Rising Sea Levels -June 2019

Scientists say sea-level rise is already happening. The question is how high will the oceans rise in the next few decades and what can we do about it?

by: John Stanton

photography by: Nicole Harnishfeger

The tide gauge sits unobtrusively just off Steamboat Wharf. In a time of ongoing political arguments about climate change, the gauge is a silent sentry whose work is non-partisan. It simply measures and records water levels. This happens all along the coast of the United States.

The work is overseen by the National Oceanic and Atmospheric Administration and has been going on for more than a century in one form or another. The Nantucket tide gauge was first installed in 1963. The present version was installed in 1990. In any discussion of climate change and sea-level rise, in any discussion of what this town and this island should be preparing for over the next 50 years or so, the data recorded by what NOAA lists as tide gauge 8449130 is good a place as any to begin.

Because numbers, sometimes, have consequences.

On Jan. 4, 2018, a nor’easter called Winter Storm Grayson hammered the island. At the storm’s height, the tide gauge measured 3.8 feet above what is called the mean higher high-water mark (MHHW). According to NOAA’s glossary of terms, MHHW is the average of what is called the higher high water for each tidal day, observed over a 19-year time period.

Those numbers played out this way: Flood waters cut off Brant Point lighthouse so that it appeared to be on an island of its own. The water was nearing three feet deep as it rolled up Easton Street. It flooded the three buildings that make up Coast Guard Station Brant Point and put its floating dock under hip-deep seawater.

When a storm and flooding are predicted, the Coast Guard spends about two days cleaning out the basements of its buildings and moving the equipment to an upper floor. Sometimes, faced with a storm, a decision is made to move the motor-rescue boats over to the Nantucket Boat Basin, but this time they stayed at the dock. Soon, it was obvious that getting personnel down Easton Street in a vehicle was going to be a problem. The answer was to run a boat over to the Town Pier to pick up enough off-duty personnel to bring the Coast Guard to full staff.

Editor’s Note: this is an excerpt from a multi-part series looking at predicted sea-level rise and increases to the number and severity of coastal storms over the next 30 to 50 years, and how the town is preparing for that future. You can follow the story in the pages of The Inquirer and Mirror beginning in June, or online at http://www.ack.net

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