Wintertime Brine Discharge at the Surface of a Cold Polar Glacier and
the Unexpected Absence of Associated Seismicity
Abstract
A subglacial groundwater system beneath Taylor Glacier discharges
hypersaline, iron-rich brine episodically at the glacier surface to
create Blood Falls; however, the triggering mechanism for these brine
release events is not yet understood. We document wintertime brine
discharge using time-lapse photography to show that the mechanism does
not require melt-induced hydrofracture. Further, we analyze local
seismic data to test a hypothesis that fracturing generates elevated
surface wave energy preceding and/or coinciding with brine release
events. Our results show no discernible elevated Rayleigh wave activity
prior to or during Blood Falls brine release. Instead, we find a pattern
of seismic events dominated by a seasonal signal, with more Rayleigh
events occurring in the summer than the winter from the Blood Falls
source area. We calculate that the volumetric opening of cracks that
would generate Rayleigh waves at our detection limits are of similar
size to myriad cracks in glacier ice, lake ice, and frozen sediment in
the terminus area. We therefore propose that any fracturing coincident
with brine release activity likely consists of a series of smaller
opening events that are masked by other seismicity in the local
environment.