Research project: CryoHyd – changes in the cryosphere and its impact on hydrology

Part of the project team on field work in Mongolia, September 2022. Picture: L. Menzel

The Earth's cryosphere includes the regions covered at least temporarily by ice and snow and the territories underlain by permafrost. Changes in the cryosphere caused by global warming are expected to alter the hydrological cycle, with consequences to freshwater availability for humans and ecosystems. In our research group, we are investigating how degradation of permafrost and change in snow cover duration affect hydrology in the greater region of southern Siberia and Mongolia. In the north of Mongolia, in the Selenga river basin, we have been conducting field research in the headwater rivers of the Khentii Mountains for more than ten years. At the same time, and based on our measurements in the Khentii Mountains, we are analysing the causes for some drastic changes in the hydrology of Siberian rivers such as the upper Lena or the Aldan.

Digging a permafrost observation profile is costly and physically demanding. The remote study re-gion in the north of Mongolia can only be reached on horseback and on foot, thus no machines are available for the work. Picture: L. Menzel

In the Khentii Mountains, we observe a sharp decline in permafrost, i.e. a continuing lowering of the permafrost table, as well as lateral degradation, not only in the areas affected by human-induced disturbances (mostly forest fire). The thickness of the active layer also seems to continue to increase under the pristine taiga forests in the higher altitudes of the mountains. The possible impacts on the hydrology of the region have already been described in several articles of our working group, see e.g. Kopp et al. (2015), but the changes are complex in nature and require further investigation.

Installation of soil moisture and temperature sensors in a permafrost monitoring pit. The pits are subsequently backfilled with soil. Picture: G. Yadamsuren

On the large scale, we combine data assimilation, cross-correlation analysis, and simulation techniques to examine the driving mechanisms of historical hydrological changes at different temporal scales. For example, we observe a remarkable increasing trend in runoff in the Aldan catchment (years 1954-2013: 4.4 km³/10 years, p≤0.05), which is underlain by continuous permafrost, although precipitation shows no significant changes over the study period. We can also recognise that warming-induced permafrost degradation has led to strong regime shifts in river runoff of the investigated basins. Snow cover has a critical impact on permafrost stability, thus, snow is one of the variables that we include in our observations and analyses. Our investigations in southern Siberia show that although snow depths have decreased, a presumed shortening of the snow cover duration has not been proven so far.

Results of an analysis on the change of air temperature and discharge in the Aldan, a tributary of the Lena River in Siberia. The increasing trends in both variables are statistically highly significant. From Han & Menzel (2022), modified.

This research is one of our long-term projects, as only continued observation and analysis of the processes and dynamics in the cryosphere and their interactions with the hydrosphere can lead to reliable knowledge.

Our cooperation partners

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

Selected poster presentations

• Han & Menzel (EGU, 2021): Terrestrial water variability in Southern Siberia driven by permafrost degradation
• Zhao & Menzel (SnowHydro, 2022): Variability of snow cover over Southern Siberia during 1982-2019

Press release

• Wie sich der Klimawandel im Norden auswirkt, RNZ Dezember 2022

Literatur

• Wimmer, F., Schlaffer, S., aus der Beek, T. & Menzel, L. (2009): Distributed modelling of climate change impacts on snow sublimation in Northern Mongolia, Adv. Geosci., 21, 117–124, https://doi.org/10.5194/adgeo-21-117-2009
• Törnros, T., Menzel, L. (2010): Heading for knowledge in a data scarce river basin: Kharaa, Mongo-lia. Status and Perspectives of Hydrology in Small Basins. Proceedings of the Workshop held at Gos-lar-Hahnenklee, Germany. Vol. 30. 2010.
• Minderlein, S., Menzel, L. (2015): Evapotranspiration and energy balance dynamics of a semi-arid mountainous steppe and shrubland site in Northern Mongolia. Environ Earth Sci 73, 593–609. https://doi.org/10.1007/s12665-014-3335-1
• Menzel, L. (2016): Eco-hydrological investigations in the Khentii mountains, Northern Mongolia. Mountain Meridian, 8, 14–15, http://issuu.com/mountainresearchinitiative/docs/news8
• Kopp, B., Minderlein, S. & Menzel, L. (2014): Soil moisture dynamics in a mountainous headwater area in the discontinuous permafrost zone of northern Mongolia. Arctic, Antarctic and Alpine Re-search, 46(2), 459–470, https://doi.org/10.1657/1938-4246-46.2.459
• Lange, J., Kopp, B., Bents, M. & Menzel, L. (2014): Tracing variability of run-off generation in mountainous permafrost of semi-arid north-eastern Mongolia. Hydrological Processes, https://doi.org/10.1002/hyp.10218
• Kopp, B. J., Lange, J. & Menzel, L. (2017): Effects of wildfire on runoff generating processes in northern Mongolia. Reg Environ Change 17, 1951–1963. https://doi.org/10.1007/s10113-016-0962-y
• Munkhjargal, M., Groos, S., Pan, C. G., Yadamsuren, G., Jambaljav, Y. & Menzel, L. (2019): Multi-source based spatio-temporal distribution of snow in a semi-arid headwater catchment of Northern Mongolia. Geosciences, 9, 53, https://doi.org/10.3390/geosciences9010053
• Munkhjargal, M. & Menzel, L. (2019): Estimating daily average net radiation in Northern Mongolia. Geografiska Annaler: Series A, Physical Geography, https://doi.org/10.1080/04353676.2019.1583498
• Munkhjargal, M., Yadamsuren, G., Jambaljav, Y. & Menzel, L. (2020): The combination of wildfire and changing climate triggers permafrost degradation in the Khentii Mountains, Northern Mongolia. Atmosphere, 11, 155, https://doi.org/10.3390/atmos11020155
• Munkhjargal, M., Yadamsuren, G., Jambaljav, Y. & Menzel, L. (2020): Ground surface temperature variability and permafrost distribution over mountainous terrain in northern Mongolia. Arctic, Ant-arctic and Alpine Research, 52:1, 13-26, https://doi.org/10.1080/15230430.2019.1704347
• Han, L. & Menzel, L. (2022): Hydrological variability in southern Siberia and the role of permafrost degradation. Journal of Hydrology, 604, https://doi.org/10.1016/j.jhydrol.2021.127203