Differential Response of Alaska Peatlands to Climate Changes of the Last Millennium

Abstract Northern peatlands in boreal and subarctic regions store about 500 Gt of carbon (C). Understanding the fate of this large C pool under a warmer climate is important, as temperatures in northern latitudes have increased quicker than the global averages over the past 100 years. Both regional climate (e.g., temperature and precipitation) and local factors (e.g., topography) influence peatland response to climate changes. To better understand peatland response to climate changes, paleoecological techniques were used to study the C accumulation and paleohydrololgy of peatlands in different Alaskan climate regions. In addition, local-scale factors were studied through comparison of two nearby peatlands in different surficial geologic settings within the Southcentral Alaska climate region. Peatland responses to relatively well-documented climate changes over the last 1100 years, such as the Medieval Climate Anomaly (MCA) at ~1000-600 and Little Ice Age (LIA) at ~600-200 cal yr BP, were analyzed. Regional-scale results indicate that peatlands in relatively warmer and wetter Southeast Alaska accumulated the most peat over the last millennium. Average apparent peatland C accumulation rates in all regions were greatest during the warmer MCA than the cooler LIA, suggesting a possible negative C cycle feedback to climate change because peatlands may sequestrate more atmospheric C under a warmer climate, reducing the greenhouse effect. However, results also indicate that local-scale factors, like surficial geology, can lead to a heterogeneous response of peatlands to climate change, even within the same region, which has important implications for C cycling and peat-based paleoclimate studies. A better understanding of local-scale controls is necessary to help account for some of the unexplained variability present in studies of northern peatland response to climate changes.