Abstract
Accelerated shrinkage of the Arctic sea ice cover is the main reason for the recent Arctic amplification of global warming. There is growing evidence that the ocean is involved in this phenomenon, but to what extent remains unknown. Here, a unique dataset of hydrographic profiles is used to infer the regional pattern of recent subsurface ocean warming and construct a skillful predictor for surface climate variability in the Barents Sea region - a hotspot of the recent climate change. It is shown that, in the era of satellite observations (1981–2018), summertime temperature anomalies of Atlantic water heading for the Arctic Ocean explain more than 80% of the variance of the leading mode of variability in the following winter sea ice concentration over the entire Northern Hemisphere, with main centers of action just in the Barents Sea region. Results from empirical forecast experiments demonstrate that predictability of the wintertime sea ice cover in the Barents Sea from subsurface ocean heat anomalies might have increased since the Arctic climate shift of the mid-2000s. In contrast, the corresponding predictability of the sea ice cover in the nearby Greenland Sea has been lost.
Highlights
Accelerated shrinkage of the Arctic sea ice cover is the main reason for the recent Arctic amplification of global warming
We have demonstrated that variations of the wintertime sea ice cover in the Barents Sea are strongly coupled to the concurrent sea surface temperature (SST) anomalies on the open water side of the ice edge (Fig. 2) as well as the previous summer subsurface ocean heat anomalies (Fig. 4, Table 1), especially in the LATE period (Fig. 5)
The insulation effect of the cold halocline has gradually weakened along the cyclonic Atlantic water (AW) pathway around the Arctic Ocean probably through a chain of positive feedbacks between the declining sea ice cover, weakening of the halocline stratification, increasing vertical mixing, and growing upward heat fluxes from the shallowing AW layer[12,48]
Summary
Accelerated shrinkage of the Arctic sea ice cover is the main reason for the recent Arctic amplification of global warming. The main objective of the present study is to verify the hypothesis that the high predictability of the sea ice cover in the Barents/Nordic Seas region from AWT anomalies survived through the most recent changes in the Arctic climate system This survival is not a priori granted since a sharp sea ice decline observed in the northern Barents Sea in the mid-2000s52,53 could be linked to reduced wintertime sea ice import from the nearby Kara Sea[13,54], which could limit the ability of AWT anomalies to control the sea ice extent in the Barents Sea. Here, the variability of the Arctic climate system is investigated using statistical analyses applied to SIC, SST and atmospheric fields, as well as subsurface ocean data covering the era of satellite observations (ESO period) from 1981 to 2018. This dataset consists of ocean temperature profiles from the newly compiled Unified Database for Arctic and Subarctic Hydrography (UDASH)[55] supplemented with in situ temperature observations from other sources (see Methods)
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