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| Titel |
Recruitment to the Ekman drain from the shelf edge to the west of Scotland |
| VerfasserIn |
Andrew Dale, Jaimie Cross, Phil Hosegood, Mark Inall |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250099411
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| Publikation (Nr.) |
 EGU/EGU2014-15186.pdf |
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| Zusammenfassung |
| A persistent, but somewhat variable, slope current flows poleward along the shelf edge to the
west of Scotland. It has been proposed that the downslope Ekman transport on the base of the
slope current represents a significant export of water and suspended material from the shelf.
The detailed dynamics of this ‘Ekman drain’ remain poorly understood, however. This largely
reflects uncertainty surrounding the source of the fluid and material within the drain, and also
concerning the interaction between this water and more strongly-stratified overlying water.
Here we examine one aspect of this system: recruitment to the Ekman drain as stratified
water is drawn into the bottom boundary layer on the shelfward flank of the slope
current.
During the summer of 2013, as part of a concerted study of shelf edge exchange in this
region (the FASTNEt project), a dye tracer was injected into the water column at mid depth
near the shelf break, close to the 200 m isobath. This was within the shelfward flank of the
slope current. The resulting dye patch was tracked for more than 4 days as it advected
alongslope, remaining close to the 200 m isobath, at a mean speed of around 8 cm s-1. The
cross-slope shear on this flank of the slope current implies a divergent bottom Ekman
transport, which in turn requires a balancing downward flux. The dye-laden water was seen to
deepen with time, at around 10 m day-1. It also crossed density surfaces, with its
density increasing until it was entrained into the 50-100 m thick bottom boundary
layer. Microstructure data collected during dye tracking help to clarify the vertical
advective-diffusive behaviour of the dye-laden water during its modification and ultimate
entrainment. |
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