Holocene environmental changes in northern Mongolia inferred from diatom and pollen records of peat sediment

The Holocene paleoenvironment in Nur sphagnum bog, northern Mongolia, was reconstructed by diatom, pollen analysis and measurement of chemical properties on a 3.7 m long peat boring sample. Development processes of peatland are well reflected in these multiproxy records, showing that peat accumulation started as early as 9 ka cal BP, and the present acidic peat bog was established no later than 6 ka cal BP. Synchronous trends in diatom and pollen assemblages revealed wetter climate in the early Holocene and extensive drought in the mid-late Holocene centered at 5900–2800 cal BP as a result of temperature increase and low precipitation. Periods of shifts in proxy data were potentially correlated with other studies in not only Mongolia and Siberia, but also the North Atlantic Ocean, and the climatic periods at 8.4 and 2.8 ka cal BP were highly significant. However, responses to climate changes seem regionally varied in time and strength, demonstrating that local differences in vegetation and orography greatly influence the balance of precipitation and evapotranspiration. Climate changes that coincided in time with the Medieval Climate Anomaly and Little Ice Age were observed as wetter (1200–980 cal BP) and drier (370–240 cal BP) conditions, probably caused by meridional shifts of westerlies.