Interannual variability of the upper ocean carbon cycle in the northeast Atlantic Ocean

Abstract

[1] Surface waters in the subtropical gyres have persistently absorbed anthropogenic CO 2 at a rate such that their inorganic carbon concentrations have shown a clear upward trend. We report a 10-year time series of upper-ocean inorganic carbon observations from the northeastern subtropical Atlantic at ESTOC which indicates significant variability in the inorganic carbon fluxes produced by variations in the Winter mixed-layer depths, induced by sea surface temperature anomalies. This variability reflects fluctuations relating to the NAO for both sites of the sub-tropical gyre, with the Eastern part showing a closer correlation with a 3-year NAO delay. The response to interannual variations in the meteorological forcing to the extra-tropical carbon cycle can be predicted to clarify effects on future climate change. Citation: González-Dávila, M.,

Variability of the ocean carbon cycle in response to the North Atlantic Oscillation

“…VARIABILITY OF THE OCEAN CARBON CYCLEet al, 2002;Gonzalez-Davila et al, 2007;Corbie`re et al, 2007;Schuster and Watson, 2007;Perez et al, 2008;Bates, 2012) provide evidence for a connection between NAO and ocean biogeochemistry in the North Atlantic. For the last decade, a decrease of the North Atlantic carbon sink has been reported (e.g.…”

Estimating mixed layer nitrate in the North Atlantic Ocean

“…Kamykowski and Zentara, 1986;Garside and Garside, 1995;Goes et al, 2000;Kamykowski et al, 2002;Switzer et al, 2003). But some of them are presenting algorithms only for other regions than the North Atlantic (Goes et al, 2000;Kamykowski and Zentara, 1986) or present gridded estimations on 10 • ×10 • grid (Switzer et al, 2003). The algorithm presented by Garside and Garside (1995) is based only on SST and they report a RMSE of 1.1 µmol L −1 for their North Atlantic dataset.…”

“…But estimating nutrient fluxes into the upper ocean and their subsequent utilisation by marine primary production is still a big challenge in oceanography. Even though there are continuous sampling programs at Bermuda Atlantic Time Series (BATS, Bates, 2007) station in the western North Atlantic and European Station for Time Series in the Ocean, Canary Islands (ESTOC, González-Dávila et al, 2007) in the eastern part of the subtropical North Atlantic, it is impossible to map nutrient variability for the whole basin. The mechanism of nutrient supply is very different at the two stations: at BATS it is mainly driven by eddies and at ESTOC by winter convection (Cianca et al, 2007).…”

“…In the temperate North Atlantic, between 30 • N and 60 • N, the coverage of surface nutrient data is sparse especially because of very few wintertime observations. Körtzinger et al (2008) and Hartman et al (2010) Some work has been done to estimate winter nitrate concentrations from nitrate-density relationships (Garside and Garside, 1995), nitrate-temperature/density relationships (Kamykowski and Zentara, 1986;Sherlock et al, 2007) or to estimate nutrient fields from remotely sensed data (Goes et al, 2000;Kamykowski et al, 2002;Switzer et al, 2003). Several other attempts were made to estimate wintertime nitrate concentration (e.g.…”

“…Several other attempts were made to estimate wintertime nitrate concentration (e.g. Takahashi et al, 1985;Glover and Brewer, 1988;Körtzinger et al, 2001;Koeve, 2001) as the values at the onset of the productive season are crucial to assess new production (Minas and Codespoti, 1993).…”