История растительности и пожаров арктической части Пур-Тазовского междуречья в голоцене

The global climate change and significantly increased anthropogenic pressure on the Arctic and Subarctic regions require modern ecosystem monitoring and understanding of the past environmental changes. Vegetation history is reflected by pollen spectra recorded in peat deposits, investigation of which is one of the main methods in the research of long-term climatic changes. In order to reconstruct the vegetation and fire history of today’s south tundra in the lower reaches of the Taz river, we carried out palynological exploration of peat and underlying lake sediments covering the last 11.2 cal ka BP in the Tazovsky district of the Yamalo-Nenets Autonomous Okrug (Russia). In the course of the research, we found 31 pollen taxa, 4 taxa of spore plants, 2 types of fungal spores, one species of shell amoeba and green algae. We have identified several stages in the development of the local wetland biocenosis at the study site and reconstructed the history of changes in the vegetation cover of the region, including changes in the composition of the woody vegetation. Grasslands, with groups of trees among thickets of shrubs and lake-mire complexes dominated in the study area by 11.2 cal ka BP. The grasslands were gradually supplemented by wet grass communities, which were then replaced by swamps and tundra complexes in the mid-Holocene. The time periods of the local fires have been established. The fire that had the greatest effect on the vegetation at the study site was detected in the period of 8.1 cal ka BP. We have revealed periods of the least fire activity – 7.6–5.5 cal ka BP and the highest fire activity – 12.5–8 cal ka BP.Чтобы реконструировать голоценовую историю растительности и пожаров современной южной тундры в нижнем течении р. Таз, мы провели палинологические исследования торфяных и подстилающих озерных отложений, сформированных за последние 11,2 кал. тыс. л. согласно полученным 8 радиоуглеродным датировкам. В ходе исследования были обнаружены: 31 пыльцевой таксон, 4 таксона споровых растений, 2 типа спор грибов, один вид раковинной амебы и зеленая водоросль. На исследуемом участке выделено несколько этапов в развитии местного водно-болотного биоценоза, реконструирована история растительного покрова региона. 11,2 кал. тыс. л. н. на исследуемой территории преобладали луга, группы деревьев в зарослях кустарников и озерно-болотные комплексы. Луга постепенно дополнялись высокопродуктивными травянистыми сообществами влаголюбивых растений, которые затем преобразовались в болота и тундровые комплексы в середине голоцена. Установлены временные периоды локальных пожаров. Пожар, который в наибольшей степени затронул растительность на исследуемом участке, произошел в период 8,1 кал. тыс. л. н. Выявлены периоды наименьшей и наибольшей пожарной активности – 7,6–5,5 кал. тыс. л. н. и 11,2–8 кал. тыс. л. н. соответственно

Изотопный состав и палиноспектры атмосферных осадков и краевых частей ледника Корумду (Северо-Чуйский хребет, Горный Алтай)

