Greenland and coastal Louisiana may not seem to have a lot in common. An autonomous territory of Denmark, Greenland is covered in snow most of the year and is home to about 56,000 people. On the other hand, more than 2 million people call coastal Louisiana home and the region rarely sees snow.
But their economies, though 3,400 miles (5,400 kilometers) apart, share a dependence on the sea. The majority of Greenland's residents rely on the territory's robust Arctic fishing industry. And in Louisiana, the coasts, ports and wetlands provide the basis for everything from shipping to fishing to tourism. As a result, both locales and the people who live in them are linked by a common environmental thread: melting ice and consequent sea level rise.
NASA satellites are keeping an eye on both.
NASA Sees the Seas
Thanks to altimetry missions, beginning with the U.S.-French TOPEX / Poseidon mission launched in 1992 and continuing through the present with the Jason series, we now have a nearly three-decade-long record of sea level change.
Similarly, because of missions like the U.S.-German Gravity Recovery and Climate Experiment (GRACE) and its successor, GRACE Follow-On, we know a lot more about what the ice is doing than we used to, especially at the poles. For instance, we know that Greenland lost 600 billion tons of ice last summer alone. That's enough to raise global sea levels by a tenth of an inch (2.2 millimeters). We also know that both Greenland and Antarctica are losing ice six times faster than they were in the 1990s.
These numbers matter because frozen within all of the glaciers and ice sheets is enough water to raise global sea levels by more than 195 feet (60 meters) — key word here being "global." Ice that melts in Greenland and Antarctica, for example, increases the volume of water in the ocean as a whole and can lead to flooding far from where the melting occurred, like in coastal communities half a world away.
In addition to using satellite data to monitor sea levels and ice melt, NASA scientists are observing the seas from a closer vantage point.
"The satellites tell us it's happening. But we want to know why — what's causing it?" said Josh Willis of the agency's Jet Propulsion Laboratory in Southern California. "Generally speaking, it's global warming. But in a specific sense, how much is it the melting of polar ice sheets as opposed to glaciers? And how much is it ocean warming and thermal expansion?" he said, referring to how water expands as it warms. "Most importantly, what's going to happen in the future?"