scholarly journals Temperature effects on carbon-specific respiration rate and sinking velocity of diatom aggregates – potential implications for deep ocean export processes

2013 ◽  
Vol 10 (6) ◽  
pp. 4073-4085 ◽  
Author(s):  
M. H. Iversen ◽  
H. Ploug
Keyword(s):  
Respiration Rate ◽  
Deep Ocean ◽  
Sediment Traps ◽  
Average Particle ◽  
Data Set ◽  
Direct Measurements ◽  
Ocean Sediment ◽  
Influence Of Temperature On ◽  
Ocean Carbon ◽  
Sinking Velocity

Abstract. Most deep ocean carbon flux profiles show low and almost constant fluxes of particulate organic carbon (POC) in the deep ocean. However, the reason for the non-changing POC fluxes at depths is unknown. This study presents direct measurements of formation, degradation, and sinking velocity of diatom aggregates from laboratory studies performed at 15 °C and 4 °C during a three-week experiment. The average carbon-specific respiration rate during the experiment was 0.12 ± 0.03 at 15 °C, and decreased 3.5-fold when the temperature was lowered to 4 °C. No direct influence of temperature on aggregate sinking speed was observed. Using the remineralisation rate measured at 4 °C and an average particle sinking speed of 150 m d−1, calculated carbon fluxes were similar to those collected in deep ocean sediment traps from a global data set, indicating that temperature plays a major role for deep ocean fluxes of POC.

scholarly journals Temperature effects on carbon-specific respiration rate and sinking velocity of diatom aggregates – potential implications for deep ocean export processes

2013 ◽  
Vol 10 (1) ◽  
pp. 371-399 ◽  
Author(s):  
M. H. Iversen ◽  
H. Ploug
Keyword(s):  
Respiration Rate ◽  
Deep Ocean ◽  
Sediment Traps ◽  
Average Particle ◽  
Data Set ◽  
Direct Measurements ◽  
Ocean Sediment ◽  
Influence Of Temperature On ◽  
Ocean Carbon ◽  
Sinking Velocity

Abstract. Most deep ocean carbon flux profiles show low and almost constant fluxes of particulate organic carbon (POC) in the deep ocean. However, the reason for the seemingly non-changing POC fluxes at depths is unknown. This study presents direct measurements of formation, degradation, and sinking velocity of diatom aggregates from laboratory studies performed at 15 °C and 4 °C during a three week experiment. The average carbon-specific respiration rate during the experiment was 0.12 ± 0.03 at 15 °C, and decreased 3.5-fold when the temperature was lowered to 4 °C. No direct influence of temperature on aggregate sinking speed was observed. Using the remineralisation rate measured at 4 °C and an average particle sinking speed of 150 m d−1, calculated carbon fluxes were similar to those collected in deep ocean sediment traps from a global data set, indicating that temperature plays a major role for deep ocean fluxes of POC.

scholarly journals Ballast minerals and the sinking carbon flux in the ocean: carbon-specific respiration rates and sinking velocity of marine snow aggregates

2010 ◽  
Vol 7 (9) ◽  
pp. 2613-2624 ◽  
Author(s):  
M. H. Iversen ◽  
H. Ploug
Keyword(s):  
Respiration Rate ◽  
Skeletonema Costatum ◽  
Aggregate Size ◽  
Respiration Rates ◽  
Marine Aggregates ◽  
Organic Carbon Fluxes ◽  
Ocean Carbon ◽  
Sinking Velocities ◽  
Sinking Velocity ◽  
Combined Data