The article presents results of study of the isotope composition and pollen spectra of atmospheric precipitation and ice taken from marginal parts of Korumdu Glacier (North-Chu Ridge, the Altai Mountains). The study was aimed at identification of sources and ways of precipitation into the nival-glacial region of Altai. Investigation of the isotope composition of ice taken from the tongue of the Korumdu Glacier and summer precipitation in its basin has shown that here the isotope concentrations are much smaller than similar ones of the cold Belukha Glacier. The last one is located near the Korumdu Glacier. This difference can be explained by the fact that main source of moisture forming layers of relatively warm Korumdu Glacier is precipitation of the cold season while accumulation on the cold Belukha Glacier proceeds during the whole year mainly due to the most heavy precipitation of warm (from March to November) season. Analysis of the isotope composition and the air mass trajectories on the day of July 16, 2013 allowed conclusion that the air masses started their way in the Baltic Sea region and moved mainly along middle latitudes. On this way they underwent insignificant isotope fractionation. Synoptic analysis had shown that the main reason of precipitation on the area under investigation was a front of occlusion over the Altai. In addition, results of palynological analysis of precipitation allow identification sources of pollen in this region. With high probability we can assume that on that day the main sources of pollen in Altai precipitation are as follows: the Naryan-Mar area for Scots pine (Pinus sylvestris) pollen, tundra zones of the East European Plain for alder (Alnaster sp.) pollen and the steppe regions of Kazakhstan, and the West Altai for pollen grains – the dominant component of the pollen spectrum.Исследование изотопного состава льда языка ледника Корумду и летних осадков, выпадавших в его бассейне, показало, что изотопный состав льда изучаемого ледника значительно облегчён как относительно осадков, так и относительно ледовых слоёв расположенного недалеко от Корумду холодного ледника Белуха. Такое отличие, в первую очередь, можно объяснить тем, что основной источник влаги при формировании слоёв тёплого ледника Корумду – атмосферные осадки холодного периода года, в то время как аккумуляция на холодном леднике Белуха происходит весь год, в основном за счёт наиболее обильных осадков тёплого (с марта по ноябрь) периода года. Результаты изотопного и споровопыльцевого анализа атмосферных осадков конкретных единичных событий и данные об обратных траекториях движения воздушных масс (модель HYSPLIT) позволяют получать объективную информацию о генезисе приходящей в изучаемый регион атмосферной влаги, а также определять источники поступления и оценивать дальность переноса пыльцы тех или иных растений на исследуемую территорию. Так, по данным изотопного состава осадков, выпавших в горноледниковом бассейне ледника Корумду 16 июля 2013 г., и траектории движения воздушных масс, принёсших эти осадки на территорию Алтая, сделан вывод, что воздушные массы, начавшие свой путь в Балтике, продвигались преимущественно по умеренным широтам и подвергались незначительному изотопному фракционированию. Анализ синоптической ситуации позволяет утверждать, что основной причиной выпадения осадков на изучаемой территории стало формирование фронта окклюзии над Алтаем. Результаты спорово-пыльцевого анализа осадков дополнительно дают возможность идентифицировать источники поступления пыльцы в изучаемый регион. Например, с большой вероятностью можно предположить, что в это время район г. Нарьян-Мар служил основным источником поступления пыльцы сосны обыкновенной (Pinus sylvestris) в изучаемый ледниковый бассейн. При этом пыльца злаковых – доминирующего компонента пыльцевого спектра – может быть как местной, так и принесённой с севера степных районов Казахстана и запада Алтайского края, а пыльца ольховника (Alnaster sp.) в атмосферных осадках 16 июля 2013 г., вероятно, принесена из лесотундровой и тундровой зон Восточно-Европейской равнины

The Reading Palaeofire Database: an expanded global resource to document changes in fire regimes from sedimentary charcoal records

Sedimentary charcoal records are widely used to reconstruct regional changes in fire regimes through time in the geological past. Existing global compilations are not geographically comprehensive and do not provide consistent metadata for all sites. Furthermore, the age models provided for these records are not harmonised and many are based on older calibrations of the radiocarbon ages. These issues limit the use of existing compilations for research into past fire regimes. Here, we present an expanded database of charcoal records, accompanied by new age models based on recalibration of radiocarbon ages using IntCal20 and Bayesian age-modelling software. We document the structure and contents of the database, the construction of the age models, and the quality control measures applied. We also record the expansion of geographical coverage relative to previous charcoal compilations and the expansion of metadata that can be used to inform analyses. This first version of the Reading Palaeofire Database contains 1676 records (entities) from 1480 sites worldwide. The database (RPDv1b – Harrison et al., 2021) is available at https://doi.org/10.17864/1947.000345

