“If we divided the recent loss from the Arctic land ice among the world’s nearly 8 billion people, each person would get 160 liters of water, each and every day of the year,” points out Jason Box.
The Glaciology and Climate Research Professor from the Geological Survey of Denmark and Greenland (GEUS) has just published a new scientific study in collaboration with colleagues from GEUS, Norway, Canada, the United States and the Netherlands.
“We show that the sea-level contribution from Arctic land ice is one third of the global amount since 1992, making the Arctic the largest regional source of global sea-level rise. Greenland alone, the largest recent global source, represents half (46 %) of the Arctic ice loss contribution to sea-level rise,” co-author and GEUS Senior Researcher William Colgan explains.
Field measurements
The new study reconstructs the year to year changes in the amount of ice stored on land across the entire Arctic for a 47 year period (1971-2017).
”Our approach uses field measurements of the balance of snowfall accumulation and surface melting. And in our case it provides an annual measurement sequence from 17 locations covering allArctic glaciated regions.We make a simple yet robust mathematical scaling of the observed field data to satellite gravity data from the GRACE mission,” says Jason Box.
The total loss of ice from Arctic glaciers, ice caps, and the Greenland ice sheet has averaged 447 gigatons of loss per year in the recent decade. The loss rate of Arctic land ice has increased threefold since 1986, from nearly 5000 tons of water per second during the “recent past” (1986-2005) to 14,000 tons per second in the present day (2005-2015).
Alaskan ice loss, roughly constant since 1988 is mostly from increased surface melting despite marine terminating glacier retreat at places like the large Columbia glacier.
Arctic Canada ice loss is about as large as from Alaska but started later, increasing sharply in the 1990s until 2013 and 2017, in which both years had a positive mass balance and resulting drop in cumulative sea level contribution. The long term increase in Canadian Arctic land ice loss, like elsewhere around the Arctic, is driven by increased surface melting from warming summers.
In the other Arctic regions: Arctic Russia, Svalbard, Iceland and Scandnavia, the sea level contributionsadd up to about as much as those fromArctic Canada.
The atmosphere drives varying land ice changes
Taken together, the sum of these regions produce 23 mm of sea level contribution since 1971. The acceleration begins really in the late 1980s when Arctic climate is shown to have shifted to a warming pattern.
Then from about year 2000 onward, it is roughly a linear sea level contribution because the rates of ice loss in Greenland and Arctic Canada have slowed down a bitbecause of persistent atmospheric circulation that has bought cold air down the west side of Greenland at the same time as the heat waves in Europe.
”Year to year extremes in sea level contributions from Arctic land ice are primarily attributable to persistent extremes in atmospheric circulation, highlighting the atmosphere as a dynamic driver of regionally varying land ice changes in both space and time,” Jason Box explains.