A version of this ICN story was copublished with NBC News.

PORTSMOUTH, Va. — At the foot of the Chesapeake Bay in southeast Virginia lies a Naval shipyard older than the nation itself. One of the country's first warships was built here in 1799. So was the first battleship, and decades later the first aircraft carrier.

Over a quarter millennium, Norfolk Naval Shipyard has been blockaded and burnt to the ground by the British, the Union and the Confederates, only to be rebuilt again and again to evolve into a hub of Naval power.

Today, it's an essential maintenance facility for the nation's fleet of nuclear-powered submarines and aircraft carriers, and it's facing a threat that could shut it down permanently.

Rising seas will likely engulf the shipyard by century's end, but the reckoning for Norfolk and nearby military installations could come much sooner.

"They're going to disappear" unless the Pentagon acts quickly to protect them, said Ray Mabus, Navy secretary under President Barack Obama.

The most immediate worry is a direct hit from a major storm. "It would have the potential for serious, if not catastrophic damage, and it would certainly put the shipyard out of business for some amount of time," Mabus said. "That has implications not just for the shipyard, but for us, for the Navy."

Sign up for InsideClimate News Weekly Our stories. Your inbox. Every weekend.

The shipyard is among the American military sites most vulnerable to climate change. Because of its role in maintaining the fleet, damage to the aging facility could undermine the Pentagon's ability to respond to military and humanitarian crises and to counter China's growing naval ambitions.

Like most of the Hampton Roads region, it's low-lying and hugged by water. Sea level has risen 1.5 feet in the past century here, about twice as much as the global average, because of climate change and land subsidence. Meanwhile, global warming is increasing the frequency of severe storms.

Among Norfolk Naval Shipyard's greatest vulnerabilities are its five dry docks, waterside basins that can be sealed off and pumped dry to expose a ship's hull for repairs for months or years at a time. Once inside, the vessels are often opened up, leaving expensive electronics and mechanical systems vulnerable to storms and flooding. The ships' nuclear reactors raise radiological concerns, too, though the Navy says it takes extensive measures to prevent nuclear accidents.

Of the Navy's four shipyards, only two can dry-dock aircraft carriers. One is Norfolk Naval Shipyard, and it is both aging and at increasing risk of inundation during storms as sea level rises. The only other facility on the East Coast capable of dry-docking a carrier is a private shipyard across the James River. Credit: Joshua J. Wahl/U.S. Navy

The dry docks "were not designed to accommodate the threats" of rising seas and stronger storms, according to a 2017 report by the Government Accountability Office. Navy officials warned the GAO that flooding in a dry dock could cause "catastrophic damage to the ships."

Already, high-tide flooding is contributing to extensive delays in ship repairs, the GAO said, disrupting maintenance schedules throughout the nuclear fleet.

The Navy has erected temporary flood walls to protect the dry docks and has begun elevating some equipment. It also recently proposed a more permanent barrier and other projects to address flooding, part of a 20-year, $21 billion plan the Navy submitted to Congress this year to modernize its four shipyards.

But the new projects have yet to be approved by lawmakers.

In October, Hurricane Michael offered a glimpse of what can happen to coastal military bases in a storm's path when it leveled much of Tyndall Air Force Base, damaging more than a dozen stealth fighters undergoing maintenance.

Months earlier, officials at the Federal Emergency Management Agency had envisioned what might occur if a similar storm were to strike Norfolk—by driving a computer-simulated Category 4 hurricane directly into the Hampton Roads region as part of a national disaster preparedness drill. Their simulated cyclone's 140 miles-per-hour winds snapped power lines and cell towers, immediately hobbling the grid and communications, and whipped the Chesapeake Bay into a 12-15 foot storm surge, high enough to flood entire downtowns of some of the area's cities.

The Navy declined to disclose the precise damage to the shipyard in the scenario, but a press release described the aftermath as "New Orleans without the levee system." National hazard maps show a storm of that magnitude would likely submerge the entirely facility.

"It's not a question of if, it's a question of when," said retired Vice Adm. Dennis V. McGinn, who was assistant secretary of the Navy for energy, installations and environment until January 2017 and is now an advisory board member at the Center for Climate and Security. "And when it hits, how vulnerable are we going to be, and are we going to be standing there saying, 'oh, we woulda, coulda, shoulda.'"

