On stratification, barotropic tides, and secular changes in surface tidal elevations: Two-layer analytical model

TL;DR

This paper presents a two-layer analytical model to study how stratification influences surface tidal elevations, revealing that both large-scale and small-scale tides are affected and that topography significantly modulates this sensitivity.

Contribution

It introduces a framework combining analytical and numerical approaches to understand stratification effects on both barotropic and baroclinic tides and their secular variations.

Findings

Stratification impacts both large-scale and small-scale surface tides.

Topography significantly influences tide sensitivity to stratification.

Numerical model results align qualitatively with analytical predictions.

Abstract

In this study the influence of stratification on surface tidal elevations in a two-layer analytical model is examined. The model assumes linearized, non-rotating, shallow-water dynamics in one dimension with astronomical forcing and allows for arbitrary topography. Using a natural modal separation, both large scale (barotropic) and small scale (baroclinic) components of the surface tidal elevation are shown to be comparably affected by stratification. It is also shown that the topography and basin boundaries affect the sensitivity of the barotropic surface tide to stratification significantly. This paper, therefore, provides a framework to understand how the presence of stratification impacts barotropic as well as baroclinic tides, and how climatic perturbations to oceanic stratification contribute to secular variations in tides. Results from a realistic-domain global numerical two-layer tide model are briefly examined and found to be qualitatively consistent with the analytical model results.