Paleodust deposition and peat accumulation rates – Bog size matters

Jenny K Sjöström,Antonio Martínez Cortizas,Sophia V Hansson,Noemí Silva Sánchez,Richard Bindler,Johan Rydberg,Carl-Magnus Mörth,Eleonor E Ryberg,Malin E Kylander

doi:10.1016/j.chemgeo.2020.119795

Abstract

We present a high-resolution peat paleodust and accumulation rate record spanning the last 8300 years from Draftinge Mosse (400 ha), southern Sweden (57°06′27.6”N 13°42′54.1″E). The record was analysed for peat accumulation rates (PAR), elemental concentrations, mineralogy, and plant macrofossil content. Five periods of increased mineral deposition were recorded. The first event occurred between ~6280 and ~5570 cal BP, during the fen to bog transition. This is followed by four atmospheric mineral dust events (DE) which were recorded in the ombrotrophic section of the sequence at (cal BP): ~2200; ~1385–1150; ~830–590, and from ~420 to the present. Statistical analysis and elemental ratios indicated that both the mineralogy and grain size shifted when the system transitioned from fen into bog, showing that the governing transport process shifted with the peatland succession stages. This highlights the importance of identifying peatland succession stages within peat paleodust studies. Following all four DE, increases in PAR were observed, implying a coupling to dust deposition. Comparison of DE and PAR with a paleodust record from Store Mosse, a 20 times larger bog located ca 18 km away (Kylander et al. 2016), showed that both PAR and dust deposition are largely represented by single-core reconstructions, indicating that they are driven by a common climate forcing mechanism. However, higher PAR and dust deposition rates were observed in the more moderately sized Draftinge Mosse, suggesting that the size of the bog is important to consider in peat paleodust studies. Furthermore, the smaller bog responded more rapidly to hydrological changes, indicating that the size of the bog affects its' buffering capacity. Authigenic carbonates, observed here during episodes of rapid peat growth, coincide with changes in REE ratios, indicating that authigenic peat processes potentially cause REE fractionation.

Highlights

Atmospheric mineral dust is an important component of the climate system acting as both a forcing and a feedback mechanism (Albani et al, 2015)
Despite the fact that the cool and wet northern latitudes lack large and distinct dust sources, recent work has established that (1) dust deposition rates vary over time in these regions
Five episodes of increased mineral deposition were recorded at Draftinge Mosse: ~6280–5570, ~2200, ~1385–1150, ~830–590, and from ~420 to the present

Summary

Introduction

Atmospheric mineral dust is an important component of the climate system acting as both a forcing and a feedback mechanism (Albani et al, 2015). Dust particles scatter and absorb incoming radiation, in fluence atmospheric photochemistry, act as cloud condensation nuclei, and fertilize nutrient limited marine Paleodust records help us to understand the natural variability of mineral dusts deposition in time and space and can help fill this knowledge gap. Paleodust studies have increased in number during the last decades but the spatial distribution is still uneven, with marine low-latitude sites more frequently studied compared to the mid- and high-latitude terrestrial regions. In this context, paleodust reconstructions from peatlands offer valuable insights into regional dust dynamics on the continents. Despite the fact that the cool and wet northern latitudes lack large and distinct dust sources, recent work has established that (1) dust deposition rates vary over time in these regions

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