For my PhD project, I focused on the glacial history of Central Asia during the Quaternary. Glaciers respond to changes in climate parameters and their responses are recorded in the landscape. The extreme continental setting and a wide variety of climate zones in Central Asia provide an ideal natural laboratory to study interaction between glaciers and climate. I am reconstructing past glacial extents in southern Siberia, monsoon-influenced mountains of Qilian Shan in China, hyper-arid climates of the Gobi and northern Tibet, and in the stretches of the Kyrgyz Tien Shan.
Field observations and mapping are integral part of my research. The field data is synthesized into the regional-scale map, using remote-sensing techniques in the lab. I use multi-spectral and elevation data, such as from ASTER or LANDSAT (processed in Exelis ENVI, ArcGIS, QGIS). For geochronology, I use different radiometric dating techniques: Cosmic-ray exposure dating (10Be) for glacial boulders, luminescence (OSL, IRSL) dating for sediments, and radiocarbon dating for organics. Finally, the paleoclimate implications of these glacial records can be explained by the numerical modeling of the glacier's mass and surface-energy balance. The overall results of my PhD research are reconsiled into three project described below.
Glaciers in the continental climates of Central Asia
Water resources and agriculture in large regions of Central Asia depend on melt water from the glaciers, many of which are retreating in today’s climate. Some of these glaciers may pose major hazards because they may release outburst floods. In recent years the monitoring of these glaciers has improved thanks to automated stations and repeated satellite imagery. However, we don’t know how much of the glacial changes in these records are due to human-induced climate warming, and this understanding is helpful in predicting future trends. To detect the natural signal, we need to determine the glaciers’ positions in the pre-industrial period, and estimate their natural variability. To address this problem, we selected several glaciers with similar climate conditions in the Altai mountains, Tian Shan, Qilian Shan, Altyn Tagh, and Kunlun, and dated at least one sequence of moraines at each site. The moraine positions determine the relative glacial extents, allowing an estimate of the advance/retreat rate. The natural variability of each glacier can then be numerically modeled (Roe and Baker, 2014). The dataset produced from this project will be a valuable baseline metric for comparing and validating general circulation models. Better understanding of the glaciers’ characteristics in these regions will inform the decision makers to implement the appropriate policies for mitigating the water resources and flood-related risks.
- Batbaatar, J., Gillespie, A.R., Koppes, M., Clark, D.H., Chadwick, O.A., Fink, D., Matmon, A., and Rupper, S., submitted. Spatial pattern of glaciations across the climate-transect of Central Asia.
- Batbaatar, J., Gillespie, A.R., 2015. Marine Oxygen Isotope Stage 3 glaciations in continental-climate regions of Central Asia. INQUA XIX Congress: Quaternary perspectives on climate change, natural hazards and civilization, Nagoya, Japan. July 29, 2015.
- Gillespie, A.R., Batbaatar, J., 2014. Climatic mediation of moisture sources on the southern edge of Siberia. Geological Society of America Abstracts with Programs. Vol. 46, No. 6, p. 798.
- Batbaatar, J., Gillespie, A.R., 2013. Spatial pattern of equilibrium-line altitude in Central Asia.Geological Society of America Abstracts with Programs. Vol. 45, No. 7, p. 261.
Asynchronous glaciations in arid continental climate
The timing and the magnitude of the maximum glacial extents around the world are known to be highly variable (Gillespie and Molnar, 1995). Numerical models (Rupper and Roe, 2008) of Central Asian glaciers have attributed this heterogeneous pattern to differential sensitivity of glaciers to changes in temperature and precipitation. Particularly, in cold, arid regions sublimation can account for more than 50% of the glacier ice loss. These “starving” glaciers are more sensitive to small changes in precipitation, unlike glaciers forming under higher precipitation which are strongly controlled by temperature. To test this hypothesis in the field we sampled moraines of glaciers in the two different climate regions of Mongolia: 1) relatively humid setting (~400 mm/yr) in the central massif, the Hangai ranges; 2) Arid setting (less than 200 mm/yr) in the Gobi-Altai ranges. A single small ice cap remains in the Hangai ranges now, but glaciers there advanced more than 30 km during the global Last Glacial Maximum (LGM: ~20 ka). In the Gobi, however, we found an evidence of local LGM advance that occurred during early Holocene, ~8–7 ka, a pluvial period in Mongolia. The preliminary calculations of the surface-energy balance suggest that despite the cold temperatures of the LGM sunlight could have provided enough energy to sublime up to ~80 mm/yr of ice in the arid Gobi mountains. During the early Holocene the increased precipitation there was sufficient enough to grow glaciers on the high peaks. Our result implicates that reconstruction of paleoclimate from glacial records in arid regions should be taken carefully. Hannah Hickey, from UW News, nicely summarized our results in a normal human language in her aricle Glaciers in Mongolia’s Gobi Desert actually shrank during the last ice age.
