Late Quaternary glacial dynamics of the Tien Shan

Project Summary

While global Quaternary climatic trends are reasonably well defined by reconstructed global sea levels (Spratt & Lisiecki, 2016) and marine oxygen-isotope records (Lisiecki & Raymo, 2005), there is increasing evidence that major "global" glacial events such as the Last Glacial Maximum (LGM) are not synchronous across the globe (Ehlers et al., 2011; Hughes et al., 2013). In Central Asia, a compilation by Owen and Dortch (2014) points instead to two distinct local LGMs: in arid regions, the maximal glacial extent likely occurred before the global LGM, while the regions subject to the wetter monsoon regime had a later local LGM. Another striking example of these local differences is the impact of the mid-Holocene Climatic Optimum (10 – 5 ka) (Marcott et al., 2013), which is globally defined as being characterized by warmer temperatures and widespread glacier retreat, but actually led to glacial advances in Central Asia due to the intensification of the monsoon and increased precipitation (Rupper et al., 2009). These results highlight the primary influence of local climate systems, rather than global climatic trends, in controlling local glacial dynamics in Central Asia. 

Despite these intriguing results, chronological controls on the timing of Quaternary glaciations in Central Asia are still poor. The vast majority of the data is situated along the Himalayas, and very few dates exist north of the Tibetan Plateau. Regions like the Tien Shan, which lie at the confluence of multiple climatic systems (Asian and Indian monsoons, the mid-latitude Westerlies, and the Siberian High-pressure system) offer the critical and underutilized opportunity to reconstruct the extent and timing of paleo climate variations, including how these different atmospheric circulation and precipitation systems have shifted over time.

This project will address one key question:  

What were the main glacial stages of the Late Quaternary in the Tien Shan, and what are the paleoclimatic implications of those stages?

• (1) Identify and sample potential MIS 4, MIS 5, and MIS 6 moraines. Because of the limited MIS 2 advance and the arid climate in the interior of the Tien Shan that tends to effectively preserve landforms, there is a unique opportunity to date older moraines, as shown by Blomdin et al. (2016) and Koppes et al. (2008).

• (2) Refine estimates of the LGM timing and glacial extents. Current LGM deglaciation ages for the Tien Shan span between 15 and 28 ka. This spread is likely due to the influence of local topographic effects and regional climatic variations. Available geochronological data do not have the required resolution to distinguish local from regional glacial stages. As a result, there is currently insufficient evidence to determine whether the LGM in the Tien Shan is synchronous with the Northern Hemisphere Ice Sheets, or if there is either a lag or a lead of glacial activity in the Tien Shan (Blomdin et al., 2016).

• (3) Constrain Holocene glacial variations. The Grigoriev Ice Cap and Issyk Kul core studies imply that a warm period during the early Holocene induced a massive deglaciation event in the Tien Shan before 12.5 ka (Takeuchi et al., 2014). If this event is widespread, moraine ages marking the beginning of this deglaciation event should be found in the region.

Field campaign

The field campaign took place during the summer of 2023! The team was composed of myself (team leader), Victoria Milanez Fernandes (postdoc researcher at the GFZ) and Tilek Omurbekov (Kyrgyz geologist). We are now waiting for the samples to ship to Germany for processing.