volatile concentrations within the magma plumbing system beneath hekla the incompatible behaviour of the volatile elements controls their concentrations in mis during the crystal fractionation and consequently the highest concentrations are found in the most evolved basaltic icelandite mis with the notable exception of sulphur volatile concentrations in the basaltic mis exhibit strong linear correlations with k2o and this relationship can be used to estimate the theoretical expected volatile contents in the basaltic icelandite melt just prior to eruption such an approach avoids underestimation of the pre eruptive volatile contents measured in mis and improves constraints on the volatile mass release into the atmosphere the difference of volatile contents between expected concentrations and those present in the groundmass scaled to the mass of erupted magma yields maximum atmospheric mass loading of 0 10 mt hcl 0 17 mt hf and 3 77 mt so2 during the 2000 hekla eruption whereas calculations using the measured values in the inclusions give a significant lower mass yields of 0 05 mt hcl 0 17 mt hf and 0 6 mt so2 these results are discussed and compared to the data derived from remote sensing and snow proxy of the gas phase measurements 2007 elsevier b v all rights reserved

eddy driven recirculation of atlantic water in fram strait eddy resolving regional ocean model results in conjunction with synthetic float trajectories and observations provide new insights into the recirculation of the atlantic water aw in fram strait that significantly impacts the redistribution of oceanic heat between the nordic seas and the arctic ocean the simulations confirm the existence of a cyclonic gyre around the molloy hole near 80 n suggesting that most of the aw within the west spitsbergen current recirculates there while colder aw recirculates in a westward mean flow south of 79 n that primarily relates to the eastern rim of the greenland sea gyre the fraction of waters recirculating in the northern branch roughly doubles during winter coinciding with a seasonal increase of eddy activity along the yermak plateau slope that also facilitates subduction of aw beneath the ice edge in this area

monitoring of jokulhlaups and element fluxes in proglacial icelandic rivers using osmotic samplers the quantification of volatile emissions from volcanoes is an integral part of understanding magmatic systems with the exsolution and extent of volcanic degassing having a large impact on the nature of an eruption measurements of volatiles have traditionally focused on gas emissions into the atmosphere but volatiles can also become dissolved in proximal water bodies en route to the surface thus the monitoring of rivers draining active volcanic areas can provide insights to identifying changes in activity this process is particularly important for sub glacial volcanoes in iceland where much of the volatile release is transported within glacial outbreak floods termed jokulhlaups monitoring and characterising these phenomena is hampered by the dependence on spot sampling of stochastic events under challenging field conditions which often leads to bias in the collected data a recent technological advance is the osmotic sampler an electricity free pump that continuously collects water that can subsequently be divided into time averaged samples this technique allows for continued and unsupervised deployment of a sampler for weeks to months representing a cost efficient form of chemical monitoring in this study we deployed osmotic samplers in two rivers in southern iceland skalm is a proglacial river from m rdalsjokull glacier and katla volcano while skafta is a larger drainage system from the western part of vatnajokull glacier both rivers are prone to jokulhlaups from geothermal and volcanic sources and a small jokulhlaup of geothermal origin occurred during the second deployment in skafta in january 2014 the two deployments show that osmotic samplers are capable of delivering accurate chemical data in turbulent conditions for several key elements total dissolved fluxes for the deployment at skafta are calculated to be na 9 9 tonnes day mg 10 5 t d si 34 7 t d cl 11 0 t d ca 31 6 t d dic 50 8 t d and so4 28 3 t d with significant elevations of element concentrations during the jokulhlaup dissolved fluxes vary considerably on temporal scales from days to seasons so that spot sampling may miss pulses in concentrations this is particularly important for elements such as mn the continuous geochemical records from the osmotic samplers make it possible to identify pulses of fluxes attributed to sea spray groundwater and subglacial sources the samplers can also be combined with existing methods of river monitoring such as conductivity and discharge to accurately assess changes to fluvial chemistry due to volcanic inputs moreover there is the potential to deploy osmotic samplers in a range of other affected water bodies e g wells springs lakes to gain further insights into volcanic processes

halocline water formation in the barents sea hydrographic data from the first phase of the coordinated eastern arctic experiment cearex are analyzed the data consist of temperature and salinity measurements made by a ship based conductivity temperature depth ctd instrument and by a drifting salargos buoy these data were collected in the autumn and early winter of 1988 1989 in the northern barents sea mostly in ice covered conditions and then across the marginal ice zone miz the data show that relatively warm salty water of atlantic origin is modified by air cooling and ice melting to produce lighter water that has properties identical to lower halocline water found in the arctic ocean this occurs mostly at the miz and to a lesser degree within the ice pack itself at the miz the halocline water subducts underneath the lighter meltwater that resides directly under the ice pack geostrophic velocity calculations indicate that it then turns eastward and flows toward the kara sea in keeping with previous chemical tracer analyses a rough calculation reveals that the amount of halocline water formed in this way in the barents sea and fram strait is 30 50 of that formed by ice growth in eastern arctic polynyas

