SUNDAY STAR★TIMES World Big melt getting worse
A new scientific survey has found that the glaciers of the Arctic are the world’s biggest contributors to rising seas, shedding ice at an accelerating rate that now adds well over a millimetre to the level of the oceans every year.
This is considerably more ice melt than Antarctica is contributing, even though the Antarctic contains far more ice.
Driven by glacier clusters in Alaska, Canada and Russia and the vast ice sheet of Greenland, the fast-warming Arctic is outstripping the entire ice continent to the south – for now. However, the biggest problem is that both ice regions appear to be accelerating their losses simultaneously – suggesting that Earth could be in for an even faster rate of sea level rise in future decades.
Currently, the seas are rising by about 3mm each year, according to Nasa. This is mainly driven by the Arctic contribution, the Antarctic, and a third major factor – that ocean water naturally expands as it warms.
For Arctic ice loss, ‘‘the rate has tripled since 1986’’, said Jason Box, first author of the new study and a scientist at the Geological Survey of Denmark and Greenland. ‘‘So it clearly shows an acceleration of the sea level contribution.
‘‘Antarctica will probably take over at some point in the future, but during the past 47 years of this study, it’s not controversial that the Arctic is the largest contribution of land ice to sea level rise,’’ he said.
Scientists in the US, Chile, Canada, Norway and the Netherlands contributed to the work, which was published in the journal Geophysical Research Letters.
The Arctic is also losing floating sea ice at a rapid pace, but that loss does not contribute substantially to rising sea levels. Sea ice losses closely match what is happening on land – both phenomena are being driven by the fast warming of the atmosphere in the Arctic, which has heated up at a rate much faster than that seen in lower latitudes. Warming seas are also driving some of the ice loss.
The research was performed by merging a highly reliable gravity-based measurement of Arctic mass loss from Nasa’s GRACE satellites with older direct ice measurements going back to 1971.
The total Arctic loss at present is 447 billion tonnes of ice per year – which Box calculated was about 14,000 tonnes of water per second. That’s for the period between 2005 and 2015.
Between 1986 and 2005, the loss is calculated at around 5000 tonnes per second – therefore, the rate has almost tripled.
Separate research recently found that the Antarctic’s loss rate has also tripled in just a decade, reaching 219 billion tonnes per year from 2012 to 2017.
To give a sense of the scale of the Arctic losses, Box imagined what it would mean if they were distributed among the Earth’s human population.
‘‘If you take the 7.7 billion people on Earth and divide the present-day numbers from 2005 to 2015, each person on Earth would have the equivalent of 160 litres per day, every day, every year,’’ he said.