TY - JOUR
T1 - Cross-basin differences in particulate organic carbon export and flux attenuation in the subtropical North Atlantic gyre
AU - Helmke, Peer
AU - Neuer, Susanne
AU - Lomas, Michael W.
AU - Conte, Maureen
AU - Freudenthal, Tim
N1 - Funding Information:
Funding for this comparison study was provided by NASA-EOS/03-0000-0514 to SN. We acknowledge funding support from the NSF for the BATS ( NSF OCE-0326885 and OCE-0752366 ) and OFP ( NSF OCE grants OCE-0325627 , OCE-0509602 and OCE-0623505 ) time series. We thank the German Ministry for Research and Education (BMBF) and the European Union (as part of EU-project CANIGO) for supporting the particle trap studies conducted at ESTOC. We thank all technicians and scientists involved in data collection at the time-series stations, and the officers and crew of the Weatherbird II, FS Poseidon and FS Meteor for their able assistance with shipboard operations. We are also grateful to Forrest Wong, ASU, for computational help.
PY - 2010/2
Y1 - 2010/2
N2 - We compared in-situ and satellite-derived measures of the biological carbon pump efficiency at the two seemingly similar subtropical North Atlantic gyre time series sites, the Bermuda time series (BATS, Bermuda Atlantic time-series study and OFP, ocean flux program) in the western gyre and the ESTOC time series (European station for time-series in the ocean, Canary Islands) in the eastern gyre. Satellite-derived surface chlorophyll a was slightly lower at Bermuda compared to ESTOC (annual average of 0.10±0.04 vs. 0.14±0.05-mg-m-3), as was satellite-derived primary production (annual average of 380±77 vs. 440±80-mg C-m-2 d-1). However, export production normalized to primary production (export ratio) was higher at Bermuda by a factor of 2-3 when estimated using mesopelagic traps moored at 500-m depth and by a factor of 3-4 when estimated using surface-tethered drifting traps. When averaged seasonally, flux at BATS was highest in spring (March, April, May) at all depths followed by summer (June, July, August) and decreasing towards fall, but this seasonality was less visible at ESTOC. Seasonal comparison showed the fastest flux attenuation at Bermuda in winter and spring, coinciding with the highest POC flux. POC/PIC ratios derived from the moored traps were significantly higher at BATS than at ESTOC in fall and winter, but this difference was not significant in spring (p>0.05). This study shows that while the western and eastern Atlantic subtropical gyres have similar rates of primary production, the biological carbon pump differs between the two provinces. Higher new nutrient input observed at Bermuda compared to ESTOC might explain part of the difference in export ratio but alone is insufficient. Greater winter mixed-layer depths and higher mesoscale eddy activity at Bermuda resulting in pulsed production events of labile organic matter might explain both the higher export flux and export ratios found at Bermuda.
AB - We compared in-situ and satellite-derived measures of the biological carbon pump efficiency at the two seemingly similar subtropical North Atlantic gyre time series sites, the Bermuda time series (BATS, Bermuda Atlantic time-series study and OFP, ocean flux program) in the western gyre and the ESTOC time series (European station for time-series in the ocean, Canary Islands) in the eastern gyre. Satellite-derived surface chlorophyll a was slightly lower at Bermuda compared to ESTOC (annual average of 0.10±0.04 vs. 0.14±0.05-mg-m-3), as was satellite-derived primary production (annual average of 380±77 vs. 440±80-mg C-m-2 d-1). However, export production normalized to primary production (export ratio) was higher at Bermuda by a factor of 2-3 when estimated using mesopelagic traps moored at 500-m depth and by a factor of 3-4 when estimated using surface-tethered drifting traps. When averaged seasonally, flux at BATS was highest in spring (March, April, May) at all depths followed by summer (June, July, August) and decreasing towards fall, but this seasonality was less visible at ESTOC. Seasonal comparison showed the fastest flux attenuation at Bermuda in winter and spring, coinciding with the highest POC flux. POC/PIC ratios derived from the moored traps were significantly higher at BATS than at ESTOC in fall and winter, but this difference was not significant in spring (p>0.05). This study shows that while the western and eastern Atlantic subtropical gyres have similar rates of primary production, the biological carbon pump differs between the two provinces. Higher new nutrient input observed at Bermuda compared to ESTOC might explain part of the difference in export ratio but alone is insufficient. Greater winter mixed-layer depths and higher mesoscale eddy activity at Bermuda resulting in pulsed production events of labile organic matter might explain both the higher export flux and export ratios found at Bermuda.
KW - Biological carbon pump
KW - Export production
KW - Flux attenuation
KW - Particle trap studies
KW - Primary production
KW - Subtropical North Atlantic Gyre
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U2 - 10.1016/j.dsr.2009.11.001
DO - 10.1016/j.dsr.2009.11.001
M3 - Article
AN - SCOPUS:74449084642
SN - 0967-0637
VL - 57
SP - 213
EP - 227
JO - Deep-Sea Research Part I: Oceanographic Research Papers
JF - Deep-Sea Research Part I: Oceanographic Research Papers
IS - 2
ER -