WASHINGTON: Earth's poles are drifting and climate change is to blame, claim scientists. The planet's rotation has always wobbled slightly, and over time this movement has caused the North Pole to shift very slightly over time.  But researchers now believe global warming could be drastically increasing this shift.

In 2005, the North Pole began to move suddenly in an easterly direction. Using Nasa satellite data, University of Texas researchers found that climate change, and in particular melting ice sheets, was to blame. Using the data, scientists also predicted that as as sea levels continued to rise, the shift would also carry on. Lead researcher Jianli Chen said that ‘ice melting and sea level change can explain 90 per cent of the shift’ and that ‘the driving force for the sudden change is climate change.’

Since 1899, the North Pole has been moving south by an average of 10cm a year along a 70-degree west longitudinal line. Between 1982 and 2005, the pole drifted 6cm a year in a south-easterly direction towards northern Labrador in Canada. In 2005, this drift abruptly changed and the North Pole began moving to the east, towards Greenland. Since that time it has shifted position by around 1.2 metres. Chen and colleagues studied changes in the Earth’s gravity during this time period using Nasa’s Gravity Recovery and Climate Experiment (GRACE) satellite images.

They were able to work out exactly how Earth’s mass had moved and changed during this time and found it was caused due to the melting of the ice sheets in Greenland and the Antarctic, which has in turn caused sea levels to rise.

Chen’s team hope that the discovery will provide scientists with a new way to measure the extent of ice sheet melting by tracing the movements of the pole. Greenland's ice sheet is said to be melting at a rate of 250 gigatonnes each year.  Antarctica is losing 180 gigatonnes of ice every year, and melting mountain glaciers adds a further 194 gigatonnes. These shifts in the Earth’s surface were found to ‘correlate perfectly’ with the changes in the position of the pole.–MOL

 According to previous research, this shift is also caused by changes in the Earth’s mass that have been occurring since the last ice age, affected by what’s called the Chandler wobble. The Chandler wobble is a wobbling motion that happens as the Earth rotates on its axis. It works in a similar way to how a spinning top wobbles as it slows down, and this causes the alignment of the Earth’s poles to vary in position as the planet spins.

The wobble was discovered by American astronomer Seth Carlo Chandler in 1891 and the poles can 'wander' up to approximately 20ft to 30ft off course over a period of 433 days, before settling. The wobble causes the latitude position of the geographic poles to circle during this 14-month period and this means star charts have to be updated regularly to reflect new reference points for the geographic poles. Chen presented the findings at the American Geophysical Union in San Francisco.