In:
Ocean Science, Copernicus GmbH, Vol. 12, No. 4 ( 2016-07-04), p. 861-873
Abstract:
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.
Type of Medium:
Online Resource
ISSN:
1812-0792
DOI:
10.5194/os-12-861-2016
DOI:
10.5194/os-12-861-2016-supplement
Language:
English
Publisher:
Copernicus GmbH
Publication Date:
2016
detail.hit.zdb_id:
2183769-7
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