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. (
Batbaatar, J., Gillespie, A.R., Fink, D., Matmon, A., Lai, ZP., 2017.
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