hydrography of the west spitsbergen current svalbard branch autumn 2001 1 the atlantic inflow is the primary source of water and heat to the arctic ocean a large portion enters through fram strait where it splits into the yermak and svalbard branches in october to november 2001 the uscgc healy occupied five oceanographic transects across the svalbard branch west and north of spitsbergen temperature and salinity sections show the warm salty atlantic water cooling and freshening as it flows along the continental slope for 553 km the temperature in the upper 500 m of the water column decreased by 0 25 c 100 km implying a heat flux across the sea surface of up to 520 w m2 if one assumes a nominal current of speed of 0 1 m s a temperature salinity t s analysis shows that the shape of the t s curves can be explained in terms of the ratio of the atmospheric to ice melt heat flux the observations imply that ice melt accounts for progressively more surface cooling as the flow moves toward the arctic ocean an autonomous underwater vehicle completed a vertical section in the region of maximum water mass gradient and revealed layer interleaving in fine detail data from this cruise extend a long time series of atlantic layer source temperature beginning in 1910 saloranta and haugan 2001 the extended observations show that after the temperature of the atlantic layer inflow reached a peak in 1992 it cooled to a minimum in 1998 and rose again through 2001

continuous measurements of riverine chemical constituents reveal the environmental effect of the 2014 2015 barðarbunga eruption in iceland abstract the 2014 2015 bar arbunga eruption caused one of the most intense and widespread volcanic derived air pollution events in centuries the volcanic plume was tracked all the way to central europe volcanic gas and aerosol dissolved in precipitation and accumulated as aerosol and snow on land in iceland here we report on the continuous monitoring of discharge and dissolved constituents of a direct runoff river located 85 km from the eruption site during the entire snowmelt period in 2015 osmotic samplers collected continuous water samples so short lived flood peaks would not be missed comparison between results from this 2015 study and data from 1998 to 2013 from the same river showed that average ph was 0 2 units lower in 2015 and the cl and so4 average concentration were 36 and 38 higher than prior to the eruption respectively integrated riverine fluxes of h and so4 were two to three times higher during summer 2015 than in the control years and the cl flux was 37 higher the measured excess h flux was however only a small fraction of the calculated excess h flux stemming from excess so4 and cl fluxes in 2015 which can be explained by ion exchange in the catchment soil water rock interaction consuming protons within the catchment and by elevated sea spray derived cl and so4 due to relatively high wind speed during the 2014 2015 winter in addition the small h increase in the river water can be the cause of the less than expected excess so4 riverine flux normalised to the total measured volcanogenic so2 and hcl emission fluxes 11 tg 0 1 tg which underscores the slow oxidation of so2 to so4 in relatively dry weather conditions and reduced sunlight during winter in iceland despite being sensitive to riverine ph and aluminium changes freshwater ecosystem was not threatened by the eruption since it did not cause large ph changes and the dissolved aluminium concentration was always low during the study period this study provided the means to quantify the integrated chemical fluxes and the impact of volcanic emissions on a riverine system in the vicinity of the eruption site and the implication of increased chemical fluxes of solutes of volcanic origin on the system

arctic ocean heat impact on regional ice decay a suggested positive feedback abstractbroad long living ice free areas in midwinter northeast of svalbard between 2011 and 2014 are investigated the formation of these persistent and reemerging anomalies is linked hypothetically with the increased seasonality of arctic sea ice cover enabling an enhanced influence of oceanic heat on sea ice and in particular heat transported by atlantic water the memory of ice depleted conditions in summer is transferred to the fall season through excess heat content in the upper mixed layer which in turn transfers to midwinter via thinner and younger ice this thinner ice is more fragile and mobile thus facilitating the formation of polynyas and leads when openings in ice cover form along the atlantic water pathway weak density stratification at the mixed layer base supports the development of thermohaline convection which further entrains warm and salty water from deeper layers convection induced upward heat flux from the atlantic layer retards ice formation either keeping ice thick

