New studies: Oceans could rise higher, faster than expected
Climate change could lead to sea level rises that are larger, and happen more rapidly, than previously thought, according to a trio of new studies that reflect mounting concerns about the stability of polar ice.
In one case, the research suggests that previous high-end projections for sea level rise by the year 2100 — a little over 3 feet — could be too low, substituting numbers as high as 3 feet at the extreme if the world continues to burn large volumes of fossil fuels.
“We have the potential to have much more sea level rise under high emissions scenarios,” said Alexander Nauels, a researcher at the University of Melbourne in Australia who led one of the three studies. His work, co-authored with researchers at institutions in Austria, Switzerland and Germany, was published Thursday in Environmental Research Letters.
The results comprise both novel scientific observations — based on high resolution seafloor imaging techniques that give a new window on past sea level events — and new modeling techniques based on a better understanding of Antarctic ice.
The observational results examine a similar time period — the close of the last Ice Age a little over 10,000 years ago, when seas are believed to have risen very rapidly at times, as Northern Hemisphere ice sheets collapsed.
Off the Texas coast, researchers looked at so-called drowned reefs with stepped regions.
André Droxler, one of the authors of the study in Nature Communications and a researcher at Rice University, thinks the reefs are structured the way they are because they formed when sea level was rising by tens of millimeters annually, far beyond the current rate, roughly 3 millimeters per year. The study concludes there were multiple bursts of fast sea level rise during the last ice age— and implies the future could hold something similar.
Meanwhile, in the Southern Hemisphere, a team of scientists examined ancient iceberg “plough marks” etched deep into the seafloor near Antarctica. The results were published in the journal Nature on Wednesday.
What’s critical about the markings, explains lead study author Matthew Wise of the University of Cambridge, is their maximum depth, which suggest fast retreat and potentially fast sea level rise.
The final study, released Thursday morning in Environmental Research Letters, used five “shared socioeconomic pathways” that analyze possible futures for global society and its energy system, and resulting climate change, over the course of this century.
The research combined these scenarios with tools to project future sea level rise in light of recent science suggesting that Antarctic ice in key regions could collapse relatively rapidly.
In one scenario assuming high fossil fuel use and strong economic growth, the study predicted seas could rise by as much as 4.33 feet on average — with a high-end possibility of 6.2 feet — by 2100. That includes possibly rapid sea level rise as high as 19 millimeters per year by the end of the century. These numbers are considerably higher than high-end projections released in 2013 by the Intergovernmental Panel on Climate Change.