“In order to fully understand the sea-level change that has occurred in the past century, we need to understand the dynamics of the flow in Earth’s core” says Mathieu Dumberry, a professor in physics at the University of Alberta.
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“If you are melting glaciers from high latitudes-in Alaska, Greenland, or Iceland-you move mass away from the pole, toward the equator, which slows the Earth down”, said Jerry Mitrovica, the study’s lead author and a Harvard geophysicist who specializes in studying sea level change.
The moon’s gravitational pull acts like a lever, which also slows down the rotation, according to the researchers.
Dumberry explained that they were able to reach this figure by using the traditional way of identifying changes in the speed of the Earth’s rotation: by looking at records of ancient eclipses recorded by civilisations such as the Babylonians. In theory, rising sea levels – once estimated to be climbing at a rate of about 0.06 to 0.08 inches (1.5 to 2 millimeters) per year – should also have slightly shifted Earth’s axis and increased the rate at which the planet spins.
Two researchers check the melting permafrost of the Arctic ice cap.
The study, published this week in the journal Science Advances, concluded that shrinking glaciers are affecting the speed of the Earth’s rotation and how our planet is tilted on its own axis by redistributing all the once-frozen water around the world. Specifically, it could cause the Earth to spin a little bit slower.
First, the scientists noted that recent studies suggested 20th-century glacial melting was about 30 percent less severe than Munk assumed.
Moreover, the research team’s mathematical calculations and computer simulations found that prior research relied on erroneous models of Earth’s internal structure.
Based on their work reconciling these discrepancies, the scientists involved in the study are confident in predicting sea level to the end of the 21st century.
How much? Don’t expect too much extra time on your hands – researchers predict that a century from now, Earth’s slower rotation will make each day 1.7 milliseconds longer.
Furthermore, interactions between Earth’s rocky mantle and the planet’s molten metal outer core should have helped slow the planet’s spin more than was previously thought.
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The latest findings solve the problem of “Munk’s enigma”, confirming predictions of Earth changes forecast by land-survey data, theoretical predictions, and astronomical observation, Mitrovica said. “By resolving Munk’s enigma, we further strengthen the already-strong argument that we are impacting climate”.
