Arctic sea ice is a major concern for climate scientists, as it is one of the most sensitive systems to global warming. With potential impacts of further ice melt from both land and sea ice worldwide, monitoring the sea ice in the Arctic is an ongoing task.
Arctic sea ice can extend to the North Pole. At this point, the arctic sea receives a decreased amount of solar energy at the surface level because of the oblique angle the sun’s rays strike. In the winter season, over 15 million km2 of sea ice is present compared to 7 million km2 at the end of the summer melt season.
Sea ice is present longer in the Arctic than the Antarctic, allowing it to grow thicker. Most arctic sea ice ranges in thickness of 2 to 3 meters thick. Certain areas in the Arctic are covered with 4 to 5 meters of ice. Artic sea ice is quite mobile and tends to stay in cold Arctic waters. Floes, sheets of floating ice, tend to group together and stack together into thick ridges consequently making the ice thicker. This thicker ice stays frozen longer during the summer melting period and grows into the following autumn season.
Ocean currents produce warmer water in the south that travels north of the Atlantic Ocean. The warmer water prevents any sea ice from forming in the North Atlantic. In contrast, waters off the eastern coast of Canada and Russia are impacted by cold air moving west-ward off the land. The eastern Canadian coast is also fueled by southward flowing cold water currents that make it easier for sea ice to grow.
The Pacific Ocean and numerous rivers located in Canada and Russia provide a fresher, less dense water source into the Arctic Ocean. This causes the Arctic Ocean to have a layer of cold, fresh water near the surface and warmer, saline water below it. This mixture promotes an environment that allows for more ice growth in the Arctic than the Antarctic.
The Arctic ice is also classified by age, some ice is multiyear ice and some is single year ice. Multiyear ice contains less salty brine; this ice is more rigid and difficult to break (and has a low enough salt content that people sometimes drink it! ). It also contains more air pockets making it clear. Multiyear ice is more common in the Arctic than in the Antarctic due to ocean currents and wind patterns moving sea ice around Antarctica, causing most of the ice to melt in the summer as it moves into warmer waters. Additionally, the Arctic Ocean is land locked allowing more multiyear ice to form. In contrast, single year ice is ice that has been formed and been around for one year. Single year ice forms from young ice that has a thickness of 0.3 to 2 meters. Physical characteristics for single year ice include rough angular ridges, formed from a lack of pressure from the surrounding environment.
Both Arctic and Antarctic sea ice are closely monitored, however in terms of understanding climate change impacts, the Arctic sea ice is of higher concern. This is because Arctic ice remains throughout the summer months, reflecting sunlight (albedo) and cooling the planet.
Sea ice in the Arctic has experienced rapid decline due to anthropogenic warming. In contrast, the Antarctic has experienced a small increase in sea ice with the exception of the Antarctic Peninsula, located in the southern tip of South America which has experienced a significant loss in ice. This is due to wind patterns and ocean waves impacting the region. Wind patterns can cause strong low pressure systems to form that can deflect warmer temperatures from melting or preventing sea ice to form. Another contribution is due to continental ice sheets. When cold fresh water enters the ocean, it starts forming a colder layer of water on the ocean surface which favours sea ice growth.
The Arctic Ocean is intimately linked with the climate systems around it, making it more sensitive to changes in climate. This is looked at in contrast to Antarctica, where wind and ocean currents around Antarctica isolate the continent from global weather patterns, keeping it consistently cold.
Reasons why the Antarctic and Arctic are reacting differently to climate change are partly due to geological differences. Mentioned above, the Arctic is a region surrounded by both land and ocean, while the Antarctic is a continent completely surrounded by water. Antarctica is geographically isolated from global weather patterns by wind and ocean currents around it. In the Antarctic, temperatures are below the freezing point that even with some extent of global warming, temperatures could stay suitably cold to prevent large surface melting. However, the Arctic ocean isn’t, which is why is it more sensitive to temperature change and closely interconnected with climate systems around it. An example of this scenario is the Greenland ice sheets. They are warmer than the Antarctic ice sheet making them substantially more fragile and susceptible to global warming causes mass melting to occur.
The video below shows Arctic sea ice reaching its annual minimum extent :