Chapter 6 - The presence and importance of internal mixing processes in the Arctic Ocean

Abstract

The Arctic Ocean is strongly stratified in its upper part, and surface-generated mechanical turbulence is restricted to a shallow upper layer. The seasonal buoyancy loss and gain induce mixing and stirring extending deeper in winter but limit the turbulence to the uppermost layers in summer. The deeper part of the Arctic Ocean is thus almost isolated from the surface forcing, and mixing processes using other energy sources gain in importance and generate the water mass transformations that are observed in the deeper parts of the water column. The chapter is focused on double-diffusive processes, and in contrast to other chapters in this book, I do not here try to review in detail different attempts to describe thermohaline intrusions and staircases in the Arctic Ocean and the efforts to explain their formation and importance. Most of this chapter is based on studies in which I have taken part, and the views and the in-depth discussions of the effects of double-diffusive convection given here are personal. They start from how staircases and intrusions appear in the Arctic Ocean water column and how these observed features can be related to different theoretical explanations about their formation. However, sufficient references to other views about how these processes arise and evolve are given, where the interested reader can find other explanations for the formation, expansion, and importance of thermohaline interleaving.