Batbaatar, J., Gillespie, A.R., Fink, D., Matmon, A., Fujioka, T., 2018. Asynchronous glaciations in arid continental climate. Quaternary Science Reviews, v. 182, p. 1–19. (pdf, supplementary 1, supplementary 2)
Batbaatar, J., Gillespie, A.R., Fink, D., Matmon, A., Lai, ZP., 2017. Relative equilibrium-line altitude as an indicator of glacier sensitivity to temperature and precipitation. Geological Society of America, Annual Meeting, Seattle, WA, October 22–25.
Batbaatar, J., Gillespie, A.R., 2012. Equilibrium-line altitudes in cold hyperarid settings. American Geophysical Union, Fall Meeting. San Francisco, CA, December 3–7 (abstract #C43E-06).
Catastrophic floods of the Maly Yenisei river, Siberia
The third largest flood on Earth, measured by its estimated peak discharge, originated from Darhad basin in northern Mongolia, the headwaters of the Yenisei river. The outlet glaciers from the East Sayan ice field (see image above) blocked the exit from the basin and impounded up to 290 m deep lake. The lake sediments exposed on the surface dated to ~50 ka (Gillespie et al., 2008), allowing a possibility that the glaciers were not big enough during the Last Glacial Maximum ~20 ka. We extracted lake sediments from a 92 m deep borehole and recovered the deep lake sediments from ~20 ka, which also supported by our cosmic-ray exposure dating of the end moraine of the blocking glacier. Our newly established glacial chronology in the adjacent areas show that the ice fields of the East Sayan and the Hangai massif were large enough to source thick outlet glaciers during the LGM.
Batbaatar, J., and Gillespie, A.R., 2016. Outburst floods of the Maly Yenisei. Part I. International Geology Review, v. 58, no. 14, p. 1723–1752. (pdf, supplementary)
Batbaatar, J., and Gillespie, A.R., 2016. Outburst floods of the Maly Yenisei. Part II – new age constraints from Darhad basin. International Geology Review, v. 58, no. 14, p. 1753–1779. (pdf, supplementary 1, supplementary 2)
Batbaatar, J., Gillespie, A.R., Schreiber, B.C., 2012, Tectonics and environment at the western end of the Baikal rift: Paleolake sediment record from Darhad Basin, northern Mongolia. Geological Society of America Abstracts with Programs, vol., 44, no. 3, p. 56.
Cool projects I helped:
Provenance of the coarse silt fractions of the Chinese Loess Plateau
Rivka Amit (Geological Survey of Israel) demonstrated in this study that the quartz grains in the Gobi dunes are transported in short distances. In this paper, she proposed in this paper that over long time-scales these abraded silts provide the primary source for the massive accumulation of the Chinese Loess Plateau.
I conducted the reconnaissance field trip and collected the initial sand samples. Later, I organized the logistics of the main trip and participated as a collaborator, and contributed to the manuscript of the paper.
Dating of the Martian surfaces
Matt Smith (post-doc at Harvard) observed that some of the craters on Mars are faulted. In this study, he mapped the faulted and unfaulted craters and proposed a new technique to directly date the tectonic activity on Mars (or any other planetary bodies).
I counted the craters and categorized into sub-groups of faulted and unfaulted craters.