Leadership Matters

Climate change is threatening to impair the military's ability to respond to crises and defend the nation, not only at the shipyard but throughout its operations. The Defense Department has publicly recognized this risk for at least 15 years. The Navy, in particular, understands what is at stake, with so many facilities along the coasts and its forces often the first to arrive on the scene of humanitarian crises triggered by extreme weather.

Still, the response across the military has been piecemeal and inadequate, according to interviews with more than a dozen retired officers and former senior-ranking national security officials.

"It's probably on the radar, but it's below what we would call the cut line," said retired Rear Adm. David W. Titley, who initiated the Navy's Task Force Climate Change in 2009. Senior officers spend their days fielding urgent requests for money and resources, he said, and have little left for long-term threats. "That's probably how it's looked at: 'Yes this is a problem, but I still see the shipyard out there,' and so it gets kicked down the road."

Even when commanders do take climate change seriously, politics and legislative gridlock can prevent them from embarking on major projects. "My experience was, the thing that Congress is most likely to do is not fund it until it becomes a crisis," Mabus said. "And then it might be too late."

Addressing climate change has become more difficult under President Donald Trump. His administration omitted mention of climate change in its first National Security Strategy and instead called for greater fossil fuel development. Trump rescinded an Obama executive order that, in part, sought to provide intelligence analysts with the most current climate science to better monitor potential global hotspots. Nearly all references to climate change were also stripped from the final draft of a survey about the effects of climate-driven weather on facilities.

Military officials have become reluctant to work openly on climate change in the current political environment, said Joan VanDervort, former deputy director for ranges, sea and airspace at the Pentagon. "They have gone underground. They're doing the same work but calling it something different. They try to stay away from the words 'climate change,' and use words like natural resources and resiliency and terms like weather, hurricanes," she said. When you omit "climate change as a priority related to our national security, it's very difficult to get funding."

Norfolk and the other three Navy shipyards have suffered extensive maintenance delays, with a total of nearly 14,000 lost days of operations for the submarines and aircraft carriers between 2000 and 2016, according to the Government Accountability Office. Credit: Shayne Hensley/Norfolk Naval Shipyard

When asked about the Navy's response to climate change at the shipyards, a spokesman pointed to comments made by Defense Secretary James Mattis last year as part of his confirmation process: "The Department should be prepared to mitigate any consequences of a changing climate, including ensuring that our shipyards and installations will continue to function as required."

Mattis is one of the few Trump cabinet secretaries who has taken climate change seriously, but he's rumored to be on his way out. His departure could put in jeopardy whatever climate action the Pentagon is taking.

"Leadership matters, and leadership really matters in a hierarchical organization, and DoD is a really hierarchical organization," said Alice Hill, who was a special adviser to President Obama on climate and national security. "I have personally been told by military personnel that unless their leaders are communicating that this is a risk, they do not see this as a priority they need to work on."

Catastrophic Risk

As scientists with the Army's Manhattan Project were trying to unleash nuclear energy in a bomb in the 1940s, the Navy was exploring harnessing it to power ships. Submarines in particular would gain tremendous tactical advantages. They would no longer need to surface to recharge their batteries with diesel generators, making them less vulnerable to detection. They would be able to sail for years—and in later models, decades—without refueling.

Today, all of the nation's 69 submarines and 11 aircraft carriers are nuclear-powered, and they help project the military's power across the globe. The carriers bring fighter jets to the South China Sea to defend American allies from territorial claims by China. They sail to the Middle East to counter Russia's presence in Syria. Ballistic missile submarines carry atomic warheads as part of the country's nuclear deterrence.

Nuclear power has a drawback, however: The ships can be repaired at only a handful of facilities that have the equipment and personnel required to handle radiological material. Of the Navy's four shipyards—the others are in Maine, Hawaii and Washington state—only two can dry-dock aircraft carriers: Puget Sound and Norfolk. The only other facility on the East Coast that's capable of dry-docking a carrier is a private shipyard across the James River in Newport News, which faces similar challenges as Norfolk because sea level is expected to rise at least an additional foot in the region by 2050.

Dry-docking a submarine allows crews to open it up and perform maintenance, like this work underway at Puget Sound Naval Shipyard in Bremerton, Washington. If the dock were to flood in a storm, unsealed areas of ships could be damaged. Credit: Richard Chaffee/U.S. Navy

In two reports—from 2014 and last year—the GAO cited officials at Norfolk and an unnamed shipyard who warned that flooding from storms posed a threat to ships undergoing maintenance. In one case, they were preparing to cut a submarine in half in order to lengthen it and were concerned that "if salt water was allowed to flood the submarine's systems, it could result in severe damage," adding months of additional maintenance.

