Tide Gauges Needed for Research Are Often Victims of Storms

Boats scattered onto shore by Hurricane Sandy in Monmouth Beach, N.J., in 2012. (Steve Nesius/Reuters)

(Click to enlarge) Boats scattered onto shore by Hurricane Sandy in Monmouth Beach, N.J., in 2012. (Steve Nesius/Reuters)

As the waters of Hurricane Sandy rose higher and higher on Oct. 29, 2012, an instrument on a pier at Sandy Hook, N.J., recorded the ominous tidal surge. The reading hit eight feet above sea level, then nine, then 10 – and every few minutes, the gauge faithfully transmitted its readings to a satellite flying overhead.

(From The New York Times / by Justin Gillis) – The reading was closing in on 11 feet above mean sea level when the transmissions suddenly stopped.

The waves of the mighty storm had smashed the government-owned instrument to bits at the moment it was needed most, with the mid-Atlantic shoreline being slammed by a record tidal surge. That was the latest example of a problem that had been plaguing oceanographers and climate scientists for the better part of a decade.

Accurate tidal readings are crucial to understanding individual storms, as well as the long-term risks associated with the rise of the sea. Yet in 2005, when Hurricanes Katrina and Rita hit the Gulf Coast, and again in 2012 with Sandy, the tide gauges that are supposed to record storm surges proved vulnerable themselves.

Rising Sea, Sinking Land
Tide gauges along the East Coast show a long-term increase in relative sea levels, in part because the ocean is rising and in part because areas of the coast are sinking.

 The New York Times Sources: American Geophysical Union; Rutgers University; NOAA; USGS

(Click to enlarge) The New York Times
Sources: American Geophysical Union; Rutgers University; NOAA; USGS

The National Oceanic and Atmospheric Administration, which maintains the gauges, said that nine were destroyed or severely damaged by Katrina and Rita. An astonishing 73 tide stations were damaged or destroyed as Sandy swept across the North Atlantic basin, including ones in Puerto Rico and the United States Virgin Islands.

Ten of the 73 needed reconstruction or major repairs, but the one at Sandy Hook, a long spit of land enclosing Lower New York Bay, took the worst hit.

“We were surprised that the station got washed off the face of the earth,” said Stephen K. Gill, senior scientist of the NOAA division that measures tides and currents. “The wave action tore everything apart.”

Climate scientists say they need precise readings from storm surges if they are to predict how much those will worsen with climate change, and to specify risks to nearby coastal areas. They say the vulnerability of the gauges comes in part from the continuing rise of the sea, which is believed to be caused largely by human emissions of greenhouse gases.

“We know our stations are at increasing risk, because the storm surges ride upon sea level,” Mr. Gill said. So the government has embarked on a long-term program of hardening the instruments against future storms.

During a recent visit to the tide gauge at the Battery, at the lower tip of Manhattan, Mr. Gill noted that the surge of water from Sandy exceeded the measurement limits of the main instrument there. Fortunately, NOAA had a backup system in place that took accurate readings throughout the storm. It pegged the storm tide at the Battery at about 11½ feet above mean sea level, higher than any other storm tide since record-keeping began at the Battery in the 1850s.

Surveys of building damage and the like suggested that the storm tide at Sandy Hook, 15 miles due south of the Battery, was almost exactly the same. But federal scientists would rather have real-time readings, instead of having to rely solely on after-the-fact estimates. A temporary gauge is providing readings at Sandy Hook now, but a permanent, much sturdier tide gauge is in the offing.

At the Battery, too, the government plans to abandon the shack behind a Coast Guard building that houses the tide gauge now, driving its own pilings next to the Staten Island Ferry Terminal to install an instrument that will be able to withstand stronger storms.

And on the Gulf Coast, NOAA has built four superstrong tide stations that it calls Sentinels of the Coast. They are mounted on tough steel pilings driven as much as 80 feet into the seabed, and are designed to stand up to Category 4 hurricanes.

But tide stations that strong can cost $ 500,000 apiece or more, depending on location, which limits how many the agency can build.


Consortium for Ocean Leadership