Arctic is losing ice faster: Melt season is now 7.5 days longer than in 1979. What it means?

The Arctic is not simply losing sea ice — it is spending longer each year in a state that makes further warming easier. 

A new analysis led by University of Washington researchers has found that the Arctic sea ice melt season has become about 7.5 days longer since 1979, with the change driven primarily by ice forming later in autumn. The finding offers another indication of how rapidly the polar climate is changing and why the loss of Arctic sea ice matters far beyond the frozen north. 

The study, published on September 2 in Nature Reviews Earth & Environment, examines roughly five decades of changes in sea ice, including not just how much ice exists but also changes in its thickness, age and snow cover. 

Melinda Webster, a research scientist at the University of Washington's Applied Physics Laboratory and lead author of the paper, said scientists have long documented declines in Arctic sea-ice extent and thickness. The latest research goes further by examining the characteristics of the remaining ice, particularly perennial sea ice — ice that survives the summer melt season. 

Why a longer melt season matters 

Sea ice plays an important role in regulating Earth's climate because of its ability to reflect sunlight. 

Bright sea ice reflects roughly 60% to 90% of incoming sunlight back into space. The dark ocean, by comparison, reflects only about 7%, meaning it absorbs substantially more solar energy. 

That difference creates a powerful feedback loop. 

As the Arctic loses ice, more dark ocean water is exposed. It absorbs additional sunlight, warming the ocean. That stored heat then makes it harder for new sea ice to form when autumn arrives. 

According to Webster, the Arctic Ocean is now remaining too warm for ice to form as early as it once did. The result is a later start to the freezing season — effectively extending the period during which the Arctic remains largely open water. 

And when ice eventually forms, it tends to be thinner and more vulnerable to melting during the following spring and summer. 

This creates a cycle in which less ice leads to more heat absorption, delayed freezing and thinner ice, which in turn makes the following year's ice cover more vulnerable. 

Arctic is warming far faster than the planet 

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That makes sea ice both a visible indicator of climate change and an active contributor to it. 

The distinction is important. Arctic sea ice does not simply respond to a warming planet; its disappearance can amplify warming by changing how much solar energy the ocean absorbs. 

The consequences therefore extend beyond the length of the Arctic summer. 

Snow and ice are changing, too 

The researchers found another significant shift: snow cover on Arctic sea ice has become thinner, while the ice itself has become smoother. 

That may sound less dramatic than declining ice extent, but it can have serious ecological consequences. 

Polar bears and seals rely on snow drifts that accumulate on thick, deformed sea ice to create dens where they raise their young. Changes in the structure and snow cover of the ice can therefore affect their habitat and reproductive conditions. 

The changes also reach into the Arctic food web. 

Algae living in and around sea ice form the foundation of much of the polar marine ecosystem. These organisms evolved under extremely low-light conditions. Thinner snow and ice allow more sunlight to penetrate, potentially altering the environment in which the algae live. 

Because algae sit at the base of the food chain, changes affecting them can cascade upward to fish and other marine organisms — creating potential consequences for fisheries in both the Arctic and sub-Arctic regions. 

Why Antarctica is telling a different story 

The study also highlights an important contrast between Earth's two polar regions. The Arctic is an ocean surrounded by land, while Antarctica is a continent surrounded by ocean. Their physical geography means they respond differently to atmospheric and oceanic changes. 

For decades, Antarctic sea ice did not show the same persistent decline seen in the Arctic. That has changed in recent years. Antarctica experienced record sea-ice losses during the last four years, although understanding the reasons remains a major scientific challenge. 

Antarctic observations are also more difficult to obtain. Researchers have fewer measurements, and the region's sea-ice system is more complex, making the available data less precise than comparable Arctic observations. 

The new research arrives as scientists prepare for the fifth International Polar Year, an international effort to coordinate observations and research in Earth's polar regions. 

International Polar Years have traditionally taken place roughly every 30 to 50 years. The next one is being advanced much sooner than the historical pattern because of the speed of environmental change.