Why Are Rising Sea Levels a Threat?

Aerial view of atolls and islands in The Maldives, Indian Ocean, Asia.

Sakis Papadopoulos / Getty Images

Researchers were astounded when, in the fall of 2007, they discovered that the year-round ice pack in the Arctic Ocean had lost some 20 percent of its mass in just two years. This set a new record low since satellite imagery began documenting the terrain in 1978. Without action to stave off climate change, some scientists believe that all of the year-round ice in the Arctic could be gone by as early as 2030.

This massive reduction has allowed an ice-free shipping lane to open through the fabled Northwest Passage along northern Canada, Alaska, and Greenland. The shipping industry, which now has easy northern access between the Atlantic and Pacific oceans, may be cheering this “natural” development. However, it's happening at a time when scientists worry about the impact of the rise in sea levels around the world. The current sea-level rise is a consequence of melting Arctic ice, to an extent, but the blame is more focused on melting ice caps and the thermal expansion of water as it gets warmer.

Threat From the Sea

According to the Intergovernmental Panel on Climate Change, made up of leading climate scientists, sea levels have risen some 3.1 millimeters per year since 1993. That's seven and a half inches between 1901 and 2010. The United Nations Environment Program estimates that some 80 percent of people live within 62 miles of the coast, with about 40 percent living within 37 miles of coastline.

The World Wildlife Fund (WWF) reports that low-lying island nations, especially in equatorial regions, have been hardest hit by this phenomenon. Some are threatened with total disappearance. Rising seas have already swallowed up two uninhabited islands in the Central Pacific. On Samoa, thousands of residents have moved to higher ground as shorelines have retreated by as much as 160 feet. And islanders on Tuvalu are scrambling to find new homes as saltwater intrusion has made their groundwater undrinkable, while increasingly strong hurricanes and ocean swells have devastate shoreline structures.

The World Wild Fund says that rising sea levels throughout tropical and sub-tropical regions of the world have inundated coastal ecosystems, decimating local plant and wildlife populations. In Bangladesh and Thailand, coastal mangrove forests — important buffers against storms and tidal waves — are giving way to ocean water.

It'll Get Worse Before It Gets Better

Unfortunately, even if we curb global warming emissions today, these problems are likely to get worse before they get better. According to marine geophysicist Robin Bell of Columbia University’s Earth Institute, sea levels rise by about 1/16 of an inch for every 150 cubic miles of ice that melts off one of the poles.

“That may not sound like a lot, but consider the volume of ice now locked up in the planet’s three greatest ice sheets,” she writes in a recent issue of Scientific American. “If the West Antarctic ice sheet were to disappear, sea level would rise almost 19 feet; the ice in the Greenland ice sheet could add 24 feet to that; and the East Antarctic ice sheet could add yet another 170 feet to the level of the world’s oceans: more than 213 feet in all.” Bell underscores the severity of the situation by pointing out that the 150-foot tall Statue of Liberty could be completely submerged within a matter of decades.

Such doom-day scenario is unlikely, but an important study was published in 2016 evoking the very real possibility that much of the West Antarctica ice sheet would collapse, raising sea levels by 3 ft by 2100. In the meantime, many coastal cities are already dealing with increasingly frequent coastal flooding ​and rushing to complete expensive engineering solutions which may or may not be enough to keep the rising waters out.