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Abstract Hydrographic and velocity data from a 2018 winter survey of the western Iceland and Greenland Seas are used to investigate the ventilation of overflow water feeding Denmark Strait. We focus on the two general classes of overflow water: warm, saline Atlantic‐origin Overflow Water (AtOW) and cold, fresh Arctic‐origin Overflow Water (ArOW). The former is found predominantly within the East Greenland Current (EGC), while the latter resides in the interior of the Iceland and Greenland Seas. Progressing north to south, the properties of AtOW in the EGC are modified diapycnally during the winter, in contrast to summer when along‐isopycnal mixing dominates. The water column response to a 10‐days cold‐air outbreak was documented using repeat observations. During the event, the northerly winds pushed the freshwater cap of the EGC onshore, and convection modified the water at the seaward edge of the current. Lateral transfer of heat and salt from the core of AtOW in the EGC appears to have influenced some of this water mass transformation. The long‐term evolution of the mixed layers in the interior was investigated using a 1‐D mixing model. This suggests that, under strong atmospheric forcing, the densest component of ArOW can be ventilated in this region. Numerous anti‐cyclonic eddies spawned from the EGC were observed during the winter survey, revealing that these features can play differing roles in modifying/prohibiting the open‐ocean convection.
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Demons in the North Atlantic: Variability of Deep Ocean Ventilation
Abstract Translation of atmospheric forcing variability into the ocean interior via ocean ventilation is an important aspect of transient climate change. On a seasonal timescale in the subtropics, this translation is mediated by a so‐called “Demon” that prevents access to all except late‐winter mixed‐layer water. Here, we use an eddy‐permitting numerical circulation model to investigate a similar process operating on longer (interannual) timescales in the subpolar North Atlantic. We find that variations in atmospheric forcing are mediated in their translation to the ocean interior, with year‐to‐year changes in the late‐winter mixed layer depth being the critical factor. The signature of persistent strong atmospheric forcing driving deep mixed layers is preferentially ventilated to the interior when the forcing is ceased. Susceptibility to this effect depends on the location and density of subduction—with the rate at which newly ventilated water escapes its region of subduction being the crucial factor.
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- Award ID(s):
- 1936222
- PAR ID:
- 10375588
- Publisher / Repository:
- DOI PREFIX: 10.1029
- Date Published:
- Journal Name:
- Geophysical Research Letters
- Volume:
- 48
- Issue:
- 9
- ISSN:
- 0094-8276
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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