Interannual variations of Dense Shelf Water in the Sea of Okhotsk affected by oceanic freshwater transport in the North Pacific subpolar gyre
Abstract
We use a new hydrographic dataset to investigate the effect of oceanic freshwater (salt) transport on the interannual variations of Dense Shelf Water (DSW) formation in the Sea of Okhotsk. DSW is formed by brine rejection due to sea-ice production in the northern shelf of the Sea of Okhotsk and is transported to the intermediate layer after its formation. DSW is one of the source waters of the North Pacific Intermediate Water so that it contributes to the North Pacific ventilation and plays a role in the global thermohaline circulation. DSW formation and advection also leads to the transport of the materials such as carbon and iron. The Sea of Okhotsk is notorious for its poor availability of the observation data. The new dataset contains the Russian hydrographic observations in the Sea of Okhotsk and Bering Sea, which enables us to study the DSW variations and their causes. The time series of DSW salinity and potential density show that they have the decreasing trends since 1950 as well as the significant interannual variations. The trends are consistent with observed decreasing of sea-ice extent due to air-temperature rise over Siberia. We suggest that the advection of salinity anomalies (freshwater transport) from the Bering Sea changes the surface layer salinity in the northern shelf of the Sea of Okhotsk and preconditions the DSW variations. Formation mechanisms for the salinity anomalies in the Bering Sea are also discussed. These results suggest that we need to improve the salinity distributions reproduced in numerical models to predict the changes in the ventilation and overturning in the North Pacific under the influence of the strengthened hydrological cycle in future.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2012
- Bibcode:
- 2012AGUFMOS33C1836U
- Keywords:
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- 4200 OCEANOGRAPHY: GENERAL;
- 4215 OCEANOGRAPHY: GENERAL / Climate and interannual variability;
- 4283 OCEANOGRAPHY: GENERAL / Water masses;
- 4500 OCEANOGRAPHY: PHYSICAL