1. Surface drifters in the southern Gulf of. California. (June 2004-2006)
Surface drifters in the southern Gulf of California (June ) Miguel F. Lavín1 and P. P. Niiler ) CICESE, Ensenada, Mexico 2) SIO, La Jolla, USA
Colaborators: A. Amador, E. Beier (CICESE), R. Castro (UABC)

2. Southern G.C. Surface Circulation
Seasonal (Pacific, wind, buoyancy, mixing)
Eddies (geostrophic, topographic?)
Coastal Trapped Waves (Ecuatorial, Storm-generated)
Jets (costal, eddy-edge, frontal instabilities)
Short-period events (met-driven)

3. Mostly from hydrography and heat and salt balances.
HOW WE KNOW ABOUT IT?
Mostly from hydrography and heat and salt balances.
Geostrophy from single-section “constructed” seasonal cycles.
Numerical models (3D baroclinic).
Mesoscale from satellite images (SST and color).
Almost no instrumented current observations!
Except: Moorings by Winant & Merrifield in Guaymas basin,
acoustic dropsondes by Collins et al., in the mouth.

4. AVHRR
SeaWiFS
MESOSCALE
50 cm/s?
/Eddies
Navarro et al. (2004)

5. TRAPPED WAVES
NLOM (Zamudio et al., 2002)

6. MODE 1
Vg Heat flux
MEAN Vg
2005

7. 3D HAMSON baroclinic model
(2003)
MODE
Top 10 m
3D HAMSON baroclinic model

8. Anticyclonic in Winter Cyclonic in Summer
What numerical models use to show they work:
Anticyclonic in Winter
Cyclonic in Summer
(Lavín et al., 1997)

10. 5-21 June 2004 (16 drifters) 6-21 Aug. 2004 (16 drifters)
120+ DRIFTERS WERE LAUNCHED
SeMar February & July 2005 (4 each)
CICIMAR August 2005, June 2006 (4 each)
Ferrys, once a month, June 2004-June 2005
NAME
5-21 June 2004 (16 drifters)
6-21 Aug (16 drifters)
1 drifter once a month, June 2004-July 2005
PROCOMEX (4 each)
June 2005
November 2005
August 2006

11. Jun 2004-Oct 2006

14. All June 2004

15. Q2 Junio 2004 June 15-30, 2004 MODIS 4km x 4km Vg 1500 m
AVHRR 1.1x1.1 km
June 15-30, 2004
MODIS 4km x 4km

16. JUNE 2004
JUNE 2005

17. JUNE 2004
JUNE 2006
JUNE 2006
JUNE 2004
(no scale, raw, not cleaned)

18. July 2004
July 2005
Cyclonic
Anticyclonic
Cyclonic
Cyclonic

19. AUGUST 2004
AUGUST 2005
Cyclonic
Cyclonic
Cyclonic
Cyclonic
Cyclonic
Cyclonic
Anticyclonic

20. Origin of the coastal current?
Costa Rica Coastal Current/WMC
Wind change

21. Wyrtki 1965 May 2001 June 2005 May 2002 June 2003 CC?
Giro anticiclónico
June 2003
June 2005
CC?

22. (2002)

24. SUMMARY
1.- In June-July there is a poleward current along the Mexican mainland
with speeds up to ~80 cm/s.
2.- In average, its speed is ~60 cm/s: it takes 3 weeks for drifters to travel
from the inner entrance to the northern Gulf.
3.- This speed is twice the speed of advance of climatological AVHRR
isotherms (~30 cm/s).
4.- The drifters suggest that the current lasts 2-3 weeks.
5.- The circulation pattern changes by August:
gulf-wide eddies dominate the circulation.
July: Guaymas basin, Anticyclonic eddy, s~50 cm/s, period ~5 days.
August: SPMtr & Guaymas basin, Cyclonic eddy, : s~25 cm/s, period ~3 days
July-October: LaPaz-Topo, Cyclonic eddy : s~30 cm/s, period ~3-4 days