the immediate environmental effects of tephra emission the earth s history is punctuated by large explosive eruptions that eject large quantities of magma and silicate rock fragments into the atmosphere these tephra particles can sometimes be dispersed across millions of square kilometres or even entire continents the interaction of tephra with or in receiving environments may induce an array of physical chemical and biological effects the consequences for affected systems and any dependent communities may be chronic and localised in the event of frequent small eruptions while larger and rarer events may have acute regional scale impacts it is therefore necessary to document the range of possible impacts that tephra may induce in receiving environments and any resulting effects in interconnected systems we collate results from many studies to offer a detailed multidisciplinary and interdisciplinary review of the immediate post eruptive effects of tephra emission into the atmosphere onto vegetation soil or ice snow surfaces and in aquatic systems we further consider the repercussions that may be induced in the weeks to years afterwards in the atmosphere tephra can influence cloud properties and air chemistry by acting as ice nuclei in or by offering sites for heterogeneous reactions respectively tephra on vegetation causes physical damage and sustained coverage may elicit longer term physiological responses tephra deposits on soils may alter their capacity to exchange gas water and heat with the atmosphere or may have a specific chemical effect such as nutrient input or acidification on sensitive soils tephra deposition onto snow or ice may affect ablation rates rivers and lakes may experience turbidity increases and changes in their morphology as a result of fallout and prolonged months or years erosion from the tephra covered catchment in the first weeks after deposition tephra leaching may affect river chemistry the abundance and speciation of phytoplankton populations in lakes may be altered by tephra induced changes in water chemistry or sediment water nutrient cycling in the oceans tephra deposition may fertilise fe limited waters with potential impacts on the global carbon cycle embracing the full complexity of environmental effects caused by tephra fall demands a renewed investigative effort drawing on interdisciplinary field and laboratory studies combined with consideration of the interconnectivity of induced impacts within and between different receiving environments

chromium geochemistry and speciation in natural waters iceland abstract natural waters in iceland were collected and analyzed for chromium concentration and speciation criii crvi and crtot the water sampled included non thermal surface and spring water surface geothermal water and single and two phase geothermal well discharges with sampling temperatures of 0 178 c ph of 2 0 9 5 and total dissolved solids tds of 35 4030 ppm the total cr concentration was between 4 the measured criii concentration was low generally 8 associated with decreasing importance of mineral surface complexation hence crvi becomes an increasingly dominant form of dissolved cr at ph above 7 8 many groundwater drinking supplies associated with mafic rocks are characterized by moderately alkaline ph resulting in crvi concentrations of a few ppb

aerosol formation in basaltic lava fountaining eyjafjallajokull volcano iceland 1 a short lived episode of basaltic lava fountaining at eyjafjallajokull volcano march april 2010 produced a low altitude ash poor plume we measured the composition of aerosol particles sampled using a cascade impactor and filter packs gases sampled using filter packs and volatile species scavenged by scoria and external water in order to investigate the formation and speciation of near source aerosol 0 4 m and its composition was dominated by chloride rather than sulfate we used two thermodynamic equilibrium models e aim and hsc chemistry v5 1 to show that the formation of particulate cl by condensation of hcl gas is more responsive to changes in ambient temperature than the oxidation of so2 to so42 so that a low so42 cl ratio in aerosol particles is characteristic of volcanic emissions in cold climates field measurements suggested that the efficiency of so2 to so42 conversion inside the vent increased with lower explosivity volatiles adsorbed on the surface of scoria had significantly higher so42 halogen molar ratios than the aerosol samples several potential explanations for these differences are discussed

reaction path models of magmatic gas scrubbing gas water rock reactions taking place within volcano hosted hydrothermal systems scrub reactive water soluble species sulfur halogens from the magmatic gas phase and as such play a major control on the composition of surface gas manifestations a number of quantitative models of magmatic gas scrubbing have been proposed in the past but no systematic comparison of model results with observations from natural systems has been carried out to date here we present the results of novel numerical simulations in which we initialized models of hydrothermal gas water rock at conditions relevant to icelandic volcanism we focus on iceland as an example of a wet volcanic region where scrubbing is widespread our simulations were performed using the eq3 6 software package at shallow temperature 100 c we find that this range of model gas compositions reproduces well the h2o co2 stot compositional range of reservoir waters and surface gas emissions in iceland from this validation of the model in an extreme end member environment of high scrubbing we conclude that eq3 6 based reaction path simulations offer a realistic representation of gas water rock interaction processes occurring underneath active magmatic hydrothermal systems

