scholarly journals Interannual variability of the oceanic CO2sink in the subtropical gyre of the North Atlantic Ocean over the last 2 decades

2007 ◽  
Vol 112 (C9) ◽  
Author(s):  
Nicholas R. Bates
Keyword(s):  
Atlantic Ocean ◽  
Interannual Variability ◽  
North Atlantic ◽  
North Atlantic Ocean ◽  
Subtropical Gyre ◽  
The North ◽  
The North Atlantic

scholarly journals Importance of dissolved organic nitrogen in the North Atlantic Ocean in sustaining primary production: a 3-D modelling approach

2008 ◽  
Vol 5 (2) ◽  
pp. 1727-1764 ◽  
Author(s):  
G. Charria ◽  
I. Dadou ◽  
J. Llido ◽  
M. Drévillon ◽  
V. Garçon
Keyword(s):  
Atlantic Ocean ◽  
Primary Production ◽  
North Atlantic ◽  
Dissolved Organic Nitrogen ◽  
Organic Nitrogen ◽  
North Atlantic Ocean ◽  
Subtropical Gyre ◽  
Ekman Transport ◽  
The North ◽  
The North Atlantic

Abstract. An eddy-permitting coupled ecosystem-circulation model including dissolved organic matter is used to estimate the dissolved organic nitrogen (DON) supply sustaining primary production in the subtropical North Atlantic Ocean. After an analysis of the coupled model performances compared to the data, a sensitivity study demonstrates the strong impact of parameter values linked to the hydrolysis of particulate organic nitrogen and remineralisation of dissolved organic nitrogen on surface biogeochemical concentrations. The physical transport of dissolved organic nitrogen contributes to maintain the level of primary production in this subtropical gyre. It is dominated by the meridional component. We estimate a meridional net input of 0.039 molN.m−2.yr−1 over the domain (13°–35° N and 71–40° W) in the subtropical gyre. This supply is driven by the Ekman transport in the southern part and by non-Ekman transport (meridional current components, eddies, meanders and fronts) in the northern part of the subtropical gyre. At 12° N, our estimate (18 kmolN.s-1) confirms the estimation (17.9 kmolN.s-1) made by Roussenov et al. (2006) using a simplified biogeochemical model in a large scale model. This DON meridional input is within the range (from 0.05 up to 0.24 molN.m−2.yr-1) (McGillicuddy and Robinson, 1997; Oschlies, 2002) of all other possible mechanisms (mesoscale activity, nitrogen fixation, atmospheric deposition) fuelling primary production in the subtropical gyre. The present study confirms that the lateral supply of dissolved organic nitrogen might be important in closing the N budget over the North Atlantic Ocean and quantifies the importance of meridional input of dissolved organic nitrogen.

scholarly journals Importance of dissolved organic nitrogen in the north Atlantic Ocean in sustaining primary production: a 3-D modelling approach

2008 ◽  
Vol 5 (5) ◽  
pp. 1437-1455 ◽  
Author(s):  
G. Charria ◽  
I. Dadou ◽  
J. Llido ◽  
M. Drévillon ◽  
V. Garçon
Keyword(s):  
Atlantic Ocean ◽  
Primary Production ◽  
North Atlantic ◽  
Dissolved Organic Nitrogen ◽  
Organic Nitrogen ◽  
North Atlantic Ocean ◽  
Subtropical Gyre ◽  
Ekman Transport ◽  
The North ◽  
The North Atlantic

Abstract. An eddy-permitting coupled ecosystem-circulation model including dissolved organic matter is used to estimate the dissolved organic nitrogen (DON) supply sustaining primary production in the subtropical north Atlantic Ocean. After an analysis of the coupled model performances compared to the data, a sensitivity study demonstrates the strong impact of parameter values linked to the hydrolysis of particulate organic nitrogen and remineralisation of dissolved organic nitrogen on surface biogeochemical concentrations. The physical transport of dissolved organic nitrogen contributes to maintain the level of primary production in this subtropical gyre. It is dominated by the meridional component. We estimate a meridional net input of 0.039 molN m−2 yr−1 over the domain (13–35° N and 71–40° W) in the subtropical gyre. This supply is driven by the Ekman transport in the southern part and by non-Ekman transport (meridional current components, eddies, meanders and fronts) in the northern part of the subtropical gyre. At 12° N, our estimate (18 kmolN s−1) confirms the estimation (17.9 kmolN s−1) made by Roussenov et al. (2006) using a simplified biogeochemical model in a large scale model. This DON meridional input is within the range (from 0.05 up to 0.24 molN m−2 yr−1) (McGillicuddy and Robinson, 1997; Oschlies, 2002) of all other possible mechanisms (mesoscale activity, nitrogen fixation, atmospheric deposition) fuelling primary production in the subtropical gyre. The present study confirms that the lateral supply of dissolved organic nitrogen might be important in closing the N budget over the north Atlantic Ocean and quantifies the importance of meridional input of dissolved organic nitrogen.

Mechanisms of Interannual Variations of the Meridional Overturning Circulation of the North Atlantic Ocean

2008 ◽  
Vol 38 (2) ◽  
pp. 467-480 ◽  
Author(s):  
Cécile Cabanes ◽  
Tong Lee ◽  
Lee-Lueng Fu
Keyword(s):  
Shear Flow ◽  
Atlantic Ocean ◽  
Interannual Variability ◽  
North Atlantic ◽  
North Atlantic Ocean ◽  
Meridional Overturning Circulation ◽  
Vertical Shear ◽  
The North ◽  
Meridional Overturning ◽  
The North Atlantic

Abstract The authors investigate the nature of the interannual variability of the meridional overturning circulation (MOC) of the North Atlantic Ocean using an Estimating the Circulation and Climate of the Ocean (ECCO) assimilation product for the period of 1993–2003. The time series of the first empirical orthogonal function of the MOC is found to be correlated with the North Atlantic Oscillation (NAO) index, while the associated circulation anomalies correspond to cells extending over the full ocean depth. Model sensitivity experiments suggest that the wind is responsible for most of this interannual variability, at least south of 40°N. A dynamical decomposition of the meridional streamfunction allows a further look into the mechanisms. In particular, the contributions associated with 1) the Ekman flow and its depth-independent compensation, 2) the vertical shear flow, and 3) the barotropic gyre flowing over zonally varying topography are examined. Ekman processes are found to dominate the shorter time scales (1.5–3 yr), while for longer time scales (3–10 yr) the MOC variations associated with vertical shear flow are of greater importance. The latter is primarily caused by heaving of the pycnocline in the western subtropics associated with the stronger wind forcing. Finally, how these changes in the MOC affect the meridional heat transport (MHT) is examined. It is found that overall, Ekman processes explain a larger part of interannual variability (3–10 yr) for MHT (57%) than for the MOC (33%).

Sign in / Sign up

Export Citation Format

Share Document