The tropical rainbelt and productivity changes off northwest Africa: A 31,000-year high-resolution record

Abstract. Nutrient rich water upwells offshore of Northwest Africa and is subsequently advected westwards. There it forms eddies and filaments with a rich spatial structure of physical and biological/biogeochemical properties. Here we present a high resolution (2.5 km) section through upwelling filaments and an eddy obtained in May 2018 with a Triaxus towed vehicle equipped with various oceanographic sensors. Physical processes at the mesoscale and submesoscale such as symmetric instability, trapping of fluid in eddies, and subduction of low potential vorticity (which we use as a water mass tracer) water can explain the observed distribution of biological production and export. We found a nitrate excess (higher nitrate concentrations than would be expected from oxygen values if only influenced by production and remineralization processes) core of an anti-cyclonic mode water eddy. We also found a high nitrate concentration region of ~5 km width in the mixed layer where symmetric instability appears to have injected nutrients from below into the euphotic zone. A similar region a little further south had high chlorophyll-a concentrations suggesting that nutrients had been injected there a few days earlier. Considering that such interactions of physics and biology are ubiquitous in the world's upwelling regions, we assume that they have strong influences on the productivity of such systems and their role in CO2 uptake. The intricate interplay of different parameters at kilometer scale needs to be taken into account when interpreting single profile and/or bottle data in dynamically active regions of the ocean.

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Rapid 20th-century increase in coastal upwelling off northwest Africa revealed by high-resolution marine sediment cores

PAGES news ◽

10.22498/pages.15.2.28 ◽

2007 ◽

Vol 15 (2) ◽

pp. 28-30

Author(s):

Helen McGregor ◽

Stefan Mulitza

Keyword(s):

High Resolution ◽

20Th Century ◽

Marine Sediment ◽

Coastal Upwelling ◽

Sediment Cores ◽

Northwest Africa

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High-resolution physical–biogeochemical structure of a filament and an eddy of upwelled water off northwest Africa

Ocean Science ◽

10.5194/os-16-253-2020 ◽

2020 ◽

Vol 16 (1) ◽

pp. 253-270 ◽

Cited By ~ 1

Author(s):

Wilken-Jon von Appen ◽

Volker H. Strass ◽

Astrid Bracher ◽

Hongyan Xi ◽

Cora Hörstmann ◽

...

Keyword(s):

High Resolution ◽

Active Regions ◽

Euphotic Zone ◽

Co2 Uptake ◽

Physical Processes ◽

Mode Water ◽

Northwest Africa ◽

Upwelled Water ◽

High Nitrate Concentration ◽

Symmetric Instability

Abstract. Nutrient-rich water upwells offshore of northwest Africa and is subsequently advected westwards. There it forms eddies and filaments with a rich spatial structure of physical and biological/biogeochemical properties. Here we present a high-resolution (2.5 km) section through upwelling filaments and an eddy obtained in May 2018 with a TRIAXUS towed vehicle equipped with various oceanographic sensors. Physical processes at the mesoscale and submesoscale such as symmetric instability, trapping of fluid in eddies, and subduction of low potential vorticity (which we use as a water mass tracer) water can explain the observed distribution of biological production and export. We found a nitrate excess (higher concentrations of nitrate than expected from oxygen values if only influenced by production and remineralization processes) core of an anticyclonic mode water eddy. We also found a high nitrate concentration region of ≈5 km width in the mixed layer where symmetric instability appears to have injected nutrients from below into the euphotic zone. Similarly, further south high chlorophyll-a concentrations suggest that nutrients had been injected there a few days earlier. Considering that such interactions of physics and biology are ubiquitous in the upwelling regions of the world, we assume that they strongly influence the productivity of such systems and their role in CO2 uptake. The intricate interplay of different parameters at the kilometer scale needs to be taken into account when interpreting single-profile and/or bottle data in dynamically active regions of the ocean.

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Observations of the spatial structure of interstellar hydrogen

Symposium - International Astronomical Union ◽

10.1017/s007418090010066x ◽

1967 ◽

Vol 31 ◽

pp. 45-46

Author(s):

Carl Heiles

Keyword(s):

High Resolution ◽

Spatial Structure ◽

Velocity Dispersion ◽

Temperature Variations

High-resolution 21-cm line observations in a region aroundlII= 120°,b11= +15°, have revealed four types of structure in the interstellar hydrogen: a smooth background, large sheets of density 2 atoms cm-3, clouds occurring mostly in groups, and ‘Cloudlets’ of a few solar masses and a few parsecs in size; the velocity dispersion in the Cloudlets is only 1 km/sec. Strong temperature variations in the gas are in evidence.

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