arctic warming through the fram strait oceanic heat transport from 3 years of measurements we present estimates of volume and heat transport through fram strait for the period 1997 to 2000 from data of moored instruments full depth volume transports at 78 55 n were in the order of 10 sv both northwards and southwards with an annual mean net transport between 2 and 4 sv to the south the temperature of the northward flow of atlantic water had a strong seasonality with a minimum in winter nevertheless the northward heat transport was highest in winter caused by the winter maximum of northward volume transport during the three years of observation the heat transport in the west spitsbergen current increased from 28 to 46 tw as a result of both increased speed and temperature in contrast to the west spitsbergen current the volume and heat transport of east greenland current remained fairly constant an integration over a subsection of the east greenland current showed similar values of volume transport to that obtained by measurements in the 1980s foldvik et al 1988 the southward heat transport through modified atlantic water weakened slightly between 1997 and 1999 despite increased temperatures

the 1991 eruption of hekla iceland the eruption that started in the hekla volcano in south iceland on 17 january 1991 and came to an end on 11 march produced mainly andesitic lava this lava covers 23 km2 and has an estimated volume of 0 15 km3 this is the third eruption in only 20 years whereas the average repose period since 1104 is 55 years earthquakes as well as a strain pulse recorded by borehole strainmeters occurred less than half an hour before the start of the eruption the initial plinian phase was very short lived producing a total of only 0 02 km3 of tephra the eruption cloud attained 11 5 km in height in only 10 min but it became detached from the volcano a few hours later several fissures were active during the first day of the eruption including a part of the summit fissure by the second day however the activity was already essentially limited to that segment of the principal fissure where the main crater subsequently formed the average effusion rate during the first two days of the eruption was about 800 m3 s 1 after this peak the effusion rate declined rapidly to 10 20 m3 s 1 then more slowly to 1 m3 s 1 and remained at 1 12 m3 s 1 until the end of the eruption site observations near the main crater suggest that the intensity of the volcanic tremor varied directly with the force of the eruption a notable rise in the fluorine concentration of riverwater in the vicinity of the eruptive fissures occurred on the 5th day of the eruption but it levelled off on the 6th day and then remained essentially constant the volume and initial silica content of the lava and tephra the explosivity and effusion rate during the earliest stage of the eruption as well as the magnitude attained by the associated earthquakes support earlier suggestions that these parameters are positively related to the length of the preceeding repose period the chemical difference between the eruptive material of hekla itself and the lavas erupted in its vicinity can be explained in terms of a density stratified magma reservoir located at the bottom of the crust we propose that the shape of this reservoir its location at the west margin of a propagating rift and its association with a crustal weakness all contribute to the high eruption frequency of hekla

circulation and transformation of atlantic water in the eurasian basin and the contribution of the fram strait inflow branch to the arctic ocean heat budget abstract the inflows of atlantic water from the nordic seas to the arctic ocean through fram strait and over the barents sea are examined and their pathways and transformations in the eurasian basin are described based primarily on hydrographic observations from two cruises with rv polarstern in 2007 and 2011 the contrast between the high salinity atlantic water core in the nansen basin and the lower atlantic water salinity in the amundsen basin combined with a salinity minimum below the atlantic layer suggest that the fram strait branch mainly remains in the nansen basin while the barents sea branch continues along the continental slope enters the amundsen basin and provides most of the atlantic water in the makarov and canada basins to examine the consequences of such a circulation pattern recently published estimates of the in and outflows of volume and liquid freshwater through the barents sea bering strait and the canadian arctic archipelago as well as river runoff net precipitation and ice export are reviewed and added together to achieve volume and freshwater balances net outflows through fram strait of 2 3 sv and 100 msv respectively are required this is reasonably close to the recently reported fram strait transport estimates the net outflows are separated into two parts upper layer transports less dense than the entering atlantic water and lower layer transports as dense as or denser than the atlantic water the largest net volume outflow occurs in the lower layer 1 65 sv while the liquid freshwater is almost exclusively exported in the 0 64 sv net outflow in upper layer leading to unrealistically low salinities in the upper layer compared with observations atlantic water is north of svalbard transformed into less saline surface water through melting of sea ice which can supply the necessary higher salinity halocline water to the upper layer 1 23 sv of halocline water of salinity 34 2 must be added to obtain a more realistic salinity of 33 1 leading to a total export of 1 84 sv upper layer water in the east greenland current existing observations of the net transports into and out of the arctic ocean through fram strait in different temperature classes are used to estimate the heat loss of the atlantic water entering the arctic ocean through fram strait about 10 tw are supplied to the atmosphere in addition to the loss of 24 tw occurring in connection with the formation of the halocline water if the hypothesis that the fram strait branch remains in the nansen basin is true it implies a heat loss between 5 and 15 w m 2 in the nansen basin depending upon how much heat is temporarily stored in the water column this is high compared to the 2 w m 2 commonly cited as the ocean heat flux to the atmosphere in the arctic ocean

