Mustan hiilen laskeumat Euroopan arktisella alueella esiteollisesta ajasta nykyaikaan asti

The Arctic has been warming twice as fast as the rest of the world during the last decades of global warming. Reasons for the amplified Arctic warming are thought to partly relate to positive feedbacks affecting the radiative budget of the area. Black carbon (BC) is a light-absorbing particulate produced by incomplete combustion of biomass and fossil fuels. BC strongly warms the atmosphere, and its climate effects are amplified in the Arctic where its deposition on light surfaces decreases their reflectivity, resulting in elevated heat absorption and further hastening melt of snow and ice. Globally, BC is estimated to be the second most important climate-warming agent after carbon dioxide. Historical information on BC deposition plays a significant role in the assessment of long-term climate effects of BC, but scarce data on this past variability has been available from the Arctic. Historical BC records can be attained from environmental archives, such as ice cores, peat deposits and marine and lake sediments, which store direct evidence of past BC deposition in chronological order. The objective of this thesis is to collect new spatial and temporal data on BC deposition in the European Arctic from the preindustrial to the present (i.e., the last ca. 300 years), and assess BC sources and climatic implications, by analysing five lake sediment cores from Arctic Finland and an ice core from Svalbard. No standard method exists to determine BC, and the precise definition of BC depends on the methodology used for its quantification. Here, three different analytical methods were used to quantify different components of BC. Spheroidal Carbonaceous Particles (SCP) and soot-BC (SBC) were analysed from the Arctic Finland lake sediments by SCP analysis and chemothermal oxidation at 375 °C, respectively, and elemental carbon (EC) from the Svalbard ice core with a thermal optical method. The results suggest temporal variation in past BC trends, both between study sites and between methods. While SCPs show a marked trend with fluxes peaking around 1980 and declining afterwards, they represent only a minor fraction of total BC. SBC and EC are better suited to indicate general historical BC trends. SBC fluxes vary between sites but some regional patterns are noticeable. The two northernmost lakes indicate generally decreasing SBC fluxes during the latter half of the 20th century which is in line with previous data from Greenland ice cores, modelling studies and atmospheric measurements. However, two other lake sites indicate increasing SBC fluxes from ca. 1970 to the end of the records, likely caused by local emissions from the Kola Peninsula, Russia. Moreover, an increasing EC deposition trend from ca. 1970 to 2004 is also recorded in the Svalbard ice core. This increasing trend is unexpected and unparalleled among available arctic records. The observed increase in the ice core is likely caused by flaring emissions from northern Russia. The fact that a similar trend in BC fluxes and deposition is recorded in two separate environmental archives analysed with different methods and receiving atmospheric transport from mostly different source areas, highlights the plausibility of such a trend, and implies that it may also be observable at other locations in the Arctic. In such a case, BC may have exerted a significant impact on the radiative forcing and thereby past climatic warming of the Arctic, in the most recent three or four decades. However, the present study indicates that local results cannot necessarily be extrapolated over wider areas, and therefore further studies are required to establish regional BC deposition trends within the Arctic. In addition, the study highlights that BC results obtained using different analytical methods should be compared with caution.Musta hiili eli noki on ilmastoa voimakkaasti lämmittävä pienhiukkanen, jota syntyy biomassan ja fossiilisten polttoaineiden epätäydellisessä poltossa. Noki on maailmanlaajuisesti hiilidioksidin jälkeen toiseksi tärkein tekijä ilmaston lämpenemisessä, ja sen lämmittävät vaikutukset ovat voimakkaimpia arktisella alueella. Siellä noen laskeuma tummentaa vaaleita jää- ja lumipintoja minkä seurauksena lämmön sitoutuminen voimistuu ja jään ja lumen sulaminen kiihtyy. Historiallinen tieto noen laskeumista on tärkeää arvioitaessa noen pitkän aikavälin ilmastovaikutuksia, mutta sitä on olemassa vain harvakseltaan arktiselta alueelta. Historiallista noen laskeumatietoa voidaan kerätä niin sanotuista ympäristöarkistoista, kuten jääkairasarjoista tai suo-, järvi- ja merisedimenttikerrostumista. Tämän työn tarkoituksena on kerätä uutta tietoa noen laskeumasta viimeisen noin 300 vuoden aikana sekä arvioida sen lähteitä ja ilmastovaikutuksia Euroopan arktisella alueella. Lähdeaineistona käytetään pohjoissuomalaisia järvisedimenttisarjoja ja Huippuvuorilta kerättyä jääkairasarjaa, joista noen eri osatekijöitä määritetään kolmella menetelmällä. Tulokset osoittavat merkittävää ajallista vaihtelua nokilaskeumissa ja sekä tutkimuskohteiden että analyysimenetelmien välillä. Suurimpien nokihiukkasten, niin sanottujen nokipallojen, ajallinen vaihtelu on ollut Pohjois-Suomessa samanlaista kuin aiempien tutkimusten mukaan muualla Euroopassa: laskeumat kasvoivat 1950-luvusta lähtien toisen maailmansodan jälkeisessä voimakkaassa kivihiili- ja öljyvetoisessa teollistumisessa, olivat korkeimmillaan noin 1980 ja laskivat sen jälkeen polttomenetelmien tehostumisen ja kehittyneiden ilmansuojelutoimien myötä. Nokipallot edustavat kuitenkin vain pientä osaa kokonaisnoesta, ja ilmakehässä kauemmaksi kulkeutuva pienijakoinen noki on arktiselle alueelle sitä merkittävämpää. Pienijakoisen noen laskeuman vaihtelut ovat olleet tutkimusalueella moninaisempia kuin nokipallojen. Kahden pohjoisimman tutkimusjärven nokilaskeumat ovat vähentyneet noin 1960-luvulta lähtien, mikä vastaa aiempien ilmakehämittausten ja mallinnusten tuloksia. Toisaalta kahden itäisen järven nokilaskeumat ovat kasvaneet merkittävästi 1970-luvulta lähtien nykypäivään saakka, minkä oletetaan johtuvan Kuolan niemimaan teollisuustoiminnasta. Myös Huippuvuorilta kerätyssä jääkaira-aineistossa nokilaskeuma nousi selvästi noin 1970 ja 2004 välillä, mikä on luultavasti seurausta Pohjois-Venäjällä tapahtuvasta soihdutuksesta öljyn ja maakaasun porauksen yhteydessä. Tämä havaittu nouseva trendi on odottamaton ja ennennäkemätön arktisella alueella. Se, että nousevia nokilaskeumia on havaittu kahdesta eri alueilla sijaitsevasta erityyppisestä ympäristöarkistosta ja eri analyysimenetelmillä tutkittuina, korostaa kuvatun trendin luotettavuutta ja osoittaa, että kyseinen laskeumatrendi voisi olla havaittavissa arktisilla alueilla laajemminkin. Näin ollen noella on voinut olla merkittävä rooli ilmaston lämpenemisessä arktisella alueella viimeisten vuosikymmenten aikana. Samalla tutkimus osoittaa, ettei paikallisia tuloksia voi välttämättä yleistää laajemmalle alueelle ja että lisää tutkimuksia tarvitaan alueellisesti laajemman arktisen noen laskeumahistorian todentamiseksi. Lisäksi tutkimus korostaa varovaisuuden tarvetta vertailtaessa eri analyysimenetelmillä saatuja nokituloksia

