AMEN (NATL4 + AGRIF) A tlantic M ode water E xperiment using N emo/Agrif

25-26 January 2007 Drakkar Meeting - Grenoble

AMEN AMEN (NATL4 + AGRIF)(NATL4 + AGRIF)

AAtlantictlantic M Modeode waterwater E Experimentxperiment using using NNemo/Agrifemo/Agrif

Virginie Thierry, Sébastien Theetten, Jean-Marc Molines, Anne-Marie Tréguier,

Carole GritDrakkar Team, Nemo team, Agrif Team


Scientific Objectives

Study mode water in the North-East Atlantic: formation, properties, subduction and variability

Identify formation area

Understand mechanisms that setup its properties

Determine the link between NAO index or other atmospheric indexes and mode water properties

Investigate the way mode water ventilates the ocean interior

Evaluate the ability of Drakkar model configurations to simulate correctly water masses and mode water in the eastern part of the North-Atlantic


AMEN model configuration

AMEN : refinement in NATL4 in the North-East Atlantic NATL4: Atlantic ocean, 20°S-80°N Agrif zoom : 30°W-0°E, 31°N-55°N


AMEN model configuration

• NATL4: ¼° resolution, eddy permitting, sea ice, closed boundaries, 486x529x64 grid points, time step: 2400S,

• Agrif zoom: 1/12°, eddy resolving, 383x397x64 grid points , time step: 720S,

• 64 grid points on the vertical:

– 36 levels within the first 1000 m, 6m at the surface, 50m at 500 m, 200 m at 5900 m

– Agreement with the NOC

• Bathymetry in Agrif zoom

– Identical to Mercator NATL12 bathymetry (for validation, exchanges purposes)


AGRIF validation

►SALINITY


AGRIF validation

Annual mean of EKE averaged along the western boundary

Low-resolution grid

High-resolution grid


AGRIF validation

Annual mean of EKE averaged along the southern and northern boundary

Low-resolution grid

High-resolution grid


Mode water in ORCA025-G70

18°W – 44°NJuly 2001

Identify by PV < 6 10-11 m-1 s-1

Example of profile containing mode water



Density of the mode water core

1991 2001



Potential temperature of the mode water core

1991 2001



T/S diagram in the POMME area

In the POMME area, central water are fresher in ORCA025 than in the data

ORCA 1993 / ORCA 2000 / POMMEORCA 1993 / ORCA 2000 / POMME



Time series of the mode water properties at 18°W-44°N

Over the period 1991-2001, the mode water is getting warmer, saltier, lighter

Consistent with the observed warming of the cental water in the Bay of Biscay over 1992-2003 (Gonzalez-Pola et al 2005)


Workplan2007• Finalize the configuration and run the simulation

– Resolve med water problem !• Validate the simulation with the large data set available in the area:

POMME, OVIDE, ARGO and historical data• Investigate mode water properties variability in using the model and

the data and mechanisms of this variability• Comparison with ORCA025-G70

2008• Use the Lagrangian tool Ariane to determine formation area,

ventilation area and ventilation processes• Comparison with NATL12• …


Questions

• What forcing field shall we use ?

• The target period is 1980-2006

– Large data set in the 80’s (see J. Paillet thesis)

– Woce data in the 90’s

– POMME: 2000-2001

– OVIDE: 2002, 2004, 2006


Thank you



Salinity of the mode water core

1991 2001



Potential vorticity of the mode water core

1991 2001



Thickness of the mode water layer

1991 2001

AMEN (NATL4 + AGRIF) A tlantic M ode water E xperiment using N emo/Agrif

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