| 論文要旨 |
Interannual variability of sea-ice in the Bering Sea and its relationship to atmospheric
variability is analyzed using a Singular Value Decomposition (SVD) analysis of Sea-Ice
Concentrations (SICs) and 1000-hPa wind speeds in winter and spring seasons. The statistically
significant first and second SVD modes, explaining 76.3% and 17.6% in winter and 54.6% and 29.6%
in spring of the squared covariance between the two fields, are identified for SICs both in the
winter and spring seasons with one-month leading wind speeds. The spatial structures show that the
first (second) SVD mode explains the SIC variability in the northeastern (northwestern) Bering
Sea, related to the local northwesterly (northerly) wind anomalies for the positive SIC anomalies
both in the winter and spring seasons. A comparison of the first SVD modes between the winter and
spring seasons suggests that the difference of dominant patterns of wind anomalies results in the
difference of SIC anomaly distributions between two seasons.
The relationship between sea-ice and atmospheric circulation anomalies indicates that one mode
of the leading two SVD modes in each season is related with large-scale atmospheric circulation
associated with the Aleutian low and the other mode is related with relatively local atmospheric
fluctuations related with pressure anomalies over Alaska. Furthermore, a slight difference of
700-hPa geopotential height anomalies results in the substantially different sea-ice anomalies.
These results suggest that in order to know the interannual sea-ice variability in the Bering Sea,
a better understanding of the wind anomalies over the Bering Sea are important.
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