http://www.theguardian.com/environme...axis-says-nasa
"Global warming is changing the way the Earth wobbles on its polar axis, a new Nasa study has found.
Melting ice sheets, especially in Greenland, are changing the distribution of weight on Earth. And that has caused both the North Pole and the wobble, which is called polar motion, to change course, according to a study published on Friday in the journal Science Advances.
Scientists and navigators have been accurately measuring the true pole and polar motion since 1899, and for almost the entire 20th century they migrated a bit toward Canada. But that has changed with this century, and now it’s moving toward England, according to study lead author Surendra Adhikari at Nasa’s Jet Propulsion Lab.
“The recent shift from the 20th-century direction is very dramatic,” Adhikari said.
While scientists say the shift is harmless, it is meaningful. Jonathan Overpeck, professor of geosciences at the University of Arizona, who wasn’t part of the study, said that “this highlights how real and profoundly large an impact humans are having on the planet.”
Since 2003, Greenland has lost on average more than 272 trillion kilograms of ice a year, and that affects the way the Earth wobbles in a manner similar to a figure skater lifting one leg while spinning, said Nasa scientist Eirk Ivins, the study’s co-author.
On top of that, West Antarctica loses 124 trillion kgs of ice and East Antarctica gains about 74 trillion kgs of ice yearly, helping tilt the wobble further, Ivins said.
They all combine to pull polar motion toward the east, Adhikari said."
Climate-driven polar motion: 2003–2015
http://advances.sciencemag.org/conte.../e1501693.full
"Earth’s spin axis has been wandering along the Greenwich meridian since about 2000, representing a 75° eastward shift from its long-term drift direction. The past 115 years have seen unequivocal evidence for a quasi-decadal periodicity, and these motions persist throughout the recent record of pole position, in spite of the new drift direction. We analyze space geodetic and satellite gravimetric data for the period 2003–2015 to show that all of the main features of polar motion are explained by global-scale continent-ocean mass transport. The changes in terrestrial water storage (TWS) and global cryosphere together explain nearly the entire amplitude (83 ± 23%) and mean directional shift (within 5.9° ± 7.6°) of the observed motion. We also find that the TWS variability fully explains the decadal-like changes in polar motion observed during the study period, thus offering a clue to resolving the long-standing quest for determining the origins of decadal oscillations. This newly discovered link between polar motion and global-scale TWS variability has broad implications for the study of past and future climate."
https://en.wikipedia.org/wiki/Polar_motion
It is interesting to consider out of the box things about what can go wrong with our civilization. The point being that this example (initially seen as harmless) is one result of our emerging impact to this planet that is now impacting even its rotation properties. The risk we take in not considering things more seriously is that one of these days something that is initially subtle will trigger another process that nobody thought that will then exponentially alter something else that is in a position to actually impact us dramatically. Have we thought out well all that can happen in a complex entangled world?
