11:00 〜 13:00
[ACG36-P04] A Relationship between Daily Variability of Surface Current Velocity in Soya Strait and Sea-Ice Distribution near East Coast of Hokkaido in Ice-Ocean Coupled Regional Ocean Model
キーワード：東サハリン海流、宗谷暖流、領域海氷海洋結合モデル、オホーツクタワー、宗谷海峡
The East Sakhalin Current (ESC)/the Soya Warm Current (SWC) is a coastal boundary current that flows along the east coast of Sakhalin/the west coast of Hokkaido into the Sea of Okhotsk (Ebuchi, 2006; Ebuchi et. al., 2009). The nearshore core of the wind driven ESC is explained as arrested topography wave (Shimizu and Ohshima, 2002). The pathway of the ESC along the east coast divide into two directions at the south of Sakhalin Island (Ohshima, 1994). A part of ESC flows to the Sea of Japan direction through the Soya Strait, another part of ESC flows to the east coast of Hokkaido. On the other hand, a part of SWC along west coast of Hokkaido flows into the Sea of Okhotsk from the Sea of Japan through the Soya Strait. Thus, these currents pass by each other to the opposite direction in the Soya Strait. In fact, the direction of surface flow in the Soya Strait often turns through the winter season.
In this study, we use the result of the ice-coupled Regional Ocean Modeling System (iROMS) which is one of the community ocean general circulation models. This model horizontal resolution is 10km×10km, and it has the vertical 48 layers. First, we focus on the direction of the surface current in the Soya Strait. We assume that the impact of the SWC/ESC strength becomes stronger when the east-west component of the surface current in the Soya Strait is eastward/westward. Basically, sea-ice distribution in the east coast of Hokkaido is impacted by the drift ice from the north of the Okhotsk Sea by the ESC with low temperature. In contrast, the ESC has high salinity and high temperature. Therefore, if the ESC strength will be stronger, the sea-ice distribution in the east coast of Hokkaido may be impacted by the ESC with high salinity and temperature. Therefore, we consider that the contribution of the eastern coastal area of Hokkaido by the surface water of the SWC.
As the results of our simulation, the daily variability of the surface flow direction in the Soya Strait is large through the winter season, thus we investigate that the daily variability of the Sea Surface Salinity (SSS) which may characterize ESC and SWC currents in the Soya Strait. Further, we examine the daily variability along the east coast of Hokkaido. In consequence, we found that the daily variability of SSS in the Soya Strait responds with respect to the daily variability along the east of Hokkaido with several days lag. Especially, we may confirm that our simulation result is well coincide with the observation result of the Okhotsk Tower (Monbetsu city) along the east coast of Hokkaido. Therefore, we consider that the daily SSS variability impact by both ESC and SWC propagate along the east coast of Hokkaido from the Soya Strait. In fact, we also confirm that the correlation coefficient is high along the east coast of Hokkaido with respect to the SSS variability in the Soya Strait.
Further, we assume that if the SSS varies lower/higher from the average in the Soya Strait, the index of ESC/SWC strength may be larger. Then, we investigate the interannual variability of the coastal total ice volume for four months (JFMA). As the result, we found that if the coastal ice volume is larger/smaller, the index of ESC/SWC strength tends to larger.
In this study, we use the result of the ice-coupled Regional Ocean Modeling System (iROMS) which is one of the community ocean general circulation models. This model horizontal resolution is 10km×10km, and it has the vertical 48 layers. First, we focus on the direction of the surface current in the Soya Strait. We assume that the impact of the SWC/ESC strength becomes stronger when the east-west component of the surface current in the Soya Strait is eastward/westward. Basically, sea-ice distribution in the east coast of Hokkaido is impacted by the drift ice from the north of the Okhotsk Sea by the ESC with low temperature. In contrast, the ESC has high salinity and high temperature. Therefore, if the ESC strength will be stronger, the sea-ice distribution in the east coast of Hokkaido may be impacted by the ESC with high salinity and temperature. Therefore, we consider that the contribution of the eastern coastal area of Hokkaido by the surface water of the SWC.
As the results of our simulation, the daily variability of the surface flow direction in the Soya Strait is large through the winter season, thus we investigate that the daily variability of the Sea Surface Salinity (SSS) which may characterize ESC and SWC currents in the Soya Strait. Further, we examine the daily variability along the east coast of Hokkaido. In consequence, we found that the daily variability of SSS in the Soya Strait responds with respect to the daily variability along the east of Hokkaido with several days lag. Especially, we may confirm that our simulation result is well coincide with the observation result of the Okhotsk Tower (Monbetsu city) along the east coast of Hokkaido. Therefore, we consider that the daily SSS variability impact by both ESC and SWC propagate along the east coast of Hokkaido from the Soya Strait. In fact, we also confirm that the correlation coefficient is high along the east coast of Hokkaido with respect to the SSS variability in the Soya Strait.
Further, we assume that if the SSS varies lower/higher from the average in the Soya Strait, the index of ESC/SWC strength may be larger. Then, we investigate the interannual variability of the coastal total ice volume for four months (JFMA). As the result, we found that if the coastal ice volume is larger/smaller, the index of ESC/SWC strength tends to larger.