The findings demonstrate that the climate of Antarctica fluctuated significantly throughout the 20th century and indicates that sea ice in the Antarctic is much less sensitive to the effects of climate change than that of the Arctic, which has experienced a dramatic decline during the 20th century.
In future the team plans to use data from naval and whaling ships as well as the logs from Amundsen’s expeditions to complete the picture.
Separate research by the British Antarctic Survey also showed that the present day loss of the Pine Island Glacier on the West Antarctic Ice Sheet has been happening since the mid 20th century and was probably caused by El Nino activity rather than global warming.
Pine Island Glacier, which drains into the Amundsen Sea in West Antarctica, is retreating and thinning rapidly, but the initial triggering mechanism was unclear. The team looked a sediment cores in the area which showed that an ocean cavity under the ice shelf began to form around 1945, following a pulse of warmth associated with El Niño events in the tropical Pacific Ocean.
“We are very excited about this new finding as it provides the first direct evidence of the timing of glacier retreat even before we had satellites to measure them,” said lead author, marine geologist Dr James Smith from British Antarctic Survey.
“They show us how changes half-way across the planet in the tropical Pacific, reached through the ocean to influence the Antarctic ice sheet.”
Co-author Professor Bob Bindschadler of NASA added: “A significant implication of our findings is that once an ice sheet retreat is set in motion it can continue for decades, even if what started gets no worse.
“It is possible that the changes we see today on Pine Island Glacier were essentially set in motion in the 1940s.”
The Pine Island research was published in Nature.