Widespread global peatland establishment and persistence over the last 130,000 y

Abstract

Glacial-interglacial variations in CO₂ and methane in polar ice cores have been attributed, in part, to changes in global wetland extent, but the wetland distribution before the Last Glacial Maximum (LGM, 21 ka to 18 ka) remains virtually unknown. We present a study of global peatland extent and carbon (C) stocks through the last glacial cycle (130 ka to present) using a newly compiled database of 1,063 detailed stratigraphic records of peat deposits buried by mineral sediments, as well as a global peatland model. Quantitative agreement between modeling and observations shows extensive peat accumulation before the LGM in northern latitudes (>40°N), particularly during warmer periods including the last interglacial (130 ka to 116 ka, MIS 5e) and the interstadial (57 ka to 29 ka, MIS 3). During cooling periods of glacial advance and permafrost formation, the burial of northern peatlands by glaciers and mineral sediments decreased active peatland extent, thickness, and modeled C stocks by 70 to 90% from warmer times. Tropical peatland extent and C stocks show little temporal variation throughout the study period. While the increased burial of northern peats was correlated with cooling periods, the burial of tropical peat was predominately driven by changes in sea level and regional hydrology. Peat burial by mineral sediments represents a mechanism for long-term terrestrial C storage in the Earth system. These results show that northern peatlands accumulate significant C stocks during warmer times, indicating their potential for C sequestration during the warming Anthropocene.

Keywords: Quaternary; carbon; carbon burial; methane; peatlands.

Fig. 1.

Locations of buried peat and present-day peatland sites; buried peat profiles from the LGM (18 ka) and before (orange circles), post-LGM (yellow circles), and profiles without chronological control (black crosses), and basal ages from present-day peatlands (purple circles). North American/Greenland and Scandinavian ice sheet extents are shown by white area with dashed border (44), exposed continental shelf areas during the LGM (yellow) are based on Etopo DEM + Bathymetry using a −125-m sea level (45). Overlapping crosses and circles indicate multiple profiles with and without chronological control.

Fig. 2.

Climate boundary conditions and peat formation records for northern (Nor.; >40°N) and tropical (Trop.; 30°N to 30°S) peatlands for the last 130 ka. At the top are corresponding names for chronostratigraphic units used in the text, including the Holocene (HOL). (A) LR04 δ¹⁸O stack (38); (B) simulated mean annual temperature for global land areas (39); (C) simulated annual precipitation for global land areas (39); (D) number of active northern peat deposits now buried (count); (E) northern peatland initiation (count); (F) number of active peat deposits (now buried) in tropical regions (count); and (G) tropical peatland initiation (count).