EGU21-10942
https://doi.org/10.5194/egusphere-egu21-10942
EGU General Assembly 2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Atmospheric circulation, hydroclimate change, and peat accumulation over the last 250 years inferred from a Sphagnum peatland in the southern Greater Khingan Mountains of Northeast China 

Zuo Wang1 and Zicheng Yu1,2
Zuo Wang and Zicheng Yu
  • 1Institute for Peat and Mire Research, Northeast Normal University, Changchun, Jilin 130024, PR China
  • 2Department of Earth and Environmental Sciences, Lehigh University, Bethlehem, PA 18015, USA

Northeast China—located near the northern limit of the influence by the East Asian summer monsoon—receives most moisture through the westerly airflow, but variations in moisture contributions from the Yellow Sea in the western Pacific Ocean determine its hydroclimate during summer monsoon season. The proportion of moisture from the Yellow Sea is strongly modulated by the location and intensity of the Western Pacific Subtropical High (WPSH). However, it is still unclear how sensitive regional hydroclimate to WPSH-modulated change in moisture sources and its impact on peatland carbon accumulation. Here, we used macrofossil data and paired δ13C and δ18O isotope analysis of Sphagnum moss cellulose from a well-dated bog from a steep mountain slope in the Greater Khingan Mountains (~47˚N) to reconstruct peatland moisture changes and elucidate past shifts in moisture sources. δ13C values reflect peatland surface moisture, as dry conditions with less water film effects would increase isotopic discrimination against 13C and result in lower δ13C values. Our results from a 250-year peat record show a decrease of ~3‰ in δ13C from -25 to -28‰—with corresponding increase in dry-adapted moss Polytrichum—suggesting a drying trend since about 1980 AD. Also, the down-core δ18O and δ13C data show a positive correlation (r = 0.65, p < 0.001), in contrast with evaporative enrichment of δ18O being the dominant effect. We argue that δ18O values reflect the input of moisture derived from the Yellow Sea—that has higher δ18O values than that from the westerlies—as modulated by the WPSH. When the WPSH extends westward, it blocks moisture transport from the Yellow Sea to North China, causing low δ18O values in summer precipitation, dry conditions, and negative shifts in δ13C, and vice versa. Furthermore, carbon accumulation rates show a major decrease after the 1980s—despite that more recent peat tends to have higher apparent accumulation rates—suggesting a sensitive response of this steep-slope mountain peatland to shift in regional hydroclimate in monsoon-margin region of Northeast China.

How to cite: Wang, Z. and Yu, Z.: Atmospheric circulation, hydroclimate change, and peat accumulation over the last 250 years inferred from a Sphagnum peatland in the southern Greater Khingan Mountains of Northeast China , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10942, https://doi.org/10.5194/egusphere-egu21-10942, 2021.

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