Impact of Icelandic dust and volcanic ash on snow and ice

Located on the mid-Atlantic ridge, Iceland has the largest volcaniclastic desert on Earth, created by glacio-fluvial processes and frequent volcanic eruptions. Due to its location along the North Atlantic Storm track, Iceland frequently experiences high winds. With an abundance of loose dust (particulate matter) from sandur plains and high winds, Icelandic glaciers are exposed to dust storms and redistributed ash. Deposited material is influencing glacier albedo and therefore the surface energy balance. The effects of deposited volcanic ash on ice and snow melt were examined using laboratory and outdoor experiments to find an insulating threshold and showed that ash insulated the ice at a thickness of 9-15 mm whereas maximum melt occurred at a thickness of ≤1-2 mm. To estimate the frequency of dust events, the dispersion model FLEXDUST was used to simulate dust events on Brúarjökull, a north outlet of Vatnajökull for the year 2012. All simulated dust events showed a corresponding albedo drop at the weather stations. For the weather station B13, near the ELA on Brúarjökull, FLEXDUST produced 10 major dust deposition events and a total annual deposition of 20.5 g m-2. Surface snow samples from Vatnajökull were analysed for impurities to map the distribution over the ice cap in 2013 and 2015, as well as two 4.5 m deep firn cores on Brúarjökull were drilled in 2015. The cores reached down to the year 2006 and showed distinct dust layers for the years 2014, 2012, 2011 and 2008 and only very small amounts for the years 2007 and 2013.Á Íslandi er að finna stærstu sanda heims úr basísku gjóskugleri. Þeir hafa myndast úr eldfjallaösku frá fjölda eldgosa og við jökul- og vatnsveðrun gosbergs. Mjög vindasamt er á Íslandi vegna legu landsins í brautum lægða eftir Norður Atlantshafi . Gnægð lausra efna (svifryks) í söndum landsins og vindasöm veðrátta gerir jökla á landsins útsetta fyrir sandog öskufoki. Efnið sem sest á jöklana hefur áhrif á endurkast sólarljóss frá yfirborðinu. Yfirborðið verður dekkra og tekur upp meira af orku frá sólgeislun; það hefur áhrif á orkubúskap við jökulyfirborð, leysingu og þannig afkomu jöklanna. Áhrif eldfjallaösku sem sests á snjó og ís voru rannsökuð með tilraunum, bæði á tilraunastofu og í náttúrunni. Fundin voru mörkin þar sem öskuþykkt er svo mikil að hún einangrar alveg og hindrar bráðnun íss og reyndust þau vera 9 - 15 mm. Hámarks aukning í bráðnunar varð hinsvegar þegar öskulagið er um ≤1-2 mm þykkt. Reiknilíkanið FLEXDUST, sem reiknar dreifingu loftborinna efna, var notað til að herma sandfok á Brúarjökul í norður Vatnajökli árið 2012. Við öll tilvik sandfoks sem komu fram í líkanreikningum mældist samsvarandi lægra hlutfall endurkastaðs sólarljóss frá yfirborði við sjálfvirkar veðurstöðvar á jöklinum. Við veðurstöð nærri jafnvægislínu Brúarjökuls, voru 10 tilvik verulegs sandfoks og uppsafnað magn efnis var 20.5 g/m2 samkvæmt líkanreikningunum. Kort af dreifingu ryks á yfirborði Vatnajökuls voru gerð eftir mælingum á rykmagni í snjósýnum sem safnað var af yfirborði (við hausthvörf) Vatnajökuls haustin 2013 og 2015. Einnig var borað eftir tveimur 4.5 m löngum kjörnum úr efsta hluta hjarns á safnsvæði Brúarjökuls árið 2015. Kjarnarnir náðu aftur til ársins 2006 og greinileg ryklög í þeim rakin til hausthvarfa áranna 2014, 2012, 2011 og 2008, en aðeins fannst mjög lítið ryk árin 2007 og 2013

