High-resolution spatial and temporal measurements of particulate organic carbon flux using thorium-234 in the northeast Pacific Ocean during the EXport Processes in the Ocean from RemoTe Sensing field campaign

被引:8
作者
Buesseler, Ken O. [1 ]
Benitez-Nelson, Claudia R. [2 ]
Roca-Marti, Montserrat [1 ]
Wyatt, Abigale M. [3 ]
Resplandy, Laure [3 ]
Clevenger, Samantha J. [1 ,4 ]
Drysdale, Jessica A. [1 ]
Estapa, Margaret L. [5 ,6 ]
Pike, Steven [1 ]
Umhau, Blaire P. [2 ]
机构
[1] Woods Hole Oceanog Inst, Dept Marine Chem & Geochem, Woods Hole, MA 02543 USA
[2] Univ South Carolina, Sch Earth Ocean & Environm, Columbia, SC 29208 USA
[3] Princeton Univ, Dept Geosci, Princeton, NJ 08544 USA
[4] MIT, Dept Earth Atmospher & Planetary Sci, Cambridge, MA USA
[5] Skidmore Coll, Geosci Dept, Saratoga Springs, NY 12866 USA
[6] Univ Maine, Darling Marine Ctr, Sch Marine Sci, Walpole, ME 04573 USA
来源
ELEMENTA-SCIENCE OF THE ANTHROPOCENE | 2020年 / 8卷 / 01期
基金
美国国家科学基金会; 美国国家航空航天局;
关键词
Thorium-234; Ocean Station Papa; Particulate organic carbon flux; EXPORTS; Biological carbon pump; SEDIMENT TRAPS; WATER COLUMN; TIME-SERIES; GLOBAL DATABASE; PARTICLE EXPORT; POC FLUX; ATLANTIC; SEA; EQUATORIAL; DYNAMICS;
D O I
10.1525/elementa.2020.030
中图分类号
X [环境科学、安全科学];
学科分类号
08 ; 0830 ;
摘要
The EXport Processes in the Ocean from RemoTe Sensing (EXPORTS) program of National Aeronautics and Space Administration focuses on linking remotely sensed properties from satellites to the mechanisms that control the transfer of carbon from surface waters to depth. Here, the naturally occurring radionuclide thorium-234 was used as a tracer of sinking particle flux. More than 950 234Th measurements were made during AugustSeptember 2018 at Ocean Station Papa in the northeast Pacific Ocean. High-resolution vertical sampling enabled observations of the spatial and temporal evolution of particle flux in Lagrangian fashion. Thorium234 profiles were remarkably consistent, with steady-state (SS) Th-234 fluxes reaching 1,450 + 300 dpm m(-2) d(-1) at 100 m. Nonetheless, Th-234 increased by 6%-10% in the upper 60 m during the cruise, leading to consideration of a non-steady-state (NSS) model and/or horizontal transport, with NSS having the largest impact by decreasing SS Th-234 fluxes by 30%. Below 100 m, NSS and SS models overlapped. Particulate organic carbon (POC)/Th-234 ratios decreased with depth in small (1-5 mm) and mid-sized (5-51 mm) particles, while large particle (>51 mm) ratios remained relatively constant, likely influenced by swimmer contamination. Using an average SS and NSS 234Th flux and the POC/Th-234 ratio of mid-sized particles, we determined a best estimate of POC flux. Maximum POC flux was 5.5+ 1.7 mmol C m(-2) d(-1) at 50 m, decreasing by 70% at the base of the primary production zone (117 m). These results support earlier studies that this site is characterized by a modest biological carbon pump, with an export efficiency of 13% + 5% (POC flux/net primary production at 120 m) and 39% flux attenuation in the subsequent 100 m (POC flux 220 m/POC flux 120m). This work sets the foundation for understanding controls on the biological carbon pump during this EXPORTS campaign.
引用
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页数:19
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