New sea level estimates show strong, recent acceleration

Enlarge / Flooding under clear skies is an increasing reality for coastal communities. (credit: NOAA)

Humanity has trillions of dollars of infrastructure within a meter of the current sea level. Given that, it's rather important that we understand how long that sea level will stay at its current measurement and how quickly it will change. Unfortunately, we don't have very good data for this. Modern satellite records of sea level only go back a few decades; before that, we have about a century of tide gauge readings.

Unfortunately, those tide gauges weren't uniformly distributed throughout the globe. And, in many cases, the solid ground they are attached to has been shifting slightly. Attempts to account for these and other factors has produced a variety of estimates of past sea level rise, most being fairly similar but differing in a number of ways. Now, the latest attempt suggests that sea level rose more slowly early last century-which means it has accelerated dramatically in recent decades.

Doing the books

Ocean levels are rising due to a combination of added water (from the melting of glaciers and ice sheets) and the fact that water expands as it warms up. But that's not the only factor at play. Humanity has trapped a lot of water behind dams, and it has taken lots of groundwater and placed it back into the regular cycling of evaporation and precipitation. Collectively, these factors create what's called a "budget" for the sea level. If we knew how much they changed, we should have a good estimate of ocean levels.

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