“We were getting a little nervous,” he said. So on July 30, they removed the last remaining equipment from the ice.

“And then we woke up the next morning and our ice floe was in a thousand pieces,” he said.

Dr. Shupe’s second tour on the Polarstern began in June, when he arrived with a group to replace the scientists and technicians who had been on board since late February. The swap had been scheduled to take place in April, but the pandemic intervened.

Because of restrictions on travel and the need to quarantine participants in order to keep the expedition free of the virus, a planned transfer by aircraft was scrapped. Instead, in late May, the Polarstern left its ice floe to rendezvous with two smaller ships carrying Dr. Shupe and others off the Norwegian archipelago of Svalbard. The Polarstern then headed back to the ice.

Abandoning the floe for nearly a month affected some of the research, the expedition’s leaders said at the time. But many autonomous instruments kept collecting data during the ship’s absence.

Carin Ashjian, a biological oceanographer at the Woods Hole Oceanographic Institution in Massachusetts, was among those who left Norway for the Polarstern in late January, before the coronavirus outbreak became a pandemic, and was on board two months longer than planned.

“Who knew when we went up there that life was going to take such an astoundingly strange turn?” said Dr. Ashjian, who studies small marine organisms called zooplankton.