Sea Ice Today

Analyses and daily images of sea ice conditions

Studying sea ice

Common questions about polar sea ice

Sea ice is ocean water that freezes and floats on the ocean surface in the polar regions, growing throughout the fall and winter, and shrinking throughout the spring and summer.

NSIDC monitors sea ice throughout the year. One metric NSIDC tracks is sea ice concentration: the percentage of sea ice coverage over a particular area. Another metric NSIDC tracks, and the main metric NSIDC reports, is sea ice extent: the area of ocean with at least 15 percent sea ice concentration.

For more information about sea ice and its role in Earth’s climate, see NSIDC’s Learn About Sea Ice.

Will the ice at the North Pole melt? How will we know if it does?

People sometimes associate the North Pole with the entire Arctic region, but the North Pole is a single point on the globe located at 90°N. In contrast, the term Arctic generally refers to a region encompassing parts of Russia, North America, and Greenland, as well as the Arctic Ocean.

If the Arctic Ocean effectively loses its summertime sea ice, so will the North Pole. Since satellites have generally orbited near but not directly over the pole, there has been a data gap at that latitude. Historically, the lack of satellite data directly over the North Pole has not concerned scientists; they have always assumed that the area underneath is covered with sea ice.

Long-term Arctic sea ice declines have compelled scientists to consider the possibility that the North Pole will lose its summer sea ice cover. Fortunately, the newer sensors now used have a much smaller data-observation gap, For example, the DMSP F17 and F18 SSMIS sensors currently used in our analyses leave a pole hole with a radius of less than 100 kilometers. Other sensors do not have a pole hole at all, such as the NASA Moderate Resolution Imaging Spectroradiometer (MODIS) and VIIRS instruments. To learn more about how scientists study sea ice, see our Learn about Sea Ice: Science page.

Has the Arctic Ocean always had ice in summer?

In the distant past, the Arctic was ice-free. Fossils from roughly 55 million years ago indicate a warm climate with palm trees and crocodiles above the Arctic Circle.

The Arctic was quite possibly free of summertime ice 125,000 years ago, during the height of the last major interglacial period, known as the Eemian. Temperatures in the Arctic were higher than now and sea level was also 4 to 6 meters (13 to 20 feet) higher than it is today because the Greenland and Antarctic ice sheets had partly melted. The last warm period in the Arctic peaked about 8,000 years ago, during the so-called Holocene Thermal Maximum. Some studies suggest that as recently as 5,500 years ago, the Arctic had less summertime sea ice than today. However, it is not clear that the Arctic was completely free of summertime sea ice during this time.

What would it mean for Arctic sea ice to recover?

Arctic sea ice has shown a decline over the course of the satellite record dating back to November 1978. More recently, Antarctic sea ice has shown signs that it might have begun a declining trend, although more observations are needed to confirm. These changes in sea ice raise the question of what it would mean for sea ice to “return to normal.”

Sea ice extent typically varies from year to year, much like the weather changes from day to day. But just as one warm day in October does not negate a cooling trend toward winter, a slight annual gain in sea ice extent over a record low does not negate the long-term decline.

Even though Arctic sea ice has not matched the record-low minimum extent of September 2012, the data show that it is not recovering, either. Arctic sea ice also remains much thinner than in the past. For more information on ice thickness, see Getting beneath the ice.

Antarctic sea ice has historically shown much less of a long-term trend, instead showing extreme year-to-year variability. It has, however, experienced mostly below-average extents since 2016.

So what would scientists call a recovery in sea ice? First, a true recovery would continue over a period of multiple years. Second, scientists would expect to see a series of sea ice extents that not only exceed the previous year, but also return to within the range of natural variation. In a recovery in the Arctic, scientists would also expect to see a return to a sea ice cover dominated by thicker, multiyear ice.

Is Antarctic sea ice increasing or decreasing?

