Abstract Seagrass meadows store sedimentary carbon and nitrogen and thus play an important role in climate change mitigation and nutrient retention globally. Here we reconstruct the impact of land-use and coastal land uplift on millennial–scale seagrass (Zostera marina) blue carbon and nitrogen accumulation in the Baltic Sea based on a multiproxy paleoreconstruction approach. We show that increased landscape clearance resulted in higher terrestrial runoff and increased accumulation of carbon and nitrogen, whereas land uplift led to hydrodynamically sheltered environments facilitating seagrass colonization, occurring 1700 and > 4000 years ago. The establishment of the seagrass meadows resulted in enhancement of the quality of carbon and nitrogen stocks with increased lignin contents. Seagrass establishment also likely supported export of organic matter to surrounding unvegetated areas and thereby contributed to carbon and nitrogen accumulation beyond habitat boundaries. The findings show that the long-term carbon and nitrogen accumulation rates and permanence are shaped by land cultivation and geomorphological changes and highlights the importance of seagrass conservation for maintaining thousands of years of sedimentary carbon and nitrogen storage.

Evidence from observational records and model simulations suggest that volcanic eruptions can strengthen mid- to high-latitude atmospheric circulation and enhance westerly wind strength, with recent proxy data-model assimilations supporting this. However, assessments of Holocene variability in storminess rarely consider whether major volcanic eruptions could be a possible driver of reconstructed periods of enhanced storminess. This research presents a new reconstruction of past storminess from a coastal peatbog situated in western Ireland spanning the last similar to 7 ka. The record is based on the measurement of the sand content along the core, with XRF core scanning analysis also applied to test whether variations in quartz sand, shell sand and sea spray can be detected by variations in silica, calcium and bromine respectively. Ca measurements were similar to the long-term changes in sand content along the core, however, peaks in sand content were not detected, while Si reflected increases in sand content only within the last millennium when the inorganic content was highest. Br concentrations appear to have been influenced primarily by humification. We also compared sand-based storminess records from northwest Europe. Six multi-decadal to centennial periods with enhanced storminess are common to records from Ireland and Wales during the last 2.5 ka BP, centred at c. 2.25, 2, 1.4, 1.1, 0.5 and 0.2 ka BP, with less agreement between records before this time. The storm periods at 2.8, 2.2-2, 1.1 and 0.5 ka BP are more widespread events and agree with records from Sweden and Scotland. Each of the episodes of increased storminess coincide roughly with major volcanic eruptions during the late Holocene, as well as with periods of enhanced North Atlantic ice-rafting. We hypothesise, therefore, that both enhanced storminess and ice-rafting may have resulted from the climate and environmental impacts of these eruptions, aligning with the findings of recent observational and modelling studies on the climate response to eruptions. Challenges remain, however, in testing this hypothesis, given chronological uncertainties in peatland records and uncertain interpretations of the factors influencing sand deposition. Therefore, to provide an independent assessment of the influence of explosive eruptions on storminess for Ireland's northeast Atlantic position, we draw upon the rich tradition of annalistic record keeping on the island, including many reports of major storms and windy seasons, to develop a windiness index running from the sixth to seventeenth centuries CE. A set of superposed epoch analyses shows that the ice-core-based dates of explosive volcanic eruptions are statistically significantly associated with the dates of documented storms and windy seasons in Ireland, suggesting avenues for future research.

High-latitude regions are emerging as sensitive and potentially expanding sources of atmospheric mineral dust under contemporary climate warming. Aeolian activity in sub-Arctic landscapes such as Sweden during the last deglaciation may therefore act as a valuable analogue for understanding these future high-latitude dust–climate feedbacks. However, the timing and drivers of postglacial aeolian activity in Sweden remains uncertain. Furthermore, Swedish wind-blown loess deposits are thin and prone to reworking, complicating reliable age determination. Here, we combine high sampling resolution luminescence (quartz OSL, feldspar IRSL) and radiocarbon dating with complementary sedimentological, mineral magnetic and multi-proxy luminescence signal analyses to resolve postglacial–Holocene aeolian activity at Brattforsheden, Värmland. Our analyses demonstrate the value of luminescence sensitivity and portable OSL for assessing age reliability and differentiating between reworked and in situ deposits in thin loess sediments. We show that an intense but short period of postglacial-Holocene aeolian activity occurred in central Sweden immediately following deglaciation, with dust activity persisting for ~ 1500 years after regional ice retreat. We also reveal a later aeolian reworking phase linked to local fire activity at ~ 7 ka, setting new constraints on high-latitude dust dynamics under changing conditions, and implying that even during peak Holocene warmth the landscape was sensitive to aeolian reworking and dust emission could occur.

