Maria Gracia Bustamante

In recent decades, remote sensing has become a powerful tool for continuously monitoring glacier dynamics in remote areas, enabling the identification of significant spatiotemporal changes due to its capacity to provide multitemporal information at regional and global scales. In this study, Landsat satellite images (1989–2020) were used to quantify glacier retreat in the ice cap of King George Island (KGI), located in the Antarctic Peninsula, and to evaluate the teleconnections of El Niño – Southern Oscillation - ENSO (ONI and SOI indices) with climaticvariables (temperature and precipitation) in this region. Our findings reveal a 10% loss in glacier coverage over the last 31 years, with a slower glacier retreat observed since 2008. Glaciers with smaller areas and marine terminating were the most affected. Of the 73 glaciers on KGI, 42% had continental terminating, 21% had marine terminating, and 37% had mixed terminating (continental and marine). Of the total glacier area lost, 35% corresponds to glaciers with marine terminating, while 16% corresponds to glaciers with continental terminating. Furthermore, climatic variables exhibited heterogeneous responses during ENSO events, with a significant correlation between mean temperature and ONI at the annual level and during the austral spring, which may be influencing glacier retreat in the study area to some extent.

Our understanding of the climatic teleconnections that drove ice-age cycles has been limited by a paucity of well-dated tropical records of glaciation that span several glacial–interglacial intervals. Glacial deposits offer discrete snapshots of glacier extent but cannot provide the continuous records required for detailed interhemispheric comparisons. By contrast, lakes located within glaciated catchments can provide continuous archives of upstream glacial activity, but few such records extend beyond the last glacial cycle. Here a piston core from Lake Junín in the uppermost Amazon basin provides the first, to our knowledge, continuous, independently dated archive of tropical glaciation spanning 700,000 years. We find that tropical glaciers tracked changes in global ice volume and followed a clear approximately 100,000-year periodicity. An enhancement in the extent of tropical Andean glaciers relative to global ice volume occurred between 200,000 and 400,000 years ago, during sustained intervals of regionally elevated hydrologic balance that modified the regular approximately 23,000-year pacing of monsoon-driven precipitation. Millennial-scale variations in the extent of tropical Andean glaciers during the last glacial cycle were driven by variations in regional monsoon strength that were linked to temperature perturbations in Greenland ice cores¹; these interhemispheric connections may have existed during previous glacial cycles.