Elucidating large-scale atmospheric controls on Bering Strait
throughflow variability using a data-constrained ocean model and its
A data-constrained coupled ocean-sea ice general circulation model and
its adjoint are used to investigate mechanisms controlling the volume
transport variability through the Bering Strait from 2002 to 2013.
Comprehensive time-resolved sensitivity maps of the Bering Strait
transport to atmospheric forcing can be accurately computed with the
adjoint along the forward model trajectory to identify the spatial and
temporal scales most relevant to the strait’s transport variability. The
model’s Bering Strait transport anomaly is found to be controlled
primarily by the wind stress on short time-scales of order 1 month.
Spatial decomposition indicates that on monthly time-scales winds over
the Bering and the combined Chukchi and East Siberian Seas are the most
significant drivers. Continental shelf waves and coastally-trapped waves
are suggested as the dominant mechanisms for propagating information
from the far field to/from the strait. In years with transport extrema,
eastward wind stress anomalies in the Arctic sector are found to be the
dominant control, with correlation coefficient of 0.94. This implies
that atmospheric variability over the Arctic plays a substantial role in
determining the Bering Strait flow variability. The near-linear response
of the transport anomaly to wind stress allows for predictive skill at
interannual time-scales, thus potentially enabling skillful prediction
of changes at this important Pacific-Arctic gateway, provided that
accurate measurements of surface winds in the Arctic can be obtained.
The novelty of this work is the use of space and time-resolved
adjoint-based sensitivity maps, which enable detailed dynamical, i.e.
causal attribution of the impacts of different forcings.