06.12.2021: Ocean Circulation and Climate Dynamics Colloquium

When?     Monday, 6. Dezember 2021 at 10 am
Where?    ZOOM meeting room: https://geomar-de.zoom.us/j/83964333722?pwd=MWloRytEU01YSmhZUmFHUjBwWkdQQT09

Meeting-ID: 839 6433 3722
Kenncode: 145710

Abstract:
Embedded in the deep ocean circulation in the subpolar North Atlantic is the lower limb of the Atlantic Meridional Overturning Circulation (AMOC). Its circulation pathway and variability have critical impacts on the spreading and mixing of high latitude climate signals in the deep ocean. However, due to relatively sparse observational data, current understanding on the large-scale deep circulation is limited. In this study, using direct velocity measurements from 121 subsurface acoustically tracked RAFOS floats, we have constructed gridded fields of mean velocity and eddy kinetic energy (EKE) in the deep (1800-2800 dbar) subpolar North Atlantic. The mean velocity field reveals a relatively strong deep boundary current around Greenland and the Labrador Basin, with a weaker deep boundary current over the eastern flank of the Reykjanes Ridge, and near-zero mean flow over the western flank – the latter feature contrasting with historical depictions of a continuous deep boundary current encircling the three basins of the subpolar North Atlantic. Over most of the subpolar basin, deep EKE resembles that at the surface, albeit with smaller magnitudes. A surprising finding about deep EKE is an elevated EKE band east of Greenland. This EKE band is attributed to the propagating Denmark Strait Overflow Cyclones and variability of the wind-driven recirculation branch, possibly suggesting enhanced lateral exchange in this region. The float-based flow fields constructed in this study provide an unprecedented view on the kinematic properties of the large-scale deep circulation in the subpolar North Atlantic.

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