Impact of dust deposition on the albedo of Vatnajökull ice cap, Iceland

Deposition of small amounts of airborne dust on glaciers causes positive radiative forcing and enhanced melting due to the reduction of surface albedo. To study the effects of dust deposition on the mass balance of Brúarjökull, an outlet glacier of the largest ice cap in Iceland, Vatnajökull, a study of dust deposition events in the year 2012 was carried out. The dust-mobilisation module FLEXDUST was used to calculate spatio-temporally resolved dust emissions from Iceland and the dispersion model FLEXPART was used to simulate atmospheric dust dispersion and deposition. We used albedo measurements at two automatic weather stations on Brúarjökull to evaluate the dust impacts. Both stations are situated in the accumulation area of the glacier, but the lower station is close to the equilibrium line. For this site ( ∼  1210 m a.s.l.), the dispersion model produced 10 major dust deposition events and a total annual deposition of 20.5 g m−2. At the station located higher on the glacier ( ∼  1525 m a.s.l.), the model produced nine dust events, with one single event causing  ∼  5 g m−2 of dust deposition and a total deposition of  ∼  10 g m−2 yr−1. The main dust source was found to be the Dyngjusandur floodplain north of Vatnajökull; northerly winds prevailed 80 % of the time at the lower station when dust events occurred. In all of the simulated dust events, a corresponding albedo drop was observed at the weather stations. The influence of the dust on the albedo was estimated using the regional climate model HIRHAM5 to simulate the albedo of a clean glacier surface without dust. By comparing the measured albedo to the modelled albedo, we determine the influence of dust events on the snow albedo and the surface energy balance. We estimate that the dust deposition caused an additional 1.1 m w.e. (water equivalent) of snowmelt (or 42 % of the 2.8 m w.e. total melt) compared to a hypothetical clean glacier surface at the lower station, and 0.6 m w.e. more melt (or 38 % of the 1.6 m w.e. melt in total) at the station located further upglacier. Our findings show that dust has a strong influence on the mass balance of glaciers in Iceland.The study described in this manuscript was supported by NordForsk as part of the two Nordic Centres of Excellence Cryosphere-Atmosphere Interactions in a Changing Arctic climate (CRAICC), and eScience Tools for Investigating Climate Change (eSTICC). Part of this work was supported by the Centre of Excellence in Atmospheric Science funded by the Finnish Academy of Sciences Excellence (project no. 272041), by the Finnish Academy of Sciences project A4 (contract 254195). Data from in situ mass balance surveys and on glacier automatic weather stations are from joint projects of the National Power Company and the Glaciology group of the Institute of Earth Science, University of Iceland. C. Groot Zwaaftink was also funded by the Swiss National Science Foundation SNF (155294), and Louise Steffensen-Schmidt, Finnur Palsson and Sverrir Gudmunds-son by the Icelandic Research Fund (project SAMAR) and the National Power Company of Iceland. Olafur Arnalds was in part funded by Icelandic Research Fund (grant no. 152248-051)Peer Reviewe

The Icelandic volcanic aeolian environment: Processes and impacts — A review

Iceland has the largest area of volcaniclastic sandy desert on Earth or 22,000 km2. The sand has been mostly produced by glacio-fluvial processes, leaving behind fine-grained unstable sediments which are later re-distributed by repeated aeolian events. Volcanic eruptions add to this pool of unstable sediments, often from subglacial eruptions. Icelandic desert surfaces are divided into sand fields, sandy lavas and sandy lag gravel, each with separate aeolian surface characteristics such as threshold velocities. Storms are frequent due to Iceland’s location on the North Atlantic Storm track. Dry winds occur on the leeward sides of mountains and glaciers, in spite of the high moisture content of the Atlantic cyclones. Surface winds often move hundreds to more than 1000 kg m−1 per annum, and more than 10,000 kg m−1 have been measured in a single storm. Desertification occurs when aeolian processes push sand fronts and have thus destroyed many previously fully vegetated ecosystems since the time of the settlement of Iceland in the late ninth century. There are about 135 dust events per annum, ranging from minor storms to >300,000 t of dust emitted in single storms. Dust production is on the order of 30–40 million tons annually, some traveling over 1000 km and deposited on land and sea. Dust deposited on deserts tends to be re-suspended during subsequent storms. High PM10 concentrations occur during major dust storms. They are more frequent in the wake of volcanic eruptions, such as after the Eyjafjallajökull 2010 eruption. Airborne dust affects human health, with negative effects enhanced by the tubular morphology of the grains, and the basaltic composition with its high metal content. Dust deposition on snow and glaciers intensifies melting. Moreover, the dust production probably also influences atmospheric conditions and parameters that affect climate change.Peer Reviewe

Volcanic impacts on modern glaciers: a global synthesis

Volcanic activity can have a notable impact on glacier behaviour (dimensions and dynamics). This is evident from the palaeo-record, but is often difficult to observe for modern glaciers. However, documenting and, if possible, quantifying volcanic impacts on modern glaciers is important if we are to predict their future behaviour (including crucial ice masses such as the West Antarctic Ice Sheet) and to monitor and mitigate glacio-volcanic hazards such as floods (including jökulhlaups) and lahars. This review provides an assessment of volcanic impacts on the behaviour of modern glaciers (since AD 1800) by presenting and summarising a global dataset of documented examples. The study reveals that shorter-term (days-to-months) impacts are typically destructive, while longer-term (years-to-decades) are more likely protective (e.g., limiting climatically driven ice loss). However, because these events are difficult to observe, particularly before the widespread availability of global satellite data, their frequency and importance are likely underestimated. The study also highlights that because the frequency and nature of volcano-glacier interactions may change with time (e.g., glacier retreat may lead to an increase in explosive volcanic activity), predicting their future importance is difficult. Fortunately, over coming years, continued improvements in remotely sensed data will increase the frequency, and enhance the quality, of observations of volcanic impacts on glaciers, allowing an improved understanding of their past and future operation