Postglacial spatiotemporal peatland initiation and lateral expansion dynamics in North America and northern Europe

Peer reviewe

Spatial and Temporal Patterns in Black Carbon Deposition to Dated Fennoscandian Arctic Lake Sediments from 1830 to 2010

Peer reviewe

Comparison of spheroidal carbonaceous particle data with modelled atmospheric black carbon concentration and deposition and air mass sources in northern Europe, 1850-2010

Peer reviewe

Observed and modeled black carbon deposition and sources in the Western Russian Arctic 1800-2014

https://doi.org/10.1021/acs.est.0c07656Black carbon (BC) particles contribute to climate warming by heating the atmosphere and reducing the albedo of snow/ice surfaces. The available Arctic BC deposition records are restricted to the Atlantic and North American sectors, for which previous studies suggest considerable spatial differences in trends. Here, we present first long-term BC deposition and radiocarbon-based source apportionment data from Russia using four lake sediment records from western Arctic Russia, a region influenced by BC emissions from oil and gas production. The records consistently indicate increasing BC fluxes between 1800 and 2014. The radiocarbon analyses suggest mainly (similar to 70%) biomass sources for BC with fossil fuel contributions peaking around 1960-1990. Backward calculations with the atmospheric transport model FLEXPART show emission source areas and indicate that modeled BC deposition between 1900 and 1999 is largely driven by emission trends. Comparison of observed and modeled data suggests the need to update anthropogenic BC emission inventories for Russia, as these seem to underestimate Russian BC emissions and since 1980s potentially inaccurately portray their trend. Additionally, the observations may indicate underestimation of wildfire emissions in inventories. Reliable information on BC deposition trends and sources is essential for design of efficient and effective policies to limit climate warming.Peer reviewe

Light-absorption of dust and elemental carbon in snow in the Indian Himalayas and the Finnish Arctic

