CAIBEX workshop Mesoscale experiments and modelling Cape Ghir

CAIBEX workshop Mesoscale experiments and modelling Cape Ghir C. Troupin 1, P. Sangrà 2, J. Arístegui 2 1 GHER-MARE, AGO Department, University of Liège, Belgium 2 Facultad de Ciencias del Mar, Universidad de Las Palmas de Gran Canaria, Spain 29 November 1 December 21

CAIBEX workshop Mesoscale experiments and modelling Cape Ghir C. Troupin 1, P. Sangrà 2, J. Arístegui 2 1 GHER-MARE, AGO Department, University of Liège, Belgium 2 Facultad de Ciencias del Mar, Universidad de Las Palmas de Gran Canaria, Spain 29 November 1 December 21

Data locations year = 4, month = 9, day = 12 T ( C) 23 12 o W 11 o W 1 o W 9 o W 32 o N 22.5 31 o N 22 21.5 21 2.5 31 o N CTD HPS Bongo Incubation Monitoring Transect 2 19.5 19 12 o W 11 o W 1 o W 4 3 2 1 1 2 3 Sampling strategy model results 9 SeaSoar tracks, 56 CTDs, 6 drifters High spatial resolution

T S diagram North Atlantic Central Water: 1 C T 16 C Antarctic Intermediate Water: salinity minimum (7 1 m) Mediterranean Water: T > 9 C and S > 35.5 North Atlantic Deep Water: T 3 C, S 35

Horizontal mapping 32 o N 25 m T ( C) 4 21 overall picture of the filament 2 2 31 o N 19 Variables: T, S, [O 2], Fluorescence 4 2 18 17 Depths: from 5 to 3 m 12 o W 32 o N 4 2 31 o N 4 2 11 o W 1 o W 9 o W 3 m T ( C) 14.2 14 13.8 13.6 13.4 Near-surface: upwelling and filament T min 16.5 C T max 21.5 C 2-3 m: warm core close to coast T max 14.25 C subsurface anticyclonic eddy? 12 o W 11 o W 1 o W 9 o W

Drifters Locations SeaSoar measurements Date: September 3, 29 31 o N filament core 5 1 m-drogue drifters 29 o N = Start 95854 95855 95861 95862 95864 95867 anticyclonic eddy 1 3 m-drogue drifter median velocity: O(.35 m/s) 3 m-drogue drifter: T 5 6 d, R 3 4 km 28 o N 14 o W 13 o W 12 o W 11 o W 1 o W

SeaSoar tracks 4 2 2 4 6 7 August 17-2 (tracks no. 1 6): synoptic picture of the filament 31 o N 4 8 August 22-23 (track no. 7): variation of the filament position 2 1 3 5 9 September 2-3 (tracks no. 8 and 9): drifter locations + final picture of the filament 12 o W 11 o W 1 o W Issues: 1. Fluorescence calibration (tracks 1 7) 2. Rough sea conditions no measurements near surface (tracks 7 9)

SeaSoar measurements Left: fluorescence before and after calibration Right: temperature

SeaSoar interpolated temperature Track 6 T ( C) 21 2 1 19 18 2 17 16 3 4 1 2 15 14 13 12 3.4 3.6 3.8 31 31.2 31.4 Latitude ( N) Track 7 T ( C) 22 21 2 19 18 17 16 Tracks 1 3: descent of isotherms possible surface anticyclonic eddy Tracks 4 7: filament more visible descent of isotherms at 2 4 m Tracks 8 9: descent of the isotherms few near-surface data 3 15 14 13 4 3.4 3.6 3.8 31 31.2 Latitude ( N) 12

SeaSoar interpolated salinity and fluorescence Track 8 S 1 2 3 36.6 36.4 36.2 36 35.8 Fluorescence: lack of surface data maximal concentration: 5 m Salinity: filament signal less evident subsurface anticyclonic eddy 35.6 4 3.3 3.4 3.5 3.6 3.7 3.8 3.9 Latitude ( N) Track 8 Fluorescence <=.5 Fluorescence <=.5 Track 9 S 36.5 25.4 25.4 36.4 1 2 36.3 36.2 36.1 36 5 75.3.2.1 5 75.3.2.1 35.9 3 35.8 35.7 1 3.3 3.4 3.5 3.6 3.7 3.8 3.9 Latitude ( N) 1 3 3.2 3.4 3.6 3.8 Latitude ( N) 4 3 3.2 3.4 3.6 3.8 Latitude ( N)

CTD meridional transect T ( C) S Fluorescence T13 T12 T11 T1 T9 T8 T7 T6 T5 T4 T3 T2 T1 2 T13 T12 T11 T1 T9 T8 T7 T6 T5 T4 T3 T2 T1 37.4 T13 T12 T11 T1 T9 T8 T7 T6 T5 T4 T3 T2 T1.45 19 37.2.4 1 2 18 17 16 1 2 37 36.8 36.6 36.4 25 5.35.3.25.2 15 36.2.15 3 14 3 36 75.1 13 35.8.5 4 3.2 3.4 3.6 3.8 31 31.2 Latitude ( N) 4 3.2 3.4 3.6 3.8 31 31.2 Latitude ( N) 1 3.2 3.4 3.6 3.8 31 31.2 Latitude ( N) Light Trans. (%) 9 Longitude: 1 36 W; Date: 25-27 August Filament between T9 and T1 Chlorophyll maximum: 25 m, below filament Very low light transmission T13 T12 T11 T1 T9 T8 T7 T6 T5 T4 T3 T2 T1 5 15 3.2 3.4 3.6 3.8 31 31.2 Latitude ( N) 8 7 6 5 4 3

Summary checklist Data pre-processing Prelimary analysis: property diagrams, mean profiles Horizontal property maps Vertical interpolation + interpretation Drifter analysis Current-meter processing Thermosalinograph data?