Microwave Radiometric Remote Sensing of Volcanic Ash Clouds From Space: Model and Data Analysis

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The Suspension of Dust and Volcanic Ash in Iceland

Dust is an important component of the earth-atmosphere system, affecting amongst other things air quality, vegetation, infrastructure, animal and human health. Iceland produces a large amount of dust, with dust storms reported frequently especially along the South Coast and in the Highlands. Nearly 20% of the country is classified as a desert with a highly erodible surface coupled with frequent windy conditions from synoptic and mesoscale weather systems which favors dust storms to occur. In addition, new material is constantly being created through glacial, fluvial, and aeolian erosion processes, as well as input of volcanic ash from volcanic eruptions. Due to the volcanic nature of Iceland, most of the material that can be suspended regularly in the atmosphere is of volcanic origin, changing critical properties of the dust relative to other major dust source regions outside of Iceland. Fresh ash, a young component of Icelandic dust, can have different properties than more aged dust particles. The different properties of fresh and aged Icelandic dust, and dust from outside of Iceland changes the parameters used for the measuring, modeling, and forecasting of dust. Fresh volcanic ash can be distinguished from aged dust particles in the lab by observing particle shapes and surface textures. Observations of dust transport, for example by satellite imagery and by weather observers, can help identify if a dust storm originated from a source area rich in young ash or more aged dust. In situ particle counting instrumentation in conjunction with meteorological measurements as well as numerical models can be used to determine when a large dust event has occurred. Synergistic use of these techniques is used to show that fresh ash provided by volcanic eruptions have a smaller impact on the number of dust events than previously assumed. Only volcanic eruptions with a Volcanic Explosive Index of 3 or greater, occurring outside of the winter season, increase the number of dust events in Iceland above the background numbers. This increase in dust events lasts typically on the scale of months, not years as previously thought. Fresh volcanic ash can be resuspended months after an eruption, but this typically occurs during dust events when more aged material is also being suspended, and therefore is not increasing the number of dust events. The conditions for dust events are very dependent on wind speed and topographical features, as a small shift in direction can dramatically change the amount of material being suspended. Precipitation and high humidity effect the strength of a dust or resuspension event, but not as much as they do in dusty areas outside of Iceland. Both aged dust and fresh volcanic ash particles have distinctive volcanic morphologies when they are greater than 20 µm in diameter. Aged dust and fresh ash particles smaller than 20 µm have a more crystalline like structure, predominantly made of blocks and plates, similar to dust from other major sources in the world. Additionally, distinguishing the surface material and ash is not possible by physical characteristics alone. The lower density of Icelandic dust compared with dust from other parts of the world allows Icelandic material to be more easily suspended and transported when compared to denser particles. For particles > 20 µm their shape and porosity has a major impact on the extent of their transport.Ryk er mikilvægur þáttur í samspili yfirborðs og lofthjúps og hefur meðal annars áhrif á loftgæði, innviði, og heilsu manna og dýra. Ísland leggur mikið til ryks á háum breiddargráðum og er sandfok (öskufok, moldrok eða sandbylur) algengt á Íslandi, þá helst við suðurströndina og á miðhálendinu. Sandfok á sér stað vegna þess að um 20% af yfirborði Íslands er flokkað sem eyðimörk (öræfi) með yfirborð sem veðrast auðveldlega og tíðs hvassviðris vegna lægða og strengja sem myndast vegna landslags. Einnig er nýtt efni sífellt að myndast vegna jökla-, áa-, og vindrofs ferla og ösku frá eldgosum. Vegna þess hve eldvirkt Ísland er, á megnið af efninu sem þyrlast upp í andrúmsloftið uppruna í eldgosum, sem er ástæða þess að sandfok á Ísland er sérstakt. Nýlega aska og eldri ryk agnir á Íslandi og frá örðrum svæðum geta haft mismunandi eiginleika og áhrif á bæði umhverfið og heilsu, því er mikilvægt að geta gert greinamun á milli þessara efna. Þessi munur hefur einnig áhrif á það hvaða eiginleikar eru notaðir mælingar og líkanreikninga. Athuganir á fokatburðum, til dæmis með gervitunglamyndum og frá mönnuðum veðurstöðvum, geta nýst til að segja til um hvort upptakasvæðið er nýleg aska eða eldra ryk. Agnateljarar (Optical Particle Counter) ásamt veðurathugunum, auk líkanreikninga, má nota til að ákvarða hvenær stór atburður hefur átt sér stað. Með því að nota gögn frá athugunum í felti, veðurupplýsingum og öðrum gögnum fannst að eldgos hafa mun minni áhrif á ryk umhverfið á Íslandi en upphaflega var talið. Aðeins stór eldgos (Volcanic Explosive Index, VEI, 3 eða hærri) sem eiga sér stað utan vetrartímans hafa sjáanleg áhrif á fjölda sandfoks atburða sem eiga sér stað á Íslandi. Hinsvegar vara áhrifin aðeins í mánuði ekki ár. Eigi að síður, getur askan þyrlast upp mánuðum eftir að eldgosi lauk, en yfirleitt gerist það með öðru fokefni og eykur því ekki tíðni fokatburða. Hvenær fok á sér stað veltur á vindhraða og landslagi, þar sem smávægilegur breytingar á vindátt geta valdið mikilli breytingu á magni efnis sem þyrlast upp. Úrkoma og rakastig hafa áhrif á stærð fokatburða, en þó minna en á öðrum svæðum heimsins. Greinileg ummerki um uppruna í eldgosum sjást á ögnum stærri en 20 µm. Agnir smærri en 20 µm eru hinsvegar líkari ögnum frá öðrum upptakasvæðum. Ekki er hægt að greina í sundur ösku og eldra ryk eingöngu á útliti agnanna. Íslenskt ryk hefur lægri eðlismassa en agnir frá öðrum upptakasvæðum heimsins og því er auðveldara að þyrla þeim upp. Lögun og gropa agna stærri en 20 µm hefur mikil áhrif á hversu langt þær berast í lofti.RANNÍS, Grant #152587-05

