Topographic control of glacier changes since the end of the Little Ice Age in the Sierra Nevada de Santa Marta mountains, Colombia

The Sierra Nevada of Santa Marta (12°N) hosts a unique glaciated environment (6.5 km2) only 40 km distant from the Caribbean Sea. However, the remoteness of the glaciers and restricted access to the region has so far prevented onsite field work research from being undertaken. We worked with several very high resolution airborne and satellite images to delimit the extension of the glaciers during the maximum extension of the Little Ice Age (ca. 1850), when glaciers covered 81.6 km2, and the ice cover in four subsequent phases (1954, 1995, 2010 and 2016). Polar plots and Random Forest models enabled characterization of the spatial distribution of ice cover in the region, and how the impact of topographic and geographical variables changed over time. Results show that elevation was the most important variable in explaining the existence of glaciers during the LIA. Since then, the ice cover has gradually been receding to areas shielded from solar radiation, even though the solar angle at this latitude is very high. Thus, results clearly confirm that topography is increasing its importance to explain the glacier distribution over the study area, and the particular characteristics of where each ice body is found will gain importance. Nonetheless, the probability of ice being present as predicted by Random Forests in 2017 suggests that most of the ice cover located outside the most elevated areas of the Sierra is very likely to disappear in coming years.