In a new study released in Nature this week, the news is quite bad on the rate of ice melt of the massive Greenland ice cap. Newest measurements on the speed, volume and mass of melt are all pointing toward the worst-case scenarios being realized for Greenland-linked sea level rise by the end of the century. Here is a view from NASA’s Jet Propulsion Laboratory.
In this long-term study, a team of 96 scientists representing 50 organizations have completed the most thorough study on ice mass loss ever done. The study covered a period from 1992 to 2018. The team conducted and combined 26 surveys over this period, computing measurements on the ice sheet’s volume, flow, and even its mass loss impact on gravity (the latter measurement of gravity is another physical calculation of mass and mass loss). The study included precise satellite survey data from 11 different satellites.
The sum total of ice loss by last year in the study shows Greenland has lost 3.8 trillion metric tons of ice since 1992. Each metric ton is the equivalent of 2,206 pounds, rather than our ton of 2,000 pounds. This volume of freshwater ice melt has added, by itself, 10.6 millimeters of sea level rise during this period, in addition to other sources of freshwater glacial ice melt and the expansion of water volume caused by the oceanic warming.
Most troublesome is the rate of melt has gone from 33 billion metric tons per year in the 1990s to 254 billion metric tons per year in this last decade. That is an astounding seven times greater rate of melting over this period.
If you can visualize the ongoing “sunny day flooding” that is already rapidly increasing along many coastlines due to sea level rise, it shouldn’t be that difficult to gauge the scope of future exacerbation of this coastal crisis. As a sidebar, the following story via the Canadian Broadcasting Corporation and NPR catalogs the serious recent increase in King Tides flooding in the Florida Keys.
Among the other variables I’ve mentioned, the increase in Greenland melt rate is a certain significant contributing factor in this kind of flooding. Remember, we’re still relatively early in this process. Here is a video sourced from climate.nasa.gov and NASA’s JPL.
By the way, if you take the time to read the credits at its finish, you’ll find there is a contribution to this study from the University at Buffalo (UB recently hired an accomplished glaciologist from the NASA Goddard Center as part of expansion of its role in climate change study, serving its mission as a growing public research university).
Greenland’s ice cap stores enough frozen water to raise global sea levels by more than 20 feet if all of it melted. Knowing how much of this shrinking ice cap is going to melt will be critical. Study lead author Professor Andrew Shepherd at the University of Leeds provided perspective for Phys.org, a leading web news service for science and technology. In 2013, the Intergovernmental Panel on Climate Change (IPCC) predicted that global sea levels will rise by 60 centimeters by 2100, putting 360 million people at risk of annual coastal flooding. But this new study shows that Greenland's ice losses are rising faster than expected and are instead tracking the IPCC's high-end climate warming scenario, which predicts 7 centimeters more.
Professor Shepherd said: "As a rule of thumb, for every centimeter rise in global sea level another six million people are exposed to coastal flooding around the planet."
"On current trends, Greenland ice melting will cause 100 million people to be flooded each year by the end of the century, so 400 million in total due to all sea level rise."
Half of the melting and mass loss is tied to surface melting tied to polar latitude warming, which runs at about twice the rate of the rest of the globe. The other half is due to oceanic warming, which melts more of the peripheral ice at its edge and beneath the ice.
Multiple satellite measurements continue to provide more precise data than was seen to be possible a few decades ago. In fact, the extraordinary warmth in this region this year will be showing up as an even greater acceleration in the rate of melting this year compared to just a few years ago. Whether this spike is temporary remains to be seen.
As has been written in many articles elsewhere, and in my own columns, it appears the primary way to turn the rate of ice mass loss down is for humankind to take more drastic steps in reducing greenhouse gas emissions. Most climate scientists, physicists and oceanographers do not yet feel we have passed a “tipping point” but it’s probable without major changes we are drawing closer to such a theoretical point.