Zombie Ice
A new name for a known problem grabs the headlines. Will it catalyze action?
The second time I saw the film "Night of the Living Dead" I had nightmares for a week. There can be something terrifying about zombies - their apparent immortality (or undeadness), and unyielding destructiveness.
Fear and dread of the undead has now given rise to a new term that might serve to heighten awareness of the threat of sea level rise: Zombie Ice. The metaphor may seem like hype, but might the phrase serve a useful purpose?
Succinct and memorable names have been important in riveting popular attention on environmental issues. From acid rain to the ozone hole to the polar vortex to El Niño, the ability to capture an issue in two words has been important in focusing national and international attention. You can find editorial or humorous cartoons on all four of those issues, a sure sign that they have penetrated the public mind. Zombie Ice is too new a term to have appeared in cartoons, but don't be surprised if we see some soon.
The acid rain and ozone hole issues have been at least partially resolved through international cooperation driven by solid science. Maybe catchy names helped a bit by conveying something of both the cause and the danger of those issues to the general public.
Understandably, current climate change reporting tends to focus on today's environmental disasters - major storms, floods, droughts, and fires. On average, the increase in these disasters is being driven by climate change, but any one story about any one event tends to be couched in wording suggesting that it might be related to climate change, or might not.
Compared with the immediacy of disaster reporting, a predicted increase in sea level of about 10 inches by 2050 may not sound very frightening, and does not seem to have conveyed the kind of immediate threat that would lead to immediate action. Earlier essays here have described some relatively successful efforts to thwart both major storms and projected sea level rise at four locations in Europe, and compared these with the general lack of acknowledgement of, and preparation for, sea level rise in the U.S.
So maybe "Zombie Ice" will be the phrase that brings immediacy to what is likely to prove, in the long run, the most important climate change outcome: the inevitable rise of sea level. Maybe Zombie Ice is just what we need - as a media term anyway.
So what is Zombie Ice and what does it mean for our environmental future?
The phrase apparently first appeared on August 29 in an article by Seth Borenstein of the Associated Press. That article circulated rapidly through media news outlets (see Sources below) and by August 31 had even reached our local newspaper here in the seacoast of New Hampshire, where the full story captured all of the space above the fold on page 7.
Zombie Ice is ice that is already unsustainable under current climate conditions - ice that will melt yielding liquid water to the oceans and causing sea level rise, even without any further increase in global temperatures.
We can think of the massive, truly massive, amounts of water captured or stored in the ice caps of Greenland and Antarctica as being currently "dead" to the global water cycle, but that massive catastrophe-in-waiting is also, inevitably, slowly, rising again, zombie-fashion.
It is fascinating to watch how the kind of dry, precise, totally factual presentation of scientific results in professional papers, purposely devoid of inflammatory adjectives, gets turned into the grist of popular media presentations. Needless to say, the authors of the scientific paper cited below did not coin the term Zombie Ice. The actual article on which the media reports were based is a carefully documented study of rates of ice loss and replenishment on the Greenland ice sheet.
In that original paper, the authors note that modeling the dynamics of ice flow, iceberg calving and meltwater runoff from the massive glaciers that ride atop Greenland is a complex and still evolving area of science, making accurate and precise predictions of water loss to the oceans difficult.
In response, they offer an alternative analysis using a mass-balance approach. Using remote sensing images, the authors mapped the area of the ice cap covered in snow in summer and compared that with total ice extent (the difference being ice that is uncovered and exposed to the atmosphere). Applied to all of the hundreds of glaciers that make up the full ice sheet, this ratio of covered ice to total ice is a good predictor of measured net water loss from each. The higher the fraction of exposed ice, the larger the net loss of water each year.
This measured relationship can also be used to determine how much ice would have to be lost to bring the net balance of water to zero (ice formation equal to melt). That quantity is the Zombie Ice. Even with no further change in climate, the water in Zombie Ice is already committed to the oceans.
Using average numbers for the period 2000-2019, the amount of Zombie Ice now held in Greenland is enough to raise sea level by 27.4 centimeters, or more than 10 inches.
So Zombie Ice tells us that, even without any further warming, a 10 inch rise in sea level is already inevitable, and this just from ice loss in Greenland.