Drivers of Holocene palsa distribution in North America

Palsas and peat plateaus are climatically sensitive landforms in permafrost peatlands. Climate envelope models have previously related palsa/peat plateau distributions in Europe to modern climate, but similar bioclimatic modelling has not been attempted for North America. Recent climate change has rendered many palsas/peat plateaus in this region, and their valuable carbon stores, vulnerable. We fitted a binary logistic regression model to predict palsa/peat plateau presence for North America by relating the distribution of 352 extant landforms to gridded modern climate data. Our model accurately classified 85.3% of grid cells that contain observed palsas/peat plateaus and 77.1% of grid cells without observed palsas/peat plateaus. The model indicates that modern North American palsas/peat plateaus are supported by cold, dry climates with large seasonal temperature ranges and mild growing seasons. We used palaeoclimate simulations from a general circulation model to simulate Holocene distributions of palsas/peat plateaus at 500-year intervals. We constrained these outputs with timings of peat initiation, deglaciation, and postglacial drainage across the continent. Our palaeoclimate simulations indicate that this climate envelope remained stationary in western North America throughout the Holocene, but further east it migrated northwards during 11.5–6.0 ka BP. However, palsa extents in eastern North America were restricted from following this moving climate envelope by late deglaciation, drainage and peat initiation. We validated our Holocene simulations against available palaeoecological records and whilst they agree that permafrost peatlands aggraded earliest in western North America, our simulations contest previous suggestions that late permafrost aggradation in central Canada was climatically-driven

Northern Eurasia Future Initiative (NEFI): facing the challenges and pathways of global change in the 21st century

During the past several decades, the Earth system has changed significantly, especially across Northern Eurasia. Changes in the socio-economic conditions of the larger countries in the region have also resulted in a variety of regional environmental changes that can have global consequences. The Northern Eurasia Future Initiative (NEFI) has been designed as an essential continuation of the Northern Eurasia Earth Science Partnership Initiative (NEESPI), which was launched in 2004. NEESPI sought to elucidate all aspects of ongoing environmental change, to inform societies and, thus, to better prepare societies for future developments. A key principle of NEFI is that these developments must now be secured through science-based strategies co-designed with regional decision makers to lead their societies to prosperity in the face of environmental and institutional challenges. NEESPI scientific research, data, and models have created a solid knowledge base to support the NEFI program. This paper presents the NEFI research vision consensus based on that knowledge. It provides the reader with samples of recent accomplishments in regional studies and formulates new NEFI science questions. To address these questions, nine research foci are identified and their selections are briefly justified. These foci include: warming of the Arctic; changing frequency, pattern, and intensity of extreme and inclement environmental conditions; retreat of the cryosphere; changes in terrestrial water cycles; changes in the biosphere; pressures on land-use; changes in infrastructure; societal actions in response to environmental change; and quantification of Northern Eurasia's role in the global Earth system. Powerful feedbacks between the Earth and human systems in Northern Eurasia (e.g., mega-fires, droughts, depletion of the cryosphere essential for water supply, retreat of sea ice) result from past and current human activities (e.g., large scale water withdrawals, land use and governance change) and potentially restrict or provide new opportunities for future human activities. Therefore, we propose that Integrated Assessment Models are needed as the final stage of global change assessment. The overarching goal of this NEFI modeling effort will enable evaluation of economic decisions in response to changing environmental conditions and justification of mitigation and adaptation efforts

The Eurasian Modern Pollen Database (EMPD), version 2

The Eurasian (née European) Modern Pollen Database (EMPD) was established in 2013 to provide a public database of high-quality modern pollen surface samples to help support studies of past climate, land cover, and land use using fossil pollen. The EMPD is part of, and complementary to, the European Pollen Database (EPD) which contains data on fossil pollen found in Late Quaternary sedimentary archives throughout the Eurasian region. The EPD is in turn part of the rapidly growing Neotoma database, which is now the primary home for global palaeoecological data. This paper describes version 2 of the EMPD in which the number of samples held in the database has been increased by 60 % from 4826 to 8134. Much of the improvement in data coverage has come from northern Asia, and the database has consequently been renamed the Eurasian Modern Pollen Database to reflect this geographical enlargement. The EMPD can be viewed online using a dedicated map-based viewer at https://empd2.github.io and downloaded in a variety of file formats at https://doi.pangaea.de/10.1594/PANGAEA.909130 (Chevalier et al., 2019)Swiss National Science Foundation | Ref. 200021_16959