Stalagmites are well-known as paleoclimatic archives, but recent work [e.g., 1,2] has also demonstrated their paleobiological potential as archives of ancient animal and plant DNA. Because of this property, stalagmites have the potential to provide information on how past climatic fluctuations have impacted land fauna, specifically cave fauna of which bats are key ecosystem services providers. The aim of this work is to use stalagmites to gain precisely such knowledge. With this endeavour, we acquired geochemical data (Sr/Ca, δ18O, δ13C) along the growth axis of three early Holocene stalagmites from Ireland, which we used for climatic and environmental reconstruction. In addition, we acquired ancient DNA data in stalagmite laminae, including those where climatic and environmental shifts were observed. Results of these analyses are presented here and include new U-Th-dated stable isotopic curves and ancient DNA data chronologically anchored to stalagmite-derived climatic records. We also discuss our analytical workflow and the pros and cons we faced while combining geological and biological data on stalagmites such as data acquisition resolution, stalagmite chemistry, and DNA data quality. [1] Stahlschmidt et al. (2019) Scientific Reports, 9, 6628. [2] Marchesini et al. (2023) Quaternary Research, 112, 180-188

A common approach to investigating species' niches is to examine relationships between spatial variation in environmental conditions and contemporary species occurrences, using species distribution models (SDM or niche models). The relationships between past species distributions and environmental variation over time are less commonly explored. One way to examine effects on species changes over time is to use paleo-datasets to parameterize niche models, where the use of temporal variation allows for making more direct links between past species and environmental conditions through records of past changes. We examined the impact of five environmental variables (temperature, incidence of external nutrient input, local [within bog] moisture, incidence of regionally dry periods, and fire activity) on temporal variation in peatland species composition, occurrences, and abundances (Sphagnum, Eriophorum, Carex, and Ericaceous dwarf shrubs) using a high-resolution peat macrofossil paleo-record spanning the last ~10,000 years from the Store Mosse bog (south-central Sweden). Our results showed that species composition was affected by external nutrient input, local moisture conditions and incidence of regionally dry conditions. The presence and abundance of different species groups were mainly affected by external nutrient input and the incidence of regionally dry periods. Moreover, hummock Sphagna benefited from external nutrient input and low moisture, and in one species, warmer temperatures. Intermediate Sphagna from cooler temperatures with no external nutrient input, and hollow Sphagna from cooler temperatures and external nutrient input. Lastly, our results showed that environmental effects differed between the successional stages of the peatland in one case. Overall, the observed species' responses imply that peatland carbon dynamics will shift with future changes in climate. By examining links between climate and species responses of the past, this study demonstrates that the paleo-data approach in SDMs can contribute to a better understanding of the environmental effects influencing species distributions on longer time scales, thereby providing a valuable tool to improve predictions of future climate change effects.

