Robust seasonal cycle of Arctic sea ice area through tipping point in amplitude

TL;DR

This paper reveals that the Arctic sea ice's seasonal cycle amplitude experienced a tipping point in 2007, marking a significant climate change that is largely independent of greenhouse warming, with the shape of the cycle remaining surprisingly constant.

Contribution

It identifies a climate tipping point in 2007 characterized by a dramatic increase in the seasonal cycle amplitude of Arctic sea ice, independent of greenhouse warming effects.

Findings

Tipping point in Arctic sea ice occurred in 2007.

Seasonal cycle shape remains constant despite ice decline.

Amplitude change reflects rapid perennial ice reduction.

Abstract

The variation in the Arctic sea ice is dominated by the seasonal cycle with little inter-annual correlation. Though the mean sea ice area has decreased steadily in the period of satellite observations, a dramatic transition in the dynamics was initiated with the record low September ice area in 2007. The change is much more pronounced in the amplitude of the seasonal cycle than in the annual mean ice area. The shape of the seasonal cycle is surprisingly constant for the whole observational record despite the general decline. A simple explanation, independent of the increased greenhouse warming, for the shape of the seasonal cycle is offered. Thus the dramatic climate change in arctic ice area is seen in the amplitude of the cycle and to a lesser extend the annual mean and the summer ice extend. The reason why the climate change is most pronounced in the amplitude is related to the rapid reduction in perennial ice and thus a thinning of the ice. The analysis shows that a tipping point for the arctic ice area was crossed in 2007.