Abstract
Overflow water from the Nordic Seas comprises the deepest limb of the Atlantic Meridional Overturning Circulation, yet questions remain as to where it is ventilated and how it reaches the Greenland-Scotland Ridge. Here we use historical hydrographic data from 2005-2015, together with satellite altimeter data, to elucidate the source regions of the Denmark Strait and Faroe Bank Channel overflows and the pathways feeding these respective sills. A recently-developed metric is used to calculate how similar two water parcels are, based on potential density and potential spicity. This reveals that the interior of the Greenland Sea gyre is the primary wintertime source of the densest portion of both overflows. After subducting, the water progresses southward along several ridge systems towards the Greenland-Scotland Ridge. Kinematic evidence supports the inferred pathways. Extending the calculation back to the 1980s reveals that the ventilation occurred previously along the periphery of the Greenland Sea gyre.
Highlights
Overflow water from the Nordic Seas comprises the deepest limb of the Atlantic Meridional Overturning Circulation, yet questions remain as to where it is ventilated and how it reaches the Greenland-Scotland Ridge
The overflows from the Nordic Seas feed the lower limb of the Atlantic Meridional Overturning Circulation (AMOC), which helps regulate Earth’s climate
There are two general classes of overflow water:[1] (1) “Atlantic-origin” overflow water which is formed by strong air-sea heat loss along the rim current system of the Nordic Seas;[2] and (2) “Arctic-origin” overflow water which stems from the interior basins of the western Nordic Seas where water mass transformation takes place via open-ocean convection[3]
Summary
Overflow water from the Nordic Seas comprises the deepest limb of the Atlantic Meridional Overturning Circulation, yet questions remain as to where it is ventilated and how it reaches the Greenland-Scotland Ridge. We use a comprehensive historical hydrographic dataset of the Nordic Seas, described in the “Methods” section, to elucidate the source regions and pathways of the Arctic-origin overflow water feeding Denmark Strait and the Faroe Bank Channel.
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