Event-scale Internal Tide Variability via X-band Marine Radar

TL;DR

This study combines high-resolution marine radar remote sensing with in situ measurements to analyze the variability and dynamics of internal tides and internal waves across the inner shelf, revealing complex behaviors and deviations from linear theory.

Contribution

It introduces a novel integrated approach using radar and in situ data to track internal tide packets and analyze their variability and shoaling behavior.

Findings

Radar-estimated wave speeds match in situ measurements.

Internal tide shoaling deviates from linear theory.

Observed internal wave polarity reversal.

Abstract

A combined radar remote sensing and in situ data set is used to track packets of nonlinear internal waves as they propagate and shoal across the inner shelf (40m - 9m). The dataset consists of high space-time resolution (5m, 2min) radar image time series collected over a 10km radial footprint, with over a dozen synchronous and co-located moorings measuring temperature, salinity, and velocity throughout the water column. The internal bores and higher-frequency internal waves that make up the internal tide are tracked in the radar image time series and, therefore, provide continuous cross-shore speed and angle estimates as the waves propagate across the inner shelf. We compare radar-estimated speeds to those estimated from moorings and confirm a cross-shore shoaling profile that deviates from linear theory. We additionally use combined remote sensing and in situ data to perform a detailed analysis on four consecutive internal tides. These analyses reveal intra-packet speed variability, tide-tide influences, reflected internal waves, and an instance of internal wave polarity reversal observed in the radar and moorings.