INVESTIGATING CLIMATE CHANGE INFLUENCED GEOHAZARDS AT BERING GLACIER, ALASKA WITH GLOBAL FIDUCIALS LIBRARY IMAGERY

In 1993, the Central Intelligence Agency’s MEDEA Group established the Global Fiducials Program to monitor ~300 environmentally sensitive fiducial sites. Each fiducial site was selected because it was a unique location that exemplified some condition or vulnerability that was being impacted by global environmental change. Selected sites served as benchmark locations for long-term monitoring of processes responsible for environmental change. All sites were monitored with high-resolution electro-optical imagery collected with U.S. National Imagery Systems (USNIS) sensors, some for nearly 30 years. When available, commercial satellite imagery, and Landsat and Sentinel Multispectral imagery were used to augment the USNIS imagery.

The Bering Glacier, Alaska fiducial site contains Bering Glacier’s piedmont lobe, its northern mountains, its marginal drainages, and its adjacent coastal forelands. It was selected because of ongoing and anticipated impacts of glacier surges and post-surge glacier retreat on associated ecosystems and landscapes.

The USNIS imagery collected to monitor and document Bering’s climate-ecosystem interactions has also been critical in depicting and understanding at least three significant geohazards events that have occurred within the Bering Glacier fiducial site: (1) a 5.0 x 10⁷ m³ ice-rock avalanche, triggered by melting alpine permafrost that occurred from the summit area of Mount Steller; (2) changes in the hydrology of the Bering’s western margin which has produced a cyclic ice-marginal lake filling and dumping sequence at Berg Lake, resulting in large areas of coastal plain flooding following rapid large volume subglacial water discharge events, each approaching 0.5 km³; and (3) a glacier surge event (2008-2012) with extensive ice surface disruption and up to 2 km of terminus advance, separating two extensive periods of rapid retreat, each characterized by terminus thinning, flotation, and massive calving of large tabular icebergs.

High resolution (1 m) literal imagery derived products (LIDP) produced from USNIS imagery were critical in documenting the multiple events observed at the Bering Glacier fiducial site. These LIDPs are available from the U.S. Geological Survey Global Fiducials Library (gfl.usgs.gov) for free, unrestricted, public distribution and use.