Numerical study of the spatial distribution of the M₂ internal tide in the Pacific Ocean

TLDR

The study aims to clarify the distribution of the M₂ internal tide in the Pacific Ocean. This is achieved by employing a three‑dimensional primitive equation numerical model. The simulation shows that energetic M₂ internal tides are generated mainly over prominent Pacific topographic features, with a total conversion rate of 338 GW (84 % from these features), a 2–3‑order‑of‑magnitude higher energy level in the western and central Pacific compared to the east, agreement with altimetric observations, and a need for extensive microstructure measurements in those regions.

Abstract

As a first step toward numerical modeling of global internal tides, we clarify the distribution of the M 2 internal tide in the Pacific Ocean using a three‐dimensional primitive equation numerical model. The numerical simulation shows that energetic internal tides are generated over the bottom topographic features in the Indonesian Archipelago, the Solomon Archipelago, the Aleutian Archipelago, and the Tuamotu Archipelago, the continental shelf slope in the East China Sea, and the mid‐oceanic ridges such as the Izu‐Ogasawara Ridge, the Hawaiian Ridge, the Norfolk Ridge, the Kermadec Ridge, and the Macquarie Ridge. The calculated spatial patterns of the M 2 internal tide around the Hawaiian Ridge and the Izu‐Ogasawara Ridge agree well with the TOPEX/Poseidon altimetric observation. The conversion rate from the M 2 surface to internal tide energy integrated over the whole model domain amounts to 338 GW (1 GW = 10 9 W), 84% of which are found to be generated over the prominent topographic features mentioned above. Reflecting the spatial distribution of the prominent topographic features in the Pacific Ocean, the energy level of the M 2 internal tide in the western and central Pacific is 2–3 orders of magnitude higher than that in the eastern Pacific. This remarkable asymmetry shows that extensive microstructure measurements in the western and central Pacific are indispensable to determining the representative value of diapycnal mixing rates in the global ocean.