Antarctica discovered contributing to sea-level rise—still!

Dinner in snow kitchen. McMurdo Station, 2010

Sea-level rise (SLR) is a stealthy impact of global warming, showing up unwelcome as storms have hit the coastlines of the globe. There's more to come. 

I’ve often blogged on how Antarctica influences sea level rise and the uncertainties about how much (11/5/2017; 1/8/2017).

In a recent letter to the international journal Nature, Slater and Shepherd (1) have drawn attention to new data on ice mass loss from Antarctica detected by satellite measurements over the ten-year period 2007-2017. Converting ice mass to SLR they observed that the rate of Antarctica’s contribution to SLR has increased 40% in the past few years—it’s accelerating. 

They compared the SLR contribution for Antarctica they computed against the projected SLR that the Intergovernmental Panel on Climate Change (IPCC) issued in its last report in 2013 (AR5; 2). What they note is that the SLR they measured follows the AR5 predicted curve for the business-as-usual, worst-case circumstance. This is when no real effort is made by nations to curb greenhouse gas emissions.

The unsettling conclusion is that the worst-case predicted curve computed five years ago is now matched by observations. The AR5 report projects a worst-case 980 millimeters (38 inches) of SLR by the year 2100. Of this Antarctica is on track to contribute 151 millimeters (6 inches). 

Slater and Shepherd note that as little as 10 centimeters (100 millimeters; 4 inches) of storm surge results in floods in many coastal locations. We’ve all seen this on the news. 

Taken in total, over 3 feet of SLR predicted for the world will result in coastal retreat of beaches, cliffs, buildings, towns, and infrastructure. It could be even worse. The prediction curves do not account for catastrophic events like Antarctic ice cliff collapse that I’ve covered in previous blog entries listed above. That could result in doubling SLR to 6 feet by 2100. 

Santa Barbara, my city, is preparing for a century of SLR with the adaptation and mitigation that this will require (When-will-sea-level-rise-swallow-Santa-Barbara?).

1. Antarctic ice losses tracking high; Nature Climate Change, | VOL 8 | DECEMBER 2018 | 1024–1026.

2. Church, J. A. et al. in Climate Change 2013: e Physical Science Basis (eds Stocker, T. F. et al.) Ch. 13 (IPCC, Cambridge Univ. Press, 2013).