Quantification of uncertainty due to spectral parameterization of topography in deep-ocean lee waves *

Stratified, steady geostrophic flow impinging on bottom topography generates oceanic lee waves. Their generation causes drag on the current, which is often parameterized in global circulation models with use of the topographic spectrum. Because a significant portion of the ocean floor is unmapped at resolutions sufficient to generate lee waves, a spectral model of the dominant bathymetric feature, the abyssal hills, is used. This study aims to quantify the uncertainty of lee wave drag prediction associated with the spectral model, which involves five uncertain physical parameters. We use three models along with the spectral model to compute wave drag: Linear theory, inviscid nonlinear theory (Long’s model) and CFD (using the SUNTANS ocean model). For each of the three models, we test the sensitivity of the five parameters in the spectral model. In SUNTANS simulations, we apply the spectral model by inverting a regional multibeam bathymetric dataset. Comparing uncertainties in wave drag of the three simulation sets will shed light on how uncertainty propagates from the topographic spectrum to the lee wave flow field, and thus guide the parameterization of lee waves in global circulation models.