Abstract

Abstract. Most northern peatlands developed during the Holocene, sequestering large amounts of carbon in terrestrial ecosystems. However, recent syntheses have highlighted the gaps in our understanding of peatland carbon accumulation. Assessments of the long-term carbon accumulation rate and possible warming-driven changes in these accumulation rates can therefore benefit from process-based modelling studies. We employed an individual-based dynamic global ecosystem model with dynamic peatland and permafrost functionalities and patch-based vegetation dynamics to quantify long-term carbon accumulation rates and to assess the effects of historical and projected climate change on peatland carbon balances across the pan-Arctic region. Our results are broadly consistent with published regional and global carbon accumulation estimates. A majority of modelled peatland sites in Scandinavia, Europe, Russia and central and eastern Canada change from carbon sinks through the Holocene to potential carbon sources in the coming century. In contrast, the carbon sink capacity of modelled sites in Siberia, far eastern Russia, Alaska and western and northern Canada was predicted to increase in the coming century. The greatest changes were evident in eastern Siberia, north-western Canada and in Alaska, where peat production hampered by permafrost and low productivity due the cold climate in these regions in the past was simulated to increase greatly due to warming, a wetter climate and higher CO2 levels by the year 2100. In contrast, our model predicts that sites that are expected to experience reduced precipitation rates and are currently permafrost free will lose more carbon in the future.

Highlights

  • The majority of the northern peatlands developed during the Holocene ca. 8–12 thousand years ago after the deglaciation of the circum-Arctic region (MacDonald et al, 2006)

  • Zones A and B covering the Scandinavian and European regions had high carbon accumulation rate (CAR) in the beginning of the Holocene, which declined through the Holocene, while Zone E covering eastern Siberia displays a peak suggesting an accelerated rate of C accumulation by the year 1900

  • Our model, which among large-scale models of high-latitude peatlands uniquely accounts for feedbacks between hydrology, peat properties, permafrost and dynamics of vegetation across a heterogeneous peatland landscape, is able to reproduce broad, observed patterns of peatland C and permafrost dynamics across the pan-Arctic region

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Summary

Introduction

The majority of the northern peatlands developed during the Holocene ca. 8–12 thousand years (kyr) ago after the deglaciation of the circum-Arctic region (MacDonald et al, 2006). Peatlands share many characteristics with upland mineral soils and non-peat wetland ecosystems They constitute a unique ecosystem type with many special characteristics, such as a shallow water table depth, C-rich soils, a unique vegetation cover dominated by bryophytes (hereinafter referred to as “mosses”), spatial heterogeneity, anaerobic biogeochemistry and permafrost in many regions. Due to their high C density and the sensitivity of their C exchange with the atmosphere to temperature changes, these systems are an important component in the global C cycle and the coupled Earth system (MacDonald et al, 2006). Considerable effort has been made to incorporate peatland accumulation processes into models with the purpose of understanding the role of peatlands in sequestering C, thereby lowering the radiative forcing of past climates

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