Mixing processes in the changing Arctic Ocean

• Main Author: Peterson, Algot Kristoffer
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: The University of Bergen 2017
• Subjects: VDP::Matematikk og Naturvitenskap: 400::Geofag: 450; Arctic; Arctic Ocean; Svalbard; Yermak Plateau; albedo; Sea ice; Yermak plateau
• Online Access: https://hdl.handle.net/1956/16781

The Arctic has undergone tremendous changes the last decades, including a strong decline in sea ice extent and thickness. The rapid pace of Arctic changes relative to the global changes are known as Arctic amplification, and has been referred to as the ‘canary in the coalmine’ of the present climate changes. Factors contributing to the accelerated changes are the ice-albedo effect, and the vast heat reservoir of Atlantic water flowing in the ocean below. This study has aimed to describe and quantify the influence of oceanic heat on the heat budget at the ocean’s upper boundary. There is a delicate heat balance at the interface between the atmosphere, the sea ice and the ocean. A small change in heat flux can have large effect on the ice cover. While the Arctic Ocean is generally not a very energetic one, the recent changes has raised concern about whether internal wave energy and the importance of vertical mixing processes are increasing. Reductions in sea ice extent may allow for more momentum transfer from the atmosphere to the ocean, either mixing the surface layer directly, or initiating inertial oscillations in the boundary layer. Near-inertial internal waves may propagate into the interior and cause mixing away from the surface boundary layer. An increase in vertical mixing in the Arctic Ocean may bring up more heat from the underlying warm Atlantic Water, posing a further threat to the diminishing Arctic sea ice. The study is based on observations from two different campaigns, both located in the region north of Svalbard. First, under-ice boundary layer and upper ocean measurements made during the winter-to-spring drift campaign N-ICE2015. Second, a yearlong deployment of three moorings on the slope of the Yermak Plateau is used to study the near-inertial wave field by the plateau. From an under-ice turbulence mast, a unique data set of winter-time measurements over the deep basin is obtained. Direct measurements of heat fluxes are weakly positive, even in winter, which are roughly doubled during storm ...