June 13, 2018

Expert reaction to research on Antarctic ice loss and sea level rise

A new climate assessment to be published in Nature combines multiple satellite surveys of Antarctica to create the most complete picture of ice loss to date.

Dr Andy Smith, glaciologist at the British Antarctic Survey, said:

“This is a comprehensive study that brings an up-to-date assessment of how much the Antarctic Ice Sheet is changing and how much it’s contributing to sea level rise.  The last assessment was published in 2012, so this study brings it up to date by including the most recent new observations.

“It shows that the overall trends seen previously have continued over the most recent 5 years. Loss of ice from West Antarctica, in particular, has continued to increase, as has that from the Antarctic Peninsula. In East Antarctica the picture is less clear and there still seems to be no major overall change that can be detected, although there is a lot of variability in the measurements there.

“The result that is most interesting is how West Antarctic continues to lose more and more ice, adding increasingly to sea level. This emphasises the importance of continued efforts to understand the ice sheet there, such as the recently-launched joint UK-US International Thwaites Glacier Consortium.”

Prof Martin Siegert, Co-Director of the Grantham Institute, Imperial College London, said:

“Satellite observations offer an ability to sample large spaces, but they have been restricted to relatively modest time periods – until now. Satellites have been measuring the surface of Antarctica with high accuracy for 25 years, which is enough time to begin to see trends in any changes. The outcome is deeply concerning. Not only is the ice sheet responding to global warming (mainly but not entirely from ocean heat) by losing mass, the rate of mass loss has increased since measurements began back in 1992.

“Unfortunately, we appear to be on a pathway to substantial ice-sheet loss in the decades ahead, with longer term consequences for enhanced sea-level rise; something that has been predicted in models for some time. If we aren’t already alert to the dangers posed by climate change, this should be an enormous wake-up call. Antarctic is being affected by global warming, and unless we curtail our CO2 emissions within the next decade, and have a zero carbon economy within a few decades, we will be locked into substantial global changes, including those in Antarctica and the Southern Ocean.”

Dr Kate Hendry, Reader in Geochemistry at the University of Bristol, said:

“The IMBIE team compilation allows us to assign the most robust and up to date number for ice loss from Antarctica. Whilst there’s still considerable uncertainty about East Antarctic mass balance, it’s increasingly clear that ice loss from West Antarctica has accelerated in the last two decades. A lot of this acceleration is likely due to interactions between the oceans and ice shelves.

“This ice loss will have important implications for sea level but will also have knock on effects for ocean chemistry and marine ecosystems. We’re understanding more and more about how glaciers and ice sheets impact marine algae that feed the rich ecosystems along the West Antarctic Peninsula. Meltwaters release key nutrients into the water, as well as cold, fresh waters that influence water density and circulation. If we’re to understand the oceanographic changes that we’re already seeing in these sensitive regions we’re really going to need robust long term records – such as this – that capture the variability of the system. We can achieve a big picture view by coupling these observations with the results of marine long term monitoring programs – but it’s critical that we keep all of these long term observing systems going even in the face of funding challenges.”

Dr Twila Moon, Research Scientist at the National Snow and Ice Data Center, University of Colorado, said:

“The power of this research is that is brings together independent methods and results from a collection of different teams throughout the world. This increases the confidence is the results and provides a key resource for understanding Antarctic ice loss over the last several decades.”

“This research is further confirmation that Antarctica is losing ice at an increasingly fast pace. While changes in East Antarctica continue to be small, and are the most difficult to pin down, the dramatic changes across the Antarctic Peninsula and West Antarctica are driving the train. Continued ice loss in Antarctica is of great concern for humanity, affecting coastal communities, people, and infrastructure. The good news is that limited climate change can slow the rate of ice loss, and there are many proven actions that can reduce climate change and be implemented immediately. The time is now for all of us to act.”

“The researchers point out several lines of continued study that will narrow the range of ice loss estimates. The agreement across methods is already at a point where we can be very confident that the overall results – that Antarctica is losing ice, and the pace is speeding up – are final. Continued work will help to determine more precisely the quantity of ice loss, which will help improve forecasts of sea level rise around the globe.”

Prof Chris Rapley, Professor of Climate Science at UCL, said:

“The paper provides a valuable synthesis of the current state of knowledge of the mass balance of the Antarctic ice sheet.

“Data are provided for the ice sheet overall, and for three regions: the Antarctic Peninsula, West Antarctica and East Antarctica over the period 1992 to 2017.

“It brings together independent estimates from satellite altimetry, satellite gravimetry, and estimates of the inflow and outflow of ice.

“It confirms previous evidence of a substantial acceleration of ice loss over the period – amounting to a factor ~3 for West Antarctica.

“This is of concern, since the underside of the ice in West Antarctica (and some areas of East Antarctica) slopes downward away from the coast, with the possibility that the discharge may become unstoppable as the ice front retreats.

“So whilst Antarctic ice loss currently makes a relatively modest contribution to the observed 33cm/C rate of of global mean sea level rise – compared with thermal expansion and the loss of ice from Greenland and mountain glaciers – this may change in the future.

“In 2005 at the Exeter conference on ‘Avoiding Dangerous Climate Change’ I was quoted as suggesting that the “Slumbering Giant seemed to be awakening”.

“This paper suggests it is stretching its limbs.”

* ‘Mass balance of the Antarctic Ice Sheet from 1992 to 2017’ by the IMBIE team published in Nature on Wednesday 13 June 2018. 

Declared interests

None received.