How did the Tirpitz, the biggest German battleship, manage to escape Allied bombers during the Second World War? Researchers have finally found the answer in the dark circles of the trees that lived through the event.
During the 39-45 conflict, the Allies tried several times to sink the Tirpitz that then British Prime Minister Winston Churchills called “the beast”. The ship was finally sent to the bottom in November 1944, during an air attack by the Royal Air Force. But the fact that it managed to survive for so long has long fascinated historians.
More than 70 years later, in 2016, during a trip with her students to the forests along the Kafjord, a fjord in northern Norway, researcher Claudia Hartl came across some rather unexpected traces of these fights.
“We measured tree rings and found that they were very narrow, in some cases almost absent, for the year 1945,” Claudia Hartl told AFP at the annual meeting of the European Union of Geosciences organized in Vienna. “Of course, we wondered why?”
The first suspicions were insects, which can spread very rapidly and cause great damage, especially in boreal forests of high latitude.
Mountain pine beetles, brown beetles no larger than a grain of rice, have recently devastated very large forest areas in Canada. But no insect of this kind has been found in northern Scandinavia in the middle of the twentieth century. “Only by speaking with a scientist from Tromsø (a town in northern Norway near which the ship was sunk) did we make the connection with the Tirpitz,” said Scott St. George, geographer of the Institute of the Environment at the University of Minnesota.
The Tirpitz and its 2,500 crew members waa, at the time, hidden in the aquatic labyrinth of northern Norway. In the “pre-satellite” era, a 250 meter monster could be hard to spot. But once the “beast” was found, the Allied bombers went into action.
To protect themselves, the Germans then spread a large amount of artificial fog. “This smog invaded the forests bordering the fjord leaving behind” a special and unusual “fingerprint,” commented Scott St. George.
The study of tree trunk growth rings, known as dendrochronology, allows climatologists to examine changes in temperature, rainfall or watercourses going back hundreds, even thousands of years. To continue her investigation, Claudia Hartl returned last summer to the scene of the battle.
The researcher was able to establish that where the vessel was, more than 60% of the trees had stopped growing. Four kilometers from the fighting, more than half of the trees showed signs of suffering. It took them about eight years to recover.
Claudia Hartl also discovered areas with trees dating back to the 1950s, suggesting that the chemical fog had destroyed those that were there before. The chemical fog employed by the Tirpitz was probably composed of chlorosulphuric acid which, when mixed with water, produces a thick, white vapor.