Walking the steep riverbank, the scene unfolds with thunderous water and a power that reminds observers of nature’s raw force. The canal, though only a single path wide, carries a flow fierce enough to rival London’s Thames, its roar and whisper a striking testament to the elements.
Turning a corner reveals something almost surreal: a widening rift at the river’s base swallows water and births a colossal whirlpool. Mist erupts into the air as jets of moisture rise—an image that could be mistaken for a CGI blockbuster, yet it is happening right now.
A feature called a make cry, or a glacier pit in Spanish, is forming on the Greenland ice sheet right before the eye. This discovery sits uneasily with established scientific expectations, suggesting real anomalies beyond current explanations.
Diagram of a moulin slicing through the ice sheet
For 35 years, a glaciologist has studied how meltwater changes the speed and behavior of glaciers and ice sheets, and this scene marks a striking moment in that ongoing inquiry.
The massive surface hole is just the beginning of meltwater’s journey through the ice. As it channels toward moulins, it carves an intricate network of channels that runs hundreds of meters beneath the ice and continues toward the base of the ice cap.
When this water reaches the bottom, it feeds the subglacial drainage system. The network delivers water toward the edges and ultimately to the ocean, affecting the thermal balance and movement of the overlying ice sheet in important ways.
Events like this, along with fresh research into ice-sheet mechanics, challenge long-held ideas about what happens inside and under icy layers where direct observations are extremely difficult yet carry wide-reaching consequences.
Studies indicate that Greenland and Antarctica’s frozen layers are more vulnerable to global warming than some computer models suggest, and that internal processes can destabilize them from within.
This unfolding situation poses a crisis for the roughly 500 million people living in vulnerable coastal regions. Greenland and Antarctica hold vast reserves of fresh water locked in ice, with cumulative potential for sea level rise well over 65 meters in the long term. Since the 1990s, mass loss has accelerated, making it a central factor in future sea level changes.
Narrow cracks, vast implications
Moulins are almost vertical channels that funnel meltwater from the ice surface each summer. Greenland hosts thousands of these openings, and some are incredibly large given the ice thickness and rapid surface melting. On the surface they resemble tennis courts, but beneath the ice they reveal hidden chambers capable of swallowing entire cathedrals.
This makes the observed make cry even more puzzling, as it did not align with the expected pattern of rifts and melt ponds science had anticipated.
In a recent paper, it is shown that the ice sheets contain millions of tiny cracks created by excess meltwater. Because glacial ice is delicate on the surface, many of these fractures remain invisible to satellite sensing, even though they are widespread in melting zones across all ice masses.
In many cases, a current-driven hydrofracture allows water to penetrate deep without breaking through the bedrock, though even partial deep fractures can significantly impact ice-sheet stability.
When water enters, it damages structure and releases heat. The ice mass warms and softens, accelerating flow and melt
Water intrusion compromises ice structure and releases latent heat, warming the ice and softening it. This causes faster flow and melting, much like a candle that melts faster when heated. Water flow drives heat deeper into the ice, weakening internal structure and increasing susceptibility to warming.
Heat transfer via current-driven hydrofractures reshapes the inner fabric of ice sheets, pushing their stability toward higher risk in a warming climate.
Shifts that speed up ice loss
Over the last twenty years, melting events have grown more frequent and intense as global temperatures rise, with Arctic warming four times the global average. The ice sheet is flowing faster, breaking into icebergs, and has shed roughly 270 billion metric tons of ice annually since 2002. Greenland now contributes about 1 millimeter per year to global sea level rise.
A 2022 study concluded that even if warming were to end now, a sea level rise of at least 27 centimeters would be inescapable due to instability seen in recent decades. Current modeling underestimates some of these processes, which means policy estimates may be conservative and could understate future sea level risks.
Recent findings highlight that warmer ocean currents prod under ice shelves, speeding destabilization of outlet glaciers. Increased Greenland precipitation accelerates surface melt and ice movement, while surface algae and microbes darken the ice, absorbing more solar heat and speeding melt. Accumulated snow becomes a barrier, pushing more meltwater to run off. The water at the bottom then softens the bed, promoting base sliding and faster inner-ice flow toward the edges. New papers describe feedback processes beneath ice sheets that are not yet included in common computer models, often because they occur on scales too small for current simulations.
Two independent studies detect increased submarine melting at the land contact line in Greenland and Antarctica, where outlet glaciers and ice streams meet the sea. These processes can magnify climate change effects on ice sheets, and in Greenland, they could double their contribution to mass loss and sea level rise.
Current models underplay risks
Along with fellow glaciologists, it is argued that existing ice-sheet models used in assessments do not account for the rapid changes observed in Greenland and Antarctica or the threats they bring. These models frequently omit the newly recognized feedbacks, leading to underestimates of sea level rise. While strides have been made since early IPCC reports, much remains misunderstood.
The author, a field scientist, reflects on the privilege of working in these sublime environments and the disquieting implications for coastal populations around the world. The intention is to highlight the evolving science and the urgency of understanding what lies ahead for vulnerable regions.
Professor Alun Hubbard, based at the University of Tromsø in Norway, is noted for his leadership in Arctic glaciology and for chairing the Arctic Five collaboration.
This exploration underscores the need for ongoing, rigorous fieldwork and updated modeling to better anticipate changes in polar ice and their global consequences.
Note: This rewritten piece preserves the original structure while updating language for clarity and context in today’s climate discourse. It focuses on the observable processes, recent research, and the broader implications for sea level rise and coastal populations.