Earth’s two great ice sheets are continuing to lose enormous quantities of ice, with new satellite-based research highlighting the scale and speed of changes taking place across Greenland and Antarctica.

The latest assessment estimates that Greenland and Antarctica together lost about 11.3 trillion tonnes of ice between 1979 and 2023. The loss contributed roughly 31.4 millimetres to global sea-level rise, adding another significant warning about the long-term consequences of a warming planet.

The figures provide a clearer picture of how changes occurring in remote polar regions can eventually affect coastal communities thousands of kilometres away.

Two Ice Sheets, Different Responses

Greenland and Antarctica are not identical ice systems.

Greenland lies in the Arctic and is surrounded by relatively warm ocean waters. Its ice sheet is particularly sensitive to surface melting during periods of unusually high temperatures.

Antarctica, meanwhile, contains by far the largest store of frozen freshwater on Earth. Much of its ice rests on land below sea level and extends outward into floating ice shelves.

Because of these differences, scientists study each ice sheet separately while also examining their combined contribution to global sea-level change.

Why Ice Loss Matters for Sea Levels

When land-based ice melts and water eventually reaches the ocean, global sea levels rise.

This is different from melting floating sea ice. Floating ice already displaces water, so its direct effect on global sea level is comparatively small when it melts.

The Greenland and Antarctic ice sheets are important because they contain enormous amounts of ice stored on land.

Even relatively small percentage changes in these ice sheets can therefore have significant consequences over long periods.

The estimated 31.4-millimetre contribution since 1979 may appear modest when viewed against the height of an individual coastline, but sea-level rise accumulates gradually and affects the baseline from which storm surges and coastal flooding occur.

Greenland Has Become a Major Source of Ice Loss

Greenland has experienced substantial ice loss through both surface melting and the discharge of glaciers into the ocean.

During warmer periods, higher temperatures can increase surface melting across the ice sheet.

Meltwater can travel across the ice surface and eventually reach the ocean through rivers, channels and crevasses.

At the same time, glaciers along Greenland’s coastline can accelerate and release large quantities of ice directly into the sea.

These processes can reinforce one another. Warmer conditions can increase surface melting while changes around glacier fronts can influence the movement of ice toward the ocean.

Antarctica Is Losing Ice Through a Different Mechanism

Antarctica’s ice loss is particularly linked to changes occurring around its coastal margins.

Many Antarctic glaciers flow toward the ocean and are protected by floating ice shelves.

These ice shelves act somewhat like barriers that slow the movement of inland ice toward the sea.

When warmer ocean water reaches the underside of vulnerable ice shelves, it can increase melting from below.

As an ice shelf becomes thinner or loses structural strength, the resistance against inland glacier flow can decline.

That can allow more land-based ice to move toward the ocean.

Ice Shelves Are a Critical Part of the Antarctic System

The stability of Antarctic ice shelves is therefore extremely important.

A floating ice shelf does not contribute directly to sea-level rise simply by floating and melting. The greater concern is what happens to the grounded ice behind it.

If a protective ice shelf retreats or weakens, glaciers that were previously slowed by the shelf can accelerate.

This creates a pathway through which additional land-based ice enters the ocean.

The process can occur gradually, but in some vulnerable regions changes can become rapid once certain physical thresholds are crossed.

The Sea-Level Impact Extends Far Beyond Polar Regions

The consequences of polar ice loss are not confined to Greenland and Antarctica.

Sea-level rise affects coastal communities across the world.

Low-lying islands, river deltas and coastal cities can become increasingly vulnerable to flooding as the average sea level rises.

A higher baseline means that storms begin from a higher starting point. A storm surge that previously remained below a critical level can therefore cause substantially greater flooding when the background sea level is higher.

This can affect roads, ports, drainage systems, homes, industrial facilities and freshwater supplies.

Coastal Flooding Can Become More Frequent

Sea-level rise does not necessarily mean that a coastline will be permanently underwater.

One of the more immediate effects can be an increase in the frequency of coastal flooding.

Events that were once considered rare may become increasingly common as average sea levels rise.

This is particularly important for cities that already experience flooding during high tides, tropical cyclones or powerful storms.

The additional height created by rising seas can turn occasional flooding into a more regular infrastructure challenge.

Ice Loss Is Part of a Larger Climate Feedback

The loss of polar ice also has implications for the climate system itself.

Bright snow and ice surfaces reflect a significant portion of incoming sunlight back into space.

When ice disappears and darker ocean or land surfaces are exposed, more solar energy can be absorbed.

This is known as the ice-albedo feedback.

It does not mean that every melting event automatically accelerates warming at the same rate, but it is an important mechanism through which changes in the cryosphere can interact with the broader climate system.

Satellite Technology Has Transformed Polar Research

The scale of the latest assessment would have been extremely difficult to measure several decades ago.

Scientists now use satellites to monitor changes in ice-sheet elevation, surface movement, gravitational mass and glacier behaviour.

Repeated observations allow researchers to distinguish between short-term fluctuations and longer-term changes.

Satellite measurements are particularly valuable in polar regions because of their enormous size and difficult terrain.

Instead of relying exclusively on measurements from individual research stations, scientists can now examine changes across vast areas.

The Numbers Represent Decades of Change

The estimated 11.3 trillion tonnes of combined ice loss covers more than four decades.

That is important because ice sheets respond slowly to climate forcing.

The full consequences of today’s warming may therefore continue to appear for decades or longer, even if temperatures stabilize.

Some parts of the ice sheets can respond relatively quickly, while other processes operate over much longer timescales.

This makes long-term monitoring essential.

What Happens Next Depends on Future Warming

Future ice loss will depend on how Earth’s climate develops.

If global temperatures continue rising, many models indicate that Greenland and parts of Antarctica will continue losing mass.

The precise rate remains uncertain, particularly for Antarctica, where interactions between ice, ocean water and bedrock create complex dynamics.

Scientists therefore continue to improve models and satellite observations to understand how individual glaciers and entire ice-sheet systems may respond.

A Long-Term Warning for Coastal Planning

The latest assessment provides an important reminder that climate change is not only about hotter summers or stronger heatwaves.

Changes occurring in the polar regions can gradually alter global sea levels.

The process may be slow compared with a sudden natural disaster, but its cumulative effects can be enormous.

For coastal governments, this means that infrastructure planning must increasingly account for future sea levels rather than relying solely on historical flood patterns.

Ports, roads, drainage networks, coastal defences and urban development can all require planning horizons measured in decades.

The Bigger Climate Picture

The loss of billions of tonnes of ice is part of a much broader transformation of Earth’s climate system.

Greenland and Antarctica contain enough frozen water to influence sea levels on a global scale. Their current changes therefore represent more than a remote environmental phenomenon.

The latest research demonstrates how satellite observations are revealing the continuing movement of Earth’s largest ice reservoirs and providing increasingly detailed evidence of their contribution to sea-level rise.

For coastal societies, the central issue is not whether sea-level change will occur, but how rapidly conditions will evolve and how effectively communities can prepare.

As polar ice continues to respond to a warming climate, monitoring these regions will remain essential for understanding the future risks facing coastlines around the world.