history in the EBS shelf environment which is characterized by much weaker and
less organized currents. Trajectories of the Unimak Pass particles with the largest
residence times (τ ∼ 35–40 months) shown in Fig. 8b first wander around the
southern EBS shelf west of the Pribilof Islands, and then slowly proceed north
following the Spanberg Strait pathway to the Arctic Ocean. Only a small fraction of
these particles join the Anadyr Current far downstream, and they are never engaged
in the eddy-induced exchange with the BSC. The same property characterizes the
fastest particles populating the left peak (τ < 11 months) of the Unalaska distribution in Fig. 8b. These particles strictly follow the main stream of the BSC and
Anadyr Current.
Summary
We presented a systematic approach for developing a regional DAS as applied to
the Bering Sea. The method is based on applying the 4dVar technique to both
climatological and instantaneous data with the ultimate goal of reconstructing
dynamically and statistically consistent states at various temporal and spatial scales:
from large-scale interannual circulation to eddy resolving transient current systems.
The backbone of the system are dynamically balanced seasonal climatological
states and the corresponding MDOT of the Bering Sea, which distinguishes the
developed Bering Sea DAS from other regional systems developed in the last
decade, such as for the Oregon Coast by Kurapov et al. [8], and for the Hawaiian
Islands by Janekovich et al. [6].
The developed seasonal climatologies of the Bering Sea include dynamically
consistent temperature, salinity, velocity, and sea surface height fields for each
season (winter, fall, spring and summer) and the corresponding fields for the climatological mean state of the Bering Sea. These climatologies have sufficiently fine
resolution to allow accurate specification of the dynamically balanced background
state for any subregion of the Bering Sea. An important by-product is the
high-resolution regional MDOT, whose accuracy and quality significantly outperforms the other MDOTs derived from various global reanalyses.
Combining the developed Bering Sea MDOT with instantaneous satellite
altimetry data provided an important observational constraint on the regional
dynamics in the entire Bering Sea. The 4dVar assimilation of satellite altimetry
anomalies referenced to the 4Dvar MDOT provides much better estimates of the
transport through the Aleutian Passes. These flows control the supply of nutrients to
the Bering Sea, affect the stability of the Aleutian North Slope Current and the
process of eddy formation along the Aleutian Arc, which is an important component of local ecosystem dynamics.
The seasonal climatologies were also used to constrain a more detailed and
comprehensive study of the EBS circulation in 2007–2010 by means of the nested
4dVar DAS developed by Panteleev et al. [25]. Comparison with the
BESTMASS DA system of Lindsay and Zhang [10] has shown that the new DAS
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G. G. Panteleev et al.
less organized currents. Trajectories of the Unimak Pass particles with the largest
residence times (τ ∼ 35–40 months) shown in Fig. 8b first wander around the
southern EBS shelf west of the Pribilof Islands, and then slowly proceed north
following the Spanberg Strait pathway to the Arctic Ocean. Only a small fraction of
these particles join the Anadyr Current far downstream, and they are never engaged
in the eddy-induced exchange with the BSC. The same property characterizes the
fastest particles populating the left peak (τ < 11 months) of the Unalaska distribution in Fig. 8b. These particles strictly follow the main stream of the BSC and
Anadyr Current.
Summary
We presented a systematic approach for developing a regional DAS as applied to
the Bering Sea. The method is based on applying the 4dVar technique to both
climatological and instantaneous data with the ultimate goal of reconstructing
dynamically and statistically consistent states at various temporal and spatial scales:
from large-scale interannual circulation to eddy resolving transient current systems.
The backbone of the system are dynamically balanced seasonal climatological
states and the corresponding MDOT of the Bering Sea, which distinguishes the
developed Bering Sea DAS from other regional systems developed in the last
decade, such as for the Oregon Coast by Kurapov et al. [8], and for the Hawaiian
Islands by Janekovich et al. [6].
The developed seasonal climatologies of the Bering Sea include dynamically
consistent temperature, salinity, velocity, and sea surface height fields for each
season (winter, fall, spring and summer) and the corresponding fields for the climatological mean state of the Bering Sea. These climatologies have sufficiently fine
resolution to allow accurate specification of the dynamically balanced background
state for any subregion of the Bering Sea. An important by-product is the
high-resolution regional MDOT, whose accuracy and quality significantly outperforms the other MDOTs derived from various global reanalyses.
Combining the developed Bering Sea MDOT with instantaneous satellite
altimetry data provided an important observational constraint on the regional
dynamics in the entire Bering Sea. The 4dVar assimilation of satellite altimetry
anomalies referenced to the 4Dvar MDOT provides much better estimates of the
transport through the Aleutian Passes. These flows control the supply of nutrients to
the Bering Sea, affect the stability of the Aleutian North Slope Current and the
process of eddy formation along the Aleutian Arc, which is an important component of local ecosystem dynamics.
The seasonal climatologies were also used to constrain a more detailed and
comprehensive study of the EBS circulation in 2007–2010 by means of the nested
4dVar DAS developed by Panteleev et al. [25]. Comparison with the
BESTMASS DA system of Lindsay and Zhang [10] has shown that the new DAS
514
G. G. Panteleev et al.