Thursday, February 06, 2020

The Increasing Rate of Rising Seas

The rate at which sea levels are rising is increasing on both the east and west coasts of the United States. This increasing rate can clearly be seen in the 2019 data from NOAA tide stations.

NOAA operates tide stations on all U.S. coasts in order to measure and record data on tide heights, current speeds and current directions. Data from 32 of those tide stations, positioned around the coast of the USA, has been used by the Virginia Institute of Marine Science (VIMS) to explore the latest trends in sea level movements. These measurements show that the rate of sea level rise is accelerating around the United States.

The VIMS Sea Level Report Cards includes two interactive maps visualizing the Rate of Rise/Fall and the Rate of Acceleration/Deceleration measured at 32 tide stations during 2019. These two values show year-to-year changes in sea level relative to the land at each station. Both the rate of sea level rise and the rate of acceleration of sea level rise increased in 2019 on the East, Gulf and West coasts. In Alaska both the rate of rise and the acceleration of sea level rise decreased.

It is clear from the data that during 2019 nearly every coastal location in the U.S. experienced an upturn in both sea levels and the rate at which those levels are rising. The only exceptions were the Northeast Coast and Alaska. Geologic uplift from tectonic plate movement means that the land in Alaska is rising faster than the rising sea. This means that Alaska is one of the few places on Earth which isn't seeing relative sea level rise.

You can view Sea Level Trends over the long term on NOAA's own interactive map of Sea Level Trends. NOAA's map uses scaled arrows to show the long-term rising sea level trends at tide gauges around the United States, based on the historical data from each tidal gauge.

NOAA's long-term sea level map shows a similar pattern to the 2019 VIMS data. Sea levels are rising around the whole of the United States, except in Alaska. The Gulf Coast and East Coast are also seeing bigger rates of sea level rise than the West Coast. Land on the eastern seaboard is gradually sinking, which is why the West Coast is seeing relatively smaller levels of sea level rise than the Gulf and East Coasts.

NOAA is reporting that the increasing rate of sea level rise means that the the worst case scenarios in sea level change are becoming more likely. These worst case scenarios predict an increase of up to 8.2 feet by the end of this century, compared with 2000 levels. This level of sea level rise will have a devastating impact on the United States, where nearly 40% of the population live near the coast.

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