EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Mechanisms driving seawater pCO2 spatiotemporal variability in the Canary-Iberian Upwelling System

Daniel Broullón1, Rita Nolasco2, Rosa Reboreda1, Jesus Dubert2, Marion Gehlen3, James Orr3, and Fiz F. Pérez1
Daniel Broullón et al.
  • 1Instituto de Investigaciones Marinas (IIM), Consejo Superior de Investigaciones Científicas (CSIC), Vigo, Spain
  • 2CESAM & Department of Physics, Universidade de Aveiro, Aveiro, Portugal
  • 3Laboratoire des Sciences du Climat et de l'Environnement (LSCE/IPSL), Université Paris-Saclay, Gif-sur-Yvette, France

Upwelling systems are very productive regions of the ocean that strongly contribute to the local economies holding very different fisheries. These dynamic systems are characterized by a high degree of spatial and temporal variability of biogeochemical properties, including carbon, which is generally poorly represented in coarse-resolution global models. The importance of the marine carbon system characterizing these systems has been demonstrated in different regions from multiple perspectives. For the first time, we evaluate the drivers of the spatiotemporal variability of the seawater partial pressure of CO2 (pCO2) in the Canary-Iberian Upwelling System (25.5-45ºN, 5.5-20.5ºW) to better understand the inorganic carbon cycle in this highly-productive upwelling region. To do so, we first coupled a regional high-resolution ocean circulation model CROCO with the ocean biogeochemical model PISCES and run a climatological simulation. A first-order Taylor expansion was applied over this simulation to compute the contribution of four variables to the pCO2 spatiotemporal variability: salinity-normalized dissolved inorganic carbon (sCT), salinity-normalized total alkalinity (sAT), temperature (T) and freshwater fluxes (FW). Modeled pCO2 is in agreement with that of recent data-based monthly climatologies (open ocean RMSE: 5.2-10.8 µatm; coastal ocean RMSE: 7.9-18.7 µatm), measured data from the Surface Ocean CO₂ Atlas (SOCAT) (RMSE: 6.6-13.9 µatm) and computed pCO2 from measured AT and pH at the European Station for Time series in the Ocean Canary islands (ESTOC) (RMSE: 5.1 µatm). The spatial distribution of the pCO2 anomalies relative to the domain mean shows two different areas with opposite anomalies: positive anomalies around the coast in the entire domain and in open ocean south of 33ºN and negative anomalies in open ocean north of 33ºN. This pattern is mainly driven by the contribution of the T component and a minor influence of sAT and FW, with the sCT component largely counteracting the effects of the other drivers but contributing to the positive anomaly along the Iberian coast. The seasonal variability is controlled by T and sCT, with a minor influence of sAT and a negligible importance of FW. The seasonal cycle shows a direct covariation between the T contribution and the δpCO2 (monthly mean minus annual mean of pCO2) and an inverse covariation between the sCT contribution and the δpCO2 that counteracts the effect of T in the δpCO2 amplitude. A decrease in the δpCO2 amplitude was found from open ocean (depths > 200m) to coastal ocean (depths < 200m) determined mainly by a decrease in the influence of the T driver and, less significant, also by a reduction of the sCT contribution. The general agreement between modeled and observed contributions to pCO2 variability at the ESTOC time-series station, in terms of both phase and amplitude, lends credibility to our deconvolution and model, which has been applied across the Canary-Iberian Upwelling System, to assess the processes behind the spatiotemporal variability of pCO2.

How to cite: Broullón, D., Nolasco, R., Reboreda, R., Dubert, J., Gehlen, M., Orr, J., and Pérez, F. F.: Mechanisms driving seawater pCO2 spatiotemporal variability in the Canary-Iberian Upwelling System, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18139,, 2020

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