Observed El Niño conditions in the eastern tropical Pacific in October 2015.

Stramma, Lothar , Fischer, Tim , Grundle, Damian, Krahmann, Gerd , Bange, Hermann W. and Marandino, Christa (2016) Observed El Niño conditions in the eastern tropical Pacific in October 2015. Open Access Ocean Science, 12 (4). pp. 861-873. DOI 10.5194/os-12-861-2016.

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Abstract

A strong El Niño developed in early 2015. Measurements from a research cruise on the R/V Sonne in October 2015 near the Equator east of the Galapagos Islands and off the shelf of Peru are used to investigate changes related to El Niño in the upper ocean in comparison with earlier cruises in this region. At the Equator at 85°30′ W, a clear temperature increase leading to lower densities in the upper 350 m had developed in October 2015, despite a concurrent salinity increase from 40 to 350 m. Lower nutrient concentrations were also present in the upper 200 m, and higher oxygen concentrations were observed between 40 and 130 m. In the equatorial current field, the Equatorial Undercurrent (EUC) east of the Galapagos Islands almost disappeared in October 2015, with a transport of only 0.02 Sv in the equatorial channel between 1° S and 1° N, and a weak current band of 0.78 Sv located between 1 and 2°30′ S. Such near-disappearances of the EUC in the eastern Pacific seem to occur only during strong El Niño events. Off the Peruvian shelf at  ∼  9° S, characteristics of upwelling were different as warm, saline, and oxygen-rich water was upwelled. At  ∼  12,  ∼  14, and  ∼  16° S, the upwelling of cold, low-salinity, and oxygen-poor water was still active at the easternmost stations of these three sections, while further west on these sections a transition to El Niño conditions appeared. Although from early 2015 the El Niño was strong, the October measurements in the eastern tropical Pacific only showed developing El Niño water mass distributions. In particular, the oxygen distribution indicated the ongoing transition from “typical” to El Niño conditions progressing southward along the Peruvian shelf.

Document Type: Article
Additional Information: WOS:000379422000001
Keywords: oxygen minimum zone, tropical Pacific, 2015 El Nino; R.V. METEOR; R.V. Sonne; M77/4, M90, M91, SO243.
Research affiliation: OceanRep > SFB 754 > B4
OceanRep > SFB 754
OceanRep > SFB 754 > A5
OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-CH Chemical Oceanography
OceanRep > GEOMAR > FB1 Ocean Circulation and Climate Dynamics > FB1-PO Physical Oceanography
Kiel University
Refereed: Yes
Open Access Journal?: Yes
DOI etc.: 10.5194/os-12-861-2016
ISSN: 1812-0784
Projects: SFB754, SOPRAN
Expeditions/Models/Experiments:
Date Deposited: 31 Mar 2016 13:18
Last Modified: 01 Feb 2019 15:06
URI: http://oceanrep.geomar.de/id/eprint/31930

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