degassing regime of hekla volcano 2012 2013 hekla is a frequently active volcano with an infamously short pre eruptive warning period our project contributes to the ongoing work on improving hekla s monitoring and early warning systems in 2012 we began monitoring gas release at hekla the dataset comprises semi permanent near real time measurements with a multigas system quantification of diffuse gas flux and direct samples analysed for composition and isotopes 13c d and 18o in addition we used reaction path modelling to derive information on the origin and reaction pathways of the gas emissions hekla s quiescent gas composition was co2 dominated 0 8 mol fraction and the 13c signature was consistent with published values for icelandic magmas the gas is poor in h2o and s compared to hydrothermal manifestations and syn eruptive emissions from other active volcanic systems in iceland the total co2 flux from hekla central volcano diffuse soil emissions is at least 44 t d 1 thereof 14 t d 1 are sourced from a small area at the volcano s summit there was no detectable gas flux at other craters even though some of them had higher ground temperatures and had erupted more recently our measurements are consistent with a magma reservoir at depth coupled with a shallow dike beneath the summit in the current quiescent state the composition of the exsolved gas is substantially modified along its pathway to the surface through cooling and interaction with wall rock and groundwater the modification involves both significant h2o condensation and scrubbing of s bearing species leading to a co2 dominated gas emitted at the summit we conclude that a compositional shift towards more s and h2o rich gas compositions if measured in the future by the permanent multigas station should be viewed as sign of imminent volcanic unrest on hekla

modelling massive sulphate aerosol pollution following the large 1783 laki basaltic eruption abstract the climatic impact of volcanic eruptions depends mainly on the amount of sulphur rich gases released into the stratosphere these are rapidly converted to sulphate aerosols which result in cooling of the lower troposphere and warming of the lower stratosphere these gases are retained in the stratosphere and then concentrated by atmospheric processes forming acid fog near the earth s surface with potentially dramatic environmental consequences on plants animals and humans we have modelled such emissions in the case of the unusually large 1783 1784 basaltic fissure eruption of laki iceland using an atmospheric general circulation model results show good agreement with historical observations such as typical time taken by individual pulses to reach continental europe or geographical extent of the deadly haze that covered much of the northern hemisphere the model could be adjusted to predict the climatic consequences of very large eruptions up to the scale of massive flood basalts and test the proposal that these are the main agent in most mass extinctions of life on earth

the atlantic water boundary current in the nansen basin transport and mechanisms of lateral exchange data from a shipboard hydrographic survey near 30 e in the nansen basin of the arctic ocean are used to investigate the structure and transport of the atlantic water boundary current two high resolution synoptic crossings of the current indicate that it is roughly 30 km wide and weakly mid depth intensified using a previously determined definition of atlantic water the transport of this water mass is calculated to be 1 6 0 3 sv which is similar to the transport of atlantic water in the inner branch of the west spitsbergen current at the time of the survey a small anti cyclonic eddy of atlantic water was situated just offshore of the boundary current the data suggest that the feature was recently detached from the boundary current and due to compensating effects of temperature and salinity on the thermal wind shear the maximum swirl speed was situated below the hydrographic property core two other similar features were detected within our study domain suggesting that these eddies are common and represent an effective means of fluxing warm and salty water from the boundary current into the interior an atmospheric low pressure system transiting south of our study area resulted in southeasterly winds prior to and during the field measurements a comparison to hydrographic data from the pacific water boundary current in the canada basin under similar atmospheric forcing suggests that upwelling was taking place during the survey this provides a second mechanism related to cross stream exchange of heat and salt in this region of the nansen basin this article is protected by copyright all rights reserved

