Since the seminal work of Walter Munk in the 1960s ('Abyssal Recipes'), oceanographers have believed that the upwelling of cold, abyssal waters that regulates the deep ocean's ability to sequester heat and carbon for decades to millennia is mainly driven by centimetre-scale turbulent mixing associated with breaking internal waves in the ocean interior. Measurements of deep-ocean turbulence over the last >20 years, however, have contested this scenario, and instead suggest that mixing by breaking internal waves drives *downwelling* of abyssal waters. Inspired by this conundrum, recent theoretical investigations have developed an alternative view of the role of mixing in sustaining deep-ocean upwelling. In this new view, upwelling is driven by highly localised turbulence within thin (typically tens of metres thick) layers near the seafloor, known collectively as the bottom boundary layer. In the BLT Recipes experiment, we recently set out to test this new view, and figure out how it works, by obtaining the first set of concurrent, systematic measurements of (1) large-scale mixing and upwelling, (2) their interior and bottom boundary layer contributions, and (3) the processes underpinning these contributions, in a representative deep-ocean basin (the Rockall Trough, in the Northeast Atlantic). This talk will review the insights emerging from the BLT Recipes experiment, and offer an outlook on how they might re-shape our understanding of the way in which turbulence sustains deep-ocean upwelling.

How to cite: Naveira-Garabato, A. C.: Rewriting the tale of deep-ocean upwelling, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16418, https://doi.org/10.5194/egusphere-egu23-16418, 2023.

The North Atlantic exhibits temperature variations on multidecadal time scales, summarized as the Atlantic Multidecadal Variability (AMV). The AMV plays an essential role in regional climate and is a crucial driver of the low-frequency variability in Northern Europe.

In this talk, I will first discuss the characteristic ocean-atmosphere interaction preceding an AMV maximum event. In the following, I will disentangle the seasonal impact of the AMV and show that a significant fraction of the variability in Baltic Sea winter temperatures is related to the AMV. The strong winter response can be linked to the interaction between the North Atlantic Oscillation, the Atlantic Meridional Overturning Circulation (AMOC), and the AMV. In contrast, the AMVs' impact on other seasons remains small.

How to cite: Börgel, F., Meier, H. E. M., Gröger, M., Dutheil, C., Rhein, M., Borchert, L., and Radtke, H.: Atlantic Multidecadal Variability and the Implications for North European climate, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9125, https://doi.org/10.5194/egusphere-egu23-9125, 2023.