28.11.2016: FB1-Seminar

11:00 h, Hörsaal, Düsternbrooker Weg 20

Abstract:

Global numerical ocean models used for climate simulations commonly only consider the ocean's general circulation, but neglect tidal dynamics. However, it has been demonstrated that tidally induced friction at the ocean bottom alters the mean ocean circulation and energy fluxes on timescales larger than one tidal period and up to climate timescales. Thereby the mean ocean circulation and temperature advection are altered and can thus affect climate.

The early Eocene (approx. 56-50 million years ago) was characterized by higher surface temperatures and a smaller meridional temperature gradient than at present. It has been hypothesized that the decreased meridional temperature gradient might be linked to tidally altered heat fluxes. We test this hypothesis by simultaneously modelling tidal dynamics and the general ocean circulation for the early Eocene. Although horizontal velocities are significantly increased in the early Eocene ocean, the oceanic meridional heat transport is only increased by a maximum of 0.1 PW (8%), thus not decreasing the meridional temperature gradient considerably.
While surface temperatures are only marginally affected by tidal forcing in the early Eocene, the present-day atmosphere experiences local increases in 2m-tempertures by up to 4°C. This is caused by a feedback between tidally reduced sea ice concentration and the heat flux between ocean and atmosphere.

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