The Evolution of Mesoscale Features in Denmark Strait Overflow

Abstract

Denmark Strait is dynamically relevant to the global climate system because the dense water that overflows through the strait is a major contributor to the Deep Western Boundary Current. Observations show that the Denmark Strait Overflow (DSO) pulses with high frequencies (2-5 days). The hydrography and circulation of our high-resolution numerical simulations covering the east Greenland shelf and the Iceland and Irminger Seas is consistent with available observations in Denmark Strait. The model shows that boluses and pulses, the two dominant mesoscale features observed in the strait, play a major role in controlling the variability of the DSO thickness and transport into the Irminger Sea. Indeed, the mean southward volume flux of the DSO in the model is about 30% greater in the presence of boluses and pulses. In this study we take advantage of our ~2 km resolution model to interpret the sparse observations available for this area. We describe the evolution of boluses and pulses downstream of Denmark Strait by investigating several vertical sections across the east Greenland shelf. Moreover, we use a Lagrangian particle code to track boluses and pulses and to study their hydrographic properties along the descending pathways. Combining the Eulerian and Lagrangian approaches we isolate boluses and pulses from the background state and we investigate the circulation in the Irminger basin associated with the mesoscale features.