In contrast to the Arctic, Antarctic sea ice extent has been mostly characterized by a small overall trend and extreme year-to-year variability. Since 2014, Antarctic sea ice has exhibited both record-high and record-low extents. From 2013 through 2015, Antarctic sea ice extent was mostly above average. Beginning in 2016, however, extent fell mostly below average. In September 2023, the Antarctic winter maximum set a record low by a wide margin. The low Antarctic sea ice extent through much of 2023 was significant enough to flip the long-term annual mean trend from slightly positive to slightly negative.

NSIDC’s Sea Ice Index data, however, indicate that in September (the month of the winter maximum), the trend for Antarctic sea ice remained positive—though just barely—from 1979 through 2023; the slope was 0.1 ± 0.6 percent per decade. As of 2024, it is too soon to tell whether the mostly low extents beginning in 2016, as well as the record-low winter and summer extents observed in 2023, signify the start of a long-term decline in Antarctic sea ice, in either winter or summer.

For more information, see How does Antarctic sea ice differ from Arctic sea ice? To see data on Antarctic sea ice, see the Sea Ice Index.

What was sea ice like before the satellite era?

Read the Ask a Scientist article: How was Arctic sea ice measured before the satellite era?

Updated August 15, 2024

Causes of global climate change and sea ice decline

How do we know human activities cause climate change?

Fossil fuel burning is responsible for climate change because of how an increased concentration of carbon dioxide in the atmosphere alters the planet’s energy budget and makes the surface warmer.

The most fundamental measure of Earth’s climate state is the globally averaged surface air temperature. We define global warming as an extended trend in this temperature. Such a change cannot happen unless something forces the change. Various natural climate forcings exist. For example, periodic changes in the Earth’s orbit about the sun alter the seasonal and latitudinal distribution of solar radiation at the planet’s surface; such variations can be linked to Earth’s ice ages over the past two million years. Changes in solar output influence how much of the sun’s energy Earth’s surface receives as a whole; more or less solar energy means a warmer or cooler global climate. Explosive volcanic eruptions inject sulfur dioxide and dust high into the stratosphere. The resulting chemical reactions create sulfate aerosols, which block some of the sun’s energy from reaching the surface and causing it to cool. These are climate forcings because they alter the planet’s radiation or energy budget.

An increase in the atmosphere’s concentration of carbon dioxide is also a climate forcing: it leads to a situation in which the planet absorbs more solar radiation than it emits to space as longwave radiation. This means the system gains energy. The globally averaged temperature will increase as a result. This is in accord with a fundamental principle of physics: conservation of energy. As humans burn fossil fuels, adding carbon dioxide to the atmosphere, globally average temperature rises as a result.

For more information about the human contribution to climate change, visit:

Do sunspots cause climate change?

Some people wonder if the reason the sea ice is declining and the planet is warming can be explained by sunspots, which are related to variations in the sun’s energy output over time. While changes in the sun's output can affect the Earth’s climate, the recent warming cannot be explained by changes in solar activity.

For more detailed information about this question, visit:

Have undersea volcanoes caused the Arctic sea ice decline?

Studies have discovered active volcanoes on the floor of the Arctic Ocean, and some people have wondered if they are causing sea ice to melt.

While volcanic eruptions surely warmed the ocean in the immediate vicinity of the eruptions, the amount of heat they produced compared to the large volume of the Arctic Ocean is small. The Arctic Ocean covers 14 million square kilometers (5.4 million square miles), about 1 ½ times the size of the United States or 58 times the size of the United Kingdom. In its deepest spots, the Arctic Ocean is 4,000 to 5,500 meters (13,000 to 18,000 feet) deep. The heat from the volcanoes would have dispersed over an enormous volume and had little effect on ocean temperature, much as a bucket of boiling water emptied into a lake would have little effect on the lake’s temperature.

Second, the eruptions would have introduced heat deep below the sea ice that floats on the ocean surface. The tops of even the tallest undersea volcanoes are more than 1,000 meters (3,000 feet) below the ocean surface. The Arctic Ocean is strongly stratified, which prevents layer mixing and makes it difficult for any deep water, even deep water warmed by heat from volcanoes, to reach the surface and melt the ice. This layering results from a strong density gradient: water layers near the surface are less salty and therefore less dense, while bottom waters are the densest. Unlike most oceans, where density gradients are determined by both salinity and temperature, Arctic Ocean waters are heavily stratified primarily because of variations in salinity.

