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Observations reveal external driver for Arctic sea‐ice retreat
Author(s) -
Notz Dirk,
Marotzke Jochem
Publication year - 2012
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2012gl051094
Subject(s) - sea ice , arctic sea ice decline , climatology , arctic ice pack , arctic , environmental science , forcing (mathematics) , climate change , drift ice , arctic geoengineering , geology , oceanography
The very low summer extent of Arctic sea ice that has been observed in recent years is often casually interpreted as an early‐warning sign of anthropogenic global warming. For examining the validity of this claim, previously IPCC model simulations have been used. Here, we focus on the available observational record to examine if this record allows us to identify either internal variability, self‐acceleration, or a specific external forcing as the main driver for the observed sea‐ice retreat. We find that the available observations are sufficient to virtually exclude internal variability and self‐acceleration as an explanation for the observed long‐term trend, clustering, and magnitude of recent sea‐ice minima. Instead, the recent retreat is well described by the superposition of an externally forced linear trend and internal variability. For the externally forced trend, we find a physically plausible strong correlation only with increasing atmospheric CO 2 concentration. Our results hence show that the observed evolution of Arctic sea‐ice extent is consistent with the claim that virtually certainly the impact of an anthropogenic climate change is observable in Arctic sea ice already today.