Jenny K. Sjöström

Bolin Centre for Climate Research

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Malin E. Kylander

Stockholm University

Antonio Martı́nez Cortizas

Universidade de Santiago de Compostela

Richard Bindler

Umeå University

Eleonor E. Ryberg

Bolin Centre for Climate Research

Frederik Schenk

Bolin Centre for Climate Research

Sophia V. Hansson

Institut de Recherche pour le Développement

Noemí Silva-Sánchez

Instituto de Ciencias del Patrimonio

Joeri Kaal

Consejo Superior de Investigaciones Científicas

Rienk H. Smittenberg

Stockholm University

Richard Gyllencreutz

Stockholm University

Cooperative Institutions

Stockholm University

Bolin Centre for Climate Research

Consejo Superior de Investigaciones Científicas

Universidade de Santiago de Compostela

University of Liverpool

Centre National de la Recherche Scientifique

Swedish University of Agricultural Sciences

Umeå University

University of Bergen

Imperial College London

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Disentangling seasonal and annual precipitation signals in the tropics over the Holocene: insights from δD, alkanes and GDGTs

Petter Hällberg Malin E. Kylander Frederik Schenk Joan Villanueva Nina Davtian

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.

Seasonality

Paleoclimatology

East Asian Monsoon

Tropical monsoon climate

10.5194/egusphere-egu24-18355

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Mineral dust as a driver of carbon accumulation in northern latitudes

Scientific Reports (2018)

Malin E. Kylander Antonio Martı́nez Cortizas Richard Bindler Joeri Kaal Jenny K. Sjöström

Abstract Peatlands in northern latitudes sequester one third of the world’s soil organic carbon. Mineral dusts can affect the primary productivity of terrestrial systems through nutrient transport but this process has not yet been documented in these peat-rich regions. Here we analysed organic and inorganic fractions of an 8900-year-old sequence from Store Mosse (the “Great Bog”) in southern Sweden. Between 5420 and 4550 cal yr BP, we observe a seven-fold increase in net peat-accumulation rates corresponding to a maximum carbon-burial rate of 150 g C m −2 yr −1 – more than six times the global average. This high peat accumulation event occurs in parallel with a distinct change in the character of the dust deposited on the bog, which moves from being dominated by clay minerals to less weathered, phosphate and feldspar minerals. We hypothesize that this shift boosted nutrient input to the bog and stimulated ecosystem productivity. This study shows that diffuse sources and dust dynamics in northern temperate latitudes, often overlooked by the dust community in favour of arid and semi-arid regions, can be important drivers of peatland carbon accumulation and by extension, global climate, warranting further consideration in predictions of future climate variability.

Carbon fibers

Soil carbon

10.1038/s41598-018-25162-9

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Citations (42)

Storm chasing: Tracking Holocene storminess in southern Sweden using mineral proxies from inland and coastal peat bogs

Quaternary Science Reviews (2022)

Malin E. Kylander Antonio Martı́nez Cortizas Jenny K. Sjöström Jenny Gåling Richard Gyllencreutz

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.

Ombrotrophic

Extratropical cyclone

Winter storm

10.1016/j.quascirev.2022.107854

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Investigating the Mineral Composition of Peat by Combining FTIR-ATR and Multivariate Analysis

Minerals (2021)

Antonio Martı́nez Cortizas Lourdes López Merino Noemí Silva-Sánchez Jenny K. Sjöström Malin E. Kylander

The mineral content of peat has received little attention until the last few decades, when peat cores have been increasingly used to study past dust deposition. Paleodust deposition is commonly reconstructed through elemental datasets, which are used to infer deposition rates, storminess patterns, mineral composition, source identification, and fertilization effects. To date, only a few studies have directly analyzed the mineralogy (by XRD and SEM) and particle size of peat mineral matter, and the conducted studies have usually been constrained by the need to remove a large amount of organic matter, which risks altering the mineral component. One alternative is to use quick, nondestructive techniques, such as FTIR-ATR, that require little sample preparation. In this study, we analyzed by FTIR-ATR both the bulk peat and ash fractions of a sequence taken in a minerogenic mire that covered a wide inorganic matter content range (6%–57%). Aided by principal component analysis on transposed IR spectral data, we were able to identify the main minerals in bulk peat and ash, quartz, mica (likely muscovite), K feldspar (likely microcline), and plagioclase (likely anorthite), which are consistent with the local geology of the mire catchment. Changes in mineral composition during the last ca. 2800 years were coeval with previously reconstructed environmental changes using the same core. Our results suggest that FTIR-ATR has great potential to investigate peat mineral matter and the processes that drive its compositional change.

Mire

Microcline

Deposition

Eluvium

10.3390/min11101084

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Citations (17)

9000 years of changes in peat organic matter composition in Store Mosse (Sweden) traced using FTIR‐ATR

Boreas (2021)

Antonio Martı́nez Cortizas Jenny K. Sjöström Eleonor E. Ryberg Malin E. Kylander Joeri Kaal

