Water–air carbon fluxes in the coastal upwelling zone off northern Baja California

Abstract

M C INTRODUCTIONA topic of great concern and interest for climatologists and oceanographers is to determine how quickly natural and anthropogenic CO 2 is being absorbed by the oceans. The ocean acts as a large CO 2 sink (Takahashi et al. 2009), and a better understanding of the actual rate of ocean uptake of INTRODUCCIÓNUno de los temas más críticos y de gran interés para climatólogos y oceanólogos es conocer qué tan rápido está siendo absorbido el CO 2 natural y antropogénico por el océano. Dado que el océano es un gran sumidero de CO 2 (Takahashi et al. 2009) ABSTRACT. An important challenge in marine science is to quantify the air-sea flux of carbon because of its possible relation to climate change and the decreasing pH in seawater. In coastal areas of Mexico, the magnitude and variability of carbon fluxes between the ocean and the atmosphere is almost completely unknown. Therefore, the objective of this research was to determine the variability of air-sea carbon fluxes in the upwelling system off northern Baja California. A one-year time series of carbon fluxes was generated from data on partial pressure of carbon dioxide (pCO 2 ) from an oceanographic buoy installed immediately south of Punta Banda (Ensenada, Baja California), which measured salinity, temperature, and pCO 2 in the water (pCO 2water ) and air (pCO 2air ) every 3 h during 2009. The study area presented several upwelling events with low sea surface temperatures (≤14 ºC), salinity <34.0, and high values of pCO 2water , which resulted in an export of excess CO 2 in the water to the atmosphere, identifying the area as a temporary source of CO 2 . In contrast, during the relaxation of upwelling, low values of pCO 2water and intermediate surface temperatures resulted in the sea acting as a sink for CO 2 . The average daily flux was 0.6 ± 0.11 mmol C m ; thus, the system turned out to be a net source of CO 2 from the ocean to the atmosphere.Key words: ocean-atmosphere carbon fluxes, coastal zone, upwelling, North Pacific. RESUMEN.Cuantificar los flujos mar-atmósfera de carbono es un reto ambiental importante por su posible relación con el cambio climático y la disminución del pH del mar. En las zonas costeras de México se desconoce casi totalmente la magnitud y la variabilidad de los flujos de carbono entre el océano y la atmósfera. Por tal motivo, el objetivo de esta investigación fue conocer la variabilidad de los flujos de carbono en el sistema de surgencias frente a Baja California norte. Los flujos de carbono se estimaron de una serie de tiempo de la presión parcial de bióxido de carbono (pCO 2 ) generada a través de una boya oceanográfica instalada inmediatamente al sur de punta Banda, (Ensenada, Baja California), la cual medía salinidad, temperatura y pCO 2 en el agua (pCO 2agua ) y el aire (pCO 2aire ), cada 3 h durante 2009. La zona de estudio presentó varios eventos de surgencias, con temperaturas superficiales del mar bajas (≤14 ºC), salinidad <34.0 y valores altos de pCO 2agua , cuyo resultado fue una exportación del exceso de CO 2 en e...

Temporal variations of water pCO2 and the air–water CO2 flux at a coastal location in the southern California Current System: diurnal to interannual scales

“…This region features strong upwelling events with low SST (<14 ºC), relatively low salinity (<34.0), and high pCO 2W values (~700 atm), resulting in an export of excess CO 2 to the atmosphere. By contrast, Muñoz-Anderson et al (2015) reported that during the weak upwelling season, it is characterized by intermediate surface temperatures and low pCO 2W values (down to ~300 µatm), resulting in a CO 2 sink. These authors used a MAPCO 2 system to analyze the seasonal changes of pCO 2W and FCO 2 in one year (2009), without any reference to high frequencies (i.e., diurnal changes) or interannual changes.…”

“…Diferentes estudios han caracterizado las aguas costeras del Sistema de la Corriente de California usando distintas metodologías para definir su papel como fuente o sumidero de carbono (DeGrandpe et al 1998;Friederich et al 2002;Chávez et al 2007;De La Cruz-Orozco et al 2010;Pennington et al 2010;Evans et al 2011Evans et al , 2015Hales et al 2012;Fiechter et al 2014;Turi et al 2014;Muñoz-Anderson et al 2015;Mariano-Matías et al 2016). Sin embargo, hay incertidumbre en la dirección de FCO 2 en este sistema.…”

“…Moored Autonomous pCO 2 (MAPCO 2 ) systems have been deployed off the central and southern California coasts (Friederich et al 1995, Sutton et al 2014. Only one such system was deployed in the California Current System region off northern Baja California, and it provided data for only one year (Muñoz-Anderson et al 2015). The California Current exhibits particular dynamics in this area.…”

“…Se han utilizado sistemas independientes de pCO 2 (MAPCO 2 ) instalados frente a la costa central y sur de California (Friederich et al 1995, Sutton et al 2014. Sólo un sistema de este tipo fue instalado en el Sistema de la Corriente de California frente al norte de Baja California, y únicamente proporcionó datos de un año (Muñoz-Anderson et al 2015). La corriente de California exhibe una dinámica muy particular en esta zona.…”

“…En esta zona se presentan eventos de surgencias con TSM bajas (<14 ºC), salinidad relativamente baja (<34.0) y valores de pCO 2W altos autumn; the positive values indicate fluxes from water to air and vice versa. Muñoz-Anderson et al (2015) concluded that, according to the annual average, the buoy location off Ensenada was a source of CO 2 to the atmosphere. However, it is desirable to extend the time series to include interannual changes and thus have a better description of the effects of the various factors affecting pCO 2W variability.…”