Evidence for local and nonlocal barotropic responses to atmospheric forcing during BEMPEX

Abstract

The coherence between single bottom pressure and barotropic velocity records collected in the North Pacific during BEMPEX and air pressure, wind stress, and stress curl derived from FNOC products are examined over the 200‐1 day period band. Strong coherence between the bottom pressure and all atmospheric variables is seen, nonlocal coherence (maximum up to 1000 km to the southeast) dominating at periods longer than ≈10 d and coherence being prevalent at shorter periods, consistent with predictions from existing models of atmospherically‐forced barotropic motion. The azimuth of the nonlocal coherence maximum relative to the ocean station is a function of frequency, which is not expected from the models. The coherence between the barotropic velocity (as measured by the electric field) and the atmospheric variables is weaker, but nonlocal coherence with the wind stress and wind stress curl at periods greater than a week, and local coherence with the wind stress at shorter periods, is statistically significant.