An article featured in Nature Geoscience on July 30th, 2025 investigates a phenomenon that transpired in 2014 but was only recently unveiled due to satellite image archives. The Greenland Ice Sheet houses several subglacial lakes. One such lake experienced flooding, and in 2014, it burst through the glacier’s surface, discharging vast quantities of water. Why does this matter? Because this subglacial lake was previously unknown, and its flooding significantly impacted the ice sheet.
Satellites disclosed the astonishing impact of this flooding event. It unleashed 23.8 billion gallons of meltwater over a span of 10 days. This averages to more than 25,000 gallons per second. It formed a crater that was 279 feet deep and spanned 0.77 square miles. Furthermore, it generated ice blocks reaching heights of 130 feet, fractured the ice sheet, and caused additional cracks in the vicinity.
Initially, this region was assumed to be completely frozen. This event challenges entrenched beliefs regarding the movement of meltwater within ice sheets. The research indicates that existing climate models may not accurately predict how Greenland’s ice will react to future global warming.
The implications of Greenland’s hidden lake on our geological knowledge
The study underscores that over the last 30 years, approximately 169 billion tons of Greenland’s ice have melted annually due to intensified surface melting. This surface melt contributes to rising sea levels. As Arctic temperatures rise, the prevalence of meltwater is expected to increase. While it is recognized that surface meltwater can penetrate the ice bed and affect glacier motion, there remains ambiguity about its travel patterns, how much it is retained, and its overall environmental impact.
One rising concern is Greenland’s concealed network of subglacial lakes. As evidenced in 2014, these lakes can drain abruptly and release large volumes of water from underneath the ice, influencing surface and flow dynamics. Such occurrences are not well understood, infrequently observed, and inadequately represented in climate models.
The abrupt flooding of the subglacial lake disrupted the hydrological framework beneath the Greenland Ice Sheet and influenced the adjacent Harder Glacier. By evaluating over 5,800 ice velocity maps from 1985 to 2020, researchers noted that while the glacier had been speeding up since 2014, a sharp slowdown occurred immediately after the 2014 flooding, three times greater than the usual seasonal deceleration. The study suggests that the floodwater momentarily enhanced the efficiency of the subglacial drainage system, leading to reduced movement.
Insights from the Greenland subglacial flood
Researchers have posited a new hypothesis to account for the flooding. Rather than the conventional surface fractures forming directly above a water source, the study proposes that intense shear stress accumulated along the ice sheet’s frozen base spread outward and forced a crack to rise through the ice. This mechanism, known as hydrofracture, may have been intensified by altered glacier flow patterns that weakened the ice. The study observes that a similar drainage incident in 1990 did not produce surface fractures; consequently, the upward fracturing observed may occur only under certain conditions.
To verify this hypothesis, further observation is required to understand how these fractures develop and their effects on ice sheets overall. With this knowledge, a refined model can be established to enhance present geological understanding and better predict future scenarios concerning melting ice sheets.
The principal author of the study, Jade Bowling from Lancaster University, commented to Space.com, “The existence of subglacial lakes beneath the Greenland Ice Sheet is still a relatively recent discovery, and — as our study illustrates — there is still much we do not comprehend about their evolution and impact on the ice sheet system.” She added, “Crucially, our research highlights the necessity to better understand how frequently they drain, and what the repercussions are for the adjacent ice sheet.”
