Quirks & Quarks

As Sea Levels Rise, The Earth Slows Down

Rising sea levels cause water to move from poles to around the equator, which slows the Earth's rotation

Climate warming leads to rising sea levels, and the Earth gets middle-age spread, slowing rotation

Earth from Space (NASA, Terra MODIS spacecraft image)
The Earth's rotation is known to have slowed down over the past three thousand years, based on various calculations. Ancient Babylonian, Arab, Chinese and Greek eclipse records suggest the rotation has slowed by about 4 1/2 hours over that time. Also, the reduction of massive ice sheets that once covered the Earth has changed our planet's shape, which slows the rotation by a few millionths of a second per year.

But there was a problem - known as Munk's enigma - trying to fit data for 20th century glacial reduction and sea level rise, into models based on those previous calculations. Now a new study by Dr. Sabine Stanley - a Professor and Canada Research Chair from the University of Toronto - and her colleagues, have looked at changes in the Earth's magnetic field for new data to solve that enigma. 

Those magnetic field changes represent the shifting in the flow of the liquid core of iron in the Earth's mantle. That flow is affected by the Earth's rotation. The new data now fits with those previous models and concludes that current sea level rise, from melting glaciers, is contributing to the on-going slow-down of the Earth's rotation.

Related Links

- Paper in Science Advances
The Guardian story
- Washington Post story
- CBC News story