Hydrology CryoHyd

The Earth’s cryosphere includes regions that are covered by ice and snow, at least seasonally, as well as areas with underlying permafrost. It is reasonable to assume that changes in the cryosphere caused by global warming will alter the water cycle, which will affect the availability of freshwater for people and ecosystems. In our research group, we investigate how permafrost degradation and changes in snow cover duration affect hydrology in the greater region of Southern Siberia and Mongolia. In northern Mongolia, in the Selenga River basin, we have been conducting field research for more than ten years in the headwaters of the Khentii Mountains. In parallel with this work, and based on our measurements in the Khentii Mountains, we are analyzing the causes of the often drastic changes in the hydrology of Siberian rivers such as the upper Lena and the Aldan.

In the Khentii Mountains, we are observing a significant decline in permafrost – that is, a continuous lowering of the permafrost table and lateral degradation of the permafrost – not only in areas affected by wildfires. Even beneath the undisturbed taiga forests at higher elevations in the mountains, the thickness of the thaw layer appears to be continuing to increase. Our research group has described the potential impacts on the region’s hydrology in several articles (see, e.g., Kopp et al. 2015); however, these changes are complex in nature and require further investigation.

On a large spatial scale, we combine techniques of data assimilation, cross-correlation analysis, and hydrological modeling to investigate the drivers of historical hydrological changes across various temporal scales. For example, we have observed a significant increase in runoff in the Aldan watershed (1954–2013: 4.4 km³/10 years, p ≤ 0.05), which is underlain by continuous permafrost, even though precipitation did not show any significant changes during the observed period. It has also become evident that permafrost degradation caused by warming has led to major regime shifts in the runoff of the monitored basins. Snow cover has a decisive influence on the stability of permafrost, which is why snow is one of the variables we include in our observations and analyses. Our studies in Southern Siberia have shown that, although snow depths have decreased, a suspected shortening of snow cover duration has not yet been confirmed.

These studies are part of our long-term projects, as only continuous observation and analysis of the processes and dynamics in the cryosphere and their interactions with the hydrosphere can produce reliable findings.

Our collaboration partners:

• Mongolian Academy of Sciences, Institute of Geography (permafrost monitoring)
• Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Institute of Arctic Climate and Environment (large-scale observation and modeling)