Geological reconstructions of relative sea level (RSL) from southern Norway show falling RSL during the last 7000 cal. a BP, but tide gauge measurements document a slow RSL rise since at least 1960 CE. With an age gap of c. 1400 years between the youngest geologically reconstructed sea‐level index point (SLIP) and the installation of the Tregde tide gauge in southernmost Norway, the exact nature and timing of the onset of RSL rise in southern Norway remain unknown. To fill this gap, we collected peat cores from a salt marsh to reconstruct RSL trends over the past 1000 years using a multiproxy approach, including 210 Pb and 14 C dating, grain‐size analysis, loss‐on‐ignition (LOI), geochemistry (stable carbon isotopes, carbon to nitrogen ratios and XRF) and diatoms. Our data suggest decreasing tidal current strength and salinity over most of the last millennium, suggesting falling RSL. Sediment geochemistry also appears to vary with wetter and drier climatic periods. An increase in marine‐brackish diatoms in combination with an acceleration in sedimentation rates after 1930 CE (1899–1954 CE) suggest that the onset of RSL rise began around this time in southernmost Norway. While most of the proxy data appear to have delayed sensitivity to RSL changes and may be linked to other causal processes, they, nonetheless, provide valuable insight into the environmental response of high‐latitude temperate salt marshes to slow rates of RSL change.

Tropical Asia is a critical component of the global climate system as it provides large amounts of moisture and heat to the extratropics and drives monsoons on both hemispheres. Paleoclimate information remains relatively scarce from the region despite its global significance, calling for additional records from the region. We generated a multiproxy peat record from Sumatra, with a focus on deconvolving seasonal and annual precipitation signals, as well as long term temperature variability. We do this by analyzing the n-alkane distributions reflecting vegetation variability, and the hydrogen isotopic composition (δDalkanes) from alkanes sourced from algae and terrestrial plants. Algae grows during the wet season, while terrestrial plants grow over the whole year, and they therefore reflect the water isotopic signal from different parts of the year. We further analyze the GDGT composition in the peat core to derive information about temperature and hydrological changes. Finally, levoglucosan was measured to reconstruct past wildfire events. We find that the climate on Sumatra was much more seasonal in the Mid-Holocene than in the Late Holocene, based on the difference between δDterrestrial and δDalgae. In particular, the period between 4-6 ka BP was extremely seasonal, with alternating floods, droughts and fires. This extreme seasonality is coeval with an Asian Summer Monsoon collapse, Australian Summer Monsoon invigoration and the collapse of Green Sahara, suggesting large scale tropical atmospheric reorganization in that period. Our multiproxy annual precipitation reconstruction indicates the wettest overall conditions between 3.3-4.5 ka BP. which is approximately 1500-2000 years later than indicated by a nearby speleothem δ18O record, which instead is more similar to δDalgae. We therefore hypothesize that speleothem reconstructions in the region record a wet season isotopic signal, similar to the algae, since cave groundwater recharge occur mainly after heavy precipitation. The Late Holocene is marked by rapid drying around 2.8 ka BP, under a much less seasonal climate, which is coeval with the strengthening of ENSO variability in the Pacific Ocean. In summary, our multiproxy peat record from Sumatra resolves the seasonal versus annual components of past rainfall variability, revealing heightened seasonality during the Mid-Holocene, significant shifts in precipitation pattern, and a notable Late Holocene drying trend. Our findings highlight the importance of considering the δD signal from the full range of alkanes and considering seasonal variability in paleoclimatological reconstructions.

