Long-term Response of Peatland Carbon Exchange to Climatic Changes in the Hudson Bay Lowlands

Northern peatlands have been a persistent net sink of atmospheric carbon (C) due to the greater rates of gross primary production (GPP) compared to ecosystem respiration (ER). Global warming has raised concerns about the C sink strength of northern environments. In the vast peatlands of the Hudson Bay Lowlands (HBL) region of Canada, warming-induced changes in sea ice dynamics over the Bay have altered its advective influence on the adjacent lowlands. Despite our knowledge of the short-term C exchange in these peatlands, there remain uncertainties in the long-term combined response of GPP and ER to climate change. In this study, the satellite data-driven Vegetation Photosynthesis and Respiration Model (VPRM) was employed to investigate the response of peatland GPP, ER, and net ecosystem exchange (NEE) to temperature and moisture changes. The results show contrasting net CO2 exchange at the two peatland sites over the last 20 years, with the fen acting as a net C source (+24 g C m-2) to the atmosphere and the bog serving as a net C sink (-130 g C m-2). There is ample evidence that a warmer and wetter climate enhanced GPP more than ER, while cooler temperatures weakened the peatland net C sink, regardless of the moisture conditions. Additionally, the advective influence of Hudson Bay on the lowlands produced markedly different C dynamics between offshore and onshore winds, with higher respiration rates (12%–26%) during offshore winds. We discuss the implications for peatland C balance under more frequent onshore winds in the region.