Light-absorbing impurities (LAIs) deposited in snow have the potential to substantially affect the snow radiation budget, with subsequent implications for snow melt. To more accurately quantify the snow albedo, the contribution from different LAIs needs to be assessed. Here we estimate the main LAI components, elemental carbon (EC) (as a proxy for black carbon) and mineral dust in snow from the Indian Himalayas and paired the results with snow samples from Arctic Finland. The impurities are collected onto quartz filters and are analyzed thermal-optically for EC, as well as with an additional optical measurement to estimate the light-absorption of dust separately on the filters. Laboratory tests were conducted using substrates containing soot and mineral particles, especially prepared to test the experimental setup. Analyzed ambient snow samples show EC concentrations that are in the same range as presented by previous research, for each respective region. In terms of the mass absorption cross section (MAC) our ambient EC surprisingly had about half of the MAC value compared to our laboratory standard EC (chimney soot), suggesting a less light absorptive EC in the snow, which has consequences for the snow albedo reduction caused by EC. In the Himalayan samples, larger contributions by dust (in the range of 50% or greater for the light absorption caused by the LAI) highlighted the importance of dust acting as a light absorber in the snow. Moreover, EC concentrations in the Indian samples, acquired from a 120 cm deep snow pit (possibly covering the last five years of snow fall), suggest an increase in both EC and dust deposition. This work emphasizes the complexity in determining the snow albedo, showing that LAI concentrations alone might not be sufficient, but additional transient effects on the light-absorbing properties of the EC need to be considered and studied in the snow. Equally as imperative is the confirmation of the spatial and temporal representativeness of these data by comparing data from several and deeper pits explored at the same time.Peer reviewe

Observed and Modeled Black Carbon Deposition and Sources in the Western Russian Arctic 1800−2014

Black carbon (BC) particles contribute to climate warming by heating the atmosphere and reducing the albedo of snow/ice surfaces. The available Arctic BC deposition records are restricted to the Atlantic and North American sectors, for which previous studies suggest considerable spatial differences in trends. Here, we present first long-term BC deposition and radiocarbon-based source apportionment data from Russia using four lake sediment records from western Arctic Russia, a region influenced by BC emissions from oil and gas production. The records consistently indicate increasing BC fluxes between 1800 and 2014. The radiocarbon analyses suggest mainly (∼70%) biomass sources for BC with fossil fuel contributions peaking around 1960–1990. Backward calculations with the atmospheric transport model FLEXPART show emission source areas and indicate that modeled BC deposition between 1900 and 1999 is largely driven by emission trends. Comparison of observed and modeled data suggests the need to update anthropogenic BC emission inventories for Russia, as these seem to underestimate Russian BC emissions and since 1980s potentially inaccurately portray their trend. Additionally, the observations may indicate underestimation of wildfire emissions in inventories. Reliable information on BC deposition trends and sources is essential for design of efficient and effective policies to limit climate warming

Climatic impacts on an Arctic lake since 1300 AD: a multi-proxy lake sediment reconstruction from Prins Karls Forland, Svalbard

On the remote Arctic archipelago of Svalbard, there is increasing evidence of environmental impacts from climate change. The analysis of lake sedimentary records can be used to assess how strongly these recent changes have altered lake ecosystems. Sediments deposited during the last millennium from Lake Blokkvatnet, Prins Karls Forland, were analysed using a multiproxy approach, including stable isotope and X-ray fluorescence analysis. The results were interpreted as reflecting variability of (1) soil organic matter inwash, and potentially catchment and lake primary production, and (2) catchment weathering and erosion. Organic content began increasing after 1920 AD to the present, likely in response to warming. Earlier peaks of a similar magnitude occurred on three occasions since 1300 AD, with evidence indicating that these may have coincided with multidecadal-scale periods with higher temperatures, reduced sea ice and negative phases of the North Atlantic Oscillation. Catchment weathering and fluvial erosion began to increase around 1800 AD and peaked during the early twentieth century, potentially due to rising temperatures in autumn and winter causing increased liquid water availability. The records suggest that similar levels of erosion and weathering occurred between approximately 1300 and 1600 AD, spanning the transition from the Medieval Climate Anomaly to the Little Ice Age

Revised historical Northern Hemisphere black carbon emissions based on inverse modeling of ice core records

Black Carbon is an important climate forcer with poorly constraint historic emission fluxes and therefore large emission uncertainty. Here, ice-core data are combined with modelling to reconstruct historical emissions of Black carbon and finding gaps with the existing inventories, which implies potential climate sensitivity biasesBlack carbon emitted by incomplete combustion of fossil fuels and biomass has a net warming effect in the atmosphere and reduces the albedo when deposited on ice and snow; accurate knowledge of past emissions is essential to quantify and model associated global climate forcing. Although bottom-up inventories provide historical Black Carbon emission estimates that are widely used in Earth System Models, they are poorly constrained by observations prior to the late 20th century. Here we use an objective inversion technique based on detailed atmospheric transport and deposition modeling to reconstruct 1850 to 2000 emissions from thirteen Northern Hemisphere ice-core records. We find substantial discrepancies between reconstructed Black Carbon emissions and existing bottom-up inventories which do not fully capture the complex spatial-temporal emission patterns. Our findings imply changes to existing historical Black Carbon radiative forcing estimates are necessary, with potential implications for observation-constrained climate sensitivity.Peer reviewe