Substantial uncertainties exist regarding how future climate change will affect storminess (storm frequency and intensity) in Ireland and the United Kingdom (UK). Knowledge about spatiotemporal variations of past storminess gives us a better understanding of its mechanisms on centennial to millennial time scales, as well as the impact of external forcing on future storminess in climate models. Here, we present the oldest storm record to date from Ireland, covering the last 8000 years, reconstructed from the Roycarter Bog, a coastal blanket bog in north-western Ireland. The sequence was analysed for grain-size, chemical, mineral and organic molecular composition. The chronology was built on 11 AMS radiocarbon dates. The deposit characteristics, location and low inorganic content suggest aeolian transport of particles to the bog throughout the studied period. Cluster analysis of the grain-size frequency curves, along with the coarse to fine sand ratio, allowed the identification of eleven storm periods (cal yr BP): 6150-5500 (1); 4970-4130 (2); 4000 (3); 3490-3290 (4); 3230 (5); 2850-2590 (6); 2170-1920 (7); 1440 (8); 1225-890 (9); 620-470 (10); and 290-230 (11). During the mid-Holocene, the relative sea level was lower and the local beach sources located further away, giving a longer transport distance compared to the late Holocene. In the latter part of the mid-Holocene (6150-4130 cal yr BP), during the Holocene thermal maximum, increased storminess and wind strengths were inferred for north-western Ireland, manifested as two longer storm periods. During the late Holocene the storm frequency increased, and a greater number (9) of shorter storm periods were recorded. Comparison between our results and regional peat palaeostorm records from Scotland, north of our study site, showed an antiphase relationship between storminess in Ireland and Scotland during the latter part of the mid-Holocene, but mostly in-phase storminess over the last 3000 years. Taken together, enhanced wind strength and storminess were recorded during the warmer mid-Holocene, while an increased frequency of storm events occurred in the cooler late Holocene. Mid-Holocene storm periods occurred during locally wet periods, while most of the storm periods during late Holocene occurred during drier phases. Alternatively, the elevated mineral input during late Holocene promoted microbial activity and peat decomposition. The apparent variability in cyclicity and frequency between the mid- and late Holocene indicates that the processes governing storminess in the region shifted. This calls for further studies ahead, including climate modelling, to disentangle the complex processes governing storminess on millennial to centennial time scale.

Assessing historical environmental conditions linked to habitat colonization is important for understanding long-term resilience and improving conservation and restoration efforts. Such information is lacking for the seagrass Zostera marina, an important foundation species across cold-temperate coastal areas of the Northern Hemisphere. Here, we reconstructed environmental conditions during the last 14,000 years from sediment cores in two eelgrass (Z. marina) meadows along the Swedish west coast, with the main aims to identify the time frame of seagrass colonization and describe subsequent biogeochemical changes following establishment. Based on vegetation proxies (lipid biomarkers), eelgrass colonization occurred about 2,000 years ago after geomorphological changes that resulted in a shallow, sheltered environment favoring seagrass growth. Seagrass establishment led to up to 20- and 24-fold increases in sedimentary carbon and nitrogen accumulation rates, respectively. This demonstrates the capacity of seagrasses as efficient ecosystem engineers and their role in global change mitigation and adaptation through CO2 removal, and nutrient and sediment retention. By combining regional climate projections and landscape models, we assessed potential climate change effects on seagrass growth, productivity and distribution until 2100. These predictions showed that seagrass meadows are mostly at risk from increased sedimentation and hydrodynamic changes, while the impact from sea level rise alone might be of less importance in the studied area. This study showcases the positive feedback between seagrass colonization and environmental conditions, which holds promise for successful conservation and restoration efforts aimed at supporting climate change mitigation and adaptation, and the provision of several other crucial ecosystem services. Plain Language Summary This study investigated the historical colonization of eelgrass (Zostera marina), an important marine vascular plant in cold-temperate coastal regions. Sediment cores from eelgrass meadows on the Swedish west coast dating back as far as 14,000 years were examined to understand the time-course of eelgrass colonization and the subsequent modification of the environment. We found that eelgrass colonization began approximately 2,000 years ago, coinciding with the development of shallow, sheltered conditions that favored eelgrass growth. As eelgrass became established, this led to substantial habitat and sediment changes, including a 20- and 24-fold increase in carbon and nitrogen accumulation, respectively. This highlights the crucial role of eelgrass as a provider of important ecosystem services, such as regulation of climate, nutrient retention, and sediment protection. We also examined the potential effects of climate change on eelgrass growth and health, predicting that decreased water clarity and altered water flow pose the greatest risks. Overall, this study adds valuable insights into the relationship between eelgrass and its environment, aiding in conservation and restoration efforts to mitigate climate change and maintain essential ecosystem services. It emphasizes the importance of specific environmental conditions for successful eelgrass colonization and restoration.

