Upper ocean carbon fluxes in the Atlantic Ocean: The importance of the POC:PIC ratio

The mean depth distribution of the POC:PIC ratio of sinking particles, measured with particle interceptor traps deployed in the Atlantic Ocean, is fitted by an exponential function (POC:PIC = 64.3Z−0.56; r2 = 0.69) The function is successfully evaluated by comparison with (a) estimates of the POC:PIC ratio of export production, computed from seasonal changes of nitrate and alkalinity and (b) estimates of the POC:PIC ratio of remineralization on shallow isopycnals. The basin mean POC:PIC ratio of export production is 4.2–4.37. The POC:PIC-depth function is combined with empirical relationships between the flux of particulate organic matter, primary production and depth, satellite derived primary production data sets, and the regional distribution of ψ (the ratio of released CO2:precipitated carbonate during CaCO3 formation) in order to estimate the effective carbon flux (Jeff) in the Atlantic Ocean. Remineralization of organic carbon above the winter mixed layer (11–17%) and CaCO3 sequestration from the winter mixed layer (13–16%), which is the balance between CaCO3 production and shallow dissolution, are the two main processes which control the difference between export production (0.9 and 2.9 GT C yr−1) and Jeff (0.64 and 2.2 GT C yr−1) on the basin scale (65°N to 65°S). CaCO3 sequestration is the dominant process modulating effective carbon export in the tropics, while shallow POC remineralization dominates in temperate and polar waters. Observed regional patterns like polarward increases of the POC:PIC export ratio and of ψ counteract each other largely when Jeff is computed

Mariculture of the Asian kelp Undaria pinnatifida and the native kelp Saccharina lattisima along the Atlantic coast of southern Europe: An overview

Preprin

Sensitivity of biogenic carbon export to ocean climate in the Labrador Sea, a deep-water formation region

We used a physical-biogeochemical model to examine the sensitivity of biogenic carbon export to ocean climate in the Labrador Sea, a subpolar, deep-water formation region. Documented changes in winter mixed layer depth between the late 1960s and the mid-1990s were used to construct scenarios of weak, moderate, and strong winter convection that drive the biogeochemical model. The model simulations suggest that the total biogenic carbon export (particle sinking flux + DOC export) is higher under strong winter convection (e.g., during the early 1990s) than under weak winter convection (e.g., during the late 1960s), by ∼70% across the 200-m isobath and nearly double at 500 m and 1000 m depth. These large variations in total biogenic carbon export are essentially due to the response of DOC export to ocean climate conditions. Sensitivity analyses indicate that the variations in DOC export from the euphotic zone are due to the impact of the convection regime on the development of the microbial food web and on the bacterial consumption of DOC in surface waters. Although DOC downward fluxes within the mesopelagic zone (below ∼500 m) are largely controlled by physical processes, the effect of convection on microbial dynamics can potentially amplify the year-to-year variations in the transport of DOC to the deep ocean due to convection