title: Increase of the Antarctic Sea Ice Extent is highly significant only in the Ross Sea.
abstract: In the context of global warming, the question of why Antarctic sea ice extent (SIE) has increased is one of the most fundamental unsolved mysteries. Although many mechanisms have been proposed, it is still unclear whether the increasing trend is anthropogenically originated or only caused by internal natural variability. In this study, we employ a new method where the underlying natural persistence in the Antarctic SIE can be correctly accounted for. We find that the Antarctic SIE is not simply short-term persistent as assumed in the standard significance analysis, but actually characterized by a combination of both short- and long-term persistence. By generating surrogate data with the same persistence properties, the SIE trends over Antarctica (as well as five sub-regions) are evaluated using Monte-Carlo simulations. It is found that the SIE trends over most sub-regions of Antarctica are not statistically significant. Only the SIE over Ross Sea has experienced a highly significant increasing trend (p = 0.008) which cannot be explained by natural variability. Influenced by the positive SIE trend over Ross Sea, the SIE over the entire Antarctica also increased over the past decades, but the trend is only at the edge of being significant (p = 0.034).
authors.affiliation: CAS Key Laboratory of Regional Climate-Environment for Temperate East Asia, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, 100029, China.|Department of Geography, Climatology, Climate Dynamics and Climate Change, Justus Liebig University Giessen, 35390 Giessen, Germany.
authors.forename: Naiming
authors.initials: N
authors.lastname: Yuan
authors.affiliation: Chinese Academy of Meteorological Science, Beijing, 100081, China.
authors.forename: Minghu
authors.initials: M
authors.lastname: Ding
authors.affiliation: Institute for Theoretical Physics, Justus Liebig University Giessen, Heinrich-Buff-Ring 16, D-35392 Giessen, Germany.
authors.forename: Josef
authors.initials: J
authors.lastname: Ludescher
authors.affiliation: Institute for Theoretical Physics, Justus Liebig University Giessen, Heinrich-Buff-Ring 16, D-35392 Giessen, Germany.
authors.forename: Armin
authors.initials: A
authors.lastname: Bunde