Transverse structure of tidal and exchange flows in a Magellan glacial fjord

Abstract:

Glacial mass losses in recent decades have sparked attention to the study of glacial fjord hydrodynamics. This is because the fresh water derived from glacier melting contributes to the global rise in sea level. The increased rate of submarine melting in tidewater glaciers has been linked to heat transport from the ocean through fjords. Despite the global relevance of ice melting in glacial fjords, little is known about their dynamics and transverse structure. The objective of this study was to resolve the spatial structure of tidal and exchange flows in a glacial fjord off the Strait of Magellan, Chile. Data from a towed ADCP and from CTD casts were collected along two transects during one semidiurnal tidal cycle in December 2003. Salinity profiles showed an easy-to-miss 3 m buoyant layer over a homogeneous water column. Tidal flows displayed marked transverse and vertical variations caused by geometry and stratification. Residual (or tidally averaged) flows showed the strongest outflow (~0.1 m/s) of buoyant waters on the side of the section most influenced by Coriolis and curvature accelerations. Inflows were only a few centimeters per second, distributed underneath the buoyant outflow.