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| Titel |
The Deep Western Boundary Current southeast of Cape Farewell, Greenland: decadal transport variability from repeat hydrography and satellite altimetry |
| VerfasserIn |
Artem Sarafanov, Anastasia Falina, Herlé Mercier, Pascale Lherminier, Alexey Sokov, Claire Gourcuff |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250032515
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| Zusammenfassung |
| Recent decadal changes in the Deep Western Boundary Current (DWBC) transport southeast
of Cape Farewell are assessed from hydrographic data (1991–2007), individual direct velocity
measurements (2002–2006) and altimetry (1992–2007).
Following the approach used in earlier studies, we first determined that the DWBC
(Ï0 >27.80) baroclinic transport (TBC) referenced to 1000 m depth increased by ~2Â Sv
between the mid-1990s (1994–1997) and 2000s (2000–2007). In the next step, we quantified
velocity changes at the reference level (1000 m) by combining estimates of the
hydrography-derived velocity changes in the water column and the altimetry-derived velocity
changes at the sea surface. The inferred increase in the southward velocity at 1000Â m above
the DWBC in 1994–2007 indicates that the increase in the DWBC absolute transport was
larger than the 2-Sv increase in the DWBC TBC. This result and the observed coherence of
the DWBC absolute and baroclinic transport changes between individual observations imply
that the DWBC absolute transport variability in the region is underestimated but
qualitatively well represented by its baroclinic component on decadal and shorter time
scales.
The updated historical record of the DWBC TBC (1955–2007) shows distinct decadal
variability (±2–2.5Â Sv) with the transport minima in the 1950s and mid-1990s,
maximum in the early 1980s and moderate-to-high transport in the 2000s. The DWBC
TBC decadal variability is consistent with the general pattern of the recent decadal
hydrographic and circulation changes in the northern North Atlantic. The DWBC TBC
anomalies negatively correlate (RÂ =Â –0.80, 1955–2007) with thickness anomalies of the
Labrador Sea Water (LSW) at its origin implying a close association between the
DWBC transport southeast of Cape Farewell and the LSW production in the Labrador
Sea. During the recent three decades (late 1970s – late 2000s), the DWBC TBC
changes were also in-phase with changes in the strength and zonal extension of the
Subpolar Gyre (SPG). In particular, the SPG weakening at shallow levels in the
mid-1990s – mid-2000s was accompanied by the DWBC strengthening in the Irminger
Sea.
The results imply that the decadal changes in the (i) LSW production, (ii) SPG
strength and (iii) DWBC transport in the Irminger Sea are linked, representing a
complex coherent oceanic response to the decadal variability of the surface forcing. |
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