The pCO₂ variability in the midlatitude North Atlantic Ocean during a full annual cycle

Abstract

[1] The results of 1 year of automated pCO 2 measurements in 2002/2003 onboard the car carrier M/V Falstaff are presented and analyzed with regard to the driving forces that change the seawater pCO 2 in the midlatitude North Atlantic Ocean. The pCO 2 in surface seawater is controlled by thermodynamics, biology, air-sea gas exchange, and physical mixing. Here we estimate the effects on the annual cycle of pCO 2 and relate this property to parameters like SST, nitrate, and chlorophyll. On the basis of the amplitude in seawater pCO 2 for all 4°Â 5°grid boxes, this region can be separated into an eastern and western basin. The annual pCO 2 cycle in the eastern basin (10°W-35°W) is less variable, which can be related to the two counteracting effects of temperature and biology; air-sea gas exchange plays a minor role when using climatological MLD. In the western basin (36°W-70°W) the pCO 2 amplitude is more variable and strongly follows the thermodynamic forcing, since the biological forcing (as derived from nitrate concentrations) is decreased. Biology and air-sea exchange strongly depend on the MLD and therefore also include physical mixing effects. The pCO 2 data of the analyzed region between 34°N and 52°N compare well to the Takahashi et al. [2002] climatology except for regions north of 45°N during the wintertime where the bias is significant.

The subsurface layer reference to calculate preformed alkalinity and air–sea CO2 disequilibrium in the Atlantic Ocean

“…The seawater pCO 2 ( pCO 2 sw ) depends on thermodynamics, biological 7 activity, physical mixing and air-sea gas exchanges. While the thermodynamic relationship between pCO 2 sw and temperature is well known (Takahashi et al, 1981;Weiss et al, 1985) the effects of biological production and mixing are more difficult to resolve and explain (Lüger et al 2004 (Pond and Pickard, 1978;Marshall and Schott, 1999 (Pond and Pickard, 1978;Woods, 1985). Unluckily, the harsh meteorological conditions and the extension of ice covers in the high latitudes reduce the number of cruises that can be conducted there during the winter season.…”

“…Typical sea surface temperature (SST) oscillations can reach up to 10 ºC (Pond & Pickard, 1978) in temperate waters and up to 6 ºC in subpolar regions were WMF processes abound (Lab Sea Group, 1998). In the case of pCO 2 , the amplitude of variations ranges between 80 and 160 ppm that eventually translate into significant changes of surface C T (Bates et al, 1996;Lefévre et al, 2004;Lüger, 2004;Corbière et al, 2007). The seawater pCO 2 ( pCO 2 sw ) depends on thermodynamics, biological 7 activity, physical mixing and air-sea gas exchanges.…”

Changes in the partial pressure of carbon dioxide in the Mauritanian–Cap Vert upwelling region between 2005 and 2012

“…The variables involved in estimating FCO 2 data (i.e., f CO sw 2 , f CO atm 2 , SST, and SSS) were fitted to sinusoidal expressions (Lüger et al, 2004) for a given latitude as follows:…”

“…Automated instruments on volunteer observing ships (VOSs) serve to provide as many observations throughout the global ocean as possible. This is in addition to data collected on scientific cruises and at long-term moorings (i.e., Astor et al, 2005: Lüger et al, 2004Schuster et al, 2009;Ullman et al, 2009;Watson et al, 2009;Padin et al, 2010;Gruber et al, 2002;Dore et al, 2003;Santana-Casiano et al, 2007;Bates et al, 2014).…”

Ocean-Atmosphere Interactions of Gases and Particles

“…The pCO 2 in the subpolar NA is driven by high temperature variability (ΔSST~8 C) and high biological productivity. Here the biological productivity during spring and summer has a strong counteracting effect on the temperature driven pCO 2 increase during this period (Körtzinger et al 2008;Lüger et al 2004). Steinhoff et al (2010) have shown that the interannual variability of convective mixing of the surface layer may influence the wintertime budget of carbon and nutrients which directly impacts the observed seawater pCO 2 and thus the ΔpCO 2 .…”