fluxes of high versus low temperature water rock interactions in aerial volcanic areas example from the kamchatka peninsula russia abstract volcanic areas play a key role in the input of elements into the ocean and in the regulation of the geological carbon cycle the aim of this study is to investigate the budget of silicate weathering in an active volcanic area we compared the fluxes of the two major weathering regimes occurring at low temperature in soils and at high temperature in the active volcanic arc of kamchatka respectively the volcanic activity by inducing geothermal circulation and releasing gases to the surface produces extreme conditions in which intense water rock interactions occur and may have a strong impact on the weathering budgets our results show that the chemical composition of the kamchatka river water is controlled by surface low temperature weathering atmospheric input and in some limited cases strongly imprinted by high temperature water rock reactions we have determined the contribution of each source and calculated the rates of co 2 consumption and chemical weathering resulting from low and high temperature water rock interactions the weathering rates between 7 and 13 7 t km 2 yr for cations only and atmospheric co 2 consumption rates 0 33 0 46 10 6 mol km 2 yr for kamchatka river due to rock weathering in soils low temperature are entirely consistent with the previously published global weathering laws relating weathering rates of basalts with runoff and temperature in the kamchatka river co 2 consumption derived from hydrothermal activity represents about 11 of the total hco 3 flux exported by the river the high temperature weathering process explains 25 of the total cationic weathering rate in the kamchatka river although in the rivers non affected by hydrothermal activity the main weathering agent is carbonic acid reflected in the abundance of hco 3 in rivers in the region most impacted by hydrothermalism the protons responsible for minerals dissolution are provided not only by carbonic acid but also by sulphuric and hydrochloric acid a clear increase of weathering rates in rivers impacted by sulphuric acid can be observed in the kamchatka river 19 of cations are released by hydrothermal acids or the oxidative weathering of sulphur minerals our results emphasise the important impact of both low and high temperature weathering of volcanic rocks on global weathering fluxes to the ocean our results also show that besides carbonic acid derived from atmospheric co 2 hydrochloric acid and especially sulphuric acid are important weathering agents clearly sulphuric acid with hydrothermal activity are key parameters that cause first order increases of the chemical weathering rates in volcanic areas in these areas accurate determination of weathering budgets in volcanic area will require to better quantify sulphuric acid impact

cooling and freshening of the west spitsbergen current by shelf origin cold core lenses the west spitsbergen current wsc cools and freshens as it flows northward along the western svalbard shelf the cooling takes place at the ocean surface through interaction with the atmosphere and also in subsurface we present observations with high horizontal resolution around 2 km from a seaexplorer glider deployed in july 2017 for 14 days in the wsc offshore kongsfjorden around 79 n they document small lenses less than 10 km diameter of cold less than 3 8 c and fresh less than 35 2 g kg waters in the core of the wsc coming from the shelf and contributing to its cooling and freshening data show that water from the shelf cascades to the bottom of the slope and then detaches on the offshore side of the wsc core where it is baroclinically unstable the presence of these lenses from the shelf can be related to the wind regime strong southerly winds cause upwelling of the warm atlantic water onto the shelf in winter weak and or northerly winds allow modified atlantic water formed by mixing with cold waters on the shelf to cascade down the slope leading to lenses of colder and fresher water protruding into the wsc if lenses are common in the wsc they could be contributing significantly to its cooling and freshening especially in summer when the influence of the atmosphere on the cooling of the wsc is less important

the chemical composition of rivers and snow affected by the 2014 2015 barðarbunga eruption iceland abstract the 2014 15 bar arbunga volcanic eruption was the largest in iceland for more than 200 years this eruption released into the atmosphere on average 60 000 tonnes day of so2 30 000 tonnes day of co2 and 500 tonnes day of hcl affecting the chemical composition of rain snow and surface water the interaction of these volcanic gases with natural waters decreases fluid ph and accelerates rock dissolution this leads to the enhanced release of elements including toxic metals such as aluminium to these waters river monitoring including spot and continuous osmotic sampling shows that although the water conductivity was relatively stable during the volcanic unrest the dissolution of volcanic gases increased the so4 f and cl concentrations of local surface waters by up to two orders of magnitude decreasing the carbon alkalinity in addition the concentration of sio2 ca mg na and trace metals rose considerably due to the water molten lava and hot solid lava interaction the presence of pristine lava and acidic gases increased the average chemical denudation rate calculated based on na flux within jokulsa a fjollum catchment by a factor of two compared to the background flux melted snow samples collected at the eruption site were characterised by a strong dependence of the ph on so4 f and cl and metal concentrations indicating that volcanic gases and aerosols acidified the snow protons balanced about half of the negatively charged anions the rest was balanced by water soluble salts and aerosols containing a variety of metals including al fe na ca and mg the concentrations of f al fe mn cd cu and pb in the snowmelt water surpassed drinking and surface water standards snowmelt river water mixing calculations indicate that low alkalinity surface waters such as numerous salmon rivers in east iceland will be more affected by polluted snowmelt waters than high alkalinity spring and glacier fed rivers

