What determines the maximum sea ice extent in the Sea of Okhotsk? Importance of ocean thermal condition from the Pacific

Abstract

[1] Previous studies suggested that the interannual variability of the maximum sea ice extent (MSIE) in the Sea of Okhotsk is not explained only by atmospheric conditions. In this study, we examined the effect of the ocean thermal condition on the determination of the MSIE based on observational data. We found that the MSIE is highly correlated with the sea surface temperature (SST) and ocean temperature around the East Kamchatska Current (EKC) in the Pacific in late autumn (November-December). The significant relationship between the MSIE and the SST cannot be fully explained by prevailing atmospheric variabilities. Considering that the inflow of EKC water to the Okhotsk Sea is strengthened in winter, advection of anomalous ocean temperature likely influences the MSIE. A multiple regression model constructed as a function of SST in the EKC and the air temperature at 850 hPa over the upwind region of the Okhotsk Sea in late autumn, which is another determinant factor for the MSIE, significantly improves the prediction skill for the MSIE: 70% of the variance of MSIE can be predicted at the stage of 2 to 3 months before the MSIE season. The SST in the EKC and the upwind air temperature are likely to control the sea ice extent in the northeastern and center to southern parts of the Okhotsk Sea, respectively.

Creation of a Heat and Salt Flux Dataset Associated with Sea Ice Production and Melting in the Sea of Okhotsk

“…1) and the central and eastern Sea of Okhotsk are considered as such cases. In the central and eastern Sea of Okhotsk, relatively warm water that originates from the East Kamchatka Current comes from the North Pacific through the northern Kuril Straits (Ohshima et al 2010). 2b).…”

“…1), coastal polynyas are formed by divergent ice drift associated with prevailing cold offshoreward wind (Martin et al 1998). Nakanowatari et al (2007) suggested that, during the past 50 yr, warming of the intermediate water and weakening of the overturning have occurred in the northwestern North Pacific, originating from the Sea of Okhotsk. Nakanowatari et al (2007) suggested that, during the past 50 yr, warming of the intermediate water and weakening of the overturning have occurred in the northwestern North Pacific, originating from the Sea of Okhotsk.…”

Four-dimensional variational ocean reanalysis: a 30-year high-resolution dataset in the western North Pacific (FORA-WNP30)

“…26 we plot the lag correlation maps between the sea ice extent of the Okhotsk Sea in March and SST in the preceding October to December. As shown by Nakanowatari et al (2010), the correlation maps indicate that SST off the east coast of Kamchatka Peninsula in autumn has a large negative correlation with the sea ice extent in the subsequent winter. It is also worth emphasizing that the area with high correlation coefficients in FORA, which is confined along EKC compared to the maps in Nakanowatari et al (2010), moves southwestward along EKC and a part of the correlation signal enters the southeastern part of the Okhotsk Sea through straits along the Kuril Islands, where there is large interannual variability in the sea ice extent.…”

“…It is also worth emphasizing that the area with high correlation coefficients in FORA, which is confined along EKC compared to the maps in Nakanowatari et al (2010), moves southwestward along EKC and a part of the correlation signal enters the southeastern part of the Okhotsk Sea through straits along the Kuril Islands, where there is large interannual variability in the sea ice extent. These features in FORA support a hypothesis proposed by Nakanowatari et al (2010) that the interannual variability of the sea ice extent in the Okhotsk Sea is influenced by advection of temperature anomalies by EKC.…”

“…A recent study by Nakanowatari et al (2010) pointed out that the maximum sea ice extent in the Okhotsk Sea is highly correlated with SST around the EKC region in the preceding autumn. To confirm this relation using the FORA data, in Fig.…”