M2 Internal Tide Energetics and Behaviors in the Subpolar North Pacific

Abstract

Abstract Energetic internal tides in the Pacific Ocean generated from multiple sources are the subject of many studies, although the subpolar North Pacific (SNP) is known as a high-latitude hotspot that remains less explored. The present study is the first detailed investigation on M2 internal tide energetics and dynamics in the SNP by high-resolution numerical simulations. The M2 internal tides in the SNP mainly originate from the Aleutian Ridge (area-integrated 5.51 GW and averaged ∼10−3 W m−2 of barotropic-to-baroclinic conversion rate), wherein the Amukta Pass is the most significant source. The Amukta Pass radiates northward 0.55 GW (averaged 2.3 kW m−1) to the Bering Sea and southward 1.40 GW (averaged 3.7 kW m−1) to the North Pacific. The subsequent south–north asymmetric radiation pattern is consistent with satellite altimeter detection. In the Bering basin, multiwave superposition in the near field between the Amukta Pass and adjacent sources generates two standing wave patterns. After approaching the Bering Sea slope, remote internal tides from Aleutian Ridge enhance local generation and dissipation. The dissipation field is relatively similar to the generation map, which is explained by the higher local dissipation efficiency q (>1/2) and the faster energy attenuation than in the midlatitudes. The simulated dissipation rates compare favorably with the estimate from fine-scale parameterization, indicating the dominance of internal tidal mixing. The averaged dissipation rate in SNP is O(10−10) W kg−1, and the depth-integrated dissipation rates reach O(10−1) W m−2 near the Amukta Pass. It is important to understand the unique physics and dissipative process of high-latitude internal tides to fully characterize the redistribution of global tidal energy and associated mixing.