Abstract. Recent observations have shown that fluxes of ballast minerals (calcium carbonate, opal, and lithogenic material) and organic carbon fluxes are closely correlated in the bathypelagic zones of the ocean. Hence it has been hypothesized that incorporation of biogenic minerals within marine aggregates could either protect the organic matter from decomposition and/or increase the sinking velocity via ballasting of the aggregates. Here we present the first combined data on size, sinking velocity, carbon-specific respiration rate, and composition measured directly in three aggregate types; Emiliania huxleyi aggregates (carbonate ballasted), Skeletonema costatum aggregates (opal ballasted), and aggregates made from a mix of both E. huxleyi and S. costatum (carbonate and opal ballasted). Overall average carbon-specific respiration rate was ~0.13 d−1 and did not vary with aggregate type and size. Ballasting from carbonate resulted in 2- to 2.5-fold higher sinking velocities than those of aggregates ballasted by opal. We compiled literature data on carbon-specific respiration rate and sinking velocity measured in aggregates of different composition and sources. Compiled carbon-specific respiration rates (including this study) vary between 0.08 d−1 and 0.20 d−1. Sinking velocity increases with increasing aggregate size within homogeneous sources of aggregates. When compared across different particle and aggregate sources, however, sinking velocity appeared to be independent of particle or aggregate size. The carbon-specific respiration rate per meter settled varied between 0.0002 m−1 and 0.0030 m−1, and decreased with increasing aggregate size. It was lower for calcite ballasted aggregates as compared to that of similar sized opal ballasted aggregates.

scholarly journals Evaluation of NorESM-OC (versions 1 and 1.2), the ocean carbon-cycle stand-alone configuration of the Norwegian Earth System Model (NorESM1)

2016 ◽  
Author(s):  
J. Schwinger ◽  
N. Goris ◽  
J. Tjiputra ◽  
I. Kriest ◽  
M. Bentsen ◽  
...  
Keyword(s):  
Carbon Cycle ◽  
Deep Ocean ◽  
Earth System Model ◽  
System Model ◽  
Earth System ◽  
Atmospheric Forcing ◽  
Ocean Carbon Cycle ◽  
Data Set ◽  
Model Version ◽  
Ocean Carbon

Abstract. Idealised and hindcast simulations performed with the stand-alone ocean carbon-cycle configuration of the Norwegian Earth System Model (NorESM-OC) are described and evaluated. We present simulation results of two different model versions at different grid resolutions and using two different atmospheric forcing data sets. Model version NorESM-OC1 corresponds to the version that is included in the fully coupled model NorESM-ME1, which participated in CMIP5. The main update between NorESM-OC1 and NorESM-OC1.2 is the addition of two new options for the treatment of sinking particles. We find that using a constant sinking speed, which has been the standard in NorESM's ocean carbon cycle module HAMOCC (HAMburg Ocean Carbon Cycle model) does not transport enough particulate organic carbon (POC) into the deep ocean below approximately 2000 m depth. The two newly implemented parameterisations, a particle aggregation scheme with prognostic sinking speed, and a simpler scheme prescribing a linear increase of sinking speed with depth, provide better agreement with observed POC fluxes. Additionally, reduced deep ocean biases of oxygen and remineralised phosphate indicate a better performance of the new parameterisations. For model version 1.2, a re-tuning of the ecosystem parameterisation has been performed, which (i) reduces previously too high primary production in high latitudes, (ii) consequently improves model results for surface nutrients, and (iii) reduces alkalinity and dissolved inorganic carbon biases at low latitudes. We use hindcast simulations with prescribed observed and constant (pre-industrial) atmospheric CO2 concentrations to derive the past and contemporary ocean carbon sink. For the period 1990–1999 we find an average ocean carbon uptake ranging from 2.01 to 2.58 Pg C yr-1 depending on model version, grid resolution and atmospheric forcing data set.

scholarly journals Ballast minerals and the sinking carbon flux in the ocean: carbon-specific respiration rates and sinking velocities of macroscopic organic aggregates (marine snow)

2010 ◽  
Vol 7 (3) ◽  
pp. 3335-3364 ◽  
Author(s):  
M. H. Iversen ◽  
H. Ploug
Keyword(s):  
Respiration Rate ◽  
Skeletonema Costatum ◽  
Aggregate Size ◽  
Respiration Rates ◽  
Carbon Remineralization ◽  
Marine Aggregates ◽  
Organic Carbon Fluxes ◽  
Ocean Carbon ◽  
Sinking Velocities ◽  
Sinking Velocity

