C51B-0704
Investigating a newly discovered firn aquifer on Disko Ice Cap, west Greenland: Insights from ground observations, remote sensing, and modeling
Friday, 18 December 2015
Poster Hall (Moscone South)
Luke D Trusel1, Sarah B Das1, Ben Smith2, Peter Kuipers Munneke3, Matthew Jared Evans4, Karen E Frey5, Matthew Osman1,6 and Ashley York5, (1)Woods Hole Oceanographic Institution, Geology and Geophysics, Woods Hole, MA, United States, (2)University of Washington, Applied Physics Laboratory, Seattle, WA, United States, (3)Institute for Marine and Atmospheric Research Utrecht, Utrecht, Netherlands, (4)Wheaton College, Norton, MA, United States, (5)Clark University, Graduate School of Geography, Worcester, MA, United States, (6)Massachusetts Institute of Technology, Earth, Atmospheric, and Planetary Sciences, Cambridge, MA, United States
Abstract:
Expanding and intensifying surface melt have accelerated contributions from Greenland to global sea level rise in recent decades. Yet, important questions remain regarding the evolution and eventual fate of this meltwater over time and space, a fact underscored by recent observations of expansive aquifers within the Greenland Ice Sheet firn. In April 2015 we observed liquid water retained at depth in an ice cap on Disko Island, central west Greenland. Two adjacent ~20 m firn/ice cores were collected before intercepting a layer saturated with liquid water as evident by water drainage from our cores. Borehole temperature profiling confirms increasing temperature with depth, revealing 0°C isothermal firn below ~10 m depth. Detailed physical stratigraphic analyses conducted on these cores allow us to assess firn properties and their small scale (< 1m) spatial heterogeneity. Notably, multiple, thick (>1 m) and likely impermeable refrozen melt horizons exist above the inferred aquifer surface, raising questions about processes of aquifer formation. To discern the spatial character of the observed firn liquid water and melt stratigraphy, we utilize ground penetrating radar collected in 2014, as well as airborne radar data collected through NASA Operation IceBridge in 2012 and 12 days prior to our field observations in 2015. Glaciochemical analyses on our ice cores reveal preservation of an annual signal allowing derivation of net snow accumulation rates. Combined with surface mass balance modeled by RACMO2.3 and melt assessed via microwave remote sensing, we investigate the recently prevailing climatic and glaciological conditions on Disko. This work will provide new insights into mechanisms of firn aquifer formation and sustenance more broadly, as well as the representation of aquifers in existing radar observations and firn models.
