Sea level rise now inevitable

The world is facing a minimum sea level rise of 27cm even if there was a total end in the use of fossil fuels today.

The stark prediction is based on two decades worth of measurements carried out by glaciologists from the National Geological Survey of Denmark and Greenland (GEUS) to determine the minimum ice loss committed from the Greenland Ice Sheet as from the climate warming so-far.

The team said the aim was to remove the uncertainty of any positive or negative future climate scenario, to define the absolute minimum of what is to come.

It concluded if the whole world stopped burning fossil fuels today, the Greenland Ice Sheet would still lose about 110 quadrillion tonnes of ice leading to an average of global sea level rise of at least 27 centimetres.

By looking at the climate in the Arctic from 2000 to 2019 and the imbalance it has created in the Greenland Ice Sheet, researchers have calculated that the shape of the ice is set in motion to correct this imbalance – inevitably – by losing 3.3 percent of its current volume, which corresponds to the 27 cm impact.

The estimate is the best case scenarios explained the lead author, Professor Jason Box from the National Geological Survey of Denmark and Greenland (GEUS).

“It is a very conservative rock-bottom minimum. Realistically, we will see this figure more than double within this century,” he said. “In the foreseeable scenario that global warming will only continue, the contribution of the Greenland Ice Sheet to sea level rise will only continue increasing. When we take the extreme melt year 2012 and take it as a hypothetical average constant climate later this century, the committed mass loss from the Greenland Ice Sheet more than doubles to 78 cm.”

He added that it needed to be remembered the study only examined the situation of the Greenland Ice Sheet and does not take into account the mass loss from Antarctica or other glaciers around the world.

Professor Box said: “The ice flow models are not ready in this area. This is a complimentary way of calculating mass loss that has been lacking.

“In order to get the figure that we have, we had to let go of the time factor in the calculation. But our observations suggest that most of the committed sea level rise will occur this century.”

The researchers have looked at changes in the so-called snow line of the ice sheet – the boundary between areas of ​​the ice sheet that are exposed to net melting during summer and the areas that are not. The ice does not melt equally all over the surface but primarily along the edges at the warmer lower elevations. Further up the ice sheet, it is too cold for net surface melting to occur even in summer. The boundary between melting and no melting, the snow line, is set by the line where the upper layer of winter snow does not melt away in summer but remains on top, nourishing the ice sheet.

The snow line varies from one year to the next, depending on the weather conditions. A hot summer may mean that the boundary moves further up the ice sheet, thus increasing the melt area and with it the amount of ice melting from the surface that year. In colder years, the melt area can decrease, pushing the snow line down towards the ice edges allowing less mass to be lost.

It concluded if the whole world stopped burning fossil fuels today, the Greenland Ice Sheet would still lose about 110 quadrillion tonnes of ice leading to an average of global sea level rise of at least 27 centimetres.

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