Seasonally dependent interannual variability of sea ice in the Bering Sea and its relation to atmospheric fluctuations

Abstract

[1] 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 1 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 to large-scale atmospheric circulation associated with the Aleutian low and the other mode is related to 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.Citation: Sasaki, Y. N., and S. Minobe (2005), Seasonally dependent interannual variability of sea ice in the Bering Sea and its relation to atmospheric fluctuations,

Processes driving sea ice variability in the Bering Sea in an eddying ocean/sea ice model: anomalies from the mean seasonal cycle

“…Wind anomalies over the Bering Sea are important for the interannual variability of sea ice. Many studies indicate the correspondence of anomalous northerly wind and increased sea ice in the Bering Sea (Niebauer 1980, Walsh and Sater 1981, Fang and Wallace 1994, Sasaki and Minobe 2005. At the same time, surface air temperature anomalies are related to advection by winds on the large scale (e.g., Deser et al 2000).…”

“…Our results are generally consistent with other studies. Some studies show that the climatic forcing of the Bering Sea ice variability arises from local processes (Fang andWallace 1994, Sasaki andMinobe 2005), rather than being associated with any prominent large-scale remote climate indices. Wind anomalies over the Bering Sea are important for the interannual variability of sea ice.…”

“…The winter sea ice extent is also associated with storm tracks (Overland and Pease 1982;Rodionov et al 2007) and the local atmospheric variability related to winds (Sasaki and Minobe 2005).…”

“…The winter air temperature and sea ice extent are also related to storm track changes associated with the strength of the Aleutian Low (Overland and Pease 1982;Rodionov et al 2007). Additionally, the local wind variability, which is associated with geopotential height anomalies over Alaska and temperature anomalies over the northern Bering Sea, is also important (Sasaki and Minobe 2005). On larger scales, the ice concentration anomalies in the Bering Sea and the Sea of Okhotsk tend to be opposite, and they are believed to result from atmosphere circulation variations 1 month earlier (Niebauer 1983;Cavalieri and Parkinson 1987;Fang and Wallace 1994;Deser et al 2000).…”

“…Zhang et al (2010) focused on interannual sea ice variations in the Bering Sea, which they found to be dominated by winddriven changes in ice transport and the ocean thermal front in the southern Bering Sea. From a large-scale perspective, the interannual variability of sea ice in the Bering Sea is mainly driven by atmospheric forcing, especially in winter (Walsh and Johnson 1979;Walsh and Sater 1981;Niebauer 1980Niebauer , 1983Niebauer , 1988Niebauer , 1998Niebauer and Day 1989;Rogers 1981;Overland and Pease 1982;Sasaki and Minobe 2005). The winter atmospheric conditions over the Bering Sea (surface air temperature and winds) and the Bering Sea ice cover are mainly determined by the position of the Aleutian Low (Rogers 1981;Cavalieri and Parkinson 1987;Niebauer 1998;Rodionov et al 2005Rodionov et al , 2007.…”