Greenland's ice sheet melting so fast it has caused global sea levels to rise 0.5mm in just a month

Half of ice sheet's surface thought to be melting as African plume that baked Britain now blasts the Arctic

Jon Sharman
Friday 02 August 2019 11:40
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Greenland hit by ‘extreme’ temperatures as Europe’s heatwave moves north

Greenland is experiencing “extreme” temperatures as the record-setting heatwave that blasted Europe last week hovers over the region.

Up to half the surface of the island’s ice sheet is thought to be currently melting, with runoff equivalent to a 0.5mm rise in global sea levels in July alone.

It comes less than a week after Britain saw its hottest-ever day, with a high of 38.7C recorded at Cambridge botanic garden last Thursday. Germany, Belgium and the Netherlands also experienced record-high temperatures due to a plume of air from north Africa.

Greenland has seen abnormally high temperatures so far this summer, scientists have told The Independent, with melting expected to rival the record levels seen in 2012.

Dr Andrew Sole, a glaciologist from the University of Sheffield, said: “This year Greenland and other parts of the Arctic have experienced some record-breaking temperatures. In mid-June, temperatures along the eastern coast of Greenland were up to 9C above the 1981-to-2010 average.

“In early July I was on an expedition to northeast Greenland in Kronprins Christian Land at 80 degrees north, and we measured a temperature of 17C in the shade. In addition, Alert, a military base and meteorological station at the northern tip of Ellesmere Island in the Canadian Arctic at 82 degrees north, experienced a temperature of 21C in mid-July.”

Dr Amber Leeson, of the University of Lancaster, said that temperatures had breached the 0C mark “in even the highest and coldest” areas of Greenland, where the mercury ordinarily hits an average of -10C at this time of year. “The Danish Meteorological Institute thinks that yesterday, about half of Greenland’s ice surface was melting – that’s twice as much as is normal for July,” she told The Independent.

And Dr Twila Moon, of the University of Colorado’s National Snow and Ice Data Centre, told The Independent that temperatures over large areas of the ice sheet reached 5C or more above average on Wednesday.

“These are extreme temperatures for the ice sheet, and communities around the Greenland coast are likely bracing for flooding from ice melt,” she added. “Forecasts for this week suggest that this may be the second-largest melt event – in terms of surface area of melt – since records began in the 1950s.”

Ruth Mottram, of the Danish Meteorological Institute, told CNN this week that an estimated 180 billion tons of Greenland’s ice had melted into the ocean since 1 July, raising sea levels by about 0.5mm.

The melting ice sheet

Explained by Dr Andrew Sole, University of Sheffield

The Greenland ice sheet and surrounding ice caps routinely experience melt on a seasonal basis – they lose mass by melting and iceberg calving in the summer, and gain mass through snowfall in the winter. The net sum of this gain and loss is the ice sheet’s “mass balance” and is usually measured over a year.

In years of anomalously high melt, such as 2012 or as 2019 is turning out to be, the gain in mass over winter is insufficient to replenish the ice and snow melted in summer, and the annual mass balance is negative.

Greenland has had a negative annual mass balance since about the early 1990s, due to enhanced melting and calving of icebergs. However, the rate of mass loss increased markedly in the mid-2000s. Since 2010 the ice sheet’s mean annual mass balance has been about -300 billion tons, equivalent to a mean global sea level rise of about 0.8mm a year.

This year there have already been significant spikes in melt rate and extent in mid-June and early July.

Apart from the direct influence of the melting ice on sea level rise, the Greenland ice sheet also has a significant impact on regional and global climate. Increased fresh meltwater runoff from the ice sheet may affect ocean circulation in the North Atlantic Ocean, potentially weakening the northwards transport of heat from tropical latitudes.

Over longer timescales, thinning and shrinking of the ice sheet will change local and regional atmospheric circulation patterns, and reduce the reflectivity of the Earth’s surface leading to an increase in the amount of solar radiation absorbed.

The current level of melting is a symptom of global climate change, said Dr Ryan Neely of the National Centre for Atmospheric Science, a research centre in Leeds. He said conditions at the Summit observation station at the top of Greenland’s ice sheet “have been the most extreme we have ever observed”.

He told The Independent: “We have observed melt events before at Summit but never the multiple days of melt that we have observed this week. Previous to the last couple of days, we had a melt event on 12 June, 2019. Before that was on 11 July, 2012. Before that was in 1889.”

However, one researcher sounded a note of caution regarding the severity of the current weather.

While record-breaking temperatures in parts of the northern hemisphere were a “sure sign” of climate change, said Professor Jeffrey Kargel of Arizona’s Planetary Science Institute, “at this time we cannot say that a couple of days of hot weather in Greenland will result in a sea level change, or that a subsequent period of colder weather than normal might negate this heatwave”.

He added: “We need to wait for scientists to go about producing, vetting, and releasing scientific results before we can say that any significant changes have occurred to the melting rate due to this heatwave.”

News of Greenland’s heatwave came as the UK’s Met Office revealed the country’s 10 hottest years on record had all occurred after 2002. None of the 10 coldest have taken place after 1963, analysis showed.

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