Inconsistent Response of Arctic Permafrost Peatland Carbon Accumulation to Warm Climate Phases

• Published in: Global biogeochemical cycles 2018-10, Vol.32 (10), p.1605-1620
• Main Authors: Zhang, H., Gallego‐Sala, A. V., Amesbury, M. J., Charman, D. J., Piilo, S. R., Väliranta, M. M.
• Format: Article
• Language: English
• Subjects: Accumulation; Atmospheric models; Carbon; carbon accumulation; Climate change; Cold climates; Computer simulation; Deglaciation; Environmental factors; Future climates; Holocene; Hydrology; Ice ages; Little Ice Age; Meltwater; Modelling; Peat; peat decay modeling; Peatlands; Permafrost; permafrost peatlands; Regression analysis; Stocks; Warm climates
• ISSN: 0886-6236; 1944-9224
• DOI: 10.1029/2018GB005980

Northern peatlands have accumulated large carbon (C) stocks since the last deglaciation and during past millennia they have acted as important atmospheric C sinks. However, it is still poorly understood how northern peatlands in general and Arctic permafrost peatlands in particular will respond to future climate change. In this study, we present C accumulation reconstructions derived from 14 peat cores from four permafrost peatlands in northeast European Russia and Finnish Lapland. The main focus is on warm climate phases. We used regression analyses to test the importance of different environmental variables such as summer temperature, hydrology, and vegetation as drivers for nonautogenic C accumulation. We used modeling approaches to simulate potential decomposition patterns. The data show that our study sites have been persistent mid‐ to late‐Holocene C sinks with an average accumulation rate of 10.80–32.40 g C m−2 year−1. The warmer climate phase during the Holocene Thermal Maximum stimulated faster apparent C accumulation rates while the Medieval Climate Anomaly did not. Moreover, during the Little Ice Age, apparent C accumulation rates were controlled more by other factors than by cold climate per se. Although we could not identify any significant environmental factor that drove C accumulation, our data show that recent warming has increased C accumulation in some permafrost peatland sites. However, the synchronous slight decrease of C accumulation in other sites may be an alternative response of these peatlands to warming in the future. This would lead to a decrease in the C sequestration ability of permafrost peatlands overall. Key Points Carbon accumulation in Arctic permafrost peatlands responds inconsistently to warm climate phases Recent warming is reflected not only as increasing but also as decreasing in carbon accumulation Permafrost peatlands are creating a negative feedback to climate warming but have a probable future scenario to turn to a positive feedback