Arctic ice pack

Big sheets of ice float on the Arctic Ocean.

This ice changes with the seasons. It melts in the warm summer. It grows back in the cold winter.

Some ice is very old and thick. This thick ice stays for many years. The white ice also acts like a mirror. It reflects sunlight away from the water. This helps keep the ocean from getting too warm. The ice is a very important part of our world.

The Arctic ice pack is a layer of ice on the ocean.

This ice follows a seasonal cycle. It melts in the spring and summer. It grows back in the autumn and winter. The ice reaches its smallest size in mid-September.

Some ice is very old. We call this multi-year ice. It is thicker than ice that melts every year. This thick ice helps keep the ocean warm. It acts like a blanket between the water and the cold air.

Ice also acts like a mirror. This is called the albedo effect. Bare ice reflects 60% of sunlight. If there is snow, it reflects 80%. This keeps the water from soaking up too much heat.

Scientists use satellites to study the ice. They found that the ice is shrinking. One study found the ice volume fell by 3% every ten years. Much of this is due to rising temperatures. As the ice gets thinner, storms can break it into pieces more easily.

This thin ice is often called first-year ice.

The Arctic ice pack is a huge layer of sea ice. It covers the Arctic Ocean and the areas around it.

This ice follows a regular seasonal cycle every year. It melts during the spring and summer months. The ice reaches its smallest size around mid-September. Then, it grows back during the autumn and winter. In the summer, the ice cover is only about 50% of what it is in the winter. Some ice is thick enough to survive many years. This is called multi-year ice, and it makes up 28% of the ice in the Arctic basin.

This ice works in a few important ways to help the Earth. First, it acts like a blanket for the ocean. It insulates the warm ocean water from the very cold air above. This helps stop heat from leaving the ocean. Second, the ice works like a mirror through the albedo effect. This is when a surface reflects sunlight. Bare ice reflects about 60% of sunlight. If the ice has snow on it, it reflects about 80%. This is much higher than the ocean, which only reflects about 10% of sunlight.

When seawater freezes, it also helps move water around the planet. As the water turns to ice, it leaves most of its salt behind. This makes the remaining water very salty and dense. This dense water sinks to the bottom of the ocean. This process helps maintain the thermohaline circulation, which is a way water moves through the sea.

In the Greenland Sea, a special area called the Odden ice tongue forms. This happens because of very cold water in the Jan Mayen Current. This current moves water eastward, which helps the ice grow in that spot.

Scientists have studied this ice for a long time. Records from the Hadley Centre go back to the start of the 20th century. However, the best data comes from the satellite era. In 1978, satellites like Seasat and Nimbus 7 began providing information. These tools work even when it is dark or cloudy. In 1987, the SSMI sensor improved how we measure the ice.

These tools help us see the difference between the area of the ice and the total volume. Monitoring the volume is very important for understanding how much ice we are losing.

Recent studies show that the Arctic ice is changing quickly. One study found that ice volume fell by 3% every decade from 1947 to 1999. This change was mostly caused by rising temperatures. Between 1979 and 2011, the September ice extent declined by 12% every decade. In 2007, the ice fell by more than a million square kilometers. In 2012, a new record low was reached.

As the ice becomes thinner first-year ice, it becomes less stable. Large storms can then cause the ice to break into many pieces.

The Arctic ice pack is a massive layer of sea ice covering the Arctic Ocean and its surrounding areas. This ice is not a permanent, unchanging block. Instead, it follows a regular seasonal cycle every year. During the spring and summer, the ice melts away. It reaches its smallest size, or minimum, around mid-September. As autumn and winter arrive, the ice begins to grow again. In the summer, the ice cover is only about 50% of the size it reaches in the winter.

Some ice is strong enough to survive these seasonal melts. This is known as multi-year ice, which is thicker than seasonal ice. Currently, multi-year ice makes up 28% of the Arctic basin sea ice. This ice can be very thick over large areas. It can even form ridges that are quite thick. In contrast, first-year ice is younger and thinner.

The ice pack plays a vital role in the Earth's energy balance. It acts as an insulator for the polar oceans. The ice sits between the relatively warm ocean and the much colder air above. This layer of ice reduces heat loss from the ocean to the atmosphere. The ice also affects how much sunlight the Earth absorbs through the albedo effect. Albedo is a measure of how much light a surface reflects. Bare ice reflects about 60% of incoming solar radiation. If the ice is covered with snow, it reflects about 80%. This is much higher than the open sea, which only reflects about 10%.

Sea ice also drives important movements in the ocean's water. When seawater freezes, it leaves most of its salt behind. This process creates very salty, dense water at the surface. Because this water is so dense, it sinks toward the bottom. This sinking helps create massive water masses like the North Atlantic Deep Water. This cycle is essential for maintaining the thermohaline circulation. This circulation is a global system of moving water.

In certain areas, unique ice formations occur due to specific currents. One example is the Odden ice tongue in the Greenland Sea. The word "Odden" is Norwegian for "headland." This ice tongue grows eastward from the East Greenland ice edge near 72–74°N. This happens because the Jan Mayen Current brings very cold polar surface water to the area. This current diverts some water eastward from the East Greenland Current. While old ice is driven south by the wind, new ice forms in the rough, cold open water. This new ice often forms as frazil or pancake ice.

Scientists have tracked these changes using many different tools. Reliable measurements of the ice edge began during the satellite era. In 1978, satellites like Seasat and Nimbus 7 provided data. These tools worked regardless of weather or sunlight. In 1987, the launch of the SSMI sensor improved the accuracy of these measurements.

Scientists distinguish between sea ice area and ice extent. Extent is defined as the area of ocean with at least 15% sea ice. Monitoring the total volume of the ice is even more important than monitoring the area.

Recent data shows a significant trend of declining sea ice. A study of the period from 1947 to 1999 found ice volume decreased by 3% per decade. This loss was almost entirely caused by temperature forcing. Between 1979 and 2002, the ice extent decreased by 2.5% per decade. The decline has accelerated in recent years. From 1979 to 2011, the September minimum ice extent declined by 12% per decade. In 2007, the minimum extent fell by more than a million square kilometers. A new record low was reached in 2012.

As the ice pack changes, it becomes more fragile. More of the Arctic is covered by thinner first-year ice. This thinner ice is less stable during large storms. Major extratropical cyclones can cause turbulence in the water. This turbulence leads to extensive fractures in the sea ice. This makes the ice pack more susceptible to breaking apart as it loses its thickness and multi-year strength.