The MTA joked in a reply to a tweet that it was pivoting to submarines, but then followed up with its own tweet, "But actually, we were testing a new 'flex gate,' which is a flood barrier that would allow us to seal off a subway entrance. We 'test flood' the entrance for four hours to make sure it was installed correctly, which it was!" The tweet said. It continued, "We're doing this because climate change is real."

But actually, we were testing a new "flex gate," which is a flood barrier that would allow us to seal off a subway entrance. We "test flood" the entrance for four hours to make sure it was installed correctly, which it was!

We're doing this because climate change is real. ^JLP

— NYCT Subway (@NYCTSubway) November 20, 2019

In another reply, the MTA wrote, "We're investing in capital projects around the system to prepare for the impacts of a changing climate." The tweet linked to an statement titled Preparing for Climate Change, where the agency made about taking a drastic step to prepare for the climate emergency by completely shutting down several stations for six months so it can protect a maintenance facility and storage yard for its trains in Coney Island.

"The location of the yard provides ideal access to multiple subway lines, but it's vulnerable to flooding," said the statement. "With intense weather events like Superstorm Sandy expected to occur more often, we need to act now to protect this vital part of our system, so we can keep trains running safely."

The "flex gate" that the MTA tested on Wednesday easily unrolls and makes a tight seal against a metal lip that runs along the edges of a subway stairwell opening to keep water from running underground, as the New York Post reported.

The subway system experienced catastrophic flooding during Superstorm Sandy in 2012 when stations were inundated from track to ceiling with corrosive salt water. Since that weather event, the MTA has upgraded stations and tunnels to prevent flooding and installed the flexible stairwell cover, or flex gate, at 65 station entrances so far, as The Verge reported. The agency spent $369 million to upgrade the South Ferry 1 train station at the southern tip of Manhattan, which was flooded by 15 million gallons of salt water, according to Gothamist.

"At street level, we built flood gates into flood-prone train station entrances, while hatches and manhole covers were redesigned to withstand large volumes of standing water. Underground, marine cabling replaced the regular wiring in the under-river tubes to increase flood resiliency," the MTA Climate Action Task Force wrote in its 2019 Resiliency Report, as Gothamist reported.