Temporal and Spatial Variation of air-sea CO2 Fluxes in the West Coast of Baja California, Mexico

J. Martín Hernández-Ayón1,Ruben Lara-Lara2, Francisco Chavez3, Taro Takahashi4, Gilberto Gaxiola2.

1Instituto de Investigaciones Oceanológicas-UABC, Ensenada, B.C., Mexico; 2 CICESE-Ensenada, B.C., Mexico; 3Monterey Bay Aquarium Research Institute, 4Lamont-Doherty Earth Observatory.

IntroductionThe California Current System (CCS) extends along the coasts of California (USA) and Baja California (B.C.), and to a great extent controls the upwelling and oceanography of the region (Ibarra-Obando et al., 2001). Seasonal coastal upwelling and the biological activity which it instigates are responsible for most of the variability in the distribution of macro-nutrients (C, N, P) and dissolved gases (CO2 and O2) along the central California coast region (Pennington & Chavez, 2000), we believe that a similar situation can be occurring in most of B.C. But of course many work need to be done. Furthermore, Interannual variability is closely linked to changes in the mid-latitude atmospheric circulation associated with El Niño events or La Niña perturbing the normal seasonal cycle on these coast. In Mexico, a few information is available related with the CO2 system. This work present the first carbon dioxide study for the west coast of B.C.

Methods

Characteristic from Baja California Coast

Acknowledgments:We really appreciate to Dr. Taro Takahashi and Dr. Fco. Chavez for the helpful pCO2 data set that help us to learn more about the CO2 system in our Mexican Coast. Conacyt for the support to the project “ FLUCAR-IMECOCAL”.

A clear seasonal CO2 fluxes regimes has been identified in the zone of the Mexican Pacific coast off Baja California: Part of winter to spring season all the coastal water was a sink for atmospheric CO2 with a flux average during this period of -0.51 ±0.2 mol m2 year-1. However, the rest of the year it was a stronger source of CO2 to the atmosphere with a flux average of 1.52 ±0.74 mol m2 year-1. The mean annual flux for the Baja Coast was 0.97 ±1.1 mol m2 year-1 suggesting this zone as a source of CO2 to the atmosphere.

Spatial data show North-South CO2 flux variation in baja with the dominance of the low CO2 during early the year in the waters over the shelf area making the region a net sink during upwelling season. But all this area became in a strong source of CO2 after summer with higher fluxes south of Punta Eugenia (latitude 28o).

Upwelling was suppressed during the warm anomaly associated with El Niño in the West Coast of Baja (Durazo and Baumgartner et al. 2002) and the pCO2 (20oC) data presented an effect with lower values during the events.

In 2005 higher total CO2 concentrations was measured in west coast of B.C. as a result of more intense Upwelling. The pCO2 (SST) also had a different trend when is compared with the values measured from 1993-2001.

Conclusions

pCO2 and temperature in surface waters close to the coast from 1993-2001 were used from the data set from Dr. Taro Takahashi and Dr. Fco. Chavez. The pCO2 data have been obtained by a method using an infrared gas analyzer or gas-chromatograph for the determination of CO2 concentrations in a carrier gas equilibrated with seawater at a known temperature and total pressure. The precision of pCO2 measurements has been estimated to be about ± 0.7% on average. The quality controlled data are archived at www.ldeo.columbia.edu/res/pi/CO2. pCO2 data from 2005 were obtained during July from the IMECOCAL program survey also using a infrared gas analyzer. Seawater samples collected in the coast of Baja during upwelling in 2004 and 2005 for Total CO2 analysis were measured by coulometry.

From Espinosa-Carreon et al. 2004

Jul 98 Oct 98

Jan 97

Jan 98 Apr 98

Oct 97Jul 97

- 1 2 0 - 1 1 9 - 1 1 8 - 1 1 7 - 1 1 6 - 1 1 5 - 1 1 4 - 1 1 3 - 1 1 2 - 1 1 1 - 1 1 0 - 1 0 9

2 3

2 4

2 5

2 6

2 7

2 8

2 9

3 0

3 1

3 2

3 3

3 4

S u r f a c e W a t e r p C O 2 O b s e r v a t i o n s 1 9 9 3 - 2 0 0 1

- 1 2 0 - 1 1 9 - 1 1 8 - 1 1 7 - 1 1 6 - 1 1 5 - 1 1 4 - 1 1 3 - 1 1 2 - 1 1 1 - 1 1 0 - 1 0 9

2 3

2 4

2 5

2 6

2 7

2 8

2 9

3 0

3 1

3 2

3 3

3 4

S u r f a c e W a t e r p C O 2 O b s e r v a t i o n s 0 4 - 2 0 0 5

More total CO2 was measured in 2005 than 2004. But also more Chl-a was observed.

Observations during el Niño 1997-98

Spatial and Temporal Flux Variations

A delayed coastal upwelling were observed along the U.S. West Coast in 2005 but in Baja California upwelling were more intense.

Indice de Bakun From 30oL North

0.0

50.0

100.0

150.0

200.0

250.0

Up

well

ing

In

dex

37 YearAverage

30 DayRunning Mean

Month

0 2 4 6 8 10 12

CO

2 F

lux

(mol

m- 2

yea

r-1

)

-2

-1

0

1

2

3

4

West of Baja California Coast 1993-2001

Two clear features in Baja:1) Sink of CO2 before summer2) Source after summer

Southwest of B.C.was the biggest source of CO2

Northwest of B.C.was the biggest sink of CO2

In B:C the event was observed from Oct-January

From Durazo and Baumgartner et al. 2002

Chl

2004 2005