A dry dock resembles a giant, three-sided dumpster pushed into the ground. The fourth side opens to the water so ships can pull in and out, but it can be sealed off with a caisson—a watertight gate—to pump the box dry. Once docked, workers usually open the ships' hulls to access the insides.

"If the water comes over the walls of the dry dock and starts flooding into the ship itself, its essentially like sinking the ship," said Diana Maurer, who manages the GAO's shipyards oversight. "It would be very, very bad."

The Navy explained in an email that it has measures to prevent that type of accident. When a major storm is approaching, it said, workers can quickly seal up ships that are undergoing repairs. That allows them to refill the dry dock and float the vessel.

It took the first of these measures with the submarine USS Wyoming as Hurricane Florence headed for the region in September, the Navy said.

However, a second ship, the USS San Francisco, was also dry-docked and was cut in half. The Navy did not say whether it sealed up the San Francisco, but commenters on the shipyard's Facebook page expressed skepticism: "San Fran won't be" sealed in time, one wrote. "It's split."

Florence veered into the Carolinas, sparing Norfolk and the USS San Francisco.

Norfolk Naval Shipyard has experienced tidal flooding from storms or high winds at least nine times over the past decade, according to the Navy. A presentation titled "NNSY Dry Dock Flooding" shows photographs of flood waters in and around what appear to be dry docks several times in recent years.

Flooding at Norfolk Naval Shipyard shown in a Naval Facilities Engineering Command presentation. Credit: NAVFAC

In 2009, after days of strong winds driving high tides, water surged into a dry dock at a rate of 3,000 gallons per minute, leaking from the bottom of the caisson, before workers could seal the leaks, according to the 2017 GAO report. The water did not harm a submarine that was docked at the time, the Navy said.

"The big concern there is you've got a nuclear-powered warship that you've parked inside one of these docks," said J. Pat Rios, who commanded the Navy's engineering and facilities branch in the Mid-Atlantic before retiring in 2016. Rios noted that conventional ships can simply be shut off. "But a nuclear-powered warship needs to have cooling water running on it all the time, even if it's off," he said. "If you had a failure on that caused by recurrent flooding and you suddenly have a lack of cooling water to a nuclear reactor, that's the scary story."

Rios and other former officers and nuclear engineers said such a failure is extremely unlikely because of the shipyard's backup power and safety systems.

The Navy said in a statement that it has "stringent requirements" in place to prevent a nuclear accident. "Navy ships and key infrastructure elements have multiple sources of electrical power; flood prevention and flood management devices," it said, and "ships are placed in their most secure conditions" before a storm hits. Taken together, it said, "these requirements ensure the safety of our personnel, our ships (nuclear and non-nuclear), and shipyard infrastructure."

Mabus and officials at the GAO declined to comment about any concerns within the military about a nuclear accident, saying such matters are classified. The public version of the 2017 GAO report does not mention nuclear concerns, saying only that "drydock flooding during certain delicate depot maintenance tasks risks personnel safety, catastrophic damage to the ships being repaired, and potential environmental impacts."

'This Is Hindering Ship Movement'

On Sept. 1, 2016, as a tropical storm hurtled toward Hampton Roads, Navy engineers sent an urgent request to regional headquarters. They needed to temporarily remove capstans from two of the shipyard's dry docks to protect them from flooding. A submarine was in dock, they warned, and it would be stuck if the winch-like devices were damaged.

They would make similar requests the following year as storms approached, emails show. The work cost more than $100,000.

"Just a reminder," an official wrote in an October 2017 request. "This is hindering ship movement."

Repeated floods have damaged "support equipment and utilities" around the dry docks, as well as motors for capstans and cranes, the Navy said in an email. In 2016, Hurricane Matthew left water standing 2 feet deep in one building, requiring repairs that cost nearly $1.2 million.

The flooding is worsening already poor conditions at the shipyard.

"Most naval shipyard capital equipment infrastructure is well beyond effective service life, obsolete, unsupported by original equipment manufacturers, and at operational risk," a Navy report submitted to Congress this year said. "Continued reliance on this aged equipment infrastructure increases submarine and aircraft carrier depot maintenance availability costs and places schedules at risk."

