 |
| Titel |
On the shelf water cascading in the Irminger Sea |
| VerfasserIn |
Anastasia Falina, Artem Sarafanov, Alexey Sokov, Herlé Mercier, Pascale Lherminier |
| Konferenz |
EGU General Assembly 2011
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250046617
|
|
|
|
|
|
| Zusammenfassung |
| Descending (cascading) of dense shelf waters down the continental slopes contributes to the
ventilation of intermediate and deep waters at many locations around the world ocean.
Cascading events were observed off the shelves of Antarctica, in the Arctic seas, at
mid-latitudes and in the subtropics and the tropics. In the northern North Atlantic, where
mixing of arctic and subarctic waters and intense wintertime cooling produce dense waters
over the Greenland shelf, shelf water cascading was suggested to be at the origin of the
so-called East Greenland Spill Jet – a narrow bottom-intensified current confined to
the shelf break and the upper part of the East Greenland slope in the northwestern
Irminger Sea. However, the potential contribution of dense shelf water cascading
to intermediate and deep water formation in the region has not been documented
yet.
We present observational evidence that shelf water cascading in the northwestern
Irminger Sea is a prominent mechanism affecting the intermediate and deep water properties
in the Western Boundary Current. Using a comprehensive dataset consisting of 31
hydrographic sections carried out in the western Irminger Sea between the Denmark Strait
and Cape Farewell in 1997–2008, we found clear signatures of shelf water cascading down
the East Greenland slope to depths of more than 1000Â m. Summer observations at 66Ë N,
southwest of the Denmark Strait, revealed episodic presence of anomalously cold (θ  27.80 kg/m3, up to 27.89 kg/m3) shelf waters carried by the East Greenland
Current at depths of 250–400 m. Given the much lower densities of the surrounding slope
waters, the high density of the shelf waters makes them capable to cascade down the
continental slope. Clear hydrographic signatures of such cascading were found downstream,
at Faxafloi section (~64Ë N), where the cold fresh shelf waters reached the layer of the
Nordic overflow-derived deep waters (Ïă0Â >Â 27.80 kg/m3). An intense along-path
mixing with surrounding waters in the Western Boundary Current dilutes the cold
fresh waters descended from the shelf, so that farther downstream, nearby Cape
Farewell (59–60Ë N), traces of the upstream shelf water cascading are less clear,
but still distinguishable at the intermediate to deep levels. The likely mechanisms
behind the dense water formation at the East Greenland shelf, southwest of the
Denmark Strait, will be discussed, as well as the potential contribution of the shelf
water cascading to the intermediate and deep water export from the Irminger Sea. |
|
|
|
|
|
|