Nagging sea level rise mismatch solved

Although we've wanted to quantify each contributor to sea level rise, it should be no surprise that the numbers don’t always add up perfectly.So researchers have turned to a process called “closing the budget”—working on adding estimates of ice mass loss, thermal expansion of seawater, and change of water storage on land, and then comparing that to estimated sea level trends from tide gauges and satellites. The sum of all the sea level change factors is 1.52±0.33 millimeters per year—a comfortable match.Estimates also match within error bars for 1957-2018 and 1993-2018, but these periods see accelerating sea level rise, with rates increasing to about 1.78 millimeters per year and then 3.35 millimeters per year.For the first half of the 20th century, water added to the oceans accounts for over 80 percent of total sea level rise, although dam-building eats into that number in the second half of the century. But even though the number of tide-gauge and land-elevation records vary, the researchers found that each ocean basin’s sea level rise budget matched observations back to 1960.There are some interesting differences between basins, with slower sea level rise in the East Pacific than in the South Atlantic, for example. But at the same time, downward movement of the seafloor (a relic from the ice age) had the opposite effect, canceling out the gravitational weirdness.Overall, the researchers write, “Closure of the twentieth-century sea-level budget, as demonstrated here, implies that no additional unknown processes, such as large-scale deep-ocean thermal expansion or additional mass loss from the Antarctic Ice Sheet, are required to explain the observed changes in global sea level.