Focus: Shored Up

Shored Up

The accelerating creep of sea level rise.

New U.S. regional sea level scenarios developed by NOAA and partners will help coastal communities plan for and adapt to risks from rising sea levels. This photo shows flooding in Norfolk, Va., on May 16, 2014.

By Bruce Buls, Editor-at-Large

Time was, SLR meant “single lens reflex,” at least to me and many others. That’s a type of camera with detachable lenses and a hinged mirror inside. Now, increasingly, it means “sea level rise.”

It’s an acronym we may get used to because SLR (the wet kind) is upon us and will only rise as the planet continues to warm. Other acronyms to add to your vocabulary include EWL (extreme water level), HTF (high tide flooding) and MHHW (mean higher high water). For mariners, MLLW (mean lower low water) has long been the salient number to keep in mind as that represents the amount of water available to float your boat. Now, as sea levels rise, there’s more of that under your keel.

At the same time, as MHHW goes up, so does shoreside flooding and ultimately inundation. When Hurricane Sandy hit New York and New Jersey in 2012, peak water levels measured by local tide gauges were between eight and nine feet above MHHW at the time.

Tide gauges have been measuring the rise and fall of coastal tides for well over 100 years. There’s one in San Francisco Bay that dates back almost 150 years. Before digitization, tide gauges were large measuring sticks housed inside “tide houses” with pen-and-ink recorders. Now, acoustic sounding tubes and pressure sensors – or newer microwave radar water-level sensors – measure the tidal variations and transmit data directly to National Oceanic and Atmospheric Administration (NOAA) scientists. Satellite telemetry is also used to track water levels.

MHHW is also the level used to visualize the reach of rising waters in NOAA’s Sea Level Rise Viewer, an online tool with maps of the entire U.S. coastline. With the viewer, users can see coastal areas’ current MHHW and then, using a slider, see the effects of rising sea levels in one-foot increments, up to 10'. It’s really quite dramatic, as you move the slider higher, more area turns blue, meaning it’s inundated. It’s under water. The viewer isn’t predicting 10' of SLR specifically but shows it as a possibility and what it would mean. Ten feet, however, is within the higher range of projected SLR by 2150.

The Sea Level Rise Viewer is a companion of the recently released 2022 Sea Level Rise Technical Report from NOAA. This report builds on a similar report from 2017, but with updated data, models and projections. One principal takeaway from the new report is a predicted sea level rise of about one foot between now and 2050. That’s about equal to the SLR of the previous 100 years, so the rate is accelerating.

“Current and future emissions matter,” NOAA Administrator Rick Spinrad said during a video presentation that followed the report’s release, “but this will happen no matter what we do about emissions. If emissions continue at the current rate, it’s likely we see two feet of sea level rise by the end of the century, and that estimate is on the conservative side.”

BALLOONING SLR

SLR is accelerating for three reasons: one, the oceans are expanding as they and the atmosphere are getting warmer; two, the oceans are filling up with more water from melting ice on land; and three, coastlines are generally sinking, a result of compaction and underground extractions of water and petroleum. (Except for Southeast Alaska, which is unique in that sea levels are dropping as the mountains are rising.)

NOAA is the lead agency for this report — a multiagency and academic effort that included NASA, the Army Corps of Engineers, U.S. Geological Survey (USGS), Environmental Protection Agency (EPA), Federal Emergency Management Agency (FEMA), Department of Defense, and Florida International University and Rutgers University.

These groups expect that the report and viewer will be used by coastal communities as they plan for these coming changes and develop mitigation strate-

gies. “We predict a ood regime shift,” said William Sweet, a NOAA oceanographer, “meaning that minor nuisance ooding, especially on the East and Gulf coasts, is likely to become damaging ooding. That extra foot around the country is just going to reach farther inland and be deeper and more severe.

“The tide is going to go where it wants to go,” he said, “so this will also affect areas where salt meets fresh, and saltwater intrusion becomes a problem for aquafers and agriculture.”