Inorganic geochemistry is a powerful tool in paleolimnology. It has become one of the most commonly used techniques to analyze lake sediments, particularly due to the development and increasing availability of XRF core scanners during the last two decades. It allows for the reconstruction of the continuous processes that occur in lakes and their watersheds, and it is ideally suited to identify event deposits. How earth surface processes and limnological conditions are recorded in the inorganic geochemical composition of lake sediments is, however, relatively complex. Here, we review the main techniques used for the inorganic geochemical analysis of lake sediments and we offer guidance on sample preparation and instrument selection. We then summarize the best practices to process and interpret bulk inorganic geochemical data. In particular, we emphasize that log-ratio transformation is critical for the rigorous statistical analysis of geochemical datasets, whether they are obtained by XRF core scanning or more traditional techniques. In addition, we show that accurately interpreting inorganic geochemical data requires a sound understanding of the main components of the sediment (organic matter, biogenic silica, carbonates, lithogenic particles) and mineral assemblages. Finally, we provide a series of examples illustrating the potential and limits of inorganic geochemistry in paleolimnology. Although the examples presented in this paper focus on lake and fjord sediments, the principles presented here also apply to other sedimentary environments.

Northern peatlands store globally-important amounts of carbon in the form of partly decomposed plant detritus. Drying associated with climate and land-use change may lead to increased fire frequency and severity in peatlands and the rapid loss of carbon to the atmosphere. However, our understanding of the patterns and drivers of peatland burning on an appropriate decadal to millennial timescale relies heavily on individual site-based reconstructions. For the first time, we synthesise peatland macrocharcoal re-cords from across North America, Europe, and Patagonia to reveal regional variation in peatland burning during the Holocene. We used an existing database of proximal sedimentary charcoal to represent regional burning trends in the wider landscape for each region. Long-term trends in peatland burning appear to be largely climate driven, with human activities likely having an increasing influence in the late Holocene. Warmer conditions during the Holocene Thermal Maximum (similar to 9e6 cal. ka BP) were associated with greater peatland burning in North America's Atlantic coast, southern Scandinavia and the Baltics, and Patagonia. Since the Little Ice Age, peatland burning has declined across North America and in some areas of Europe. This decline is mirrored by a decrease in wider landscape burning in some, but not all sub-regions, linked to fire-suppression policies, and landscape fragmentation caused by agricultural expansion. Peatlands demonstrate lower susceptibility to burning than the wider landscape in several instances, probably because of autogenic processes that maintain high levels of near-surface wetness even during drought. Nonetheless, widespread drying and degradation of peatlands, particularly in Europe, has likely increased their vulnerability to burning in recent centuries. Consequently, peatland restoration efforts are important to mitigate the risk of peatland fire under a changing climate. Finally, we make recommendations for future research to improve our understanding of the controls on peatland fires.(c) 2023 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

Severe extratropical winter storms are a recurrent feature of the European climate and cause widespread socioeconomic losses. Due to insufficient long-term data, it remains unclear whether storminess has shown a notable response to changes in external forcing over the past millennia, which impacts our ability to project future storminess in a changing climate. Reconstructing past storm variability is essential to improving our understanding of storms on these longer, missing timescales. Peat sequences from coastal ombrotrophic bogs are increasingly used for this purpose, where greater quantities of coarser grained beach sand are deposited by strong winds during storm events. Moving inland however, storm intensity decreases, as does sand availability, muting potential paleostorm signals in bogs. We circumvent these issues by taking the innovative approach of using mid-infrared (MIR) spectral data, supported by elemental information, from the inorganic fraction of Store Mosse Dune South (SMDS), a 5000-year-old sequence from a large peatland located in southern Sweden. We infer past changes in mineral composition and thereby, the grain size of the deposited material. The record is dominated by quartz, whose coarse nature was confirmed through analyses of potential local source sediments. This was supported by further mineralogical and elemental proxies of atmospheric input. Comparison of SMDS with within-bog and regionally relevant records showed that there is a difference in proxy and site response to what should be similar timing in shifts in storminess over the-100 km transect considered. We suggest the construction of regional storm stacks, built here by applying changepoint modelling to four transect sites jointly. This modelling approach has the effect of reinforcing signals in common while reducing the influence of random noise. The resulting Southern Sweden-Storm Stack dates stormier periods to 4495-4290, 3880-3790, 2885-2855, 2300-2005, 1175-1065 and 715-425 cal yr BP. By comparing with a newly constructed Western Scotland-Storm Stack and proximal dune records, we argue that regional storm stacks allow us to better compare past storminess over wider areas, gauge storm track movements and by extension, increase our understanding of the drivers of storminess on centennial to millennial timescales.(c) 2022 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