Abstract. Recent observations have shown that fluxes of ballast minerals (calcium carbonate, opal, and lithogenic material) and organic carbon fluxes are closely correlated in the bathypelagic zones of the ocean. Hence it has been hypothesized that incorporation of biogenic minerals within marine aggregates could either protect the organic matter from decomposition and/or increase the sinking velocity via ballasting of the aggregates. Here we present the first combined data on size, sinking velocity, carbon-specific respiration rate, and composition measured directly in three aggregate types; Emiliania huxleyi aggregates (carbonate ballasted), Skeletonema costatum aggregates (opal ballasted), and aggregates made from a mix of both E. huxleyi and S. costatum (carbonate and opal ballasted). Overall average carbon-specific respiration rate was ~0.13 d−1 and did not vary with aggregate type and size. Ballasting from carbonate resulted in 2- to 2.5-fold higher sinking velocities than aggregates ballasted by opal. We compiled literature data on carbon-specific respiration rate and sinking velocity measured in aggregate of different composition and sources. Compiled carbon-specific respiration rates (including this study) vary between 0.08 d−1 and 0.20 d−1. Sinking velocity increases with increasing aggregate size within homogeneous sources of aggregates. When compared across different particle and aggregate sources, however, sinking velocity appeared to be independent of particle or aggregate size. The calculated carbon remineralization length scale due to microbial respiration and sinking velocity of mm-large marine aggregates was higher for calcite ballasted aggregates as compared to opal-ballasted aggregates. It varied between 0.0002 m−1 and 0.0030 m−1, and decreased with increasing aggregate size.

scholarly journals Evaluation of NorESM-OC (versions 1 and 1.2), the ocean carbon-cycle stand-alone configuration of the Norwegian Earth System Model (NorESM1)

2016 ◽  
Vol 9 (8) ◽  
pp. 2589-2622 ◽  
Author(s):  
Jörg Schwinger ◽  
Nadine Goris ◽  
Jerry F. Tjiputra ◽  
Iris Kriest ◽  
Mats Bentsen ◽  
...  
Keyword(s):  
Carbon Cycle ◽  
Deep Ocean ◽  
Earth System Model ◽  
System Model ◽  
Earth System ◽  
Atmospheric Forcing ◽  
Ocean Carbon Cycle ◽  
Data Set ◽  
Model Version ◽  
Ocean Carbon

Abstract. Idealised and hindcast simulations performed with the stand-alone ocean carbon-cycle configuration of the Norwegian Earth System Model (NorESM-OC) are described and evaluated. We present simulation results of three different model configurations (two different model versions at different grid resolutions) using two different atmospheric forcing data sets. Model version NorESM-OC1 corresponds to the version that is included in the NorESM-ME1 fully coupled model, which participated in CMIP5. The main update between NorESM-OC1 and NorESM-OC1.2 is the addition of two new options for the treatment of sinking particles. We find that using a constant sinking speed, which has been the standard in NorESM's ocean carbon cycle module HAMOCC (HAMburg Ocean Carbon Cycle model), does not transport enough particulate organic carbon (POC) into the deep ocean below approximately 2000 m depth. The two newly implemented parameterisations, a particle aggregation scheme with prognostic sinking speed, and a simpler scheme that uses a linear increase in the sinking speed with depth, provide better agreement with observed POC fluxes. Additionally, reduced deep ocean biases of oxygen and remineralised phosphate indicate a better performance of the new parameterisations. For model version 1.2, a re-tuning of the ecosystem parameterisation has been performed, which (i) reduces previously too high primary production at high latitudes, (ii) consequently improves model results for surface nutrients, and (iii) reduces alkalinity and dissolved inorganic carbon biases at low latitudes. We use hindcast simulations with prescribed observed and constant (pre-industrial) atmospheric CO2 concentrations to derive the past and contemporary ocean carbon sink. For the period 1990–1999 we find an average ocean carbon uptake ranging from 2.01 to 2.58 Pg C yr−1 depending on model version, grid resolution, and atmospheric forcing data set.

scholarly journals Peak glacial <sup>14</sup>C ventilation ages suggest major draw-down of carbon into the abyssal ocean

