CoAuthors

Léon Chafik (Department of Meteorology, Stockholm University, Sweden); Kristofer Döös (Department of Meteorology, Stockholm University, Sweden)

Understanding the impact of oceanic climate variability on shelf seas requires knowledge of their water-mass origins and associated pathways. Furthermore, identifying the dominant driving mechanisms responsible for water-mass variability is an important step towards better predictability of shelf sea properties. To determine the link between the large-scale circulation of the subpolar North Atlantic and the North Sea, we adopt a Lagrangian approach based on satellite altimetry and satellite-derived Ekman velocities. Utilizing these velocity fields, we are able to isolate the changes of water-mass pathways in response to decadal large-scale oceanic variability. In particular, we find that during phases of a strong subpolar gyre, water-masses that are transported into the North Sea follow a comparatively direct path along the subpolar gyre, as well as being faster. Subsequently, northern North Sea water-masses originate from further west in the southern and central subpolar North Atlantic. In contrast, phases of a weak subpolar gyre lead to increased residence times in the north-eastern North Atlantic. We conclude that the subpolar gyre strength is a key predictor of inter-annual variability of North Sea water-mass pathways, origin, and properties.