Reconstruction of permafrost cover and periglacial dynamics during the last permafrost maximum at Cofre de Perote volcano, Mexico

Synchronous with the Last Glacial Maximum (LGM), a Last Permafrost Maximum (LPM) also occurred, during which maximum global permafrost coverage was reached. Despite its strategic location and the existence of glacial evidence at Cofre de Perote, no local studies have addressed this topic. Using records of ground and air temperature, and by arithmetically adjusting present-day temperature values with the estimated cooling that occurred during the LPM, we reconstructed permafrost coverage and periglacial dynamics for this period. Between 1960 and 2020, the average temperature in the Trans-Mexican Volcanic Belt increased by 0.43 °C. Furthermore, the presence of permafrost during the LPM was confirmed: its lower limit was located at 3870 m a.s.l., covering an area of 7 km², while seasonal frozen ground extended down to 3553 m a.s.l. The active layer persisted from April to June, with an average thickness of 55 cm near the summit. The ground profile exhibited a geothermal gradient of 0.0197 °C/cm, while the vertical air temperature gradient was −0.0057 °C/m. Freeze-thaw cycles followed a parabolic trend, with a total of 148 cycles near the summit, increasing to 244 cycles at 4137 m a.s.l., and decreasing again to 84 cycles at 3870 m a.s.l. These results suggest that the periglacial conditions and landscape at this mountain during the LPM were similar to the present-day conditions at Pico de Orizaba volcano. This study contributes to the paleoclimatic reconstruction of this mountain and provides a reference framework for future scenarios in the cryosphere of intertropical regions.