MECHANISMS FOR GLACIER ACCELERATION OF THE SOUTHERN PATAGONIAN ICEFIELD, CHILE

We aimed to quantify the impact of warm ocean water and lake drainages on glacier behavior for tidewater glaciers of the Southern Patagonian Icefield (SPI) and to establish a protocol for bi-monthly, long-term site monitoring. This is important because in recent decades the SPI has retreated at an accelerated rate coincident with rising atmospheric and ocean temperatures. However, how quickly the SPI will respond to continued warming and identifying the drivers of ice loss remain important questions to be addressed. In October 2019, supported by a GSA research grant, we sampled water temperature and salinity at the surface and to depths up to 10 m and collected data on surface reflectance, suspended sediment and plankton in front of two tidewater glaciers, Bernardo and Témpano, in Bernard O’Higgins National Park, Chile. We conducted three transects in Témpano Fjord and one in Bernardo Fjord (limited by iceberg discharge near the terminus). Results show a clear boundary between fresh glacial runoff and warm ocean water around 6 m depth close to the terminus of Témpano Glacier. In coordination with sampling efforts, we set up time-lapse cameras overlooking both glaciers to track iceberg movement and try to observe sediment plumes and surface currents. Additionally, we witnessed one of the earliest-known glacial lake outburst floods (GLOF) in a summer season at Bernardo Glacier. In witnessing this event, it is clear that to fully understand this dynamic ice-ocean system, we need longer duration measurements to capture both episodic events (GLOFs) and persistent forcing (ocean warming). To aid in long-term monitoring of ice/ocean interactions and GLOF events in this region, we established an agreement between three organizations participating in this project - Coporacion Nacional Forestral, Round River Conservation Studies, and UMaine Ice/Ocean group to continue this research in the coming years by sharing logistical support, scientific equipment, and data. With the SPI contributing a disproportionate amount of ice loss relative to the size of the icefield when compared with other mountain glaciers around the world, better understanding the mechanisms for tidewater glacier retreat in this region are critical for projections of future ice loss.