## 2 Study Area  
The Changbai Mountains constitute the northernmost mountainous area in eastern China where Quaternary glaciers developed. Their geographic location is unique in that they link the Chinese Loess Plateau (CLP) to the Sea of Japan and its islands laterally; longitudinally, they connect Russia's Far East, China's vast sea area and Taiwan. Located on the eastern edge of the Eurasian Plate near the coast of the Western Pacific Ocean, Tianchi is the famous volcanic crater lake of the Changbai Mountains (Figure 1). The study area is located on the east coast of the Eurasian continent in the mid-latitudes. EAM-controlled waserly winds dominate its temperate climate throughout the year. The climate is windy in spring, warm for a short period in summer, foggy and cool in autumn and extremely cold in winter. According to the records of the Tianchi meteorological station (2623 m) over many years, the average temperature in spring is \(-8\)\({}^{\circ}\)C, in summer is \(7\)\({}^{\circ}\)C, in autumn is \(-10\)\({}^{\circ}\)C and in winter is \(-23\)\({}^{\circ}\)C. The growing season is short. The highest temperature (T) in the Tianchi area of the Changbai Mountains occurs in July and the lowest in January. Most precipitation (\(P\)) in the Tianchi area falls in July, with the lowest amounts recorded in January. The EAM circulation controls \(P\) in this study area, resulting in an uneven seasonal distribution of \(P\), with the summer months accounting for \(\sim\)60-70% of total annual \(P\)[25, 26].  
The authors' field surveys and previous studies [10, 11, 27] have identified the main types of glacial remnants preserved in the area. These include cirques, glacial valleys, terminal moraine ridges and medial moraine ridges. Eight cirques can be found in the study area, principally in the caldera; here, the mean altitude of the base of the cirques is 2239 m asl (Table 1). Typical glaciated valleys include the Heifengkou and Erdaobaiahe valleys on the north-facing slopes of the Changbai Mountains and the Xipotingchechang and Songjianghe valleys on the west-facing slopes. The Heifengkou and Xipotingchechang valleys contain well-preserved terminal moraine ridges. There are also well-preserved medial moraine ridges in the Songjianghe Valley (Figure 2). The lower limit of the glacial remnants of the LGM in the study area is 1850 m asl [13, 26]. [PERSON] [28] considered that the last Quaternary glaciation in the Tianchi area occurred during the LGM. [PERSON] [12] also believed that the last glaciation in this area was during the LGM. [PERSON] [27] conducted a chronological study of two sets of moraines preserved in the Tianchi area of the Changbai Mountains using optically stimulated luminescence (OSL) dating techniques and determined that there were glacial advances in both the LGM (\(\sim\)20 ka) and the Last Glacial Period (LGP; 11 ka).  
Figure 1: Location map of study area. This picture shows the location of Tianchi Lake, the location of the weather station used later and the nearby river (30 m resolution ASTER GDEM V2 dataset: [[http://www.gscloud.cn/](http://www.gscloud.cn/)]([http://www.gscloud.cn/](http://www.gscloud.cn/))) (accessed on 10 January 2024).  
\begin{table}
\begin{tabular}{l c c c c c c c c} \hline \hline
**Cirque Name** & **1** & **2** & **3** & **4** & **5** & **6** & **7** & **8** & **Mean Value** \\ \hline elevation (m) & 2243 & 2251 & 2237 & 2252 & 2246 & 2257 & 2219 & 2203 & 2239 \\ \hline \hline \end{tabular}
\end{table}
Table 1: The bottom elevation values of 8 cirques in Tianchi crater. These data can help calculate the the equilibrium line altitude (ELA) value of the LGM.  
Figure 2: Glacier geomorphology map of the last glacial maximum in Tianchi area of Changbai Mountains. The information in this image includes the location of the cirque, the glacier valley and the moraine in the Tianchi area (30 m resolution ASTER GDEM V2 dataset: [[http://www.gscloud.cn/](http://www.gscloud.cn/)]([http://www.gscloud.cn/](http://www.gscloud.cn/))) (accessed 19 December 2023).