Before setting out to explore what's living within the Bering Sea's annual sea ice, scientists need to understand the sea ice itself.
The first important step is to understand how sea ice forms. When we think of the world’s oceans, we usually imagine large bodies of blue-green salt water. However, in the polar regions of our planet, conditions can be so cold that the surface of the ocean freezes. This happens when cool air temperatures and wind combine to chill the top layer of seawater to less than 28.8°F (-1.8°C).
Take a look at the videos below to learn more about how sea ice forms and how it fits into the Bering Sea ecosystem:
VIDEO: THE SCIENCE OF SEA ICE
This video explains how sea ice differs from ice formed on fresh water lakes and describes why sea ice is an important part of the Bering Sea ecosystem. (1:55)
Salt water and fresh water have very different physical properties. You may have noticed one example of this already- seawater freezes at a cooler temperature. This is because of the dissolved salt that makes sea water salty.
When ocean water freezes, only the fresh water forms ice crystals leaving the salts behind in concertrated liquid droplets called brine. As the water continues to freeze, the brine droplets grow and accumulate to form tiny passageways called brine channels.
So instead of being solid like an ice cube, sea ice is laced with these little brine channels that are filled with extremely salty water.
Because sea water freezes at a lower temperature than fresh water, sea ice can only exist in very cold locations. The National Snow and Ice Data Center estimates that only about “15% of the world’s oceans are covered by sea ice during part of the year”. Most of this sea ice is in the Arctic Ocean and the Southern Ocean surrounding Antarctica. Some areas of the ocean are covered with sea ice all year, while in other areas sea ice is only present during the coldest months of the winter.
The Bering Sea is an example of a region that only has sea ice during part of the year. Arctic sea ice begins to grow in September, extending South into the Bering Sea as the winter continues. The maximum sea ice extent is in March, and in the spring ice begins to melt away.
Plants, wildlife and humans all rely on the timing of the Spring sea ice melt. For plants, melting ice means access to light for photosynthesis. For animals and humans it means access to the food resources they depend on. Scientists expect that changes in the timing and extent of sea ice cover in the Bering Sea may impact the whole ecosystem.
Brine channels inside the sea ice provide a unique habitat for ice algae. When sea ice melts in the spring, this algae is released into the water below. In areas like the Bering Sea, where sea ice is not always present, the spring sea ice melt is an important annual event for the ecosystem.
VIDEO: SEA ICE ALGAE THROUGH THE SEASONS
This animation illustrates how sea ice algae in the Bering Sea varies through the seasons. (0:55)
To help them describe different parts of the ocean from the top down, scientists divide it into zones based on types of habitats. In the Bering Sea, three habitat zones exist: the sympagic, the pelagic and the benthic.
Dr. Gradinger and his team believe that, in the spring, plants and animals in the sympagic, pelagic and benthic zones are all impacted by sea ice. What they want to better understand is exactly how these species are impacted, by learning how they fit together in the food web.
Understanding what life is like in different areas of the Bering Sea ecosystem during the springtime helps Dr. Gradinger and his team begin to predict how the ecosystem might respond if Arctic sea ice coverage continues to recede.
The research team's curiosity with this previously understudied ecosystem led to the development of specific research questions and a project proposal that took them out on the ice!
WHO IS STUDYING SEA ICE?
POLAR (adj)- Describing the area of the Earth's surface around the North and South poles.
BRINE (n)- very salty water
PELAGIC (adj)- in the open ocean environment
BENTHIC (adj)- in the sea floor environment
SYMPAGIC (adj)- in the ice environment
PRIMARY CONSUMER(n)- an animal that feeds on plants; an herbivore
LARVAL STAGE (n)- a juvenile stage many animals go through before they grow into adults