Melting ice from Greenland and the polar regions is causing sea levels to rise, moving mass around the planet in ways that are starting to slow down, scientists have discovered.
NASA
hide caption
change the caption
NASA
Climate change is causing widespread global impacts, but now scientists are discovering that it is changing the planet itself. The earth’s rotation is slowing down, lengthening the length of a day a little longer.
As temperatures rise, more ice is lost from Greenland and Antarctica. The meltwater flows into the oceans, redistributing the mass closer to the equator. When a planet is denser at the center, its daily rotation takes longer.
“This is evidence of the gravity of climate change,” said Surendra Adhikari of NASA’s Jet Propulsion Laboratory, who co-authored the study, which was recently released in Proceedings of the National Academy of Sciences.
Small changes, measured in milliseconds, are thousandths of a second. Although invisible on a human scale, it can affect computer systems that control financial transactions, GPS navigation and power grids.
“Everyday life is not sensitive at the level of one second,” said Judah Levine, a physicist at the National Institute of Standards and Technology. “Technology works, and people use technology and don’t understand the sensitivity.”
A day is not exactly 24 hours
The clock measures the day as 24 hours on the nose, but on a very dynamic planet like Earth, exactly 24 hours is not entirely correct.
“If you want to be more precise, the length of the day changes from day to day,” Adhikari said. “Today may be a little longer or shorter than yesterday.”
Various forces are constantly acting on the rotation of the planet. The pull of the moon continues to slowly rotate the earth by a few milliseconds every century. The rotation of the solid iron core at the center of the planet can also fluctuate slightly, causing Earth’s outer layers to move faster or slower. Even the movement of the earth’s crust, now slowly recovering after being covered by ice during the last ice age, affects the rotation.
Now, rapidly melting ice at the poles is shifting the planet’s mass, raising sea levels at the equator. Since 1993, global sea levels have risen an average of 4 inches and will rise 2 feet or more by the end of this century, depending on how much humans do to prevent climate pollution produced by burning fossil fuels.
As a result, the Earth is now slightly wider at the center, which rotates slowly like a roller skater. Skaters with extended arms skate slower than those with arms pulled close to the body. Adhikari and his colleagues found that melting ice has slowed the planet’s rotation by 1.33 milliseconds per century since 2000. If emissions remain high, that will increase to 2.62 milliseconds by the end of the century.
Adds leap seconds
While the amount of time does not mean much for everyday life, it can pose a problem for highly connected computer networks that society depends on. GPS and board navigation, as well as financial institutions and cell phone networks, all rely on time synchronization. Setting the clock can be a major technological headache.
Since 1972, 27 leap seconds have been added to world time to account for the slow rotation of the earth. The problem arises because timekeeping is controlled by the current atomic clock, not the rotation of the Earth. But in order for the time to match the rotation of the planet, a few seconds must be added. Tech companies have since fought the regulation, saying it could lead to network collapse.
Now, experts say climate change should be factored into the decision. But the melting of the ice has more serious consequences for the planet than time. Millions of people face losing their homes as polar ice melts and sea levels continue to rise.
“If you live in a low-lying coastal area, then you’re not concerned about leap seconds,” Levine said. “That’s the least of your worries. You have more serious matters to deal with.”
