Testing the climate sensitivity of peat-based paleoclimate reconstructions in mid-continental North America

The sensitivity of peatland water-table depth reconstructions to past hydroclimate variability was assessed by comparing Pb-210-dated, testate amoeba-based reconstructions of water-table depth with instrumental records of temperature, precipitation, and Palmer Drought Severity Index (PDSI). Comparisons were made for the past century at five sites in the western Great Lakes region of North America. The primary objectives were (1) to assess the relative influence of temperature and precipitation on proxy records from these systems, (2) compare an integrated index of past moisture variability, PDSI, to records of peatland surface-moisture, and (3) compare the relative climate sensitivity of paleohydrological records from a raised bog and two types of kettle peatland, including those with and without floating peat mats. Results indicated that the raised bog surface-moisture reconstructions were most strongly correlated with PDSI, with precipitation variability more important than temperature variability. Proxy records from two non-floating kettle peatlands were also correlated with PDSI, although the importance of precipitation and temperature varied between the two sites. Records from floating mats were not correlated with instrumental climate records, although patterns suggest that additional research is needed to assess the sensitivity of these systems to high-magnitude or prolonged drought events. Although the relative importance of precipitation and temperature in controlling peatland surface-moisture conditions may vary in space and time, consistent correlations with PDSI indicate that peatland archives are well suited for studies of past drought variability and should be particularly valuable in humid regions at mid-to-high latitudes where moisture-sensitive records are scarce. (C) 2009 Elsevier Ltd. All rights reserved.