GLACIAL LOSS IN THE EQUATORIAL ALPINE OF MEXICO

While glaciers are commonly associated with cold regions at high latitudes, they also exist at sufficiently high elevations nearer the equator. Alpine glaciers are particularly susceptible to climate-related changes, where many are experiencing rapid ice loss. The equatorial alpine regions in central Mexico are no exception: while three stratovolcanoes in the Cordillera Neovolcánica have possessed alpine glaciers in recent history, only two summits remain glaciated today (Pico de Orizaba, 19.03°N, 97.27°W, and Iztaccíhuatl, 19.18°N, 97.64°W), and both have lost significant area over the last several decades. The objective of this study is to extend the record of glacier monitoring in both regions and to better understand the factors driving recent glacier loss.

We map the glacial extent in both regions using multispectral remote sensing data (Enhanced Thematic Mapper Plus and Operational Land Imager on Landsat 7 and 8, and the Multispectral Imager [MSI] on Sentinel-2) over the past decade to identify regions of deglaciation. This effort uses a semi-automated method that calculates standard band ratios for glacier/snow detection. Optimal threshold values are identified manually and used to produce glacier outline polygons that are overlain on multiband color images and edited as needed. Preliminary mapping of the glacial regions using the most recent MSI images reveals that the remaining glacier area at Pico de Orizaba and Iztaccíhuatl are 0.99 and 0.23 km², respectively, where the latter reflects ice loss of ~15% since 2007. We will present additional observations on the temporal variations in glacial extent and an analysis of surface thermal variations over seasonal and annual timescales. Longer-term goals for this project include fieldwork to (1) conduct higher-resolution remote sensing analyses (including glacier surface topography) and (2) establish ground stations for in situ environmental monitoring. These tasks will help to clarify the factors affecting modern glacier loss.