pollution from the 2014 15 barðarbunga eruption monitored by snow cores from the vatnajokull glacier iceland abstract the chemical composition of icelandic rain and snow is dominated by marine aerosols however human and volcanic activity can also affect these compositions the six month long 2014 15 bar arbunga volcanic eruption was the largest in iceland for more than 200 years and it released into the atmosphere an average of 60 kt day so2 30 kt day co2 500 t day hcl and 280 t day hf to study the effect of this eruption on the winter precipitation snow cores were collected from the vatnajokull glacier and the highlands northeast of the glacier in addition to 29 bulk snow cores from that precipitated from september 2014 until march 2015 two cores were sampled in 21 and 44 increments to quantify the spatial and time evolution of the chemical composition of the snow the ph and chemical compositions of melted snow samples indicate that snow has been affected by the volcanic gases emitted during the bar arbunga eruption the ph of the melted bulk snow cores ranged from 4 41 to 5 64 with an average value of 5 01 this is four times greater h activity than pure water saturated with the atmospheric co2 the highest concentrations of volatiles in the snow cores were found close to the eruption site as predicted from calpuff so2 gas dispersion quality model the anion concentrations so4 cl and f were higher and the ph was lower compared to equivalent snow samples collected during 1997 2006 from the unpolluted icelandic langjokull glacier higher so4 and cl concentrations in the snow compared with the unpolluted rainwater of marine origin confirm the addition of a non seawater so4 and cl the 34s isotopic composition confirms that the sulphur addition is of volcanic aerosol origin the chemical evolution of the snow with depth reflects changes in the lava effusion and gas emission rates those rates were the highest at the early stage of the eruption snow that fell during that time represented by samples from the deepest part of the snow cores had the lowest ph and highest concentrations of so4 f cl and metals compared with snow that fell later in the winter also the al concentration did exceed world health organisation drinking water standard of 3 7 mol kg in the lower part of the snow core closest to the eruption site collected snow represents the precipitation that fell during the eruption period nevertheless only minor environmental impacts are evident in the snow due to its interaction with the volcanic aerosol gases in addition the microbial communities identified in the snow that fell during the eruption were similar to those found in snow from other parts of the arctic confirming an insignificant impact of this eruption on the snow microecology

effects of volcanic eruptions on the co2 content of the atmosphere and the oceans the 1996 eruption and flood within the vatnajokull glacier iceland abstract the october 1996 eruption within the vatnajokull glacier iceland provides a unique opportunity to study the net effect of volcanic eruptions on atmospheric and oceanic co2 volatile elements dissolved in the meltwater that enclosed the eruption site were eventually discharged into the ocean in a dramatic flood 35 days after the beginning of the eruption enabling measurement of 50 dissolved element fluxes the minimum concentration of exsolved co2 in the 1 1012 kg of erupted magma was 516 mg kg s was 98 mg kg cl was 14 mg kg and f was 2 mg kg the ph of the meltwater at the eruption site ranged from about 3 to 8 volatile and dissolved element release to the meltwater in less than 35 days amounted to more than one million tonnes equal to 0 1 of the mass of erupted magma the total dissolved solid concentration in the floodwater was close to 500 mg kg ph ranged from 6 88 to 7 95 and suspended solid concentration ranged from 1 to 10 according to h o c and s isotopes most of the water was meteoric whereas the c and s were of magmatic origin both c and s went through isotopic fractionation due to precipitation at the eruption site creating short cuts in their global cycles the dissolved fluxes of c ca na si s and mg were greatest ranging from 1 4 1010 to 1 4 109 mol the dissolved c flux equaled 0 6 million tonnes of co2 the heavy metals ni mn cu pb and zn were relatively mobile during condensation and water rock interactions at the eruption site about half of the measured total carbon flood flux from the 1996 vatnajokull eruption will be added to the long term co2 budget of the oceans and the atmosphere the other half will eventually precipitate with the ca and mg released thus for eruptions on the ocean floor one can expect a net long term c release to the ocean of less than half that of the exsolved gas this is a considerably higher net c release than suggested for the oceanic crust by staudigel et al geochim cosmochim acta 53 1989 3091 in fact they suggested a net loss of c therefore magma degassed at the ocean floor contributes more c to the oceans and the atmosphere than magma degassed deep in the oceanic crust the results of this study show that subglacial eruptions affecting the surface layer of the ocean where either mn fe si or cu are rate determining for the growth of oceanic biomass have a potential for a transient net co2 removal from the ocean and the atmosphere for eruptions at high latitudes timing is crucial for the effect of oceanic biota eruptions occurring in the wintertime when light is rate determining for the growth of biota have much less potential for bringing about a transient net negative co2 flux from the ocean atmosphere reservoir

