TY - JOUR
T1 - Controls on carbon export in the subtropical North Atlantic
AU - Yumruktepe, Veli Çağlar
AU - Salihoğlu, Barış
AU - Neuer, Susanne
N1 - Funding Information:
This study was supported by the EU 7th Framework Programme EURO-BASIN (European Basin-scale Analysis, Synthesis and Integration) (project No: 246 933). This study was also supported by the DEKOSIM (Center for Marine Ecosystem and Climate Research) Project (BAP-08-11-DPT.2012K120880) funded by the Ministry of Development of Turkey . This study was also supported by TÜBITAK (Türkiye Bilimsel ve Teknolojik Arastirma Kurumu) (The Scientific and Technological Research Council of Turkey ) under the fellowship program towards scientific prior areas, 2211-C. We also acknowledge the use of The European Centre for Medium-Range Weather Forecasts’ (ECMWF) computing and archive facilities in this research.
Funding Information:
This study was supported by the EU 7th Framework Programme EURO-BASIN (European Basin-scale Analysis, Synthesis and Integration) (project No: 246 933). This study was also supported by the DEKOSIM (Center for Marine Ecosystem and Climate Research) Project (BAP-08-11-DPT.2012K120880) funded by the Ministry of Development of Turkey. This study was also supported by T?BITAK (T?rkiye Bilimsel ve Teknolojik Arastirma Kurumu) (The Scientific and Technological Research Council of Turkey) under the fellowship program towards scientific prior areas, 2211-C. We also acknowledge the use of The European Centre for Medium-Range Weather Forecasts? (ECMWF) computing and archive facilities in this research.
Publisher Copyright:
© 2020 Elsevier Ltd
PY - 2020/8/1
Y1 - 2020/8/1
N2 - We present a lower trophic level pelagic ecosystem model that allows the investigation of the role of hydrography, bacterial remineralization and detritus consumption on the strength of carbon export and its attenuation. We apply the model to investigate the controls on the carbon export at the Bermuda Atlantic Time-Series Study site (BATS) and the European Station for Time series in the Ocean, Canary Islands (ESTOC) in the subtropical North Atlantic. In previous field studies, export ratios at 200 m (the ratio between particulate carbon export below the euphotic zone and primary production) were found to be 300–400% smaller at ESTOC compared to BATS. Our model results show that the magnitude and temporal variability of primary productivity and modeled carbon export are modulated by the intensity and duration of vertical mixing events. BATS, with a more dynamic physical environment, has winter mixed-layer depths on average 80 m deeper than ESTOC and is characterized by pulses of enhanced productivity and export. Our model demonstrates the influence of hydrography on export attenuation through (i) more stable water column dynamics at ESTOC that increase particle remineralization time scales and weaken export strength at ESTOC compared to BATS; and (ii) higher water temperatures at BATS in the mesopelagic between 200 and 500 m that increase remineralization rates compared to ESTOC. This results in reduced differences in export ratios within the mesopelagic between both stations that is confirmed by observations. Strengthening remineralization through (i) adding zooplankton feeding on detritus and (ii) increasing bacterial remineralization rates decrease export at all depths at both stations, and increase the modeled difference in 200 m export ratios between BATS and ESTOC from 7% to 17%, a difference that is still much smaller than observed. While we could demonstrate the skill of our model in testing the mechanisms that could lead to differences in regional carbon export, our results indicate that hydrography-driven residence times, zooplankton feeding on detritus and enhanced bacterial remineralization rates alone are insufficient in driving export ratio differences between BATS and ESTOC. On the other hand, modeled export proved to be highly sensitive to prescribed particle sinking speeds. Thus, community and site dependent processes that lead to variations in particle sinking speed and remineralization, together with potential differences in vertical migration by zooplankton and horizontal transport, may be additional processes explaining the observed differences in export ratios at BATS and ESTOC.
AB - We present a lower trophic level pelagic ecosystem model that allows the investigation of the role of hydrography, bacterial remineralization and detritus consumption on the strength of carbon export and its attenuation. We apply the model to investigate the controls on the carbon export at the Bermuda Atlantic Time-Series Study site (BATS) and the European Station for Time series in the Ocean, Canary Islands (ESTOC) in the subtropical North Atlantic. In previous field studies, export ratios at 200 m (the ratio between particulate carbon export below the euphotic zone and primary production) were found to be 300–400% smaller at ESTOC compared to BATS. Our model results show that the magnitude and temporal variability of primary productivity and modeled carbon export are modulated by the intensity and duration of vertical mixing events. BATS, with a more dynamic physical environment, has winter mixed-layer depths on average 80 m deeper than ESTOC and is characterized by pulses of enhanced productivity and export. Our model demonstrates the influence of hydrography on export attenuation through (i) more stable water column dynamics at ESTOC that increase particle remineralization time scales and weaken export strength at ESTOC compared to BATS; and (ii) higher water temperatures at BATS in the mesopelagic between 200 and 500 m that increase remineralization rates compared to ESTOC. This results in reduced differences in export ratios within the mesopelagic between both stations that is confirmed by observations. Strengthening remineralization through (i) adding zooplankton feeding on detritus and (ii) increasing bacterial remineralization rates decrease export at all depths at both stations, and increase the modeled difference in 200 m export ratios between BATS and ESTOC from 7% to 17%, a difference that is still much smaller than observed. While we could demonstrate the skill of our model in testing the mechanisms that could lead to differences in regional carbon export, our results indicate that hydrography-driven residence times, zooplankton feeding on detritus and enhanced bacterial remineralization rates alone are insufficient in driving export ratio differences between BATS and ESTOC. On the other hand, modeled export proved to be highly sensitive to prescribed particle sinking speeds. Thus, community and site dependent processes that lead to variations in particle sinking speed and remineralization, together with potential differences in vertical migration by zooplankton and horizontal transport, may be additional processes explaining the observed differences in export ratios at BATS and ESTOC.
KW - BATS
KW - Bacterial remineralization
KW - Carbon export
KW - Detritus feeding
KW - ESTOC
KW - Model algorithms
KW - Subtropical gyre
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U2 - 10.1016/j.pocean.2020.102380
DO - 10.1016/j.pocean.2020.102380
M3 - Article
AN - SCOPUS:85088402042
SN - 0079-6611
VL - 187
JO - Progress in Oceanography
JF - Progress in Oceanography
M1 - 102380
ER -