The Eurasian Modern Pollen Database (EMPD), version 2

The Eurasian (nee European) Modern Pollen Database (EMPD) was established in 2013 to provide a public database of high-quality modern pollen surface samples to help support studies of past climate, land cover, and land use using fossil pollen. The EMPD is part of, and complementary to, the European Pollen Database (EPD) which contains data on fossil pollen found in Late Quaternary sedimentary archives throughout the Eurasian region. The EPD is in turn part of the rapidly growing Neotoma database, which is now the primary home for global palaeoecological data. This paper describes version 2 of the EMPD in which the number of samples held in the database has been increased by 60% from 4826 to 8134. Much of the improvement in data coverage has come from northern Asia, and the database has consequently been renamed the Eurasian Modern Pollen Database to reflect this geographical enlargement. The EMPD can be viewed online using a dedicated map-based viewer at https://empd2.github.io and downloaded in a variety of file formats at https://doi.pangaea.de/10.1594/PANGAEA.909130 (Chevalier et al., 2019).Peer reviewe

Biological proxies recorded in a Belukha ice core, Russian Altai

Different biological proxies such as pollen, cysts, and diatoms were identified and quantified in the upper part of a Belukha ice core from the Russian Altai. The ice core from the Belukha glacier collected in 2001 (4062 m a.s.l., 49°48' N, 86°34' E) was analyzed with annual resolution in the period 1964–2000. Daily data of the frequency of synoptic patterns observed in the Northern Hemisphere along with daily data of precipitation have been used to identify the predominant atmospheric circulations (elementary circulating mechanisms, or ECMs) generating the entry of biological proxies on the glacier surface. It was shown that the high-resolution records of diatoms, cysts, spores, and plant pollen in the Belukha ice core are the biological proxies for the changes in the structure of precipitation in the Altai region since these records can reflect changes in the contribution of different atmospheric circulation to annual or seasonal precipitation. The joint consideration of the transport ability of the biological species and the data of precipitation allowed us to determine the main modern sources of biological proxies deposited at the Belukha glacier. The main sources of diatoms in the Belukha ice core are water bodies of the Aral, Caspian, and northern Kazakhstan basins; coniferous tree pollen originated from the taiga forest of the boreal zone of western Siberia; pollen of deciduous trees and herbs from steppe and forest-steppe vegetation in the northern Altai and eastern Kazakhstan; and cysts and spores of plants were transported from local water bodies and forests. The identified source regions of the biological species are supported by back trajectory analyses and are in good agreement with emission source regions of the trace elements in the ice core

Isotopic composition and pollen spectra of precipitation and ice at the edge part of Korumdu Glacier (North Chu ridge, Altai Mountains)

The article presents results of study of the isotope composition and pollen spectra of atmospheric precipitation and ice taken from marginal parts of Korumdu Glacier (North-Chu Ridge, the Altai Mountains). The study was aimed at identification of sources and ways of precipitation into the nival-glacial region of Altai. Investigation of the isotope composition of ice taken from the tongue of the Korumdu Glacier and summer precipitation in its basin has shown that here the isotope concentrations are much smaller than similar ones of the cold Belukha Glacier. The last one is located near the Korumdu Glacier. This difference can be explained by the fact that main source of moisture forming layers of relatively warm Korumdu Glacier is precipitation of the cold season while accumulation on the cold Belukha Glacier proceeds during the whole year mainly due to the most heavy precipitation of warm (from March to November) season. Analysis of the isotope composition and the air mass trajectories on the day of July 16, 2013 allowed conclusion that the air masses started their way in the Baltic Sea region and moved mainly along middle latitudes. On this way they underwent insignificant isotope fractionation. Synoptic analysis had shown that the main reason of precipitation on the area under investigation was a front of occlusion over the Altai. In addition, results of palynological analysis of precipitation allow identification sources of pollen in this region. With high probability we can assume that on that day the main sources of pollen in Altai precipitation are as follows: the Naryan-Mar area for Scots pine (Pinus sylvestris) pollen, tundra zones of the East European Plain for alder (Alnaster sp.) pollen and the steppe regions of Kazakhstan, and the West Altai for pollen grains – the dominant component of the pollen spectrum