The £131million (€145million) expedition set up four observation points in 25 miles (40km) radius around the Polarstern.
The scientists then collected water samples from below the Arctic ice to study how plankton and bacteria fare under extreme conditions.
Dr Rex said: “At the North Pole itself, we found badly eroded, melted, thin and brittle ice.”
Unfortunately, if warming trends are allowed to continue, the expert said the Arctic is going to see ice-free summers in as little as a few decades.
More than 1,000 ice samples and some 150 terabytes – more than 150,000,000MB – of data returned to Germany this week.