December 10, 2019

expert reaction to research on Greenland ice loss

Research, published in Earth System Science Data and Nature, reports that Greenland ice loss is rising faster than expected.

This roundup accompanied an SMC briefing.

Prof Robert Marsh, National Oceanography Centre, University of Southampton, said:

“The IMBIE Team provide a timely update on the startling increase in annual mass loss from the Greenland ice sheet. This major synthesis reveals how – over the lifetime of five IPCC reports to date – Greenland’s contribution to global-mean sea level rise has increased faster than all others (thermal expansion, other glaciers, Antarctica). Particularly revealing are the relative and varying influences of regional atmospheric and ocean warming on the rate of loss. It is critical to monitor the great ice sheets of Greenland and Antarctica, and a matter of urgency that scientists better understand the complex processes that are driving the dramatic mass losses of Greenland in particular.”

Dr Louise Sime, climate scientist at British Antarctic Survey says:

“This finding should be of huge concern for all those who will be affected by sea level rise.  If this very high rate of ice loss continues, it is possible that new tipping points may be breached sooner than we previously thought.”

Dr Bethan Davies, senior lecturer in Physical Geography at Royal Holloway, University of London, said:

“The IMBIE team are a very well-respected group of scientists who release regular updates on the changing mass balance of the Greenland and Antarctic ice sheets. This method, which combines and compares multiple data sources, is the most accurate method available for analysing changes in these two ice sheets.

“The research highlights how over the last decade, Greenland has become a major source of sea level rise, rivalling that from global glaciers, with increased surface melt, and increased glacier flow speeds, driving the ice loss.  It’s an update on work that has been coming from Greenland for the last few years and shows that ice loss from Greenland is increasingly important in terms of global sea level. Importantly, it shows the that the Greenland Ice Sheet is on a trajectory that could lead to significant volumes of ice loss and sea level rise over the next 80 years.”

Dr Andrew Sole, Lecturer in Physical Geography at the University of Sheffield, said:

“Measuring the mass of something as large as the Greenland Ice Sheet is extremely difficult and complicated. The strength of the IMBIE study is that they have combined many different methods, models and satellite measurements over a common time period and area to create a dataset that minimises the impact of the individual uncertainties.

“The IMBIE team’s findings have confirmed that the Greenland Ice Sheet has been losing mass since the early 1990s, and that, despite some variability, the overall rate of mass loss has increased significantly. Their use of multiple mass balance methods has enabled different types of mass loss to be measured (surface melt and runoff vs iceberg calving and submarine ice melt), which can help to make more accurate predictions of how the ice sheet might respond to further changes in climate.

“These new combined data show that the ice sheet’s contribution to global sea level rise has mostly been tracking the upper range of the Intergovernmental Panel on Climate Change’s predictions. Even though it has ducked slightly below this in the last few years, initial observations indicate that 2019 was another high melt year across many parts of the ice sheet, suggesting this slight slowing in the rate of ice loss may be short-lived – and we may well remain on course for the IPCC’s worst-case scenario of 67cm of sea level rise by 2100.”

Dr Robin Smith, Senior Research Scientist at the National Centre for Atmospheric Science, University of Reading, said:

“This is the most comprehensive estimate yet of how the whole Greenland ice sheet is changing, requiring an international team of scientists with a wide range of skills. They have drawn together data and understanding from different sources to work out how a complex combination of weather, ocean temperatures and ice flow in different parts of the ice sheet affect how global sea-levels are rising.

“The study shows that loss of ice from Greenland has increased very significantly since the 1990s and is unfortunately following the upper limit of the rate estimated in the last IPCC Assessment. As well as giving us the overall picture of how the ice sheet has changed, data-sets such as these also helps improve our understanding of how different factors work together to produce that picture, so they’re really important from that point of view as well.

“Although this is excellent work, studies such as these must still rely on a relatively short period of observations of the ice sheet, considering the timescales of the ice physics involved and the changes in sea-level we need to be able to predict. This means it’s important that we continue making measurements to monitor how ice sheets are responding to climate change as a vital part of being able to predict the impact of sea-level rise in the 21st century and beyond.”

Prof Jeffrey Kargel, Senior Scientist, Planetary Research Institute, Tuscon, Arizona, said:

“This valuable work by the IMBIE team appears to be very well done. They have carefully combined two different types of data– direct measurements of surface elevation change and measurements of total mass change, which allows the uplift or subsidence of the ice sheet bed to be accounted for. The authors’ results are consistent with what other people have reported, but this work achieves an improved level of accuracy.

“The findings point to sustained but variable melting of Greenland ice. However, they also find that a recent slowdown of melting has taken place in the last few years– despite repeated summer heat waves in Greenland. (The record breaking 2019 heat wave occurred after the period of their data analysis.) What Greenland is experiencing is due to global warming, which accounts for the dominant trend since the 1990s, combined with a natural climate cyclic in the North Atlantic, which appears to work with global warming to alternately speed up and slow down the melting of Greenland ice. 

“In Greenland, most future melting will probably come during hot summers, pooling of lakes on the ice sheet surface then sudden draining of those lakes, causing fast flow (surging) of the major outlet glaciers into the sea, which then melts more ice. We need to better understand the North Atlantic Ocean circulation and attendant effects on climate. The melting of ice in Greenland, especially if it accelerates, can have major influences on the North Atlantic Ocean’s circulation and the climate of adjoining land, including parts of the U.S., Canada, and Europe. These disruptions may have started already. The surging of large Greenlandic glaciers into the sea is probably a dress rehearsal for even faster melting of more glaciers later this century.

“However, the results here do not support sensationalized media and political reports that all of Greenland’s ice will suddenly melt and raise sea level by 7 m (23 feet). That total amount of sea level rise due to melting of most of Greenland’s ice is locked into Earth’s near future due to global warming, but much of that melting will elapse over many centuries and continue for thousands of years. Consequently, the amount of sea level rise that has been occurring will accelerate and plague coastal regions worldwide for centuries.”

‘Mass balance of the Greenland Ice Sheet from 1992-2018’ by the IMBIE team was published across Earth System Science Data and Nature at 4pm UK time Tuesday 10 December 2019. 

Declared interests

None received.