<p>Most relative sea level (RSL) curves in Norway have been solidly constructed using sea-level index points (SLIPs) from isolation basins. Many of these curves show RSL falling at a slow and steady rate to modern sea level during the late Holocene, despite a lack of SLIPs younger than ca. 2000 years. Tide gauge records from southern and western Norway indicate that RSL may have been rising since they were installed (ca. 100 years ago), while the few RSL curves with one or two SLIPs younger than 2000 years BP hint that rates of sea-level fall accelerated during this period. This study aims to close the gap between palaeo and instrumental data by generating late Holocene SLIPs from low-elevation and intertidal basins in southwestern Norway. Geochemical analyses of the sediment cores from all the studied areas thus far suggests that marine influence has been increasing in recent centuries, possibly due to rates of eustatic sea level rise overtaking residual glacioisostatic adjustment (ca. 1-2 mm/yr) from the Last Glacial Maximum. Anecdotal evidence from local residents of Egersund, with family histories and records of past storm levels going back to the 1800s, confirm this. Discrete storm layers consisting of shell fragments in one salt marsh at the back of a sheltered intertidal basin, however, may be overprinting any subtle trends in recent RSL rise. Full results of multi-proxy analyses of 8 cores from four salt marshes and protected, intertidal basins with bedrock sills will be presented from the southwestern corner of Norway.</p>

The exact spatial and temporal behaviour of rapid climate shifts during the Last Glacial–Interglacial Transition are still not entirely understood. In order to investigate these events, it is necessary to have detailed palaeoenvironmental reconstructions at geographically spread study sites combined with reliable correlations between them. Tephrochronology, i.e., using volcanic ash deposits in geological archives as a dating and correlation tool, offers opportunities to examine the timing of events across wider regional scales. This study aims to review the posited asynchrony of the Younger Dryas stadial in comparison with Greenland Stadial-1 by correlating new proxy data from southernmost Sweden to previous palaeoclimate reconstructions in Europe based on the presence of the Hässeldalen Tephra, the Vedde Ash, and the Laacher See Tephra. μ-XRF core-scanning data were projected using a recently published age–depth model based on these tephras and several radiocarbon dates, and compared to previous findings, including by adapting previous chronologies to the recently proposed earlier date of the Laacher See Tephra (13,006 ± 9 cal. a BP). Although the results to some extent support the idea of a more synchronous Younger Dryas event than previously assumed, this issue requires further high-resolution proxy studies to overcome limitations of temporal precision.

Sediments from the only permanent lake on the island of Jan Mayen (71°N, 08°30′W), Lake Nordlaguna (NL), were investigated. The lake, with an area of ∼1 km2, is situated at the foot of the world's northernmost active subaerial volcano and is separated from the sea by a 150–240 m wide beach barrier, which reaches 4–5 m above sea level. Most of the lake is deeper than 25 m, with the deepest part being 36 m. Altogether five coring sites, evenly spread out, were chosen and the sediment cores were retrieved from the lake ice with Uwitec and Nesje corers. After detailed descriptions of the very organic-poor and silt dominated sediments (of supposedly tephra-dominated origin), three sites were chosen for further analyses: macrofossils for 14C dating, tephra chemistry, C, S, grain-size, and XRF analyses. Based on 14C dates and the occurrence of the so-called Eggøya tephra (AD 1732), age models show variable bottom ages for the three sites: ∼3000, 600 and 400 cal yr BP. Due to the position of the core sites, with different sediment source areas, the elemental signals vary considerably between sites. An interesting feature of the lake is an isolated stock of Arctic char, which shows that the now land-locked lake has once been in contact with the sea. The almost total lack of organic material excluded any advanced paleo-ecologic investigations of the lake, and the study therefore focused on its marine-limnic history by different examinations of the XRF data with focus on the oldest and longest record. This development is based on elemental ratios (Br/Zn), PCA analyses of a center log ratio (clr) transformation of the original XRF data and magnetic susceptibility. It shows that the lake was isolated just before the time of the Eggøya tephra fall-out (∼220 cal yr BP), when the stock of Arctic char was most likely isolated from the sea. This was preceded by a ∼2200 yr long period of marine bay with a more or less open connection with the sea, and thus varying fresh-water impact. Between ∼2400 and 2600 cal yr BP the basin was more or less isolated, preceded by almost full marine conditions for at least the 300–400 preceding years we have data from, a period when relative sea level might have been higher.