Tracking retreat processes at the Falljökull Glacier, SE Iceland

In glacial systems, hydrological forcing of ice velocity may lead to instability and accelerated mass loss. However, recent studies have demonstrated that the relationship between ice melt and ice dynamics is non-linear because subglacial drainage configuration strongly modulates meltwater inputs and results in asynchroneity between surface melt production and ice movement. Furthermore, subglacial drainage undergoes temporal evolution and can vary spatially between and within individual glaciers. As such, the degree of connectivity between ice melt and ice dynamics exhibits spatio-temporal variability. To address this, time-lapse images from Falljökull, SE Iceland, were analysed using Pointcatcher, a feature tracking software. Surface velocities and thinning rates were quantified for the period 2011-2013 and compared to results from energy balance modelling (EBM) to determine the climatic, hydrological and structural controls on glacier dynamics. The results show that melt production at Falljökull is closely linked to energy inputs to the glacier surface, although consistent thinning underestimation by the EBM, equivalent to ~1-3 m, reflects the poor optimisation of the model for thin debris cover. In addition, melt production is strongly modulated by individual events e.g. Grímsvötn eruption, which modify surface conditions and enhance/supress melt. A clear relationship between ice melt and ice dynamics is also evident in these data although subglacial drainage structure i.e. discrete/distributed, and surface conditions e.g. debris or snow cover, account for periods of de-coupling. Hydrologically induced speed-up events are identified and occur more readily when inefficient distributed systems are present. In contrast, flow variability is markedly reduced when meltwater inputs are suppressed and when efficient discrete drainage is present. Enhanced flow is strongly linked to sliding at the ice-bed interface although this varies spatially and temporally as a function of subglacial drainage configuration. Finally, these data conflict markedly with previous research which inferred that Falljökull was stagnant and wasting away in-situ. Instead, Falljökull is ‘active’ with movement through ice deformation, basal sliding and subglacial deformation although forward motion is insufficient to offset retreat

