RV SONNE SO243 Cruise Report / Fahrtbericht Guayaquil, Ecuador: 05. October 2015 Antofagasta, Chile: 22. October 2015 SO243 ASTRA-OMZ: AIR SEA INTERACTION OF TRACE ELEMENTS IN OXYGEN MINIMUM ZONES.

Marandino, Christa A. (2016) RV SONNE SO243 Cruise Report / Fahrtbericht Guayaquil, Ecuador: 05. October 2015 Antofagasta, Chile: 22. October 2015 SO243 ASTRA-OMZ: AIR SEA INTERACTION OF TRACE ELEMENTS IN OXYGEN MINIMUM ZONES. Open Access . GEOMAR Helmholtz Centre for Ocean Research Kiel, 81 pp. DOI 10.3289/CR_SO243.

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Abstract

The ASTRA-OMZ SO243 cruise on board the R/V Sonne took place between the 5th and 22nd October 2015 from Guayaquil, Ecuador to Antofagasta, Chile. Scientists from Germany, the U.S.A, and Norway participated, spanning chemical, biological, and physical oceanography, as well as atmospheric science. The main goal of the cruise was to determine the impact of low oxygen conditions on trace element cycling and distributions, as well as to determine how air-sea exchange of trace elements is influenced by high productivity conditions. The subsequent impact of trace element ocean-atmosphere exchange on atmospheric chemistry and climate will be determined.
A summary of the main preliminary results is below:
- a strong source of nitrous oxide (N2O) and carbon dioxide (CO2) was detected from surface waters in the Peruvian upwelling, particularly in the near-coastal area between 9°S and 18°S
- generally, surface N2O during the SO-243 cruise was lower than previously observed, probably due to the reduced extent of upwelling events because of El Niño conditions
- less dimethyl sulphide (DMS) (< 2nmol L-1) and isoprene (at 20-30 pmol L-1) than on board previous cruises in the coastal upwelling region (8°-12°S) were detected, likely due to suppressed upwelling off of Peru because of the El Niño conditions
- a strong source for atmospheric carbonyl sulphide (OCS) was observed, as well as a strong correlation with oxygen. OCS decreased below the detection limit in oxygen depleted zones.
- a strong contrast between normal and El Niño conditions were detected for the halocarbon compounds. Both surface and deeper water was characterized by much larger concentrations of bromocarbons than of iodocarbons during ASTRA-OMZ, which stands in contrast to the previous M91 cruise during neutral conditions.
- it appears that the direct flux eddy covariance method was successful for sea-to-air flux measurements of N2O (for the first time)
- a pronounced atmospheric inversion layer at approximately 1 km altitude was striking, which was accompanied by an accumulation of high relative humidity and moderate to fresh southerly winds below this inversion. Convective activity was limited and very few precipitation events were detected. Tropospheric ozone levels reveal distinct fluctuations within 9.5°S and 16.5°S latitude.
- the oxygen distribution measured at about 9°S showed that the upwelling in October 2015 was very weak. Low oxygen water with less than 5 μmol kg-1 was located only below 250 m in October 2015
- higher oxygen distribution in 2015, as well as the changes in water temperature, salinity and density indicate the influence of El Niño. We have already published our first paper related to El Niño during SO243 (Stramma et al. 2016).

Document Type: Report (Cruise Report)
Keywords: FS SONNE; Cruise report; SO243; ASTRA-OMZ SO243 cruise
Research affiliation: OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-CH Chemical Oceanography
OceanRep > The Future Ocean - Cluster of Excellence
OceanRep > SFB 754
Open Access Journal?: Yes
DOI etc.: 10.3289/CR_SO243
Projects: Future Ocean, SFB754
Expeditions/Models/Experiments:
Date Deposited: 29 Aug 2016 10:42
Last Modified: 30 Aug 2016 07:13
URI: http://oceanrep.geomar.de/id/eprint/33652

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