Chemical disequilibrium, or the long- term coexistence of two or more incompatible species, may be a useful metric for finding life. The presence of CH4 and O2 (that ought to react) in Earth’s atmosphere is an example and indicates biogenic sources of these gases. It is reasonable to think that life on an exoplanet or an icy moon would influence chemical disequilibrium because terrestrial life influences chemical disequilibrium by cycling almost all the bulk atmospheric gases. A chemical disequilibrium biosignature is appealing because it does not make assumptions about underlying biochemistry, unlike a search for biomolecules (e.g. DNA). Krissansen-Totton et al. (2016) calculated the atmosphere or atmosphere-ocean chemical disequilibrium of several planets and moons in our solar system. The metric used was the Gibbs free energy released when all chemical species are reacted together to an equilibrium state. They found that Earth’s atmosphere-ocean system has significantly more disequilibrium than any other planet due to biogenic fluxes. They propose high atmosphere-ocean chemical disequilibrium as a biosignature for exoplanets similar to the modern Earth, with photosynthetic biospheres. While disequilibrium is promising for detecting life on photosynthetic worlds, it remains to be determined how this metric applies to oceans in icy moons such as Europa and Enceladus. Indeed, an argument exists that purely chemosynthetic life will tend to destroy disequilibrium through its metabolism and produce anomalous equilibrium (Sholes et al., 2018). Thus, disequilibrium may have different interpretations: (1) High disequilibrium (uneaten food) on a dead world is an anti-biosignature. (2) High disequilibrium on a photosynthetic world would come from biogenic gases. (3) Low disequilibrium on a chemosynthetic world would be caused by biological consumption of chemical energy. We investigate the chemical disequilibrium biosignature for oceans on icy moons using analog environments: Antarctic subglacial lakes. First, we compute the disequilibrium in an observed “living” and modeled “dead” Antarctic subglacial lake. For a “living” subglacial lake, we use the aqueous composition of Subglacial Lake Whillans (SLW), located in Western Antarctica (Christner et al., 2014). For a “dead” subglacial lake, we model the steady-state chemistry of SLW if there was not life influencing chemical cycling. The disequilibrium calculation of both environments indicate that the “dead” lake has more available Gibbs energy than the “living” lake, suggesting that in purely chemosynthetic environments, anomalous chemical equilibrium is a sign of life, or inversely, that large chemical disequilibrium is an anti-biosignature. Our work on subglacial lakes can be considered within the context of measurements of Enceladus’ plumes by the Cassini Spacecraft. Plume measurements indicate relatively high available Gibbs energy in Enceladus’ ocean which may indicate low biomass, if life exists.