On the basis of all available data, it is found that intermediate water temperature on the 26.8–27.4σθ isopycnals in the northwestern North Pacific has significantly increased during the past 50 years. The largest warming area exists in the western part of the Sea of Okhotsk with a 0.68°C/50‐yr temperature increase observed at 27.0σθ. The warming in the Pacific is found over the Oyashio and Subarctic Current regions, where the Okhotsk water extends along the subarctic gyre. This suggests that the warming originates from the Sea of Okhotsk. The warming trend is also accompanied by the significant decreasing trend of dissolved oxygen content, suggesting the weakening of overturning in the northwestern North Pacific. We propose that these trends of the water mass property are caused by a decrease in dense shelf water production in the northwestern shelf of the Sea of Okhotsk, which is a sensitive area to the current global warming.
Predictability of sea ice concentrations (SICs) in the Barents Sea in early winter (November-December) is studied using canonical correlation analysis with atmospheric and ocean anomalies from the NCEP Climate Forecast System Reanalysis (CFSR) data. It is found that the highest prediction skill for a single-predictor model is obtained from the 13-month lead subsurface temperature at 200-m depth (T200) and the in-phase meridional surface wind (V sfc ). T200 skillfully predicts SIC variability in 35% of the Barents Sea, mainly in the eastern side. The T200 for negative sea ice anomalies exhibits warm anomalies in the subsurface ocean temperature downstream of the Norwegian Atlantic Slope Current (NwASC) on a decadal time scale. The diagnostic analysis of NCEP CFSR data suggests that the subsurface temperature anomaly stored below the thermocline during summer reemerges in late autumn by atmospheric cooling and affects the sea ice. The subsurface temperature anomaly of the NwASC is advected from the North Atlantic subpolar gyre over ;3 years. Also, V sfc skillfully predicts SIC variability in 32% of the Barents Sea, mainly in the western side. The V sfc for the negative sea ice anomalies exhibits southerly wind anomalies; V sfc is related to the large-scale atmospheric circulation patterns from the subtropical North Atlantic to the Eurasian continent. This study suggests that both atmospheric and oceanic remote effects have a potential impact on the forecasting accuracy of SIC.
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