The shipyards have suffered extensive maintenance delays, with a total of nearly 14,000 lost days of operations for the submarines and aircraft carriers between 2000 and 2016, according to the GAO.

"Combine the fact that they're really old with climate change," said Maurer, of the GAO, "it makes it even more difficult for the Navy to carry out an already challenging task, which is how do you maintain and repair the naval fleet."

Addressing climate change, including the well-documented risks it poses to the military's critical shipyards, has become more difficult under President Trump. Defense Secretary James Mattis said last year: "The Department should be prepared to mitigate any consequences of a changing climate, including ensuring that our shipyards and installations will continue to function as required." Credit: Ryan U. Kledzik/U.S. Navy

In 2016, the USS George H.W. Bush, one of the Navy's 11 aircraft carriers, spent 13 months at Norfolk rather than the planned six months, leaving a gap when there was no carrier in the Middle East. A hurricane caused a 3-4 foot storm surge in the region while the ship was in dock. Sen. Mark Warner (D-Va.) wrote to the Navy to express concerns that the gap limited the service's capabilities.

In an email, the Navy said that flooding "did not directly contribute" to the lag, but it acknowledged that destructive weather events require preparation and work suspensions that can "result in some delay to the maintenance execution schedule."

Mabus, the former Navy secretary, said these delays ripple throughout the fleet's carefully choreographed maintenance schedule. "It's a very, very serious readiness issue," he said.

Every Year You Wait, the Risk Goes Up

A decade ago, the chief of naval operations commissioned the National Research Council to study the implications of climate change on the Navy's mission. The 2011 report warned that global warming would strain the service's capabilities. More severe weather would trigger famine and mass migration, requiring more humanitarian aid. A thawing Arctic would stress the Navy's fleet by opening a vast new arena to police in particularly harsh conditions. Rising seas and harsher storms would put bases at risk: 56 facilities worth a combined $100 billion would be threatened by about 3 feet of sea level rise (the list has not been made public).

It warned that the Navy needed to begin investing in protections immediately at facilities facing the greatest climate risks, and had only 10 to 20 years to begin work on the rest. Seven years later, there's been little progress, said retired Rear Adm. Jonathan White, who led the Navy's Task Force Climate Change before retiring in 2015.

"Many of those recommendations, most if not all, have gone unanswered," he said. "Every year you wait to make decisions and take actions, the risk goes up. And I think the expense also goes up."

While the Navy's ships have changed, its shipyards have seen little investment. "Most naval shipyard capital equipment infrastructure is well beyond effective service life, obsolete, unsupported by original equipment manufacturers, and at operational risk,"a recent Navy report to Congress said. Credit: Michael R. Gendron/U.S. Navy

The Pentagon has taken some steps, including producing a database, which also has not been made public, that provides regional sea level rise projections for 1,774 coastal military facilities. Last year, the Navy published a handbook to help base planners assess climate risks and decide how to incorporate them into planning and construction.

Perhaps most critically, Congress passed legislation this year requiring that any military construction in a 100-year floodplain be elevated at least 2 feet above the expected flood level, the same requirement that was in an Obama executive order Trump had revoked.

As a result of all this, the Navy has begun protecting its bases here and there, elevating critical equipment like generators, for example, and creating "micro-grids" at some facilities, including the shipyard in Maine, to make electrical supply more resilient to storms. In Hampton Roads, the Pentagon has initiated two land-use studies in cooperation with the region's cities to address rising seas.

Even if some of the work the Navy plans to undertake receives funding, it may be inadequate. A flood wall to protect the most vulnerable dry docks at Norfolk Naval Shipyard, for example, will not be built to the more stringent, 500-year-flood standards once considered. Instead, it's being designed a foot and a half lower to keep out a 100-year flood. That probably would not protect against a storm like Cora, the simulated Category 4 hurricane that brought a 12-foot storm surge. A few decades from now, when the seas will be 1 or 2 feet higher, a smaller storm would inflict the same amount of damage.

Before Hurricane Michael destroyed Tyndall Air Force Base in October, the military had flown to safety most of the 55 F-22 stealth fighters the base housed. Those jets now need a new home, and at least for now, some have been stationed at Langley Air Force Base, surrounded by water on three sides about 20 miles north of the shipyard in Hampton Roads.

InsideClimate News reporter Neela Banerjee contributed to this story.

Read this next: Dangers Without Borders: Military Readiness in a Warming World