Scientists have shown that giant, plume-like columns deep inside Greenland’s ice sheet are powered by slow thermal convection rather than by freezing at the base.
That hidden circulation means parts of the deepest ice move in ways that current forecasts have not fully accounted for, reshaping how scientists think about Greenland’s future contribution to sea-level rise.
Plumes in deep ice
Deep beneath the surface, radar images reveal towering columns where once-flat age layers of ice buckle upward from the bedrock.
Tracing those warped layers across northern Greenland, Andreas Born at the University of Bergen (UiB) demonstrated that modest temperature contrasts at depth can drive sustained vertical circulation inside solid ice.
The columns rise from near the base, push warmer ice upward through colder surroundings, and then fold back down at their edges, creating a self-sustaining pattern over thousands of years.
Such motion alters how stress is carried through the ice sheet, setting up the deeper questions about softness and flow that the next section takes on.
Heat makes softer ice move
Temperature contrasts inside an ice sheet can pile up slowly, especially where the base stays relatively warm.
Under those conditions, thermal convection, slow circulation driven by temperature and density differences, can push warmer ice upward.
As the rising ice cools, gravity pulls it back down at the edges, keeping the churning going.
“We typically think of ice as a solid material, so the discovery that parts of the Greenland Ice Sheet actually undergo thermal convection, resembling a boiling pot of pasta, is as wild as it is fascinating,” said Born.
Where plumes of softer ice form
Plumes showed up most often in northern Greenland, where the ice stays thick and moves more slowly toward the coast.
Thicker than about 1.25 miles (2 kilometers), deep ice has enough vertical room for warm material to rise and sink.
Fast surface flow and heavy snowfall tend to squash the pattern, because fresh snow pushes layers downward while ice slides sideways.
That mix of limits helps explain why the largest features cluster in the north, not across the whole island.
Finding Greenland’s softer ice
Deep below the surface, the team estimated that the ice in parts of northern Greenland could be around ten times softer.
In modeling terms, that points to lower viscosity – how strongly a material resists slow flow – near the ice bottom.
Warmer ice deformed more easily under pressure, so slight heating at depth made the column more willing to rise.
Assumptions about stiff deep ice can steer computer models toward the wrong stress balance, even when surface speeds match.
How motion changes flow
Softer ice at depth changed the way the ice sheet moved, because internal stretching started to carry more of the load.
Less reliance on basal slip – ice sliding over bedrock at its base – followed when deep layers flowed more freely.
Rising columns lifted warmer, softer ice into the middle, while sinking lanes carried colder ice downward into high stress.
More realistic deep flow could narrow the range of future coastline planning numbers, even before any new warming.
Why melt is uncertain
Softer ice did not automatically translate into faster melting, because melting depends on energy, not just on flow.
Heat from warmer air and ocean water still sets the melt rate at the surface and edges.
Changes in flow can speed some glaciers by feeding them more ice, yet other areas may slow as stresses rebalance.
Isolating how much convection matters will take more measurements inside the ice, not just better computers.
To test the idea, the UiB team turned to a tool normally used to simulate rising plumes of hot rock.
Instead of an ice-sheet model, the UiB group used ASPECT, a mantle-convection code that tracks how slow materials circulate.
By adapting ASPECT to a slice of ice, they checked whether a small, warm bump could trigger sustained overturning.
That cross-over let ASPECT borrow well-tested mantle physics, then apply it to a place most people assume stays locked solid.
Radar sees hidden layers
Radio waves sent through ice bounce off tiny changes in chemistry and density, creating layer lines that can be followed.
Scientists call that radiostratigraphy – layer patterns seen in ice-penetrating radar data – and the plumes show up as disruptions.
When layers bend upward from the base, the pattern hints that something is moving vertically inside the ice.
Repeated radar passes could reveal whether the columns are still growing today, offering a direct test of convection.
Greenland convection and softer ice
Coastline forecasts often circle one number – 24 feet (7.3 meters) of global sea-level rise if the Greenland Ice Sheet vanished, according to National Snow and Ice Data Center notes.
Sea-level forecasts rely on ice-flow models, and small changes in deep ice behavior can widen their spread.
“Our discovery could be key to reducing uncertainties in models of future ice sheet mass balance and sea-level rise,” said Born.
Better deep-ice physics can reduce guesswork, but the biggest swings still come from how much warming the world allows.
Seeing the plumes as heat-driven circulation links a strange radar signature to the basic physics that governs ice flow.
Future work will need boreholes, lab tests, and updated simulations before planners can treat softer deep ice as standard input.
The study is published in The Cryosphere.
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