Ozone damage could have constituted half of the Arctic warming in 50 years since the 1950s, scientists say
Arctic sea ice cannot ‘recover quickly if climate change causes it to melt, suggests another recent study.
A team of scientists led by the University of Exeter used quahog clam shells, which can live for hundreds of years, and climate models to discover how Arctic sea ice has changed in the last 1,000 years.
They discovered that sea ice coverage changes on time scales from decades to centuries, so you cannot expect shrinking ice to return quickly if climate change slows or reverses.
The study examined whether ice changes passed to northern Iceland were ‘forced’ (caused by events such as volcanic eruptions and variations in the sunrise) or ‘not forced’ (part of a natural pattern).
It was found that at least one third of the past variations were ‘forced’, which shows that the climate system is “very sensitive” to such driving factors, according to lead author Dr. Paul Halloran of the University of Exeter.
“There is increasing evidence that many aspects of our changing climate are not caused by natural variation, but are” forced “by certain events,” he said.
“Our study shows the great effect that climate controllers can have on Arctic sea ice, even when those controllers are weak, such as volcanic eruptions or solar changes.
“Today, the climatic factor is not the weak volcanic or solar changes, it is human activity, and now we are massively forcing the system.”
Co-author of the study, Professor Ian Hall, of Cardiff University, said: ‘Our results suggest that climate models can correctly reproduce the long-term pattern of sea ice change.
“This gives us greater confidence in what climate models tell us about the loss of current and future sea ice.”
When there is a lot of sea ice, part of this moves south and, by releasing fresh water, can slow down the circulation of the North Atlantic Ocean, also known as the South Atlantic Overturning Circulation (AMOC).
The AMOC brings warm water from the tropics to the Arctic, so the slowdown cools this region and allows sea ice to grow even more.
Then, with less ice, the AMOC can bring more warm water, a so-called ‘positive feedback’ where climate change drives warming and the loss of sea ice.
Quahog clams are believed to be the longest non-colonial animals on Earth, and their shells produce growth rings that can be examined to measure past environmental changes.
Dr. Halloran is part of the Global Systems Institute, which brings together experts from a wide range of fields to find solutions to global challenges.
The new study is part of a project that includes Cardiff University, the Met Office and an international team that works on simulations of climate models of the last millennium. The work was funded by the Natural Environment Research Council.
The article, published in the journal Scientific Reports, is entitled: “Natural engines of the variability of sea ice in the multidecadal Arctic during the last millennium.”