Are the Polar Ice Caps Melting Faster Than We Thought?

Icebergs are chunks of frozen glacial ice that break from glaciers and fall into the ocean. Global warming is causing more icebergs to form by weakening the glaciers, causing more cracks and making ice more likely to break off.

Some people compare melting sea ice to ice cubes in a glass of water. When the ice cubes melt, they don't increase the water level in the glass. So, how can melting icebergs cause global sea level rise?

It turns out, sea ice melting in the ocean is not really comparable to ice cubes melting in your water glass. That's because glaciers contain fresh water, which takes up more volume than salty ocean water [source: Huang]. However, their impact is small compared to the melting of Antarctic ice sheets.

The main ice-covered landmass on Earth is Antarctica at the South Pole, with about 90 percent of the world's ice (and 70 percent of its freshwater). The continent of Antarctica is covered with ice an average of 2,133 meters (7,000 feet) thick. If the entire Antarctic ice sheet melted, sea levels worldwide would rise about 61 meters (200 feet).

According to NASA, Antarctica is melting at an average rate of 147 billion metric tons of ice lost yearly. It's losing mass much faster than scientists previously thought.

At the other end of the world, the North Pole, there is no landmass. Instead, the Arctic is covered in a layer of floating sea ice. Since Arctic sea ice generally grows and shrinks throughout the year, scientists measure changes in the ice each September, when the ice is at its smallest.

Satellite images show us that the Arctic ice is shrinking by 12.6 percent per decade. Ice age is another helpful metric for tracking climate change. In 1958, Arctic sea ice was predominantly older, thicker ice. Today, the ice is younger and thinner, with over 70 percent of Arctic sea ice now considered "seasonal," meaning the ice melts and returns each year.

There is a significant amount of ice covering Greenland. If the Greenland ice sheet melted, it would add another 7 meters (20 feet) to the oceans if it melted. Because Greenland is closer to the equator than Antarctica, the temperatures there are higher, so the ice is more likely to melt. According to NASA, Greenland is melting at a rate of 271 billion metric tons of ice lost per year.

Water is most dense at 4 degrees Celsius (39 degrees Fahrenheit). Above and below this temperature, the density of water decreases (the same weight of water occupies a bigger space). As the overall temperature of the water increases, it naturally expands a little bit, making the oceans rise.

In 2019, the Intergovernmental Panel on Climate Change issued a new report containing various projections of the sea level change by 2100. They estimate the sea will rise between 0.43 meters (1.4 feet) and 0.84 meters (3.75 feet) by 2100. The rise will come from the ocean's thermal expansion and melting glaciers and ice sheets and have a devastating impact on coastal communities.