More than 12 trillion tons of the Earth’s polar ice has melted, as scientists warn about sea-level rise

A glacier is a long-lasting mass of ice that flows slowly over land. An ice sheet is the largest type of glacier system, spreading across vast areas and feeding many individual glaciers. Both store freshwater as snow is compressed into ice over centuries or longer.

Greenland’s ice sheet covers a large island. Antarctica’s ice sheet covers a continent and is much larger. Their ice rests on land, so melting or flowing ice can add water to the ocean. Jakobshavn is one Greenland glacier carrying ice toward the sea.

Sea ice is different. It forms when ocean water freezes and floats on the ocean surface. When floating sea ice melts, it has little direct effect on sea level because it already displaces seawater. Land ice is therefore the main concern for rising seas. The article reports rapid losses from Greenland and Antarctica since 1979.

About 12.5 trillion tons, or 11.3 trillion metric tons, of ice melted from Greenland and Antarctica since 1979, according to the article’s cited scientific report. This is not a small seasonal change. It represents a huge loss from Earth’s largest stores of frozen freshwater.

The report gives a striking physical comparison. Spread across the continental United States, that amount would form a layer of ice about 5 feet, or 1.5 meters, deep. Imagine covering roads, fields, homes, and cities with ice taller than many people. The comparison helps turn an abstract trillion-ton number into a visible scale.

This ice came from land-based ice sheets and glaciers. When that ice melts or flows into the ocean, it contributes to sea-level rise. The total also shows why scientists closely track both ice sheets as Earth’s temperatures continue warming.

A glacier’s retreat means its front, or terminus, is moving backward toward land. It does not mean every part of the glacier moves that distance each day. At Jakobshavn, the reported maximum retreat is up to 164 feet daily, showing an exceptionally rapid change at the glacier’s ocean-facing edge.

That pace is roughly 50 meters per day. Warm conditions can melt ice at the surface and around the glacier’s front. Warmer ocean water can also reach the submerged ice and melt it from below. As the front becomes thinner or less supported, large ice pieces may break off as icebergs, a process called calving.

The figure is a snapshot of a maximum rate, not a promise that the glacier retreats exactly that far every day. Still, it illustrates how quickly a major Greenland glacier can respond to warming. Continued retreat can send more land ice into the ocean and raise sea levels.

Earth’s warming temperatures accelerate ice-sheet loss because ice melts when surrounding air, ocean water, or both become warmer. Warmer air can increase surface melting and reduce the snow that normally builds new ice. Warmer seawater can melt ice along the edges and beneath floating extensions.

Greenland is especially affected by surface melt. Meltwater can flow into cracks and help lubricate the ice’s base, allowing some ice to move faster toward the coast. In Antarctica, ocean water can attack the undersides of ice shelves. When those floating shelves thin or weaken, they may provide less resistance to inland ice flowing outward.

The article links warming Earth temperatures with accelerating melt in both major ice sheets. This matters because the ice is grounded on land. Continued warming can increase ice loss, glacier retreat, and sea-level rise, although the exact pace varies by place and depends on future temperatures.

Greenland’s and Antarctica’s ice sheets sit on land. When their ice melts, or when glaciers carry ice into the ocean and it melts there, that water becomes part of the ocean. More ocean water raises global average sea level. This is different from simply rearranging water already floating in the sea.

The article reports that about 12.5 trillion tons of ice from these regions melted since 1979. That loss is large enough to represent a major addition to the ocean. Rising seas can worsen high-tide flooding, storm-surge flooding, shoreline erosion, and saltwater intrusion into freshwater supplies. Local effects vary with land height, currents, and sinking or rising ground.

The most exposed places include low-lying islands, coastal cities, river deltas, and communities built near beaches or tidal rivers. As warming continues, more land-ice loss can raise seas further. Preparing coastlines becomes harder and more urgent as ice-sheet changes continue.

Land ice and floating sea ice differ mainly in where they are stored. Glaciers and ice sheets rest on bedrock. When they melt or flow into the sea, water moves from land into the ocean, increasing the ocean’s volume and raising global sea level.

Sea ice forms when ocean water freezes. Because it already floats, it displaces roughly the amount of seawater matching its weight. When it melts, the resulting water mostly takes up the space the ice had already displaced. This is why melting floating sea ice has little direct effect on global average sea level. Greenland’s and Antarctica’s ice sheets are land-based, so their losses matter directly.

Sea-ice decline still matters in other ways. Bright ice reflects sunlight, while darker ocean absorbs more energy. Losing it can therefore amplify warming and affect marine ecosystems. But for direct sea-level rise, the article’s focus is crucial: melting land ice from Greenland and Antarctica adds water to the ocean.

Sunlight passes through Earth’s atmosphere and warms the surface. The surface then releases energy as infrared heat. Greenhouse gases, including carbon dioxide, methane, and water vapor, absorb some of that heat and send energy back in different directions. This natural greenhouse effect keeps Earth much warmer than it would otherwise be.

Human activities strengthen the effect. Burning coal, oil, and gas releases extra carbon dioxide. Cutting forests reduces the removal of carbon dioxide from the air. Agriculture, landfills, and fossil-fuel production add methane and other warming gases. These gases increase the atmosphere’s ability to hold heat, shifting Earth’s energy balance.

As the planet warms, air and oceans can melt glaciers and ice sheets faster. The article connects this warming with accelerating ice loss in Greenland and Antarctica. More melting land ice can raise sea levels, while darker surfaces exposed as ice disappears can absorb more sunlight and add further warming.