New Research May Solve a Puzzle in Sea Level’s Rise
A team of researchers reported Wednesday that the ocean did not rise quite as much as previously believed in the 20th century. They proposed a seemingly tiny adjustment that could make a big difference in scientific understanding of the looming problem of sea-level rise.
Instead of rising about six inches over the course of the 20th century, as previous research suggested, the sea actually rose by approximately five inches, the team from Harvard and Rutgers Universities found. The difference turns out to be an immense amount of water: on the order of two quadrillion gallons, or enough to fill three billion Olympic-size swimming pools.[one_fourth]
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If the findings stand up to critical scrutiny by other scientists, they could help to resolve a longstanding conundrum in climate research. For years, when experts added up their best measurements of melt water from land ice and of other factors causing the sea to rise, the numbers fell a bit short of the rise that had been recorded at harbors around the world.
If the harbor measurements were right and the ocean really had two quadrillion gallons of extra water, where was it coming from? The discrepancy set off an intensive search for additional ice that might be melting from glaciers and ice sheets, or extra heat that might be causing ocean water to expand, and so on. To some scientists, the answers that emerged were never entirely satisfactory.
Now, in a new paper published Wednesday by the journal Nature, the Harvard and Rutgers scientists applied advanced statistical techniques to the measurements taken at harbors. They found that previous research on that record had slightly overestimated the amount of sea-level rise that occurred in the 20th century. With their downward revision, the harbor record now matches the other records rather neatly.
“If it’s right, it’s pretty important,” said Peter U. Clark, a geologist at Oregon State University who studies sea level but was not involved in the new research. John A. Church, a scientist with Australia’s national scientific organization and a prominent researcher on sea level, echoed that view, but both men said they would like to see more details of the research before passing final judgment.
The main significance of the paper, if it holds up, may be to increase scientists’ confidence that they understand precisely why the ocean is rising — and therefore shore up their ability to project future increases.
