Hydrological change in response to climate change and permafrost dynamics in southern Siberia

• Main Author: Han, Li
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: 2022
• Subjects: 550; 550 Earth sciences; permafrost; Siberia
• Online Access: https://archiv.ub.uni-heidelberg.de/volltextserver/31185/; https://archiv.ub.uni-heidelberg.de/volltextserver/31185/1/Thesis_LH.pdf; https://doi.org/10.11588/heidok.00031185; https://nbn-resolving.org/urn:nbn:de:bsz:16-heidok-311856

Changes in the cryosphere caused by global warming are expected to alter the terrestrial hydrological cycle, with inevitable consequences for freshwater availability to humans and ecosystems. In particular, the presence of permafrost influences water fluxes and dynamics in the subsurface system, thus, complicating the hydrologic processes in the permafrost-affected region. However, due to the absence of long-term, large-scale permafrost observations, a systematic understanding of how the warming-related permafrost dynamics may influence the large-scale hydrological processes is not clear yet. This work aims to address this research gap by investigating the hydro-climatic dynamics during 1954-2013 over multiple temporal scales, i.e., 60-year, 30-year, decadal and event scales. The study area is focused on three southern Siberian catchments with diverse ecosystems and permafrost distributions, namely, the semi-arid Selenga featured with sporadic permafrost, the boreal Lena covered by discontinuous permafrost, and the boreal Aldan is underlain by continuous permafrost. Our investigations will help to gain insights into the consequences of permafrost degradation on the terrestrial water availability from a hydrology-permafrost-climate coupling perspective. Due to “seesaw-like” large-scale atmospheric circulations over the Siberian region, we found that precipitation and river runoff resemble periodical natural oscillations between dry and wet states: while Selenga oscillates in a wet-dry-wet-dry pattern from 1954 to 2013, Lena and Aldan oscillate in a dry-wet-dry-wet mode. On top of these oscillations, the precipitation in all the catchments shows negligible long-term (60-yr) trends. However, significant but divergent long-term trends are observed in the river runoff among these catchments that can be related to different permafrost degradation dynamics. The semi-arid Selenga, dominated by lateral permafrost degradation (i.e., decreasing permafrost extent), suffers from severe water loss due to enhanced infiltration ...