March 11, 2020, as you might remember, was a dark, unsettling day. After an NBA player tested positive for coronavirus, the league called players off an Oklahoma basketball court minutes before tipoff, and then promptly suspended the season. Tom Hanks revealed he tested positive. The Dow Jones Industrial Average plunged. President Donald Trump suddenly announced a European travel ban. German Chancellor Angela Merkel told her nation a serious pandemic had arrived, and "that many people will be infected."

It was all terribly real. And everything was shutting down.

In March, NASA oceanographer Josh Willis supposed his looming, critical endeavor to observe how the warming oceans were melting Greenland and raising sea levels — a mission called Oceans Melting Greenland — would be shut down, too. "I assumed there would be no way we would be able to do the mission this year," Willis said in an interview.

And yet, over a three week period in August and September this year, the multiyear mission to collect novel, largely unprecedented data flew, and Willis brought back invaluable observations: The waters around Greenland's glaciers have started warming again, after a short-lived, about four-year cooling trend. This portends the accelerated melt of Greenland's colossal glaciers as the climate relentlessly warms. Many of these glaciers end in great cliffs of ice that extend two or three thousand feet beneath the sea.

"The mission was an adventure, to say the least," said Willis. "We made it home and no one got sick. Usually, someone at least gets a cold."

Taking off

The odds looked heavily stacked against the fifth, and second-to-last, year of the Oceans Melting Greenland mission. Amid the spread of a newly emerged human pathogen with no proven treatments nor a vaccine, the trip required traveling to Canada before flying around Greenland for some six weeks, with a stop in Svalbard (islands east of Greenland). Willis' six-person crew had to get approval from NASA's Jet Propulsion Laboratory, NASA headquarters, the U.S. State Department, and the plane's operator, along with the governments of Greenland, Denmark, Iceland, Norway, and Canada.

"At any step I assumed someone would just say 'no,'" said Willis. "To our surprise, people said 'yes.'"

But "yes" came with stringent COVID precautions. "Greenland had almost no cases," said Willis. "The worry we might introduce COVID into Greenland was huge." Willis and his team quarantined when they first arrived in Greenland and avoided contact with any locals. Willis was tested once a week during the mission, in addition to regular testing for his six-person crew. They masked when necessary. It worked. No one spread disease.

Once the tests came back negative, the crew could take flight.

To understand how the ocean is impacting Greenland's great rivers of ice (aka glaciers) that pour into the sea, it's vital to measure the ocean temperature, up to some 3,000 feet beneath the surface. That's where the melting happens. "The only way to measure that is to stick a thermometer down there," explained Willis.

The mission, then, largely involves flying low along the Greenland coast and dropping data-collecting tubes into the water in front of the glaciers. The plane, a retrofit old DC-3 propellor plane, is well suited for the task. "It's like an Indiana Jones plane," said Willis. It flies relatively slow, at some 100 mph, allowing the team to make careful, precise drops into the sea. Once the canisters, which look like three-foot-long poster tubes, parachute into the water, they break apart. One piece floats on the surface, transmitting the thermometer's data to the plane. The other piece, which measures temperature and salinity, sinks. It's a spool of thin wire, thinner than a human hair, that unravels for 3,000 feet. It gathers a deep profile of the water.

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Importantly, it's the deeper, relatively warmer waters (compared to the surface) that eat away at the foot of the glaciers. This accelerates how fast the glaciers break apart and collapse into the water, ultimately raising sea levels. During the mission, the crew successfully dropped 348 tubes into the water, their most ever.

"It was a huge success," said Willis.

The warming

Greenland is getting hit hard, from both above and below.

The relentlessly warming Arctic atmosphere is melting Greenland's ice sheets at an "off-the-charts" rate. Meanwhile, the oceans are melting the ice from below. Critically, in the coming years, decades, and beyond, the oceans will inevitably absorb profoundly more heat — specifically the heat trapped on Earth by human-created carbon emissions. The absorbent ocean soaks up over 90 percent of this accumulating warmth. Over the last three decades, this amassed heat equated to theamount of energy released when detonating the biggest atomic bomb ever built once every 10 minutes for 10 years.

This means the North Atlantic oceans around Greenland will grow increasingly warmer overall, and melt more of Greenland's ice, even though currents will inherently vacillate between relatively cooler and warmer periods. The big picture is more heating.

"The whole ocean is warming up," emphasized Willis, particularly the Atlantic, he said. "The glaciers are going to be more and more threatened by the oceans, every decade."

The ultimate consequence of glaciers breaking apart, or calving, ever faster into the water is sea level rise. The colossal ice sheets on Greenland (and Antarctica) figure to be increasingly dominant sources of sea level rise this century. Between 1992 and 2018, Greenland lost some 3.8 trillion tons of ice to the oceans, and the island's sprawling ice sheet alone will raise sea levels by some three to five inches by 2100, according to NASA. Those numbers, however, could be low, said Willis, as they don't fully account for the recently discovered, potent influence of the ocean's melting of the glaciers. (Other projections have concluded sea level rise from Greenland could be significantly higher in 2100, by over 10 inches.)

Overall, sea levels globally have risen by some eight to nine inches since the late 1800s. A conservative estimate, from the UN's Intergovernmental Panel on Climate Change (IPCC), is that sea levels will rise by another one to two feet by the century's end. But, this could very well be more like two or three feet, or potentially an extreme six or so feet, said Willis. That's because some of the biggest glaciers on Earth — like the monstrous and alarming Thwaites glacier in Antarctica — have destabilized. It's unknown how much ice this dominant southern glacier could potentially unleash in the coming years, but it could be terrible for the coastal world (nearly 2.4 billion people live within 60 miles of the coast). "Thwaites is the one spot in Antarctica that has the potential to dump an enormous amount of water into the ocean over the next decades," Sridhar Anandakrishnan, a professor of glaciology at Penn State University, told Mashable earlier this year.

Willis is now back in Pasadena, California, working with NASA scientists to project how the warming oceans might accelerate the melt of Greenland's great glaciers in the coming decades (stay tuned for that research). The melt has already been significant.

Greenland's mighty Jakobshavn glacier, which has retreated over 25 milessince the late 1800s, changed course and briefly started growing in 2016 as cooler waters flowed into the region. The Oceans Melting Greenland mission tracked these changes, demonstrating how the ocean holds powerful sway over the glacier. This year, however, the pandemic-era mission discovered the waters have started warming again. "We found out it was warmer than in years past," said Willis. "Jakobshavn's growth spurt was only temporary."

"This is the signal we were hoping to catch," he added. "It proves how sensitive this glacier is to the water."

As for Earth's future, Jakobshavn is one of the most critical glaciers on the planet. This river of ice fills a canyon that reaches deep into Greenland, which, like a cork, keeps inland ice locked in place. But as the oceans melt Jakobshavn's 2,500-foot tall cliff face, the glacier will recede, releasing ever more ice into the oceans and raising sea levels. It's unknown, at present, how much ice that will be. But the melting process is certainly in motion.

Willis' NASA mission proves the warming ocean is speaking loudly to this monstrous glacier. "The big guy is listening," said Willis.