Publication Date:
2024-07-01
Description:
A more than two-decadal sediment trap record from the Eastern Boundary Upwelling Ecosystem (EBUE) off Cape Blanc, Mauritania, is analysed with respect to deep ocean mass fluxes, flux components and their variability on seasonal to decadal timescales. The total mass flux revealed interannual fluctuations which were superimposed by fluctuations on decadal timescales. High winter fluxes of biogenic silica (BSi), used as a measure of marine production (mostly by diatoms) largely correspond to a positive North Atlantic Oscillation (NAO) index (December-March). However, this relationship is weak. The highest positive BSi anomaly was in winter 2004-2005 when the NAO was in a neutral state. More episodic BSi sedimentation events occurred in several summer seasons between 2001 and 2005, when the previous winter NAO was neutral or even negative. We suggest that distinct dust outbreaks and deposition in the surface ocean in winter and occasionally in summer/autumn enhanced particle sedimentation and carbon export on short timescales via the ballasting effect. Episodic perturbations of the marine carbon cycle by dust outbreaks (e.g. in 2005) might have weakened the relationships between fluxes and large-scale climatic oscillations. As phytoplankton biomass is high throughout the year, any dry (in winter) or wet (in summer) deposition of fine-grained dust particles is assumed to enhance the efficiency of the biological pump by incorporating dust into dense and fast settling organic-rich aggregates. A good correspondence between BSi and dust fluxes was observed for the dusty year 2005, following a period of rather dry conditions in the Sahara/Sahel region. Large changes of all bulk fluxes occurred during the strongest El Niño-Southern Oscillation (ENSO) in 1997-1999 where low fluxes were obtained for almost 1 year during the warm El Niño and high fluxes in the following cold La Niña phase. For decadal timescales, Bakun (1990) suggested an intensification of coastal upwelling due to increased winds (''Bakun upwelling intensification hypothesis''; Cropper et al., 2014) and global climate change. We did not observe an increase of any flux component off Cape Blanc during the past 2 and a half decades which might support this. Furthermore, fluxes of mineral dust did not show any positive or negative trends over time which might suggest enhanced desertification or ''Saharan greening'' during the last few decades.
Keywords:
Biogenic silica; Biogenic silica, flux, at time interval; Calcium carbonate, flux, at time interval; Calcium carbonate, flux of total flux; Cape Blanc; Carbon, organic, flux, at time interval; Carbon, organic, flux of total flux; CB1_trap; CB11; CB12; CB12_trap; CB13; CB13_trap; CB14; CB15; CB16; CB17; CB17_trap; CB18; CB18_trap; CB19; CB2_trap; CB20; CB21; CB22; CB3_trap; CB4_trap; CB5_trap; CB6; CB7; CB7_trap; CB8; CB9_trap; Center for Marine Environmental Sciences; Comment; Date; DATE/TIME; Date/time end; DEPTH, water; Duration, number of days; Event label; GeoB; Geosciences, University of Bremen; Lithogenic, flux, at time interval; Lithogenic, flux of total flux; M12/1; M16/2; M29/3; M6/6; M65/2; M9/4; Maria S. Merian; MARUM; Meteor (1986); MOOR; Mooring; MSM04/4b; Nitrogen, flux, at time interval; Nitrogen, flux of total flux; Northwest Africa; POS310; Poseidon; Sample code/label; Sample comment; Season; SFB261; South Atlantic in Late Quaternary: Reconstruction of Budget and Currents; Total mass, flux; Trap; TRAP
Type:
Dataset
Format:
text/tab-separated-values, 1402 data points
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