The role of tides in bottom water export from the western Ross Sea

Melissa M Bowen,Denise Fernandez,Aitana Forcen-Vazquez,Arnold L Gordon,Pierpaolo Falco,Bruce Huber,Pasquale Castagno

doi:10.1038/s41598-021-81793-5

Abstract

Approximately 25% of Antarctic Bottom Water has its origin as dense water exiting the western Ross Sea, but little is known about what controls the release of dense water plumes from the Drygalski Trough. We deployed two moorings on the slope to investigate the water properties of the bottom water exiting the region at Cape Adare. Salinity of the bottom water has increased in 2018 from the previous measurements in 2008–2010, consistent with the observed salinity increase in the Ross Sea. We find High Salinity Shelf Water from the Drygalski Trough contributes to two pulses of dense water at Cape Adare. The timing and magnitude of the pulses is largely explained by an inverse relationship with the tidal velocity in the Ross Sea. We suggest that the diurnal and low frequency tides in the western Ross Sea may control the magnitude and timing of the dense water outflow.

Highlights

25% of Antarctic Bottom Water has its origin as dense water exiting the western Ross Sea, but little is known about what controls the release of dense water plumes from the Drygalski Trough
We investigated what proportion of water from the Drygalski Trough is needed to create the salinity and temperature observed at Cape Adare every month during the Ross sea outflow (RSO) deployment (Fig. 4)
The two co-located mooring deployments at Cape Adare show dense water appearing twice a year with highest salinities measured in March

Summary

Introduction

25% of Antarctic Bottom Water has its origin as dense water exiting the western Ross Sea, but little is known about what controls the release of dense water plumes from the Drygalski Trough. Salinity of the bottom water has increased in 2018 from the previous measurements in 2008–2010, consistent with the observed salinity increase in the Ross Sea. We find High Salinity Shelf Water from the Drygalski Trough contributes to two pulses of dense water at Cape Adare. The water properties of the bottom water from the western Ross Sea are primarily set by dense shelf water plumes exiting the Drygalski and Glomar Challenger Troughs. The dense plumes descend over the continental slope and mix with the warmer Circumpolar Deep Water (CDW)[8,9,10] to exit the region as AABW to the northwest at Cape A dare[11]. Exchange flow varies markedly with the strength of the tides in many estuaries[25,26] and reduction

Methods

Results

Conclusion