Using glaciers to identify, monitor and predict volcanic activity

Globally, ~250 Holocene active volcanoes are either glacier-clad or have glaciers in close proximity. The presence of glaciers on a volcano sometimes masks evidence of volcanic activity and therefore makes direct observations of volcanic activity more challenging if compared to an ‘ice-free’ volcano. However, it is also possible that glaciers can provide indirect information about the activity of the volcanoes on which they sit. With this in mind, the overall aim of this thesis is to assess the degree to which volcanically triggered impacts on glaciers can be observed from optical satellite imagery, and to consider whether these impacts can be used to help identify, monitor and predict volcanic activity. To achieve this, volcanically triggered changes in glacier surface morphology and glacier surface velocity are studied on ice-clad volcanoes using optical satellite images. Approximately 1400 optical satellite images are investigated from key, well-documented eruptions from 1972 to 2015 (i.e., during the satellite remote sensing era) and around the globe. To investigate volcanically triggered changes in surface velocity, glacier velocimetry is performed on Cone Glacier (Mount Veniaminof, Alaska) using 99 Sentinel-2 band 8 images (near-infrared, central wavelength: 842 nm) covering two volcanically active periods, one from September to December 2018 and one in March/April 2021. This approach includes the extraction of velocities along a profile line (following an inferred ice flowline), the generation of time-series velocities, and the calculation of velocity difference maps. The extensive analysis of optical satellite images around the globe shows that the most common observable volcanic impact on glacier morphology (for both thick and thin ice-masses) is ice cauldron and opening formation, often (but not exclusively) associated with concentric crevassing. Other observable volcanic impacts on glacier morphology include ice bulging and fracturing due to subglacial dome growth, localized crevassing due to supraglacial lava flows and widespread glacier crevassing, presumably, due to meltwater-triggered glacier acceleration and advance. Glacier velocimetry results from Cone Glacier show faster glacier surface velocities ~10 months prior to the 2018 volcanically active period and ~2 months prior to the 2021 volcanically active period. Also, an amplified seasonal cycle of faster-than-usual surface velocities in the summer and slower-than-usual surface velocities in the winter is observed during both years with an eruption. Volcanically triggered meltwater is considered as a cause of changing the subglacial drainage at Cone Glacier and is therefore argued as a potential cause of the observed surface velocity changes. The wider applicability of the results to other temperate and polythermal glaciers affected by volcanic activity is discussed. In all, this thesis works towards a deeper understanding of volcanic impacts on glacier morphology and dynamics, elaborates main limitations of using optical satellite images to study ice-clad volcanoes and provides advice for best practice for monitoring glaciers in volcanically active areas

Effects of black carbon and Icelandic dust on snow albedo, melt and density

Light-absorbing impurities in the cryosphere are of hydrological, environmental and climatic importance. The wet and dry deposition of black carbon (BC), organic carbon (OC), and dust particles affect the optical properties and melt of snow and ice. In the Arctic region, the climatic effects are amplified, and surface albedo feedback is often cited as the main contributor. The aim of this thesis is to fill in some of the gaps in our knowledge of the effects of BC, OC, and Icelandic dust on snow in the European Arctic through a series of field and laboratory experiments and an analysis of the resulting data, including modeling. The thesis presents a new hypothesis on the snow density effects of light-absorbing impurities, an important quantity for climate modeling and remote sensing. Three processes are suggested to explain the proposed ”BC density effect”. Experimental results show that dirty snow releases melt water quicker than cleaner snow. The albedo of natural seasonally melting snow in Sodankylä, north of the Arctic Circle, is found to be asymmetric with respect to solar midday, thus indicating a change in the properties of the snow. The radiative transfer modeling results show that the observed solar zenith angle asymmetry results in a 2–4 % daily error for satellite snow albedo estimates. Surface albedo model results indicate that the biggest snow albedo changes due to BC are expected in the ultraviolet (UV) part of the electromagnetic spectrum. The albedo of natural seasonal snow measured in Sodankylä, is found to be lower than expected. Solar UV and visible (VIS) albedo values of 0.6–0.8 in the accumulation period and 0.5–0.7 during melting are observed. The low albedo values are explained to be due to large snow grain sizes up to ∼3 mm in diameter, meltwater surrounding the grains and increasing the effective grain size, and absorption caused by impurities in the natural snow (87 ppb BC and 2894 ppb OC). The BC contents of the surface snow layer at the Sodankylä Arctic Research Center, Finland, is higher than expected. Increased BC in spring time suggests surface accumulation of hydrophobic BC during snow melt. Some of the high BC concentrations are related to anthropogenic soot transported from the Kola Peninsula, Russia. The origin of OC can be anthropogenic or natural, and may include pollen, seeds, lichens, natural litter or microorganisms that reside in snow and ice. Iceland is the most important Arctic dust source, but a scientific assessment of its impacts on the cryosphere is currently unavailable and scientific results are urgently needed to investigate the role of Icelandic dust in Iceland and elsewhere, in the past, present and future. Experimental results on Icelandic volcanic ash show that a thin layer increases the snow and ice melt but that an ash layer exceeding a certain critical thickness causes insulation. The Arctic results of this thesis have relevance to the assessment of Arctic climate change, including modeling and satellite applications