Though it is an undisputed fact that rising sea levels from melting glaciers and ice sheets pose an increasing threat to coastal communities worldwide, a new analysis of high-resolution satellite observations takes a major step forward in assessing this risk by confirming theoretical predictions and computational models of sea-level changes used to forecast climate-change-driven impacts.
“Using sea-surface-height observations from satellites in the way we have independently verified observations of Arctic and Greenland ice-mass loss allows us to tease apart contributions to global sea-level rise from individual ice sheets and glacier systems,” said Sophie Coulson, a postdoctoral researcher in fluid dynamics and geophysics at Los Alamos National Laboratory.
The Harvard alumna is the lead author of a paper published last Thursday in the journal Science on detecting the ‘fingerprint’ of sea-level change attributable to the melting of the Greenland ice sheet. The work validates almost a century of sea level science and helps solidify confidence in models predicting future sea level rise.
Accurately predicting regional patterns of sea-level change is absolutely central to understanding the impacts of future climate change and forecasting hazards. Theoretical models and computer simulations can predict sea level changes as ice sheets and glaciers melt. As this melting continues, and the water is redistributed around the global oceans, sea level does not rise uniformly.
Since every glacier and ice sheet has a unique pattern of sea-level change, they have come to be known as sea-level fingerprints. But despite over half a century of research, these fingerprints have never been unambiguously detected, observed Coulson whose search focused on satellite observations of sea-surface height in the oceans surrounding the Greenland ice sheet over the last three decades.
The dominant effect in this region is that as the Greenland ice sheet loses mass, it exerts less gravitational attraction on water in the open ocean and so water migrates away from the ice sheet. This results in a lowering of sea level near Greenland, but progressively higher levels of sea-level rise outside the region.
Detection of the patterns has historically been hindered by the lack of sea-surface-height measurements around polar ice sheets and the variability of shorter-timescale processes, such as changing currents and ocean density. The research team on the Science paper took advantage of processed satellite observations that extend to much higher latitudes than previously possible, where the fingerprint signal is the largest.
The team processed this satellite data using a powerful new technique to remove the variability due to ocean dynamics. The new study confirms the accuracy of the geophysical predictions of sea-level change and adds confidence to projections of sea level rise across the next decades and century.
“Ocean level projections, urban and coastal planning — all of it — has been built on the idea of fingerprints,” said the study team member Harvard geophysicist Jerry X. Mitrovica, the Frank B. Baird Jr. Professor of Science in the Department of Earth and Planetary Sciences.
“That’s why fingerprints are so important. They allow you to estimate what the geometry of the sea level changes is going to be like… so we now have much more confidence in how sea level changes are going to evolve…. If fingerprint physics wasn’t correct, then we’d have to rethink all modern sea level research.”
Now that the first sea level fingerprint has been detected, the question with the biggest global implications is now where does this all leads. “More detections will come,” Mitrovica said. “Soon the full power of fingerprint physics will be available to project sea level changes into the next decade, century, and beyond.”