Process study 48 o N 4 o N 32 o N 24 o N 16 o N D 28 Grid D3 D2 D1 3 2 1 1 2 3 4 5 D i D i+1: One-way, off-line nesting D : high-resolution climatology [Troupin et al. (21) JGR] D 1: solution from E. Mason Domain Res. (km) Size D 1 15. 227 33 D 2 5.1 258 29 D 3 1.7 162 162 45 o W 36 o W 27 o W 18 o W 9 o W o

Process-oriented experiments β-effect Wind intensity and wind curl Topographic effects Friction q (m 1 s 1 ) 42 o N 1 9.5 39 o N 9 8.5 36 o N 8 q (m 1 s 1 ) 1 33 o N 7.5 7 42 o N 9 6.5 36 o N 8 7 6 27 o N (b) Summer 24 o W 2 o W 16 o W 12 o W 8 o W Mecanism: 6 5.5 5 24 o N 5 1. Conversation of potential vorticity 18 o N (a) Summer 4 2. Injection of relative vorticity by the wind 3 o W 24 o W 18 o W 12 o W 6 o W

Realistic solution Validation against Medspiration satellite images (left) Correct scales and location of the filament (right) Agreement with in situ data year = 4, month = 9, day = 12 ( C) 24 23.5 23 22.5 31 o N 22 21.5 21 2.5 2 12 o W 11 o W 1 o W (a) 19.5 19

Sub-surface anticyclonic eddy year = 4, month = 9, day = 3 T ( C) 16 year = 4, month = 9, day = 3 ζ.25 15.8.2 15.6.15 15.4.1 31 o N 15.2 31 o N.5 15 14.8.5 14.6.1 14.4.15 14.2.2 12 o W 11 o W 1 o W 14 12 o W 11 o W 1 o W.25 Model agrees with CAIBEX observations Mechanism: interaction undercurrent + topography Similar in California Upwelling System

Sub-mesoscale study 29 Grid D 3 5 o N 2 1 4 o N D2 1 D3 2 2 o N 3 4 1 o N D1 5 45 o W 36 o W 27 o W 18 o W 9 o W o D i D i+1: One-way, off-line nesting [Mason et al. (21) Ocean Model.] D : high-resolution climatology [Troupin et al. (21) JGR] D 1: solution from E. Mason et al. (subm.) Domain Res. (km) Size D 1 7.5 442 646 D 2 2.5 242 29 D 3.8 29 29

Sub-mesoscale fields Temperature and normalized vorticity at 1 m 8-m horizontal resolution Broader filament; Frontal instabilities Animation: http://www.youtube.com/watch?v=-aadsmnjrio

Mapping Repeat sections (filament) Circulation modeling Publications and conferences EOF analysis Source: Medspiration project (ESA) Sensor: AATSR (1 km-resolution) Period: 29 ongoing Method: DINEOF [Alvera-Azcárate et al. (25, 29)] Objectives: 1. Extract dominant modes 2. Fill incomplete images http://gher-diva.phys.ulg.ac. be/dineof/dineof_allcan.html

EOF analysis: dominant mode Spatial modes: Temporal modes: EOF no. 1: seasonal cycle EOF no. 2: related to filament related to wind curl?

Summary checklist Realistic model results + validation Process-oriented experiments Generation mechanism Sub-mesoscale modeling effort EOF analysis Inter-annual forcing Publication

Publications 1. Generation of the Cape Ghir coastal upwelling filament: a numerical study [modelling] 2. High-resolution sampling of the Cape Ghir upwelling filament during the CAIBEX cruise [observations] 3. Observation and modeling of a subsurface anticyclonic eddy off Cape Ghir (NW Africa) [modelling + observation]

Conferences VLIZ Young Scientists day, Oostende (Belgium), November 27, 29: High-resolution measurements and modelling of the Cape Ghir upwelling filament during the CAIBEX cruise [oral presentation and poster] Ocean Science Meeting, Portland (USA), February 22-26, 21: Poleward front of upwelling filaments generates subsurface anticyclonic eddies (feddy): a CAIBEX project contribution [poster], P Sangrà, J. Arístegui, C. Troupin and E. D. Barton. The Cape Ghir (NW Africa) upwelling filament: Modeling and observation during the CAIBEX Campaign [poster], C Troupin, P Sangrà, J. Arístegui, J.-M. Beckers and E. D. Barton. 42 nd International Liège Colloquium on Ocean Dynamics: Liège (Belgium), April 26-3 21: High-resolution measurements of an upwelling filament during the CAIBEX campaign [oral presentation and poster], C. Troupin, J. Arístegui, J.-M. Beckers and P. Sangrà.