The Tides of the Glacial Ocean and Their Possible Connection to Heinrich Event Instabilities of the Laurentide Ice Sheet

Abstract

The possibility that Heinrich event 1 (H1), which occurred during the most recent deglaciation event of the current ice age, may have been both triggered and subsequently continuously forced by the tides, is investigated. For the purpose of this investigation, a discontinuous Galerkin method is employed to solve the shallow water tidal equations on the sphere using a nonuniform icosahedral grid to enable high resolution of the Hudson Strait region that was the locus of the ice stream instability that caused H1. Since Heinrich events are known to have involved, for most if not all such events, an instability of the Hudson Strait Ice Stream, an initial representation of H1 has been investigated in which the ice loss is assumed to proceed up the strait to Southampton Island over a period constrained by observations. The tidal energy and dissipation associated with the dominant M2 semidiurnal tide were found to be extremely high relative to their modern strengths prior to H1 but dropped sharply after the instability occurred. A globally averaged (eustatic) sea level rise of approximately 1 m associated directly with this simple model is inferred. The high-amplitude tides at the Atlantic outlet of the Hudson Strait are further demonstrated to track inland with the retreating ice up the strait as the instability of the ice stream migrates inland at a moderate speed consistent with estimates of the inferred instability event duration.