Bright pink algae that light up the Arctic seafloor like Las Vegas neon are also guides to hundreds of years of climate history, a new study shows.
From the medieval chill called the Little Ice Age to the onset of global warming in the 1800s, the coralline algae show how Arctic sea ice has responded to climate swings for the past 650 years. The findings were published Monday (Nov. 18) in the journal Proceedings of the National Academy of Sciences.
For the first time, researchers now have ancient sea ice information on a yearly scale, said lead study author Jochen Halfar, a paleoclimatologist at the University of Toronto in Mississauga, Canada. "This is important for understanding the rapid, short-term changes that are currently ongoing with respect to sea ice decline," Halfar said in an email interview.
Undersea 'tree rings'
The species are called coralline algae because they deposit coral-like crusts of the mineral calcite on underwater rocks, coating the rocks with colorful pink splotches. (However, algae are plants and coral are animals.) Because the algae go dormant in the winter, when sea ice blocks incoming sunlight, the calcite layers develop visible bands that are similar to tree rings, Halfar said.
During the Little Ice Age, when volcanoes and sun cycle variations caused a global cooling from the 1300s to the 1800s, the coral's underwater "tree rings" narrowed, suggesting extensive sea ice cover and short summers. Starting in 1850 — the onset of the Industrial Revolution — the algae's growth rings doubled in thickness, in sync with the decline in the extent of Arctic sea ice. "The steepness of the decline is unprecedented in the entire record," Halfar said.
The algae records also reveal frequent year-to-year variations in the amount of sea ice, as satellites have seen in the past decade, when the Arctic sea ice has seesawed between relative highs and extreme lows. [Video: Deep Sea Algae Contain Climate Change Clues]