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. 18) in the journal Proceedings of the National Academy of Sciences.
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] Collecting more algae crusts could help fill a gap between climate records from sediment and ice cores, which may only provide a record for every 100 years, and satellite tracking, which goes back for only a few decades, Halfar said.
"Models right now differ tremendously in predicting when an ice-free summer Arctic will occur," Halfar said.
"A big problem in these models is the lack of long-term data from the past that can be used as input.