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| Titel |
Water mass transformation in the North Atlantic over 1985-2002 simulated in an eddy-permitting model |
| VerfasserIn |
R. Marsh, S. A. Josey, A. J. G. Nurser, B. A. Cuevas, A. C. Coward |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1812-0784
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| Digitales Dokument |
URL |
| Erschienen |
In: Ocean Science ; 1, no. 2 ; Nr. 1, no. 2 (2005-10-25), S.127-144 |
| Datensatznummer |
250000159
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| Publikation (Nr.) |
 copernicus.org/os-1-127-2005.pdf |
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| Zusammenfassung |
| Water mass transformation in the North Atlantic is examined in an
eddy-permitting simulation with the OCCAM ocean general circulation model,
forced by realistic surface fluxes over the period 1985-2002. Three Atlantic regions
are considered - the subtropics, mid-latitudes, the northeast Atlantic - along with
the Labrador Sea. The oceanic boundaries of each region coincide with hydrographic
sections occupied in recent years. These regions broadly represent the
formation sites of Eighteen Degree Water (EDW), Subtropical Mode Water (STMW),
Subpolar Mode Water (SPMW) and Labrador Sea Water (LSW).
Water mass budgets are obtained for each region and year. Terms in
the budget comprise surface-forced transformation rates, boundary exchanges
and unsteadiness. Transformation rates due to "total mixing" are obtained as the difference
between net and surface transformation rates. Transports at the boundaries are evaluated alongside
recent hydrographic section datasets, while surface-driven and mixing-driven transformation rates are
compared with estimates based on air-sea flux datasets and inverse analysis of hydrographic data.
In general OCCAM compares well with the observations, although two particular discrepancies are identified:
deep overflows at high latitudes too light by around 0.2 kg m-3 and spurious heat gain of
up to 100 Wm-2 east of the Grand Banks. Over 1985-2002, there is considerable
variability on a range of timescales, in the annual surface-driven and mixing-driven formation rates
of all four water masses.
In the case of EDW and STMW, surface-driven and mixing-driven formation rates largely cancel.
This is not so for SPMW and LSW, leading to regional net formation rates of up to 17 Sv and 15 Sv, respectively.
In particular, OCCAM successfully simulates the strong LSW formation event of 1989-1994. |
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