Subglacial lakes are repositories of ancient climate conditions, provide habitats for life and modulate ice flow, basal hydrology, biogeochemical fluxes and geomorphic activity. In this Review, we construct the first global inventory of subglacial lakes (773 in total), which includes 675 from Antarctica (59 newly identified), 64 from Greenland, 2 beneath the Devon Ice Cap, 6 beneath Iceland’s ice caps and 26 from valley glaciers. This inventory is used to evaluate subglacial lake environments, dynamics and their wider impact on ice flow and sediment transport. The behaviour of these lakes is conditioned by their subglacial setting and the hydrological, dynamic and mass balance regime of the overlying ice mass. Regions where climate warming causes ice surface steepening are predicted to have fewer and smaller lakes, but increased activity with higher discharge drainages of shorter duration. Coupling to surface melt and rainfall inputs will modulate fill–drain cycles and seasonally enhance oxic processes. Higher discharges cause large, transient ice flow accelerations but might result in overall net slowdown owing to the development of efficient subglacial drainage. Subglacial lake research requires new drilling technologies and the integration of geophysics, satellite monitoring and numerical modelling to provide insight into the wider role of subglacial lakes in the changing Earth system.
Subglacial lakes modify glacial conditions and flow. This Review provides a first global inventory of subglacial lakes, as well as outlining their settings, impacts and potential changes with climate warming.
Key points: We report a global inventory of subglacial lakes (773 in total): 675 from Antarctica (59 newly identified here), 64 from Greenland, 6 from Iceland, 2 beneath the Devon Ice Cap and 26 from valley glaciers.80% of subglacial lakes are stable, implying either closed systems or approximately balanced inflow and outflow; the remaining lakes are active and display one of five distinct activity patterns.Active subglacial lakes exhibit a quasi-linear relationship between mean discharge and lake volume; lakes in Greenland and Iceland exhibit higher discharge rates for a given lake volume than do lakes in Antarctica.Larger active subglacial lakes recharge at a faster rate than smaller lakes, suggesting an underlying control on lake refilling rate associated with lake size.Lakes are less likely to occur where climate warming causes ice surface steepening, but drainage will be of higher magnitude, producing transient ice flow perturbations that are more likely to cause a net ice flow reduction.Enhanced surface melt and rainfall inputs to the bed will modulate fill–drain cycles, increase the potential for catastrophic drainages and provide a supply of oxygen, sediment, microorganisms and nutrients.