Boreal peatlands are facing significant changes in response to a warming climate. Sphagnum mosses are key species in these ecosystems and contribute substantially to carbon sequestration. Understanding the factors driving vegetation changes on longer time scales is therefore of high importance, yet challenging since species changes are typically affected by a range of internal and external processes acting simultaneously within the system. This study presents a high‐resolution macrofossil analysis of a peat core from Store Mosse bog (south‐central Sweden), dating back to nearly 10 000 cal. a BP. The aim is to identify factors driving species changes on multidecadal to millennial timescales considering internal autogenic, internal biotic and external allogenic processes. A set of independent proxy data was used as a comparison framework to estimate changes in the bog and regional effective humidity, nutrient input and cold periods. We found that Store Mosse largely follows the expected successional pathway for a boreal peatland (i.e. lake → fen → bog). However, the system has also been affected by other interlinked factors. Of interest, we note that external nutrient input (originating from dust deposition and climate processes) has had a negative effect on Sphagnum while favouring vascular plants, and increased fire activity (driven by allogenic and autogenic factors) typically caused post‐fire, floristic wet shifts. These effects interactively caused a floristic reversal and near disappearance of a once‐established Sphagnum community, during which climate acted as an indirect driver. Overall, this study highlights that the factors driving vegetation change within the peatland are multiple and complex. Consideration of the role of interlinked factors on Sphagnum is crucial for an improved understanding of the drivers of species change on short‐ and long‐term scales.

Sediments from the only permanent lake on the island of Jan Mayen (71°N, 08°30’W), Lake Nordlaguna (NL), were investigated. The lake, with an area of ~1 km 2 , is situated at the foot of the world´s northernmost active subaerial volcano and is separated from the sea by a 100-300 m wide beach barrier, situated a couple of meters above sea level. Most of the lake is deeper than 25 m, with the deepest part being 36 m. Altogether five drilling sites, evenly spread out, were chosen and the sediment cores were retrieved from the lake ice with Uwitec and Nesje corers. After detailed descriptions of the very organic-poor and silt dominated sediments (of supposedly tephra-dominated origin), three sites were chosen for further analyses: macrofossils for 14 C dating, tephra chemistry, C, S, grain-size, and XRF analyses. Based on 14 C dates and the occurrence of the so-called Eggøya tephra (AD 1732), age models show variable bottom ages for the three sites: ~3000, 600 and 400 cal yr BP. Due to the position of the core sites, with different sediment source areas, the elemental signals vary considerably between sites. An interesting feature of the lake is an isolated stock of Arctic char, which shows that the now land-locked lake has once been in contact with the sea. The almost total lack of organic material excluded any advanced paleoecologic investigations of the lake, and the study therefore focussed on its marine-limnic history by different examinations of the XRF data with focus on the oldest core. This development is based on elemental ratios (Br/Zn), PCA analyses of a center log ratio (clr) transformation of the original XRF data and magnetic susceptibility. It shows that the lake was isolated just before the time of the Eggøya tephra fall-out (~220 cal yr BP), when the stock of Arctic char was most likely isolated from the sea. This was preceded by a ~2200 yr long period of marine bay with a more or less open connection with the sea, and thus varying fresh-water impact. Between ~2400-2600 cal yr BP the basin was more or less isolated, preceded by almost full marine conditions for at least the 300-400 preceding years we have data from, a period when relative sea level might have been higher.

