Subglacial Discharge Reflux and Buoyancy Forcing Drive Seasonality in a Silled Glacial Fjord

Fjords are conduits for heat and mass exchange between tidewater glaciers the coastal ocean, thus regulate near-glacier water properties submarine melting of glaciers. Entrainment into subglacial discharge plumes is a primary driver seasonal glacial fjord circulation; however, outflowing may continue to influence circulation after reaching neutral buoyancy through sill-driven mixing recycling, or reflux, freshwater. Despite its importance in non-glacial fjords, no framework exists how freshwater reflux affect where strong forcing also present. Here, we pair suite hydrographic observations measured throughout 2016–2017 LeConte Bay, Alaska, with three-dimensional numerical model quantify freshwater, determine on circulation. When paired plume-driven forcing, sill-generated drives distinct regimes that differ greatly their ability transport glacier terminus. During summer, 53%–72% surface outflow refluxed at fjord's shallow entrance sill subsequently re-entrained plume head. As result, near-terminus heavily influenced by sill, altered draw warm, modified external grounding line 200 m depth. This circulatory cell does not exist winter when minimal. Similar behavior other fjords Southeast Patagonia, Greenland, elsewhere.