2013 ◽  
Vol 9 (6) ◽  
pp. 2595-2614 ◽  
Author(s):  
M. Sarnthein ◽  
B. Schneider ◽  
P. M. Grootes
Keyword(s):  
Dissolved Inorganic Carbon ◽  
Ice Core ◽  
Deep Ocean ◽  
Atmospheric Co2 ◽  
Age Difference ◽  
Data Set ◽  
Atlantic Sector ◽  
Deep Waters ◽  
14C Age ◽  
Ocean Carbon

Abstract. Ice core records demonstrate a glacial–interglacial atmospheric CO2 increase of ~ 100 ppm, while 14C calibration efforts document a strong decrease in atmospheric 14C concentration during this period. A calculated transfer of ~ 530 Gt of 14C-depleted carbon is required to produce the deglacial coeval rise of carbon in the atmosphere and terrestrial biosphere. This amount is usually ascribed to oceanic carbon release, although the actual mechanisms remained elusive, since an adequately old and carbon-enriched deep-ocean reservoir seemed unlikely. Here we present a new, though still fragmentary, ocean-wide Δ14C data set showing that during the Last Glacial Maximum (LGM) and Heinrich Stadial 1 (HS-1) the maximum 14C age difference between ocean deep waters and the atmosphere exceeded the modern values by up to 1500 14C yr, in the extreme reaching 5100 14C yr. Below 2000 m depth the 14C ventilation age of modern ocean waters is directly linked to the concentration of dissolved inorganic carbon (DIC). We propose as a working hypothesis that the modern regression of DIC vs. Δ14C also applies for LGM times, which implies that a mean LGM aging of ~ 600 14C yr corresponded to a global rise of ~ 85–115 μmol DIC kg−1 in the deep ocean. Thus, the prolonged residence time of ocean deep waters may indeed have made it possible to absorb an additional ~ 730–980 Gt DIC, one third of which possibly originated from intermediate waters. We also infer that LGM deep-water O2 dropped to suboxic values of < 10 μmol kg−1 in the Atlantic sector of the Southern Ocean, possibly also in the subpolar North Pacific. The deglacial transfer of the extra-aged, deep-ocean carbon to the atmosphere via the dynamic ocean–atmosphere carbon exchange would be sufficient to account for two trends observed, (1) for the increase in atmospheric CO2 and (2) for the 190‰ drop in atmospheric Δ14C during the so-called HS-1 "Mystery Interval", when atmospheric 14C production rates were largely constant.

scholarly journals Global ocean particulate organic carbon flux merged with satellite parameters

2016 ◽  
Vol 8 (2) ◽  
pp. 531-541 ◽  
Author(s):  
Colleen B. Mouw ◽  
Audrey Barnett ◽  
Galen A. McKinley ◽  
Lucas Gloege ◽  
Darren Pilcher
Keyword(s):  
Time Series ◽  
Organic Carbon ◽  
Particulate Organic Carbon ◽  
Net Primary Production ◽  
Mixed Layer Depth ◽  
Deep Ocean ◽  
Euphotic Zone ◽  
Sediment Traps ◽  
Global Ocean ◽  
Data Set

Abstract. Particulate organic carbon (POC) flux estimated from POC concentration observations from sediment traps and 234Th are compiled across the global ocean. The compilation includes six time series locations: CARIACO, K2, OSP, BATS, OFP, and HOT. Efficiency of the biological pump of carbon to the deep ocean depends largely on biologically mediated export of carbon from the surface ocean and its remineralization with depth; thus biologically related parameters able to be estimated from satellite observations were merged at the POC observation sites. Satellite parameters include net primary production, percent microplankton, sea surface temperature, photosynthetically active radiation, diffuse attenuation coefficient at 490 nm, euphotic zone depth, and climatological mixed layer depth. Of the observations across the globe, 85 % are concentrated in the Northern Hemisphere with 44 % of the data record overlapping the satellite record. Time series sites accounted for 36 % of the data, while 71 % of the data are measured at  ≥  500 m with the most common deployment depths between 1000 and 1500 m. This data set is valuable for investigations of CO2 drawdown, carbon export, remineralization, and sequestration. The compiled data can be freely accessed at doi:10.1594/PANGAEA.855600.

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