Store Mosse (the ‘Great Bog’ in Swedish) is one of the most extensive bog complexes in southern Sweden (~77 km 2 ), where pioneering palaeoenvironmental research has been carried out since the early 20th century. This includes, for example, vegetation changes, carbon and nitrogen dynamics, peat decomposition, atmospheric metal pollution, mineral dust deposition, dendrochronology, and tephrochronology. Even though organic matter (OM) represents the bulk of the peat mass and its compositional change has the potential to provide crucial ecological information on bog responses to environmental factors, peat OM molecular composition has not been addressed in detail. Here, a 568‐cm‐deep peat sequence was studied at high resolution, by attenuated reflectance Fourier‐transform infrared spectroscopy (FTIR‐ATR) in the mid‐infrared region (4000–400 cm –1 ). Principal components analysis was performed on selected absorbances and change‐point modelling was applied to the records to determine the timing of changes. Four components accounted for peat composition: (i) depletion/accumulation of labile (i.e. carbohydrates) and recalcitrant (i.e. lignin and other aromatics, aliphatics, organic acids and some N compounds) compounds, due to peat decomposition; (ii) variations in N compounds and carbohydrates; (iii) residual variation of lignin and organic acids; and (iv) residual variation of aliphatic structures. Peat decomposition showed two main patterns: a long‐term trend highly correlated to peat age ( r = 0.87), and a short‐term trend, which showed five main phases of increased decomposition (at ~8.4–8.1, ~7.0–5.6, ~3.5–3.1, ~2.7–2.1 and ~1.6–1.3 ka) – mostly corresponding to drier climate and its effect on bog hydrology. The high peat accumulation event (~5.6–3.9 ka), described in earlier studies, is characterized by the lowest degree of peat decomposition of the whole record. Given that FTIR‐ATR is a quick, non‐destructive, cost‐effective technique, our results indicate that it can be applied in a systematic way (including multicore studies) to peat research and provide relevant information on the evolution of peatlands.

10.1111/bor.12527

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Citations (26)

Late Holocene palaeoenvironmental reconstruction from Mpumalanga Province (South Africa) inferred from geochemical and biogenic proxies

Review of Palaeobotany and Palynology (2017)

Jenny K. Sjöström Elin Norström Jan Risberg Maria H. Schoeman

Phytolith

Biome

10.1016/j.revpalbo.2017.06.011

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Citations (11)

Reconstruction of Holocene atmospheric mineral dust deposition from raised peat bogs in south–central Sweden

Jenny K. Sjöström

Atmospheric mineral dust plays a dynamic role in the climate system acting both as a forcing and a feedback mechanism. To date, the majority of paleodust studies have been conducted on marine sedim ...

Mineral dust

Deposition

Forcing (mathematics)

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Postglacial peatland vegetation succession in Store Mosse bog, south‐central Sweden: An exploration of factors driving species change

Boreas (2022)

Eleonor E. Ryberg Minna Väliranta Antonio Martı́nez Cortizas Johan Ehrlén Jenny K. Sjöström

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.

Sphagnum

Mire

Macrofossil

Testate amoebae

Ombrotrophic

10.1111/bor.12580

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Citations (12)

Complex evolution of Holocene hydroclimate, fire and vegetation revealed by molecular, minerogenic and biogenic proxies, Marais Geluk wetland, eastern Free State, South Africa

Quaternary Science Reviews (2023)

Jenny K. Sjöström Antonio Martı́nez Cortizas Are Nylund Amanda Hardman Joeri Kaal

The Holocene climate history of Southern Africa remains inconclusive despite the increasing number of proxy records from the region. This might be related to the diversity of proxy records, how the proxies are interpreted, or that proxies may respond to more than one forcing (e.g. hydroclimate, fire, temperature.). Here, a 175-cm peat sequence from Free State, South Africa (28°17′53″S, 29°25′10.9″E), was analyzed using a comprehensive set of novel and conventional proxies, including isotopic (δ13C), elemental (CS-XRF), mineral (pXRD), molecular (FTIR-ATR and pyrolysis-GC-MS), grain size (Malvern 3000) and GSSC phytolith composition. The chronology was constructed through AMS radiocarbon dating (n = 7). The early Holocene (10,380–7000 cal yr BP) was characterized by an initial wet phase, followed by relative dryness, at least seasonally, evidenced by slow accumulation rates, low organic content and dominance of terrestrial vegetation in the organic matter matrix. From 7000 cal yr BP, decreasing temperatures, as evidenced in regional climate reconstructions, were associated at Marias Geluk with higher biogenic silica and organic matter content and an increase of moisture-adapted grasses, indicating increasingly mesic conditions. This trend was amplified after 6000 cal yr BP, co-occurring with a southward displacement of the ITCZ. Complex proxy dynamics were observed between 4300 and 2180 cal yr BP, with bulk organic proxies indicating a drier environment (lower carbon content, slow accumulation rates, enriched δ13C values) but the phytolith record pointing towards relatively mesic conditions. The period was also associated with increased fire frequency, that also reached the local wetland. We suggest that the period was associated with seasonally mesic conditions together with increased fire incidence, which affected some of the organic proxies. Increased fire activity was also recorded in the region, while the hydroclimatic indications differed. The last 2000 years, during which human activity is known to have increased in the region, was characterized by lower fire incidence and variable, but relatively moist, conditions. The hydroclimatic inferences for the last 2000 years are in line with previous studies from the region, but additional studies are needed to decipher if the decline in fire incidence was associated to climate forcings, human activities, or a combination of both. The multiproxy approach applied here - in particular the inclusion of FTIR-ATR and pyrolysis GC-MS - revealed a complex interplay between vegetation dynamics, hydrology and paleofire variability. This study confirms that relatively small Holocene temperature variations (compared to northern higher latitudes) were associated with major hydrological variability at Marais Geluk, and reinforces concerns from earlier studies that the hydroclimate of the region is vulnerable to climate change. The result s also show that the southward displacement of the ITCZ, and associated tropical air masses, likely had significant effects on regional hydrology and fire incidence.

Biogenic silica

Phytolith

Paleoclimatology

10.1016/j.quascirev.2023.108216

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Mid-Holocene mineral dust deposition in raised bogs in southern Sweden : Processes and links

Jenny K. Sjöström

Atmospheric mineral dust is a key component of the climate system, which affects insolation, brings nutrients to marine and terrestrial ecosystems, and acts as a cloud condensation nuclei. To recon ...

Mineral dust

Cloud condensation nuclei

Deposition

Source

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Citations (2)