Why is Sea Ice Important?

Have you ever wondered what sea ice is and why it is so important? With the media focusing on the thinning sea ice around the globe, read more to learn about its importance and its relationship to global climate change! 

What is sea ice?
Sea ice is frozen ocean water that floats on the surface of the ocean and is found in both the Arctic and Antarctic. Around 15% of the ocean is covered with sea ice at some point during the year.
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What is the difference between sea ice and icebergs, glaciers, and lake ice?Sea ice is defined as ice that is formed in the ocean from saltwater. This is different from icebergs, glaciers, and ice shelves that are originally formed on land. Glaciers are a form of land ice and icebergs are parts of glaciers that break off into the ocean. Lake ice is the sheet of ice that forms over a lake in cold temperatures. Sea ice forms slower than other kinds of ice because of the constant movement of the ocean. 

What are the Arctic sea ice minimums and maximums?
Sea ice minimums and maximums represent the times when the sea ice cover is at its lowest or largest. The melting season for sea ice is from March to September and the sea ice minimum is usually around the end of summer. The cold, winter season is the other half of the year from September to March and the sea ice maximum is usually at the end of this period of time.

Why is sea ice so important?
Sea ice is important for a number of reasons, key among them being its role in the regulation of temperature. When frozen, sea ice is a bright surface that reflects sunlight back into the atmosphere. In the summer months, some of the sea ice melts allowing for the ocean to absorb more heat. In the winter, as the sea ice covers more surface area over the sea, more sunlight is reflected and therefore, more heat is reflected away from warming our planet. This effect helps keep the Arctic and Antarctic cool as well as more broadly helps moderate earth’s temperatures and climates. 
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Sea ice is also an important part of the global conveyor belt, or the circulation of ocean water around the planet caused by temperature and density differences. The water around sea ice is usually saltier than in other areas because salt does not freeze when the water does. This means that water around sea ice is also denser than the surrounding water and will sink down and be replaced by less-dense water. In this way, sea ice contributes to the global conveyor belt as well.

Sea ice houses its own ecosystem. Within the liquid brine water underneath and within sea ice live fish and invertebrates along with archaea, a small single-cell organism. Sea ice is also home to ice algae, which is arguably one of the most important organisms on the planet. The organisms that live in these sea ice ecosystems are food sources for many other animals too and create the base for the marine food web! 

What has been happening to sea ice with climate change?
Sea Ice has been melting at a rapid pace due to global climate change. Because of a global temperature that is on the rise as a result of climate change, sea ice has been melting faster than historically witnessed. More specifically, the surface-area and thickness of sea ice have been declining for the past 30 years. Sea ice melt means that both the sea ice minimum and maximums are smaller than in previous years. Models predict that by 2040 there might not be any sea ice left. 

What are the effects of the ice melt?
The Arctic and Antarctic regions are very sensitive to changing temperatures. Sea ice melt does and will continue to have many effects on ecosystems around the world. Since sea ice reflects sunlight off the earth and back into the atmosphere, the lack of sea ice means that more of this sunlight, aka heat, will be absorbed by the ocean. This will have further effects on the climate as well as it shifts the energy balance between the sun and the earth, causing more energy to be absorbed by the earth.

Sea ice melt could also affect the global ocean conveyor belt.  With less sea ice, there would be less frozen fresh water, and therefore there would be less of a density difference in the water. The water in the polar regions would also be warmer because of the heat absorbed (versus reflected) and there would be less push from opposing water densities that would normally drive the ocean conveyor belt.  

Saiyna Toran

Saiyana Toran is a junior at Albany High School. She grew up in Berkeley and Albany, California. She plays ultimate frisbee and the flute and she works with OYA as an intern.