Seasonal variation in total organic carbon in the northeast Atlantic in 2000–2001

Abstract

[1] Total organic carbon (TOC) was measured in the midlatitudes of the northeast Atlantic in 2000-2001 during the Programme Océan Multidisciplinaire Méso Echelle (POMME). In spring, mixed layer depth (MLD) was positively correlated with the north latitude, while the surface TOC and chlorophyll-a (Chl a) were negatively correlated with it. It indicates the northward propagation of TOC accumulation along the onset of spring bloom, which was triggered by shoaling of MLD from the south. Surface TOC was highest in summer, though surface Chl a was lowest. Surface TOC was significantly correlated with surface Chl a during winter and spring but not during summer or fall, indicating the minor influence of total phytoplankton biomass on surface TOC distribution in the oligotrophic season. High surface TOC in summer and fall was related with shallow MLD, which could hold fresh TOC near the surface. Downward TOC flux from the surface to below the seasonal thermocline was estimated for the processes of winter convection (F c ), turbulent diffusion (F d ) and sinking flux (F p ). The sum of these fluxes accounts for 6-75% of annual new production. To our knowledge, this is the first estimation based on the simultaneous measurement of F c , F d , F p , and annual new production.

Impact of marine biogeochemistry on the chemical mixing state and cloud forming ability of nascent sea spray aerosol

“…SSA hygroscopicity was reduced by 42% to κ = 0.81 (+0.33, À0.40) (Figure 2, period Z1) in association with the initial addition of bacteria culture, ZoBell media, and unfiltered seawater (A1) at t = 0.6 days. The TOC concentration in the seawater after this initial addition averaged 89 μM, approximately 20 μM higher than the unaltered seawater control, which is slightly higher than typical springtime regional averages [Sohrin and Sempere, 2005], but is well below values observed at the ocean surface in regions of high biological activity [Engel et al, 2012]. This initial suppression of aerosol hygroscopicity is attributed primarily to the influence of just the ZoBell media on the OM aero content.…”

“…STXM-NEXAFS measurements of a collection of individual, internally mixed salt/organic particles also indicate an increase in the organic volume fraction of approximately 5% ( Figure S5). To date, this represents the largest observed change in CCN activity for ocean-relevant TOC (50-120 μM) [Sohrin and Sempere, 2005;Engel et al, 2012] and heterotrophic bacteria concentrations (approximately 5 × 10 5 -5 × 10 7 cells/mL) [Cho and Azam, 1990;Li, 1998]. Teeling et al [2012] recently observed heterotrophic bacteria concentrations of~3.6 × 10 6 cells mL À1 in the North Sea following periods of high photosynthetic biological activity (high chl a), which acted as the carbon source for the observed surge in bacterial growth in that locale.…”

Tracing the transport of colored dissolved organic matter in water masses of the Southern Beaufort Sea: relationship with hydrographic characteristics

“…Dissolved organic carbon (DOC) was measured using the high-temperature combustion method and either a TOC-V or TOC-5000 analyzer (Shimadzu) (Benner and Strom, 1993;Sohrin and Sempéré, 2005). Filtered water samples were stored frozen until analysis in laboratory.…”

The composition and flux of particulate and dissolved carbohydrates from the Rhone River into the Mediterranean Sea

“…Analytical errors based on duplicate analysis were approximately 5 %. DOC concentration was measured by high temperature combustion on a Shimadzu TOC 5000 analyzer, as described in Sohrin and Sempéré (2005). A four-point calibration curve was constructed daily with standards prepared by diluting a stock solution of potassium hydrogen phthalate in Milli-Q water.…”