Antarctica is losing ice because warm ocean water is eating away at the undersides of its ice shelves, and rising air temperatures are accelerating surface melting. Between 2002 and 2025, the continent shed roughly 135 gigatons of ice per year, enough to raise global sea level by about 0.4 millimeters annually. That rate has been increasing decade by decade, and the forces driving it involve a complex interplay of ocean currents, wind patterns, and the shape of the seafloor beneath the ice.
Warm Ocean Water Is the Primary Driver
The single biggest cause of Antarctic ice loss is a deep, warm ocean current called Circumpolar Deep Water. This water circles the entire continent at depth, and when it reaches the continental shelf, it can flow beneath floating ice shelves and melt them from below. The water doesn’t need to be hot. It just needs to be above the freezing point of ice under pressure, and at its warmest it exceeds 2°C above the local freezing point. That’s more than enough to erode massive volumes of ice over time.
How this warm water reaches the ice depends on the region. In East Antarctica, seasonal shifts in coastal winds allow the warm deep water to spill onto the continental shelf when easterly winds weaken during summer. In West Antarctica, the mechanism is different: westerly wind patterns drive an undercurrent along the shelf break that pushes warm water toward the coast through a network of troughs carved into the seafloor. In other areas, like the Weddell and Ross seas, the process is tied to the formation and export of cold, dense water off the shelf. As that cold water flows out through underwater canyons, it creates a pressure difference that draws warm water inward along the opposite side of the same canyon.
These aren’t random processes. They follow predictable seasonal patterns, but climate change is altering the strength and timing of the winds that control them, potentially increasing how much warm water reaches the ice.
West Antarctica Is Losing Ice Fastest
Not all of Antarctica is melting at the same rate. West Antarctica and the Antarctic Peninsula have been losing ice at accelerating rates for decades. A 2018 analysis by 80 polar scientists found that West Antarctica’s ice loss jumped from about 53 gigatons per year in the early 1990s to 159 gigatons per year by 2012-2017. The Antarctic Peninsula saw its losses climb from 7 to 33 gigatons per year over the same period.
East Antarctica, which holds far more ice, was long considered stable or even slightly gaining mass from increased snowfall. But that picture has shifted. A 2019 study examining data back to 1979 concluded that “East Antarctica is a major participant in the mass loss,” and that the entire continent’s rate of ice loss rose from about 40 gigatons per year in the 1980s to 252 gigatons per year by 2009-2017. That’s a sixfold increase in roughly three decades.
Thwaites and Pine Island: The Vulnerable Giants
Two glaciers in West Antarctica receive the most attention from scientists, and for good reason. Thwaites Glacier, sometimes called the “Doomsday Glacier,” and its neighbor Pine Island Glacier sit on bedrock that slopes downward toward the interior of the continent. This geometry creates a dangerous feedback loop. As warm water melts the ice at the point where the glacier meets the ocean (the grounding line), the grounding line retreats onto deeper bedrock. Deeper bedrock means thicker ice is exposed to the ocean, which increases the rate of melting, which causes more retreat. Scientists call this marine ice sheet instability, and it can make glacier retreat self-reinforcing and potentially irreversible.
Observations from beneath Thwaites show that the ocean cavity under the glacier contains water well above freezing, and that melting is concentrated along sloped and crevassed surfaces rather than flat ones. The ice base gets sculpted into steep terraces, and these steep faces melt faster, creating a feedback where melting reshapes the ice in ways that accelerate further melting. The bedrock beneath Thwaites plunges to 2,300 meters below sea level in places, giving the warm water an enormous volume of ice to work through.
Changing Wind Patterns Push Heat Toward the Ice
A major atmospheric pattern called the Southern Annular Mode, which describes the strength and position of the belt of westerly winds circling Antarctica, plays a significant role in how much the ice melts. When this pattern shifts to a weaker state (a more negative index), it allows warmer air to reach the continent and changes how energy reaches the ice surface.
The effects vary by region. In Wilkes Land (part of East Antarctica), weaker westerlies bring warmer air that increases the amount of heat radiated down to the ice surface. In Dronning Maud Land, the mechanism is different: weaker winds mean less snowfall, which leaves the ice surface darker and more absorbent of solar radiation. Both pathways lead to more surface melting, but through distinct physical processes. These wind patterns have been shifting over recent decades, partly due to the ozone hole and partly due to rising greenhouse gas concentrations.
Surface Melt and Ice Shelf Collapse
While ocean-driven melting from below dominates current ice loss, surface melting is expected to become increasingly important as air temperatures rise. When meltwater pools on the surface of an ice shelf, it can seep into cracks and act like a wedge, forcing the cracks open in a process called hydrofracture. This is what destroyed the Larsen B Ice Shelf in 2002, when thousands of meltwater ponds drained through the shelf in a matter of weeks, causing it to disintegrate almost overnight.
Most ice shelf regions that currently host surface meltwater are thought to be resilient to this kind of fracturing for now. But as surface melt expands into new areas, it could reach more vulnerable zones. This has already been observed at Shackleton Ice Shelf in East Antarctica. Ice shelves act as buttresses, holding back the flow of glaciers behind them. When a shelf collapses, the glaciers it was restraining speed up dramatically, dumping more ice into the ocean.
Temperature Thresholds and Long-Term Risk
Antarctica’s ice sheet doesn’t respond to warming in a smooth, gradual way. Instead, certain temperature levels can trigger abrupt, large-scale changes. Research published in 2025 mapped these tipping points across the continent and found that global warming of just 1 to 2°C above pre-industrial levels (a threshold the world is already approaching) could trigger the long-term collapse of roughly 40% of the marine-based ice volume in West Antarctica.
At 2 to 3°C of warming, major basins in East Antarctica enter the danger zone. The Wilkes Subglacial Basin, one of the largest, could lose 40% of its ice volume above flotation, translating to about 1.2 meters of global sea level rise on its own. At 2 to 5°C, marine-based sectors in East Antarctica holding the equivalent of about 5 meters of sea level rise are at risk of losing stability. These collapses wouldn’t happen overnight. They would unfold over centuries. But the critical point is that once triggered, they may be irreversible regardless of whether temperatures later come back down.
The total ice stored in Antarctica holds enough water to raise global sea levels by about 58 meters. Even losing a small fraction of that reshapes coastlines worldwide. At the current rate of 0.4 millimeters per year, Antarctica’s contribution to sea level rise is still modest compared to the total rate of about 3 millimeters per year from all sources. But the acceleration over recent decades, and the potential for self-reinforcing feedbacks to kick in, is what makes Antarctic ice loss one of the most consequential processes in climate science.