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Growing evidence suggests substantial quantities of particulate organic carbon (POC) produced in surface waters reach abyssal depths within days during episodic flux events. A 29-year record of in situ observations was used to examine episodic peaks in POC fluxes and sediment community oxygen consumption (SCOC) at Station M (NE Pacific, 4,000-m depth). From 1989 to 2017, 19% of POC flux at 3,400 m arrived during high-magnitude episodic events (≥mean + 2 σ), and 43% from 2011 to 2017. From 2011 to 2017, when high-resolution SCOC data were available, time lags between changes in satellite-estimated export flux (EF), POC flux, and SCOC on the sea floor varied between six flux events from 0 to 70 days, suggesting variable remineralization rates and/or particle sinking speeds. Half of POC flux pulse events correlated with prior increases in EF and/or subsequent SCOC increases. Peaks in EF overlying Station M frequently translated to changes in POC flux at abyssal depths. A power-law model (Martin curve) was used to estimate abyssal fluxes from EF and midwater temperature variation. While the background POC flux at 3,400-m depth was described well by the model, the episodic events were significantly underestimated by ∼80% and total flux by almost 50%. Quantifying episodic pulses of organic carbon into the deep sea is critical in modeling the depth and intensity of POC sequestration and understanding the global carbon cycle.
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Carbon export and fate beneath a dynamic upwelled filament off the California coast
Abstract. To understand the vertical variations in carbon fluxes inbiologically productive waters, four autonomous carbon flux explorers(CFEs), ship-lowered CTD-interfaced particle-sensitive transmissometer andscattering sensors, and surface-drogued sediment traps were deployed in afilament of offshore flowing, recently upwelled water, during the June 2017California Current Ecosystem – Long Term Ecological Research process study.The Lagrangian CFEs operating at depths from 100–500 m yielded carbon fluxand its partitioning with size from 30 µm–1 cm at three intensivestudy locations within the filament and in waters outside the filament. Sizeanalysis codes intended to enable long-term CFE operations independent ofships are described. Different particle classes (anchovy pellets, copepodpellets, and > 1000 µm aggregates) dominated the 100–150 mfluxes during successive stages of the filament evolution as it progressedoffshore. Fluxes were very high at all locations in the filament; below150 m, flux was invariant or increased with depth at the two locationscloser to the coast. Martin curve b factors (± denotes 95 %confidence intervals) for total particulate carbon flux were +0.37 ± 0.59, +0.85 ± 0.31, −0.24 ± 0.68, and −0.45 ± 0.70 at thethree successively occupied locations within the plume, and in transitionalwaters. Interestingly, the flux profiles for all particles< 400 µm were a much closer fit to the canonical Martinprofile (b−0.86); however, most (typically > 90 %) ofthe particle flux was carried by > 1000 µm sized aggregateswhich increased with depth. Mechanisms to explain the factor of 3 fluxincrease between 150 and 500 m at the mid-plume location are investigated.
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- Award ID(s):
- 1637632
- PAR ID:
- 10235751
- Date Published:
- Journal Name:
- Biogeosciences
- Volume:
- 18
- Issue:
- 10
- ISSN:
- 1726-4189
- Page Range / eLocation ID:
- 3053 to 3086
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.5194/bg-18-3053-2021
