Abstract
Satellite observations are used to establish the dominant magnitudes,
scales, and mechanisms of intraseasonal variability in ocean dynamic sea
level (ζ) in the Persian Gulf over 2002-2015. Empirical orthogonal
function (EOF) analysis applied to altimetry data reveals a basin-wide,
single-signed intraseasonal fluctuation that contributes importantly to
ζ variance in the Persian Gulf at monthly to decadal timescales. An EOF
analysis of Gravity Recovery and Climate Experiment (GRACE) observations
over the same period returns a similar large-scale mode of intraseasonal
variability, suggesting that the basin-wide intraseasonal ζ variation
has a predominantly barotropic nature. A linear barotropic theory is
developed to interpret the data. The theory represents
Persian-Gulf-average ζ () in terms of local freshwater flux, barometric
pressure, and wind stress forcing, as well as ζ at the boundary in the
Gulf of Oman. The theory is tested using a multiple linear regression
with these freshwater flux, barometric pressure, wind stress, and
boundary ζ quantities as input, and as output. The regression explains
70% +/- 9% (95% confidence interval) of the intraseasonal variance.
Numerical values of regression coefficients computed empirically from
the data are consistent with theoretical expectations from the theory.
Results point to a substantial non-isostatic response to surface
loading. The Gulf of Oman ζ boundary condition shows lagged correlation
with ζ upstream along the Indian Subcontinent, Maritime Continent, and
equatorial Indian Ocean, suggesting a large-scale Indian-Ocean influence
on intraseasonal variation mediated by coastal and equatorial waves, and
hinting at potential predictability. This study highlights the value of
GRACE for understanding sea level in an understudied marginal sea.