the west spitsbergen current disposition and water mass transformation recent work suggests that the west spitsbergen current which provides the principal contribution to the arctic ocean of salt and sensible heat as well as of a variety of anthropogenic tracers is a rather complex circulation feature north of 79 n where the isobaths diverge markedly the current contains two separate warm cores that follow different isobaths the western core carried by the offshore branch of the current follows the western flank of the yermak plateau and north of 80 n at least part of this flow detaches from the plateau probably to contribute to the recirculation in fram strait in contrast the inshore branch follows the shelf break into the arctic ocean it is this inshore branch that provides the primary focus in this paper during the transit of the inshore waters past northwestern spitsbergen the core properties change primarily through vertical heat flux which during ice free conditions in winter is estimated to be of the order of 200 w m 2 from the core layer alone together with some freshening within the arctic ocean this process is responsible for fully transforming the original atlantic water into arctic intermediate water within about 600 km of fram strait

mesoscale eddy activity and transport in the atlantic water inflow region north of svalbard mesoscale eddies are known to transport heat and biogeochemical properties from arctic ocean boundary currents to basin interiors previous hydrographic surveys and model results suggest that eddy formation may be common in the atlantic water aw inflow area north of svalbard but no quantitative eddy survey has yet been done for the region here vorticity and water property signatures are used to identify and track aw eddies in an eddy resolving sea ice ocean model the boundary current sheds aw eddies along most of the length of the continental slope considered from the western yermak plateau to 40 e though eddies forming east of 20 e are likely more important for slope to basin transport eddy formation seasonality reflects seasonal stability properties of the boundary current in the eastern portion of the study domain but on and immediately east of the yermak plateau enhanced eddy formation during summer merits further investigation aw eddies tend to be anticyclonic have radii close to the local deformation radius and be centered in the halocline they transport roughly 0 16 sv of aw and due to their warm cores 1 0 tw away from the boundary current these findings suggest eddies may be important for halocline ventilation in the eurasian basin as has been shown for pacific water eddies in the canadian basin

in situ aircraft observations of the 2000 mt hekla volcanic cloud composition and chemical evolution in the arctic lower stratosphere abstract an instrumented nasa aircraft made comprehensive in situ measurements of trace gas concentrations and aerosol properties while flying through the eruptive cloud from mt hekla in february and march 2000 the data reveal novel aspects of the properties and evolution of the volcanic cloud in the lower arctic stratosphere thirty five hours after the initial sub plinian explosion on february 26 2000 the aircraft intersected the cloud at an altitude of 11 3 km so2 concentrations in the cloud exceeded 1 ppmv but no h2s was observed large hf concentrations of 50 ppbv were nearly equal to the hcl concentration the same ratio of halogen species adsorbed on fallen ash although reactive nitrogen species are rarely detected in volcanic clouds significant hno3 concentrations of 3 ppbv above background were measured a bimodal aerosol size distribution with total number densities exceeding 8000 particles cm3 and total aerosol volume of 65 m3 cm3 was observed approximately 1 3 of the fine aerosol particles were non volatile volcanic ash and the remaining 2 3 were volatile sulfate aerosol and ice the volcanic cloud was highly structured with clearly delineated boundaries in the 18 day period following the initial eruption increases in so2 sulfate aerosol hcl and hf volume mixing ratios were again detected analysis of the partitioning of sulfur between the gas and aerosol phases in these later cloud encounters shows that the rate of so2 oxidation to sulfuric acid was broadly consistent with changing oh concentrations at the time of the vernal equinox

the yermak pass branch a major pathway for the atlantic water north of svalbard an upward looking acoustic doppler current profiler deployed from july 2007 to september 2008 in the yermak pass north of svalbard gathered velocity data from 570 m up to 90 m at a location covered by sea ice 10 months out of 12 barotropic diurnal and semi diurnal tides are the dominant signals in the velocity more than 70 of the velocity variance in winter baroclinic eddies at periods between 5 and 15 days and pulses of one to two month periodicity are observed in the atlantic water layer and are associated with a shoaling of the pycnocline mercator ocean global operational model with daily and 1 12 degree spatial resolution is shown to have skills in representing low frequency velocity variations 1 month in the west spitsbergen current and in the yermak pass model outputs suggest that the yermak pass branch has had a robust winter pattern over the last 10 years carrying on average 31 of the atlantic water volume transport of the west spitsbergen current 36 in autumn winter however those figures have to be considered with caution as the model neither simulates tides nor fully resolves eddies and ignores residual mean currents that could be significant