New research utilizing the DNA of dinoflagellate (Polarella glacialis) indicates that, 14,000 years ago, when the atmospheric CO2 concentration is thought to have been 230 ppm, the studied Arctic region (Yermak Plateau) was sea ice-free year-round.
“Around 14.0-13.9 cal kyr BP, a short-lived year-round, ice-free, open ocean occurred.”
During the Early to Middle Holocene (10,000 to 4,000 years ago), Arctic sea ice was seasonal, dominated by first-year ice that did not survive the summer melt season.
“The Holocene Yermak Plateau is characterized by a seasonal sea ice cover, which my consist mainly of first-year sea ice … a large part of first-year ice, as opposed to seasonally drifted multi-year ice.”
Today, at 430 ppm CO2, Arctic sea ice is increasingly first-year, but a “multi-year environment” persists. Multi-year sea ice has survived at least one summer melt season, and it continues to thicken over multiple years.
The current phase is similar to the sea ice conditions that predominated ~16,000 years ago, or during the last glacial.
“…a marginal sea ice cover ca. 16 cal kyr BP [characterized by] first-year sea ice in a multi-year sea ice environment, a setting not unlike today.”
If the Arctic can be sea ice-free year-round when CO2 is 230 ppm, but dominated by multi-year ice when the CO2 concentration is 430 ppm, this does not support the alarmist claims that high CO2 concentrations are responsible for enhanced Arctic sea ice melt.