The researchers made some conservative assumptions in doing these calculations. For example, they applied the method separately to hundreds of subregions across the island. A single calculation for the entire ice cap would have yielded a 20% higher estimate of the total amount of Zombie Ice.
The use of average water loss values for the years 2000-2019 is also conservative. Rates of ice loss from Greenland over that 20 year period have been trending upward, and global average temperatures, important in determining snow cover and melting, are going to increase across the century no matter what steps we take now.
If the average conditions across the 21st century are more like the extreme ice melt year of 2012 described in the paper, then the total amount of Zombie Ice is enough to raise sea level by 78.2 cm or more than 30 inches.
Where the uncertainty lies in this analysis is in timing. This is an equilibrium calculation, not a dynamic one. Current thoughts are that it might not be until 2100 or even 2150 before all of this Zombie Ice actually melts. I take no comfort in that. Someone will be here then, maybe even my grandchildren (in 2100), and they will have to deal with this. But, unlike the dynamic models of ice flow, this approach does not have a predicted timeline.
In an earlier essay, where we are headed in terms of sea level rise was presented in the context of previous geologic eras with similar global temperatures. Employing the kind of equilibrium thinking used to calculate Zombie Ice here, another recent paper cited in that essay noted that the last time the Earth was 2 degrees Celsius warmer than now (a conservative estimate of warming by the end of the century), sea levels were higher by 20 meters, or more than 60 feet!
So sea level will rise, and by a lot. The question is how fast. It is the incredible inertia in the climate system provided by all that ice in Greenland and Antarctica, that will melt only slowly, that is preventing a much more rapid rise in sea level. This makes the Zombie Ice calculation seem conservative in the extreme, and also makes the case that understanding what controls rates of ice loss from those two massive ice sheets should be a high priority for climate change research.
Another theme in these essays has been that climate change is going to be expensive. Either we can spend money now to reduce carbon emissions and slow the rate of change, or we can spend money on preparedness to respond to rising sea levels and the more intense storm surges that will inevitably follow. The third choice, of course, is to wait for the disasters to happen, and then spend the money to salvage what remains (and that is as far as we go into politics, policy, and economics in these essays!).
And note this as well - we have only dealt here with the Zombie Ice on Greenland. How big are the zombies waiting for us in Antarctica?
Iconic names may have helped raise awareness of issues like acid rain and the ozone hole that have been addressed through the kind of science-based, international cooperation that we have failed to achieve so far on the climate issue.
Maybe the specter of Zombie Ice can achieve what 30 years of careful IPCC study and synthesis, and recurring international gatherings, has failed to do - generate increased acceptance of the inevitability of climate change and sea level rise, and motivate coherent action in response.
Acknowledgement: Thanks to Caitlin Aber for bringing Zombie Ice to my attention!
Sources
The original scientific article that has led to the term Zombie Ice is here:
https://www.nature.com/articles/s41558-022-01441-2#code-availability
The paper on climate and sea levels in older geological eras is here:
https://www.pnas.org/content/115/52/13288
Media stories using the Zombie Ice name include:
https://abcnews.go.com/Politics/wireStory/zombie-ice-greenland-raise-sea-level-10-inches-89003077
https://www.cbc.ca/news/science/zombie-ice-greenland-1.6566437
https://news.yahoo.com/zombie-ice-greenland-raise-sea-145917647.html
The projection of about a 10 inch rise in sea level by 2050 is from the science report out of the 6th assessment of the Intergovernmental Panel on Climate Change:
https://www.ipcc.ch/report/ar6/wg1/downloads/report/IPCC_AR6_WGI_SPM.pdf
p.22. Note that all of the different policy options tested in this report result in very similar projections for sea level rise by 2050 - this will happen no matter what we do. Note also that projected sea level rise by the year 2300 might be anywhere from 6 to 20 feet for the highest emission scenario.
The image of the Greenland ice cap is from:
https://earthobservatory.nasa.gov/images/147728/shrinking-margins-of-greenland
The image used with the definition of ablation is from:
https://climate.nasa.gov/news/3206/nasa-studies-find-previously-unknown-loss-of-antarctic-ice/