Arctic sea ice helps steer winter weather in North America and Europe, sometimes in ways that catch people off guard.

When the ice cover shrinks or thins, the ocean and atmosphere trade heat differently. That can affect large-scale winds that guide cold outbreaks and storms.

Scientists have long tracked how less ice can alter the energy balance in the Arctic and ripple into weather patterns farther south. The effect is not automatic, and it plays out alongside many other climate drivers.

Walt Meier of the National Snow and Ice Data Center (NSIDC) has studied these changes for decades. His team’s monitoring work helps explain why regional cold snaps can still happen in a warming world.

Cold spells are more likely when high-latitude winds weaken and meander. That sets the stage for lobes of Arctic air to slip into the midlatitudes.

Arctic ice and the polar vortex

The Arctic vortex is a persistent low-pressure circulation that, when strong, holds frigid air near the pole. Sometimes it weakens, and when that happens, cold air can spill south.

The polar vortex is a massive circulation of cold, low-pressure air that normally stays centered over the Arctic.

At times, this circulation can weaken and shift away from its usual position. When that happens, the jet stream, which normally flows in a fairly tight pattern, becomes more wavy and irregular. These waves allow frigid Arctic air to break free and move southward.

The result can be sharp temperature drops across large areas of the United States, heavy snow in the Great Lakes region, and prolonged cold spells in parts of Canada and Europe.

Not every cold snap is a polar vortex event. Still, the vortex is a useful signal to watch as winter approaches.

What satellites saw in 2025

Arctic sea ice reached a record low winter maximum on March 22, 2025, at 5.53 million square miles. That was the lowest maximum in the 47-year satellite record.

By August, the long-term summer decline continued. For August 2025, the downward linear trend in extent was 9.8 percent per decade relative to 1981 to 2010, with the month averaging 2.09 million square miles of ice.

The age mix of the pack matters too. Multiyear ice now makes up only a small fraction of what it was in the 1980s, and the oldest ice is minimal.

Sea ice, sunlight, and heat

Brightness plays a critical role in how the Arctic interacts with sunlight, since ice, snow, and open water each reflect or absorb energy differently.

Sea ice and snow bounce much of the sun’s radiation back into space, while darker ocean water soaks it up and stores the heat.

This difference in reflectivity helps determine how fast the region warms, how stable the ice cover remains, and how much energy feeds into the atmosphere above.

“The ocean reflects only 6 percent of the incoming solar radiation,” stated the National Snow and Ice Data Center.

Sea ice reflects 50 to 70 percent, so a loss of ice lets the ocean absorb more heat, which can slow ice growth later.

Warmer open water also feeds heat and moisture back to the air. That exchange can thicken clouds, nudge pressure systems, and reshape the near-surface winds that herd cold air.

Different types of ice

Not all sea ice is the same. First-year ice is relatively thin, usually less than four feet thick, and still salty because it has not yet flushed out the brine trapped during its formation.

It develops in autumn, grows through winter, and often melts away in summer.

Multiyear ice survives at least one melt season and is typically 6.5 to 13 feet thick. It is harder to break, stores less brine, and tends to resist melt longer than younger ice.

When first-year ice dominates, the pack is thinner and easier for storms to fracture. That can increase leads, speed up drift, and change how quickly early-winter cold can build.

Tracking Arctic sea ice changes

Satellites observe and analyze sea ice day and night through clouds using microwave sensors. These instruments distinguish ice from open water and track daily changes over the entire Arctic.

Researchers track the height of sea ice above the water to figure out how thick it is overall.

When those measurements are combined with records of how the ice moves and how long it has survived, scientists can tell if the ice cover is becoming thinner, younger, or breaking apart more easily.

Field teams still drill and sample ice to ground-truth the satellite record. Those spot checks, along with buoys and ship surveys, keep the long-term record reliable.

What to watch this winter

A recent paper finds a temporary slowdown in the rate of Arctic sea ice loss since 2005, consistent with natural variability. That pause does not mean the ice is healthy or that winters will turn mild.

The record-low winter maximum in 2025 left a thin starting point for autumn growth. Thin ice forms more quickly, but it also fractures and melts more easily under winds and warm spells.

Winter outcomes will depend on how the stratospheric vortex behaves, the placement of high and low pressure over the Arctic, and ocean heat near the ice edge.

If the vortex weakens for weeks, expect a greater chance of sharp cold snaps in parts of the United States, Canada, and Europe.

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