Atmospheric mineral dust not only interacts with the climate system by scattering incoming solar radiation and affecting atmospheric photochemistry, but also contributes critical nutrients to marine and terrestrial ecosystems. In a high-resolution analysis of paleodust deposition, peat development and soil dust sources, we assess the interplay between dust deposition and bog development of the Davidsmosse bog in south-western Sweden. Analyses of the 5400-year record (458 cm) included radiocarbon dating, bulk density, ash content, chemical and mineralogical composition and carbon stable isotopes, subsequently explored using principal component analysis. Fourteen dust events (DEs) were recorded (cal BP) in the peat sequence: 3580???3490; 3280; 3140; 3010???2840; 2740; 2610; 2480; 2340; 2240???2130; 1690; 1240; 960, 890???760, and 620???360. The majority of the DEs were coupled to increases in peat accumulation rates and increased nutrient content (N, P and K) suggesting that the DEs contributed with nutrients to the bog ecosystem, promoting increased accumulation. We also analyzed the chemical and mineral composition of potential mineral source deposits (separated into 6 grain-size fractions) from sites within a 4 km radius as well as aeolian dunes closer to the coast (25 km). The composition deposited on the present-day bog surface indicates that the bulk of the contemporary minerals have a local origin (<1.5 km), but the DEs may be of a more distant origin. The results also indicate that quartz and plagioclase feldspar content consistently increase with increasing grain-size, both in the source samples as well as in the peat sequence, and that the Si/Al ratio can be used to infer grain size changes in the peat. Two longer phases saw numerous DEs, between 2800 and 2130 cal BP and a stepwise increase from 960 towards 360 cal BP. The episodic character of the events, together with the inferred coarse grain size, suggest that the particles were deposited by (winter) storms. Future studies should include grain size analysis as well as a more in-depth comparison with regional paleo dust and storm records to increase knowledge on both transport processes (creep, saltation, suspension) and the climate processes driving late Holocene dust and storm events in Scandinavia.

Despite immense progress in the last decades, the Holocene climate evolution is still poorly resolved, in particular in the tropics, and especially from a terrestrial perspective. Here we reconstruct 11 000 years of paleo-climate and environment in the western Indo-Pacific Warm Pool – “the heat and steam engine of the world” – by analysing biomarker and geochemical proxies in peat sediments from Sumatra. We discuss the composition of archaeal and bacterial membrane lipids (branched and isoprenoid glycerol dialkyl glycerol tetraethers; GDGTs) and their relationship with temperature and other environmental conditions. By analysing the hydrogen isotopes of leaf waxes (dDwax) we reconstruct past rainfall amounts. X-Ray Fluorescence (XRF) derived geochemical composition reveals changes in erosional regimes. Additionally, we use long-chain n-alkane distributions, carbon and nitrogen analysis, and attenuated reflectance Fourier-Transform Infrared analysis (FTIR-ATR) to investigate changes in vegetation on the peatland. Three main climate-environmental phases emerge in our record: 1) Relatively cold, dry and unstable conditions during the Early Holocene which is marked by high detrital input into the peatland. 2) Warm, wet and stable conditions coincided with the mid-Holocene period, 8.2 – 3.2 ka BP. Using a global peat-specific temperature calibration based on branched GDGTs (Naafs et al., 2017), we derive mean annual air temperatures peaking at 4.8 ka BP that are ~3 °C warmer compared to core-top and modern local weather station data. The warmest period is also the wettest according to dDwax, which is further supported by GDGT and alkane distributions, and d13C values indicating aquatic biomass production. 3) At 3.2 ka BP, the climate abruptly deteriorated into colder and drier conditions and re-intensified erosion. Surprisingly, slope wash events resulting in input of coarse detrital material into the core were most frequent during the dry periods. We suggest that this is related to a more variable hydroclimate with droughts and episodic heavy rains, likely associated with ENSO variability, causing increased erosion during the Early and Late Holocene.