Initial in situ measurements of perennial meltwater storage in the Greenland firn aquifer

Abstract

[1] A perennial storage of water in a firn aquifer was discovered in southeast Greenland in 2011. We present the first in situ measurements of the aquifer, including densities and temperatures. Water was present at depths between~12 and 37 m and amounted to 18.7 ± 0.9 kg in the extracted core. The water filled the firn to capacity at~35 m. Measurements show the aquifer temperature remained at the melting point, representing a large heat reservoir within the firn. Using model results of liquid water extent and aquifer surface depth from radar measurements, we extend our in situ measurements to the Greenland ice sheet. The estimated water volume is 140 ± 20 Gt, representing~0.4 mm of sea level rise (SLR). It is unknown if the aquifer temporary buffers SLR or contributes to SLR through drainage and/or ice dynamics. Citation: Koenig, L. S., C. Miège, R. R. Forster, and L. Brucker (2014), Initial in situ measurements of perennial meltwater storage in the Greenland firn aquifer, Geophys. Res. Lett., 41,[81][82][83][84][85]

Dynamic perennial firn aquifer on an Arctic glacier

“…Our analyses show that the bright radar reflector that crosscuts firn stratigraphy represents a water table between relatively dry, unsaturated firn above and a saturated or nearly saturated perennial firn aquifer (PFA) below, with saturation increasing downward, as observed in the Greenland PFA [Koenig et al, 2014]. Our observations may not be directly comparable to summer firn water saturation on mountain glaciers Geophysical Research Letters 10.1002 due to the shallow depth of and more active discharge and recharge processes in mountain glacier firn [cf.…”

“…Storage of summer meltwater warms the ice beneath [e.g., Humphrey et al, 2012], potentially affecting ice rheology. More significantly, PFAs likely drain to the bed through moulins and crevasses, as suggested by Alley et al [2005] and Koenig et al [2014]; this has a variety of implications. Vertical transport of surface meltwater through crevasses and moulins has been linked to ice shelf breakup [e.g., Banwell et al, 2013], transport of surface water to the base of ice sheets can lead to rapid basal thawing in areas where the bed is below the pressure melting point [Parizek and Alley, 2004], and PFAs may provide a slow, steady flux of lubricating water to the bed in areas where basal channels are constricted and water increases rather than decreases basal lubrication [Sundal et al, 2011].…”

“…Water storage in perennial firn aquifers (PFAs) of ice sheet percolation zones may provide a buffer against contribution to sea level rise from increasing surface melt Forster et al, 2014;Koenig et al, 2014]. In southeastern Greenland, preliminary estimates, based on airborne radar, in situ measurements, and modeling, indicate that the PFA has an area of ∼70,000 km 2 and a water storage capacity equivalent to ∼0.4 mm eustatic sea level rise [Koenig et al, 2014].…”

“…In southeastern Greenland, preliminary estimates, based on airborne radar, in situ measurements, and modeling, indicate that the PFA has an area of ∼70,000 km 2 and a water storage capacity equivalent to ∼0.4 mm eustatic sea level rise [Koenig et al, 2014].…”

Greenland meltwater storage in firn limited by near-surface ice formation

“…3). Limited amounts of subsurface runoff cannot be ruled out where deep percolation prevails 11,14,18 . The low permeability of the thick near-surface ice layers is corroborated by a network of summer 2012 surface meltwater channels ( Fig.…”