Do icebreakers contribute to climate change?

Read our Ask a Scientist article: Are icebreakers changing the climate?

Do hurricanes in the Atlantic break up Arctic sea ice?

Remnants of hurricanes do reach the Arctic but their impact on sea ice is probably minimal. Even the big storm that occurred in August 2012 played a small role in the record-low minimum.

Once Arctic sea ice is broken up, does it melt faster?

Yes. Waves, sea spray, winds, and melt ponds all affect sea ice. If the ice is broken up, the areas of open water between floes absorb a great deal of solar energy in summer. That energy can be transferred both to the sides of the floes and underneath the floes, promoting further melt.

Wind direction is also important. Warm southerly winds can promote melt, both because they bring warm air and because southerly winds move ice northward away from the coast. Storms and their associated sea spray can work to reduce the albedo, or reflectivity, of the ice, further increasing melt. Other effects of wind on sea ice either push the ice together, resulting in a smaller extent, or spread it out, resulting in larger expanses of sea ice at a lower density. These processes are known as convergence and divergence, respectively.

Unfortunately, computer simulations do not capture the level of detail that these sorts of processes entail. It may be that some of the more detailed melt processes are not yet captured properly.

If warm Arctic conditions suggest continued global warming, then why doesn’t colder-than-usual weather in my region suggest global cooling?

We note recent Arctic weather conditions in our reports because they help us understand if weather has affected the ice this season. The year’s weather conditions in the Arctic do not create or indicate climate warming, just as a cooler season in any region of the Earth does not mean that climate is cooling. One season’s weather could either speed up or slightly slow down the loss of Arctic sea ice this year, but it will not change the climate trend and the basic causes of warming.

Climate is a measure of the average conditions over a long period of time, so it is a better way to tell if changes may be persistent. Climate records show that the Arctic has warmed substantially over the past decades. The Arctic continues to warm faster than any other region of the world. Global data still show the Earth to be warming on average.

Scientists expected that the Arctic could warm faster than other places on Earth, a phenomenon known as Arctic amplification, because of the way the Arctic interacts with the global climate system. Arctic warming is a special concern because its effects can speed up the warming of the whole Earth.

The following Web sites have more information on the science of climate change:

Updated August 15, 2024

Possible Solutions

Is renewable energy the answer?

Almost every study published in peer-reviewed scientific journals confirms that Earth’s climate is warming because of fossil fuel burning. People naturally wonder what other sources of energy we could use, with renewable energy often being the one they ask about. NSIDC scientists do not specialize in renewable energy, but the following non-NSIDC resources might be of use:

If we put white “styrofoam” in the ocean to replace sea ice, would it stop climate change?

Resurfacing the Arctic Ocean with ice substitutes probably would not work to stop climate change.

One reason is that the Arctic is a vast region. If we attempted to bring the Arctic back to long-term average levels of “ice,” we would need to add approximately 2.6 million square kilometers (1 million square miles) of foam to the Arctic Ocean. This would be the equivalent of covering Alaska and Texas, or ten United Kingdoms, with polystyrene foam. Studies would also need to be done concerning the environmental impact of introducing such vast quantities of a human-made substance in the ocean, the albedo difference between ice and foam, the longevity of the solution, the cost of such an effort, and the carbon dioxide emitted during foam production and placement.

That said, even if foam were a viable solution that was immediately undertaken, it still would not halt climate change right away. The climate system already has some heating yet to be realized; it has not yet caught up with the effects of fossil fuel burning of past decades. People sometimes refer to this future heating as heat “in the pipeline.” In a way, this is similar to how a credit card works. We have already “spent” fossil fuels, but we have not yet “paid” the full charge in terms of temperature rise. So, even if we were to prevent any more ice from melting, the planet still has some additional warming on the horizon.

Updated August 15, 2024