Noble gases sampled from three cruises in the eastern tropical Atlantic in September 2005 and June/July 2006

DOI

Upwelling velocities w in the equatorial band are too small to be directly observed. Here, we apply a recently proposed indirect method, using the observed helium isotope (3He or 4He) disequilibria in the mixed layer. The helium data were sampled from three cruises in the eastern tropical Atlantic in September 2005 and June/July 2006. A one-dimensional two-box model was applied, where the helium air-sea gas exchange is balanced by upwelling from 3He-rich water below the mixed layer and by vertical mixing. The mixing coefficients Kv were estimated from microstructure measurements, and on two of the cruises, Kv exceeded 1 x 10-4 m2/s, making the vertical mixing term of the same order of magnitude as the gas exchange and the upwelling term. In total, helium disequilibrium was observed on 54 stations. Of the calculated upwelling velocities, 48% were smaller than 1.0 x 10-5 m/s, 19% were between 1.0 and 2.0 x 10-5 m/s, 22% were between 2.0 and 4.0 x 10-5 m/s, and on 11% of upwelling velocities exceeded this limit. The highest upwelling velocities were found in late June 2006. Meridional upwelling distribution indicated an equatorial asymmetry with higher vertical velocities between the equator and 1° to 2° south compared to north of the equator, particularly at 10°W. Associated heat flux into the mixed layer could be as high as 138 W/m2, but this depends strongly on the chosen depths where the upwelled water comes from. By combining upwelling velocities with sea surface temperature and productivity distributions, a mean monthly equatorial upwelling rate of 19 Sv was estimated for June 2006 and a biweekly mean of 24 Sv was estimated for September 2005.

Supplement to: Rhein, Monika; Dengler, Marcus; Sültenfuß, Jürgen; Hummels, Rebecca; Hüttl-Kabus, Sabine; Bourles, Bernard (2010): Upwelling and associated heat flux in the equatorial Atlantic inferred from helium isotope disequilibrium. Journal of Geophysical Research: Oceans, 115(C8), C08021

Identifier
DOI https://doi.org/10.1594/PANGAEA.808206
Related Identifier https://doi.org/10.1029/2009JC005772
Related Identifier https://doi.org/10.1594/PANGAEA.839752
Related Identifier https://doi.org/10.1594/PANGAEA.839750
Related Identifier https://doi.org/10.1594/PANGAEA.839749
Related Identifier https://doi.org/10.1594/PANGAEA.787643
Metadata Access https://ws.pangaea.de/oai/provider?verb=GetRecord&metadataPrefix=datacite4&identifier=oai:pangaea.de:doi:10.1594/PANGAEA.808206
Provenance
Creator Rhein, Monika ORCID logo; Dengler, Marcus ORCID logo; Sültenfuß, Jürgen ORCID logo; Hummels, Rebecca ORCID logo; Hüttl-Kabus, Sabine; Bourles, Bernard
Publisher PANGAEA
Publication Year 2010
Rights Creative Commons Attribution 3.0 Unported; https://creativecommons.org/licenses/by/3.0/
OpenAccess true
Representation
Language English
Resource Type Supplementary Publication Series of Datasets; Collection
Format application/zip
Size 3 datasets
Discipline Earth System Research
Spatial Coverage (-34.995W, -8.002S, 6.001E, 5.013N)
Temporal Coverage Begin 2005-09-10T11:31:00Z
Temporal Coverage End 2006-07-03T05:49:00Z