Sea ice

There is a very common misconception that many have; perhaps because they are exposed to it through mass media such as youtube in a certain way. It is that the icebergs melting is causing the ocean levels to rise, and it is all because of global warming. However, this statement is only partially true. Because sea ice forms from the seawater it floats on, it behaves much like an ice cube in a glass of water. Like that ice cube, which does not change the water level of the glass when it melts, melting sea ice in the Arctic does not dramatically change sea level. Melting land ice, for example from the Greenland or Antarctic ice sheets, does contribute to sea-level rise. That’s because when land ice melts, it releases water that was previously trapped on land and adds to the water in the oceans. 

These sea ices, however, are currently declining. NASA has been tracking sea ice minimum (usually in September) and maximum (usually in March) since 1978. While the exact values may vary year to year, the overall trend is clear: the Arctic is losing sea ice year-round.

“The last 15 years, we’ve seen the lowest 15 sea ice minimum extents,” said Dr. Rachel Tilling, a sea ice scientist at the University of Maryland and NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “Each year we’re losing an area that’s roughly the size of West Virginia.”

It is also true that sea ice does help delay the process of atmospheric warming. Sea ice acts as a “blanket,” separating the ocean from the atmosphere; in addition to keeping sunlight out, sea ice traps existing heat in the ocean, keeping it from warming the air above. These “blankets” affect arctic life both above and below the sea. As ice crystals form above seawater, they leave behind salt in the ocean below. This dense, salty water sinks to the bottom of the ocean. The descending water in one location will be balanced out by rising motion in others, which results in more nutrient-dense water circulating up toward the surface. Those nutrients are essential to microscopic phytoplankton, which are then eaten by fish and animals. The regular melt-freeze cycle keeps underwater Arctic life thriving, from algae to killer whales.


Categories: Society