Beyond 2050, the report provides various scenarios with a wide range of potential increases. Looking to 2100 and 2150, the report says coastal mean water levels could rise by as much as 7.2' by 2100 and 12.8' by 2150, relative to 2000. Or it could be as little as 1.97' by 2100 and 2.6' by 2150, according to the report. The determinant, of course, is global warming. The warmer it gets, the higher the water. The giant ice sheets of Greenland and Antarctica are especially vulnerable to rising temperatures and contain enough water to raise sea levels by at least 10' by sometime in the next century.

Meanwhile, here in the U.S., in 2022, creeping sea level rise has not yet emerged as a signi cant national issue. Regionally, however, the awareness of SLR and its effects may be more prevalent. Chesapeake Bay, on the shores of Maryland and Virginia, is a “hot spot” for rising tides and sinking lands.

The historical relationship between CO2 concentrations, global temperatures and sea levels is stark when graphically depicted.

In Earl Swift’s 2018 book, “Chesapeake Requiem – A Year with the Watermen of Vanishing Tangier Island,” the author wrote: “Full moons pull water not only over its edges, but straight up through the ground, turning yards into ponds. In fact, the lower Chesapeake’s relative sea-level rise — the one-two punch of water coming up and land going down — is among the highest on Earth, and of all the towns and cities situated on the estuary, none is as vulnerable, none as captive to the effects of climate change, as Tangier.” The legendary watermen who pioneered the blue crab shery face a ooded future and may well become America’s rst climate refugees. Another well-known island farther south, Parris Island, the Marine Corps Recruit Depot in South Carolina, is also threatened by rising seas. A recent article in The Island Packet in Hilton Head Island, S.C., reported that the Marines and partner organizations are applying for grant money to construct oyster-shell reefs bundled in wire to help protect and preserve the low-lying island. The arti cial reefs would encourage the expansion of salt marshes, which help buffer wave energy and decrease ooding and erosion. Even so, “That facility has a limited lifespan,” said Rob Young, a geology professor at Western Carolina University in neighboring North Carolina. “As long as sea level continues to rise, the mission of that facility is going to have to be accomplished somewhere else. I can’t tell you whether that’s 10 years from now or 50 years from now, but it will happen.”

Sea level along the U.S. coastline is projected to rise, on average, 10"-12" in the next 30 years (2020 - 2050), which will be as much as the rise measured over the last 100 years (1920 - 2020), according to the 2022 Sea Level Rise Technical Report. SOME BENEFIT

On the other side of the U.S., in Puget Sound, Wash., Matt Nichols of Nichols Brothers Boat Builders said his company tracks water levels closely because the boatyard sits practically on the edge of Whidbey Island’s Holmes Harbor. “We haven’t seen any change at all,” he

said. “We live and die by the tides, so we know what’s been happening over the 58 years we’ve been here. We’ve seen water over the road and into the yard many times, like during especially high tides and flooding rivers nearby, but we have ways of sandbagging and that type of thing. But the positive side of it is, with deeper water, we can launch deeperdraft vessels.”

A few others may also benefit from rising waters, like marine construction companies that build artificial reefs, seawalls and levees. Other construction will also be needed to repair or raise roadways. Drainage systems will need rebuilding, and many shoreside structures will need to be raised above encroaching tides and storm surge.

“If we want to minimize the impact of sea-level rise in the next century, here’s how we do it: stop burning fossil fuels and move to higher ground,” writes Jeff Goodell in his 2017 book, “The Water Will Come.”

“We wouldn’t even have to stop burning fossil fuels tomorrow. If we did it by 2050, that would be good enough. It wouldn’t entirely halt sea-level rise, but it would avoid the worst of it. Instead of six, seven, eight feet, or more by the end of the century, we might get two or three. We would still need to retreat from the low-lying coastlines, but instead of a stampede, it could be a leisurely stroll.”

Bruce Buls

Nichols Brothers Boat Builders tracks water levels closely because the shipyard is located on the edge of Whidbey Island, Wash.'s, Holmes Harbor.